User avatar
TWA772LR
Topic Author
Posts: 3714
Joined: Thu Nov 17, 2011 6:12 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 2:28 am

Which is better to use during push back? What are advantages and disadvantages? I know AirTran used reversers with their 717s when I was last in ATL, but that was 2003ish... Which airlines use their reversers for push back?

All replies welcome. Feel free to add and ask anything.  
Beauty is watching a 787 bank to make a short final. Bliss is watching that 787 with a good beer. Nirvana is all of that with a beautiful woman on your side.
 
User avatar
Starlionblue
Posts: 17097
Joined: Fri Feb 27, 2004 9:54 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 2:40 am

Tug is the way to go.

Tug advantages:
- Uses less fuel.
- Does not produce dangerous jet blast.
- Makes less noise.
- Does not risk tipping the plane on its bum-bum.

Powerback advantages:
- You don't need a tug. Heh...
- You can't turn the nose wheel past its limits.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
TWA772LR
Topic Author
Posts: 3714
Joined: Thu Nov 17, 2011 6:12 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 2:45 am

I imagined the tug would be best. One would think that the nose gear would have something on it to keep it from turn it too much, we know it doesn't have it on A320s.  Thanks for the reply!
Beauty is watching a 787 bank to make a short final. Bliss is watching that 787 with a good beer. Nirvana is all of that with a beautiful woman on your side.
 
User avatar
Starlionblue
Posts: 17097
Joined: Fri Feb 27, 2004 9:54 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 3:45 am

Quoting TWA772LR (Reply 2):
One would think that the nose gear would have something on it to keep it from turn it too much, we know it doesn't have it on A320s. 

An expert would have to weigh in but I think the tug is strong enough to break any locks on the gear turning radius.

As for 320s and the nose wheels turning perpendicular to the direction of travel, that's a safety feature. In some particular failure situations, the gear will fail perpendicular, and thus be in a predictable position, rather than at an unknown angle which would make a landing really hairy.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
TWA772LR
Topic Author
Posts: 3714
Joined: Thu Nov 17, 2011 6:12 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 4:02 am

Quoting Starlionblue (Reply 3):

Why wouldn't airbus just have the landing gear lock in the normal, straight-ahead (lack of a better word) setting?
Beauty is watching a 787 bank to make a short final. Bliss is watching that 787 with a good beer. Nirvana is all of that with a beautiful woman on your side.
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 4:24 am

Quoting TWA772LR (Reply 2):
One would think that the nose gear would have something on it to keep it from turn it too much

The tug/towbar combination has enough power to overcome such things.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
User avatar
DarkSnowyNight
Posts: 1792
Joined: Sun Jan 01, 2012 7:59 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 4:29 am

Quoting Mir (Reply 5):

The tug/towbar combination has enough power to overcome such things.

I think purposely. If the NLG locks and trunions were string enough to resist a tug overdoing it there, there would probably significant risk of frame damage.


On topic... Most airports have officially "no-no'd" powerbacks. I got to do one once, and looking at how vorboten it is at most places, that will probably have to do for this life.
Be A Perfectionst, You're Nothing If You're Just Another; Something Material, This Isn't Personal...
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 5:10 am

Quoting Darksnowynight (Reply 6):
I think purposely. If the NLG locks and trunions were string enough to resist a tug overdoing it there, there would probably significant risk of frame damage.

Oh definitely. They're not there so much to prevent oversteering as to alert the crew that it's happened, and that an inspection needs to be done.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 5:14 am

Quoting TWA772LR (Thread starter):

Which is better to use during push back?

Tug.

Quoting TWA772LR (Thread starter):
What are advantages and disadvantages?

The only advantage of power back is that you don't need a tug...by almost every other metric, it's inferior.

Quoting Starlionblue (Reply 3):
I think the tug is strong enough to break any locks on the gear turning radius.

The tug is more than strong enough. However, assuming the appropriate tow bar is in use, the fuse pins in the towbar should let go before damage to the nose gear occurs.

Tom.
 
ak907
Posts: 39
Joined: Wed Mar 07, 2012 10:56 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 6:06 am

On any towbar, the shear pins will break first. On the 747, if the shear pins do not break, the bracket where the towbar connects to the nose gear will break. If that doesn't break, the nosegear turning actuator's piston will bottom out in the cylinder and then something serious will happen.
 
Max Q
Posts: 5634
Joined: Wed May 09, 2001 12:40 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 6:42 am

One of the most serious disadvantages of 'powering back' was the ingestion of debris (FOD) from the ramp.



Using a tug is far more controlled, safer and easier on the machinery !
The best contribution to safety is a competent Pilot.
 
User avatar
Starlionblue
Posts: 17097
Joined: Fri Feb 27, 2004 9:54 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 6:49 am

Quoting TWA772LR (Reply 4):
Quoting Starlionblue (Reply 3):

Why wouldn't airbus just have the landing gear lock in the normal, straight-ahead (lack of a better word) setting?

If memory serves because the gear does not have a mechanical center "detent" per se. The center position is determined somewhere else in the steering logic. So if you "lose the signal" from the tillers and pedals there is no way for the gear to know where center is. On the other hand there will be mechanical stops on both sides.

But I may be remembering that wrong.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 7:05 pm

To the best of my knowledge nobody regularly does Powerbacks anymore. I'm told the AA still has it as an approved procedure and may rarely do it if a tug isn't available, but it's not a regularly done procedure anymore.

NW was the last airline I know of to stop doing it - around 2006 with their DC-9s.
AA and FL both stopped it in 2005 - AA with their MD-80s, FL with their 717s.
 
User avatar
DocLightning
Posts: 19769
Joined: Wed Nov 16, 2005 8:51 am

Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 7:29 pm

Quoting BoeingGuy (Reply 12):
To the best of my knowledge nobody regularly does Powerbacks anymore. I'm told the AA still has it as an approved procedure and may rarely do it if a tug isn't available, but it's not a regularly done procedure anymore.

Also, it can ONLY be done with high-mounted engines. It cannot be done with under-wing engines because the risk of FOD ingestion is too high. Remember, under forward thrust, FOD will tend to get blown away from the inlet by the exhaust gas. In reverse thrust, FOD will tend to get blown TOWARD the inlet. When you are at high speed on the runway, this is less important since it doesn't get blown far enough forward, but when you are at a near standstill, you are absolutely at risk of blowing something into the path of the inlet.

Other issues:
1) Wear and tear on the engine
2) The aircraft's CG is (by design) very close to the MLG. For this reason, you have to stop the backwards roll with forward thrust. If you try to stop a backwards roll with the brakes, you are likely to tip the airframe up on its butt, which involves large amounts of paperwork, not to mention that it makes you look awfully silly.
3) The pilots don't have a rearview mirror, so if they are about to back into something, one of the spotters has to tell them, and then they have to kill the reverse thrust and then use forward thrust to stop, all of which takes a few seconds, by which point they will probably have run into whatever it was.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 8:49 pm

Quoting DocLightning (Reply 13):
Also, it can ONLY be done with high-mounted engines. It cannot be done with under-wing engines because the risk of FOD ingestion is too high.

In practice, what you say is mostly true. However, the 757 and 737 are authorized to do powerbacks. Several customers have done it with the 737 and 757 in years past. AA tried it with the 757 but then decided not to adopt it. Britannia had a supplementary procedure in their Ops Manual for powerbacking a 757.

The 747, 767, 777 and 787 have AFM (Airplane Flight Manual) Limitations stating that "backing the airplane with reverse trust is prohibited". As I said, the 737 and 757 do not have such limitations.
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Fri Jun 22, 2012 11:16 pm

Powerbacks are an oft repeated topic on A.net, perhaps because they were cool to watch.

You guys might enjoy these videos:

http://www.youtube.com/watch?v=KdWEArjevZM

http://www.youtube.com/watch?v=sJQGNAUk5Ao&feature=related
 
Max Q
Posts: 5634
Joined: Wed May 09, 2001 12:40 pm

RE: Push-Back Tug Versus Thrust Reversers

Sat Jun 23, 2012 1:55 am

Quoting BoeingGuy (Reply 14):
However, the 757 and 737 are authorized to do powerbacks

My B757 manual does not approve powerbacks.
The best contribution to safety is a competent Pilot.
 
bohica
Posts: 2304
Joined: Tue Feb 10, 2004 3:21 pm

RE: Push-Back Tug Versus Thrust Reversers

Sat Jun 23, 2012 2:54 am

Quoting DocLightning (Reply 13):
Also, it can ONLY be done with high-mounted engines. It cannot be done with under-wing engines because the risk of FOD ingestion is too high.

EA used to powerback the 757 when they first got them. I was on a couple 757 flights departing ATL that powered back.


I still miss the good ole days on Eastern 727's back in the 80's during powerbacks. Sitting in the back of one was extremely LOUD, but was fun.  
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Push-Back Tug Versus Thrust Reversers

Sat Jun 23, 2012 6:47 pm

As long as one uses the forward thrust to stop a powerback & NOT brakes its fine.

if a tug is available use it help not to reduce the engine life.
I may not win often, but I damn well never lose!!! ;)
 
User avatar
DocLightning
Posts: 19769
Joined: Wed Nov 16, 2005 8:51 am

RE: Push-Back Tug Versus Thrust Reversers

Sat Jun 23, 2012 7:04 pm

Quoting BoeingGuy (Reply 14):
However, the 757 and 737 are authorized to do powerbacks.

I did not know that. Is that all 737's or just the Jurassics?

Anyway, I know that Airbus is looking into adding a small electric motor to the NLG on the A320.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Sat Jun 23, 2012 8:51 pm

Quoting Max Q (Reply 16):
My B757 manual does not approve powerbacks.
Quoting DocLightning (Reply 19):
I did not know that. Is that all 737's or just the Jurassics?

Anyway, I know that Airbus is looking into adding a small electric motor to the NLG on the A320.

So let me state this differently. There is no AFM limitation in the Boeing 737 (any minor model) or 757 AFMs that prohibit powerbacking those models. I mentioned it is prohibited by AFM limitation on the 747, 767, 777 and 787.

I can't speak for individual operator policies or other regulatory requirements. As I and others have noted, some operators have tried powerbacks with 757s and 737s. Not sure if anyone has done it with the 737NG, but it's not prohibited.

I miss watching (and riding) all the AA MD-80 powerbacks at DFW. It's kind of like the old aggressive noise abatement procedure at SNA in older model airplanes (e.g. not as quiet as the 738 which does a normal takeoff profile there). Pilots and airlines may be happy they things aren't done much anymore, but from a aviation fan point of view some of these past things are missed.
 
BAE146QT
Posts: 981
Joined: Sun Sep 24, 2006 4:58 am

RE: Push-Back Tug Versus Thrust Reversers

Sun Jun 24, 2012 5:28 pm

Since no-one has mentioned it (in this thread at least), attempting to power back in icing/snow conditions was a major contributory factor in the loss of Air Florida flight Palm 90.

For those that don't know, the tug wasn't able to push the 737 back, so the crew attempted to power back to break the snow's lock on the gear. The engines and nacelles took on a huge amount of ice and although it certainly wasn't the only reason the plane went down, it was a large part of it.

If you get a chance, read the NTSB report, or at the very least, the Wiki entry on this crash. It's an eye-opening look into human factors and how something that might look sensible totally isn't, (snuggling up behind the aircraft in front in order to warm your plane up with his jetwash, for example).
Todos mis dominós son totalmente pegajosos
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Sun Jun 24, 2012 6:39 pm

Quoting BAe146QT (Reply 21):
Since no-one has mentioned it (in this thread at least), attempting to power back in icing/snow conditions was a major contributory factor in the loss of Air Florida flight Palm 90.

Yes, and the other factor was being afraid to push the throttles above the target thrust even when ground contact was imminent. We talk about that in our new Ice Crystal Icing procedure. The limits may be erroneous; manually set thrust to keep the airplane doing what you want it to do.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Push-Back Tug Versus Thrust Reversers

Mon Jun 25, 2012 10:10 am

Quoting BoeingGuy (Reply 14):
the 757 and 737 are authorized to do powerbacks

In the early years....but thereafter restricted as tipping over chances existed if stopped by brakes instead of fwd thrust,hence discontinued......Our Company SOP clearly forbids powerback.
I may not win often, but I damn well never lose!!! ;)
 
BAE146QT
Posts: 981
Joined: Sun Sep 24, 2006 4:58 am

RE: Push-Back Tug Versus Thrust Reversers

Thu Jul 12, 2012 6:08 pm

Quoting BoeingGuy (Reply 22):
Yes, and the other factor was being afraid to push the throttles above the target thrust even when ground contact was imminent

According to David Beaty's book "The Naked Pilot", there was a suggestion that they were afraid of exceeding the airline's EPR limits, even though the probes and guages were essentially lying to them. The flew a perfectly servicable aircraft into a river because they were chasing numbers and ignoring the facts of their situation.

I won't criticize them for that because I'm not a commercial pilot and I'm not subject to the pressures that they were. But that was clearly a cultural problem that was just asking for an accident.

Appologies for the slight thread derailing there, but TR pushback was definitely a major factor there.
Todos mis dominós son totalmente pegajosos
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Thu Jul 12, 2012 10:53 pm

Quoting BAE146QT (Reply 24):
According to David Beaty's book "The Naked Pilot", there was a suggestion that they were afraid of exceeding the airline's EPR limits, even though the probes and guages were essentially lying to them. The flew a perfectly servicable aircraft into a river because they were chasing numbers and ignoring the facts of their situation.

I won't criticize them for that because I'm not a commercial pilot and I'm not subject to the pressures that they were. But that was clearly a cultural problem that was just asking for an accident.

Appologies for the slight thread derailing there, but TR pushback was definitely a major factor there.

When ground or water contact is imminent you firewall the engines. Exceeding thrust perimeters or sustaining economic damage to the engines is not a factor. Trying not to crash is.

Swissair 111 was a similar mentally. They have a catastrophic fire developing, but instead of landing immediately like they should have, they were flying in a holding pattern dumping fuel to get down to max landing weight so they'd be "legal"
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Push-Back Tug Versus Thrust Reversers

Fri Jul 13, 2012 1:20 am

Quoting BoeingGuy (Reply 25):
Swissair 111 was a similar mentally. They have a catastrophic fire developing, but instead of landing immediately like they should have, they were flying in a holding pattern dumping fuel to get down to max landing weight so they'd be "legal"

The Swissair 111 crew didn't know they had a catastrophic fire until it was far too late. Even if they'd turned around at the first indication of any issue they wouldn't have made it.

Tom.
 
BoeingGuy
Posts: 3935
Joined: Fri Dec 10, 2010 6:01 pm

RE: Push-Back Tug Versus Thrust Reversers

Fri Jul 13, 2012 5:11 am

Quoting tdscanuck (Reply 26):
The Swissair 111 crew didn't know they had a catastrophic fire until it was far too late. Even if they'd turned around at the first indication of any issue they wouldn't have made it.

Tom.

I sort of disagree. I helped write Boeing's Smoke/Fire/Fumes checklists and thus have studied SW111 and AC797 very extensively.

Bottom line is that you don't need to know you have a catastrophic fire. If you have unidentified smoke and you can't VISUALLY confirm that it's out (there's the wastepaper basket and I see that it's out) you land at the nearest piece of concrete - period. No if and, or gee maybe it's only air conditioning smoke. Get on the ground.
 
User avatar
Starlionblue
Posts: 17097
Joined: Fri Feb 27, 2004 9:54 pm

RE: Push-Back Tug Versus Thrust Reversers

Fri Jul 13, 2012 8:51 am

I think the point is that they should have landed immediately. The fact they wouldn't have made it should not have influenced the decision.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
n92r03
Posts: 355
Joined: Sun Jan 10, 2010 10:46 pm

RE: Push-Back Tug Versus Thrust Reversers

Tue Jul 24, 2012 1:19 am

Quoting Starlionblue (Reply 1):
- Does not risk tipping the plane on its bum-bum.

Classic!

Quoting Starlionblue (Reply 1):
Powerback advantages:

Plus it was just cool to watch/hear.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Push-Back Tug Versus Thrust Reversers

Wed Jul 25, 2012 11:31 am

Unless a tug is not available....The options of using Powerback will always be uneconomical.
I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: No registered users and 8 guests