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Thrust Reverse  
User currently offlineVictor Hotel From Australia, joined Aug 2000, 305 posts, RR: 1
Posted (13 years 5 months 3 days 10 hours ago) and read 1247 times:

For thrust reverse on turbofan engines, do they bleed pressure from some of the compression stages and direct them forward. Can someone explain how they work properly for me, keeping it simple? Thanks.
VH

7 replies: All unread, jump to last
 
User currently offline242 From United States of America, joined Oct 2000, 498 posts, RR: 1
Reply 1, posted (13 years 5 months 3 days 9 hours ago) and read 1193 times:

It just depends on what type of reverser the engine has.

A clam-shell, or bucket style reverser, like on DC-9s and 737-200 JT8-D engiines, both the hot stream (core exaust) and cool stream (fan exaust) are deflected forward.

On larger engines, like the GE CF-6 and P&W 4060, the cascade type reverser slides backward, pulling panels closed via linkage in the cool stream duct and exposing the cascade screen to deflect only the fan exaust forward. The hot stream is not affected.




User currently offlineJt8djet From United States of America, joined Jul 2000, 214 posts, RR: 0
Reply 2, posted (13 years 5 months 3 days 9 hours ago) and read 1185 times:

Forward thrust

Click for large version
Click here for full size photo!

Photo © Colin K. Work




Thrust reverser deployed exposing the cascade vanes.

Click for large version
Click here for full size photo!

Photo © AirNikon






User currently offlineVictor Hotel From Australia, joined Aug 2000, 305 posts, RR: 1
Reply 3, posted (13 years 5 months 2 days 12 hours ago) and read 1160 times:

thanks people.
VH


User currently offlineTOP From Germany, joined May 2000, 264 posts, RR: 0
Reply 4, posted (13 years 4 months 3 weeks 5 days 21 hours ago) and read 1135 times:

I think I've a photo of a dismantled reverser unit...
Are you interested in it?



User currently offlineNicolaki From , joined Dec 1969, posts, RR:
Reply 5, posted (13 years 4 months 3 weeks 5 days 20 hours ago) and read 1129 times:

TOP: I don't know if Victor Hotel is, but I am very interested in that picture.

User currently offlineTOP From Germany, joined May 2000, 264 posts, RR: 0
Reply 6, posted (13 years 4 months 3 weeks 5 days 17 hours ago) and read 1122 times:

I'll send them to you next time!

stephan.tophoven@t-online.de


User currently offlineAF_Guy From , joined Dec 1969, posts, RR:
Reply 7, posted (13 years 4 months 3 weeks 5 days 14 hours ago) and read 1118 times:

Something to remember is that the thrust is NOT directed exactly forward (i.e. 180 degrees from the reverse axis). Once the aircraft touches down, electrical switches on the landing gear enable the thrust reverse control system to engage. The pilot brings the engines to forward idle, and pulls up on a set of smaller levers forward of the actual throttles. This causes the "buckets" or "sleeve" (see below), to swing back into the engine's thrust stream. Once the pilot sees that all engine thrust reversers are engaged, through a set of indicator lights, he advances the normal engine throttles to bring the engine power up and the reverse thrust force higher.

On the T-Tail aircraft, thrust reversers are large "buckets" of metal that mechanically swing back and "clamshell" into the exhaust stream of the engine, deflecting the thrust maybe 10-20 degrees max forward. These "buckets" are actuated either pneumatically (using air bled from the engines) or hydraulically (using a self-contained hydraulic system).

On underwing engines, the principal is the same but you really can't see the reversers working. Usually a sliding sleeve on the engine slides aft, which closes off the buckets inside the tailcone, deflecting the exhaust to the sides and forward, but nowhere near directly forward, more like 10-20 degrees....

Some of the myths of thrust reversers are:
(1) the engine stops, and spins in reverse, directing thrust forward (NO! not even close)
(2) the compressor blades in the engine are pivoted to direct the thrust forward (NO! although some engines do have variable stator vanes, these are used to schedule the airflow through the engine)

Hope this helps!


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