Fuel economy - piston vs turboprop vs jet?

Question

For a passenger aircraft of a certain size, which engine type is the most economical? (comfort or enroute time does not matter)

For example, I have a 100-pax plane flying an 1000 nm route. How much fuel would a piston (like DC-6, Connie), a turboprop (like Dash 8Q4, Vanguard) and a jet (like 737, A318) typically burn? Which is the cheapest? (mind that they use different fuel types)

Answer 1

My money is on the turboprop. The small profile of the engine creates much less drag that most piston engines, especially the fuel hog Connie that you mentioned, overall better fuel controls, temp datum, variable pitch props that adjust to varying loads. Piston engines require constant mixture adjusting, turbos do this automatically, Go turbo and hydramatic props!

Answer 2

In physics terms prop(piston and turboprop) are much efficient compared to jets because they produce thrust accelerating a larger mass flow. In fact the bigger mass flow you accelerate for a given thrust, the less you must accelerate that flow, so less energy is wasted.

But about airliners you must consider the number of passengers transported(you can divide the consumption for the number of passengers).....and also the time is important(you can't stay in the air 5 hours instead of 1hour for the same flight).

Turboprop planes are quite cheap comprared to jets in short range, but turboprop are also slower so in short range the difference in time will be quite little(1 hour flight instead of 40 minutes can be accepted), but in longer ranges grows(10 hours instead of 6:40 hours)...

And you must consider that the plane produces much profit if flyes more flights...this is the reason why usually turboprops don't fly at their maximum range speed(minimize the fuel compsuption to fly from A to B) but usually they fly near their max cruise speed.

Answer 3

I agree with all of the answers given above but you should also consider that the faster a gas turbine engine runs the more efficient it becomes nm/pl so it also comes down to the type of gas turbine  engine and the speed it's running at, should also point out that if it's a supersonic aircraft it would need to use reheat to break the sound barrier and reheat makes the engine burn approximatly 150% more fuel. so not that economic!

cost wise avtur is much cheaper than gasoline and slightly cheaper than avgas used in piston engines so if it's cost the piston engine would be hugely more expensive as stated in an earlier answer both for the cost of the fuel and maintainance.

the turbo prop however can give a much higher thrust output than a pure gas turbine engine of the same size but cant reach as high a speed.

hope this was of some help.

Answer 4

The total amount of fuel the aircraft burns is not the relevant question...  The important factor is the COST of moving X number of passengers Y miles.  A Cessna 172 may burn much less fuel per mile than a 737, but how much money  does it really cost to move ONE passenger seat (or 170 lbs of cargo) from point A to point B?  

You'll have to do the math on each airplane you want to compare, but I think you'll find that turbo-prop aircraft are the most efficient for short hauls, while passenger jets like the DC-9, or the 737 are the most efficient people movers for longer flights.

Answer 5

Regardless of anything else. Weight uses energy. So the heaviest will use the most fuel. While the lightest will use the least.

Answer 6

You have them in correct order. Least fuel to most. However you did not take into account altitude and speed. Time is money. And maintenance on a piston radial engine can really be expensive spark plugs all over the place. Typically turbo prop with three or four moving parts is better. Turbo Jet bi pass engine even better than turbo prop one moving part engine in terms of speed altitude and maintenance costs. The latter two run on kerosene.

Answer 7

saw a documentary about this exact thing the other day. Because of the propulsion system of a jet engine it can fly further on the same amount of fuel than a prop driven or turboprob engine because the jet engine produces more thrust wfor the amount of fuel used... all loads and conditions being equal

Answer 8

well most of the answers summed it up. All I gotta say is distance and speed is a factor in fuel. I believe the turboprop is fuel efficient on short journey's, and the large aircrafts for long flights.