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Idle Reverse while vacating
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?
While vacating on high speed exits I usually keep reverses at idle until I'm down to a taxi speed that I'm happy with, I don't find any point in selecting forward idle while still decelerating. This means having reverse idle while on an exit. |
I'm sure they're risks. There's risk associated with walking down the stairs. I do it when necessary, with your logic. Why stow them when you're still decelerating?
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Vacating the runway, while in reverse is one of the highest risk areas for blowing around debris to be ingested by engines. When I used to fly the four holers I could count on a shower of visible fan sparks in the inlet if the pilot left the outboard reversers on when turning off the runway
When I conducted airport debris investigations, I would always note the highest risk areas were at the turning points between runways and taxiways. And a few stories about high power spoolups on the chevrons where only the few dare to go |
Forward idle adds considerable thrust so keeping at reverse idle is a good idea when clearing at high speed.
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A320 FCOM (CFM) says:
"AT TAXI SPEED REVERSERS.........STOW When the aircraft reaches the taxi speed, and before it leaves the runway, stow the reversers.' |
See lomapaseo's note above - it's not just 4-eng aircraft or wide bodies that risk ingestion from FOD; all aircraft are at a greater risk of FOD ingestion when on taxiways than on runways for the simple fact that they are not usually as well-maintained/inspected in many parts of the world. Engine intakes on a low-mounteed a/c are much closer to the grass/dirt on a taxiway than on a 45m-wide runway. I take your point that there's little point adding fwd thrust if still braking, but by the time you vacate the runway you should be going slow enough that adding a little fwd thrust is not a threat.
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Depends on the aircraft. What guidance does the manufacturer provide? |
IIRC Airbus recommends to stow the reversers before leaving the runway due to FOD. I’m too lazy to look it up for you, but it’s clearly written somewhere in the FCTM. |
Yes. Airbus say to stow reversers when reaching 70 kts to avoid FOD ingestion. With some stopping issues following failures, they say you can use reversers all the way down to 0, (obviously increased FOD risk, but deemed acceptable in such circumstances). |
Do you have a reference for that? |
In my OM we have as a reference to stow at taxi speed, there’s a limitation regarding snow on the runway. A part from that I normally see also many Training Captain keeping rev idle while vacating on a RET and only at a low speed (usually around 10kts before the turn after the RET) stowing reverse. It’s really rare on a RET have reverse stowed before leaving the rwy |
Yes. Airbus say to stow reversers when reaching 70 kts to avoid FOD ingestion |
What's more troubling is the person who goes from max reverse to forward idle at once. Absolutely no need for that.
Thanks for the FCOM reference that says to store them before vacating, and at taxi speed. Unfortunately the reality is that if we slowed to taxi speed before leaving the runway every time, ATC would quickly get annoyed. |
Most major airports have high speed exits at a 45' angle which you can take at 60 kts depending on aircraft type. A 90' turn would require slowing down to around 10 kts. Some airports monitor runway occupancy time and may follow up if you are way in excess of the expected time without good reason.
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I don’t know if we are allowed to copy and paste from manufacturer’s manuals, so Moderators please edit if necessary: From Airbus FCTM (A320) SOPs/ Landing/ Deceleration: REVERSE THRUST EFFICIENCY Thrust reversers are more efficient at high speeds: The flight crew must select reverse thrust immediately after main landing gear touchdown. Below 70 kt, thrust reversers efficiency rapidly decreases. Below 60 kt with REV MAXselected, engine stall may occur. Therefore, it is recommended to reduce the reverse thrust to REV IDLE at 70 kt, and keep REV IDLE until taxi speed. However in an emergency case, the flight crew must keep REV MAX until full-stop of the aircraft. At taxi speed, and not above, stow the thrust reversers before leaving the runway, in order to avoid foreign object ingestion. |
Uplinker - Folk here are in agreement with the FCTM. Your post 9 isn't. REV IDLE is not stowed.
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Yes, I was sloppy with my terminology. Apologies. :ok: . |
Here’s the FCOM reference AT TAXI SPEED REVERSERS................................................... ............................................................ .............STOW L2 ‐ When the aircraft reaches the taxi speed, and before it leaves the runway, stow the reversers. PRO-NOR-SOP-19 P 3/8 |
Originally Posted by Max Angle
(Post 10507247)
Idle reverse by 70kts, not stowed at 70.
I was under the impression it’s reduce from max to idle at 70kts and cancel reverse at taxi speed. An Interesting question is this, which speed reference are you using, GS off the ND or IAS off the PFD . |
IAS is what we use (large airbus operator). |
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