reverse thrust at the gate

[onthehill2]

Hello to all.
Ieve been an avid reader for some time but never found the answer to something I saw at Salt Lake on a stopover to Vegas. Instead of using a tug to push back I saw quite a few aircraft using reverse thrust to back away from the gate. Never seen this in the UK and was wondering what the carriers/manufacturers position is on using that procedure?

[Desk Jockey]

It's called powerback or power back. You will find more by googling.

[Check Airman]

I believe DC9's and the MD80 series were approved for powerback by the manufacturer. Even then, the airline would have to approve it. Don't know if anybody still does it though.

[onthehill2]

I wonder what the engine manufacturers state though. I cant think that going from cold to a high thrust level in a short space of time can do the engines a great deal of good

[mustangsally]

Eastern Airlines was doing power backs, starting in the mid 80's. B-727's, DC-9's. Ramp had to be level or sloping away from the terminal. Power was really minimal. Power was added for a forward roll of a couple of inches then reverse thrust. Turns left or right were normal.

[Final 3 Greens]

I've seen it done quite often on turbo props around Europe.

MXP springs to mind as one example.

[Pugilistic Animus]

so is a Boeing 757, but no-one does it

[BigJoeRice]

We also used power backs on our DC9's and 727's only, and then only if the ramp was "not contaminated" - no rain or snow. Although in the winter, we'd sometimes have our 747's with the inboards in reverse and a "wee bit o' power" to help the tug over the icy bits of the ramp. I must admit to being one of those who voiced concerns about engine FOD when we adopted the power back procedure, but I can't recall ever losing an engine to a power back FOD incident or stall. As "mustangsally" pointed out, it didn't take a ton of power to get the beasties moving, so as long as the oil temps were in the green, or yellow and rising, there was no harm to the engine. All you had to remember was that to stop after the power back, it was forward thrust not brakes - not unless you want an embarrassing view of the sky and a "hats-on" interview with the the Chief Pilot.

[NSEU]

I must admit to being one of those who voiced concerns about engine FOD when we adopted the power back procedure, but I can't recall ever losing an engine to a power back FOD incident or stall.

A 747 pilot was telling me that one of his colleagues tried this and max EGT'd 3 (I recall) engines. From that time, he was known as the "6 million dollar man"... for those of you who can remember the TV series ;)

Rgds.
NSEU

[john_tullamarine]

6 million dollar man

.. now, that has the ring of folk legend ... max temp would require a very significant thrust level .. certainly not the level one would be game to use on the ramp ?

[hikoushi]

Maybe he didn't wait till the chocks were out?:eek:

[Capt Claret]

From the Douglas Boeing 717 FCOM (Not for Operational Use) :8

Powerback
* The following limitations are applicable when the airplane is using reverse thrust for reverse taxi (power back):
– Thrust reversers on both engines must be operative.
– Ramp slope limit range is +1% to –2%.
– Application of brakes while backing is prohibited.
– Powerback is not authorized for winds higher than 25 knots, or when ice, snow, or slush is on the ramp or during periods of heavy rain.

And, executing the manoeuvre.

Copyright ©The Boeing Company.

PT.10.2 POWERBACK

General

The powerback maneuver can be an efficient means for the airplane to depart the gate and transition to the taxi phase. There are, however, several factors of safety and passenger comfort that must be considered before commencing the maneuver and during the maneuver itself. These considerations are as follows:
• Flight and ground crew must have completed an appropriate powerback procedures training program.
• Powerback can be performed only in approved ramp areas.
• Thrust reversers on both engines must be operative.
• Ramp must be clear of contamination.
• There must be no more than moderate precipitation.
• Use minimum reverse thrust required.
• Do not use brakes while the airplane is moving rearward.
• Both pilots should have their feet on the floor during the powerback maneuver.
• Verify all personnel and equipment are clear of engines fore and aft prior to initiating movement of thrust levers.

Executing the Maneuver

Check that the FLAP/SLAT handle is in the UP/RET position and that ground crewman (or coordinator) is in position to maintain visual contact with Captain. Having received ground control clearance for powerback, Captain signals readiness to begin powerback with a flash of nosewheel light. Coordinator responds with all clear signal and commences rolling motion with both wands to indicate start of powerback. Captain releases parking brakes and ensures both pilots’ feet are on the floor. Captain applies reverse thrust to reverse idle detent and checks both engines in reverse thrust condition.

NOTE: To facilitate backward movement in some instances of tire flat spots, chocks, or ramp conditions, a few feet of forward taxi may be appropriate prior to applying reverse thrust. Use normal brakes to stop forward roll.

Apply reverse thrust as required to initiate movement. Once motion has commenced, reduce EPR to maintain a safe speed. If the speed is too fast, move one reverse thrust lever to forward thrust idle. If airplane does not move initially with maximum reverse EPR, discontinue powerback operation. Coordinator advises the speed of reverse taxi by varying the speed of wand(s) rotation. To signal a turn, coordinator points downward with his right or left hand. Downward pointing hand indicates direction the tail should move and direction the Captain should turn the nose gear steering wheel. When reverse taxi is complete, coordinator will give the come ahead signal. Captain should then place reverse thrust levers full down and apply forward thrust as required and transition to normal taxi.

Emergency Stop

If an emergency stop is required, coordinator will discontinue the rolling motion of the wands and immediately signal forward taxi. Captain should respond immediately by placing reverse levers full down and applying forward thrust as required.
[END]

[Re-entry]

B744 Limitations.

'Backing the airplane with use of reverse thrust is prohibited.'

[Feather #3]

In the QF case, it was Damascus and the engines stalled in reverse having overrun the taxiway exit and tried to do a 3-point turn in a B742 := [where, BTW, you could use idle reverse to help the tug; usually in icy locations.]

After finding a tug and an appropriate borescope, they got on with the job.

And the Capt. is better known as "Calamity", which sums up the highlights of his career [he use to say he was the only supervisory pilot with a velcro star!!]

G'day ;)

[ITCZ]

DC-9, MD-80, B717, powerback is ok by FCOM as per Claret's post.

It looks like this.....

YouTube - AirTran Boeing 717 Powerback From Gate (http://youtube.com/watch?v=3_-NbqX1ypI)

It is not always a good idea, however....

Air Florida 90 air crash (http://www.pilotfriend.com/disasters/crash/airflorida90.htm)

"At 3:23pm, Palm 90 was cleared to push from the gate. The tug tried to push the 737, but snow that had accumulated on the ground caused it's tires to spin. Wheaton then suggested that, contrary to policy, they would use the aircraft's reverse thrust to assist in the push. The reversers were engaged for about a minute and a half, but were only successful in throwing up slush and snow. Another tug was brought in with chains and the aircraft was successfully pushed back."

[Check Airman]

Does anybody know why it seems to be restricted to planes with rear-mounted engines? What's so bad about doing that with the engines under the wings? Is it simply because the engines are closer to the ground and the risk of ingesting FOD is greater?

[bubbers44]

Yes, because of FOD.

[WHBM]

I've seen plenty of jet powerbacks over the years in the USA, but never with the same types elsewhere.It seems to use a lot of thrust/noise/fuel for a limited distance backwards. Possibly with more expensive fuel in Europe it's just cheaper to have a tug.

Scot Airways always did it away from the Edinburgh terminal with their Dornier 328s headed for London City, marshalled backwards. Not known another turboprop operator to do it in the UK. I've always been on the jet on the route in recent times, do they still do it with the Dorniers ?

[icarusone]

Haven't seen it as much lately but American Airlines used a thrust-reverse taxi on its MD-80s often (even at its hub).

Procedure was to pull forward a couple of feet to reduce the soft spot on the tyre after sitting for some time. Thrust reversers were then applied to back up. Forward thrust was used to come to a stop (or forward motion so that brakes could be applied).

[RJ Kanary]

A retired avionics tech informed me that Unfortunately Still Allegheny Airlines put a stop to power backs in the eighties.One of the reasons cited...........those windows on the terminal buildings are expensive. <G>

[pattern_is_full]

"All you had to remember was that to stop after the power back, it was forward thrust not brakes - not unless you want an embarrassing view of the sky and a "hats-on" interview with the the Chief Pilot."

I was going to say....! Note that a nose-wheel plane will be temporarily converted to a tail-dragger when going BACKWARDS under power (location of CG relative to wheels). With enough speed you could even ground-loop it, I expect, although a "tail-over" would probably occur first.

As a pax I've ridden through several power-backs over the years and thought it a neat idea - but in an era when some (Virgin?) are suggesting tractoring all the way to the RWY threshold, burning Jet-A just to go backwards a few feet seems like an idea whose time has passed.

[BEagle]

I seem to recall that, shortly after the Soviets had shot down an airliner, the ramp staff at Heathrow had some form of strike and refused to let an Aeroflot airliner have a pushback.

Whereupon the Russian announced that he'd back his Il-62 off the parking slot.

This was refused until the Terminal staff had cleared everyone from the area as they were concerned that the windows might be blown in.

[AirRabbit]

"At 3:23pm, Palm 90 was cleared to push from the gate. The tug tried to push the 737, but snow that had accumulated on the ground caused it's tires to spin. Wheaton then suggested that, contrary to policy, they would use the aircraft's reverse thrust to assist in the push. The reversers were engaged for about a minute and a half, but were only successful in throwing up slush and snow. Another tug was brought in with chains and the aircraft was successfully pushed back."
This was an unapproved, ill-advised, and practically useless procedure that gained nothing and, despite a lot of opinions to the contrary, did NOT contribute to the stall and crash after takeoff.

[lomapaseo]

This was an unapproved, ill-advised, and practically useless procedure that gained nothing and, despite a lot of opinions to the contrary, did NOT contribute to the stall and crash after takeoff.

I take it then that you do not believe the theory that the reverse at the gate contributed to the nose dome Pt (EPR) probes on the engines to beome plugged with congealed snow?

[TWApilot]

onthehill2,

You mentioned going from low-to-high power in short time not being good on the engines. Actually, a powerback doesn't really require a very high power setting. You just select reverse thrust, and just a small increase in power, similar to the amount needed to taxi forward, will move the airplane backwards. So you are not going to shock the engines any more than you would when pushing the power up to taxi forward.

Regarding terminal windows, this procedure is fairly common at some places, with no ill effects to the windows. It is always done with tail-mounted engines, so they are quite some distance back.

All that being said, I've never been a fan of powerbacks due to FOD concerns, even with tail-mounted engines. I think it is an unnecessary risk.

[digiteyes]

A major factor against the use of powerback is increased useage of fuel.

If it costs airlines a few extra $$... they usually prohibit the practice.