B747 C Speed Brake Extension and SYSTEM 4 Hyd
Thread Starter
Joined: Dec 1999
Posts: 86
Likes: 0
From: In from the fringe
B747 C Speed Brake Extension and SYSTEM 4 Hyd
With hydraulic system 4 inoperative, the caution in the procedure states that rapid extention of speedbrakes causes nose pitch up. Sure enough in the sim you can get airborne again.....why does the nose pitch up rather violently even when spoilers 5 6 and 7 8 will not operate.?? I can't picture in my opaque mind the shifting of the centre of lift or is it drag related...?
Can someone clear this point up for me ...??
Many thanks in advance
jones
Can someone clear this point up for me ...??
Many thanks in advance
jones
Joined: Jun 2001
Posts: 518
Likes: 0
From: Chicago, IL, USA
I'm just going to take a clumsy stab at this one--no energy to do the research for a really good explanation.
I believe it's more a question of the center of lift. Since spoilers 5, 6, 7 and 8 are the most inboard, they're also the most forward.
As the remaining spoilers deploy, lift is destroyed aftward, but not more forward.
Wish I could post some brilliant diagrams, but that's the best I can do right now.
Did it help? I hope so.
I'm sure you'll get better responses soon.
I believe it's more a question of the center of lift. Since spoilers 5, 6, 7 and 8 are the most inboard, they're also the most forward.
As the remaining spoilers deploy, lift is destroyed aftward, but not more forward.
Wish I could post some brilliant diagrams, but that's the best I can do right now.
Did it help? I hope so.
I'm sure you'll get better responses soon.
Joined: Jun 2001
Posts: 518
Likes: 0
From: Chicago, IL, USA
Originally Posted by Intruder
That's pretty much the answer. The total center of lift moves aft, causing the pitch-up.
