Could large non-turbine aircraft be much more fuel efficient than current jet / turboprop transports?
Large non-turbine (prop) aircraft were common during WWII and for a short time after. Could advances in materials and design make a non-turbine transport aircraft practical?
I understand there would be a lot of consumer resistance, and practical factors ( lower speed being one ) which might prevent it, but was curious as to how much fuel could be saved by a properly designed non-turbine transport aircraft?
Efficency tradeoffs would be payload, speed, size limits, maintenance ?
Would these tradeoffs ever make sense if fuel prices rocketed?
I am aware of benifits of turbines, but was wondering, in regards to fuel burn for a given mission, if you were willing to go slower, smaller etc. what % fuel savings could be achieved using for example a diesel engined aircraft.
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Comments on Could large non-turbine aircraft be much more fuel efficient than current jet / turboprop transports?
The big piston engined aircraft burn a huge amount of very expensive, super-high octane, leaded gasoline, and can use gallons of motor oil during a long flight.
Imagine how much time and expense it would take to overhaul four or six 36-cylinder radial engines after every 1000 hours of flight, as opposed to two turbine engines every 6000 hours.
Turbine engines are much more efficient, the fuel costs less, and maintenance costs are also considerably less that piston powered aircraft.
The question as stated is impossible to answer definitively, and needs to be refined…
Depends on how you define efficiency.. On a horsepower per pound of fuel burned, turbine engines burn more fuel for a given amount of power output than reciprocating (piston ) engines, which (in addition to their high acquisition costs) are why they are rare in light airplanes…
HOWEVER, they can produce more power, allowing more passengers to be carried, generating more revenue, making each flight more productive..
Piston engines are already more efficient than jet engines. Unfortunately, they have other problems that outweigh their efficiency for most applications.
Piston engines are far less reliable than jet engines and gas turbines. Until jets came alone, engine failures in flight were almost routine, and airplanes had to have plenty of engines just to be sure that they’d make it through a long flight. Piston engines are also much heavier than jet engines for the same horsepower. They produce more vibration as well. They are more complex in design (which is a key reason why they fail more frequently).
All of this works against piston engines. And there aren’t too many other competitors for jets and gas turbines. Rotary engines are simpler and more reliable than piston engines, but they also are less efficient, so they can’t help. Diesel engines are more efficient but they are heavier, too. Water cooling would probably improve efficiency, but that has problems of its own, especially in aviation.
Not only that, but certifying a new engine design is tremendously expensive, and the market for non-jet engines is small. That’s why piston engines on small prop airplanes have stayed essentially unchanged for decades.
The one sure thing in the world is change, and so there may be new powerplants one day, but for the foreseeable future, jets in some form are way out ahead of the pack.