The Engine Revolution is almost upon us

Back in the early 1990s I remember talking to a group of disillusioned pilots. They were complaining that while the engines in their cars had moved on, what they referred to as the LyCosaurus lumps in their aeroplanes hadn’t.

For the bulk of the General Aviation fleet you could make the same argument today, but take a step or two backwards to gain a bit of perspective and you might just be able to see changes starting to happen. 

There have of course been many new, and sadly, false dawns. Among them, a French company, SMA, used Renault F1 engineers and many many tens of millions of euros to design and certify a four-cylinder diesel engine. Textron was so confident that this would work, that it cancelled the production of avgas-fuelled C182s in favour of the Jet A fuelled SMA.

A couple of engine failures during testing saw the project quietly dropped and avgas Lycomings were once again hung on the front of the C182. Maule too had a go at developing an SMA engined aircraft, but that project also found its way to the big hangar in the sky…

Earlier still, I remember taxying out in an ARV-powered by a multi-fuel capable Wankel engine only to make it as far as the hold before a technical issue had us returning to the hangar. Although a development of that engine found a place in some sailplanes, it never became the wonder for the two-seat fleet that many had hoped. 

There have been some wins. Thielert successfully certified a version of a Mercedes engine to bring frugal diesel power to GA. It wasn’t without its troubles, early reliability issues slowed its adoption, and the jailing of its founder for financial irregularities did nothing for the brand.

However, a lot of engineering work, significant development, a renaming and an eventual change of ownership (it is now owned by Continental Aerospace Technologies) finds the Centurion alive and well, although perhaps not retrofitted in as many PA28s or C172s as was predicted. Diamond Aircraft, the big early adopter of the Thielert engine, launched its own new engine line, initially also a converted Mercedes motor, and now the majority of its new aircraft are powered by their Austro engines. 

And then there’s Rotax. I remember the introduction of Diamond’s Katana to the UK flight training industry in 1994-ish. It was a fun little frugal aeroplane, but the high-revving four stroke 912 with its gearbox meant that for many it was anything but love at first flight. It took a while for the conservative (small c) wing of the aviation establishment to come to terms with the engine, but over the years it gained a few extra horsepower and a growing reputation for frugal reliability.

The super-sweet 100hp fuel injected 912iS was recently joined by the 915iS which offered a temporary 141hp and 135hp max continuous, and at Sun ‘n Fun, the company planted a big flag in four-seat territory with its 916iS/c – capable of delivering 160hp for three minutes before turning itself back into a 915 with its continuous 135hp. Full take-off power is available all the way to 15,000ft. 

However, it’s not all sweetness and light. A new 916 is going to cost you north of £40k, and I’m not sure that the fuel consumption will be very much less than a hard working O-320 or lumbering 0-360.

The weight will of course be much lower, but that means that any retrofit applications are either going to need extra long engine mounts and cowls or extra weight in the nose to keep those CofGs in the right place. 

That said, all things all things considered, the combination of a fine Rotax family of engines, the 600kg microlight rules, and a lighter touch in certified aviation, will I think see a gradual evolution away from the heavier older designs, at least until someone delivers battery technology that starts to come close to the energy density you find in avgas and mogas.