Mark Wilson, Head of Flight Engineering at Britten-Norman Ltd writes: In the resurgence of General Aviation (GA) in recent years the light utility sector has seen expansion of the single engined aircraft market; this may cause some to question the future of the light twin. However, I feel confident that the future of twin engined GA is healthy and that given certain developments in the next few years the market can be expected to expand. \rTwo areas dominate the agenda: the issue of Single Engined IFR commercial operation (SEIFR) and new technological developments, primarily powerplant. With regard to the former, it can be expected that I am against the use of SEIFR. My objection is not simply parochial, rather it is due to concern with the statistical basis upon which the SEIFR case is made, the distortion such rule-making brings to international airworthiness and the likely effect on fleet make-up.\rStatistically I would say that SEIFR is not proven; everyone has their own set of statistics; I would point to a UK Department of Trade and Industry survey that shows a twin turbine installation having in-flight shut down rates of only about 7 per cent, better than for a twin piston installation; put alongside the Australian authorities' view that engine failure in a single engine aircraft is four times more likely to end in a fatal accident than in a twin and I think sufficient doubt creeps into the argument.\rWith regard to airworthiness legislation, SEIFR will mean that carrying up to nine passengers can be done with no continued flight capability following engine failure, whereas with ten passengers the regulations are 'commuter category' and therefore not far off large transport aircraft level. \rIn addition it means light twins are penalised - why should the BN2T-4S Islander have its max weight limited by one engine inoperative performance? If it were exempted from these requirements it could structurally carry an extra 680 kg in payload and still have a better power to weight ratio than the most popular single engined turbine!\rMy final concern on SEIFR is that the fleet impact is likely to be more in replacing turbo-props than piston aircraft simply due to the cost aspects - in which case the arguments in terms of safety against 'aged' piston twins fall apart. I feel single engined commercial operations have their place, but that they must not be considered in isolation. I therefore see the light twin as a continuing important sector of the GA market.\rThe role of the light piston engined twin will be further enhanced by the adoption of some of the new technology that is beginning to penetrate the smaller four-seater sector of the market. \rThe advances from programmes such as AGATE are bringing features to light aircraft that make them more usable than ever before. In particular, powerplant develop-ments are of major interest. These technological developments are aimed at the mass market of the C172 and PA-28 etc but are equally appropriate for light twins.\rBritten-Norman (BN) are currently trialling new generation propellers with Hartzell and have been in liaison with all the primary engine manufacturers regarding new powerplant technologies. In particular the development of a compression ignition (diesel) multi fuel burning engine is of great interest - the scarcity and cost of AVGAS is a growing problem world-wide. \rWithout exception these new powerplants will greatly reduce noise and be more fuel and cost efficient. What is important is that these engines are almost all rated at 300 hp and below - as such the only way they can apply to a true nine passenger aircraft is with a twin.\rSo with a proper integration of single and twin (or multi!) engined operating rules and the advent of new powerplant and avionic technology I see a return in the demand for the light twin. With a range of piston and turbo-prop aircraft BN are confident in the future for multi engined light aircraft.\r- Mark Wilson, Head of Flight Engineering, Britten-Norman Ltd