Srilankan A320 at Singapore on Mar 21th 2019, temporary runway excursion on landing

Last Update: April 4, 2020 / 13:54:41 GMT/Zulu time

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Photo of Srilankan Airlines 4R-ABN, Airbus A320 — Srilankan Airlines 4R-ABN, Airbus A320 (Photo credit: Alec BHX/KKC / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Mar 21, 2019

Classification
Incident

Airline
Srilankan Airlines

Flight number
UL-308

Departure
Colombo, Sri Lanka

Destination
Singapore, Singapore

Aircraft Registration
4R-ABN

Aircraft Type
Airbus A320

ICAO Type Designator
A320

Airport
Singapore Changi International Airport, Singapore

Airport ICAO Code
WSSS

A SriLankan Airlines Airbus A320-200, registration 4R-ABN performing flight UL-308 from Colombo (Sri Lanka) to Singapore (Singapore), landed on Singapore's runway 02L but veered towards the runway edge and damaged a runway edge light. The aircraft taxied to the apron.

The aircraft departed for the return flight on schedule.

On Apr 12th 2019 Singapore's AIB reported they have opened an investigation into the occurrence rated a serious incident.

In Apr 2020 Singapore's AIB released their final report concluding the probable causes of the incident were:

- Shortly after disengaging the autopilot, the aircraft started to deviate to the right, away from the centre of the runway. This was the cumulative effect of a series of right roll inputs from the PF and the left crosswind that was increasing in strength.

- The aircraft touched down to the right of the runway centreline and veered past the right runway side stripe marking, damaging a runway edge light in the process.

- The flight crew was aware that they should go-around if the approach was destabilised. However, they appeared not to have recognised that the approach had become destabilised.

- The PF used the NWS tiller in an apparent attempt to steer the aircraft back towards the centre of the runway, despite the aircraft groundspeed being higher than the normal range of speed to operate the tiller.

- The flight crew did not file an occurrence report. Without such a report, the damaged runway edge light posed a FOD hazard to other aircraft using the runway until it was detected and removed during a routine runway inspection six hours later.

The AIB reported the captain (53, ATPL, 5,055 hours total, 2,959 hours on type) was pilot flying, the first officer (26, CPL, 2,216 hours total, 1,850 hours on type) was pilot monitoring.

The flight was cleared for an ILS approach to runway 02L, winds were reported from 310 degrees at 12 knots, RVR was reported at 1700 meters, the crew conducted the ILS approach with autoflight engaged. At decision height the approach was fully stabilized, runway visual contact was established despite rain. At 190 feet AGL the captain disengaged the autopilot, within one second of the autopilot disengagement the pilot flying applied both elevator (nose up) and right roll inputs via the control stick as well as rudder pedal input causing the aircraft to reach 6 degrees right bank. The aircraft progressively deviated from the extended runway center line to the right. At 70 feet AGL the captain initiated the flare.

Descending through 13 feet AGL the captain applied left roll input which brought the wings to nearly level and provided a left rudder input. The aircraft however was still drifting to the right of the runway center line.

The aircraft touched down to the right of the runway center line with the nose pointing towards the left of the runway. After touchdown the aircraft continued to skid to the right edge of the runway. The captain applied right rudder, the aircraft was aligned with the runway heading.

The thrust reversers were deployed and maximum reverse was applied for 19 seconds. When the ground speed dropped through 110 knots the captain applied left rudder and applied left nose wheel steering inputs. In the meantime the right main gear travelled past the right runway egde. The aircraft subsequently returned onto the center line of the runway, vacated the runway via taxiway W4 and taxied to the apron.

A routine post flight inspection revealed no anomaly.

6 hours later a runway inspection found a damaged runway edge light near taxiway W7, a runway surveillance camera identified 4R-ABN had contacted and broken the runway light.

The AIB reported runway 02L was 4000 meters long and 60 meters (200 feet) in width, the runway edge lights were 2.5 meters outside the runway edge lines.

The AIB analysed:

In this occurrence, the aircraft had become destabilised during its approach to land. The flight crew did not carry out a goaround. They appeared not to have recognised that the approach had become destabilised despite the following signs:

a) The aircraft was on a continuous right deviation from the point of autopilot disengagement until touchdown.

b) The PF provided a significant left roll input in an attempt to bring the aircraft to a wings level attitude and pilot the aircraft back towards the centre of the runway, about 17 feet AGL, just moments before touchdown.

The AIB analysed that the use of the nose wheel steering tiller at 110 knots was highly unusual, the tiller would be inhibited at that speed anyway. The AIB wrote: "As soon as the aircraft landed, the PF used the NWS tiller seemingly in the hope that the large NWS angle afforded by the tiller (as compared with the NWS angle if the rudder was used) would allow him to steer the aircraft back quickly towards the runway centreline, but forgetting that the NWS tiller was actually inhibited at that time, given the aircraft groundspeed of 110 knots."

With respect to the lack of occurrence reporting the AIB analysed:

The damage to the runway edge light was discovered approximately six hours later by the aerodrome operator during its scheduled runway maintenance. The damaged edge light could potentially have been a foreign object debris (FOD) hazard to other aircraft using the runway.

While the flight crew might not know that their veering aircraft had damaged the runway edge light, the use of the NWS tiller almost immediately after touch down suggests that they were aware of the aircraft’s drifting to the right edge of the runway. It would have been prudent on the part of the pilots to report the abnormal landing to ATC. This would have allowed ATC or the aerodrome operator to inspect the runway and remove any FOD as soon as possible.>/i>

Metars:
WSSS 211200Z VRB02KT 9000 FEW017TCU FEW018CB SCT270 24/23 Q1010 RETS NOSIG=
WSSS 211130Z VRB02KT 7000 -TSRA FEW015 SCT017TCU FEW018CB 24/22 Q1010 RESHRA BECMG FM1145 TL1200 NSW=
WSSS 211100Z 34006KT 290V050 2000 +TSRA FEW014 SCT016TCU FEW018CB 23/22 Q1010 WS R20C BECMG TL1130 4000 -TSRA BECMG FM1145 TL1200 6000 NSW=
WSSS 211030Z VRB02KT 9000 4000NE -SHRA SCT015TCU FEW017CB SCT270 28/24 Q1009 RETS TEMPO FM1045 TL1130 3000 TSRA=
WSSS 211000Z VRB02KT 8000 -TSRA FEW015CB SCT016TCU 27/24 Q1008 BECMG FM1100 TL1115 NSW=
WSSS 210930Z 21005KT 180V240 8000 -TSRA FEW012 FEW015CB SCT016TCU 27/24 Q1008 BECMG FM1000 TL1030 NSW=
WSSS 210900Z 24006KT 200V350 8000 3500W -TSRA FEW012 FEW015CB SCT016TCU 28/24 Q1008 TEMPO TL1000 1000 +TSRA=
WSSS 210830Z 05011KT 010V100 9999 4000S -TSRA FEW012 SCT016TCU FEW017CB 31/22 Q1007 WS R02L TEMPO TL0930 05017G30KT 1000 +TSRA=
WSSS 210800Z 04010KT 9999 VCSH SCT017TCU FEW020CB BKN300 32/22 Q1007 TEMPO FM0820 TL0905 3000 TSRA=
WSSS 210730Z 04009KT 350V080 9999 SCT020TCU BKN300 33/23 Q1008 NOSIG=
WSSS 210700Z 05010KT 020V080 9999 FEW020TCU SCT023 BKN300 34/23 Q1008 NOSIG=