Technical Report 8 - GW · 2016. 5. 24. · Table 1: Baseline state Runway 16 Runway 34 TORA-m 1945...

Technical Report 8

Astral Aviation Consultants – Construction Aeronautical Study

WEL98526 4820036.1

FINAL REPORT

WELLINGTON INTERNATIONAL AIRPORT

SOUTH RUNWAY EXTENSION AERONAUTICAL STUDY

ASTRAL LIMITED

April 2016

South runway extension aeronautical study

WEL98526 4820036.1 26 April 2016 Astral Limited 2

CONTENTS

1. Background ................................................................................................................................... 3

2. Construction overview .................................................................................................................. 3

3. Baseline case ................................................................................................................................. 4

4. Proposed change ........................................................................................................................... 5

5. Risk assessment ............................................................................................................................ 5

5.1. General .................................................................................................................................. 5

5.2. OLS Penetrations ................................................................................................................... 6

5.3. Mitigation of OLS penetrations ............................................................................................. 7

5.4. Other risk factors ................................................................................................................... 8

6. Runway 34 threshold displacement .............................................................................................. 9

6.1. General .......................................................................................................................................... 9

6.2. Conditions on use ......................................................................................................................... 9

6.3. Resulting state ............................................................................................................................. 10

7. Consultation ................................................................................................................................ 11

8. Method of Works Plan ................................................................................................................ 13

9. Conclusions................................................................................................................................. 13

Figures

Figure 1 Construction areas 14

Figure 2a Approach OLS (existing) 15

Figure 2b Take off climb surface (existing) 16

Figure 2c PAPI protection surface (existing) 17

Figure 3a Approach OLS (displaced threshold) 18

Figure 3b Take off climb surface (displaced threshold) 19

Figure 3c PAPI protection surface (displaced threshold) 20

Figure 4 Cross section at chainage 210m 21

Figure 5 Cross section at chainage 510m 21

Figure 6 Surface vertical profiles (long sections) 22

Appendix 1 – Method of Works Plan



1. Background

Wellington International Airport Limited (WIAL) wishes to develop a construction methodology for

the proposed 355m south runway extension that enables aircraft operations to safely continue

while construction is occurring. A “runway extension” in this report mean an increase in the

runway length available for take-off and landing. The length of the associated reclamation will

be more.

Astral has been asked to develop this methodology and in particular draft an Aeronautical

Study and Method of Works Plan (MOWP) which will establish that construction can be done

concurrent with safe aircraft operations.

The following reference documents were used to prepare this study.

AECOM Construction methodology report 42792153/01/01 dated 30 Jan 2015.

AECOM drawings S1.0, S2.0, S2.1, S3.0, S3.1, S3.2, S3.3, S4.0, S5.0, S6.0 and E1.0,

all rev 1 dated 19 May 20141

CAA Rule Part 139 Revisions 9 and 102

CAA Advisory Circular AC139-6 Revision 4 Aerodrome Design Requirements

CAA Advisory Circular AC139-15 Aeronautical Studies

Wellington Airport Type A Obstacle Chart 13th Ed dated Jul 2015

2. Construction overview

The complete project involves the construction of an approximately 10 ha reclamation and

commissioning of a 355m extension to the main runway and taxiway at the south end. This

requires the construction of a dyke which forms the sea wall protection at the perimeter of the

reclamation, draining and backfilling inside dyke, compaction, paving and fitting of services

including lighting and ILS equipment and involves the use of marine and land based plant and

equipment. The project is illustrated in Figure 1 and the construction methodology is

described in the AECOM Report.

1 We are advised that URS, who prepared the reports we reviewed, is now called AECOM and that there have

subsequently been later reports but these do not affect our report findings. 2 Revision 10 is the current version however Wellington Airport remains certificated under Revision 9. It is expected

construction will be done under revision 10.



In summary the dyke wall construction involves:

Possible excavation of the sea bed and placement of stone columns under the dyke as

a foundation.

Placement of fill material around the dyke perimeter in stages, initially using bottom

dumping barges, then ejector trucks from landside until the finished height of the dyke

is reached.

Placing the sea wall armouring (akmon or accropode) on the face(s) of the dyke using

either a barge mounted crane, land based crane, or both.

Once the dyke wall is constructed the following will occur:

Backfilling and compacting the drained area with material up to new runway and

taxiway level.

Construction of services, runway edging and surfacing.

Installation of new lighting, and painting and marking.

The construction is to be done during normal construction working hours (typically 7am to 5pm

6 days per week but could be 7 days per week to take advantage of good weather) with work

outside airport hours of operation (typically midnight to 6am) when required to avoid an

unacceptable impact on aircraft operations.

Of the estimated 3 to 4 year construction period, it is estimated that the measures discussed

to mitigate the aviation impacts of that construction will be in place for approximately 2 years.

3. Baseline case

The baseline case is operations from the existing runway. Currently the south runway end is

fully operational with no construction activity. Operational lengths are per the table below:



Table 1: Baseline state

Runway 16 Runway 34

TORA-m 1945 1921

ASDA-m 1945 1921

TODA-m 2300 2300

LDA-m 1815 1815

RESA undershoot-m 90 90

RESA overshoot-m 90 90

Approach OLS upslope Not affected 2.0% clear

Take-off OLS upslope 1.6% clear Not affected

Transitional OLS upslope Not affected 1:7 clear

The baseline case conforms to CAA aerodrome design standards and as there is no

construction occurring in the baseline case aircraft operations are unrestricted.

4. Proposed change

The proposed change is the presence of construction personnel, plant, and equipment

immediately at the end of the south RESA (runway 16 overshoot, runway 34 undershoot)

which will penetrate the existing 16 take-off, 34 approach and transitional OLS and the

precision approach path indication (PAPI) protection Surface (PPS). Sections 5 and 6 discuss

how this will be mitigated by the use of a displaced threshold for runway 34 landing.

Dust and glare from construction activity, interference with ILS signals, and presence of heavy

equipment in vicinity of taxiing aircraft are also changes that may occur as a result of

construction, however these can be appropriately managed.

5. Risk assessment

5.1. General

The risk assessment in this study is qualitative rather than quantitative, on the basis that:

a) The methodology for managing the aviation risk of construction on aerodromes is

well established via the MOWP process; and

b) The objective is to achieve an equivalent level of risk by protection of OLS



penetrations as exists in the present (non-construction) situation.

In the following sections risks are identified, discussed and mitigations developed.

5.2. OLS Penetrations

Figures 2a, 2b and 2c shows the height of the relevant AC139-6 obstacle limitation

surfaces (OLS) above mean sea level (AMSL) for the normal (non-construction) situation in

the vicinity of construction for the approach and transitional OLS, take-off OLS and PPS for

the existing threshold and OLS geometry.

Figures 3a, 3b and 3c show the same for the construction situation. Figures 4 and 5 on

page 21 shows cross sections of the vertical profile of the various surfaces at two different

distances (chainages) from the datum point. Figure 6 shows the upslopes of the various

profiles and location of their origins.

The PPS is similar in shape to the approach OLS but has a 300m base width compared to

150m and an upslope of 3.3%. Except on the western edge of the dyke the increased width

of the PPS is unlikely to present any problems for construction given its upslope of 3.3%

places the surface significantly above the approach OLS.

The height of typical construction equipment (bottom dumping barges and ejector trucks) is

4.5m. Any cranes (floating or land based) used to place protective armour on the dyke

walls is much higher, typically 23m AMSL.

The high point of the construction is the top of the dyke wall at 8.0m AMSL. Distances are

referenced as chainage, being meters southwards from the runway 34 threshold on

extended runway centreline.

The height of the 2.0% runway 34 approach OLS (origin height 7.1m AMSL) on centreline

at the extremity of the dyke wall (approximately 540m chainage) is 16.9m, giving an

equipment clearance of 7.9m to the OLS. However above the sections of the dyke wall

parallel to the runway, the OLS clearance progressively reduces to 0.9m which is clearly

inadequate for construction equipment clearance.

The runway 16 take-off OLS is more affected than the approach OLS. The take-off OLS

origin point is chainage 355m (height 11.6m AMSL) and it is currently clear to 1.6%

upslope. At the point where the take-off OLS centreline passes over the outer end of the

dyke wall (chainage 550m) its height is 14.7m, some 5.7m above the top of the dyke wall.



If a 2.0% upslope is used the clearance increases to 6.5m. As with the approach OLS the

lowest clearance occurs on the sides of the dyke parallel to the runway and close to the

OLS origin point. At this location there is 2.6m clearance beneath the take-off OLS.

In areas where OLS penetrations occur equipment has to remain outside while aircraft are

operating. This means construction must be performed either between aircraft movements

or outside hours of operation of the airport. The objective is to minimize the size of the

“keep out” area, consistent with safe aircraft operations, to maximise the amount of

construction which can safely occur during aircraft operations. This increases construction

efficiency and reduces the amount of higher risk night work.

5.3. Mitigation of OLS penetrations

OLS penetrations can be mitigated in several ways:

Increase the height of the OLS such that penetrations do not occur

Remove the source of the penetration

Enable the penetrating obstacle to be seen and avoided by the pilot

Increase the height of the aircraft flight profile so it safely clears the penetration

A combination of the above

Increasing the height of the OLS can, for the approach OLS, be achieved by either or both of

displacing the landing threshold and with it the origin point of the OLS or steepening the OLS

gradient. This is possible for landing on runway 34 by displacing the threshold 100m north

and increasing its upslope from 2.0% to 2.5% which is permitted under AC139-6 for domestic

aerodromes.3 This mitigation, which requires alterations to runway lighting and marking and

instrument approach procedures, is discussed further in section 6.

Removing the source of the penetration would mean not permitting construction equipment

within the OLS area while aircraft operations are occurring. This is possible but would mean

work would be disrupted during aircraft operating hours to the point where little progress could

be made. Therefore this mitigation is only practical for aircraft operations that occur relatively

infrequently (such as international departures or arrivals), or when the aerodrome is closed to

aircraft movements i.e. in the curfew hours.

3 Taking the view that for a domestic flight the aerodrome can be regarded as a “domestic aerodrome”



Enabling the penetration to be seen and avoided is not considered practical for penetrations

so close to the end of the runway. When this low on approach the aircraft should not be

manoeuvred other than as required to remain on the approach path. On take-off, due to the

nose high attitude of the aircraft, the pilot is not able to easily see a close-in obstacle to enable

it to be avoided. This mitigation is therefore not considered practical.

Increasing the height of the aircraft flight path is not possible on approach as the approach

glide path is fixed at 3.0 deg by both the instrument landing system (ILS) glide path and the

PAPI settings. While a steeper approach could be used with a new temporary PAPI, 3.0 deg

is the international standard and to use an appreciably steeper path requires specific crew

training and increases the risk of heavy landing due to the higher vertical descent speed.

Increasing the height of the flight path on take-off is possible by reducing the take-off weight of

the aircraft. Taking account of flight path obstacles is standard airline procedure in calculating

the aircraft weight limit under the existing ambient conditions for each take-off. This mitigation

is therefore practical for take-off, however as reducing aircraft take-off weight potentially

reduces payload this mitigation has limited use. An upslope of 2.0%, which conforms with that

specified in AC139-6, is considered the maximum desirable to avoid payload limitations.

A combination of these mitigations is viable, in particular the combination of raising the height

of the OLS and displacing the threshold (approach), raising the aircraft flight path (take-off)

and eliminating the penetration (approach and take-off) by controlling access of construction

equipment under the OLS.

5.4. Other risk factors

These include the usual construction risks of glare, dust, foreign object damage to aircraft

(FOD) and proximity of equipment to moving aircraft. Glare is usually only a problem with

lighting of works areas. This can be avoided by largely confining works to daylight hours or, if

at night, ensuring lighting is shielded from aircraft flight and taxiing paths.

Dust is controlled by ensuring loose material is covered or liberally watered to keep it in place.

The frequency of strong winds at the aerodrome make this a hazard that requires particular

care. FOD also requires extra care in windy conditions by making sure all barriers, cones,

markers and construction materials are firmly held down. Regular FOD checks, particularly

before the start of aircraft operations in the mornings are essential. Keeping construction

equipment access routes well away from aircraft operational areas (physical separation) also



helps minimise FOD risk.

Finally an effective safety incident reporting system recording any safety incidents or observed

hazards to aircraft operations with regular meetings between stakeholders (including

operating airlines) is very effective in ensuring any issues are promptly and effectively

addressed. This should be part of the airport operator's normal safety management

processes.

All these mitigations would be included in the Method of Works Plan.

6. Runway 34 threshold displacement

6.1. General

Displacing the runway 34 threshold will increase the approach OLS clearance over the works

area thereby reducing the extent of the “keep out” area for construction equipment. However

displacement reduces the runway 34 landing distance available which is already relatively

short for jet aircraft operations. After reviewing the landing performance of the 737-800 and

the A320 Astral recommends 100m as the maximum viable threshold displacement. It is also

the minimum to give any appreciable benefit. There is a 1 to 1 relationship between threshold

displacement and the proximity to the existing threshold for construction equipment i.e. a

100m displacement means equipment can work 100m closer to the existing threshold while

aircraft are operating. This is a considerable advantage to construction.

It should also be noted that CAR139 Rev 10 at Appendix D.1(d) prohibits new objects above

the approach surface (OLS) within 3000m of the surface origin point unless an aeronautical

study establishes no adverse effects to aircraft safety or regularity of operations. A similar

prohibition applies to the take-off OLS under Appendix D.2(b). The required upslopes of the

surfaces are specified in AC139-6 Tables 4-1 and 4-2.

In conjunction with the displaced threshold Astral considers that the associated approach OLS

can be steepened to 2.5% (1 in 40), as is permitted AC139-6 Table 4-1 for domestic

aerodromes, for the operation of domestic flights. This would have to be accepted by the

CAA.

6.2. Conditions on use

As the displaced threshold will not have an ILS glide path installed, or have lighting and

marking (other than wing bars, marker boards and PAPI) it will not be available under all



conditions. Specifically the following conditions would need to apply:

Daytime hours only

Weather conditions for use of runway 34 to be at or better than 1100ft-5km (Cat C/D VOR

DME runway 34, circling minima)

A RNP or RNAV instrument approach with barometric glide path guidance is to be available

A full (4 box) PAPI is to be provided

6.3. Resulting state

Table 2 shows the resulting state (configuration) of the runway with the displaced threshold

and works occurring up to but outside of the “keep out” area.



Table 2: Resulting state with displaced threshold during construction

Runway 16 Runway 34

Existing Proposed with

displaced

threshold

existing Proposed with

displaced

threshold

TORA-m 1945 1921

ASDA-m 1945 1921

TODA-m 2300 2300

LDA-m 1815 1815 1715

RESA undershoot-m 90 90

RESA overshoot-m 90 90

Approach OLS upslope Not affected 2.0% clear 2.5% clear4

Take-off OLS upslope 1.6% clear 2.0% clear Not affected

Transitional OLS upslope Not affected 1:7 clear

PAPI yes yes

Night operations5 yes no yes no

ILS yes yes LLZ only

RNP-AR yes yes

RNAV(GNSS) yes yes

Minima Per AIP or airline approval Per AIP or

airline approval

1100ft-5km6

7. Consultation

The scheduled jet operating airlines (Qantas Group, Virgin and Air New Zealand) have been

consulted regarding the feasibility of displacing the runway 34 threshold 100m to the north. No

airline objections to the displacement were received on the understanding that the following

conditions will apply and facilities will be provided for the displaced threshold:

4 2.0% may be provided for international arrivals 5 No night ops if existing OLS is infringed 6 Minima for displaced threshold operations



Conditions for use of displaced threshold

a) Day use only (to avoid the need for lighting configuration changes)

b) 1100ft/5km visibility restriction (to avoid operating restrictions on operators that do not

have RNAV(GNSS) with barometric vertical guidance capability).

Facilities to be available

c) A 4 box PAPI

d) A non-precision approach with (RNP or RNAV (GNSS)) with barometric height

guidance

e) Temporary touchdown markings or zone limit markers

f) All relevant AIP data for the runway with displaced threshold, using different runway

designator, such as runway 35, or yellow pages.

Qantas advised that its 737-800 operations may be restricted in landing weight on runway 34

under wet runway conditions with the reduced landing distance from the displaced threshold.

At the time of preparing this report Qantas had not quantified this possible restriction but, in

Astral's view, it could be avoided “on the day” by reversion to full runway length on pilot

request for inbound international flights. This would be consistent with the international

requirement for a 2.0% approach OLS.

Virgin, operating the same type of aircraft advise that the runway grooving may enable them to

use dry runway performance on most “wet” occasions and avoid a landing weight penalty.

Existing or planned displaced threshold operations at both Christchurch and Auckland airports

which have the similar provisions were noted by the airlines.

Airways Corporation were also consulted and advised that they had no objections to the

proposal and, given adequate lead time, can support the airlines' requirements. Airways noted

the need to provide a clear PAPI protection surface (PPS).

On the basis of the consultation it is concluded the 100m displaced threshold can be

implemented and operated safely, thereby minimising the “keep out” area for construction

equipment.



8. Method of Works Plan

A Method of Works Plan (MOWP) for the proposed works, including the displaced threshold

has been drafted and this in included at Appendix A to this study for reference purposes.

The MOWP, which is in essence a safety plan to ensure aircraft operations are protected from

construction activity (and vice versa), is suitable as a basis for discussion with the works

contractor. It must be emphasised the MOWP presented is a starting point for contractor and

airline discussions only and as a result of discussions it may be determined there is a better

way to do the works that enhances both safety and efficiency during construction.

9. Conclusions

The runway extension works are feasible from an aircraft operational safety perspective using

methods and procedures that are established and proven in works at other aerodromes. In

particular the use of a 100m displaced runway 34 threshold with a 2.5% upslope approach

OLS will minimise the size of the “keep out” area for construction equipment thereby reducing

the amount of work that needs to be done outside aircraft operating hours.

Airlines have been consulted and have no concerns over displaced threshold operations

under the conditions specified in section 7 which are reflected in the draft MOWP.

The next steps would be to familiarise the preferred contractor with the MOWP to ensure its

requirements are considered in construction tendering and the contractor's Method Statement

and to invite feedback from the contractor on the MOWP.

Airlines should also be appraised of the MOWP and given the opportunity to provide feedback

and suggestions on its refinement.


WEL98526 4820036.1 26 Apr 16 Astral Limited 14

Figure 1:

Construction areas



Figure 6

Technical Report 8 - GW · 2016. 5. 24. · Table 1: Baseline state Runway 16 Runway 34 TORA-m 1945...

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