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General Science => General Science => Topic started by: Anders Strandberg on 02/08/2010 11:30:01

Title: Why don't we use turboprop planes?
Post by: Anders Strandberg on 02/08/2010 11:30:01

Anders Strandberg  asked the Naked Scientists:
   
Hello,

How much less warming do you get from emissions by turboprop aeroplanes instead of jets? They fly slower and lower so several factors.

Why don't we use more turboprop within europe, is jetfuel so cheap and is it so cheap to pollute that the fact that jets fly faster is the only important factor to the airlines?

Also as aeroplanes run at maximum power at take off can they get any help from ground installation that run at clean energy, electricity. 

keep up the good work,

Anders

What do you think?

Title: Why don't we use turboprop planes?
Post by: ccheric on 08/08/2010 14:47:40

I don't have the exact number, but turboprops are about 25% more fuel efficient than turbofans. (may correct me on the exact numbers)
For a quick comparison, a Bombardier Dash 8 Q-400 flies at ~414mph, a Boeing 737 flies at ~511mph.
Range also plays an important role on the actual fuel-per-passenger-mile number. Turboprops, being slow, are generally used for shorter routes, which means they carry less fuel. Turbofans, being faster and used for longer routes, has to not only carry the extra fuel for the range, but also the extra fuel to carry that extra fuel around (nonlinear increase).

And then there is the noise issue. I wouldn't vouch for any one, but turboprops' open rotors are much louder.

The airlines will also need to look at the competition, among other things like maintenance. If multiple airlines are competing on the same route, with different airplane types, will there be a preference for a sleeker looking type? The carbon trading laws for airlines in Europe may already be putting pressure on the selection of airplane types.


Airplanes usually don't use max power at takeoff. They only need max power when the weight is high, runway is short, or runway condition is bad. There are already many measures commonly in place to save fuel on the ground, e.g. use one engine for taxing, use ground power instead of APU, use electric motor for taxing. Currently there is no technology available to commercial airplanes to assist takeoffs. (I'm not aware of any plans for such) Something like a catapult launcher, will however increase the structural demand of the airplane, increasing weight and decreasing efficiency. Something like a runway rail-gun that shoots the plane out of the airport, may destroy avionics, the protection of which will increase weight... otherwise an awesome technology. (there is some research on using similar technology for non-human lunch into orbit)


Last but not least, electricity from coal/oil are not that clean anyways. Only nuke, solar, wind, etc, are C02 clean.


And a lot more....

Title: Why don't we use turboprop planes?
Post by: Geezer on 08/08/2010 18:50:59

Don't forget the propfan.

http://en.wikipedia.org/wiki/Propfan