ON COMMERCIAL AVIATION SAFETY - UKFSC 74.pdf · Front Cover Picture: Malaysia Airlines B747-400...

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ISSUE 74

The official publication of the United Kingdom Flight Safety Committee ISSN 1355-1523

O N C O M M E R C I A L AV I AT I O N S A F E T Y

37187®Flight Safety iss 74 25/3/09 12:19

Safer


ContentsThe Official Publication of THE UNITED KINGDOM FLIGHT SAFETY COMMITTEE ISSN: 1355-1523 SPRING 2009

Editorial 2

Chairman’s Column 3

Don’t eat into your margins –

How to cope with wet runways and hydroplanning 4

A article from JETSETS – the flight safety newsletter for BAE

Airline Fatigue Risk Management: purpose and benefits 7

by Simon Stewart and Derek Brown, easyjet

Battling Level Busts 10

by Peter Riley, NATS

The SKYbrary Project 14

by Tzvetomir Blajev and John Barrass of Eurocontrol

Safer Skies 17

by Hazel Courtney, CAA Research

Avoiding the Conflict 21

by Anne Isaac and Vicky Brooks of NATS

Wake Turbulence – Progress at Last 23

by David Booth, Eurocontrol

Front Cover Picture: Malaysia Airlines B747-400

FOCUS is a quarterly subscription journal devoted

to the promotion of best practises in aviation

safety. It includes articles, either original or

reprinted from other sources, related to safety

issues throughout all areas of air transport

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and improve networking within the industry. It

must be emphasised that FOCUS is not intended

as a substitute for regulatory information or

company publications and procedures.

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1focus spring 09


What should Accountable Managers knowabout Aviation Safety?

EDITORIAL

Along with others, I was recently invited

by the CAA to address a gathering of

Airline Executives and Accountable Managers.

The aim of the conference was to spend time

reviewing the state of aviation safety in the

UK and to highlight developments in

regulation in Europe.As I approach the end of

my first year at the UKFSC, preparation for

the conference provided a welcome

opportunity to take stock and generate an

independent view of the industry.

I have learned a lot about commercial airtransport, and much of it is very positive. For astart, the industry is incredibly dynamic,operationally focused and extremely flexible. Itis also very responsive to change and adaptableto technology.

But what has the past year taught me as far ascommercial aviation safety is concerned? Itmay be useful at this point to rehearse thesources of information from which I have beenable to elicit my views. Our bi-monthly SafetyInformation Exchange Meetings are importantthermometers with which to test the water.Sixty or seventy aviation safety professionals,both for the UK and overseas and from mostsectors involved in the industry, regularly sharethe details of their companies’ incidents andaccidents in a confidential forum.

In addition, I represent the UKFSC at over 20national and international safety meetings,through which the Membership are keptinformed on safety issues and activities in mostsectors across the industry. Briefings andsummaries on the outcomes from each ofthese meetings are routinely posted on theUKFSC website.Through my regular attendanceat these meetings, I have come to realise thatthere is a great deal of excellent and earnestaviation safety work going on – but that thereis much duplication of effort and of resourcesbeing wasted. There would be much to begained from better co-ordination andpartnership in all safety initiatives byidentifying regional centres of excellence, whichcould take the lead on co-ordinating anddistributing safety knowledge and informationand directing a more coherent approach; this isthe major reason for the UKFSC becoming apartner in the SKYbrary aviation safety website.

Turning now to the accident statistics for thepast year, the news, on the face of it, is good.The safety record of UK carriers stands up well

in comparison to the worldwide situation,where the number of fatalities attributed tocommercial aircraft accidents is down,although the number of accidents involvingfatalities is up. But with no fatal accidentsinvolving large public transport aircraft in theUK since 2001, our safety record looksimpressive – but this could have been sodifferent. Had the skill and luck of the BritishAirways 777 crew been any less on 17 Januarylast year, or had the aircraft’s approach profilebeen less forgiving, we could have beendiscussing a whole new safety situation!

But of equal concern, had the final outcomesfrom several incidents debated during ourpast year’s Safety Information ExchangesMeetings been just a little less fortunate, wecould have been dealing with a much morecritical and catastrophic period for UK andEuropean aviation. To my knowledge, anincorrect configuration event - not toodissimilar to the recent Spanair disaster - andseveral loading and performance calculationerrors have put at least four airlines withinseconds of serious accidents in the past year!

So, the apparently strong safety record that UKairlines continue to enjoy should not provideany excuse for self congratulation orcomplacency. Nevertheless, we should beextremely grateful that there is enough of apositive safety culture and willingness amongstour airline community to share the facts andcircumstances surrounding these incidents, andthereby give others the invaluable opportunityto learn from these mistakes, rather thanrepeating them in ignorance!

Having aired some of my concerns about UKaviation safety gleaned from the past year atthe UKFSC at the conference, I grasped theopportunity to highlight some of the newresponsibilities which the regulatoryintroduction of SMS now lays at the door ofAirline Directors and Accountable Managers.In the highly political, litigious and media-richworld in which today’s airlines must operate,where the latest corporate manslaughterlegislation awaits its day in court and wherethe buck can no longer be passed into the solecharge of safety and quality people, what is itthat an Airline Board Director and theAccountable Manager need to know aboutthe safety and risk management of theirbusiness. I suggest the following questionsshould be foremost in their mind:

■ What could go wrong?

■ What will stop it happening in theirorganisation – either today or tomorrow?

■ What other things should and could be done?

■ Is the company striving for continuousimprovement ?

In response, the following strategy is offeredfor consideration:

Own and promote your company’s safety policyand get it understood throughout the company.

Make sure your company’s safety organisationis well trained, respected and influential atBoard level and right across the company.

Develop a just safety culture which permeatesthe entire organisation.

Build a Safety Management System whichencourages non-punitive reporting of allevents and incidents - from which lessons canbe learnt, hazards identified and risksmanaged effectively.

Integrate Safety Management into yourbusiness plan and give it the same attentionas all other business risks.

Establish safety assurance arrangementswhich ensure that Flight Ops, Training,Engineering and Support Servicescommunicate and co-ordinate with theSafety Department effectively.

Not learning the lessons can be hard and veryexpensive – if not business threatening!

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by Rich Jones


CHAIRMAN’S COLUMN

Sharing Data, Keeping Saferby Steve Hull, Baines Simmons

Often safety within aviation can come

back and haunt you particularly after

an accident. This normally results in you

saying under your breath, or you hear

others saying either “I knew that would

happen” or “it was just a matter of time.”

Why? Well as I write this column the US

Airways A340 that crash landed on the

Hudson River is still major news and quite

rightly so. It would be inappropriate of me

to pre-empt the investigation, albeit to say

that both the flight and cabin crew appear

to have done a fantastic job.

Let me explain. During my airline career I wascalled “the Birdman of BA” and have spent thelast 15 years trying to highlight the hazardthat exists within the industry. So I believed inthe inevitability of losing a passenger aircraftto a serious bird strike.

My bird strike involvement started after Inoticed BA was experiencing a high numberof bird strike events when operating in andout of Entebbe, Uganda. BA operated threetimes a week using a DC-10 aircraft and weresuffering a bird strike every other arrival ordeparture. As a result I did what every safetymanager should do and highlighted what Iperceived to be a hazard. It then took methree months and several heated exchangesto get the hazard raised to a senior level. Thisincluded a visit to the airfield and meetingswith the Airfield Operator and also theUgandan Government. As a result of thisminor victory, I began a crusade against ourfeathered friends and those that have heardme speak at bird strike conferences will knowthe passion I have on the subject.

So why do I believe for instance “it was just a

matter of time?”

Let me further explain. Most airlines gathersafety data through air safety reports or asimilar medium and included in that data isbird strikes and near strikes. Airfield operatorsalso collect information on bird strikes thatoccur at their airport. We all know theimportance of safety data sharing, well we dowithin the UKFSC, but that cannot be saidabout our colleagues.

If safety data sharing is effective, then anyserious aircraft incident or accident is atragedy that should be shared by all, as theinformation that could have prevented theevent would have been known to someone.This can be testified as immediately after theLa Guardia event, I was reliably informed byone major airline, that La Guardia was theNo.2 airport on their bird strike hazard list.Don’t tell me, tell La Guardia, let your ownairline know and then all airlines that operateinto that airport.

So the sharing of data is still in its infancy andas we know three major US airlines havestopped their Aviation Safety Action Plan(ASAP) programmes altogether. This results inan increase in the risk of airlines experiencingevents that may have occurred before. Howcan this be allowed to happen? The sharing ofsafety data is the only tool that caneffectively prevent a repetition of an event,for airlines and airport authorities not to sharethis information is nothing short of criminal.As Bill Voss – CEO FSF, quite rightly stated‘safety should not be used as a bargainingtool,’ I would go further and state that ‘safetyis not a commodity that should be used forcommercial advantage.’

Those airlines that have scrapped theirreporting programme must sit down withtheir pilots, engineers and ground workers andneed to get together and thrash out an MOU(Memorandum of Understanding) with regardto the reporting of safety incidents. Mostother international airlines have achieved this,so we are not talking about the impossible.

So where are we, well the world now knowsthat birds are a hazard to aviation and stepsmust be taken to reduce that hazard to anacceptable level, but once again it takes a hullloss to hammer that point home. AirportOperators must be responsible andaccountable for what occurs on and aroundtheir airfield, airlines must ensure that theairports they operate to, maintain the highestbird strike awareness and avoidanceprogramme. If they do not, then they musttake steps to ensure they do, as it is theAirport Operators responsibility to ensurethat their airfield is safe for aircraft to land atand take off from. There is no doubt thatNew York and New Jersey Port Authority arelooking at their present procedures closely.They should do and they should hope they dideverything possible to prevent the accident,as once the legal eagles get hold of it, theywill have wished they had.

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UK FLIGHT SAFETY COMMITTEE OBJECTIVES

■ To pursue the highest standards of aviation safety.

■ To constitute a body of experienced aviation flight safety personnel available for consultation.

■ To facilitate the free exchange of aviation safety data.

■ To maintain an appropriate liaison with other bodies concerned with aviation safety.

■ To provide assistance to operators establishing and maintaining a flight safety organisation.


In 2005 an Embraer 145 overshot runway

27L at Hanover Airport. According to the

German Federal Bureau of Aircraft

Accident Investigation Report EX006-0/05

which can be read in full on their web site

(http://www.bfuweb.de):

The weather forecast indicatedthunderstorms and heavy showers of rain.Theinitial ATIS indicated a wind of 150/5 kt and avisibility of 8 km in light rain.

The weather deteriorated during theapproach, and at the time of landing the windwas 100/5 kt (a 3 kt tailwind) with a visibilityof 2000 m in heavy rain. The runway was wetand showed patches of standing water.Approximately 15 minutes after theoccurrence the braking coefficients for thefirst third of the runway were between 0.4and 0.7 and for the remainder of the runwaywere between 0.6 and 0.7 (good); however, ithad stopped raining by this time, and so thesecoefficients were not considered by theInvestigation to be relevant to the accident.

A Boeing 737 that landed prior to theEmbraer subsequently reported to theInvestigation that the braking action wasmedium – but this was not reported at thetime to ATC. According to crew statementsthe aircraft crossed the threshold at 140 kt(Vref 131 kt) and touched down in thetouchdown zone.The FDR showed a thresholdcrossing height of 62 feet as as opposed tothe correct 50 feet. The crew did notexperience any significant deceleration of theaircraft even though the ground spoilers hadautomatically deployed after touchdown.

Both pilots attempted to brake, and shortlybefore the aircraft overshot the runway thepilot in command activated the parking brakewhich is also the emergency brake. Thisresulted in deactivation of the anti-skidsystem, the wheels locked up and the groundspoilers retracted (because the wheels hadlocked). The aircraft came to a rest about160m beyond the end of the runway, andsuffered only minor damage.

Eyewitnesses stated that the aircraft toucheddown about 1000 m after the threshold, andthis was later refined from FDR data to 849m.

All four tyres showed traces of rubberreversion hydroplaning (Figure 1), and had leftabout 400m long bright traces on the runwaywhich were definitely caused by rubberreversion hydroplaning (runway marks leftfollowing rubber reversion hydroplaning looklike they might originate from steam blasting(Figure 2)).

Furthermore, melted away rubber was foundon the runway (Figure 3).

The Investigation concluded that based onthe slow deceleration after touchdown it washighly likely that dynamic aquaplaningoccurred in the middle portion of the runwayfollowed by rubber reversion hydroplaningwhich occurred when the emergency brakewas activated, the anti-skid deactivated andthe tyres locked.

The aircraft technical log did not show anyirregularities regarding the brakes or tyres, andthe tyres were inflated correctly.

The worst case RLW calculation, which theInvestigation thought most likely to apply tothis landing, gave a stopping distance with150m runway remaining – there was a longerrunway available but the crew chose 27Lbecause of construction work on a taxiwayand the shorter distance to the terminal.

Lessons that can be learnt

I would like to use this incident to illustrate 2lessons: firstly the factors leading to anoverrun, and secondly to discusshydroplaning.

Lesson 1 – The overrun

The last issue of JETSETS also coveredoverruns and we found that all overruns hadmore than one contributory factor. From myreading of the report this overrun is nodifferent in that there were several factors aslisted below:

1. Landed slightly long. The idealtouchdown point is 300 m from thethreshold - in this instance thetouchdown was at 849 m. This shortenedthe LDA.

4 focus spring 09

Don’t eat into your margins – How to copewith wet runways and hydroplaningAn article from JETSETS – the flight safety news for BAE Systems Regional Aircraft customers

Above: wet runways can affect braking

Left: Figure 1 – marks of rubber reversion

hydroplaning on the tyre.


2. Landed slightly fast - but only by a fewknots.

3. Runway condition. The runway was wet,or even flooded, but it is not clear whetherthe crew were aware of this. The crewwere notinformed of the runwaycondition by ATC.

4. Wind. There was a slight tailwind.

5. Incorrect braking technique. The AircraftOperation Manual Part B included: Whenhydroplaning occurs, it causes asubstantial loss of tire friction and wheelspin-up may not occur.

■ The approach must be flown with thetarget of minimising the landingdistance.

■ The approach must be stabilized, andlanding on centre line in thetouchdown zone.

■ The touchdown should be firm topenetrate the contaminating fluidfilm, and ensure wheel spin-up andspoiler activation.

■ Immediately after touchdown, checkthe ground spoiler automaticdeployment when thrust levers arereduced to IDLE.

■ Lower the nose wheel positively, withforward pressure to assist traction anddirectional stability.

■ Apply brakes with moderate-to-

firm pressure, smoothly and

symmetrically, and let the anti-skid

do its job.

■ If no braking action is felt,

hydroplaning is probably occurring.

Do not apply Emergency/Parking

brake, as it will cause the spoilers to

close and cut the anti-skid

protection. Maintain runway centre

line and keep braking until airplane

is decelerated.

The crew do not appear to have followedsome of the above advice. BAE Systems havereceived reports of incidents occuring to BAe146/ Avro RJ aircraft where the anti-skidsystem was not given a chance to adapt to theconditions because yellow, green and thenemergency yellow were selected in quicksuccession. This does not allow the adaptivefeature of the anti-skid to operate correctly.You should note from the above that lockedwheels provide very little stopping assistance!

As can be seen, there were at least fivecontributing factors.This incident may have beeninevitable because the LDR following the longtouchdown might have been insufficient, but ifthe other factors had not been present it ispossible that an overrun would not haveoccurred. As stated at the end of the JETSETSarticle in the previous issue dated February 2008:

Don’t eat into your margins, and if in doubt

go around.

Lesson 2 – Hydroplaning

The other lesson from this accident has to dowith hydroplaning. Control of your aircraft onthe ground depends on the contact betweenthe tyres and the surface, and on the frictionprovided by that surface. Whilst the aboveaccident highlighted the braking problemscaused by hydroplaning, directional control canbe equally affected, especially in strongcrosswinds before the rudder becomes fullyeffective. As a tyre rolls along the runway it isconstantly squeezing water from the tread.Thissqueezing action generates pressure within thewater that can lift part of the tyre off therunway and reduce the amount of friction thatthe tyre can develop. This squeezing action iscalled hydroplaning. Please note that icyrunways are a totally separate issue.

Three basic modes of hydroplaning have beenidentified: dynamic, viscous and revertedrubber.

Dynamic hydroplaning, which is also calledaquaplaning, is related to speed and tyrepressure. High speed and low tyre pressure arethe worst combination, giving the lowestaquaplaning speeds. During total dynamichydroplaning the tyre lifts off the surface andrides on a wedge of water like a water ski.

5focus spring 09

Above: an Embraer 145 similar to the aircraft that

suffered a runway overshoot

Above Left: Figure 2 – marks of hydroplaning on

the runway. Above Right: Figure 3 – Rubber

dumped from tyre.


6 focus spring 09

You have probably experienced this whendriving through large puddles on the road, andfelt the steering lighten. Dynamichydroplaning will occur at speeds above 9times the square root of your tyre pressure (inpounds per square inch). For instance the146/RJ with tyres at 155 psi wouldhydroplane at speeds above 112 kt, the ATP(86 psi) above 84 kt, and the Jetstream 41(100 psi) above 90 kt When dynamichydroplaning occurs it may lift the wheel offthe runway and prevent spin up or, if anti-skidis not being used, cause the wheel to stopspinning. Once started the hydroplaningcould continue to much lower speeds.

Viscous hydroplaning occurs on all wetrunways and describes the normal slipperinessor lubricating action of the water. Viscoushydroplaning reduces the friction, but not to

such an extent the spin up on touch down isprevented. The most positive way to preventviscous hydroplaning is to provide texture to thesurface – hence grooved runways.

Reverted rubber hydroplaning is similar toviscous hydroplaning in that it occurs with athin film of water and a smooth runwaysurface. It often follows dynamic or viscoushydroplaning where the wheels are locked.The locked wheel creates enough heat tovaporise the underlying water film thusforming a cushion of steam that eliminatestyre to surface contact, and begins to revertthe rubber, on a portion of the tyre, back to itsuncured state. Once started, reverted rubberhydroplaning will persist down to very lowspeeds – virtually until the aircraft comes to astop. During the skid there is no steeringability. Indications of reverted rubberhydroplaning are distinctive white marks onthe runway, and a patch of reverted rubbersimilar to the uncured state on the tyre. It isalso likely that melted away rubber will befound on the runway.

The increase in stopping distance as a result ofhydroplaning is impossible to predictaccurately, but it has been estimated toincrease it by as much as 700%. The reducedbraking action on a wet runway may preventthe aircraft from decelerating normally withthe anti-skid system operational. But the anti-skid system will provide optimum braking –

switching it off will most likely lead to wheellock up and burst tyres.

Conclusion

I hope that this article has provided some foodfor thought. Our northern winter will soon behere with wet weather and we will be facedwith conditions similar, and worse to thosedescribed above. Of course other areas in theworld suffer similar conditions in monsoonsand heavy rain. I can do no better thanreiterate the advice given in the previous issue:

■ A good landing starts with a goodapproach.

■ Think before accepting a downwindcomponent.

■ Land in the right place at the right speed.

■ If in doubt go around.

■ Trust the systems and brake for effect,not comfort.

Don’t eat into your margins

This article is reprinted from JETSETS

Magazine with kind permission of BAE Systems

Regional Aircraft.

Above: wet runways contamination can cause hydroplanning


focus spring 09 7

by Simon Stewart and Derek Brown, easyJet

This article outlines the background forthe establishment of a Fatigue Risk

Management System (FRMS) in an airline.An FRMS was developed to enable fatiguerisk to be managed in an evidence-based,dynamic and comprehensive manner. Thepurpose of the FRMS is to ensure thatemployees (initially flight crew, then cabincrew, ground operations, engineering andremaining employees) are sufficiently alertso that they can operate to a satisfactorylevel of performance and safety. The FRMSis based on scientific principles, includingmethods for data collection and analysis.Among other benefits, the system enableseasyJet to monitor and understand therelationship between rostering, operationalvariables and crew fatigue and workloadand to identify where controls need to beimplemented or strengthened.

easyJet has attained significant market sharewithin the competitive air transport industrythrough being dynamic, innovative andattaining maximum aircraft and crewutilisation.The airlines’ success depends on thetraining, professionalism, and health of flight-crew to deliver a safe standard of operation fortheir customer base. Intensive short-haulflight schedules are a necessary element ofLow Cost Carrier (LCC) operations to ensureprofit margins and reflect specific challengesfor safety management with regard to humanfactors considerations and crew fatiguealleviation. Regulatory differences across theEU and scheduling practices reflecting highduty hours, incorporating multiple sector dutydays and minimum crew rest, have beenproposed as contributing factors for crewfatigue (Rosekind et al, 1997; Goode, 2003;Caldwell, 2004). Current research suggeststhat there is a relationship between crewfatigue and an increased risk of incidents andaccidents (Batelle Memorial Report, 1998).However, fatigue is a controversial issue thatremains difficult to quantify within an airlineoperational environment. The Civil AviationAuthority (CAA) introduced the firstcomprehensive regulation in the form of anadvisory document CAP 371 (The Avoidanceof Fatigue in Aircrews) based on the provisionsof the Bader report (1973). The fourth editionof this document was released in January2004 however the guidance limits given byHours of Service frameworks are largelyunsupported by scientific field based research(Dawson & McCulloch, 2005; Cabon et al,2002).The purpose of regulations, as proposed

by the EU through the European AviationSafety Agency (EASA) and Civil AviationAuthority (CAA), is to provide a fatigue-alleviating framework (Flight Time Limitations,FTL) for airlines. These FTL guidelines (CivilAeronautical Publication, CAP 371) allow anairline rostering department to conductrostering practices that minimise flight-crewoperational fatigue. Current regulations havebeen principally designed around long-haulcommercial flight operations and don’t reflectthe high aircraft and crew utilisation practicesthat reflect LCC operations (BALPA log, 2004;IATA Research Study, 2001).

The IATA Research Study (2001) cited that

crew fatigue may be affected by the following

contributing factors:

“Increased flying hours;

Unsympathetic rostering practices; and

Absence of adequate JAA/EU rules on FTL.

The above factors in turn may be influenced by:

Shortage of experienced pilots;

High utilisation rates of crews; and

Lack of operations/ administration support.

These factors will be in turn influenced by:

The company organisational or corporate

culture; and

The crew professional culture”

This review shows that fatigue within an airlinemust be managed at many levels and thatdetection capability for fatigue risk requires aproactive element and not simply focusing onactive failures and retrospective investigation of

Airline Fatigue Risk Management:purpose and benefits


8 focus spring 09

events. Within events the capability mustextend to the ability to determine and evidencefatigue’s influence on safe operation as a rootcause or contributory factor.

The ICAO Fatigue Risk Management subgroupcomprising leading fatigue researchacademics from across the industry cite adefinition of fatigue as:

‘A physiological state of reduced mental orphysical performance capability resultingfrom sleep loss or extended wakefulnessand/or physical activity that can impair acrew member’s alertness and ability to safelyoperate an aircraft or perform safety relatedduties’ (ICAO FRMS sub group 2007 andEASA Draft regulations EASA Ops AMC 1 toMS.OPS.8.205(a)-2008).

This definition states that fatigue riskprecursors (mental, physiological andemotional) interact with operational processto manifest fatigue performance decrements.Such performance changes need to bedetected and assessed (safety reports, surveys,domain sleep deprivation studies,observational field studies) as operational riskand reported and managed to maintain anacceptable safe level of operation. Fatiguemanagement requires both proactive andreactive capability within the risk

management process.This definition of fatigueis used as the template for design of a FatigueRisk Management System at easyJet. The nextstep is to evolve this relational framework intoa process that can represent fatigue as a riskwithin a social-technical system such as anairline. The first step is to review the literatureand summarise the use of controls, causes andconsequences of fatigue.

Fatigue Risk Management at easyJet

In 2006 easyJet became the first Europeanairline to implement an FRMS.The key benefitof managing fatigue risk is obviously theprevention of accidents, however it issimplistic to view fatigue risk management asmerely a safety initiative. It is in thecommercial interests of managers tounderstand the nature of fatigue risk andrecognising this easyJet have incorporated theFRMS into their core business model. Knowingoperational risk exposure enables managers toensure that the short-term profitability issimultaneously considered with brandprotection in mind.

easyJet have also implemented the FRMS inpreparation for the ICAO SMS legislation thatis due to become effective from January 2009.ICAO will require airlines to implement acontinuous safety monitoring program withmanagement accountability for operationalrisk. In a similar vein, in the EU thestrengthening of the European Aviation SafetyAgency (EASA) means that national regulatorybodies will have less oversight in the futureand airlines will need to implement internalgovernance, or in other words risk awarenessand ownership and a strong internal auditprocess (Hampton Report, 2005). In the UK,the CAA is already under pressure to cutresources and place more emphasis oninternal self governance. Furthermore,corporate manslaughter legislation thatbecomes effective in the UK (2008), statesthat being unaware of a risk does not meanthat managers are not accountable.

Insurers and underwriters are also promotingthe application of proactive risk managementstrategies that demonstrate safety awarenessand capability (Airline Business RiskManagement Survey, 2007). They seek whatdistinguishes a company from regulatorybaselines such as corporate managementsystems and enterprise risk management

processes and will link airline premiums againstrisk signature (AeroSafety world, 2007).

easyJet FRMS Purpose

To maintain an acceptable level of safety,through the application of scientific principlesbased on human physiology and knowledge,determined from data collection, riskinvestigation and analysis. In doing so itallows greater operational flexibility of crewscheduling, in comparison with prescriptivelimitations of flight and duty time. The FRMSforms an integral part of easyJet’s establishedSafety Management System (SMS).

Fatigue Risk Management applies standardmanagement control principles in order tomitigate fatigue risk in airline operations,through processes based on sharedresponsibility amongst management andcrew members acting within a just culture.

Functioning

The objective of the FRMS team is to facilitatethe airline’s commercial success throughenhanced productivity, delivered within a risk-controlled environment. The FRMS team alsoadd financial value to the company, based onachieving a lowered risk profile, evidencedthrough a significant reduction of insurancepremiums; together with lower levels of crewattrition and sickness costs throughmaintaining sustainable rostering practices,whilst minimising the risk of serious incidents.

In such a complex operating environmentfocussing on simple compliance with FTLrequirements (i.e. 900 hours productivity peryear) cannot be justified or assumed toprovide adequate legal protection againstsafety risks for the easyJet business model aswe have demonstrated through our previousexperience. Operators are responsible and areaccountable for their own risk with the overallrequirement of achieving a level of risk as lowas reasonably practicable.

The high levels of crew utilisation now being

achieved has led to concerns that the degree of

protection against fatigue offered by basic

compliance with those quantitative FTL

provisions specified in CAP 371 Annex A is no

longer sufficient for larger companies.

CAA Draft FODCOM 2008


9

The FRMS team must establish a full androbust safety case, supported by scientificresearch, incident investigations, metrics, andreporting in order to identify risk,†prior toimplementing each and every rosterconstraint to the business.

After identifying the risk, that safety case isput before the FRMS SAG made up of therelevant post-holders. It is these post-holderswho own the risk and it is they who make thedecision - not the FRMS team - to implementmitigating strategies in the form of rosterconstraints in order to maintain an acceptablelevel of safety.

Although a fully fledged FRMS is neither acheap nor an easy option, it provides asystematic and objective process of managingfatigue risk and can add significant value tothe business model. For this to happen itneeds to be firmly embedded in theoperational philosophy of the operator, havethe full support and the visibility of the mostsenior management in the company, and willwork only if it is continually nurtured througha ‘just and open’ culture.

The FRMS does not represent a ‘bolt on’compliance system that acts a barrier tocommercial viability. It represents operationalflexibility and opportunity. It facilitatesoptimal performance and protection withinevidenced safety criteria in pursuit ofcommercial opportunity.

In doing so it satisfies the corporatephilosophy enshrined in the 5 values ofeasyJet - Safety, Teamwork, Pioneering,Passionate and Integrity.

The benefits of FRMS to easyJet

The benefits of managing fatigue like anyother risk i.e. within a SMS are significant.Reasons for investing in an FRMS include notonly avoiding pitfalls of FTL:

1) Knowledge of fatigue risk exposure is a

fundamental element of business model -FRMS gives you measures of risk exposure. It isin the commercial interests of operators tounderstand the nature of fatigue risk andmanage it effectively for continued safeoperation and viability in the commercialenvironment. safety links to commercial viabrand protection.

■ Reduction in frequency of medium andhigh risk events

■ Reduction in oversight from the regulatingauthority

■ Reduction in attrition

■ Reduction in Fatigue lost duty days andsickness incidence due fatigue relatedfactors

■ Increased crew morale and CRMperformance

The quantification of the benefits a reductionin fatigue associated with altered workschedules has been demonstrated in thenuclear industry by Fleishman et al (2006)with the following benefits:

■ Reduction in frequency of severeaccidents

■ Reduction in plant shutdown risk

■ Improved security

■ Reduction in frequency of lost andrestricted work cases

2) New ICAO SMS legislation becoming effectivefrom January (2009) requires airlines toimplement a continuous safety monitoringprogram with management accountability ofoperational risk. EASA means that the CAA willhave less oversight and airlines need internalgovernance (risk ownership), Within the EU,with the incremental transference of authorityand responsibility to EASA, the CAA is undertremendous pressure to cut resource with moreemphasis (and reliance) being placed on astrong internal company audit process (internalgovernance). An internal governance programbased on accountability, transparency,predictability and participation (Gardiner, 2005)supports continuous oversight of operationalrisk by the Authority and allows them to focusregulatory resource against audit risk areas,maximising benefit to the business model.

3) Risk signature. Insurers and underwriters areseeking the application of proactive riskmanagement strategies that demonstratesafety awareness and capability throughmitigation of the risks of incidents & accidentsagainst easyJet airline peers in the industry(Airline Business Risk Management Survey,2007). They seek what distinguishes a

company from regulatory baselines such ascorporate management systems andenterprise risk management processes and willlink the decrease in airline premiumscommensurate with risk profile (Underwriterperspective-AeroSafety world, 2007).

4) Corporate liability. The message from theregulators is clear: legal duty hour limits donot necessarily ensure safety and riskownership and accountability lie squarely onthe shoulders of the operator (CAApresentation Crew Management Conference,Brussels 2007). Corporate Manslaughterlegislation (effective UK Ministry of Justice,2008) informs us that not knowing or beingunaware of the risk does not mean that youare not accountable.

Unless the FRMS system is provided withaccurate and timely information regarding thesystem state (that can be processed andassimilated into a fatigue risk format foranalysis) the program will at worst beineffectual (box ticking exercise) and at bestprovide senior management with aninaccurate system overview of a key riskindicator on which operational decisions arebased. These decisions may directly impingeon system fatigue risk. Furthermore, theinformation sources for the FRMS systemshould be dynamic, in-effect ‘real-time’ sothat a fatigue risk model can be developed,that provides a platform from which systemprojections on performance can be made. Thisallows the system to be employed proactively,to provide senior management with anaccurate state of operational fatigue risk. TheFRMS then forms part of the companycommercial business plan that accounts forfatigue risk to maintain operational integrityduring projected expansion activities. TheFRMS system must encompass an accurateassessment of network fatigue tolerance levelscombined with work-related fatiguedetermined from hours and patterns of work.

focus spring 09


Battling Level Busts

10 focus spring 09

Departing from your cleared flight level

is never a good idea, especially in

Europe’s crowded skies, where a level bust

could lead to a loss of separation with

another aircraft. Business aviation, which

accounts for about seven percent of flights

in the United Kingdom, was responsible for

almost 20 percent of the level busts

recorded in that air space, and five of the

eight most serious losses of separation

following a level bust.

Between January and September 2008 in theairspace in which NATS, the U.K. airnavigation service provider, provides the airtraffic control (ATC) service, there were 356incidents involving business jet aircraft.Fourteen of these incidents were within thehigher risk category and involved a loss ofseparation, mainly due to level busts.

Responding to this trend, NATS has lookedmore closely at the specific issues posed bybusiness aviation with regards to level busts.

As part of its efforts to reduce the numberand severity of level bust events, the NATSLevel Bust Workstream, a working group ofrepresentatives from across the company, hasbecome increasingly concerned about theprominence of business aviation aircraft, inparticular non-U.K. registered, non-commercial operators, in the statistics. Ofconcern not only are the numbers but theseverity of the busts; business jets caused 5 ofthe 8 most serious losses of separation

resulting from level busts in the 6-monthperiod that ended in June, 2008 (see Table 1).

The NATS Level Bust Workstream determinedthat the evidence of a problem is compelling.Going back to January, 2007, the businessaviation community accounted for 10 out ofthe 19 most serious level busts recorded, 52%of the number of serious bust events. Eight ofthose ten events involved non-U.K.-registeredaircraft. Given this disproportionateinvolvement in the higher severity events, it isclear there was a need to focus effort onworking in partnership with the businessaviation community.

NATS believes that there are many reasons forthe unwelcome prominence of corporate jetsin the level bust event data. The nature ofbusiness flying is such that crews often findthemselves flying into airports and associatedairspace for the first time.As infrequent visitors,a lack of familiarity with some of the morechallenging procedures in U.K. airspace isprobably a major factor. Among thesechallenging procedures are step-climb standardinstrument departures (SID), a feature at manyof the London region’s outer airports, wherebusiness aircraft are frequent visitors.

There have been many instances recorded,and not only among the business aviationcommunity, of crews “falling up the stairs” ona stepped profile. For business aviation, if theaircraft is flown by a single pilot, or if the crewis distracted from briefing the profile correctly– perhaps by having to perform functions

carried out by other staff such as cabin crewon the airlines – the possibility of an incorrector incomplete brief is increased. Throw intothe mix the fact that many of the businessaviation crews may not have the level of flightoperations support available to airline crews,and the very high performance of the aircraftthat are being flown, especially in the climb,and the reasons behind the prominence ofcorporate jet aircraft in the data becomemore obvious.

NATS has made great efforts to reduce thelevel bust threat, having introduced Mode Sradars that display each aircraft’s selectedflight level (SFL) on the radar workstationswithin the Manchester Area Control Centreand in the London Terminal Control OperationsRoom at Swanwick Centre. Although this hashad a very positive effect on reducing levelbusts, with controllers now able to see theflight level dialled into the mode controlpanel/flight control unit (MCP/FCU) by pilotsfollowing an instruction to climb or descend, ithas not been the complete solution.

For example, the displayed SFL will not takeinto account any altimeter setting error madeby the pilot. This is a common causal factorof level busts in the U.K., where the transitionaltitude to change altimeter settings fromlocal pressure readings (QNH) to 1013.2mb(29.92 inches) is 6,000 ft in controlledairspace and 3,000 ft outside it.

It is appreciated that particular standardoperating procedures (SOP) are chosen to

by Peter Riley,

NATS tracks down why business jets figure prominently in altitude deviation in UK airspace.


enhance operational effectiveness accordingto the nature of the operation. However,where a pilot has programmed a step climbprofile into the flight management system(FMS), unless there is an additional SOP to setthe profile restrictions in the MCP, there can bea disparity between the aircraft’s SFL and theprogrammed SID, which can cause increasedcontroller workload as they try to ascertainwhether or not there is a level bust developing.

While there is little possibility that step-climbSIDs will be eliminated in the short term,avoidance of this procedure now is enshrinedas a basic design principle for all future NATSairspace changes. In the interim, there havebeen some successful mitigation measuresapplied at some NATS units; for example,providing with the departure clearance anexplicit warning of the existence of a step-climb SID.

While helpful, Mode S SFL capabilities maycreate new hazards, data is beginning toindicate: When the SFL displays the correctlevel to which an aircraft is cleared, controllershave a level of confidence in the crew’scorrect handling of the climb or descent that

focus spring 09 11

SERIOUS LEVEL BUST EVENTS (Safety Significant Events 1-3) in airspace in which NATS provided a service – 01 Jan 08 – 30 Jun 08

Date and Aircraft Summary Primary Causal Factors

14/01/2008 The FA10 descended below its cleared level and came into confliction with a B738 which Incorrect response to TCASwas under the control of a different sector. Slow TCAS response was to ‘maintain

AVANT FA10 passenger comfort’. Rate of turn/climb/descent

07/03/2008 The F2TH was instructed to climb to FL140 but climbed to FL144 and into conflict with Incorrect response to TCASother traffic. The F2TH had a very high rate of climb and may have mis-interpreted

BPK F2TH a TCAS RA. Rate of turn/climb/descent

10/03/2008 An FA50 was instructed to climb FL120, and approaching FL110 was given traffic Incomplete readback by correct information on an aircraft 1000ft above. The FA50 climbed to FL127. aircraft

DET FA50 Not Heard

11/03/2008 On departure the F50 was instructed to climb to FL80. The aircraft was later observed Altimeter setting errorat FL87. This level bust was as a result of the pilot climbing on the QNH.

LAM F50 Not seen

01/04/2008 An inbound aircraft was descended to FL120. An outbound C560 was climbed to FL110. Incorrect response to TCASBoth aircraft approached BPK at the same time. The C560 was observed climbing to

BPK C560 FL117 - before descending again. The inbound aircraft received a TCAS RA. Poor manual handling

11/04/2008 An LJ45 was instructed to climb to FL80 against traffic descending to FL90. The descending Incorrect response to TCAS traffic reported a TCAS Climb. The LJ45 reported that it had also received a TCAS Climb.

BKY LJ45 It had climbed at 2500fpm with less than 1000ft to go. Responded to TCAS/GPWS

26/05/2008 On climb out the student pilot exceeded the cleared level by 600ft before the training Correct pilot readback followed captain could intervene. by incorrect action

HON B733 Pilot under training

03/06/2008 Traffic in the hold was descended to FL 70. The readback from the pilot was garbled by Pilot readback by incorrect another inbound aircraft. The cleared levels were not clarified by controller and an aircraft

ABBOT B738 incorrect callsign descended to FL70, losing separation. Not Heard

Reporting period Jan. 1, 2008–June 30, 2008. Source: NATS

Above: London’s complex airspace can trip up infrequent visitors


may turn out to be misplaced if the pilots donot adhere to sound airmanship principles ofreducing the rate of climb or descentapproaching the assigned level.

Further, a high rate of climb or descent cantrigger a traffic alert and collision avoidancesystem (TCAS) warning on one or moreaircraft under these circumstances, and theresolution advisory (RA) often is to continuethe ongoing climb or descent. When thisoccurs, the SFL indication quickly becomesmeaningless, and a situation the controllerhad every reason to believe was under controlcan quickly become a level bust. This is one ofthe reasons an “incorrect response to TCAS”might be attributed to a level bust, eventhough the actual response to the RA mayhave been correct.

In fact, an incorrect response to TCAS isrecorded in half the level bust events.

Analyses of TCAS-related events by the NATSTCAS Working Group have found three majorcontributory factors. The most numerous by farwere aircraft with high rates of climb or descentapproaching the cleared level; around 75percent of recorded TCAS events involve aircraftcleared to vertically separated levels generating‘nuisance’ TCAS RA manoeuvres. Incorrectresponses to TCAS RAs were less frequent, butoften had far more serious consequences.

The causes behind an incorrect TCAS responsevaried. In some, crews reported choosing notto follow the RA to maintain passengercomfort or because they had visually acquiredthe other aircraft in the encounter. A morecommon cause was misinterpreting an RA, inparticular misunderstanding an “adjustvertical speed” RA, an instruction to reducethe rate of climb or descent.

A normal TCAS response also can cause pilotsto fail to maintain their ATC-cleared levelwhen correctly following an RA; for example,an aircraft is climbed to a level with 1000 ftstandard separation below another aircraftand receives an “adjust vertical speed” RA.While staying within the green arc of theTCAS climb/descent guidance, the aircraft canlevel at 600’ beneath the traffic, preventing acollision but eroding standard ATC separation.

The increased risk of non-response, lateresponse or incorrect response to TCAS – aswell as possible pilot slow reporting of adeviation in response to a TCAS RA – aresome of the many issues that have beenidentified as being more common in single-pilot operations. The introduction of Very

Light Jets (VLJs), particularly when operatingwith one pilot, complicates this picture.Although low performance VLJs are likely tobe treated from a controlling perspectivemuch the same way as current turboprops,mid performance VLJs will have highercruising levels combined with slower speedsthan other aircraft at those levels. This is likelyto add to controller workload, and, given theevidence of incorrect response to TCASalready identified, NATS will need to monitorclosely the level bust performance of singlepilot aircraft.

For NATS, having identified the level bust trendin the business aviation sector, the greatestchallenge is to reach the correct audience withits mitigations. NATS has a very successfulsafety partnership agreement with manycommercial operators in which it exchangesdata and discusses issues in an open and frank

forum. It also provides on a quarterly basisspecific data on level bust performance tonearly 50 operators, including some businessjet fleet operators such as Netjets.

However, for the business aviationcommunity beyond the U.K. Air Operator’sCertificate-holder sector, it has proven verydifficult to reach the crews in an effectiveway. Small operators are too numerous,transitory, dispersed and infrequent U.K.airspace visitors to develop the longer-termrelationship necessary to bring down levelbust numbers. NATS has worked to developties with trade associations and simulatorservice providers, and has taken advantage ofrelationships with local handling agents toprovide publicity and awareness initiatives.Ultimately, however, these strategies do notaddress the fundamental issue of directlyengaging the target audience.

focus spring 0912

AVOIDING LEVEL BUSTS

NATS has identified that there are a number ofthings that aircrew, especially business aviationcrews, can do to minimise their chances of beinginvolved in a level bust:

Crew Preparation

■ Ensure departure and arrival briefs arecomplete and include Transition Altitude (lowin the UK), first stop altitudes on stepped-climb SIDs and the impact of low QNHswhen transitioning from altitudes to flightlevels (FL) and vice versa.

■ Understand the profile, brief the profile, flythe profile. Do not “fall up the stairs” onstepped climbs. Carry out a specific review ofthe SID to be flown with both pilotsparticipating.

Communications

■ Both pilots should wear headsets, monitorthe frequencies and listen to the clearance.

■ Use standard phraseology and avoidunnecessary radio chatter. When not sure, donot repeat clearances as a question; ask ATCto say again.

■ When changing radio frequency, listen afterthe change before transmitting; be alert forsimilar call signs on your frequency; if youhear a readback error, let ATC know.

■ Beware of confusing heading and levelnumbers; do not confuse 2s and 3s — e.g.FL230 / FL330; beware of a non-existent firstdigit, e.g. FL90 not FL190.

■ On first contact, always pass to ATC yourcurrent cleared level.

Operational good habits

■ One pilot programs the FMS, another checksit; crosscheck every MCP/FCU change,visually and verbally; crosscheck altimetersettings.

■ Apply CRM skills, e.g. pilot monitoringstandard call for altimeter setting on passinga set flight level; call out altitudes passingand feet to go approaching the level off.

■ Avoid high rates of climb or descentapproaching the level-off point to preventunnecessary TCAS alerts; consider limits of3000 fpm with 3000ft to go; 2000fpm with2000ft to go; 1000fpm with 1000ft to go.

■ Understand how TCAS works and all TCAS RAwarnings, including those not frequentlypracticed in the simulator.

■ Set the clearance given, not the clearanceexpected.

■ Maintain a sterile cockpit below FL100.

Pete Riley, a controller now working at NATSCorporate and Technical Centre in the UK, isNATS Level Bust Workstream Lead

– NATS


In an attempt to go further in addressing thisissue, NATS has created a new workstreamwhose focus is on business aviation, as well ascooperating with the Business Aviation SafetyPartnership. The work of these groups willconsider the following areas:

Training Establishments

■ Pilot training for global airspace and notjust the country within which they arelearning; and,

■ Pilots training for a variety of conditions,e.g. emergencies, poor weather, etc.

Regulation

■ Promoting carriage of specific avionicequipment, such as Mode S and, in some airspace, airborne collision avoidance systems

■ Adequate licensing, training andcompetency arrangements to expandknowledge of TCAS responses andairspace, airports and poor weatheroperations.

Briefing

■ Facilitate access to adequate briefingmaterial through handling agents, etc.

■ Encourage correct briefing by theoperators.

The focus of these groups is supported by therecent publication of the Business Jet SafetyResearch Report, a Statistical Review andQuestionnaire Study of Safety Issuesconnected with Business Jets in the UK (15Aug 08). This, in turn, has resulted in theformulation of a U.K. Civil Aviation Authority-led Safety Action Plan for Business Aviation.

Although the work is not yet finalised in thisarea, it is clear that the need for specificattention to be given to this sector of theaviation industry is greater than ever.

focus spring 09 13


The SKYbrary Project – A Single Source of Aviation Safety Knowledge

How often do we hear people say in the

aftermath of an accident, "This is a

known problem"? If a pilot, a controller or

a safety manager in an airline or air

navigation service provider wants to find

out information about a specific problem

or issue that he is encountering, where can

he go to find knowledge, examples of

incident and accident reports, advice on

best practice, solutions to his needs,

training material and links to other

sources of information?

Most organizations in the flight safety worldpublish their own journals and docurnents ontheir websites but don’t link very well to othersources. There are numerous amateurwebsites devoted to aspects of flight safety,some of which are an excellent source of bestpractice, but how can the visitor be sure thatthe advice is correct?

How can we ensure that our collectiveknowledge and experience is shared andaccessible to all in the business? Furthermore,how can we ensure that the knowledgeprovided helps to shape behavior, andpromote best practice?

The SKYbrary Project – Creating a “One

Stop Shop” for Aviation Safety Knowledge

Eurocontrol’s Safety Improvement Sub-Group(SISG), which comprises safety representativesfrom Europe’s air navigation service providers,is a consultation group that acts as a forum forsafety lesson dissemination, particularly inrelation to ATC significant events and safetymonitoring in general in order to advise onsafety improvement in the ECAC1 area.

The SISG was interested in creating a wiki-likeknowledge base, combining the power ofWikipedia whilst ensuring quality ofinformation to serve the needs of aviationprofessionals worldwide, with the aim ofproviding safety managers with solutions to theproblems they were encountering in their day-to-day work. Eurocontrol’s HindSight magazinewas launched at this time, and it was also theintention that this would evolve to becomesome form of online knowledgebase to meetthe needs identified by the SISG.Work began in

2005-2006 on the development of the concept,design and subsequently the population of anaviation safety knowledgebase, which acquiredthe name of SKYbrary. This initiative soongained the support of both Flight SafetyFoundation and ICAO, support consideredcrucial for the project to have credibility andaccess to existing knowledge.

Collecting and then organizing and deliveringaviation safety knowledge in such a way that itdoes not remain static is an enormous challenge.

It quickly became obvious that anyknowledgebase would need to extend beyondthe needs of the air traffic control communityand must also address the needs of theoperators.The focus of the project is therefore,for now, on commercial air transport operatorssince the potential safety benefit of addressingthe needs of that community will also improvethe overall safety of the whole aviation systemfor the benefit of all.

What is SKYbrary?

The SKYbrary knowledgebase is built on amediawiki platform and is a network of

hyperlinked articles, similar to Wikipedia, butwith more restrictive control over theauthorship rights, and is available free ofcharge to the aviation community via theInternet. Substantial bespoke work has beendone to the look-and-feel as well as contentmanagement logic, to meet the requirementsof Eurocontrol and its partners.

The Article is the prime content item inSKYbrary and it can contain links to relatedarticles, Bookshelf documents, or externaldocuments and sources. Articles follow thesemantics and style of classic encyclopediaentries – precise, concise and concept-related.

It is important to note that SKYbrary's aim is notto reproduce the entire domain of aviation safety,but to provide an umbrella for easy search,reference and links to the credible resources.

Visitors can browse selected categories ofinformation, look at recent Safety Alertsissued by Eurocontrol, or access a growingBookshelf of reference documents, includingAccident and Serious Incident Reports.SKYbrary also gives to the user a uniqueopportunity to search in ICAO documents.SKYbrary provides a coherent link from

14 focus spring 09

by Tzvetomir Blajev, John Barrass, EurocontrolAccessible and Comprehensive Safety Knowledge


knowledge articles to direct behavior-influencing applications like e-learningmodules, videos, posters and presentations.

Accessibility

Although in the pre-launch stage the authorand editor role have been merged, it isenvisaged that the author population ofSKYbrary will eventually be built up from theSKYbrary user population.

Each of the authors can draft articles in aspecial area of SKYbrary (the “work inprogress” area).

The editorial team discusses to whichcategories the drafted articles belong. Percategory, an editor oversees the quality ofcontributions and can edit contributions. Theeditor not only looks at the content of thearticles, but to the references provided as well.SKYbrary is not only a compendium ofaviation safety articles, but a portal to thewider network of aviation safety knowledge. Itis the task of the editor to ensure thatoutward links from SKYbrary equallyrepresent high quality content.

If a (registered) user does not want to draft anarticle, they have the option to voice ideas forarticles to be written, using the "Request anArticle" facility. If an article meets theeditorial standards of SKYbrary, the SKYbrarycontent manager can move the article ontothe main SKYbrary space. As indicated earlier,the content manager also manages userrights in SKYbrary.

It is important to emphasize that the SKYbrarypartners (ICAO and Flight Safey Foundation)provide their content to the SKYbrary platformas well, thereby greatly enhancing the breadthand depth of the subject matter provided tothe user population.

Defining the Scope

Initially, the project concentrated onoperational issues of concern to the SISG andwhich were the subject of Eurocontrol safetyimprovement initiatives. This has since been

extended to cover 14 principal categories:CFIT, Runway Incursions, Runway Excursions,Loss of Control, Level Bust, Fire, GroundOperations, Human Factors, AirspaceInfringement, Bird Strike, Air-GroundCommunications, Loss of Separation, WakeVortex Turbulence and Weather.In addition to Operational Issues, two furtherportals were created: the Enhancing Safetyportal, which includes the categoriesAirworthiness, Flight Technical, SafetyManagement, Safety Nets and Theory ofFlight, and the Safety Regulations portal,which includes the categories Certification,ESARRs, Licensing and Regulation. Theconcept envisaged that every category shouldbe kind of “tool kit”, providing users with easyaccess to background knowledge andsolutions, and contain no more than 30articles. Secondary articles, and articles of amore encyclopedic nature, or articles whichdo not fit neatly into any particular categoryare stored under a General heading.

Articles are linked together, as in Wikipedia,and a separate database, a Bookshelf, ofdocuments is slowly being built to providefurther reading. This includes accident andserious incident reports which are covered bya basic article within SKYbrary, linked toappropriate categories and articles, and acopy of the associated official report isincluded on the Bookshelf.

The organization and structure of SKYbrary issubject to constant review as the volume ofknowledge grows and feedback is receivedfrom users.

Who is the Target Audience?

SKYbrary is aimed at anyone interested inaviation safety. The production process is,however, targeted at explicitly bringing valueto three groups of stakeholders:

■ Safety – Safety Managers, IncidentInvestigators, Flight Safety Officers,Safety Experts, Safety Regulators.

■ Operations – Air Traffic Controllers, Pilots,ATC Operations line mangers, Chief pilots,Operations experts.

■ Training – Training Experts, Instructors.

Priorities

While the framework of the SKYbraryknowledgebase is becoming mature, thesubject coverage is in places quite thin. Thepriority for content development is targetedat the major killers in the aviation industry:

15focus spring 09

Above: 9,232 visits came from 1,762 cities


16 focus spring 09

■ Loss of Control (LOC)

■ Controlled Flight Into Terrain (CFIT)

■ Runway Excursion (RE)

■ Runway Incursion (RI)

■ Loss of Separation (LOS)

Within these specific categories, the target isto achieve 100 percent of subject coverageby June 2009. Achievement of that target isof course a subjective assessment, and theknowledgebase will and must continue togrow. Over the same time frame, it is hopedthat coverage of all other categories withinSKYbrary will be at least 60 percent ofsubject coverage.

Measuring Success?

SKYbrary currently has over 1,200 articles and500 documents stored, including nearly 100official accident/serious incident reports linkedto operational safety issues.

Visitor numbers passed 10,000 per month inAugust 2008 and analysis shows that whilethe majority of visitors are based in Europe,SKYbrary is attracting visitors from all overthe world.

Help Wanted

It has taken two years of considerable effortto get SKYbrary ready for launch. A great dealhas been achieved in this me but for the

project to go forward, we need greaterengagement from the community in order tobuild the depth and breadth of knowledgethat we aspire to.

1 ECAC: European Civil Aviation Conference,

consiting of 42 member states

C O M I N G S O O N

Look out for the new UK Flight Safety Committee Websitewww.ukfsc.co.uk which will be launched shortly.


focus spring 09 17

Safer Skiesby Hazel Courtney, CAA Research

The UK Civil Aviation Authority (CAA)

research programme is much reduced

in areas that support rule-making, as this is

largely now the responsibility of the

European Aviation Safety Agency (EASA).

However, there are still good reasons to do

research.The most common categories are

as follows.

Reduce restrictions: Research can produceinformation that allows regulations to bemade less restrictive or more flexible, resultingin greater freedom for industry. Restrictionscan be reduced because research has shownwhere this can be done safely, e.g. SAFE pilotfatigue model, pilot's colour vision andhelideck landing (wind-shear criterion).

Safety improvements: Research developssolutions that target safety directly, in areaswhere risks are known. Examples include newtype rating training syllabus for highlyautomated aircraft, fire training improvementsfor cabin crew, health and usage monitoringsystems, helideck landing (lighting, andmoving decks), carburettor icing andgyroplane design projects.

Safety investigations: Safety risks may besuspected or rumoured but before CAA cantake action or raise the issue with EASA, thenature and extent of the problem has to beinvestigated. The measurement of manualflying skills and data analysis of maintenanceerror are examples of this.

Safe introduction of new technology: Safeintroduction of new technology sometimesneeds support from research. Examplesinclude the required navigation performance(RNP) terminology database, fire foamtesting, inspection reliability of compositematerials, and projects related to globalnavigation satellite system (GNSS)/globalpositioning system (GPS) approaches, both inmainland airports and offshore.

Regulatory actions: Policy decisions aresupported with information, such as researchon runway incursions technologyinterventions, ground fire fighting technologyinterventions, risk based oversight,inadvertent instrument meteorologicalconditions (IMC) and occurrence reporting byground handlers. There is also a need to findways to demonstrate compliance with newEuropean regulations and this sometimes

requires research, for example the target levelof safety (TLS) compliance research.

Safety – CAA or EASA?

CAA continues to have a responsibility foroversight of safety for the UK industry whichincludes ensuring that safety risks areidentified and addressed – with the exceptionof aircraft certification where CAA acts onbehalf of EASA.

The emerging situation is that EASA will createthe requirements but national authorities suchas the UK CAA will continue to interpret andimplement them nationally – guided andmonitored by a standardisation function fromEASA. In time, EASA will conduct research tosupport its rule making activity but CAAresearch is generally not for rule makingpurposes. It does, however, provide informationthat is independent from commercial interests.

What to research?

Safety risks are identified systematically. Fatalaccidents to large public transport aeroplanesworld-wide are analysed to identify the mostfrequent types of accident and the commoncausal factors. A full ten-year update of thiswork (up to the end of 2006) will be publishedsoon as CAP 776 on the CAA website. This issupplemented by a detailed review of allhighrisk events involving the UK large publictransport aircraft fleet (reportable accidents,

serious incidents or A or B grade mandatoryoccurrence reporting scheme (MORS) affectingUK-registered or operated large publictransport aircraft anywhere in the world).

The MORS records almost 13,000 events peryear and these are used to monitor thefrequency of any known precursors to thesemajor events for the UK in general.

The most prominent risks emerging from theanalysis are then subjected to a rigorousgroup process where a multidisciplinary teamworks through potential contributors to thatrisk, from any source.

Pilot performance issues are prominent inCAA research. In the past ten years, the mostcommon type of fatal accident to large public

Other studies include incident occurrencereporting by ground handlers on the ramp.

Previously specialising in research relating to rule making initiatives, CAA Research nowfocuses on safety risk projects funded by industry. HAZEL COURTENEY* highlights some ofthe main drivers for research, examines what is delivered and asks whether it achieves valuefor money for its industry sponsors.

Above: Beechcraft King Air. CAA Research’s work include studies measuring pilot performance,pilot fatigue and colour vision.


focus spring 0918

transport aeroplanes world-wide is ‘loss ofcontrol’. Pilot performance is the primarycausal factor in two thirds of fatal accidents,and the most prevalent pilot errors to featurein these events are flight handling, and alsoinappropriate action (potentially related to arange of causes such as fatigue or training)

The UK is not immune. For example, in 2007there were 72 stall related events incommercial aircraft reported to CAA as MORS;60 triggered stick shakers/stall warnings, sevenwere classified as serious, including anoccurrence where the airliner appeared to stallat a pitch angle of 44° (based on preliminarydata, subject to change following fullinvestigation) during a go-around following anunstable approach and another where therewas a stall warning during climb out withdifficulty re-engaging autopilot.

In addition, many authoritative sources suchas UK Air Accident Investigation Board (AAIB)and the US Federal Aviation Administration(FAA) currentiy cite pilot interaction withautomation as a priority risk. There is alsoresearch requested by regulating departmentsdirectly, often to support policy decisions orfind ways to comply with new requirements.

Recent research projects

The activities below highlight some milestoneswithin the CAA Research programme duringthe financial year 07/08, includingachievement of a number of ‘world firsts’.Projects are externally contracted, and thecomplete programme is managed by three

research project managers who also drive thesafety planning process and provide much ofthe matenal for the CAA’s Safety RegulationGroup (SRG) safety plan.

Pilot performance – manual flying skills

measure and trial (joint funded with the

Guild of Air Pilots and Air Navigators

(GAPAN)) – For the first time an objective, fullyvalidated method of measuring pilot's manualflying skills has been developed. This moves farbeyond the early attempts to measure rootmean squares (RMS) of path deviation. Themethod has been applied to pilots flying with amajor UK operator (short haul) and early resultsshow that manual skills do reduce with servicein highly automated aircraft, particularlyairspeed management.Airspeed management isimportant in avoiding risks related to stall andalso runway excursions or overruns.

Type rating syllabus for highly automated

aircraft – A new type rating syllabus for highlyautomated aeroplanes has been developedusing robust research into training principlesand differs from the traditional syllabus: (i)moving away from the ability to state how theautomation works, toward the ability to knowhow to use it, and (ii) a change in sequencingto learn first how to achieve the task manually,and so understanding what the automation istrying to achieve and thus becoming betterable to monitor it. A trial is in progress with amajor UK operator and their training provider.As part of this work a simulation package of‘human factors faults’ has been developed.Thiscauses the simulator to fail as if either the pilotor co-pilot has made an undetected error. The

simulated error is introduced to evaluate theflight crew’s performance in recognising anddealing with the effects of the error. This isimportant since ‘pilot error’ is the single mostfrequent accident cause.

Runway incursions technology

interventions study – An evaluation of thevarious technologies potentially available toreduce the risk of runway incursions wasdelivered to the CAA Runway IncursionsSteering Group.

Pilot fatigue SAFE model – Following severalyears in development, a fully mature (VersionV) computerised model of pilot fatigue thatincludes crossing time zones has beenproduced, validated and trialled in an airlineroster. This was developed so that flightoperations regulators could assess industryapplications to vary their roster outside thenormal guidelines, and it is used two to threetimes per month on average for that task.Without the model it would be difficult tohave confidence to approve variations and somore rigid rules would be used.The system foraircrew fatigue evaluation (SAFE) is now beingtrialled for incorporation into commercialrostering software.

Pilot colour vision test – For the first time anaccurate, repeatable, computerised colourvision test has been produced, that is tailoredto the pilot flying task and will allow morepilots to fly (up to 35% of pilots currentlyexcluded due to defective colour vision maybe able to obtain a licence). As a side benefit,it was shown that by placing a filter in front oflights, such as PAPI (precision approach pathindicator) lights, it is possible to reduce thehuman error rate among normally sightedpilots as well as those with marginal colourdeficiency. The new system is currently withthe CAA Medical Department for evaluation.

RNP terminology database (joint funded by

GAPAN) – RNAV (area navigation) atld RNP(required navigation performance) approachimplementation is imminent in the UK andthere was concern voiced by operators thatterminology was proliferating out of control,with multiple definitions for the same termand multiple terms for the same definition.This could result in confusion on the flight deck(subtle differences in ‘definitions’ have alreadycontributed to fatal accident causal chains).Aninteractive, web based terminology database

Ground fire fighting technology has been studied by CAA Research.


19focus spring 09

has been produced and populated, andimplemented by key groups conducting rulemaking and procedure design.

Aircraft maintenance – data analysis of

maintenance error – A subject matter expertconducted a full analysis of MORS related toerrors in aircraft maintenance. This showedclearly which systems are most at risk (e.g.equipment and furnishings (especially escapeslides), power-plant, flight controls andlanding gear) but did not reveal any systemicerror pattern or indicate a particularintervention. It did show a marked effect ofthe human factors education programme onreducing certain kinds of maintenance error.

GNSS/GPS approaches – signal reliability

and integrity – A computerised model of GPSperformance has been produced. It is able topredict GPS performance for non-precisionapproaches in terms of the key RNP-RNAVnavigation parameters of accuracy, integrity,continuity and availability, and it can identifythe points on the approach that could sufferfrom GPS outages. Also, a method has beendeveloped and implemented to provideeffective performance monitoring of the GPSsignal in the UK, as recommended by ICAO.

Support to implementation of RNAV

(GNSS) instrument approach procedures

A successful trial of GPS non-precision, orRNAV (GNSS), approaches was conducted atsix UK airports, prior to CAA accepting

applications for such approaches fromsuitable UK airports. A website for reportingissues associated with GPS during these earlystages of implementation and its use ingeneral, is now being created.

Cabin safety, fire and evacuation – cabin

crew fire training – Simulated cabinevacuations were filmed at CranfieldUniversity and the footage contributed to aninternational cabin crew fire training package,launched at an international conference andnow being prepared as a webbased version. Ina separate exercise, over 2,000 current cabincrew responded to a website contributingopinions on fire training. This will now be usedfor a full training needs analysis.

Ground fire fighting technology

interventions study – The technical ability tofight cabin fires on the ground has notadvanced significantly since the catastrophe atManchester in 1985. A range of available firefighting technologies was compared for theirpotential to enhance fire fighting on theground and specifically for their life savingcapability. This showed that one particulartechnology had substantial advantage overothers available, and this information is nowbeing used in policy decisions.

Report on passenger experiences during

evacuations: A report detailing real passengerevacuation experiences has been produced,containing information collected over severalyears. This will provide insight for instructioncards, cabin crew training and cabin design issues.

Large public transport helicopters offshore

– HUMS (joint funded with FAA, CAA

Norway, Oil & Gas UK and Shell Aircraft)

Health and usage monitoring systems(HUMS) capability has been improved withvibration health monitoring (VHM) analysiscapability. A six-month in-service trial of theenhanced capability produced excellentresults and a second in-service trial isunderway. A study investigating the potentialfor HUMS for rotors showed potentialbenefits in this area.

Offshore helicopter use of GPS (joint

funded with CAA Norway and the EU)

Safety assessments for the use of GPS for en

route navigation, weather radar approachesand weather radar approaches enhanced byexisting GPS equipment fits have been

completed. The en route safety assessmentwas translated into a CAA Specification andimplemented by operators. A GPS-assisted, or‘hybrid’ weather radar approach wasdeveloped and tested and will beimplemented later this year.

Helideck landings (joint funded with CAA

Norway and HSE) – Lighting: Night landingson offshore helidecks have been previouslydescribed as landing in a ‘black hole’. Aprototype system of enhanced helidecklighting was designed and installed on a NorthSea oil platform and evaluated during ademonstration flight. Following evaluation,changes were made and a modified systemhas been installed, to be tested next winter.Status lights on helidecks have been a separateissue – a correct procedure to test these lightshas now been ascertained and changes to theCAA specification recommended.

Wind shear: Data analysis and wind-tunneltesting has allowed the wind-shear criterionin CAP 437 to be deleted, allowing lessrestriction on industry with science to supportthe safety of this decision.

Moving decks: Substantial analysis andmathematical research has produced landingcriteria for moving decks (e.g. small shipsoffshore) and prelirninary limits derived for somehelicopter types. An in-service trial is planned.

General aviation – Small helicopters:

inadvertent flight into IMC – A study intovisual cues and inadvertent entry to IMC hascontributed to changes in the Air NavigationOrder (ANO).

Small Aeroplanes: Carburettor icing (in

response to AAIB recommendations, e.g.

2004/01) – A mechanism to solve thisperennial problem was developed and testedon a ground rig. (It will now be tested on anaircraft to validate the laboratory data.)

Gyroplane design requirements – Acomputer model and flight trial of rotor teeterbehaviour has confirmed the benefits of achange to the gyroplane design requirements,which are still a UK CAA responsibility.

Regulatory activity – compliance support

There have been methods developed to helpdetermine whether UK service providerscomply with new standards from Europe.

Helideck lighting – before

Helideck lighting – after


20 focus spring 09

Risk based oversight – Current methodsused by flight operations inspectors toinformally adjust oversight according to askwere surveyed and documented. This formedan input to development of key performanceindicators for risk based oversight across allareas of safety oversight.

Occurrence reporting by ground handlers –

Ramp events can have serious safetyimplications, but very few ground handlersreport to the MOR scheme. Reporting is beingexplored and promoted.

Limited budget

Since industry funds this research through feesand charges, is it good value? The annualresearch budget is currently £600,000, aspublished in the CAA accounts. In addition, thereis a similar sum contributed between a range ofexternal bodies, including Oil & Gas UK, ShellAircraft, UKOOA (UK Offshore OperatorsAssociation), EPSRC (Engineering & PhysicalSciences Research Council), HSE (Health &Safety Executive), GAPAN, Transport CanadaCivil Aviation, Norway Civil Aviation Authorityand US Federal Aviation Administration.

While £600,000 is a significant sum, it mustbe put in context with other industryoperating costs such as IT projects,accommodation changes, fuel, cabinmodifications or the interest charges onfinance arrangements. In the aviationenvironment, a single diversion may cost£150,000 (including the sub leasedreplacement aeroplane and additional crew,passenger hotel bill, fuel and ground support),one FMGS data entry keypad for a simulatorcan cost £100,000, training for one pilot£60,000, a single baggage truck dent £50,000£160,000 (depending on where on the aircraftthe damage occurs). An accident that causesinjuries or a small drop in passengerconfidence frequently leads to lost revenueand a complete re-branding exercise for anairline that can run into many millions.

The manufacturing industry is supported bywidespread research in universities and airtraffic management research has fabulousbudgets from Europe (Single European Skiesresearch is funded at £47m for the definitionphase alone). The flight operations industryhas no such research infrastructure and the

majority of airlines do not conduct safetyresearch. Those that do may not necessarilyshare it with the industry as a whole (or itmay not be applicable) and there is no co-ordinated programme.

Yet flight operations is the ‘sharp end’ wheremost safety risks emerge and where any risksthat have entered the system at another stage– for example at the aircraft design stage – willbecome apparent and have to be addressed.While not all GA research is aimed at flightoperations, the operators do not pay all of theCAA funds either. UK operators share thebenefits of CAA flight operations research. Theprice is equivalent to one diversion plus oneoccurrence of ramp damage that hit anexpensive part of the aircraft, shared betweenall UK AOC holders. Benefits include moreoperational flexibility and less accident risk. Itcould be argued that this is quite good value.

Conclusion

Research for UK CAA still has a useful role toplay, alongside EASA. While safety levels arehigh, it is easy to forget that this good safetyrecord has been achieved through continuouswork from many sources including CAA. Forall of these reasons the CAA conductsresearch that is systematic and focused andprovides a worthwhile contribution to safeaviation. Your comments would be mostwelcome to [email protected].

*Dr Hazel Courteney, FRAeS, is head of research

& strategic analysis at the UK CAA. She worked

in aircraft design and manufacture for 12 years

before joining CAA in 1994 to work in type

certification, particularly crew related issues,

and chairs the CAA Accident Analysis Group.


21focus spring 09

Avoiding the Conflict

It would seem strange to an outsider that

ANSPs spend an enormous amount of

time and resources on selecting and

training professionals to separate aircraft,

only to have increasing numbers of

incidents which involve short-term

conflict alert (STCA) and TCAS

intervention. This is not unique to Europe

and it is almost impossible to calculate

how many conflicts are not resolved in a

timely manner, but the estimate is

somewhere in the region of 10 for every

100,000 movements. This is exactly why

the air traffic control system finds it so

difficult to implement further safety

strategies and often struggles to find the

balance between safety and service. If

controllers got it wrong more often we

would be in a better position to implement

more robust safety nets. But why do

controllers get it wrong at all? The answer

in some part lies in the often difficult

balance between conflict resolution and

conflict avoidance. Conflict resolution,

which is the most obvious skill of

controllers, is demonstrated when

measures are taken in order to prevent the

further development of a conflict

situation. Conflict avoidance, is used to

prevent the situation in the first place by

using pro-active control actions such as

heading or level assignments.

When analysing these two strategies it is easyto recognise how complex avoiding theconflict can be. Conflict resolution can bedescribed simply as a three-stage activity,although at each stage there are severalthings that may go wrong.

Conflict resolution firstly relies on detection,which means the controller must know whatto look at and for, when to look and actively

‘see’ what is being searched. Here we have thefirst problem, since incident statisticsdemonstrate that one of the highest numberof errors in ATC incidents is to ‘not see’ theinformation at all. There are many reasons forthis: firstly if the technology does not displaythe relevant information in an intuitive way,controllers may fail to scan the most relevantdata. Secondly, controllers may fail torecognise the important information.

If the relevant information is detected thecontroller then needs to recognise it as aproblem or risk. The main problem with theseactivities for experienced controllers is theissue of time; often requiring tasks to beprioritised. High workload also increases therisk of reacting to situations instead ofanticipating them.

The existence of conflict resolution tools, suchas STCA and medium-term conflict alert(MTCA), also invite controllers to not activelyscan for conflicts but depend on the tools towarn them; which must be avoided.

Conflict avoidance, on the other hand, ispotentially a more robust technique, howeverit does require the controller to controldefensively and pro-actively; that is set up thetraffic in such a way that should a plan fail,separation would be maintained. Thistechnique is illustrated in the following figure.

Comparing this with the conflict resolutionmodel, it can be seen that controllers wouldbe expected to invest more time inmonitoring the situation, which of coursemeans a trade-off with other activities or insome cases deferring other activities until the

original task is complete. However if a clearset of roles and responsibilities are given andpracticed by the controlling team, theinvestment would ultimately mean less riskyand more pro active controlling.

One challenging factor is the year on yearincrease of traffic. It is not surprising that thisincrease in demand decreases the possibilitiesof using conflict avoidance techniques.Another area that hampers the use of conflictavoidance is the complexity of airspace, oneof the leading contextual factors in ATMincidents. This is a highly challenging area totackle and demands highly collaborativedecision-making, learned over a lengthyperiod of time.

So what do we know about conflict resolutionat the moment? Recent work with regard toSTCA has revealed some interesting trends,although how robust these are and how theycan be generalised is too early yet to assess.The analysis of STCA alerts requires the lateraland vertical geometries to be defined. Thelateral geometry in this work is based on therelative heading of two aircraft; the alert isthen classified as head on, crossing or catchup as the following diagram indicates.

The vertical geometry is based on the altitudechange over the last 5 radar cycles before analert. The geometry of each aircraft is thenclassified as climbing, descending or level.

In terms of the lateral geometries of the alertsstudied, 55% were crossing, 22% were catchup and 23% were head on.

by Anne Isaac and Vicky Brooks of NATS


22 focus spring 09

In terms of the vertical geometries of thealerts; 65% of encounters are where oneaircraft is level and the other is either climbingor descending.

Combining the lateral and vertical geometries ofthe alerts shows that approximately 80% ofcrossing encounters involve one or both aircraftthat were climbing or descending. The followingfigure illustrates the findings of these geometries.

The version of STCA used in this study uses atwo-stage alert, changing from white (lowseverity) to red (high severity). It is assumedthat in the first stage of the alert, white,controllers will acknowledge the alert and actto resolve the potential conflict as required;indeed 97% of alerts that were white,remained white until they were resolved. Asmall percentage of alerts went straight to red,which meant there was little pre-warning,possibly the result of a ‘pop-up’, for example,either a fast moving military encounter, anencounter with a sudden change in lateral orvertical geometry, or an airspace infringement.And the remainder of the alerts began whitebefore becoming red.

It is difficult to make any substantial claimsfrom one set of data, but further analysis willadd to the understanding about whatcontrollers do, particularly when the alertgoes white and what, if anything, changestheir strategy when the alert becomes red.

If we return to the original discussion ofconflict resolution versus conflict avoidance, itwould seem that developing techniques toallow controllers to exploit conflict avoidancestrategies within their time constraints would

be a more pro-active approach to ATM safety.How we do this of course is another story –watch this space!

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23focus spring 09

Wake Turbulence – Progress at Lastby David Booth, Eurocontrol

Wake vortices are generated by all

aircraft in flight. Their generation

begins when the nose wheel lifts off the

runway on take off and ends when the nose

wheel touches down again on landing.

These vortices are in the form of two

counter-rotating air masses trailing behind

the aircraft. The vortices generally sink and

when they are close to the ground tend to

move outwards from the track of the

aircraft. Vortex strength increases with

weight and therefore is at its greatest when

generated by heavy aircraft.

While the term wake vortex describes thenature of the air masses, the term waketurbulence is used to describe the effect of themasses. Because wake turbulence is invisibleand its presence and location are dependanton a number of factors (e.g. wind speed anddirection, proximity to the ground etc.), it isdifficult to determine precisely where they are.It is for this reason that ICAO introduced waketurbulence separations in the 1970s.

When these separations were introducedaircraft were categorised solely on weight andexpert opinion at the time. Although theseparation requirements were adequate at thetime they were introduced, over the yearsmany changes and modifications to the originalcriteria have been made – in Europe alone thereat least 15 variations! Since their introduction ahuge amount of research has been carried outin the study of wake vortex. This research hasshown that factors other than aircraft weight(e.g. wingspan, wing loading, speed etc.) needto be taken into account when determininginto which category aircraft are placed. Thisincreased knowledge has increased our abilityto effectively model and predict the behavioursof vortices. However, no changes would ever bepossible until real time data could be obtainedto supplement the output from models and toprove beyond any doubt that the vortex wakeis behaving precisely as predicted. Thecollection of this real time data is now, at last,possible due to the availability of advancedmeasuring equipment such as LIDAR. At last,after many years, the present criteria can beupdated and new procedures that take accountof the effects of strong winds on vortex wakecan be developed.

The recent introduction of the Airbus A380into operational service demonstrates this very

well. For the first time the wake turbulenceseparations were defined prior to an aircraftentering service and for the first time theywere defined using scientific analysis. Aninteresting spin off from this project, using thisnew measuring technology was the discoverythat on many occasions when aircraft hadbeen carefully separated by the air trafficcontrollers, the vortex wake generated by thelead aircraft simply was not there – it hadeither been blown away from the flight path ofthe following aircraft or more often it haddecayed to virtually zero strength.

This has clearly demonstrated that furtherchanges to wake turbulence separations will bepossible in certain circumstances. EUROCONTROLhas identified four areas of interest:

■ The need to apply wake turbulenceseparations between aircraft operatingfrom closely spaced parallel runways(CSPR)

■ The application of wake turbulenceseparations in crosswind conditions

■ The development of a time based finalapproach separation procedure (TBS)


24 focus spring 09

■ Updating the present ICAO aircraft waketurbulence categories into a single globallyaccepted set of categories (RECAT)

In order to build on the common interest inthese concepts, to avoid any duplication ofeffort and to facilitate the approach to ICAOfor rule changes, EUROCONTROL are co-operating very closely with the FAA. Togetherthey have established a common Wake Vortex(WV) Coordination Group to oversee thedevelopment of these concepts.Representatives of all sectors of the aviationcommunity have been invited to participateand to contribute to the work.

Closely Spaced Parallel Runways (CSPR)

In today’s operations, parallel runways spacedless than 760m apart are classed as dependantin terms of wake turbulence. The CSPR projectaims to introduce procedures to reduce oreliminate this dependency. It will do this bydemonstrating;

1) That in certain crosswind situations thevortices generated by an aircraft on onerunway are transported away from the otherrunway.

2) In a zero wind or headwind situationvortices are either not transported from one runway to the other or are of sufficiently low

strength not to be a factor – and by lowstrength it is meant considerably less strengththat those vortices that are routinelyencountered when flying directly behindaircraft on final approach today.

This project is currently being developed atParis, Charles de Gaulle airport and the firstphase of implementation took place inNovember 2008.

While addressing the particular case of Paris,CDG airport, the work will be of benefit to otherairports with closely spaced parallel runways inEurope – and generic procedures will bedeveloped that can be adapted to those otherairports. At the same time the data and analysiswill be used to expedite the development ofsingle runway crosswind procedures.

Because the CSPR procedures are not weatherdependant they will offer an increase incapacity to already constrained airports.

Crosswind Procedures

This project is weather dependant andtherefore cannot claim to increase capacity;however it is seen as one possible solution toreduce delays at airports. It is investigating thepossibilities of safe conditional reduction ofwake turbulence separation minima betweensuccessive arrivals or departures.

Recent research has shown that a crosswind ofas little as 7 knots will transport any wakevortex away from a runway. Therefore, if thereis no wake turbulence then there is norequirement for wake turbulence separation.This would then allow the possibility ofsuspension of the 2 minutes wake turbulencerunway separation when Medium and Lightaircraft depart behind Heavy. For arrivingaircraft ATC would only need to provide radarseparation.

Time Based Separation (TBS)

The objective of this project is to validate aconcept substituting distance based separationwith minima based on time leading to arecovery of some of the runway capacity lostduring periods of strong headwinds. The factthat controllers still need to apply standardwake turbulence separations in these strongheadwind conditions is one of the biggestcauses of delay in Europe. In terms of applyingthis concept, controllers use marker lines thatare generated and displayed on the radarscreens. EUROCONTROL have alreadyconducted a real time simulation at theirexperimental facility involving controllers fromGermany. The result of that simulationdemonstrated that the TBS concept is viable,was easily understood and applied by controllersand, in strong wind conditions, TBS operationsrecovers most of the lost runway throughput.


25focus spring 09

Re-categorisation of the ICAO Wake

Turbulence Categories (RECAT)

Concerns over the viability of the existing ICAOwake turbulence separation criteria have ledmany Civil Aviation Authorities around theworld to introduce modifications to thescheme. These local variations are not co-ordinated and have significant implications forboth safety and capacity. In the light of theseconsiderations it is now apparent that thecurrent ICAO Wake Turbulence categories areoutdated and a major update is needed. TheRECAT project is being conducted in close co-operation with the FAA. The objective is simplyto produce a globally accepted set of criteriathat take account of all relevant factors. Ifsuccessful this criteria will be adopted by ICAO.

Other Issues?

While the four projects mentioned above formthe basis of the current EUROCONTROL workin wake turbulence there are other areas thatwe need to, and indeed our stakeholders areinsisting that we address.

One of the most important of these areas isthe question “What is a safe encounter?” Atthe present time opinion on this subject variesgreatly and, in truth, there appears to be littleconsensus on the matter. We know thataircraft are experiencing encounters today butmany are considered by aircrew to be “justmild turbulence” or “a bit bumpy”. Even someof the more serious encounters go unreportedbecause the situation has been controlledswiftly and professionally by the crew.

In the future it could be argued that anacceptable encounter would be one whichwould be no worse than that experienced byaircraft following a B747-400 using today’sICAO wake turbulence separations.

However, in order to investigate this subjectmore we will require pilots to file waketurbulence encounter reports. Currently thereis an ICAO Wake Encounter Report Form andthe UK’s Safety Regulation Group hasdeveloped its own version which is morecomprehensive. Whilst it is appreciated thatpilots are very busy and would prefer to avoidtime spent filling forms the information

contained in them is vital to the ongoingresearch into wake turbulence.

Other areas of concern are:

■ en-route wake turbulence separations.Currently ICAO provides no guidance inthis area.

■ The separations needed for Very Light Jets(VLJs)

■ Helicopters

These areas will be developed as part of alonger term work plan.

Finally let us reiterate that we are now in aposition where revisions to the current ICAOwake turbulence separations can and will bemade in the short term. These will beimplemented with the development of newpractices and procedures, the results of whichwill be developed and implemented within thenext three years.


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