Sir - Capt Jim Passmore, head of safety at British Airways, appears to have confused "minimum descent altitude" (MDA) with "decision altitude" (Letters, Flight International, 20-26 March, P100). There is a significant difference between the two, and to confuse them is hardly conducive to flight safety. If he is using BA terminology, it is unlikely to be helpful to use ones so close to standard International Civil Aviation Organisation terminology.
Perhaps Capt Passmore has spent too long, on the flight decks of aircraft, which have more sophisticated flight-management systems than the vast majority of aircraft. He is, therefore on dangerous ground in telling the rest of us how to fly a non-precision approach.
His letter further advocates departure from published approach-procedures. Guidance in the UK AIP (RAC 4-2-4) on the descent rates states that, at RAC 4-1-1: "PANS-OPS stresses the need for flight-crew and operational personnel to adhere strictly to the published procedures...to achieve and maintain an acceptable level of safety in operations."
Capt Passmore's non-precision approach poses risks. If air crew are to calculate the nominal glide-slope, they may get it wrong, given that a non-precision approach is a time of relatively high stress on the flight-deck. Also, the lower winds may be stronger or weaker than expected. If stronger, the aircraft will reach MDA short of the missed-approach point (MAP), and will either go around from an approach which could well have resulted in a perfectly safe landing, or will be flown level until reaching MAP, exactly what Capt Passmore wishes to avoid. If weaker winds prevail, the aircraft will reach the MAP too high. Either way, the probability of unnecessary go-around is increased, with a decrease in flight safety.
Name and address supplied
Source: Flight International
