David Learmount/AMSTERDAM
AIRLINES CARRYING out non-precision approach and landing procedures face a five-fold increase in the risk of a controlled-flight-into-terrain (CFIT) accident compared with precision approaches, according to research by the Netherlands' National Aerospace Laboratory (NLR).
The Flight Safety Foundation (FSF), as part of its International Civil Aviation Organisation-backed campaign to reduce CFIT accidents, has long maintained that most CFIT crashes happen on step-letdown approaches using navigation beacons such as VORs and distance-measuring equipment (DME). The December 1995 crash of an American Airlines Boeing 757 on a VOR/DME letdown to Cali, Colombia, is a recent example of such an accident.
The theory, however, has not been tested before. The NLR study has examined accident and movement data for 557 International Civil Aviation Organisation-graded "principal" airports, collating an accident sample of 131 hull-loss occurrences on the approach and landing phase during the ten years to 1993. The study has now produced a relative-risk analysis of approach aids and approach categories.
The report, presented at the FSF's European Aviation Safety Seminar in Amsterdam, Netherlands, on 28 February, contends the following points:
on average worldwide, precision approaches are 5.2 times safer than non-precision approaches;
if there is no terminal-approach radar at the airport, the risk increases by a multiple of 3.1;
if there is high terrain in the neighbourhood, the risk increases by a factor of 1.2 (NLR notes that the data for the latter were statistically marginal);
lack of a broadcast airport-terminal information system or meteorological report increases risk by a multiple of nearly four;
with no published standard terminal-arrival procedure, the risk increases by a factor of 1.6.;
with no approach lights, the risk increases by a factor of 1.4.
Source: Flight International
