The exercise in deciding how single-engined aircraft can be made safe for public transport in IMC should trigger other improvements

The European Joint Aviation Authorities is nearing the final hurdle in the arduous decision-making process on whether to allow commercial single-engine operations in instrument meteorological conditions (IMC) and at night. Some JAA states have already approved it, anticipating and applying the constraints that the final JAA requirements (JAR) will demand.

The process leading to the final notice of proposed amendment (NPA) that has just been published for final comment has been typically European: ponderous, argumentative, incredibly long, and almost unbelievably thorough. In the end, however, the NPA is impressive even if some might reckon it to be overly pedantic. The levels of systems redundancy required, the operational safety requirements demanding additional highly capable on-board equipment, were prompted, one suspects, by those who still oppose the concept of single-engine commercial instrument flight rules (SEIFR). They may well have hoped that the demands went so far beyond that required for a traditional piston-powered twin that it would price SEIFR out of the skies.

Safety should indeed be required not just to stand still but to advance, taking advantage of improving technology and new safety systems. It is valid to argue - as SEIFR's proponents have successfully done -- that the modern turboprop-powered machines that are the subject of the NPA have a far better safety record than most piston twins in service today that are allowed to operate in IMC as air taxis or commuter aircraft. But because older piston twins have such marginal performance after suffering an engine failure - especially at take-off, in the early climb or during a go-around - it is definitely not valid to argue that the modern singles should only have to achieve equivalent safety as these, because that is patently not good enough given the high rate of piston engine power loss events compared with that of a modern turboprop. Indeed, no-one did try to argue this, but it does raise the question of whether more should be done to advance the safety of aircraft technically immunised by grandfather rights from the requirement to improve. The reason for maintaining grandfather rights for previous generation aircraft is mainly to do with fairness to the industry, but one of the assumptions on which the grandfather philosophy is based is that the older technology will be retired within a reasonably short time. But it is not working like that in practice, either in general aviation or in the airlines. In the airline industry, safety is gradually being advanced - under the JAA if not under the US Federal Aviation Administration - by requiring that new versions of old types of aircraft such as the Boeing 737 meet "equivalent safety" standards with more modern designs as determined by the JAA, even if they do not comply with the letter of the law that applies to new types.

There is a case for examining whether, instead of improving safety by requiring uneconomically expensive new equipment to be fitted in old aircraft, a system should be developed for limiting - possibly at the time an old aircraft comes up for its annual certificate of airworthiness renewal - what a veteran type or individual airframe is licensed to do in today's world given higher safety expectations by the travelling public, including air taxi users. Consigning old aircraft to cargo operations only would be one option available. The problem would be in deciding the criteria for limitations.

A glance at the list of compulsory requirements, in systems redundancy and operational capability terms, for SEIFR types should trigger questions about the staggering contrast in all respects except engine redundancy with the requirements for a grandfathered piston twin, which requires none of them. These include: two independent engine control systems; airborne weather radar; sufficient passenger oxygen in pressurised types to allow descent to be made at best gliding speed from the maximum certificated cruising altitude; an area navigation system programmable with the positions of aerodromes and emergency landing sites; a radio altimeter - preferably a system which provides an analogue closure rate display; a battery with sufficient power to provide - during the descent from maximum cruising altitude - flight instruments, the area navigation display, an attempt at engine start, radio altimeter throughout descent, a landing light to operate during the last 200ft, a pitot heater, and a means for keeping the windscreen clear.

If it does not make economic sense to invest in keeping a veteran public transport aircraft's safety up to date, regulators should consider whether it should retain all its operating rights.

Source: Flight International