[Closed] Aeroplane fuel economy

Is this a ploy to stop anyone overtaking you?

is it on a conveyor belt ?

Piper Cub or A380?

Why the M4 in particular?

Loads of variables but the answer is ...not very.

Aircraft are designed to fly not taxi down the M4.

[quote=Eyepic ]Loads of variables but the answer is ...not very.
Aircraft are designed to fly not taxi down the M1.
But what about the M4? Are you trying to avoid answering the question?

Ask Easyjet because last time I flew to schipol with them I think we landed in Rotterdam and drove the rest of the way.

Sorry edited M4 would of course be totally different to the M1 due to direcion of prevailing winds. ... which way down the M4 are you after?

I'd be interested to see the comparison between mpg on the m4 and the m62 as its more hilly terrain

Here's some reading for you

WEB.MIT.EDU "http://web.mit.edu/~hamsa/www/pubs/KhadilkarBalakrishnanGNC2011.pdf"

Ask Easyjet because last time I flew to schipol with them I think we landed in Rotterdam and drove the rest of the way.

Did you know Schipol is Dutch for "drive further than you have flown"

I do now.

Sorry to be sensible

[url= http://science.howstuffworks.com/transport/flight/modern/question192.htm ]747 fuel economy[/url]

Apparently Lancasters used to do 1mpg - a flight engineer who managed to get 1.1 mpg out of his aircraft was taken off ops and sent on a lecture tour. You can see why when you think that 10% extra range was then available - could have made the difference between getting home and not...

Piper Cub or A380?

Good question, but I was on a 737-700 at the time so let's go with that.

Flying Heathrow to Cardiff?

I was on a 737-700 at the time so let's go with that.

On the M4?

No. You weren't.

Ask Easyjet because last time I flew to schipol with them I think we landed in Rotterdam and drove the rest of the way.

Very similar at Frankfurt Hahn. Land. Taxi for 30 minutes. Depart aircraft. Get on bus. Drive for 30 minutes to terminal.

It's this sort of thing that makes LCY brilliant.
Land, brake very hard, turn off runway, park. Job done and away you go

Very similar at Frankfurt Hahn. Land. Taxi for 30 minutes. Depart aircraft. Get on bus. Drive for 30 minutes to terminal.

And you're STILL nowhere near Frankfurt! 😉

It's this sort of thing that makes LCY brilliant.
Land, brake very hard, turn off runway, park. Job done and away you go

See also Changi, which is abnormally efficient, pretty much any island runway (Barbados is a joy!) and, funnily enough, Frankfurt which is a superb airport!

And you're STILL nowhere near Frankfurt!

yeah, then you get in a clapped out old Mercedes taxi with a driver who think's he's an F1 driver!

Mind you, the airport seems to have the most mahoosive sex shop in it 😯

Ah, frankfurt hahn...

Decided to go to the stuttgart beer festival (excellent - do try it) for my 40th, wife said she would organise.

Direct flights way too expensive, flights to Hahn only 50 quid return, train from frankfurt to stuttgart cheap and fast.

Missus didn't check how to get from Hahn to either frankfurt or stuttgart. Ended up hiring a car and driving.

Anyway, some googling would indicate 10kg/m fuel burnt taxing a 737-700

Average taxi speeds would appear to be 15 knots (although I can't remember the last time I was on an aircraft taxiing that slowly, however if we use those numbers it's going to be a very unscientifically calculated (guessed) 40kg/m

Someone else can work out MPG!

Used to test aircraft engines, at full takeoff power, a GE CF6-80C2 (widely used on various aircraft, including 747's) will use just over a gallon per second. Bugger all to do with the question, but just thought I'd chuck it in!.

Used to test aircraft engines,

On a treadmill? Go on, you did, didn't you?

Sadly not. Would have been much more fun.

piedi di formaggio - Member

Land, brake very hard, turn off runway, park. Job done and away you go

I love City. It's the little lifeboats bobbing about at the end of the runway that make it perfect. That was my first domestic flight- so discovering that if you fly from Edinburgh to Stanstead, you're almost as far away as you started was an eyeopener.

Huh? What?

Did someone call?

Edit - my dad can fly from Chilbolton, Hants to Weston Zoyland, Somerset and back on a tank which appears to be made of an old beer barrel.

I think thats 11 gallons, and about 120 miles, so around 11mpg in one of these:
[img] [/img]

I'd hazard a guess at not very given they are currently developing electric nose wheel motors for taxiing

[url= http://aviationweek.com/awin/honeywellsafran-joint-venture-tests-electric-taxiing ]http://aviationweek.com/awin/honeywellsafran-joint-venture-tests-electric-taxiing[/url]

Don't think you'd get very far, with a tail height of 41ft & a wingspan of 112ft, wouldn't bridges be a problem?

Once spent a couple of hours in a 747 taxi-ing to take off at JFK; when we'd got near the front the pilot announced "that we'd burnt 10 tons of fuel so far", in a rather pi55ed off voice.

I was already tucked-up in an upstairs window sleep-bed outside the gaze of the stewardess - the G&T's had already had their effect 🙂

Is there a strip at Chilbolton? There was RAF Chilbolton, but no longer active, shirley? Or is he going from Popham? My local riding area, so always interested!

BR, once had four hours on the tarmac at LHR en route to LAS once. Also upstairs, thankfully, but we taxied out and back, and refuelled! Luckily they didn't run out of the chablis!

No idea but I do know that when I'm running a tornado I can get through 70kg per minute at times. Raises a little smirk from the 12 year old me when I'm at the throttles

The APU's will be sucking a fair amount of fuel too. Larger aircraft will have two, sometimes three APUs. Not exactly the most efficient part of the journey. The large engines generate too much thrust on the ground. Also fuel is invested in compressing air that is ultimately dumped overboard as there is just too much air on the ground for the engine to handle. These things are designed and optimised to be chugging along at 30k+ feet. Forget miles per gallon, you're in the realms of feet or inches per gallon.

My day job is a aircraft Engineer.
I get to taxy and run a variety of aircraft, over the years there has been BAC1-11, B737 -200,-300,-400,-500. B747-200,-400 ,B757, B767, B777 , DC-10, Tristar, and Airbus A320 family.
I think the most fuel used was once on a B747-200 where we had to do trim runs ( making correct power for the temp and pressure of the day ) and also Fan trim balance ( Just like dynamic wheel balancing , but in those days more trial and error method called a 3-shot plot )..... we went through nearly 20 tons of fuel that day !

Never known an aircraft with more than one APU, though. The B777 APU burns 250-300 kgs an hour if supplying air and electrics

I thought I'd chuck this in, copied from the Aviation Forum, in answer to a question about the fuel consumption of the Avro Vulcan:

Hi,

The Olympus 20201 fitted to the Vulcan has a fuel burn of 13,950 lbs/hr at maximum power (100-100.5%) at sea level on an ISA standard 15c, 1013.2mb day.

This equates to a rate of 55,800 lbs/hr for a Vulcan with Take Off power selected at the end of the runway. Quite a lot eh!

Quickly crunching a few numbers regarding the fuel burn and using Moggy's figure of 60p per litre, this equates to £5.24 per second.

To put this into perspective though, in similar circumstances; Max power, lined up on runway etc..... a Tornado GR4 in max reheat is burning 6 gallons of Avtur per second.

I'd hazard a guess at not very given they are currently developing electric nose wheel motors for taxiing

http://aviationweek.com/awin/honeywellsafran-joint-venture-tests-electric-taxiing

It's a nice concept which has been around for a while but the operators will never go for it. Too much unknowns of time between leaving the gate and cleared for take-off (i'm sorry tower, i just need to start my engines as i've been taxing on electric). They also won't want to risk starting their engines away from the terminal then finding out they have a problem so have to return.

[I know nothing]

Does it take much more fuel for a plane to taxi than it does to idle? ie, could it be worth taxiing with a powered wheel, even if the engines are still running?

[i]could it be worth taxiing with a powered wheel, even if the engines are still running? [/i]

possibly although you then have to transport the weight of all the generators and other gubbins for the whole time it's in the air.

They'd be better off having conveyor belts running from the boarding gates to the runways...

Ask Easyjet because last time I flew to schipol with them I think we landed in Rotterdam and drove the rest of the way.
Very similar at Frankfurt Hahn. Land. Taxi for 30 minutes. Depart aircraft. Get on bus. Drive for 30 minutes to terminal.

see also Paris CDG

Schiphol is crazy. Thought it was novel when you crossed 1 motorway, but now for one of the runways you cross 2 of them!

Have had bus to plane from one end of terminals at Frankfurt all the way up to the very last parking slot at the other end. And then taxied the entire length of the airport back the other way to take off. Thought we were going to drive to BHX.

Now I know some German autobahns have been designed to be usable as impromptu runways for F15s (have seen photos), but I don't think the M4 has been designed for 737's and A320's.

LHS is right on the electric nosewheel concept. Also its alot of dead weight - and therefore extra fuel, to carry around for the vast majority of its time - when the aircraft is flying. Also it is only of use when taxiing back after landing, as you neeed time for the enigne's to warm up before taking off, so you can't taxi out to the runway, fire up the engines and go. Airlines are looking and experimenting with shutting down one engine after landing and taxiing on one enigne, which saves a good chunk of the fuel which sort of destroys the case for the nosewheel motor thing.

Is there a strip at Chilbolton? There was RAF Chilbolton, but no longer active, shirley? Or is he going from Popham? My local riding area, so always interested!

There's a small private strip in the field at the back of what I guess was RAF Chilbolton (there's a small industrial park of what look like large 2nd world war bomb shelters). No public access though and certainly wouldn't get your transatlantic flights in there! I think there's about half a dozen light aircraft / microlights in the club, and the control tower / terminal / clubhouse is an old damp and rather green caravan.

Its a lot cheaper than Popham!

[i]Airlines are looking and experimenting with shutting down one engine after landing and taxiing on one enigne, which saves a good chunk of the fuel which sort of destroys the case for the nosewheel motor thing. [/i]

This use to be pretty normal on the 2-engine prop flights I use to go on.

you neeed time for the enigne's to warm up before taking off, so you can't taxi out to the runway, fire up the engines and go.

<where's flaperon?>

edit: [url= http://www.askthepilot.com/questionanswers/the-barking-dog-airbus-noises/ ]my brain is full of mindless drivel, some of which is correct.[/url]

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.