Is this a good way to save fuel?

chornedsnorkack · Post by **chornedsnorkack** » 21 Aug 2006, 12:14

David747 wrote:Correct me if I'm wrong, but the fuel that is burned by a plane during taxi to the runway is excess fuel, without burning this fuel the aircraft will be too heavy for take off.

A jet engine accelerating a small amount of air to a high speed is the only engine suitable to propel a plane at nearsonic speed kilometres away from Earth. But it is highly inefficient way of moving anything slowly. For slow gear on ground, one would expect tugs on driving wheels to be much more efficient. Taxiing is a waste of fuel...

Stepha380 · Post by **Stepha380** » 21 Aug 2006, 12:30

David747 wrote:another thing, if planes are taxied to the runway by some system, how will it save companies fuel expenses? they will still need the fuel to get the plane airborne, and as we can see, jet fuel is expensive all around, a few pounds of jet fuel being saved during an automatic taxi will not make much of a difference.

You don't pay the fuel burnt for taxi. Jet engines are not really efficient on the ground.
You don't run the engines when you are waiting for take-off for dozens of minutes just the APU for air cond.

Bracebrace · Post by **Bracebrace** » 21 Aug 2006, 14:37

Standard taxi fuel for a 737 on OFP's: 250kg-300kg? Suppose you are a small charter company, 5 737's in your fleet, 3 destinations a day (so 6 taxi procedures to do). 250 x 5 x 3 x 2 = 7500kg of fuel on ONE day. With 7500kg of fuel you can get a long way with a 737...

Try the same calculation for a fleet of 30 737's, or 10 747's with a much higher standard taxi fuel amount...

Advisor · Post by **Advisor** » 22 Aug 2006, 20:56

Bracebrace wrote:Standard taxi fuel for a 737 on OFP's: 250kg-300kg? Suppose you are a small charter company, 5 737's in your fleet, 3 destinations a day (so 6 taxi procedures to do). 250 x 5 x 3 x 2 = 7500kg of fuel on ONE day. With 7500kg of fuel you can get a long way with a 737...

Try the same calculation for a fleet of 30 737's, or 10 747's with a much higher standard taxi fuel amount...

Can you support this by statistics or even some more reasons...

Bracebrace · Post by **Bracebrace** » 22 Aug 2006, 22:40

Airbus: http://www.wingfiles.com/files/systems/fueleconomy.pdf

(page 18 for taxi fuel burn data)

Boeing: http://www.wingfiles.com/files/systems/ ... snov04.pdf

(page 75 for taxi fuel burn data)

EBAW_flyer · Post by **EBAW_flyer** » 23 Aug 2006, 09:29

But there's another problem; normaly you should taxi to the RWY under your own power for the simple reason that you have to check if your engines can be started. In Brussels I've seen 3 different cases where one of the engines did not start (or a malfunction during start-up). If you taxi on one engine or on no engine power at all and you get the problem near the RWY, you have to taxi back and in that case you easily loose about 30 mins. And engines are not designed to just start up and go to max thrust immediately. Just leave it the way it is today!

Stepha380 · Post by **Stepha380** » 23 Aug 2006, 09:43

n5528p wrote:
SN30952 wrote:Why not build sloping taxi ways?
Why not build sloping run ways?
Are you kidding?

Bernhard

I don't think he is, he has just forgotten the elevators.

fokker_f27 · Post by **fokker_f27** » 23 Aug 2006, 10:09

I would still vote for leaviing it as it is. Maybe if one really wants to, they could taxi on one engine, but sometimes, the most simple solution is the best.