Air Transport

Study finds some environmental approach procedures to be potentially dangerous and demands more analysis

Risky approach and departure procedures adopted solely for environmental reasons must be subjected to safety analysis, demands a just-released international study commissioned by the UK Civil Aviation Authority.

The study reveals that many aviation environmental procedures were designed without analysing the "system safety case", and it cites noise abatement flight profiles and the choice of specific runway approaches that prioritise the minimising of noise nuisance instead of optimum operational considerations.

Where system safety analyses were not done before they must be carried out now, insists the report, Delivering safety in the context of environmental restrictions. It was researched by Cranfield University's professor Peter Brooker, CAA professor of air traffic management and environmental policy.

Brooker says the procedures that give cause for concern include some noise preferential routeings (NPR) and continuous descent approaches (CDA), but particularly the use of a non-precision approach (NPA) solely for environmental benefit when an alternative precision approach is available.

On the latter, Brooker says:"The evidence is that the use of [NPAs] solely for environmental reasons is unwise. This is a policy conclusion, not a requirement for any further work." The Brooker study was presented to the CAA before publication of the final report on the fatal accident considered to be the classic example of the risks of putting environment before safety. This was the November 2001 crash in which a Crossair BAE Systems Avro RJ00 hit high ground on a night VOR/DME NPA to runway 28 at Zurich Kloten airport, Switzerland. Although the aircraft was originally cleared for a precision instrument landing system approach to runway 14, a curfew for that approach was about to come into force so the RJ was told to fly the VOR/DME to runway 28.

Just 6.5min after the curfew started, the aircraft slammed into a hillside in poor visibility with snow, killing 24 of the 33 people on board. Brooker tells Flight International that, had the accident investigation report been published before he presented his study, it would have served to emphasise his existing conclusions and he "would have written differently". Brooker's report says that an NPA inherently "is 8.5 times more risky than a precision approach". He adds: "The message from studies of accidents is clear: it is difficult to see how the use of [NPAs] when precision approaches are available can be justified purely for environmental reasons".

On the use of non-optimal runways, Brooker cites a December 1997 Transavia Boeing 757 accident at Amsterdam Schiphol where runway 27 was used for environmental reasons rather than the into-wind runway 24. The accident investigation "identified the strong crosswind during the landing manoeuvre as a major contributory factor to the cause of the accident". The nose-wheel collapsed during the landing, but no-one was hurt. He cites pressure to carry out tailwind landings as particularly dangerous in wet weather.

DAVID LEARMOUNT / LONDON