[Closed] Aeroplane fuel economy

Dash 8 turboprops taxi on one engine.

A320 is somewhere between 750 and 1250 kg / hour. You could probably reach 70 with little more than idle power, or a decent wedge of thrust on a single engine.

1000 / .8 = 1250 litres = 275 gallons.

So 70 / 275 = .25 miles per gallon.

APU should be running if single engine but not strictly necessary. Since trundling down the M6 probably counts as not following SOPs I daresay you could get away with it.

Dash 8 turboprops taxi on one engine.

"EE-ee. EE-ee. Ee-ee-ee-ee-ee-ee. EE-EE..."

So 70 / 275 = .25 miles per gallon.

But there are what, 250 passengers on board, so that makes it around 60mpg per passenger. Not bad. IIRC that's comparable to a bus?

Boeing 777 with GE90 engines will accelerate to 40 Kts (46mph) on idle power alone....thats with an empty aircraft and 40 tons of fuel.

Best cornering speed is < 10 kts

A320 has in region of 170 Pax, not 250

My Luscombe burns 20 litres an hour , cruises at 88kts , but is only 2 seater.
Based a airstrip not to dissimilar to Chilbolton

sierrakilo - Member

Boeing 777 with GE90 engines will accelerate to 40 Kts (46mph) on idle power alone....

That's pretty badass. Well, OK, you can do the same with a mondeo but not while carrying 450 people.

Molgrips. A bus does around 6mpg in town, and 9.1-9.3mpg at motorway speeds, with 65 passengers on board. I cant do the maths, im too tired.

Large turbofan engines generate way too much thrust at idle. When taxiing the pilots main challenge on busy taxi ways when queueing, is managing brake temperatures as they're always dragging their brakes. I think a large turbofan engine, like a 777 engine, generates around 6 to 8k lbs of thrust each at idle. The majority of an engines thrust, around 90%, comes from the fan, the glorified propeller at the front of the engine. So you can't really slow that down too much - the larger the fan the slower the rpm (limited by tip speed which can't exceed the speed of sound at take off), so you have a very narrow operating speed range as the turbine driving it wants to spin quickly and you can't run it slowly enough when at idle, so the result is a lot of excess power at idle.

I concur with Flaperon's figures. Although SE taxi at 70 would be quite 'exciting' I think. I'd prefer both on, but the kgs/hour would be very similar for 70mph.

Now I know some German autobahns have been designed to be usable as impromptu runways for F15s

BAC once landed a Jaguar on the M55 back in the 1970's:

Shortly before the M55 was due for completion, arrangements were made in conjunction with the Ministry of Defence, and the British Aircraft Corporation, for a Jaguar G R Mark 1(XX109) aircraft, from the Warton (Lancashire) Aerodrome, to land on the afternoon of Saturday, 26 April, 1975, on the road base of a section of carriageway near Weeton. After fitting four of the RAF's latest cluster bombs on the plane, it then took off from the motorway. The purpose was to demonstrate the Jaguar's ability to land and take off in short distances.