DAVID LEARMOUNT, OPERATIONS & SAFETY EDITOR
The issue of runway incursions has emerged as a cause for concern in Europe
According to the United Nations Security Council, last year's four worst aviation disasters were the result of an "act of war". The attacks of 11 September, which destroyed four US-registered airliners, may have succeeded because of security failures (see P29), but the events were not "accidents". For these reasons, as with other acts of war, the 11 September events do not come under the "safety" heading.
Nor was the 4 October accidental missile downing of a Sibir Airlines Tupolev Tu-154 over the Black Sea the result of a safety failure. The 78 people on board died because of an accident during a military exercise.
So, five major recent aircraft disasters, which killed 343 people in the air and over 3,000 on the ground, are irrelevant to any projections for the future of aircraft safety. The focus has to be on events that can be categorised as accidents.
There appears to be no specific trend in 2001. The number of small commuter and regional aircraft crashes was similar to other years. Of four accidents to large passenger-carrying jets, however, three involved issues likely to have repercussions.
The first, the 8 October collision at Milan Linate airport, Italy, between an SAS Boeing MD-87 and a Cessna Citation Jet, in which all 114 people on board the aircraft were killed, has already focused the attention of Europe's safety authorities on the issue of runway incursion (Flight International, 16-22 October 2001). The hazard has already been recognised by the USA, and is high on the Federal Aviation Administration's action list.
Europe has started by collecting data on all runway incursion incidents to help judge the nature and extent of the problem. As soon as this is better defined, European hub airports will probably be compelled to install surface movement detection systems, as in the USA. This would enable air traffic controllers to detect aircraft taxiing in the wrong direction before safety is affected. The Linate crash, caused by a pilot not taxiing on the correct route, occurred after an old surface movement radar had been removed before its replacement was ready.
Unknown cause
The cause of the crash of an American Airlines Airbus A300-600 soon after take-off from New York Kennedy on 12 November is still unknown. Certainly the vertical tail fin and the engines had detached before the aircraft hit the ground, but it is not yet clear why the fin broke away. The engines probably separated after the aircraft went out of control. The investigation has now moved to NASA's Langley laboratories, where materials specialists hope to determine whether the all-composite fin failed under stresses beyond its design strength - though the flight data recorder has not yet yielded any conclusive information on this point.
NASA will also investigate whether flutter developed in the fin and snapped its mountings, or whether there was an undetected crack or weakness in the composite material. Whatever NASA finds will be crucial for aircraft design and manufacture, since primary load-bearing structures, like the A300's fin, are increasingly being made out of composite materials.
Finally, the 24 November Crossair British Aerospace Avro RJ100 that crashed on a non-precision approach to Zurich Kloten in Switzerland will raise crucial questions about the conflict between best operational practice and best environmental procedures for an airport (Flight International, 4-10 December 2001).
In this case, the aircraft was completing its approach into Zurich too late in the evening to use a runway equipped with instrument landing systems (ILS). Noise restrictions prevented its use after 22:00h.
Although it was night, with poor visibility and light snow, the aircraft was required to perform a non-precision approach using a VOR/DME approach. The aircraft hit trees short of the runway; 24 people died.
Non-precision risk
Irrespective of the accident investigation's eventual findings, the Flight Safety Foundation's approach and landing accident reduction task force has already established that serious accidents are between five and seven times as likely to happen on non-precision as on precision approaches. Decision-makers who put environmental considerations ahead of operational ones will have to take more care that they do not raise levels of risk.
Source: Flight International