Piston-Engined Aircraft

[Dekan]

I live close to a small airport.

 

Small planes flying in and out of the airport can often be seen in the sky. They're slow straight-winged things with propellers. No jet-engines. Not even turbo-props, to judge from the engine noise. Just piston-engines. Like in planes from the 1930's.

 

I wonder why these piston-engined anachronisms persist in our 21st Century skies. Isn't it a bit like seeing horse-drawn hansom-cabs still running around our city streets?

 

Couldn't the piston engines be replaced by small turbofan jet-engines. Like the engines used in cruise missiles. These engines are light, compact, fuel-economical, and give high speed and long range.

 

Such modern engines would seem ideally suited to light aircraft.

 

Yet many light aircraft still use the old-fashioned piston engine - is there a good reason for this?

Edited May 17, 2011 by Dekan

[swansont]

How much does a piston engine cost as compared to turbofan?

[Dekan]

How much does a piston engine cost as compared to turbofan?

 

 

Would a turbofan engine have to cost much more than a piston engine?

 

The piston engine is very complicated, with its cylinders, valves, spark-plugs.

 

Such complexity must cost a lot to manufacture. Compared to the relative simplicity of the turbofan.

 

I'd like to see the relative costs.

 

 

 

[Gweedz]

I'm not into airplanes (but I know about engines), just some suggestions:

 

A turbofan may have less parts, but due to speed and tolerances each part must be built with higher precision and better materials. Equals more cost.

 

Small airports are more likely to have mechanics and tools suited towards older, established technology. (Same idea like that town in the middle of nowhere may not have a qualified mechanic or tools to service your 2012 Mercedes).

 

Is a turbofan more reliable? (I really don't know, but I'd rather a couple spark plugs fail in an 8 cylinder engine, than a couple fan blades in a turbofan).

 

Are most of the planes you see recreational planes where performance, speed, fuel economy, and range are not as important as a commercial airplane? For recreation some people like driving their classic cars, even when their daily driver vehicle is much better in all aspects.

 

Is a turbofan too noisy for small airports near residential areas?

 

Just some ideas, but I think the biggest reason is cost - for the engine, repairs, maintenance. With little added value to the operator/owner.

[insane_alien]

while you may think piston engines are more complicated, well they're not.

 

there are plenty of mechanics who can service piston engines, the parts are mass produced, the technology is old and well tested etc. etc.

 

small jet engines are quite complex and have a high maintenance upkeep. the principle is simpler, but the excecution is not.

 

incidentally, you do get a few gas turbine prop driven aircraft these days. still not too common though.

[Gweedz]

Also, maybe it's easier/cheaper for a small airport to get regular fuel vs av gas.

[InigoMontoya]

I'm curious about your "fuel-economical" claim. True, modern turbofans are more efficient than turbojets or even the turbofans of a decade or three ago... But I've never heard anyone claim that they beat piston engines for efficiency. On that note, it is worth noting that the first plane to go round the world unrefueled was a piston job...even though the builder had the resources to do it as a turbofans/turboprops. One has to think he had a reason.

[CaptainPanic]

Piston engines are really cheap. They are used in nearly all the cars, so the production volumes is many millions per year.

 

To give an example of the difference in volume:

- The most sold aircraft is the Cessna 172, of which 43,000 were build so far.

- The most sold (single model) car is the Volkswagen Beetle, of which 21,529,464 were sold.

 

We're basically dealing with a production volume which is 500-1000x larger for cars than for airplanes. And that's why the most sold airplanes actually use engines that are quite like car engines.

 

I'm sure that if turbo props or jet engines were build by the tens of millions per year, they would also be a lot cheaper.

 

[edit: forgot links for my claims - inserted them now]

Edited May 18, 2011 by CaptainPanic

[Klaynos]

In my experience of general aviation (light aircraft) they are all quite basic piston engines, very cheap upkeep. Quite a few are actually motorbike engines as they are small and light.

[Skye]

The main reason is that different engines have differing fuel efficiencies in take off/landing and cruising. Piston engines are more efficient at the former, turbofans at the latter. Turboprops are in the middle. So piston engines are used for short ranged, turboprops for medium distance and jet engines for longer distances.