PPRuNe Forums - View Single Post - Tail plane in ground effect during rotation.
Old 7th July 2005 | 05:06
  #23 (permalink)  
LGB
 
Joined: Feb 2002
Posts: 178
Likes: 1
From: -
Rainboe,

Being rather new on the 74, I tend to agree, though I thought it was lower than 400. If turbulence and wind change is not a factor, I seem to go high on either or both of speed and glide slope unless I do a slight power reduction. When considering the span of the 747, it does make sense that it occurs at a few hundred feet.

Regarding what initial attitude to rotate to, going beyond 12 degrees in a swift rotation would give a tail strike (except for the SP), but as long as the rate of rotation is the recommended 2 to 3 degrees pr second, by the time the pitch goes through 12 degrees, lift of should have occured anyway.

Which leads to another relevant question of how the climbout performance may be affected by a slower rotation, as opposed to a faster one. Some will say to stop rotation at 10 degrees until positive rate, so would this technique alter the climb gradient? Waiting for positive rate at 10 degrees will often give a speed higher than V2+10. When airborne, however, that speed could be traded for climb, and thus one should be back on the same climb profile, more or less. Or what? I am not talking about gross underrotation, just rotate 10 degrees, then lift to whatever pitch brings the speed back to V2+10 to 20. If neither obstacles nor runway length is an issue, I'd rather be sure to avoid a tail strike.

How many degrees is this?

http://www.!!!!!!!!!!!!!!/open.file/869836/M/

Tail strike:

http://www.!!!!!!!!!!!!!!/open.file/336680/M/

Vmu testing

http://www.!!!!!!!!!!!!!!/open.file/219906/M/

Other close examples

http://www.!!!!!!!!!!!!!!/open.file/539269/M/
http://www.!!!!!!!!!!!!!!/open.file/562519/M/
http://www.!!!!!!!!!!!!!!/open.file/292539/M/



Tail strike on landing, when going below Vref is another similar issue

http://www.!!!!!!!!!!!!!!/open.file/815565/M/

Last edited by LGB; 7th July 2005 at 05:22.
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