Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Idle Reverse while vacating

Tech Log The very best in practical technical discussion on the web

Idle Reverse while vacating

Old 2nd Jul 2019, 23:14
  #21 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 64
Posts: 2,419
Originally Posted by 5420N View Post


IAS is what we use (large airbus operator).
Absolutely - the risk of re-ingestion and FOD is primarily related to airspeed, not ground speed.
tdracer is online now  
Old 3rd Jul 2019, 02:04
  #22 (permalink)  
 
Join Date: Feb 2019
Location: shiny side up
Posts: 431
Does anyone here have an opinion with regard to keeping reversers at idle while vacating the runway after landing when the aircraft is still decelerating (i.e. entering the taxiway). Any possible risks associated with doing this?
What is your airline SOP,?...rev thrust or braking?

Aside from all of the FOD risks noted above, this is an engine cycle that is counted for maintenance. Most airlines tend to want to reduce rev thrust cycles and time, to reduce maintenance cycles on the engines.

Brakes/replacement are far cheaper than engines.....
Smythe is offline  
Old 3rd Jul 2019, 03:23
  #23 (permalink)  
 
Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,534
Originally Posted by Smythe View Post

Brakes/replacement are far cheaper than engines.....
Yes, but more than one airline found that the money saved was negated by some order(s) of magnitude by having an aircraft off the end of the runway in the greenery.
compressor stall is offline  
Old 3rd Jul 2019, 07:20
  #24 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 1
Aircraft type doesnít affect the issue too much here. One problem is that in winter with runway conditions reported, very often the turn off taxiways can be much more slippery.
Idle reverse until taxy speed (a very slow taxy speed) is a good idea.
Out in the sticks in summer FOD is the problem, so as long as she brakes OK, stow the reverse.
bill fly is offline  
Old 3rd Jul 2019, 20:29
  #25 (permalink)  
 
Join Date: Sep 2013
Location: USA
Posts: 41
We're to be fully out of reverse by 60 kts.

As many have mentioned, you risk FOD ingestion keeping them out leaving the runway.
Altcrznav is offline  
Old 4th Jul 2019, 01:33
  #26 (permalink)  
 
Join Date: Mar 2006
Location: USA
Posts: 1,448
Originally Posted by Altcrznav View Post
We're to be fully out of reverse by 60 kts.

As many have mentioned, you risk FOD ingestion keeping them out leaving the runway.
I dream for a day when fleet managers stop making up their own procedures.
Check Airman is online now  
Old 4th Jul 2019, 23:01
  #27 (permalink)  
 
Join Date: Sep 2005
Location: ???
Posts: 231
Originally Posted by bill fly View Post
Aircraft type doesnít affect the issue too much here. One problem is that in winter with runway conditions reported, very often the turn off taxiways can be much more slippery.
Idle reverse until taxy speed (a very slow taxy speed) is a good idea.
Out in the sticks in summer FOD is the problem, so as long as she brakes OK, stow the reverse.
aircraft type does affect the issue quite a bit. The lower the engines and the further they are mounted from the fuselage, the higher the effect of FOD. If its too slippery to be taking a RET at high speed then slow it right down on the runway before vacating. Just tell ATC about it.
InSoMnIaC is offline  
Old 4th Jul 2019, 23:53
  #28 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 208
I've seen a handful of mostly corporate types with high tail mounted engines using reverse on taxiways to manage speed.
Tomaski is offline  
Old 5th Jul 2019, 00:41
  #29 (permalink)  
 
Join Date: Sep 2016
Location: USA
Posts: 449
Originally Posted by InSoMnIaC View Post
If its too slippery to be taking a RET at high speed then slow it right down on the runway before vacating. Just tell ATC about it.

That you'll be slowing to a safe speed before turning, is the type of obvious and unnecessary statement that we should not be clogging frequencies with. Like that we won't be taking off overweight or flying slower than stall speed. Duh.

ATC should know that planes have to slow down more for turns when it's slippery out; and if they don't, they'll figure it out quickly enough.
Vessbot is online now  
Old 5th Jul 2019, 04:19
  #30 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
Age: 64
Posts: 2,419
Originally Posted by Smythe View Post
What is your airline SOP,?...rev thrust or braking?

Aside from all of the FOD risks noted above, this is an engine cycle that is counted for maintenance. Most airlines tend to want to reduce rev thrust cycles and time, to reduce maintenance cycles on the engines.

Brakes/replacement are far cheaper than engines.....
At least in the Boeing world, most of what you wrote is simply wrong. Deploying the reverser is not counted as an 'engine cycle' - only a takeoff is counted as an engine cycle. Max reverse N1 is significantly lower than max climb, so it's not really taking anything significant out of the engine, and FOD damage risk is almost non-existent above 80 knots. It is counted as a reverser cycle, but the Boeing MPD tasks assume one reverser cycle per flight cycle so in most cases you'll be doing the reverser maintenance regardless. According to the Boeing R&M types, appropriate use of the reversers on the 777 saves ~$100 per landing in total maintenance costs (not to mention the costs of going off the end). Brakes aren't cheap either.
If you respect the FCOM recommendations on reverser usage - getting them to idle by 60 knots, and stowing by taxi speed, the risk of re-ingestion and associated engine damage are minimal.
The key is to respect the FCOM recommendations - reverse below 60 knots doesn't do much aside from killing the forward idle thrust - so there is really no reason to use them unless getting the aircraft stopped in time is not a sure thing (in which case abusing the reversers is probably preferable to abusing the airframe).
tdracer is online now  
Old 5th Jul 2019, 09:07
  #31 (permalink)  
 
Join Date: Feb 2015
Location: The woods
Posts: 1
Originally Posted by InSoMnIaC View Post


aircraft type does affect the issue quite a bit. The lower the engines and the further they are mounted from the fuselage, the higher the effect of FOD. If its too slippery to be taking a RET at high speed then slow it right down on the runway before vacating. Just tell ATC about it.
Well taking a turn off at high speed wasnít what I discussed - rather the difference between icy conditions, where a taxiway may well not be so well deiced as a runway - and not.
In icy conditions you will use as much of the runway as necessary to decelerate and wonít be trying for an early exit.
If you are prepared by having the reverser in idle, you are in better shape to react to this not uncommon case - particularly if you are first landing after RW opening... The airport ties hard to keep/get the runway open and taxy ways come second.
Generally under such conditions there is less risk of stone ingestion, but snow can be blown loose.
bill fly is offline  
Old 9th Jul 2019, 05:57
  #32 (permalink)  
 
Join Date: Sep 2005
Location: ???
Posts: 231
Originally Posted by Vessbot View Post
That you'll be slowing to a safe speed before turning, is the type of obvious and unnecessary statement that we should not be clogging frequencies with. Like that we won't be taking off overweight or flying slower than stall speed. Duh.

ATC should know that planes have to slow down more for turns when it's slippery out; and if they don't, they'll figure it out quickly enough.

Get off your high Horse buddy. If you donít have any thing constructive to add then I suggest you keep your negativity to yourself.

It is quite reasonable to advise ATC When they need you to expedite vacating. Or there is guidance in the AIP advising you to use a particular exit which you cannot make or requiring you to vacate within a number of seconds after landing (eg in china).
InSoMnIaC is offline  
Old 9th Jul 2019, 13:14
  #33 (permalink)  
 
Join Date: Jun 2000
Location: Australia
Posts: 3,871
While training crews in Asia who were used to their company procedures (not necessarily Boeing FCTM procedures), it was noticed they tended to completely cancel reverse thrust at the 60 knots call during the landing run. At the call of 60 knots, they would slam the reverse thrust levers fully down from full reverse (Boeing 737). This would cause the aircraft to momentarily accelerate down the runway while the pilot was still also applying the brakes. The reason being the N1 would be still running down through around 60% N1 when the reverser lights went out; thus giving momentarily significant forward thrust.

It wasn't until the English second language pilots were advised to carefully read (and understand) the FCTM instructions about the need to allow the N1 to reach idle reverse before cancelling, that the penny dropped they were doing it all wrong.

It got me thinking about landing with loss of all hydraulic braking capability - rare though that possibility could be, of course. The scenario in the simulator was concerned with the use of reverse thrust and the aircraft managing to stop still in full reverse right at the end of the safety area with a nasty drop at the end. How do you cancel reverse when stopped without the residual forward thrust inherent with cancellation from full reverse, trickling the aircraft over the cliff?

OK - I confess it is a bit far fetched but sometimes a bit of lateral thinking doesn't do you any harm; especially if there is nothing in the book about such a non-normal. And neither does there need to be.

Answer? At the moment the aircraft stops right at the end (your lucky day) cut both start levers while the engines are still at full reverse. With a bit of luck, there will be little or no forward thrust to roll you over the cliff with no brakes.

Writer quickly exits stage left..
Centaurus is offline  
Old 9th Jul 2019, 16:27
  #34 (permalink)  
Thread Starter
 
Join Date: Apr 2009
Location: Canada
Posts: 513
Originally Posted by Centaurus View Post
Answer? At the moment the aircraft stops right at the end (your lucky day) cut both start levers while the engines are still at full reverse. With a bit of luck, there will be little or no forward thrust to roll you over the cliff with no brakes.
Or just go to idle reverse and let the plane back up a before cancelling
Airmann is offline  
Old 10th Jul 2019, 07:55
  #35 (permalink)  
 
Join Date: Nov 2010
Location: Atlanta
Age: 52
Posts: 3
Originally Posted by Centaurus View Post
While training crews in Asia who were used to their company procedures (not necessarily Boeing FCTM procedures), it was noticed they tended to completely cancel reverse thrust at the 60 knots call during the landing run. At the call of 60 knots, they would slam the reverse thrust levers fully down from full reverse (Boeing 737). This would cause the aircraft to momentarily accelerate down the runway while the pilot was still also applying the brakes. The reason being the N1 would be still running down through around 60% N1 when the reverser lights went out; thus giving momentarily significant forward thrust.

It wasn't until the English second language pilots were advised to carefully read (and understand) the FCTM instructions about the need to allow the N1 to reach idle reverse before cancelling, that the penny dropped they were doing it all wrong.

It got me thinking about landing with loss of all hydraulic braking capability - rare though that possibility could be, of course. The scenario in the simulator was concerned with the use of reverse thrust and the aircraft managing to stop still in full reverse right at the end of the safety area with a nasty drop at the end. How do you cancel reverse when stopped without the residual forward thrust inherent with cancellation from full reverse, trickling the aircraft over the cliff?

OK - I confess it is a bit far fetched but sometimes a bit of lateral thinking doesn't do you any harm; especially if there is nothing in the book about such a non-normal. And neither does there need to be.

Answer? At the moment the aircraft stops right at the end (your lucky day) cut both start levers while the engines are still at full reverse. With a bit of luck, there will be little or no forward thrust to roll you over the cliff with no brakes.

Writer quickly exits stage left..
Had this happen in a light jet, Citation bravo. Has a seperate hydraulic system for the brakes and we lost all the fluid. I diverted to the longest runway, used the reverse to slow down to a complete stop. I had my hand on the emergency nitrogen powered emergency brake in case I needed it but wanted to avoid using it if I didn't have to because of the extra maintenance. So after I stopped I felt it started moving backwards, so I selected forward idle on one of the engines, stopped, shut both down, and we stood still long enough for the fire department to chock the nosewheel.
hans brinker is online now  
Old 10th Jul 2019, 16:03
  #36 (permalink)  
 
Join Date: Jun 2019
Location: VA
Posts: 208
Quite a while back, some airliners with tail mounted engines (DC-9/MD-80, 727’s, certain Fokkers) routinely used reverse to “power back” off a gate to save cost of having extra tugs. I think someone eventually figured out that the cost of fuel and wear on the engines was more than the cost of the tug.
Tomaski is offline  
Old 10th Jul 2019, 16:22
  #37 (permalink)  
 
Join Date: Apr 2003
Location: Europe
Posts: 2,973
If you do not stow the reversers upon reaching the taxiway you risk ingesting FOD and other stuff, as an A319 crew found out when they exited the runway in wintery conditions with the reversers still deployed. The low swung engines ingested de-icing chemicals, which caused smoke en fumes in the cabin, which led to an emergency evacuation initiated by the cabin crew (!).
Report: Easyjet A319 at Belfast on Jan 6th 2011, taxiway de-icing prompts evacuation


Anyway, Airbus FCTM says: stow reversers before leaving the runway to avoid ingesting FOD. Seems pretty sensible to me.
PENKO is offline  
Old 11th Jul 2019, 04:13
  #38 (permalink)  
 
Join Date: Jun 2000
Location: Australia
Posts: 3,871
We're to be fully out of reverse by 60 kts.
Is that the manufacturer's recommendation? Depends on aircraft type. For example B737 FCTM states: "Maintain reverse thrust as required, up to maximum, until the airspeed approaches 60 knots. At this point start reducing the reverse thrust so that the reverse thrust levers are moving down at a rate commensurate with the deceleration rate of the airplane. The thrust levers should be positioned to reverse ideal by taxi speed, then full down after the engines have decelerated to idle. Reverse thrust is reduced to idle between 60 knots and taxi speed to prevent engine exhaust re-ingestion and to reduce the risk of FOD. It also helps the pilot maintain directional control in event a reverser becomes inoperative. The PM should call out 60 knots to assist the PF in scheduling reverse thrust."

You can't get it more clearer than that.
Centaurus is offline  
Old 11th Jul 2019, 08:34
  #39 (permalink)  
 
Join Date: Nov 2018
Location: LUX
Posts: 73
Boeing 4-holer. Idle rev at 70 kts. Stow reversers before vacating the runway.
SaulGoodman is offline  
Old 13th Jul 2019, 19:22
  #40 (permalink)  
 
Join Date: May 2002
Location: somehere sandy!
Posts: 264
Someone needs to tell the man writing the Airbus manuals, that most airports won’t accept you being at taxi speed before leaving the runway. It defeats the whole purpose of high speed exits. And icy conditions aside, I believe the HS exits were well swept by the previous aircraft vacating!
goeasy is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.