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Towing Planes From The Gate To The Runway  
User currently offline4tet From Spain, joined Sep 2007, 114 posts, RR: 0
Posted (3 years 4 months 1 week 6 days 10 hours ago) and read 6023 times:

Seeing the line of planes that usually builds in some busy airports, sometimes more than 1 hour wait, I was thinking:

Would make sense to tow the planes till almost the runway to save fuel? ( I know that means a lot more of towing tugs... )

Otherwise, build some track or similar where the planes could attach in the front-wheel (on the taxiway) or maybe an electric motor also in the front-wheel?

Obviously the aim of these measures would be to start the engines only the time needed to warm-up before takeoff.

How many gas is burned in a line like mentioned above, in a A340 B777 or B747?

Cheers,
R.

23 replies: All unread, jump to last
 
User currently offlinewilco737 From Greenland, joined Jun 2004, 8991 posts, RR: 76
Reply 1, posted (3 years 4 months 1 week 6 days 9 hours ago) and read 6010 times:
AIRLINERS.NET CREW
HEAD MODERATOR

Damn, just made a long post, then hit the "post reply" and then it was moved already...   

Quoting 4tet (Thread starter):
therwise, build some track or similar where the planes could attach in the front-wheel (on the taxiway) or maybe an electric motor also in the front-wheel?

huge electric motor for an 748 with 425 tons or even bigger for an A380.... Lots of weight to carry additionally. Doubt that's gonna happen.

Quoting 4tet (Thread starter):
Obviously the aim of these measures would be to start the engines only the time needed to warm-up before takeoff.

Yes, they need a couple of minutes until you are allowed to set take off thrust.

Quoting 4tet (Thread starter):
How many gas is burned in a line like mentioned above, in a A340 B777 or B747?

We usually carry up to 1 ton of taxi fuel, depending on airport and taxi time. At airport like JFK or so we take a little more. Depening on expected traffic etc etc.

being towed to the runway, I don't think that's gonna happen. During that time the APU is running as well, to provide electricity and pneumatic air to the air condition. So that's a bit of fuel you use as well. If the APU is not working, you have to start an engine at the position anyway for the above mentioned reason.
If you are towed to the runway and then one engine doesn't start up or you have some technical issues you are away from the gate, need to taxi back to the parking stand or being pulled back there. Many systems can only be observed if they are working properly after the engines have been started.

So, I personally doubt that's happening soon.

wilco737
  



It it's not Boeing, I am not going.
User currently offline4tet From Spain, joined Sep 2007, 114 posts, RR: 0
Reply 2, posted (3 years 4 months 1 week 6 days 9 hours ago) and read 6004 times:

1 tm 'means' something like $600, am I right?

User currently offlinewilco737 From Greenland, joined Jun 2004, 8991 posts, RR: 76
Reply 3, posted (3 years 4 months 1 week 6 days 9 hours ago) and read 6003 times:
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Quoting 4tet (Reply 2):
1 tm 'means' something like $600, am I right?

What is 1 tm?! You mean 1 ton? Depends on the fuel cost at the airport where you are. But I think around $600 sounds about right.

wilco737
  



It it's not Boeing, I am not going.
User currently offline4tet From Spain, joined Sep 2007, 114 posts, RR: 0
Reply 4, posted (3 years 4 months 1 week 6 days 9 hours ago) and read 5999 times:

Well, tm I think is the symbol we use in Spain to express Metric Ton...

Back to the topic, I suppose then that $600 is not a big deal for a 10hr flight of a big airliner...

Maybe this will come someday via eviormental rules or something similar to prevent the pollution on the areas nearby the airports

Thank you for the info!!


User currently offlinewilco737 From Greenland, joined Jun 2004, 8991 posts, RR: 76
Reply 5, posted (3 years 4 months 1 week 6 days 9 hours ago) and read 5988 times:
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Quoting 4tet (Reply 4):
I suppose then that $600 is not a big deal for a 10hr flight of a big airliner...

Generally no. But airlines try to reduce the fuel costs as much as possible Even 50 kgs savings for each flight in a huge fleet with many fleets can safe millions of dollars... That's why there are many ideas to reduce the minimum fuel on board.
There are plans for flights without alternate already. And reduced contingency fuel etc etc.

Quoting 4tet (Reply 4):
Maybe this will come someday via eviormental rules or something similar to prevent the pollution on the areas nearby the airports

Maybe. I am sure airports, airplane manufacturs and many other engineers think about possibilities.

wilco737
  



It it's not Boeing, I am not going.
User currently offline330guy From Ireland, joined Nov 2010, 453 posts, RR: 2
Reply 6, posted (3 years 4 months 1 week 6 days 8 hours ago) and read 5968 times:

Didnt VS trial being towed part of the way to the runway a few years ago at LHR and decided against the idea??

[Edited 2011-04-10 07:32:02]


Aircraft flown: a300/10/20/21/30/40, b727/37/47/57/67/, DC9, MD80-90, l1011, f50, atr42/72, shorts360, pc12
User currently offlineGST From United Kingdom, joined Jun 2008, 930 posts, RR: 0
Reply 7, posted (3 years 4 months 1 week 6 days 3 hours ago) and read 5834 times:

Quoting 330guy (Reply 6):

If I recall it was quietly dropped after worries of excessive nose gear leg fatigue and stressing.


User currently offlineMax777geek From Italy, joined Mar 2007, 538 posts, RR: 0
Reply 8, posted (3 years 4 months 1 week 6 days 2 hours ago) and read 5792 times:

Quoting 4tet (Thread starter):
Would make sense to tow the planes till almost the runway to save fuel? ( I know that means a lot more of towing tugs... )

standing to recent environmental studies, that wouldn't differ much in terms of enviromental impact, whatever you feeds your tugs like.


User currently offlinecobra27 From Slovenia, joined May 2001, 1011 posts, RR: 0
Reply 9, posted (3 years 4 months 1 week 6 days 2 hours ago) and read 5785 times:

Quoting wilco737 (Reply 1):
huge electric motor for an 748 with 425 tons or even bigger for an A380.... Lots of weight to carry additionally. Doubt that's gonna happen.

It could also be hydraulical to save weight and it would easily avoid pushback aswell. I don't really think it is a technical problem. And it is logical that it will save money, and will surely happen in the future. Military helicopters have long run up times and military piston engines in slovenian army never used mixture even at altitude.

There is fuel being produced from corn and other plants while at the same time huge quantities of natural gas and heating oil are being burned.

So in my opinion is they just don't think green or economical.


User currently offline4tet From Spain, joined Sep 2007, 114 posts, RR: 0
Reply 10, posted (3 years 4 months 1 week 5 days 14 hours ago) and read 5623 times:

Quoting cobra27 (Reply 9):
standing to recent environmental studies, that wouldn't differ much in terms of enviromental impact, whatever you feeds your tugs like.

I don't really think a tug would spend a metric ton of fuel to push the plane till the runway. The tug would be able to start and stop while the plane hasn't got to move, so this I suppose its a big big savings in front of 4 turbines runing, sometimes for a long long time...


User currently offlinecobra27 From Slovenia, joined May 2001, 1011 posts, RR: 0
Reply 11, posted (3 years 4 months 1 week 5 days 13 hours ago) and read 5616 times:

Funny funny!!

4tet You put other text in my quote, that happened to me when I unexpectedly added text in other post, so much fun when I saw his reaction. Check my replie 9 and then quote


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25106 posts, RR: 22
Reply 12, posted (3 years 4 months 1 week 5 days ago) and read 5446 times:

Quoting 4tet (Reply 10):
I don't really think a tug would spend a metric ton of fuel to push the plane till the runway. The tug would be able to start and stop while the plane hasn't got to move, so this I suppose its a big big savings in front of 4 turbines runing, sometimes for a long long time...

Also have to consider the salaries of the many additional tug operators (and the cost of the tugs themselves) you would need at a busy airport like JFK or LHR.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 13, posted (3 years 4 months 1 week 4 days 21 hours ago) and read 5397 times:

I have to applaud anyone who thinks outside the box, and in its basic form, I think this idea holds water. However, it's not as simple as just finding a tug, hooking it up, and off you go! There are quite a few other things to consider, and here are a few just off the top of my head:

First of all, how fast would a tug hauling a fully-loaded A380 be able to go? Three, maybe five knots max? An airliner under its own power typically does what, ten to twenty knots? The whole taxi process would be slowed down and bottlenecks could easily form.

You would also need to have every aircraft participate in the program. I can imagine an A380 under tow moving at the blistering pace of three knots with a congo line of twenty self-powered aircraft stacked up behind it. Every airplane that wasn't under tow would be wasting additional fuel while it was creeping along. If everybody were strapped to a tug, it would be a different story, but I have my doubts you could convince every operator to jump on board.

In order to tow every aircraft, you would have to purchase many additional tugs to keep things moving. You would also have to hire additional tug drivers to handle the additional workload. Neither of these would save any money.

There would also be an additional burden placed on ATC. The tugs are now no longer confined to the ramp, but are now in the movement areas and crossing active runways. While the tug is connected to an aircraft, the tug would have to be communicating with ground and/or local control while in transit both to and from the runway. Once the tug unhooks and returns to the ramp, it has to again cross whatever runways it crossed on the way out. I fear that the chances of a runway incursion would escalate dramatically.

During the tug's return trip, unless there is a vacant parallel taxiway that could be used, additional tug lanes would have to be created. Also, most airports would need larger holding pads to contain all the departing aircraft while they fire up their engines. Many airports don't have the space to easily expand, and any new pavement wouldn't come cheap.

Also, consider a major domestic hub like ATL or DFW. These airports are flooded with regional jets that make multiple flights a day. If it takes five minutes to taxi to the active versus fifteen with a tug, you could easily lose an hour or more per day. The utilization of these aircraft could take a hit, not to mention crew duty times. Airlines depend on these little jets to haul as many passengers as possible, i.e. make as many revenue flights as possible. Also, airlines like Southwest pride themselves on their quick gate turnarounds. Any time saved at the gate could easily be lost while being towed to the runway.

Again, I'm not saying that the concept of towing aircraft to save fuel is flawed. You just need to consider all of the logistics behind it to determine if the idea would indeed be worth the effort and save money in the long run.

PC



In-trail spacing is a team effort.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (3 years 4 months 1 week 4 days 21 hours ago) and read 5383 times:

Quoting PapaChuck (Reply 13):
First of all, how fast would a tug hauling a fully-loaded A380 be able to go? Three, maybe five knots max?

The big towbarless tugs can pull pretty much anything at speeds considerably faster than you want an aircraft with passengers on it to be going...I don't think speed is the problem here.

Tom.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 15, posted (3 years 4 months 1 week 4 days 21 hours ago) and read 5375 times:

My concern is how fast a tug can safely tow an aircraft. Tugs may be able to move rather quickly, but how quickly can they stop? That's a lot of strain being put on the nose gear during a panic stop. Is a tug's braking ability with a heavy load comparable to an aircraft's braking ability?

PC



In-trail spacing is a team effort.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 16, posted (3 years 4 months 1 week 4 days 19 hours ago) and read 5355 times:

Quoting PapaChuck (Reply 15):
Is a tug's braking ability with a heavy load comparable to an aircraft's braking ability?

Nowhere close. But a tug will never have to stop an airliner from the kinds of speeds that aircraft brakes do, so there's no particular reason they need to be comparable. Nose gear stress is likely more limiting than tug braking capability.

Tom.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 17, posted (3 years 4 months 1 week 4 days 18 hours ago) and read 5320 times:

Very true, Tom. Apples to oranges when you compare the two brake systems. My concern is that a tug wouldn't be able to safely stop an aircraft going twenty knots as quickly as the aircraft's own brakes could. The tug driver could slam on the brakes, but would the nose gear be damaged in the process? The tugs might need to travel slower to keep a million pounds of Airbus from becoming a runaway freight train.

PC



In-trail spacing is a team effort.
User currently offlinecobra27 From Slovenia, joined May 2001, 1011 posts, RR: 0
Reply 18, posted (3 years 4 months 1 week 4 days 13 hours ago) and read 5279 times:

Look, the plane can still fire up the engines and taxi conventionally even if there is no tug avaliable.

Quoting wilco737 (Reply 1):
huge electric motor for an 748 with 425 tons or even bigger for an A380.... Lots of weight to carry additionally. Doubt that's gonna happen.

Ok Tesla roadstes car of about 250 Hp weight 30 kg (70 lbs). "250 Hp would suffice for A380 withpout a problem, Hydraulic motor could be even less, but APU would probably have to be beefed up

Quoting PapaChuck (Reply 17):
My concern is that a tug wouldn't be able to safely stop an aircraft going twenty knots as quickly as the aircraft's own brakes could. The tug driver could slam on the brakes, but would the nose gear be damaged in the process

True, true. Nose gear on current aircraft is not designed for long distance towing , almost for pushbach and slow towing across apron. Small motor on the main gear would probably do the job, better than tugs, stopping wouldn't be a problem

I think a small motor would do the job on tha main landing gear would do the job better, small airports would haven't to have so many tugs.

And taxing with engines running increas engine wear and tear.
But I don't think we will see this happening in the near future. And if it happens and Airbus does it they will probably be the greenest thing that anyone has ever done on the planet


User currently offlineblueflyer From United States of America, joined Jan 2006, 3967 posts, RR: 2
Reply 19, posted (3 years 4 months 1 week 4 days 13 hours ago) and read 5274 times:
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Quoting cobra27 (Reply 18):
I think a small motor would do the job on tha main landing gear would do the job better, small airports would haven't to have so many tugs.

I'm not sure we're anywhere near that kind of solution being used in the real world.
For one thing, a motor needs an outside power source, be it an engine or a beefed up APU. Using the APU as power source probably would burn less fuel than using an engine, but there's the higher weight of the APU to contend with, and not just for taxi as is the case with taxi fuel, but for the entire flight all the way to the arrival gate.

A stand-alone engine would probably work better, but again weight is a major issue. One engine probably wouldn't do it, several would be needed, with the caveat that they collectively would have to burn a lot less fuel than a normal taxi does to account for the fact that this extra weight has to again, be carried to the end of the flight.

Another issue to contend with is the increased maintenance costs and the higher risks for AOG that adding a few more engines to an already complex vehicle would entail.

Without being an expert in the field, I'm thinking that advances in light batteries and quick-start engines currently driven (no pun intended) by hybrid/electric car developments will probably translate to commercial aviation before the weight and maintenance issues of on-landing-gear engines are solved, and aircraft would be able to power on their engines just long enough to move, with light, high-capacity quick-charge batteries powering aircraft system during non-movement phases.



I've got $h*t to do
User currently offlinecobra27 From Slovenia, joined May 2001, 1011 posts, RR: 0
Reply 20, posted (3 years 4 months 1 week 4 days 2 hours ago) and read 5194 times:

Interesting reply

Well am not aviation engineer or expert also, but I did study aviation course on mechanical university, so I have some technical foundation

So you would put a battery on a plane , but not enlarge APU, I would do otherwise. Since A320/737 has around 150 hp and I think that should do it, 787 which is more electric has powerfull APU. Batteries are not weight wise if you ask me. It would made more sense to tow/power high cycle aiframe like 737, than to put a really have motor on superlong range plane

Quoting blueflyer (Reply 19):
will probably translate to commercial aviation before the weight and maintenance issues of on-landing-gear engines are solved

Higher maintenace cost, true (but we are talking huge saves in fuel), that should be more than ofset. Complicated maintenance, probably not is not crucial element.
Yes, It would have to work well even with all stress when landing, maybe some sort of clutchable shaft

Keep in mind that it would decrease engine total time, decrease noise at airports, decrease jet blast danger, not burning fuel when in line, decrease pollution at airports.

Jet engines at idle don't burn so cleanly, exhaust gas contains 0,1-3 % (less on newer engines) of unburnt fuel. So there is also emmision benefit


User currently offlineyeelep From United States of America, joined Apr 2011, 653 posts, RR: 0
Reply 21, posted (3 years 4 months 1 week 4 days 2 hours ago) and read 5182 times:

Autonomous taxiing Is been actively studied by both major aircraft manufactures. I believe there was a previous thread about this.

Heres a articles about airbus's efforts.

http://sky-is-our-home.blogspot.com/...-develops-autonomous-aircraft.html


User currently offlinecobra27 From Slovenia, joined May 2001, 1011 posts, RR: 0
Reply 22, posted (3 years 4 months 1 week 4 days ago) and read 5164 times:

It only needs a push and it will happen. Also long landing approaches in landing configuration all the way, Steeper landing aproaches in cleaner configuration. And routes that change according to prevailing winds

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 23, posted (3 years 4 months 1 week 3 days 18 hours ago) and read 5112 times:

Quoting cobra27 (Reply 18):
Small motor on the main gear would probably do the job, better than tugs, stopping wouldn't be a problem

Ah ha! Now we know why the A380 has an axle on each side with no brakes...it's for future electric motor retrofit!

Tom.


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