Airbus okays use of ‘Taxibot’ to tow planes to the runway Airbus last week revealed it has certified a “Taxibot” to transport its single-aisle planes from stand to runway. As explained in an Airbus post, the SESAR project that aims to digitize air traffic control across Europe created a sub-project called HERON (Highly Efficient gReen OperatioNs) that aims to reduce the aviation …
yes, but who will be held accountable if its wings clip another plane on the way to the terminal. pilot should be pretty aware of the space needed to maneuver his plane, and have a good idea of exactly where the plane needs to be parked, not to mention a possibly better perspective of the area from the planes cabin than the guy with his chin on the ground.
"better perspective of the area from the planes cabin than the guy with his chin on the ground."
From the cabin? Not. From the cockpit? Certainly.
This seems like a wizard idea. Concorde burned an enormous amount of fuel getting from the stand to the runway. Stop and go traffic in a car is murder on MPG (KPL) and I suspect that it's even worse with jet engines.
Thermal cycles are stressful things for engines, especially going from idle to takeoff thrust. Presumably this means that the engines will still need to be started some minimum time before reaching the runway. If HERON becomes a common thing it'll be interesting to see if there are more rejected takeoffs or engine failures and emergency landings.
Tugs are slow, the need to dispose of the tug in a place where it can easily return to the apron without causing congestion on taxiways or the runway will perhaps limit this at some airports.
You are right, they will probably have to start the engines anyway some time before takeoff, but still they can probably save some fuel by doing it at the last moment and just for the right amount of time to make them work properly. Overall this can lead to fuel savings, especially if there is some kind of congestion and so the planes have to wait in line with engines running (as of today).
Not just at the last moment, but presumably only to idle speed, whereas taxying under own power would require some thrust above idle? The airliner world tends to be conservative and needs to make pretty accurate fuel calculations, so if they are claiming to save "half the fuel" then this must be what they are seeing in practice.
M.
>wait in line with engines running
In extreme circumstances I am led to believe (ok, YouTube leads me to believe) that planes that are kept waiting after a long taxi may have to return to the stand for re-fueling - there are very strict limits on the amount of "spare" fuel that the plane must carry at the point of departure.
When Concorde was still flying from Heathrow it would typically burn around two and a half tons of fuel between engine start and taxiing to the end of the runway. Concorde flights were always prioritised on the ground so that they usually got to the end of the runway then took off straight away - a delay of even five minutes could mean having to return to the gate for a fuel top up. Also, the pilots would always be using the brakes as the engines were that powerful that even at idle the aircraft still wanted to bob along at around 20mph.
It would also be nice to not have planes running jet engines close to where all the people are. Jetbridges have gaps that let the hot air / unburned jet fuel into the jetbridge and main airport, plus there are baggage handlers etc. who would likely appreciate being able to work without the noise and smell. Even if the jet has to start warming up its engines shortly after the tug pulls it away that's a big win for the comfort of people before considering the potential fuel savings.
Proper warm up for a CFM equipped A320 is 2 minutes if it has been shutdown for less the 2 hours, and 5 minutes if longer than 2 hours. Your start the clock when the second engine is started, usually the chrono timer, and its checked before you line up. Unless your gate is near your runway, not usually a problem. Feels like a solution in search of a problem.
Also looking at the very long taxi times at some airports is this going to increase the time from the current pushback to power tests before entering the runway?
I would be surprised if the vehicle supported the same taxiing speed as the aircraft under it's own power.
That is the answer right there. Schipol is a good example. Any airport where the runway is on the other side of the terminal (or further) from the departure gate will benefit. Taxi, taxi, taxi, and more taxi.
Conversely, an airline's hub airport where they have the prime gates right next to the departure runway...not much value.
Of course it supports the same taxi speeds.
Schiphol has been trialling Taxibot for several years, it easily does 22 knots. (25mph, 40kph)
Have a video. It's zooming along at around the 1 minute mark.
At airports with congestion, like Heathrow or Schiphol or JFK, taxibots make sense, especially if you have to trundle 3.5 kilometres from the one end of the airport to the other to take off (at LHR any BA plane from T5A/B/C to the eastern end for a 27L/R departure, or any plane from T2/3 to the western end for an 09L/R departure). JFK... well, it's an airport in the middle of Brooklyn, so yeah, trying to reduce noise and pollution again makes sense.
At Schiphol, the Polderbaan is 'miles' away from the terminal buildings, so having a taxibot take the plane at least most of the way there before starting up the engines and warming them up on the last bit of the trundle to the runway makes sense. Given Schiphol has already tried to start banning short-distance flights over the excessive emissions (although that all got blocked because the airlines complained), a taxibot can make a difference.
Of course, figuring out how to get the (eventually autonomous) taxibots to return to the terminal without crashing into planes or running off taxiways is another problem to solve.
"Of course, figuring out how to get the (eventually autonomous) taxibots to return to the terminal without crashing into planes or running off taxiways is another problem to solve."
If you look at the cost of one aircraft, a single accident would pay for a driver for a decade or more. Besides replacement/repairs, chances are that it would create a mess at the airport. A human driver isn't perfect, but a red "stop" light can be put in the taxibot that tells the driver to stop immediately and communicate with ground control if they've missed an instruction over the radio. If the practice gets to be more common, there might be taxibot roads separate from taxiways.
"the engines will still need to be started some minimum time before reaching the runway."
The engines will need to be started right after push-back to warm up and provide hotel power. The APU can be shut down as well. Everything needs to come up to temp/pressure so the pilot knows it's all good and the sooner the better. Besides saving fuel from not ramping power up and down, they would also not be riding the brakes all the way out.
For me it's been throwing times wherever you feel like in the sentence.
> Last week, Airbus revealed it has certified a “Taxibot” to transport its single-aisle planes from stand to runway.
> Airbus last week revealed it has certified a “Taxibot” to transport its single-aisle planes from stand to runway.
> Airbus revealed it has certified a “Taxibot” to transport its single-aisle planes from stand to runway last week.
> Airbus revealed, last week, it has certified a “Taxibot” to transport its single-aisle planes from stand to runway.
> Airbus revealed it has certified a “Taxibot” last week to transport its single-aisle planes from stand to runway.
> Airbus revealed it has certified a “Taxibot” to transport last week its single-aisle planes from stand to runway.
> Airbus revealed it last week has certified a “Taxibot” to transport its single-aisle planes from stand to runway.
> Airbus revealed it has last week certified a “Taxibot” to transport its single-aisle planes from stand to runway.
choose your favorite placement of time. Choose what you've been seeing most commonly lately. Choose the "Wtf? Why are people DOing it like that?!?" Honestly almost all of the lines above are better than what is used in the article.
I think that's just Brit journalistic style. It gets the "who" and "when" of the standard five "Ws" (who, what, when, where, and why) of journalism out of the way in just a few words.
If you regularly read the Beeb, the Grauniad, or basically any other outlet in the UK, you'll find locutions like that. It doesn't bother me, it's just "local color."
Personally, I'm just happy when the subject and predicate in a sentence agree in number and tense. Oh, and they get the facts right. That helps, too.
Back of the envelope calculation for somewhere like Heathrow where there are 250-ish short haul departures per day from BA alone (according to Google). Average taxi time is 25 minutes, so given a 5 minute warm-up and a bit of flexibility, the saving per flight will be 15 minutes. You can only count the saving of one engine (because they're already using one-engine taxi procedures), so that's 250 * 15 minutes * 500kg/hour of fuel, so approximately 31 tonnes of fuel per day, or 11,000 tonnes per year. That's 35,000 tonnes of CO2.
Throw other airlines into the mix (Air France, Lufthansa, Iberia all use A320s for short haul because the 737 is crap) and the benefits get even better. There are, however, some quite big challenges associated with the implementation, namely that if it doesn't release from the aircraft then you have something stuck in quite an inconvenient position and holding everything else up. Faults tend to present on Airbus at first engine start, so doing that in the queue for take-off is not ideal. None of these are insurmountable, though.
Don't forget that the 'taxi' uses fuel as well, so it's not completely eliminating emissions. It will be significantly lower though.
Add in the cost of another attendant driver and another machine that needs maintenance. I'm not sure how much sense it will make financially, but pleased to see that they're looking to improve what can be improved.
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The trouble with "runway to stand" towing is that there's no good point to hook up the tow, which takes some time. For efficiency and safety reasons, aircraft have to move off the runway as soon as possible. Most major airports have slanted taxiway exits that allow exiting the runway at increased speed even. Aircraft then have to basically keep moving as the aircraft landing behind them might well use the same exit and need the space. So there's not really a good point in that travel to stop, wait to attach the tug and then continue again without potentially being in the way. There might be ways around this in some airports but those will likely be the exception, not the norm.
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not sure they're thinking of doing a tow from the runway to the terminal if there's any chance the plane is going to continue to fly. once the engines are shut down there is a period where they need to stay shut down before restarting. believe i read somewhere that due to uneven cooling down in the engine the rotors can warp and starting up before things cool down enough can cause interference between the rotor and the stater. not desirable in a jet engine.
There should be no need for guesstimates, I remember a couple decades back, the use of tow tractors to move the aircraft to the “start of the runway” where it then fired up its engines a couple of minutes before take off. The purpose being two fold: reduce fuel consumption/waste and reduce airport emissions. So there should be allot of real world data on this.
About the only new feature is the ability of the pilot to control the tow tractors. However ,this is of very limited value, given the very limited ground view from the cockpit, so the pilot will need a video feed from the tow tractors etc. Personally, I don’t see the value, the tow tractor driver should be an expert on manoeuvring around the airport with a jet in tow; on less bit of pressure on the pilot just before take off.
An additional complication is the engine warm up time, given places like Heathrow have a take-off spacing of 45 seconds, the engines can’t be started at start of the runway, but at some distance before it, at designated engine starting places on the taxiways ie. Not at the terminal bay.
Upvoted for the reference to this not being *quite* as new an idea as it might first seem - I too remember the articles about the use of tugs for taxying.
However, on your second point - re the usefulness of this particular implementation - it's worth remembering that pilots are *already* capable of taxying their aircraft without external assistance, so provided the taxibot doesn't significantly alter the handling characteristics of the aircraft compared with it taxying under its own power and steered directly from the nose wheel, then the pilot should be no less capable of reaching their destination safely than they are today.
The main advantage I therefore see at present in having the pilot controlling the taxibot is that it fits neatly into the existing ATC procedures for directing taxying aircraft around the airport, rather than requiring ATC to know whether they need to be talking to the pilot or tug driver. There may also be additional training requirements for tug drivers to allow them to be towing aircraft around any part of the airport vs only those parts they presently operate in.
Whilst it's not referred to in the article or video, a potential future benefit might then also be in allowing autonomous upgrades so that the taxibot could return to the stand area without the need to be driven back by a human. You might still need a human to handle getting it into position at the start, and detatching at the end, of each taxying movement, but if you could avoid the need to have drivers twiddling their thumbs under the nose of every taxying aircraft using a taxibot, and only need to have them stationed around the stand area (as in present tug operations) and additionally near the takeoff area (to handle detaching), that'd be a somewhat more efficient use of trained personnel.
It's an ROV connected to the aircraft controls.
The pilot drives the plane the same way they already do. That's the cool bit.
I'm genuinely impressed, this has been done really well.
After disconnection, the onboard driver takes over and drives it back to to stand for the next flight.
I think you may be being a bit pessimistic in some areas. Getting the tug engaged with the plane should be easily (and better) done using routine robot controls - image and or proximity systems. We are currently hearing people talk seriously about driverless cars on the open road so a tug and plane in a pretty sterile environment would be a doddle by comparison.
I remember a couple decades back, the use of tow tractors to move the aircraft to ...
I'm sure I recall something on the telly, possibly on Tomorrow's World (so that dates it) where they were showing some new idea which was basically this without the pilot control. At the time, it was said that towing using a tow bar had significant limitations (notably speed), but this new fangled tug that picked up the nose wheel avoided that. For some reason, a figure of 15t of fuel saved with a big (would have been a 747 Jumbo back then) aircraft at somewhere like Heathrow.
And then, back when I was flying (i.e. before young free and single gave way to family house etc.), we had a mechanical tug that worked on much the same principle (but controlled by someone walking with it) for moving our little birds in and out of the hangar. That was a couple of decades ago now.
So as far as I can see, the only thing that's actually new is a) pilot control and b) certified for a. Everything else has been around for decades.
Perhaps the manufactures can beef up the nose gear and airframe... in preparation for catapult take off of passenger aircraft!
Alternatively, there's always JATO/RATO...
A 747 is in a "slightly" different weight class to an A220 or A320 series aircraft. It's probably one of the things that needed to be certified, but I would imagine it's comparatively far less of a problem on a single aisle narrowbody compared to the stresses put on the nose gear strut of a 4 engine wide-body.
Transport to and from hangars for maintenance would be done at low speed and unloaded, putting far less stress on the nosewheel. Plus that that is a limited amount of cycles. The problem isn't that the nosewheel can't stand up to towing, it's that it can't withstand the amount of force cycles involved in towing (at speed) as a standard operation for every single flight (or at least it isn't certified). Also keep in mind that this solution by Airbus isn't certified for the A340, A350 or A380, which would be a far more fair comparison to a Boeing 747 or 777 for instance. It might well be that Boeing narrow body aircraft like the 737 could withstand this towing as well, but the main thing is that currently, this simply isn't certified as Boeing simply hasn't done the research and paperwork required to prove that it is safe.
With a bit of logical thinking, you might discover that isn't necessarily a problem.
If the bot hooks up from the back, it can decouple and scuttle back between the legs of the main landing gear (it is low enough to fit under the fuselage of all aircraft with the possible exception of the B737).
I saw the headline and assumed that they'd come up with a unit that didn't need a driver; something like, a driver takes it to the gate and hooks it to the plane, then gets out. The pilot remote-steers it to the runway, where it disengages, and then returns autonomously to a parking space for the next go round.
This is - a driver drives the tug to the plane and hooks it up, the pilot steers it while the driver sits there, the driver unhooks it and drives it back to the apron. Which is exactly as it is now except for the pilot doing the steering. Still need one tug and one driver for every taxi out.
AFAIK the tug nowadays only pushes the plane back from the gate, and then the plane uses its own engines to move to the take off line. So the idea here is to tug the plane around while on the ground and not just push it back from the gate. Still I'd totally expect the tug to be an actual bot, so as you say it should come back on its own, at least. It was probably the original idea but it got scrapped because it's not safe enough.
One original proposal was that after pushing back under driver control, with wing walkers, it would be controlled by the aircraft
The issue was that it needed modifications to all planes to be worth the airports investing which they wouldn't do until the aircraft were compatible, which needed Airbus and Boeing to agree.
The other problem, which this system also has to solve, is that the nose gear needed strengthening to tow at taxi speeds, and be able to stop in an emergency without break the gear off.
The breaking braking problem has been solved by not braking.
Aircraft can already stop themselves while taxiing, so this thing only pulls, and leaves the stopping part to the aircraft.
Must by fairly complicated to make sure it's only stopping itself and not the aircraft it was pulling a moment earlier.
I suspect in future they'd want to make the tugs autonomous for the "not towing an aircraft" portions of this rigmarole. But aviation is never going to accept driverless vehicles hooking up to jets and whizzing around on the apron without exhaustive testing. Airbus probably wants to get the use of tugs for these purposes normalized first before they start trying to take the next steps towards making them autonomous.
The only thing I have to wonder about is how they're going to run AC systems when the engines remain off after pushback. Right now the standard is that the aircraft is on ground power and usually external cold air supply until push back, after which the passengers get a little uncomfortable until the first engine is started.
Do they now run the APU for bleed-air and power until they reach the point for engine start? That's going to put a lot more hours on the APU with related fuel and service costs. I have to wonder if that consideration is taken into account in the cost analysis by Airbus
My experience (and that of a few friends, some of which are airline pilots) is that unless it's a really hot day, they (especially the low-cost carriers) keep the APU off anyway and just let the passengers and crew suffer until engine start anyway. By that time you're usually glad when the engines start and cool air starts circulating.
The APU does not provide power to the cabin air conditioning. It provides power for the airplane's electronic and hydraulic systems and crucially, the power needed to start the main jet engines. That's why it's blisteringly hot inside the cabin on hot days until the main engines have been started.
The APU bleed air absolutely can be used for cabin AC on the A320. (and if you're looking for how something works, there's always a video with an indian guy explaining the topic. Such as this one explaining the Airbus A320 pneumatic and bleed air system)
If they can get this working with electric motors (or at least hybrid) then another plus is the definite potential to improve safety and air quality on the ramp - although I love the smell of burning jet fuel - engines often burn oil and other crap when starting up, and if you're working on the ramp every day it's probably going to take a toll on your health.
If each aircraft just has to start a relatively small APU with an exhaust that's high up, rather than starting two or more jet engines down at person-height, I'd expect that would make a difference. Don't start the engines until you're on the taxiway out in the open and the startup smoke dissipates where there's nobody to directly breathe it in.
Could also reduce the likelihood of foreign object damage, as well as reducing the likelihood of workers being ingested into running engines.
All low probability, but high cost/impact issues which probably add to the overall business case.
1) Aircraft gets towed taxi rather than doing so under power.
2) While queueing for runway, aircraft performs engine startup.
3) The APU trips and there's a total power loss.
4) Entire airport sits and twiddles its thumbs while a trolley-ack runs out to provide power to start the now-immobilised aircraft stalling the queue.
What? You mean you haven't been on one that's had 3 happen at the gate? You need to fly more often. This is usually accompanied by increasing murmurings of panic from the more nervous passengers sitting in the darkness while the staff whistle up a trolley-ack, despite this only taking the odd couple of minutes at the gate. It'll be fun to see what happens when they have to wait for one to traipse out to the runway queue.
A lot of tugs incorporate a ground power unit capable of starting aircraft these days. They are also capable of providing at least basic electrical power to aircraft when moving them so they don't need to run an apu onboard, most modern airliners can't even be towed if they don't have power.
This is how engineers do it:
> Sharp-eyed readers may have noticed that video is a few years old. That’s because Airbus has tested Taxibot for years.
> However, it was only last week that the European aerospace giant announced that it has certified the aircraft modifications Taxibot requires for use on its single-aisle aircraft.
Meanwhile, in driverless car news...
