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I've read that turbo-prop aircraft are more efficient than jet-aircraft. Browsing this Wikipedia page it looks like in general, jet airliners burn less fuel per passenger. I imagine this is due to jet aircraft typically carrying more people, and flying longer in cruise. Is there some fundamental reason why traditional propeller designs couldn't be scaled up to 150+ passengers and trans-oceanic ranges? If it was possible, would air travel become substantially more efficient per passenger?

Edit: Perhaps a better phrased question would be: are turboprop aircraft always more efficient, regardless of airframe size? Or is there some regime where modern turbofans take over? I'm specifically asking about fuel efficiency (i.e. ignoring noise / speed).

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    $\begingroup$ With great thrust comes great MTOW. $\endgroup$ – DeepSpace Jul 28 '16 at 6:41
  • $\begingroup$ It all boils down to cost. Can an airline make enough money from passengers using their turboprop 8 hour routes when a jet powered aircraft can cover the same route in 4.5 hours? $\endgroup$ – Mike Brass Feb 5 '18 at 0:38
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why traditional propeller designs couldn't be scaled up to 150+ passengers and trans-oceanic ranges?

Well, they can. One of the more fundamental problems is extracting enough power from turboprops, that is, building a large turboprop engine. Turboprops are necessarily geared, and designing a gearbox to pass such an enormous power and torque is a big challenge. In the Tu-114/Tu-95 engines (which were the most powerful turboprops ever built), the gearbox weighed more than the rest of the engine. After some point, such gearbox will eat up all the benefits.

The same applies to the propeller: it is quite difficult to convert high power to thrust while maintaining a reasonable size.

The new generation geared turbofans potentially offer some of the advantages of turboprops: they need less gearing, yet their fan has much higher thrust density.

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  • $\begingroup$ Cool, thanks for the info! $\endgroup$ – mike Jul 28 '16 at 11:44
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There are a number of problems:

  1. Speed

Traditional Propeller aircraft are much slower than jets. Propellers decline in efficiency as they increase in speed.

  1. Noise

For the same thrust, propellers are noisier then jets.

  1. Development Cost

There have been efforts for propellers but so far they have not been justified by economics.

GE36 Engine

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