c5load
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Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 12:08 am

I have seen it many times on the C-17 that it parks with the thrust reversers in the deployed position. Do civilian airliners do this at any point? Is it possibly an engine cooldown measure?


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tdscanuck
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 12:20 am

Quoting c5load (Thread starter):
Do civilian airliners do this at any point?

Not by normal procedures...they might do it for maintenance or in the event of a failure.

Quoting c5load (Thread starter):
Is it possibly an engine cooldown measure?

Not on a modern civilian airliner...it might work on a C-17 since they've got core reversers.

Tom.
 
Fly2HMO
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 12:36 am

Quoting tdscanuck (Reply 1):
it might work on a C-17 since they've got core reversers.

Wouldn't an engine cool down better if it was just allowed to windmill freely?

Leaving the reverser deployed arrests windmilling from what I've noticed.
 
packcheer
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 4:14 am

Well maybe you've hit the nail on the head. Maybe the C-17 leaving the reversers open won't harm anything, but will prevent the engine from windmilling, so they use that instead of having to put something in the fan blades (I've seen some airlines use a long 2 x 4 when the aircraft is at the gate).
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Fly2HMO
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 6:17 am

Quoting packcheer (Reply 3):
(I've seen some airlines use a long 2 x 4 when the aircraft is at the gate).

Now that's crude. The one I see often at airshows is bungee cords or even seatbelt extenders tied across a fan blade and a stator  I'm assuming the only real benefit to that is so stupid people don't stick their hands in there and get mauled.
 
tdscanuck
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 3:28 pm

Quoting Fly2HMO (Reply 2):

Wouldn't an engine cool down better if it was just allowed to windmill freely?

Windmilling doesn't do that much for the core...the N1 spool is spinning but most of the guts aren't. The core is heavily insulated, so airflow is limited. In a commercial reverser, windmilling is all you get so it's probably better than nothing.

Opening a core revereser, like a C-17, would actually give you an airflow path to the core, which might give you convective cooling and/or make the windmilling more effective.

This is wild speculation on my part...I have no idea what the real reason is.

Quoting Fly2HMO (Reply 4):
The one I see often at airshows is bungee cords or even seatbelt extenders tied across a fan blade and a stator

You should have seen the A400M guys securing their props at Farnborough this year...it was like Cirque Du Soleil came to town and they were starting to put the tent up.

Tom.
 
DashTrash
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 7:48 pm

Quoting Fly2HMO (Reply 4):
I'm assuming the only real benefit to that is so stupid people don't stick their hands in there and get mauled.

When an engine is windmilling it it turning with zero oil pressure. Preventing the windmilling reduces engine wear since there is no lubrication going on.
 
MD11Engineer
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 8:59 pm

On older IL-76 aircraft (and possibly other Russian aircraft) it was standard practice to deploy the bucket type reversers when the aircraft was parked to prevent windmilling.

Jan
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Fly2HMO
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 9:07 pm

Quoting DashTrash (Reply 6):

When an engine is windmilling it it turning with zero oil pressure. Preventing the windmilling reduces engine wear since there is no lubrication going on.

I figured that too but I remember asking that question eons ago here and everybody said the wear is negligible.
 
evil8er2006
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RE: Parking With Thrust Reversers Deployed?

Thu Sep 09, 2010 9:45 pm

Quoting packcheer (Reply 3):
Maybe the C-17 leaving the reversers open won't harm anything, but will prevent the engine from windmilling, so they use that instead of having to put something in the fan blades...

Pretty much correct. Also, if you have a tailwind above a certain wind speed, the flight manual recommends placing the TRs in reverse to help with starting the engine.
 
Spacepope
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RE: Parking With Thrust Reversers Deployed?

Fri Sep 10, 2010 12:36 am

I remember TWA used to park their -9s with the buckets closed at STL, like this:

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And of course the IL-76 was also mentioned already:

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