Spot on Rainboe. Slowly does it. There is very sophisticated software running the system to avoid various problems. WT will not turn an aircraft into a dragster!

I think Short Circuit blew a fuse...

Logical thinking Christiaan. Except WT have done quite a bit since the Proof of Concept. Your right about numerous scenarios, usable system, valid business case. We do have many more 'ideas'. Some equally as advanced as WT, which is a specific end use for one of many in house technologies. The Chorus Motor has much potential.

Tow bars are a constant source of maintenance woes. Hard linking a strut to a tug exposes the strut, mounting and airframe to the full jarring force of the tug. WT is much more gentle.

WT eliminates Jet blast and many FOD issues. Jet engines run on the ground act as giant vacuum cleaners for grit etc. NOT desirable. Some urban airports are now brining in limits as to the total ground noise envelope. Others have noise limits with early & late landings; a 10 minute taxi in creating 5 minutes of unnecessary noise (after cool down). Then there is air pollution emanating from airports. Using tugs is expensive too. However traditionally airports don't make a separate charge for their use - yet. Gate & taxiway operations will speed up considerably. WT will be a godsend.

When it comes to dips indentations and ramps etc, these have been factored in. Power usage can be momentarily increased to cope.

NSEU, WT's intent is to eliminate the day to day need for tugs. I shan't be addressing the commercially sensitive issue of pushback method here. Are you aware of the number of accidents directly caused by the use of tugs. Not risks, actual events. It was a proof of concept. The video is Boeing's.
Quite rightly WT were not allowed to interfere with ANY on-board systems. Hence the need for a separate power supply. V0.1 was never intended to be remotely close to V1.0. Boeing / Air Canada were satisfied with the method used to prove the concept. As were/are Delta and numerous others. To visually satisfy lay viewers of the video, the Proof of Concept test would have cost many millions more. Money WT just doesn't have to splash about.
When it comes to the real thing, none of your concerns will be issues. If they were, the project would have ceased by now.
The concept isn't new. There were experiments with hook on diesel motors in the 50's. I guess they floundered because the cost of fuel, noise, and environmental concerns weren't topics in those days.

Have any of you pilots experienced Virgin's towing a/c round airports? It seems to have ceased....

So you are saying that this system WILL be used for pushbacks?

If so, I think this biggest company's hurdle will be Occupational Health and Safety.... then company beancounters after a few million dollar-wingtips have sliced through lightpoles, other aircraft, etc...

Sorry NSEU after I posted I saw your last. Please see my previous edited post.
WT do know nobody would take up the system. That is IF your concerns were to crystallise.

H&S. First there is the FAA & CAA with certification and an STC. This is where Newport Aeronautical come in. They do such work for the big boys. They know what is feasible.
Airlines are quite protective of their fleets too.

Winglets managed it and that was a flight system!
WT are not amateurs.

NSEU- you're an avionics engineer? You are arguing a bit out of your sphere of knowledge!
If such a device failed on push, the first thing you would want it to do is gently provide automatic braking. What you must not do is brake the main wheels- that could tip the aeroplane back. We rely on such safety braking systems every time we get in an elevator!

Why would it not be used for pushbacks (if it can hack it)? We used to do powerbacks- starting engines on stand, idle reverse and let it go- steering to ground controllers visual instructions. It works OK, but training required, and the engines tend to ingest debris. The pilot has to follow exact visual instructions from the marshaller. I sat at Dallas and watched AA MD82s doing powerback after powerback most skillfully.

If this company wants to prove itself- good luck to them, let them try. They may just do it. But all the ideas are established procedure at some time or other. It's a complete red herring harping on about failed starts at holding points- everyday aeroplanes have trouble at various places. Just today I took off behind a 757 that abandoned take-off at Stockholm. It happens...people deal with it.

Rainboe,
I agree.
Let them try.
I can't see a 200 lbs add-on to the nosewheels provide enough traction in all but the most ideal cases.
I can't see saving a few hundred pounds of taxy fuel as compensating for carrying the equivalent of another passenger or two across the Atlantic.
I'd like to see the sums.
But if we're talking 0.1% or so, the changes in procedures, the necessity to still have push-back trucks on standby, and all that, may well negate any advantages.

See you in 2010.

Bear in mind that most electric motors can be used to provide a braking action as well as traction,
Either as a resistive brake i.e. motor used as a generator and power disapated in resistors, though not practical on an a/c through weight,
Or regenerative braking where the generated power is returned to the supply bus, this could work from touch down so it would not remove the braking action from the nose wheels.
As a last ditch an electric motor can go from forward to reverse, again to provide braking action.

Sorry westlakes....That makes sense on trams and trains, especially high-speed trains.
It makes no sense whatsoever on aircraft taxying at a few miles an hour.....

Great debate. It hasn't taken long for this think tank to arrive at many of the salient points.

The financial and environmental numbers can be calculated. Simply, on a 737-700 the savings will be something under $½M per year.....

Safety issues are here.


Oh & sooner than 2010. Plus there will be a constant stream of news along the way.

Prime objectives, Get it working, certified & installed. Deluxe features can wait.

Next time you pilots find yourself twiddling your thumbs during a tug related issue, you'll be thinking, 'roll on WT'.

True, I am an avionics maintenance engineer, but I'm actively involved in pushbacks of aircraft of many different types. Sure, I understand about braking during pushback... but my biggest concern is the motor locking up on takeoff/landing....I assume the system is NOT fitted with antiskid? Most airplane systems, if they lose electrical power, go into the safest mode. What happens if this nosewheel drive system loses power? Sure, you can put interlocks on this system, but how many will there be? (with reversers and spoilers, they seem to keep re-evaluating the number every 10 years after the existing interlocks have failed and caused major accidents).

BTW, if communications break down between the ground and flight deck during a critical part of pushback, what is the procedure to stop the aircraft? (at least with a tug, you can signal the tugdriver to stop... or even if you are in difficulty and are unable to signal the driver, he can see what you are doing at all times). Pushing back a 747, how long would the headset lead have to be before the pilots can see me? (Note: the longer the lead, the more likely it is put strain on the wiring, leading to failure... or to get caught under the wheels)... And just ask me how many times I have called the cockpit only to be told to "standby".... :mad:

Sorry All
I believe I introduced to words ”during push back” in attempt to
highlight one disadvantege of the system. :uhoh:
I guess the system is not designed for that phase of departure,
it is to allow “Taxi” with no engines or possibly 1 of 4 running to and from
the runway to save gas. But, hey, it has produced some good dialogue.;)

Some great dialogue & insight as to the numerous hurdles. Nobody is pretending it is going to be a walk in the park. If it were, I wouldn't be here because the system would already exist! Conversely if there were elementary show stoppers, by now the project would have ceased.

Many of the basic questions can be answered by spending 10 minutes on the web site.

From the preamble
System Overview

Introduction

WheelTug® is a fully integrated ground propulsion system for aircraft. Built into the hubs of the nose wheels, it will give aircraft of all sizes full ground mobility (forward & reverse with steering) without turbines or external tugs. It will not require airframe modifications. It will be powered by the Auxiliary Power Unit (APU) which, while technically a turbine, is designed for this sort of application.

To the:-
Join the team, Involvement can be full or part-time, and does not require relocation or frequent travel.

Christiaan

Yes I know, the only time it could possibly be used would be during touch down (or rejected take off) as part of the overall braking effort.
I was more trying to show that the presence of an electric motor (and no independant brakes on nose wheels) does not mean there is no possibility of "braking" those wheels, again as part of the overall braking action of the aircraft.

Consider how many electrical Joules would be required to heat the multiple brakes red hot in say 30 seconds. (This is what happens with traditional friction braking on landing). Then there is the increased size/weight of the (motor /) generator required to utilise said energy, mounted on the relatively flimsy front strut.... This energy has to be either very rapidly stored (weighty & bulky) or dumped as heat (might as well dump it without going through the transformation to electricity!). Back up brake systems would still be needed too!

Another issue. The concentration and redistribution of all those braking forces, instead of from the main bogeys, from the front strut, up into the airframe. Would 1st class & flight deck crew object to being used as friction material?

(You might have guessed from my terminology, although I have rudimentary understanding of the issues, it doesn't go much further.)

Well speaking as an LAE I think it sounds like a good idea. We have a lot of ATC slot delays here (flights to LHR) and the thought of being able to release the ground crew at depature time so they can go and do another job, instead of hanging around waiting for the slot sounds like a good idea. We have straight push backs so I see no problem with the crew doing it themselves. But our problem is ice in the winter. The parking stands are also the last places to be swept in the snow, mainly because there are aircraft parked there! We use TBL tractors for pushback, which have a very low mass, and quite often in winter they cannot get enough friction to get the pushback started. Often I am shovelling grit under their wheels so they can get a grip. Some gates have underfloor heating and these are much better, we need it on the other gates.
I see no problem with unsupervised engine starts. Nearly all pushbacks are performed by loaders, not LAEs, and I can't remember the last time we had an incident which would have been handled better with an LAE on the headset.
I think that airlines that operate to crowded airports where you have to wait in line for departure will find this a must have.
I am definitely for it, hope we can afford the leasing costs!

Braking

In theory only!

The use of regenerative braking on the rail system depends on being able to return the power to the supply network. In an a/c, despite the large electrical loads, I agree it could be a non-starter.

Any braking action would be in concert with the main bogeys and forces would be no larger than already imparted on the structure than conventional brakes.
As an example (this would not work in the a/c case) most high speed trains whan braking, first use the regenerative brakes and gradually blend in the conventional brakes as speed reduces - it's about how clever the automation is!

Most electrical motors can operate as a generator with no weight penalty, again it's all in the control equipment
(some windfarms are motors, when required to generate they run up to nearly synchronous speed as a motor the wind then accelerates them to synchronous speed which turns them into a generator)

Not very detailed but I hope this gives an idea of the principle.

The heat dump idea would be the resistive braking mentioned by me earlier - a non-started (or stopper!!!)

The design sketch in the early part of the thread is reminisent of the basic design of a linear motor (I could be way off beam here) that has been rolled up

http://en.wikipedia.org/wiki/Linear_motor

The Maglev trains use electrical braking as their sole means of stopping by control of the motor.

Again only theory from an electrical view point



Of course, to comply with best practice, will a/c fitted with this system also be fitted with reversing lights & an audible warning "CAUTION THIS AIRCRAFT IS REVERSING"
That's a joke by the way;)

NSEU:
It's all done on hand signals only! It's too dangerous to connect up for it. You have just run through why we used hand signals only for it. Can't you leave the practicalities about pushing to those that know about it, and stick to the technical side?

About 25 metres.

Humour first
Communications - cordless phones are pretty cheap
Regenerative - Hook it up like a trolley bus
-----------

The Chorus Motor is one very clever piece of kit. Virtual windings (bit like the Company) that actually harness the normally detrimental harmonics. On the fly it can perform as if many different style of motor, in one, and with greater efficiency than each regular motor/generator. Phenomenal power density. One of the big problems with traditional A/C motors is the size / capacity of the controller to handle the relatively large transient peak power requirements at start up. Industry leading Semikron are handling that side of things. Neat is a word that springs to mind.

Safely too. A DC motor has a failure mode akin to an arc welder. (Thought they banned smoking on flights some while ago). An AC motor fails to a non resistive open circuit state. An AC Chorus® Motor is the nextgen.
If I'm not mistaken, what held Maglev back for a long while, was the complexity of the electronics managing the magnetic field. All electric motors manage magnetic fields. Thus there will always be similarities. Mathematically a linear motor is simply an infinite rotating motor.

Come what may, WT technology has to safely, practically, economically reconcile itself with operations at airports.


I must thank you all for your continuing valued input.

Re reversing lights and "beep, beep, beep".
May well become mandatory.... normally you're alerted, by running engines and a big noisy tug, that something is due to happen. Now you'll have aircraft suddenly and quietly creep up on you !
Maybe we'll see the return of the "man with the red flag" !

rahosi,
On a more serious note, went back to the website and the ppt presentation.
If it works on a 767 it should work on a 737.
And I see WT has Semikron on board... not exactly a fly-by-night company (no pun intended).

Drove a new Toyota Prius the other day. Similar problem with the silence in reverse. For a laugh, whilst it was parking itself, I leant out the window and deliberately talked to someone gesticulating with both hands. It rather unnerved him seeing the steering wheel spinning this way & that.

Technology has a way of solving problems.

The 767 was supplied by Air Canada. The 737 will be WTs 1st target.

Re Semikron. Not sure if your comment was an accolade or not. They are worthy.

Fly by night or wire? :ouch:

Don't worry, it was meant as an accolade.... :ok: They were around when I started my "career", and that was a long long time ago.

Ignoring the obvious insult....
Maybe I should just leave the job to baggage handlers... or become a baggage handler and buy shares in this company? :ugh:

If there is no comms, how does the marshaller know
1) when to push
2) which way to point the aircraft (where there is a choice). Or does he look for a windsock?
3) which aircraft has priority if there is an aircraft pushing at the same time (behind him at parallel terminal fingers)? Sometimes manoeuvering aircraft at our terminal is akin to solving a chinese puzzle.

This forum is for disseminating information.. If I don't ask questions or make comments, how am I to learn how things work in your part of the world?
Also, just because this system works at your airport/in your country, it doesn't mean it will work at ours.

18 Wheeler.. thanks... but it was a mostly rhetorical question about lead length... I'll be sure to build up my neck muscles to take the weight of the cord (until I learn how to do the required hand signals).

Swedish Steve... I don't like hanging around the nosewheel either, but our company is trying to improve its ontime performance by keeping engineers from various trades on standby in the vicinity of the airplane. If we are there, we may as well do the pushback. Also, excuse my feeble attempt to save my job.

I've removed two posts which discussed the commercial good/bad/whatever of the company concerned. Not appropriate to PPRuNe, I suggest. While this thread continues down the "does it"/"doesn't it" and similar technical paths, we'll let it run ...

I watched a single marshaller reverse a 737 out of a gate at YMSY and then drive it forward to the edge of the apron using a long headset lead for communications to the aircraft with the single tug under the port main wheels operated by remote control by this single marshaller. Both engines were started whilst being maneuvered on the tug.

This leaves the issue of traction. Out of interest how much weight is supported by the nose gear of jet (say a 737 or A320 or a heavy such as a 747) under static conditions on the ground? It is this weight that will determine the amount of traction available.

W

rainboe :
If a large aircraft tug with a big diesel e.ngine can struggle sometimes, how can a small electric motor cope? I would have thought it would require a larger APU to be certified.


I know the 787 will have 2 250kva genny's on the apu, that would help.
i think your right on the traction front though.
tk

Lots of WheelTug info
 

Electric WheelTug System to Move Planes on the Ground, article in Design News

WheelTug Pushback
 

I just read through this old thread and I don't see what the problem with WheelTug pushback is.

Pilots are also not in control of aircraft movement when there is a tug for pushback. Pilot just signals to ground crew when to pushback and in what direction. Touching brakes when moving backwards is a big no-no, tug or no tug. As long as main wheel brakes are not used then no problem. Nose wheel braking cannot tip over the aircraft. Even if tug motor locks up the plane can not tilt over because nose wheel gets lighter and simply skids to a gentle stop. More so I believe procedures should not be changed from now. Target should be to just remove the tug when conditions allow. Ground crew should normally control the wheel tug via manual controls connected to a short cable and see both wing walkers for best reaction time. Pilot should only have an override control for both soft and hard stop. This tug motor is also great for airports with limited number of gates and airlines will need less ground crew too. Flights can leave the gate at scheduled time because taxi time is not a problem. It is only a problem for airlines that pay the pilots for actual taxi time...

Edited for clarity. Original was a bit messy. See below. :uhoh:

I am confused :confused:

Story published yesterday in the Times:

http://www.timesonline.co.uk/tol/new...cle3516551.ece

Presumably the same problem would apply if the a/c is 'towed' by motors in the nose wheels as proposed by Wheeltug....

I'm slightly bemused by that. Surely every time an aircraft is pushed/pulled off gate by a tug that is exactly what happens? I concede that the greater distance could mean greater stress cycles, but surely the nosewheel leg is designed to withstand such stress cycles within elastic limits?

I still think it's about the same as the marvelous idea of having blimps hovering at the ramps, lifting the aircraft.

No more taxying
No more runway friction.
No more runways, come to that.

No more runway length limitations, the aircraft can continue to accelerate until it reaches flying speed, and only then disconnect from the blimp, which returns to pick up the next aircraft.

Oh, you never heard of the idea? No wonder, I just thought of it....... honestly.

CJ

WheelTug Update
 

How is WheelTug doing with their development program? The story, link below, is around six month’s old, and it states: “Delta Airlines will get the first WheelTug-equipped 737s by late 2009, and at least one automaker is talking with Chorus as we go to press.”

http://www.motortrend.com/features/editorial/112_0901_flying_hybrids_technologue/index.html

I am curious if this installation is a new 737 delivery involving Boeing installing the WheelTug, or a retrofit to an existing Delta 737. It reads like certification will be done by then too. If so, has there been an installation done yet using production parts? Rahosi, are you still monitoring this forum? If so, can you bring us upd to date?

WheelTug has made some progress.
 

Well here I go, apparently talking to myself, on this one. After doing a little poking around, it appears that WheelTug is making progress. They have been granted this patent # US7,469,858 B2, dtd Dec 30, 2008, for the nose gear drive system, issued Dec 30, 2008, with the caption below.



And here is a link to the full patent document.

http://www.wheeltug.gi/patents/US7469858.pdf

“Delta Air Lines is the launch customer and development partner for the first units which will be for the Boeing 737NG, with delivery of the first units slated for 2010 immediately following FAA certification. Delta Air Lines holds the rights to installation and maintenance of WheelTugs.” This sounds like the first installation will be a Delta retrofit, and here is a link to the rest of the related story: http://en.wikipedia.org/wiki/Wheeltug.

It sounds like this might be a real deal, and time will tell, by 2010, according to the current information.

Here is one more link to WheelTug’s own site where you can see more information: http://www.wheeltug.gi/.

Let's keep an eye on this one.

PS: Anyone remember DC9/MD80 operators doing tugless pushbacks using reversers? I am sure that I saw somebody, maybe Continental, doing it in the late 1980's or early 1990's.

I've been in several MD80s in the past few years that did self-pushbacks with reversers. Alaska did them before they got rid of their last MD80s, and I believe a few other airlines still do them.

Does Wheeltug have an STC yet?

Cert Status
 

Bunk
 

Put the "Chorus/MeshCon" units in a ground tug. An A/C is a poor truck, and a hobbled bird with even the bare necessities of "truck stuff" on board while aloft. This is idiocy. If 1/2 the engineering went into ground ops instead of "Innovation" (TM), we'd have more mobile tugs pulling a/c from the ramp to the Hold/Short and from the High Speed back to the Gate.

Also, while you're at it, let's have some Meshcons on my Audi and Prius.

A few years back I was trying to persuade a pal to start a company with me - making powered wheels. This was to be for cars.

There is only one way for the alternative fuel thing to work, and that's to get rid of all complexity. No I. No drive train from conventional motor(s).

The wheel was to be the inappropriately named Stator. No power had to be conveyed to a rotating part. Two, or even four computer-controlled wheels will be the future...though I probably won't be around to see it.

About the only way I could see a sizable aircraft - and that's most of them these days - being self propelled, would be for several of the main wheels being powered. The idea that the squitty nose wheels could do the job leaves me totally non-plussed!

The main-wheel powered hubs wouldn't be the problem, it's the powering of such devices that will be difficult. Hundreds of cycles of gear-hauling, with zero danger of frayed hi-power cables. Light flexible conductors, that offer very little resistance even after they're loaded. Harder to do than you would think.

Even hotter things being stowed in the wheelbays? Breaks get hot during long taxi-runs, so that shouldn't be too problematic, but as for putting a HOT motor into the electrics-busy area up front. I don't like that at all. I defy a motor that's pulled a 747 a mile, to be anything but hot.

Right now I would put my money on a cockpit controlled removable mini-tug. But when that's been fueled by whatever...and the aircraft has been cooled and aired...the net gain is starting to slip away.

Things are progressing, especially on the negotiation front - very busy. Development is also progressing, but the economic climate doesn't help.... Funding is still an issue. The good news is the family of companies have no debt! Lately that looks quite smart.....

Delta is still our launch customer & things are broadly on schedule for 2010.
Look out for a completely revamped website soon. More news ASAP. Maybe some interesting pictures showing the technical progress. Work continues.

And as for towing aircraft all over the place. It doesn't work. As it appears likewise some of the aircraft afterwards.... The high profile tests that were conducted about a year ago were abandoned quite soon after commencement. Mind you some of the green lobby may well have felt a bit off colour after their wrongful accusations on that abandonment. Ground tugs are quite aggressive.
-------

Following through on your link to MotorTrend, (+ today's interest) you might find Chorus™ for Cars interesting. Quite topical at the moment. Series Hybrid is the way to go (literally) - until there is radical advancement on the mobile electrical storage / supply issue.

There is also a more recent MotorTrends article that shows great insight. Anybody & everybody are building prototypes. But where are they going to source the essential elements required to build 10s of millions based on those prototypes? You think those prototypes are expensive now, with a ~$20K surcharge on them, wait until market forces drive up the price of those rare key elements. Forget economies of scale. Parallel Hybrids are VERY complex.
Nothing exotic is required to construct Chorus Motors. Simply a better motor.

I'm having trouble understanding how the above post is not a self-serving advertisement. Last time I checked, PPRuNe was an aviation forum so why the discussion of hybrid technologies for cars?