Jet A .. Do we have a winner?

With the Continental take over of Thielert as well as licensing from SMA it was to be expected that they finally will do something. Still I think the competition is not fierce enough for things to develop as fast and as cost relevant as it could be.

What I wish for is that Lycoming would finally certify it’s diesel engine for civil applications as well. Usually, if Conti and Lycoming are competing, the end result is much better for the customer.

I am a bit sceptical about that. The way to do this is to increase the manifold pressure considerably. RPM cannot be touched because it’s a direct drive and you can’t turn the prop faster than 2500 with today’s noise abatement rules really. I am sceptical because already today the turbochargers (which deliver the MP) are underpowered and the engine quickly runs out of power at altitude (critical altitude FL100).

I believe the way forward for SMA and the other diesels is to combine turbocharging with supercharging. This is probably what SMA are going to do and it is the concept that Prof. Junkers used in the 1930s for the Jumo 2-stroke diesels.

Or maybe using an electric turbocharger…

That would be a supercharger in my terminology

Turbocharger: extracts energy from the exhaust
Supercharger: driven by the engine (whether directly or indirectly doesn’t matter)

Electric superchargers are a very interesting topic of research. They are starting to be used on modern car diesel engines. I would assume they find their way into aviation much later because the simple mechanical drive of a supercharger is easier to construct reliably and the industry has been doing it for decades. There are several STCs out there to add superchargers, e.g. for the O-470 C182.

Or maybe using an electric turbocharger…

Exactly. This could be combined with an electric motor coupled to the crank shaft, similar to what is done in F1. – Or stop fooling around with these super complex and heavy systems altogether and install one of these (180 kW turboprop at 55kg).

…and install one of these (180 kW turboprop at 55kg).

Once they make them with the noise emission of a piston engine and the efficiency and specific fuel consumption of a turbocharged diesel engine, they will have the market all for themselves. But unfortunately this is only going to happen in a parallel universe because the laws of physics in our universe are against it.

Once they make them with the noise emission of a piston engine and the efficiency and specific fuel consumption of a turbocharged diesel engine, they will have the market all for themselves.

True, but only if fuel efficiency and noise is a factor. There are lots of places where the cost of Jet-A is almost nothing, and AVGAS is non existent. Noise emission is only a factor for densely populated areas in Europe, and is more governed by the fact that noise emission rules exist, rather than noise as a real problem. Besides, a turboprop is only noisy when taxiing on the ground. In the air, there is only propeller noise which is proportional to HP in any case.

…There are lots of places where the cost of Jet-A is almost nothing,

Lots maybe now, but less every day. In twenty years from now this will be an issue everywhere, worldwide. This is why the engine manufacturers are not seriously developing small gas turbines – because it is only going to be a short term market. I remember that 20 or 30 years ago, most newly built ships were powered by gas turbines. Now diesel engines only (military vessels apart, but they don’t have to pay for their fuel yet). And the heavy oil used by ships is a lot cheaper than Jet fuel yet it makes no sense any more wasting 50 percent of it in a turbine.