Nepal

The balance of evidence suggests that the primary cause of the accident was that one or both pilots consistently failed to follow the approach procedure and inadvertently adopted a profile which, at each DME fix, was one altitude step ahead and below the correct procedure. Why and how that happened could not be determined with certainty because there was no record of the crew's conversation on the flight deck. Contributory causal factors were thought to be the inevitable complexity of the approach and the associated approach chart.
The following findings were reported:
- The flight deck crew were properly licensed and medically fit,
- The aircraft had been properly maintained and was fit for the flight and the essential aircraft systems were operating normally during the approach,
- The SIERRA approach to Kathmandu is a demanding approach in any wide-bodied aircraft,
- Unlawful interference and extreme weather were not causal factors,
- The crash site was enveloped in cloud at the time of the accident,
- There was no ATC clearance error,
- The VOR DME beacons used for the approach were operating satisfactorily and there was no evidence of failure or malfunction within the aircraft’s DME equipment,
- The aircraft acquired and maintained the correct final approach track but began descent too early and then continued to descend in accordance with an altitude profile which was consistent with being 'one step ahead' and below the correct profile,
- At 16 DME the co-pilot mis-reported the aircraft’s altitude by 1,000 feet,
- The commander did not adhere to the airline’s recommended technique for the final part of the approach which commenced at 10 DME,
- The 10 DME position report requested by the Tower controller was made at an altitude below the minimum safe altitude for that portion of the approach,
- The altitude profile on the Jeppesen approach chart which should have been used by the pilots was technically correct. However, the profile illustrated could not be flown in the A300 at V app, in common with any other wide-bodied jet of similar size and the minimum altitude at some DME fixes was not directly associated with the fix,
- The aircraft did not have control column mounted chartboards,
- As described in the report, there is scope for improving the SIERRA approach procedure and its associated charts,
- Kathmandu was not a frequent destination for PIA’S A300 crews and neither pilot had operated that within the previous two months,
- PIA’s training of air crews, briefing material and self-briefing facilities for the SIERRA approach to Kathmandu leave room for improvement,
- PIA’s route checking and flight operations inspection procedures were ineffective,
- The accident was inevitable 15 seconds before impact,
- The Tower controller requested an altitude report immediately after the co-pilot reported at 10 DME. His failure to challenge the low altitude reported at 10 DME was a missed opportunity to prevent the accident but, even if he had done so, it is doubtful whether the accident could have been averted,
- Some air controllers at Kathmandu had a low-self-esteem and was reluctant to intervene in piloting matters such as terrain separation,
- The GPWS was probably serviceable but failed to warn the crew of impending flight towards high ground because of the combination of elderly equipment and rugged terrain,
- Advice within the aircraft manufacturer’s operating manuals regarding pilot reaction to a GPWS warning was incomplete,
- The MEL was being breached in that PIA wen not supplying their CAA with the required carry-forward defect summaries for analysis, neither was the CAA requesting them.

It was determined that the nose gear tyre burst after hitting stones coming from a pothole in the runway surface. This caused the nose gear to collapse.

TG311 flight crew's management of the aircraft flight path wherein the flight proceeded in a northerly direction which was opposite to the cleared point Romeo to the South; ineffective radio communication between the area control centre and the TG311 flight crew which allowed the flight to continue in the wrong direction, in that the TG311 crew never provided the aircraft's VOR radial when stating DME and the controller never solicited this information and thus the aircraft's position was not transmitted at any time; and ineffective cockpit crew coordination by the TG311 crew in conducting flight navigation duties. Contributing factors were: the misleading depiction of Romeo on the operator's approach chart used by the flight crew; a flap fault, although corrected, required that the initial approach be discontinued; and radio communication difficulties between the TG311 crew and the air traffic controllers that stemmed from language difficulties and ineffective discussion of apparent unresolved problems.

Controlled flight into terrain following a wrong altimeter setting. It was determined that the crew departed Surkhet Airport under VFR mode but while climbing, he encountered limited visibility as the mountain struck by the aircraft was shrouded in clouds. At impact, the captain's altimeter showed 7,350 feet while the aircraft's real altitude was 5,800 feet.

It was determined that the crew initiated the descent prematurely, causing the aircraft to descend below the MDA.