SAFETY OF THE RUNWAY OPERATIONS WITH A TEMPORARY DISPLACED THRESHOLD

DURING CONSTRUCTION WORKS

November 15, 2013

6,823 words

Gaël LE BRIS

Airside Development Manager, Aeroports de Paris S.A.

Batiment 7300, Zone Technique, BP81007, 95931 Roissy-Charles de Gaulle Cedex +33(0)786-298-433 (phone)

gael.lebris@adp.fr (e-mail)

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Abstract 1 2 Temporary displaced thresholds have been subjected to a growing interest from airport operators facing 3 capacity challenges and high expectations from their customers in terms of operational reliability. This concept 4 minimizes the impact of the construction works on the traffic, because it avoids a closure of the runway to 5 complete them. However, accident and incident records between 1997 and 2013 demonstrate major to 6 catastrophic occurrences, for a significant part of the set of constructions works of this period. Consequently, 7 the design of a shortened runway and of the adjacent construction project must include proper provisions for 8 guarantying the safety of the flights and of the working staff. The analysis of recent projects and the related 9 accidents reveal generic hazards and risks. It suggests innovative measures of risk mitigation and risk assurance, 10 including some that have recently been tried with success by airports. However, a risk management plan has to 11 consider local specificities. Consequently, the safety of temporary displaced thresholds calls for a pragmatic 12 and comprehensive risk management approach, and for the sharing of the experience between the players of the 13 airport industry. 14

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INTRODUCTION 1 The temporary displacement of a threshold for construction works is a sensitive modification, because it 2 modifies the existing operating conditions and introduces complexity. Also it can easily generate accidents if 3 all the related safety issues are not carefully addressed. Nevertheless, this type of change is not rare. Only 4 during the first seven months of 2013, at least five displaced threshold (DTHR) were put in place at 5 international airports around the world. Growing aviation traffic, and higher expectations from the passengers 6 and airlines in terms of operational robustness, should increase the interest for the temporary displaced 7 thresholds in order to limit the impact of runway works on the throughput. 8 An inventory, even partial, of the accidents on shortened runways demonstrates that significant safety 9 events occur under this configuration (table 2). In 1997 at Vienna International Airport, nine aircraft landed 10 before the displaced threshold. In 2005 at Perth Airport, and in 2009 at Chhatrapati Shivaji (Mumbai) 11 International Airport, each time, a flight was closed to land on the construction works themselves. In 2011 at 12 Vnukovo International Airport, two serious accidents occurred during the period a threshold was displaced. 13 Consequently, the criticality of such a configuration of a runway requests a careful assessment of the 14 risks and an adequate mitigation plan. All construction projects are different. Each one needs a safety risk 15 analysis taking into account the specificities of the airport, and these of its traffic profile. However, it is 16 possible to define a common typology of the hazards and risks for the most severe of them, and to identify the 17 best practices for risk mitigation. 18 19 METHODOLOGY AND SETS OF DATA 20 Seventeen construction projects from 1997 to 2013 with displaced thresholds at airports accommodating a 21 commercial traffic were compared (table 1). Within this set, ten took place in Europe, two in North America, 22 one in the Caribbean (French Overseas Territory), one in the CIS (Community of the Independent States), and 23 two in the Asia-Pacific region (Australia). 24 25 TABLE 1 Inventory of the set of displaced thresholds 26

Airport Name ICAO

Code Period DTHR Main Operations Restrictions

Point-à-Pitre TFFR April 2013-June 2013* 12 Mobile THR12.

Roma Fiumicino LIRF 02/16/2013-06/30/2013* 25 RWY25: only T/O. No LVTO.

Belfast Intl. EGAA 02/18/2013-02/06/2013 07 –

Milano Linate LIML 06/03/2013-09/30/2013* 36 –

Prague V. Havel LKPR 05/15/2013-09/30/1013 12 –

San Francisco KSFO 06/14/2012-09/07/2012 10R –

Paris-CDG LFPG April 2012-June 2012 08L No H T/O RWY26R. No LVTO.

Bâle-Mulhouse LFSB 03/05/2011-09/07/2011 33 ILS RWY33 not available.

Vnukovo UUWW 2011 01 No PAPI and no ILS on RWY01.

Chicago O'Hare KORD 2009 14R –

Paris-Orly LFPO 2009 08 Only T/O from RWY08.

Mumbai Intl. VABB 2009 27 –

Paris-CDG LFPG 2008 09R No ILS on RWY09R.

Perth YPPH 2008 21 No ILS on RWY21.

Metz-Nancy LFJL 2006 04 –

Perth YPPH 2005 21 No ILS on RWY21. Vienna Intl. LOWW 1997 11 and 29 –

* Only a limited phase during this period. – Missing data. 27 THR Threshold. DTHR Displaced threshold. T/O Takeoff. LVTO Low Visibility Take-Off. 28

29 The analysis took benefit from the risk-based Safety Risk Analysis (SRA) of Threshold 08 30

Reconstruction Program Phase 2 of Paris-CDG (2012), during which Threshold 08L was displaced by 31 approximately 700 m (2,297 ft) eastward (figure 1). This safety study was conducted according to the 32

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principles of the Safety Risk Management (SRM) (1), mandatory in France since 2007 as part of an airport 1 Safety Management System (SMS). 2

3

4 In order to conduct a complementary event-based approach and introduce new hazards in the study, 5

Accidents and incidents on shortened runways (table 2) and other major to catastrophic events (table 3) were 6 searched through a record of exogenous events used at Paris-CDG for the Safety Risk Analysis. This record is 7 filled with airport-related accidents and incidents extracted from a selection of online databases. The primary 8 sources are FAA' Aviation Safety Information Analysis and Sharing (ASIAS), Transport Canada' Civil 9 Aviation Daily Occurrence Report System (CADORS), and regular official accident digests, notably from the 10 French BEA. 11 12 TABLE 2 List of accidents and incidents on shortened runways 13

Date ICAO

Code

ACFT Description

07/04/2012 LKPR A319 Takeoff RWY12 without taking into account the reduced TORA.

2012 LFPG – At least 3 entries on the shortened runway by closed access taxiways.

06/05/2011 UUWW A333 Landing RWY01 below the descent plan. Collision with jet blast fences.

05/14/2011 UUWW YK42 Landing RWY01. Longitudinal runway excursion.

11/10/2009 VABB AT72 Landing RWY27A. Longitudinal excursion on wet runway.

11/03/2009 VABB A322 Two successive interrupted approaches before the shortened RWY27A.

2009 KORD – 2 aircraft overran beyond the end of the RWY.

2009 KORD – Touch & go on the closed portion.

2009 KORD – 2 takeoffs of HEAVY ACFT without knowing the existence of the DTHR.

08/16/2008 LFPG B738 Takeoff RWY27L without taking into account the reduced TORA.

05/09/2008 YPPH B738 Two interrupted approaches on the usual threshold on a shortened RWY.

04/24/2005 YPPH A342 Landing short before the displaced threshold.

1997 LOWW – 9 landings before the displaced thresholds.

1997 LOWW B747 Too long takeoff. Blast fences cleared by 5m.

THR Threshold. DTHR Displaced Threshold. 14 15 TABLE 3 Other major to catastrophic runway accidents 16

Date ICAO

Code

ACFT Description

04/09/2011 LEMH CRJ2 Landing on the parallel runway closed for maintenance.

05/25/2008 EBBR B742 Rejected T/O 12 kt after V1. Longitudinal veer-off.

01/17/2008 EGLL B772 Undershoot before Threshold 27L.

08/27/2006 KLEX CRJ1 Crash after a confusion btw the short and the long RWY.

08/02/2005 CYYZ A343 Landing then overrun on a contaminated runway after enduring

windshears.

11/05/2000 LFPG B74F Accelerate-stop after V1 on RWY27L then runway excursion.

10/31/2000 RCTP B744 Takeoff from a parallel TWY/RWY in maintenance.

09/05/2000 LFPG B742 Landing then lateral excursion beyond the CAT I protections.

FIGURE 1 Threshold 08 Reconstruction Program (Phase 2) at Paris-CDG, 2012

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REASONS FOR IMPLEMENTING A TEMPORARY DISPLACED THRESHOLD 1 The situations involving a displaced threshold on a runway are the refurbishments (Linate, 2013) or the 2 developments (Paris-CDG, 2012) of adjacent taxiways, the phased runway resurfacings (Point-à-Pitre, 2013), 3 and the resurfacings of the common section of a crossing runway (Prague, 2013). All of these operations 4 include necessarily constructions within the border of the runway strip, and directly onto the runway at least for 5 a part. The alternative solutions to a displaced threshold are the completion of the works during the lowest 6 traffic period of the day (usually a few hours by night), or the closure of the runway during the entire works. 7

Performing the works by night is not compatible with certain construction technics which do not accept 8 to be interrupted, especially pouring concrete. Indeed, if the resurfacing of runways in asphalt can be entirely 9 phased by night (Frankfurt-Main, 2003-2007) or during extended week-ends (Paris-CDG, 2012 and 2013), the 10 proper reconstruction of large surfaces of concrete panels require time for guarantying a correct quality of 11 realization and a proper drying, for avoiding early damages. 12

The permanent closure is an answer to these technical needs. Nonetheless, it impacts the operations, 13 constraining significantly the ability of the runways system of accommodating the ordinary daily throughput. 14 One-runway airports are naturally the most impacted in case of prolonged closure. For multi-runway airports, 15 the consequences would be different depending on their connectivity. Highly connected airports, welcoming an 16 airline working within hub-and-spoke rules, sized their facilities in order to expedite dense traffic peak hours. 17 The large amount of arrivals and departures is not compatible with a lengthy runway closure, because it would 18 degrade the punctuality and the gathering of the connected flights, which is the key issue for such an 19 organization of the daily flight program. A displaced threshold is a way to protect the operational robustness, 20 because it reduces the consequences of the unavailability of another runway. 21

Runway closures are less critical at point-to-point airports, if the runway system is not constrained by 22 Air Traffic Flow Management (ATFM) restrictions. Indeed, it is usually tolerable that some flights are 23 moderately spread out during the peak periods. However, this apparent flexibility for point-to-point airports is 24 subjected to the Air Traffic Control (ATC) procedures and local noise mitigation measures. For instance, Paris-25 Orly has three runways, but two of them accommodate more than 99% of the movements. On each one of these 26 two runways, only one direction is operated most of the time, alternatively for the takeoffs and landings. So, 27 one runway cannot be used in mixed mode. Similar restrictions exist at many other airports. 28

Multi-airports systems owned or conceded to the same operator offer also an opportunity for 29 implementing limited continuous closures, because the traffic from the closed airport can be diverted to the 30 others of the metropolitan area, if their capacity allows it. 31

Whatever the runway system and the mitigation measures for limiting the impact on the traffic, a 32 prolonged continuous runway closure degrades significantly the airport capacity. The drop of capacity depends 33 mainly on the configuration of the runway system, the equipment of these runways, their operating conditions, 34 and the traffic profile (mix index) (2). For airports which cannot accept restrictions of their capacity, the 35 displaced threshold is a tool for mitigating the impacts of the works on the aviation operations. 36 37 REDUCED AVAILABLE DISTANCES 38 The length of runway made inoperative by a displaced thresholds balance the needs of the construction project, 39 and the requirements of the usual aircraft serving the airport. The reduction of the TORA (Takeoff Runway 40 Available for the acceleration of the aircraft) can leave only two thirds of the initial available runway length 41 (Vnukovo, 2011), until even less than a half (Vienna, 1997). The choice of the remaining lengths available has 42 to take into account the capacity of the other runways (if applicable) with their operating restrictions, and the 43 performances of the aircraft types using the airport at their weights for flying their usual destinations. For 44 instance, at the sea level and Std+15°C (typically 30°C or 86°F), a Boeing 737-800 NG requires 2,743 m 45 (9,000 ft) to takeoff at its MTOW (Maximum Takeoff Weight) and 1,650 m (5,410 ft) to land at its MLW 46 (Maximum Landing Weight) (3). A Boeing 777-300ER needs 3,200 m (10,499 ft) to takeoff at the MTOW, and 47 2,175 m (7,136 ft) to land at the MLW (4). 48

Beyond the accommodation of the desired fleet, the length of the shortened runway should take into 49 account the increase of the likelihood of excursion, based for instance on a probabilistic study or the 50 transposition of a selection of critical occurrences. 51

52

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TABLE 4 Takeoff runways available with temporary displaced threshold 1

Airport Name ICAO

Code Year DTHR Full TORA Reduced TORA

Point-à-Pitre TFFR 2013 12 3,129 m (10,226 ft) Variable

Roma Fiumicino LIRF 2013 25 3,309 m (10,856 ft) 2,485 m (8,153 ft)

Belfast Intl. EGAA 2013 07 2,780 m (9,121 ft) 2,070 m then 1,770 m

Milano Linate LIML 2013 36 2,442 m (8,012 ft) 2,403 m (7,884 ft)

Prague V. Havel LKPR 2013 12 3,250 m (10,663 ft) 2,950 m (9,678 ft)

San Francisco KSFO 2012 10R 3,469 m (11,381 ft) 2,835 m (9,300 ft)

Paris-CDG LFPG 2012 08L 4,215 m (13,829 ft) 3,480 m (11,417 ft)

Bâle-Mulhouse LFSB 2011 33 3,900 m (12,795 ft) 2,310 m (7,579 ft)

Vnukovo UUWW 2011 01 3,060 m (10,039 ft) 2,030 m (6,660 ft)

Chicago O'Hare KORD 2009 14R 2,952 m (9,685 ft) 1,824 m (5,985 ft)

Paris-Orly LFPO 2009 08 3,320 m (10,892 ft) 2,790 m (9,154 ft)

Mumbai Intl. VABB 2009 27 3,448 m (11,312 ft) 1,703 m (5,587 ft)

Paris-CDG LFPG 2008 09R 3,970 m (13,025 ft) 2,960 m (9,771 ft)

Perth YPPH 2008 21 3,444 m (11,299 ft) 2,652 m (8,701 ft)

Perth YPPH 2006 21 3,444 m (11,299 ft) 2,113 m (6,932 ft)

Metz-Nancy LFJL 2005 04 3,050 m (10,007 ft) 2,100 m (6,890 ft)

Vienna Intl. LOWW 1997 11 and 29 3,037 m (9,964 ft) 1,360 m (4,462 ft)

2 FLIGHT PROCEDURES AND NAVAIDS 3 A temporary displaced threshold implies the unavailability of at least the Glide Path of the Instrument Landing 4 System (ILS) of the concerned threshold, if existing. A temporary Glide Path (GP) would be unreasonably 5 expensive (>100,000 USD). Consequently, instrument procedures, including Low Visibility Take-Off (LVTO), 6 have to be suspended (Point-à-Pitre, 2013) or modified (Paris-CDG, 2012). A PAPI (Precision Approach Path 7 Indicator) is more affordable (>10,000 USD) and provides in Visual Meteorological Conditions (VMC) an 8 indication on the position of the approach path to the crew. At Paris-CDG, on RWY08L/26R, both thresholds 9 are equipped with CATI/III ILS. So, when Threshold 08L was displaced during two months in 2012, a 10 temporary PAPI was created and a LOC-DME approach procedure replaced the usual ILS procedures. 11

However, the opportunity of a displaced threshold, and the choice of the remaining navigation aids 12 (NAVAIDS) and procedures, should be based on the average weather conditions during the period of the 13 construction works. A contingency plan should be determined in case of unusual adverse conditions. For 14 instance, if Low Visibility Procedures (LVP) can occur during the constructions, and if these make inoperative 15 the complete ILS, a plan for diverting the entire traffic should be prepared. 16 17 HAZARDS AND RISK ANALYSIS 18 19 Approach or landing before the displaced threshold 20 An interrupted approach or a landing before the displaced threshold, because of a misidentification of the 21 operative threshold, is a risk of collision with works or unsuitable surfaces. In Vienna in 1997, nine flights 22 landed short before the displaced threshold. Short landings, touch and go as well as missed approaches on the 23 initial threshold also occurred in Perth in 2005 and 2008, at Chicago O'Hare in 2009, and in Mumbai in 2009. 24

In the case of Perth of 2005, despite a temporary PAPI, the crew was unable to locate precisely the 25 displaced threshold (5). In another accident which occurred three years later, a 737-800 was closed to land and 26 then performed a go-around two successive times on the initial threshold. The aircraft correctly landed the third 27 time. According to the investigation report (6), a PAPI was provided for the correct identification of the 28 location of the aiming points, but the closed section was not correctly marked: the painted crosses closing the 29 first 800 m (2,625 ft) were 6 m-long (20 in) instead of 36 m (120 in) as recommended by the ICAO (7) as the 30 FAA (8). Indeed, crosses for closing a taxiway were used instead of the standard markings for runway closure. 31 Furthermore, when a threshold is displaced during less than five days, the Australian regulation tolerates the 32 displaced threshold markings are simplified as two pairs of white chevrons on each side of the beginning of the 33 Landing Distance Available (LDA) (9). 34

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At Point-à-Pitre in 2013, an original solution emerged for differentiating the initial and the displaced 1 thresholds. Due to the organization of the construction works and the flight program, the threshold was 2 displaced only during seventeen nights. A variable length configuration was chosen. Two thresholds were 3 visible: the initial remained white, and the displaced one was painted in blue. 4 5 Landing below the approach path of the displaced threshold 6 If the instrument approach procedures are suspended, the pilots have limited instrument or visual guidance for 7 maintaining the right approach path. The critical risks of a non-compliant trajectory are a destructive collision 8 with an obstacle from the constructions before touching down, or a short landing with the consequences 9 discussed before. 10

At Vnukovo Airport in 2011, an Airbus A330-300 landed too low, and its main gear touched the fences 11 protecting the construction works against jet blast. The weather conditions were excellent. In absence of 12 instruments aids, a temporary PAPI would give to the crew an indication for keeping the correct approach path. 13

An alternative is the simple removal of the hazard by the suspension of the landings flying over the 14 closed part of the runway. This solution was retained in 2008 at Paris-Orly on RWY08, and in 2012 at Paris-15 CDG on RWY08L/26R, which are runways preferentially used for takeoff. 16 17 High speed collision during a takeoff toward the construction works 18 A takeoff without taking account the reduced distances in determining the takeoff speeds (or V-speeds) could 19 make the aircraft in a collision trajectory with obstacles beyond the end of the safety margins of the shortened 20 runway. Many occurrences happened on the considered period. At Vienna in 1997, a 747 took off too long and 21 cleared blast fences by 5 meters (10). At Paris-CDG in 2008, a 737-800 took off long, hurt plastic separators 22 without sustaining critical damages, and then flew low over the blast fences (11). At Chicago O'Hare in 2009, 23 two wide-bodies took off without being aware of the declared distances in effect. At Prague V. Havel in 2012, 24 an Airbus A320 aligned and started to accelerate with takeoff speeds calculated on the basis of full runway 25 lengths. The crew realized its mistake when they saw the construction works appearing beyond the end of the 26 available runway (12). 27 A collision between aircraft and the vehicles or excavations would be catastrophic, as demonstrated by 28 the accident of Taipei in October 2000, when an aircraft aligned and accelerated on a runway closed for 29 maintenance, before being destroyed by the shock with the machines. 30 These events occurred on airports where the shortened runway and the aeronautical information 31 associated with its modification were compliant to the regulation requirements. When the constructions are not 32 directly on the runway, the likelihood of a collision dramatically decreases if there is no obstacle (especially 33 blast fences) on the runway itself, even on the closed section (Paris-CDG, 2012). However, this is not possible 34 when the purpose of the works is the refurbishment of the runway pavement. Banning the aircraft requiring the 35 longest distances, for taking off as performing an accelerate-stop, reduces also the likelihood of the risk of a 36 collision (Paris-CDG, 2012). Only the suspension of all operations facing the works removes the hazard (Paris-37 Orly, 2009). 38 39 Veer-off toward the construction works 40 For the takeoffs facing the constructions, another critical hazard is an accelerate-stop after V1, which is the 41 maximum speed authorized for performing a safe a Rejected Takeoff (RTO) in case of engine failure. For the 42 landings, the main hazards are a longitudinal veer-off (Toronto, 2005), and a landing beyond the temporary 43 runway end (O'Hare, 2009), with the infringement of the working perimeter. 44

The basic for mitigating the consequence of an overrun is to preserve the runway strip and a Runway 45 (End) Safety Area. The choice of the maximum RSA (350 m or 1,000 ft for a U.S. RSA beyond the runway end, 46 240 m or 787 ft for an ICAO RESA from the end of the runway strip) is relevant, since the consequences in 47 case of further excursions is potentially higher than usual. However, the 300 m-long (307 ft) overruns of an 48 Airbus A330-200 landing at Toronto Pearson in 2005 (13), and of a Boeing 747-200 Freighter performing an 49 accelerate-stop after V1 at Brussels National in 2008 (14), showed that a veer-off can end largely beyond the 50 limits of the RSA. This would be particularly true after the temporary end of a runway with a displaced 51 threshold, because this closed section is probably still paved and will not arrest the plane like a RSA in turf. 52 The lateral dimensions of a RSA are also challenged by some exceptional occurrences, like the excursion 53

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beyond the Instrument Landing System (ILS) Category I runway protections of a Boeing 747-200 Combi at 1 Paris-CDG in 2000 (15). 2

The provisions previously observed for preventing an accident during a takeoff contribute to the 3 mitigation of the consequences of a veer-off. In addition, at Paris-CDG in 2012, a supplementary safety area on 4 each side of the closed section would be evacuated by the construction works if a recovery of the capacity of 5 accommodating landings on this runway would be required due to the closure of another runway. Its 6 dimensions were based on a record of exceptional veer-offs, and was approximately those of the ILS CAT I 7 sensitive area. 8 9 Risks on the operations back to the constructions 10 For the landings back to the works, the cases of undershoots were considered above. The preservation of a RSA 11 at the end of the shortened runway contributes also to mitigate the effect of a short landing. The reduction of 12 the runway length increases the probability of excursion after the end of the runway, especially when it is 13 contaminated. If snow and ice are not usual contaminants of temporary shortened runway, because the 14 constructions avoid periods of adverse conditions and cold weather, heavy rain are still possible. In 2009 at 15 Mumbai Intl, an ATR-72 overran on a wet shortened runway (16). 16

New tools can help the safety risk managers to address this risk. For instance, the ACRP sponsored the 17 development of a tool so-called RSARA for assessing the probability of veer-off beyond the runway end, with 18 the local traffic and safety objective as inputs (17). Moreover, pilots' behavior face to overrun precursors should 19 evolve within the next decade. The TALPA workgroup, sponsored by the FAA, issued recommendations for 20 providing a matrix for correcting the required runway length based on the last information provided by the 21 ATCT about the runway condition. Also, aircraft manufacturers are developing on-board systems for helping 22 the pilots to detect the landing conditions in which an excursion could occur, and then decided to perform a go-23 around (notably Airbus' ROPS and Boeing's SAAFER). 24 25 AWARNESS AND INFORMATION OF THE PILOTS 26 27 Aeronautical information 28 The displacement of the threshold is basically announced by a NOTAM (Notice-To-Airmen), or an AIP 29 supplement activated by a "Trigger" NOTAM, in compliance with Annex 15 (18). The aeronautical 30 information mainly details the reduced declared distances, and the available NAVAIDS and procedures. For a 31 publication only by NOTAM, the description of the entire modification of the operating conditions takes 32 usually more than a dozen of lines. The number of NOTAMS to be read by crews is significant and in constant 33 growing (19). On long-haul flights, more than a thousand of notices can be applicable depending of the 34 countries and airspaces crossed. Another risk of NOTAMS is that a late publication will not be included by the 35 private providers of aeronautical information into their products. 36

AIP supplements have been used for significant temporary modifications in order to add more text, and 37 for adding modified aerodrome chart and ground movements' charts. Because of the standard notice prior 38 publication, an AIP supplement is diffused from two weeks (non-AIRAC activation) to six weeks (AIRAC 39 cycle) before being in force. 40 In order to reinforce the awareness of the aviation community, innovative solutions are locally found in 41 complement to the official aeronautical information. In the United States, the Federal Aviation Administration 42 sponsors illustrated construction works notices (20). These are available on the website (21) of the National 43 Flight Data Center (NFDC). All the temporary simultaneous modifications of the airside announced by a 44 NOTAM and longer than a day are represented on an aerodrome chart, updated on a daily basis during the 45 week. Other initiatives exist as letters to the airlines' station managers, community briefings, etc. 46

However, despite the efforts of the airport operators and the ATCT for communicating even beyond 47 the mandatory actions, inspections (22) and accident records show that they are not a guarantee of reception of 48 information by all the crews. In the accident of Paris-CDG in 2008, the crew was not aware of the AIP 49 supplement and the Trigger NOTAM describing the shortened runway. In the accident of 2012 in Prague, the 50 captain determined the V-speeds based on the full runway lengths. It identified the fatigue and a low awareness 51 as the main factor of their error. These results force the safety risk managers to consider the possibility of the 52

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most critical event possible. He has to include provisions in the design of the shortened runway for mitigating 1 their severity. 2 3 Visual information and real-time actions 4 Airports found innovative visual solutions for increasing the awareness of the pilots. At Mumbai Intl in 2009, 5 the shortened RWY27 and the associated procedures were designated 27A. At Paris-CDG in 2012, the only 6 access taxiway remaining open to accede to RWY26R, facing the construction works and the displaced 7 threshold was named R1 "WORKS" (figure 1). An unusual suffix focuses the attention of the pilot on the fact 8 that something could be modified in the operating conditions. 9

Additionally, specific information should be provided on the Automatic Terminal Information Service 10 (ATIS), and the phraseology should be adapted for fusing the attention of the crews (23). In the same manner, a 11 special signage is implemented for reproducing this special phraseology on board, and reminds the reduced 12 declared distances (O'Hare, 2009). 13

The last barrier against a catastrophic event is undeniably the air traffic controller. In the accident of 14 Perth in 2008, the controller plays a key role in the decision of making a go-around. At Paris-CDG in 2012, 15 three incursions on RWY26R by closed entry were stopped. Because the Air Traffic Control Tower is the key 16 resource in real-time, the awareness of the acting staff must be increased by a reinforced information. In 17 addition of special operational orders, mandatory briefings for the entire staff should be performed. 18 19 Temporary closures of the shortened runway 20 The airport operator should take provisions in case of, due to the construction works (heavy vehicle stuck 21 within the runway strip borders) or not (runway incursion, spontaneous crack), the shortened runway would 22 become unavailable. The goal is maintaining an equivalent level of safety, and especially mitigate the risk of 23 mistake from the crew (alignment of a wrong runway) if such an event occurs, 24

When RWY08L/26R (inner and longer runway) was shortened at Paris-CDG in 2012, a contingency 25 plan was written for continued operation of the second parallel RWY08R/26L (outer and shorter runway) of the 26 same South complex in case of the first one would be inoperative due to an incident of the construction works 27 (especially the morning of the re-opening of the runway, shortened). Consequently, if the inner runway would 28 be unavailable, the outer runway would remain accessible through two to four paths crossing the inner runway. 29 They would be highlighted with plastic ballasted cones and red lights. Finally, based on the accident of a 747-30 400 in Taipei in 2000, lighted crosses would be added beyond the edge of the last crossing paths, and forward 31 to a potential incursion on the wrong runway for takeoff. Finally, the inner runway itself would be closed by 32 the mandatory lighted crosses on the thresholds (24). 33 34 GOOD PRACTICES AND RECOMMENDATIONS 35 A displaced threshold means first reduced runway lengths. Consequently, the location of the temporary 36 threshold should carefully balance the needs of the construction works and the requirements of a representative 37 set of aircraft at their usual weights when they serve the airport traffic. It should also take into account the 38 likelihood of a runway excursion, modified by the reduction of the operational distances. 39

With the unavailability of at least the PAPI and the Glide Path of the initial threshold, alternatives to 40 the usual flight procedures should be decided in accordance to the average weather and the potential 41 exceptional adverse conditions. Except when a safety study demonstrates it is not the case, a temporary PAPI 42 should be considered a minimum but not sufficient condition for operating a displaced threshold, in order to 43 help the crews to aim the right area on the runway. Indeed, the past events prove that even with excellent 44 weather conditions, crews can encounter trouble in locating the threshold or in maintaining the right path. 45

The markings should only display the active information. Consequently, the initial threshold should be 46 removed or masked in order to avoid misunderstanding. Even if the displaced threshold is not operated with the 47 same operating conditions than the initial one, the same type of markings than the initial threshold should be 48 reproduced when it is possible, in order to not trouble the pilots. Adding a chevron bar, like in the U.S. 49 standards (25), strengthens the visual displacement of the beginning of the runway. The FAA standard is 50 equivalent to a combination of the two patterns of markings recommended by the ICAO (figure 2). Finally, the 51 standard 120 in-long crosses should be painted on the closed section. For night operations, the markings should 52 be reinforced by standard wing bar lights (26). 53

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1

2 3 The removal of all non-frangible obstacles from the full runway should be considered, if the operations 4

are allowed in the two orientations of the runway. The extension of this additional safety area and the eventual 5 operation restrictions should be determined through a safety study based on the runway characteristics, the 6 traffic profile, and a record of local and exogenous runway excursions. If the constructions are located on the 7 runway itself, conducting the operations only back to the works is an efficient mitigation measure. So, the 8 constructions should be protected from the jet blast by fences. 9

For safety assurance purpose, an inspection should be completed before the runway reopens in a 10 shortened configuration, to check that the risks mitigation plan is correctly implemented, and that the displaced 11 threshold, the construction works and the other mandatory provisions meet the certification specifications. A 12 similar common inspection should be completed before opening the full runway. During the operation of the 13 reduced runway, comprehensive checks should be performed on a daily basis, to verify that the measures are 14 properly maintained. These actions may be done by the airside operations acting staff, before or after the 15 runway inspection. A specific inspection sheet, on the model of the self-inspection form, should be provided to 16 the acting staff, for keeping a record of the risk assurance actions, and for insuring that these inspections are 17 comprehensive regarding the mitigation plan. 18

For informing the airside community (pilots, drivers, and controllers), a communication plan should be 19 implemented in complement to the basic regulatory aeronautical information (NOTAM or AIP supplement). 20 Aviation operations community websites, as this of the NFDC in the United States or the CDM (Collaborative 21 Decision-Making) portal of certain European airports, should be systematically used for providing information 22 and materials to the stakeholders. 23

FIGURE 2 Recommended markings for temporary displaced thresholds (ICAO and FAA)

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CONCLUSION AND PERSPECTIVE 1 Temporary displaced thresholds for construction works challenge project funding, construction design, ATC 2 procedures, runway operations, and aviation safety. For most of the issues they create, generic answers exist. 3 However, these solutions must be applied to local projects taking into account their specificities. Consequently, 4 they need an integrated, comprehensive, and pragmatic process for addressing the safety issues. 5

Airport Safety Management System (SMS) and its Safety Risk Management (SRM) component answer 6 to this challenge. The Safety Risk Management is a formal approach to assess the impacts of any modification 7 regarding the operations on safety, and mitigate them with adequate measures. ICAO defined the basics of an 8 airport SMS in the Annex 14 in 2005 (27), and in its future Annex 19, and the United States are in the process 9 of adding in 2014 provisions for a SMS for certified airports in U.S. 14 CFR Part 139 (28). 10

Because of their evident interdependence, the ATCT and the airport operator must coordinate their 11 safety risk analysis and the associated mitigation plan. The merger of their Safety Risk Management processes 12 for a same capital improvement operation should be considered, since the vision and the knowledge of these 13 two stakeholders are complementary. 14

As a single airport cannot have fortunately encountered the entire range of significant safety events 15 possible, it is relevant for such sensitive modifications to search for inputs from other airports. For this reason, 16 regional and international initiatives for sharing experience and best management practices in constructions 17 design between airport operators, Air Traffic Organizations, and consultants, as the Airport Construction 18 Advisory Council (ACAC) in the United States, must be promoted by the industry and the States. 19 20 REFERENCES 21

1. "Safety Management Manual", Doc 9859, 2nd

edition, ICAO, 2009. 22 2. "Airport Capacity and Delay", Advisory Circular No. 150/5060-5, FAA, September 1983, pp. 8-10. 23 3. "737-700/800/900 (With Winglets): Airplane Characteristics for Airport Planning", Boeing, September 24

2003, pp. 36-96. 25 4. "777-200LR/-300ER: Airplane Characteristics for Airport Planning", Boeing, June 2004, pp. 38-49. 26 5. " Aviation safety investigations & reports Airbus A340 ZS-SLA", Investigation No 200501819, ATSB, 27

http://www.atsb.gov.au/publications/investigation_reports/2005/aair/aair200501819.aspx 28 6. "Operational non-compliance at Perth Airport, WA on 9 May 2008", ATSB Transport Safety Report 29

(Final), Aviation Occurrence Investigation AO-2008-033, ATSB, June 2009. 30 7. "Annex 14, Aerodromes", Vol. I Aerodrome Design and Operations, 5

th edition, ICAO, July 2009, p. 31

7-2. 32 8. "Standards for Airport Markings", Advisory Circular No. 150/5340-1L, FAA, September 2013, p. 107. 33 9. "Temporary Displaced Threshold Markings", Manual of Standards Part 139 – Aerodromes, Version 34

1.10, CASA, May 2012, p. 8-24. 35 10. "What's on Your Runway? Mitigating Hazards Associated with Airport Construction", FAA ATO, p. 3. 36 11. "Serious incident on 16 August 2008 on take-off from Paris Charles de Gaulle Airport (95) to the 37

Boeing 737-800 registered SU-BPZ operated by AMC Airlines", BEA, 2011. 38 12. "AAIB Bulletin 2/2013", EW/G2012/07/23, AAIB, 2013, pp. 51-52. 39 13. "Runway overrun and fire/Air France Airbus A340-313 F-GLZQ, Toronto/Lester B. Pearson 40

International Airport, Ontario/02 August 2005", Report No A05H0002, TSB, 2007. 41 14. "Final Report on the Accident Occurred on 25 May 2008 at Brussels Airport on a Boeing B747-209F 42

Registered N704CK", AAIU-2008-13, FPSMT AAIU, 10 July 2009. 43 15. "Accident on 5 November 2000 at Paris Charles de Gaulle (95) to the Boeing 747-200 registered TJ-44

CAB operated by Cameroon Airlines", BEA, March 2003. 45 16. "Report on accident to M/S Kingfisher Airlines ATR-72 Aircraft VT-KAC at Mumbai on 10.11.2009", 46

Air Safety Directorate / DGCA, November 2011. 47 17. "Improved Models for Risk Assessment of Runway Safety Areas", ACRP Report 50, TRB, 2011. 48 18. "Annex 15, Aeronautical Information Services", Chapter 4 Section 4 Specifications for AIP 49

Supplements, 13th edition, ICAO, July 2010, pp. 5-1 and 4-4. 50

19. Hill, Steven. "NOTAM Proliferation", AIS-AIMSG 6th

meeting, Buenos Aires, November 2011. 51 20. Rosenkrans, Wayne. "What’s on Your Runway?", Aero Safety World, Vol. 7, July 2012, pp. 16–19. 52 21. Airport Construction Notices, NFDC, FAA, 53

TRB 2014 Annual Meeting Paper revised from original submittal.

Gaël LE BRIS 12

https://nfdc.faa.gov/xwiki/bin/view/NFDC/Construction+Notices 1 22. "Information aéronautique : publier n'est pas toujours suffisant", Objectif Sécurité n°15, October 2012, 2

pp. 11–12. 3 23. "Reduced Runway Length Operations during Construction/Work in Progress – ATIS and 4

Radiotelephony Messages", HindSight No 15, pp. 25-27, January 2012 5 24. "Operational Safety on Airports During Construction", Advisory Circular No. 150/5370-2F, FAA, 6

September 2011, pp. 22-23. 7 25. "Standards for Airport Markings", Advisory Circular No. 150/5340-1L, FAA, September 2013, p. 87. 8 26. "Annex 14, Aerodromes", Vol. I Aerodrome Design and Operations, 5

th edition, ICAO, July 2009, p. 9

5-51. 10 27. "Annex 14, Aerodromes", Vol. I Aerodrome Design and Operations, 5

th edition, ICAO, July 2009, pp. 11

APP 7-1. 12 28. "Safety Management System for Certified Airports", Docket No FAA-2010-0997 (NPRM), U.S. 13

Department of Transportation, October 2010. 14

TRB 2014 Annual Meeting Paper revised from original submittal.