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ASN Wikibase Occurrence # 225110
Last updated: 22 May 2019
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Time:21:49 LT
Type:Silhouette image of generic B733 model; specific model in this crash may look slightly different
Boeing 737-376
Registration: VH-TJB
C/n / msn: 24296
Fatalities:Fatalities: 0 / Occupants: 85
Other fatalities:0
Aircraft damage: Minor
Category:Serious incident
Location:Darwin International Airport, NT (YPDN) -   Australia
Phase: Landing
Nature:Domestic Scheduled Passenger
Departure airport:Adelaide Airport, SA (YDL/YPAD)
Destination airport:Darwin International Airport, NT (YPDN)
Investigating agency: ATSB
The Boeing 737-376 aircraft, registered VH-TJB, landed on runway 29 at Darwin. The aircraft touched down close to the right edge of the runway and ran off the sealed runway surface. The handling pilot returned the aircraft back to the runway during the landing roll. There were no reported injuries to either the passengers or crew. The aircraft sustained minor damage.

The aircraft was operating a scheduled public transport passenger service between Adelaide and Darwin, with six crew and 79 passengers. The approach was conducted at night and in conditions of reduced visibility due to rain. The automatic terminal information service (ATIS) reported 6,000 m visibility at the aerodrome.
The runway was wet and the previous landing aircraft had reported that the braking action on the runway was good. The aerodrome controller had selected the high intensity approach lighting (HIAL) and high intensity runway lighting (HIRL) to Stage 6 (maximum intensity). The visual approach slope indicator system (T-VASIS) was operating. Due to the weather conditions, the crew elected to perform a monitored approach and configured the aircraft with flap 40, and the autobrake set to 3.

Initial approach
Consistent with company procedures, the copilot was the handling pilot for the initial stage of the monitored approach and provided input to the aircraft's automatic flight management system. The pilot in command monitored the progress of the approach and attempted to establish visual reference with the runway. The aircraft was flown with both autopilots engaged and coupled to the instrument landing system (ILS) for runway 29. The threshold reference speed (Vref) for a flap 40 landing was 131 kts.
Analysis of data from the aircraft's flight data recorder (FDR) confirmed the aircraft was configured for landing prior to reaching the outer marker (OM) and that the approach parameters were stable. The pilot in command recalled that the aircraft crossed the OM and was at an altitude of approximately 1,000 ft when the HIAL became visible. At the decision altitude (DA) he could clearly see the approach lighting and runway lights and decided to continue the approach and land the aircraft. Consistent with company procedures for the monitored approach, the pilot in command became the handling pilot for the remainder of the approach and landing. The aircraft's landing lights were 'ON' during the final approach and landing.

Final approach
The FDR indicated that the autopilot was disengaged approximately 2 to 3 seconds after passing the DA and about 20 seconds prior to touchdown. At the time of autopilot disengagement, the aircraft was established on the localiser and glide slope, maintaining a heading of 283 degrees magnetic (deg M) and was about 200 ft above the height of the runway threshold (HAT). The aircraft's flight path deviated above glide path following disengagement of the autopilot.
About 6 seconds after the autopilot was disengaged, the FDR recorded a control wheel input that resulted in a slightly right wing low bank attitude and then application of left rudder. The combined effect of those control inputs altered the aircraft's heading to the left, but introduced a sideslip to the right and a corresponding angle of drift. The localiser deviation recorded on the FDR indicated that the aircraft started to drift right of the extended runway centreline about 13 seconds before touchdown. Application of left rudder and roll attitude that was predominantly right wing low continued to the point of touchdown, by which time the aircraft's heading was about 7 degrees left of the aircraft's ground track and the localiser deviation indicated 0.57 dots 'fly left'. The control wheel inputs resulted in deployment of the right wing's flight spoilers during the final 70 ft of descent.
The pilot in command recalled that during the final stages of the approach, he could see the runway lights along the full runway length and was satisfied that he had the required visual reference to continue the approach. He recalled that rain was streaming across the windscreen and that the wipers were operating. As the aircraft descended into the touchdown zone he observed that the runway surface was very dark and there was a lack of surface definition. He recalled shifting his gaze from the runway aim point to the cues available at the far end of the runway to judge the height for the landing flare. The pilot in command recalled hearing the synthesised calls of altitude from the aircraft's radar altimeter, which occurred at radar altitudes of 50 ft, 30 ft and 10 ft.
The pilot in command recalled that he did not detect any anomalies with the aircraft's approach path during the final stages of flight and was unaware that the aircraft had commenced to sideslip as it approached the runway. The copilot recalled that he did not detect any anomalies with the aircraft's flight path as he monitored the various flight instruments during the final stages of the approach.
The FDR recorded a backing of the wind direction and a gradual increase in wind speed during the 11 seconds prior to touchdown. Although this change in wind velocity represented an increasing left crosswind component as the aircraft approached the runway, this occurred after the aircraft had commenced the sideslipping manoeuvre.

Touchdown and landing roll
The pilot in command recalled that, due to the wet runway surface, he intended to make a firm touchdown on the runway. During the final stages of the flight, the aircraft's pitch attitude increased from about 2 to 3.2 degrees nose-up. Analysis of data from the FDR indicated that the aircraft touched down with a descent rate of approximately 600 ft/minute and a vertical deceleration of 2.3 g. Information contained in the operator's manuals indicated that the normal descent rate for touchdown should be about 150 ft/minute, with a nose-up pitch attitude of between 4 and 6 degrees.
The pilot in command recalled that immediately after touchdown, he brought his view back down the runway and saw that the runway edge lights were tracking down the windscreen centre frame. He immediately realised that they were close to the right edge of the runway and heard the aircraft wheels strike runway lights. Corrective control inputs returned the aircraft to the runway centreline and the aircraft completed the rollout.
Marks on the runway and data from the FDR provided further information on the touchdown and landing roll. Touchdown occurred approximately 520 m from the threshold of runway 29, at a computed airspeed of 127 kts (a ground speed of about 128 kts). The right main landing gear was about 1.4 m inside the edge of the runway and the aircraft was sideslipping to the right. The right main landing gear departed the runway about 590 m from the threshold, at a ground speed of about 124 kts. The left main landing gear departed the runway about 760 m from the threshold, at a ground speed of about 111 kts. Corrective control inputs by the pilot had returned all wheels to the runway by about 1,130 m from the threshold. At the maximum point of excursion, the right main gear was about 7 m from the edge of the runway and the left main gear was about 2 m from the edge of the runway.
The pilot in command taxied the aircraft clear of the runway. Although there were no abnormal cockpit indications about the landing gear, he requested a precautionary inspection of the aircraft's landing gear by the airport's emergency rescue and fire fighting service before taxiing to the terminal.

ATSB Conclusion
The investigation concluded that the presence of runway centreline lighting would have increased the visual cues available to the pilot and assisted with his recognition of the developing sideslip and lateral deviation from the centreline.



Photo of VH-TJB courtesy

Adelaide - International (YPAD / ADL)
11 December 1994; (c) David Tanner (via Daniel Tanner)

Revision history:

15-May-2019 09:37 harro Added
15-May-2019 10:32 harro Updated [Departure airport]

Corrections or additions? ... Edit this accident description