After two decades of European resistance to permitting commercial single-turbine operations at night or in instrument meteorological conditions (SET-IMC), the European Aviation Safety Agency is drawing up the final regulation that would approve it across all contracting states.

For small or isolated communities that need reliable air links, air taxi services and would-be operators of commercially marginal scheduled air services, this looks like excellent news. Continual disappointment over the years, however, means some operators may wait for the final rule before making any business expansion decisions. Others, however, are starting to prepare for the new status quo.

For manufacturers of appropriate aircraft types, the permission could herald a sales bonanza. The General Aviation Manufacturers Association (GAMA) hints as much in its interpretation of the figures backing up EASA’s notice of proposed amendment (NPA) on commercial SET-IMC: “The NPA lays out the order of magnitude difference between the number of single-engine turbine aeroplanes in commercial operations in Europe and the United States. According to this analysis, there were 13 single-engined turbine aeroplanes in CAT [commercial air transport] operation in Europe in 2013, whereas in the United States – which is similar in size, overall population, and economic activity – there were 673 aeroplanes in Part 135 CAT operations. These statistics, by themselves, point to an unmet demand for several hundred aeroplanes to support overnight cargo delivery, aeromedical flight operations, and passenger operations to under-served communities across Europe.”

EASA, in its published opinion on the subject, released in November, acknowledged the anomalies resulting from Europe’s failure to approve CAT SET-IMC, including: some European states already allow such operations conditionally; the International Civil Aviation Organisation has published standards for CAT SET-IMC; many other states including the USA and Canada allow it; economic and social issues are involved because permitting CAT SET-IMC may allow low-density routes to be served where at present they are not viable. EASA then states the objective of the present rulemaking: “The specific objective is to allow single-engined turbine aeroplanes, meeting specified powerplant reliability, equipment, operating, and maintenance requirements, to conduct CAT SET-IMC operations.” The safety justification is simple: “The proposed changes are expected to maintain the safety of CAT operations by allowing, based on proportionate requirements, the operations in IMC and/or at night of single-engined turbine aeroplanes better equipped and with a higher engine reliability than some currently operated twins.”

But winning SET-IMC approval in Europe is a challenging process. The task for the SET operator community is rather like that faced by twin-engine jet operators 30 years ago when they were seeking approval for extended-range twin-engine operation - usually known as ETOPS - over oceanic and wilderness areas. Approval involves comprehensive operational requirements for crew training, capability and experience, flight planning considerations, enhanced maintenance programmes with tighter minimum equipment list specifications, and aircraft type suitability.

Obvious aircraft candidates include Cessna’s Caravan series, Daher’s TBM series, the Pilatus Aircraft PC-12 series and Quest Aircraft’s Kodiak. These, however, would normally leave the factory without all the additional technical requirements for SET-IMC-cleared airframes unless they were buyer-specified. These include twin independent electrical generation systems with powerful emergency back-up, weather radar, radio altimeter, two independently powered attitude indicators and smart ice-detection systems – and, all will require a powerful landing light to enable the pilot to carry out a forced landing on flat terrain at night. Also, the types that can fly at heights demanding pressurisation – if they are to use that capability in commercial operations – will need supplemental oxygen to sustain crew and passengers during an efficient engine-out glide profile from maximum operating altitude, assuming descent in areas with demanding terrain.

Pilatus Aircraft, maker of the PC-12 which, arguably, stands most to gain from the larger potential market the new rules would usher in, declines to comment on its prospects; likewise Cessna about its Caravan series. But at a recent discussion at the British Business and General Aviation Association (BBGA) on the proposed CAT SET-IMC rules, Edwin Brenninkmeyer, chief executive of UK Pilatus distributor Oriens Aviation, chaired a session that voiced considerable enthusiasm for the prospects once the approvals come through.

At the same meeting, Geoff Parker, head of the UK Civil Aviation Authority's (CAA) flight operations group, revealed he had already held two meetings with EASA and advised the gathering the CAA would use its “exemptive powers” to allow SET-IMC flights by as early as October, adding the UK to the list of European states that permit them under exemption. Brenninkmeyer voiced the opinion EASA approval “is not a question of if, but when,” adding operators can use the EASA endorsement to start preparing manuals for approval in readiness for public charter flights. As Aircraft Owners and Pilots Association UK chief executive Martin Robinson points out, Eurocontrol is already working on developing new low-level routes to accommodate these aircraft.

Daher, the France-based maker of TBM fast single-engined turboprop business aircraft, is rather more cautious about the size of the market boost that the proposed rule would bring, pointing out the choice is for the operators to make, because the manufacturers can, if asked, deliver whatever capabilities are specified. But, it adds, if the final rule also demands pilots be unrealistically experienced and have to undergo specialist recurrent training for commercial SET-IMC operations, the proposition may be commercially unviable for some operators.

The TBM series, as six-seaters, are more suited to the air taxi business than low-volume commuter schedules, but Daher reckons the charter market will definitely get a boost from the new rules, so whatever conditions are attached to the final rule, Daher observes it is better to have a demanding clearance to operate than to be grounded in IMC come what may.

The critical component in the draft EASA rule states: “In Commercial Air Transport (CAT) operations, single-engined turbine aeroplanes shall only be operated at night or in IMC if the operator has been granted a SET-IMC approval by the competent authority.” The requirements for approval – both technical and operational – are extensive and detailed, but because of advances in turbine engine reliability, engine health monitoring systems, and satellite navigation systems and their displays, they are achievable; 20 years ago perhaps they were not. What is more, it had become increasingly obvious old twin piston-engine aircraft which retained the rights to carry out CAT SET-IMC were becoming less safe than the latest generation of single-turbine types.

US-based Quest aircraft, builders of the Kodiak utility turboprop, points out many countries “operate the same type of specifications for SET-IMC operators, and Quest does not believe this makes it unviable.” It points out the Kodiak is approved for US Part 135 operations, “and this will carry over to our EASA certification”. Like all the other stakeholders, it says it is expecting the final EASA rule to be implemented in the first half of 2017.

Several operators in Europe are already flying aircraft and crews compliant with the demanding technical and operational requirements EASA expects to formalise, but at present they are cleared for operations under national exemptions for limited SET-IMC operations. These operators are based in Finland, France, Norway, and Sweden. The additional technical and operational standards for SET-IMC are no surprise to anyone, because EASA did not invent them. In fact the ICAO published them more than a decade ago (Annex 6, Part I, Amendment 29). But even for these Finnish, French and Scandinavian operators, according to GAMA, an EASA mandate will hugely improve their potential commercial viability. GAMA states: “Their main commercial obstacle has been the uncertainty of operating under an exemption. They will now instead be in a position to lay out firm business plans and access the necessary capital to build their businesses.”

One of the operational conditions for SET-IMC operators looks as if it will be a higher standard of training for its pilots than those cleared to fly daylight or night-time visual flight rules at present. They will not only require a full instrument rating – which would be a minimum for IMC operations, but specifically have to be tutored in the demanding business of recovering an aircraft at night or in IMC in the event of an engine failure, including over high terrain.

This is potentially a problem. Typically, pilots flying single-engine night freight operations, for example, are at the beginning of their careers and will not have that kind of experience, and pilots who have gained the specified higher levels of expertise would normally be looking for a more lucrative job, or for a level of pay that would persuade them to stay where they are. GAMA comments: “We expect market forces to engage to ensure that operators have the necessary access to training and, if applicable, access to simulator devices.” Greater access to capable but low-cost flight simulation training devices for SET types would certainly make a positive difference, and if GAMA is right, a demand for such training would lead flight training organisations to invest in them.

The proposed EASA supplements to existing regulation, at this stage in the drafting process, include these requirements for the approval of a European operator to carry out CAT SET-IMC operations:

·The pilot shall have a minimum 700h flying time, including 400h as pilot in command, 100h in IMC and 40h of multi-engine operation.

·Operators are to ensure operations are planned only in areas or along routes where surfaces are available to permit a safe forced landing, and the aircraft should be capable of reaching these.

·An acceptable level of turbine engine reliability achieved in service by the world fleet for the particular airframe-engine combination, and an enhanced engine health monitoring and maintenance programme.

·The flight crew composition and an appropriate training/checking programme for the flight crew members involved in these operations must have been established; and operating procedures must have been established specifying equipment to be carried, flight planning, normal procedures, contingency procedures, including those following a propulsion system failure, forced landing procedures in all weather conditions, and procedures for monitoring and incident reporting must be established.

·Equipment and systems must include: two separate electrical generating systems, each individually capable of supplying adequate power to all essential flight instruments, navigation systems and aeroplane systems required for continued flight to the destination or alternate aerodrome; two attitude indicators, powered from independent sources; for passenger operations, a shoulder harness or a safety belt with a diagonal shoulder strap for each passenger seat; airborne weather-detecting equipment; in a pressurised aeroplane, sufficient supplemental oxygen for all occupants to allow descent, following engine failure at the maximum certificated cruising altitude, at the best range gliding speed and in the best gliding configuration, assuming the maximum cabin leak rate, until sustained cabin altitudes below 13,000ft are reached; an area navigation system capable of being programmed with the positions of landing sites and providing lateral guidance to the flight crew to reach those sites; a radio altimeter; a landing light, capable of illuminating the touchdown point on the power-off glide path from 200ft away.

·An emergency electrical supply system capable of providing power – following the failure of all generated power – to all the following: the essential flight and area navigation instruments during descent from maximum operating altitude after engine failure; the means to provide for one attempt to restart the engine; if appropriate, the extension of landing gear and flaps; the use of the radio altimeter throughout the landing approach; the landing light; one pitot heater; an ignition system that activates automatically, or is capable of being operated manually, for take-off, landing and during flight; a system for ensuring the pilot has visibility when in visible moisture; a means of continuously monitoring the power train lubrication system to detect the presence of debris associated with the imminent failure of a drivetrain component, including a flight crew compartment caution indication.