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Thrust Reverser On Landing (with Pic)  
User currently offlineLHSebi From Germany, joined Jan 2004, 1049 posts, RR: 8
Posted (10 years 9 months 2 days 10 hours ago) and read 4114 times:


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If the pilots activate the reversers so early, even before the nose wheel has actually hit the ground, won't it come down pretty hard? (the nose wheel)

Sebastian


I guess that's what happens in the end, you start thinking about the beginning.
8 replies: All unread, jump to last
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (10 years 9 months 2 days 10 hours ago) and read 4042 times:

No.....the Thrust Reversers are controlled off the Main Wheel Squat switches, so they will not activate until the mains are firmly on the ground. As for the nose wheel, you get enough lift off the elevators to softly control the nose wheel dropping.


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineContact_tower From Norway, joined Sep 2001, 536 posts, RR: 1
Reply 2, posted (10 years 9 months 2 days 10 hours ago) and read 4032 times:

Kinda depends on how much "umf" they put out before the nose hits mother earth, in idle the effect ain't that great, and it takes a while to spool up the engines again.
It's not a uncommon sight, were I work we get a lot of dodgy braiking action during the winter months, and during such conditions the pilots of medium to large jets are "hot" on the reverse.  Big thumbs up


User currently offlineBio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 3, posted (10 years 9 months 1 day 17 hours ago) and read 3844 times:

No.....the Thrust Reversers are controlled off the Main Wheel Squat switches, so they will not activate until the mains are firmly on the ground.


EMBQA sorry but that is an incorrect statement for some aircraft. The Tu-154 can activate the thrust reversers while in flight. A more popular aircraft, the DC-8 can also do so. The two inner reversers can be used while descending to help slow down the aircraft since it has no in flight spoilers.


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-Alfredo


User currently offlineWing From Turkey, joined Oct 2000, 1573 posts, RR: 24
Reply 4, posted (10 years 9 months 1 day 17 hours ago) and read 3834 times:

The nose actually flies until there is sufficent amount of lift generated over the elevator surfaces.In wing mounted engines you can deploy TR's,it will delay until 2-3 seconds and during this time you already put the nose down while in tail mounted engines its recomended to put the nose down first before using the TR to prevent reverser buckets contact the ground.Still either wing or tail mounted its better to put the nose down as soon as possible.


Widen your world
User currently offlineJetmek319 From Germany, joined Sep 2003, 199 posts, RR: 1
Reply 5, posted (10 years 9 months 1 day 16 hours ago) and read 3817 times:

If I'm not full of hot air, I believe that some of the Airbus family uses the radio altimeter to inhibit/allow TR use close to the ground. ??


Never, ever moon a werewolf !!
User currently offlineBio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 6, posted (10 years 9 months 10 hours ago) and read 3587 times:

I had the same idea as you Jetmek. I vaguely recall seeing a picture in the database of an airbus with the reversers deployed before toughdown, but couldn't find it.

-Alfredo


User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 34
Reply 7, posted (10 years 9 months 5 hours ago) and read 3478 times:

>>>If I'm not full of hot air, I believe that some of the Airbus family uses the radio altimeter to inhibit/allow TR use close to the ground. ??<<<

No your not full of hot air. Most modern airliners utilize the radio altimeter system as a redundancy to wheel spin-up to deploy the thrust reversers.

Here's why. Most later model aircraft utilize main wheel spin-up as a primary "on ground" signal allowing the thrust reverser to be deployed. But certain scenarios could potentially nullify this from happening. For instance, severe hydroplaning can prevent the wheels from spinning up potentially preventing the t/r's from deploying.

The reverse thrust system use's the radio altimeter as an alternate method of determining "ground" mode to deal with the contingency of ice or water on the runway preventing wheel spin-up.

The radio altimeter "trip" height is very low, 7 feet on the MD11 for instance. This height roughly commensurates with actual radio height with the main gear struts extended touching the ground.

The radio altimeter is also used by the auto-spoiler system for the same reason.



You're only as good as your last departure.
User currently offlineNightFlyer From United States of America, joined Sep 2001, 95 posts, RR: 3
Reply 8, posted (10 years 9 months 5 hours ago) and read 3542 times:

Another tid-bit on the MD11. The #1 and #3 engines are available for reverse thrust after the mains spin up and the reversers are fully deployed. The #2 reverser will deploy but will not spool up until the nose wheel is on the ground.

NightFlyer


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