National Air Cargo crashed in Bagram, Afghanistan

[Flanker2]

Load shifting is one possibility. This is being assumed as the cause as the pilots have maydayed that they were stalling due to a possible loadshift. The video does seem to confirm the theory of load shifting, but if you know what weight and balance does to a large aircraft, you may not be so sure that load shifting was the culprit.

If you have a 15.000kg vehicle making an aft shift of 5 meter, it would result in aft torque of 750.000 NM. It would explain the high pitch attitude in the beginning of the video. But in this condition, it's impossible to explain how the aircraft managed to yaw the fuselage back in to a horizontal position from a tail-down position, virtually without losing altitude in a complete stall situation let alone regain a nose-down pitch. I don't think that the pilots could have made the aircraft yaw like that with the rudder in a full stall and neither could aerodynamics of the wings.

With an aft center of gravity, your aircraft will no longer pitch down in a stall, it would stay pitch up until it hits the ground.

There are many more possible causes.
-wrong trim settings with aft CG
-elevator malfunction, trim malfunction

The load shift theory, would also point to a possible failure on the part of the loading crew and the loadmaster.

When loading heavy army vehicles that rests on the small area formed by 4 tyres on non-military cargo aircraft, a pallet is not always adequate to shed the load enough, as it doesn't have enough thickness. It sometimes requires to stand on a construction of multiple crossed wood beams sandwiched by pallets.
Military cargo aircraft can take heavy vehicle without any load-repartition as they have a much stronger cargo floor.
If the load shift occurs during the rotation, usually resulting in a tailstrike, the only thing you can do is to idle the engines and abort the take-off (even after V1). Trying to outclimb the aft shift is a 50/50 bet, it only depends on how bad the load shift is, how much spare thrust/weight ratio and maneuvering envelope you have left with your flight controls.

[AC.be]

There is a very simple explanation for the aircraft's high angle of attack at the beginning of the video. The surroundings of Bagram Airport are considered hostile territory, so the standard procedure is to take off with full power and climb as fast as possible, hence the high angle.

When you are near or at maximum angle of attack and you have a load shift towards the rear, you will go into a stall as soon as the center of gravity exceeds the allowed limit. It's actually a vicious circle. As soon as a piece of cargo starts moving towards the rear, the centre of gravity will increase, moving the angle of attack if not corrected. That increasing angle will make it harder for the rest of the locks and straps to keep the other cargo in place, not to mention carrying the load of the cargo that is already lose and pushing against the other cargo. Once it starts it just gets worse.

Nothing these pilots could have done, not even at greater altitude. They could theoretically recover from a stall at sufficient altitude, but you still have lose cargo in the hold, which would just put you in another stall again until you eventually impact terrain. Not even the best pilot could have saved this.

Tragic accident that shows the importance of the work of people on the ground towards air safety.

[Bralo20]

When loading heavy army vehicles that rests on the small area formed by 4 tyres on non-military cargo aircraft, a pallet is not always adequate to shed the load enough, as it doesn't have enough thickness. It sometimes requires to stand on a construction of multiple crossed wood beams sandwiched by pallets.
Military cargo aircraft can take heavy vehicle without any load-repartition as they have a much stronger cargo floor.

We probably need to wait until the report is out but there is a picture of MRAPS M-ATV Oshkosh vehicles (like the ones loaded on N949CA) loaded into a Boeing 747. It may be even from National Air Cargo but it could be also be from another company, couldn't find the original picture in a quick search.



You'll notice that the vehicles are loaded onto a pallet but that they are also supported by wood beams to level the weight and to disable the suspension of the vehicle, further it's clear that multiple straps are used to secure the vehicle to the pallet and to the cargofloor.

[Bracebrace]

The high angle of attack is not the same as high angle of climb. The angle of attack for a max rate of climb and max angle of climb are pretty close to eachother (they are not the same but close enough to be fairly unidentifiable by the human eye in a video like this). There is a difference in speed although yet again, hardly noticeable by the human eye looking at a aircraft from the outside.

The difference in pitch here (if he's not already in the stall at the beginning of the video) could be caused by the use of full power one would use in this hostile environment (depending on what the pilots/company prefer). The full rated thrust is only needed for the couple of tons below the max in the given conditions (I guess from 30-40 tons below but that is a "motivated" guess) so it is hardly ever used. If they did use full thrust with the lower weights, this leads to much higher pitch angles than you would see on a normal takeoff. Normal takeoff require pitch from 15 to 18°, if you use all thrust you easily have to pitch up beyond 20° to prevent the speed from blasting away after rotation. You end up flying a rocket, but in Afghanistan, you might prefer to be in a rocket...

On the subject of Brussels: in the sixties there was a Sabena 707 on approach to Brussels which probably had a stab trim runaway. The result is pretty much the same. The Sabena pilots managed to pull the 707 in a continuous turn instead of blasting up in the sky and stalling out of it. But they still couldn't solve it and eventually stalled in the turn. Everybody died.

[BrightCedars]

Can somebody shed light on how you get this cargo loaded in a BCF? It's not like the nose will open like on standard B747F's. Are the cargo doors large enough? Do you need to rotate the vehicles inside the hull?

What a horrific accident. RIP

[andorra-airport]

The 5 M-ATV's were not loaded in Bagram, but at a previous stop at Camp Bastion.

[9vsmu]

Can somebody shed light on how you get this cargo loaded in a BCF? It's not like the nose will open like on standard B747F's. Are the cargo doors large enough? Do you need to rotate the vehicles inside the hull?

What a horrific accident. RIP

A 747F has a system to turn/load 20ft pllts. Most pdu (power drive units) turn in one direction (fwd/aft only) but on some positions (nse/side cgo door) some pdu's can be retracted or be turned in a different angle.

The max length you can load thru the side cgo door is the length of a 20ft pllt plus a overhang of about max 50-70cm, assuming the pllt is build on max contour.

[flightlover]

Can somebody shed light on how you get this cargo loaded in a BCF? It's not like the nose will open like on standard B747F's. Are the cargo doors large enough? Do you need to rotate the vehicles inside the hull?

What a horrific accident. RIP

If you look at the picture of the vehicle inside the plane you might notice some bits of the car sticking out above the black net hanging just after the flight deck bulkhead. If anything catches the net, this means damage will occur to the flight deck if you would try to load it further to the front.
In this case nose load wasn't even an option

[RTM]

Just a thought... But what is going to stop 15 tons of steel once it gets moving? Especially at that steap a pitch angle... I think it even could take out the aft pressure bulkhead and exit the aircraft taking of the tail. Which it obvously didn't. But would the pilot be able to regain a nose down attitude after the stall...? I don't know... Looking at the initial yaw to the left, wouldn't an engine failure be more likely?

[FlightMate]

Given the high Angle of Attack during the stall, it is possible that one engine stalled as well, inducing the yaw.
Could well be as well that one wing stalled before the other, specially if the aircraft was in a turn.

[Flanker2]

I'm just posting to highlight the great thread that this one has been. Civilised conversation, great inputs from everyone, great sharing of information.
It's much better than the rubbish that you read on the equivalent discussion on airliners.net, where everyone wants to be right and they all end up sounding like a bunch of politicians.

Is this the sign of a new dynamic on luchtzak.be? It certainly looks like it and I think that we should embrace it.