You claim (Flight International, 4-10 February) that single engine instrument flight rules (SEIFR) is a wonder cure for general aviation. It is not.

The accident rate met by single-engined turboprops remains double that achieved in service by the B-N Islander twin.

Our concern is that this notice of proposed amendment alters the balance between design and operational codes. Operational requirements will allow carriage of nine passengers with zero continued flight capability following a powerplant failure, while the design codes continue to require a similar capacity twin to meet penalistic engine-out performance. This lop-sided approach to airworthiness means that a twin is now penalised for providing continued flight capability. The penalty is startling; as a "single", B-N's Defender would see a 40% payload increase and still have a better power/weight ratio than the most popular single-engined turboprop.

It is also a myth that SEIFR will make GA cheaper and more available. New single-engined turboprops cost from $1.5 million - not a value assigned to most piston twins. While newer aircraft require lower maintenance, the only real factor to offset the higher capital/engine overhaul costs is the difference in the price of JET A1 and highly taxed 100LL AVGAS.

This will be addressed by the adoption of diesel engines - that really is a cure for European GA.

Mark Wilson Managing director, Britten-Norman Aircraft, Bembridge, Isle of Wight, UK

Source: Flight International