Sir - The extreme enthusiasm for reduced vertical separation minima (RVSM) demonstrated by United Airlines' Mark Hurston (Letters, Flight International 16-22 April, P40) is by no means universal. Has the cost of qualifying certain aircraft types for RVSM been included in his, or anyone else's, projections?

Just before implementation of North Atlantic RVSM, in attempting to have the height-keeping performance of suitable aircraft measured (often involving re-routes which would not otherwise have taken place), the height-monitoring unit was found to be unserviceable as often as not, requiring a repetition of the exercise. Some aircraft in extensive use required upgraded air-data computers to qualify and other types will require work on the pitot-static systems and/or the fuselage surface in the area of the static ports before qualification will be possible. What sort of fuel savings will be required to pay for all this, and in how many years?

Will there be any greater chance of stepping up to a more advantageous level while on the North Atlantic Organised Track System with the increased volume of traffic than there was before RVSM were introduced? I very much doubt it.

RVSM were introduced to increase the allowable volume of traffic in North Atlantic airspace. This was a perfectly laudable aim and I see no reason, therefore, for dressing up the project with the promise of huge fuel-cost savings, unless the idea was to counter the airlines' objections about the high cost of compliance.

Norman Foster

Duxford, Cambridge, UK


Source: Flight International