Originally posted by Deadstick
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National Air Cargo B744 at Bagram on Apr 29th 2013, lost height shortly after takeoff
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Allesandro has a nice link there. http://avherald.com/h?article=46183bb4
No cargo added or removed during a stop for fuel. Kind of rules out a load shift.
Also if the load had broken to the back I highly doubt they would have been able to get that plane back to the nose down finish, nevermind ANY control.
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Originally posted by TheKiecker View PostAllesandro has a nice link there. http://avherald.com/h?article=46183bb4
No cargo added or removed during a stop for fuel. Kind of rules out a load shift.
Also if the load had broken to the back I highly doubt they would have been able to get that plane back to the nose down finish, nevermind ANY control.
About the plane being able to "lower the nose", I see no problem.
With a too aft CG the plane will still have a trim AoA, the problem is if even with full elevator down that trim AoA is beyond stall AoA. If this happens, the plane will unavoidably stall.
Now, that it stalls doesn't meant that it'll keep its nose high. To begin with, the center of pressure moves from about 24% of the chord in a fully unstalled wing to about 50% of the chord in a fully stalled wing (flow completely detached on all the wing). That by itself provides a nose-down pitching moment. Also, as the wing's AoA increases, the tail's AoA also increases providing additional pitching down moment. So the plane will eventually to that trim (a.k.a. equilibrium) AoA even if it's beyond stall.
Now say that that trim AoA is 30 degrees, which will be well beyond stall. The plane at the top of the climb can be briefly fly horizontally with the nose 30° high (that's 30° of AoA), then fall with a descent slope of 40° and the nose 10° low, which again is still 30° of AoA.
Lowering the nose is not the same than reducing the AoA, you need the nose to go more down than what the trajectory goes down. And I don't think that this ever happened in this accident.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by TheKiecker View PostAllesandro has a nice link there. http://avherald.com/h?article=46183bb4
No cargo added or removed during a stop for fuel. Kind of rules out a load shift.
Also if the load had broken to the back I highly doubt they would have been able to get that plane back to the nose down finish, nevermind ANY control.
i also agree with the recent comment, that with a much steeper climb out, the cargo retention system/connection points etc. may have finally reached a stress leve (that was not reached on earlier leg of trip) where something snapped or gave way causing the shift aft;
once the nose came towards level (during the 90deg roll to right), the cargo may then have shifted/rolled forward allowing CG to shift forward again (as someone points out in a post above as well).
If cargo did give way, and it shifted back, then to the left, then far to the right (as the jet rolled/pitched, etc.) and then forward, it is possible that it was a real sh-tstorm inside the cargo hold with stuff moving/shifting hither tither and yon.
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Originally posted by bob m View PostIf the load shifted aft, why is the aircraft hitting the ground in a nose down attitude?
The nose did go way up.
The wing stalled and lost lots of lift.
The plane turned sideways allowing the tail to help swing the nose downward- since the CG was still well ahead of the tail.
Go buy yourself a balsa wood glider and put a binder clip near the rear of it...you will find lots of flight modes where it flutters around with wild attitude fluctuations...espeically right after you release it.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by snydersnapshots View Post..............................
2) The FAA (and, I assume, the foreign equivalents) would probably NEVER sign off on an installation where only a portion of the occupants have the opportunity to get out of the airplane....................
......................point out that military cargo planes such as the C-5, C-17, C-130, KC-10, and KC-135 do not have ejection seats and they would (rightly) point out that the missions and environments that those aircraft operate in are by nature far more hazardous than the environments that civilian cargo aircraft operate in.
The KC-135 had manual bailout capability provided there was sufficient altitude and aircraft stability. A pilot I knew said the worst case scenario was being attacked by enemy aircraft.
I'm not sure if other tankers had bailout capability.
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Originally posted by Gabriel View PostAnd that it didn't break in the previous flight doesn't mean that it won't break in the next one.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by phoneman View PostJust curious about the position of cargo after crash, and positions of control surfaces.
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