No engine power needed until lined up........

[NacelleStrake]

Messrs Messier Bugatti Dowty, [Airbus undercarriage manufacturer's],have developed an electric motor to power the taxi of large jet transports to cut back on expensive fuel burn during this portion of the flight. When will we get V1 speed on this?

[ShyTorque]

Nice idea, but is it practical?

Jet engines, even at idle, burn fuel (and produce residual thrust, which is what keeps the aircraft rolling).

So, unless the engines are only started at the end of the taxying phase (and would this be allowed, possibly not) how much fuel will actually be saved by using this system?

It's also a bigger logistical problem if the aircraft goes tech on start when it's already in a queue on the taxiway, as opposed to on stand. There is probably nowhere to turn off except via the runway. Many tech issues are discovered during, or just after engine start.

Where will the power to drive the electric motors come from? Additional batteries, a bigger APU, or a generator (i.e engine driven...see above)?

[NacelleStrake]

APU, apparently.... Messier-Bugatti-Dowty (http://www.safranmbd.com/systems-equipment-178/electric-green-taxiing-system/)

[Groundloop]

Different company - same idea:-

WheelTug Ground Test, June 2012 - YouTube


WheelTug Ground Operations - YouTube

[DaveReidUK]

Different company - same ideaInteresting difference in approach - WheelTug drives the nose gear whereas EGTS powers the MLG.

[NacelleStrake]

As ShyTorque intimated. When would you light the cans to be able to monitor certain systems?

[JustOccurred2Me]

Even if the whole premise is a good idea, as a mere SLF I don't understand why you'd want to build in the additional equipment (= weight) to the a/c when a perfectly good tug would do the job instead.

In any case, I always understood there were sound technical and safety reasons (not to mention it being good airmanship) why you warm the engines up away from the runway before turning the volume up to 11 for t/o?

[Lightning Mate]

....why you warm the engines up away from the runway before turning the
volume up to 11 for t/o?

One does not warm up a gas turbine - it's not necessary.

[con-pilot]

One does not warm up a gas turbine - it's not necessary.

Not necessarily. There are airports with extremely low ambient temperatures that when a jet aircraft is parked outside overnight, one has to wait for the oil temperature to reach a minimum temperature after start, as not to exceed the maximum oil pressure allowable for takeoff.

I have also operated at airports that I had to pre-heat jet engines prior to start, as not to risk the starter shafts from breaking*, again only if the aircraft remained outside overnight due to the low ambient temperatures.



* I saw a Lear 24 shear the starter shafts on both engines one morning in Gunnison, Colorado. We tried to tell them, but....

[PAXboy]

Here we go again! This question gets raised about once a year. All the arguments for and against have been set ou tin the previous threads whihc careful searching should find.

In short:


The places where the most benefit to be had is at large airports, such as LHR andf JFK. At smaller, there is little delay.
Since every large airport is built around the current format of tug for push back and then taxi. How do you re-engineer them?

[Agaricus bisporus]

Why do you need to re-engineer anything? How does a self-powered pushback require a different layout?

I think anything that frees us from reliance on availability of tugs is a thoroughly good thing. It is far simpler and more reliable (and often quicker) to operate from taxi-off stands and this innovation effectively makes all stands taxi-off.

Ditch the pushback tugs, bring it on!

[Denti]

Why re-engineer them? Start up the APU, push back with just one wing walker instead of a push back driver and a wing walker and then taxi on electric power out to the runway, start up engines to meet the three minute warm up time (or two, depending on engine), shut down the APU and off you go.

Could get interesting if the APU dies before the engines are started and the aircraft in question is blocking a major taxiway.

[Intruder]

One does not warm up a gas turbine - it's not necessary.
One DOES run airliner engines for 4 minutes or so to ensure integrity of the fuel delivery system...

[PAXboy]

DentiCould get interesting if the APU dies before the engines are started and the aircraft in question is blocking a major taxiway. Exactly! How do you extract the stalled a/c and get it back? Does the recuse tug have to go down the runway (at it's usual speed) to get to the head of the queue?

Do you need to lay some more access roads to the queue line?

If this was a simple task - it would have been running more than a decade ago. As I understand it, attempts and Patents on this idea have been running for a lot longer.

The only change now is the price of fuel that might make it viable. But any airport that introduced it would be faced with charges (redundancy, surplus capital equipment etc.) and those costs get passed directly onto the carriers and our tickets.

BBC News - Paris Air Show: Aircraft tech that works best on the ground (http://www.bbc.co.uk/news/business-22992654)

[SloppyJoe]

One does not warm up a gas turbine - it's not necessary.


In Johannesburg we warm up our A340-300 engines for 10 minutes prior to taxi as helps with the EGT on take-off.

[Lord Spandex Masher]

How do you extract the stalled a/c and get it back?

The same way you would for any other problem which prevented it from taxying further. That already happens you see.

[Denti]

@Paxboy, to be honest it is not that big an issue, the same thing can happen right now already (technical problems). And yes, in that case a tug has to go out and get the plane off the taxiway.

Had to get towed of a runway once already, not a big deal, a couple more holdings for those arriving and a few minutes delay for those waiting to get off the ground.

[TURIN]

Look at the bigger picture. How many times have you been sat on the gate, ready to go but waiting for a tug. This system gets rid of up to 3 ground staff and a tug per pushback. That is a big saving in the long run.

[500 above]

Not really. You would still need wing walkers.

[TURIN]

Depends on the airport.


By the way, Lightning mate..



One does not warm up a gas turbine - it's not necessary.

Every engine run AMM ref I have come across says to let the engine stabalise at idle for 5 mins before increasing power.

However, I take the point that a certain extremely quick twin engine interceptor may not have had this luxury when called upon to say hello to the neighbours from across the North Sea. :ok:

[avionic type]

I can't remember which airport in Texas Houston, Dallas, or Austin but I saw "Nose in" DC9s start their engines select right hand reverse thrust and back out to the centre line of the taxi way and then head for the take off with no problem .Wouldn't be possible with low wing mounted jet engines plus the cost of fuel now, it was in the 90s.

[India Charlie]

Guys, how about an "Electric Green Flying System"? No need for gas turbines and ATF!!! How lovely the world would be without the amazing sound of those turbines and you wont even know an aircraft flew over you. Ah! The romance of aviation... :sad:

Though I agree that fuel is getting costlier and there's also the environmental question, this system which could prove to be a great one hardly matters unless we stop using fossil fuels altogether for any use. :\

What about emissions from jet engines at 35,000 ft? Will an EGFS address that? Unless we switch to solar powered aircraft that look like UFOs :yuk:

And most of us aviation buffs so love the pushback truck. It would be sad to see it go. The process of pushback (with the truck) adds to the excitement and romance of being at an airport and in an aircraft. :ok:

If we're giving up all of this, we might as well be arriving at an airport in maglev, building-climbing cars like in "Minority Report". :8

[Mr Angry from Purley]

Just think of all the extra hours you could extract from pilots, the taxi tim wouldn't count towards the block time.............:\

[thing]

One DOES run airliner engines for 4 minutes or so to ensure integrity of the fuel delivery system...

I think Lightning Mate would be plugging into a tanker by then...

I was at Binbrook at The End Of Lightnings and somebody chucked a Mk6 up without a ventral, ran it at full chat in the cct in tight turns and I think got to 'land now or go very quiet' in around 4 minutes.