National Air Cargo 747-400 Crash

[John H Watson]

From what I'm reading on the PPRuNe forum on this incident, the most intelligent sounding posts are suggesting that, in situations where the pitch upwards is beyond control, the aircraft should be rolled to bring the nose down. At some airlines, this is trained for in the sim.

Increasing thrust increases the pitch up movement, but I'm told that this is not as pronounced as it is on some aircraft with engines below the wing.

That is not to say that this technique would be of much benefit at such a low altitude.

[Aidan]

Hi John,

Certainly in extreme unusual attitudes that's what we are instructed to do (although it is not usually practiced in the sim) but certainly not a garden variety stall and again when you're as close to the ground as these guys were all bets are off, do what you can to 'land' the aircraft so everyone can be extricated with a heartbeat.

I don't know whether they had actively input the roll to the right that eventually occurred, it certainly got the nose going down but as the writer indicated the C of G was still to far rearward to effect any flyable condition.

I was always impressed with the PS1.3 flight characteristics that Hardy had programmed in to the 747, when I used to muck around with it years back, I always found that particularly at high altitudes, the PS744 was a bitch to get flying again once stalled. When I had a go in a full motion sim some years back now (not my usual steed) I found it very representative of the same stall characteristics I had seen on the PS744. Well done Hardy!

[Hardy Heinlin]

Thanks :-)

For the engineers: Assuming some military equipment rolled down into the aft section, could this destroy the stabilizer control system and cause an uncommanded, unstoppable stab motion? (Uncommanded stab motion can be simulated in the sims for training.)


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[John H Watson]

Too many variables.

The vehicle would probably have had to pierce/deform the aft pressure bulkhead or fly up into the ceiling area to do any damage.

How fast was the vehicle rolling before it hit something? Was there restraining webbing fitted in front of the aft pressure bulkhead. What was the shape of the vehicle? Was the handbrake on? Were the tyres deflated (as routine)? Did the tie down straps and other restraints slow it down any?

How strong is the bulkhead? The bulkhead is designed to withstand differential pressures of greater than 9psi (so, many. many tonnes of force over it's entirety). Also, there is a respectable distance between the bulkhead and the jackscrew (a metre or two from memory)

If the vehicle was going fast and altered the shape of the bulkhead, it could have damaged/jammed some of the elevator control cables or punctured some of the many hydraulic lines (which run through and/or are in close proximity to the bulkhead). However, there are two sets of elevator control cable pairs (effectively 4 wires). Jamming/breaking one pair may still leave the other operative.  And regarding trim, if no trim commands are made or no hydraulics available, the stabiliser jack screw mechanism is mechanically braked.

Unfortunately, after such a fireball, I doubt there would be much left for the investigators to salvage for their investigation  :?

[Jeroen D]

Were the tyres deflated (as routine)?

Never realized they deflate the tyres? On telly you always see them driving up and down aircraft ramps as if it was a ferry boat!  So in between they let the air out and fill it up again?

Jeroen

[John H Watson]

The tyres are partially deflated to sit the vehicle on wooden blocks/planks which support the chassis (this should stop the vehicle bouncing around on its own suspension)

I can see vehicles being driven onto cargo aircraft fitted with built-in ramps where the main cargo deck is only a metre or two above the tarmac (Hercules, C5A, etc), but normally, on a 747F, which has a main deck perhaps 5 metres above the tarmac, vehicles are loaded onto flat trays and then lifted vertically up to the main deck, where the 747's inbuilt loading system moves the vehicle into the right position (the floor has motorised rubber drive wheels, some of which can be positioned at various angles).
The trays are then locked down with latches in the floor and the vehicle is tied down with dozens of straps.

Rgds
JHW.

[Jeroen D]

Thanks
Jeroen

[George Kent]

Lots of information about this incident here:

http://avherald.com/h?article=46183bb4&opt=0

Some very disturbing speculation seems to be emerging that the aircraft may have landed at Bagram to refuel due to the lower cost of fuel compared with Camp Bastion.

[John Golin]

Some very disturbing speculation seems to be emerging that the aircraft may have landed at Bagram to refuel due to the lower cost of fuel compared with Camp Bastion.

That doesn't sound disturbing to me, it sounds smart?  

[Phil Bunch]

Some very disturbing speculation seems to be emerging that the aircraft may have landed at Bagram to refuel due to the lower cost of fuel compared with Camp Bastion.

That doesn't sound disturbing to me, it sounds smart?  

I thought it was routine (especially for freighters) to use computers, etc, to plan the lowest cost route for flights.  Refueling stops would be a critical part of flight planning.  For passenger flights, this type of planning is also routine, and for very long flights one's actual route depends on the specific weather, weight, etc, etc.  The other financial and non-financial costs and nuisance considerations for refuelling stops are always considered too, as best I can follow how airlines work.

Is Bagram considered a normal, civilian-suitable airport these days?

Perfect safety is hard to achieve - I've flown into Heathrow and found police with submachine guns patrolling the airport, and I've had my airliner on which I was a passenger guarded by an assigned soldier with a shotgun - he was stationed just off the nose wheel while passengers boarded in Bangkok.  Each airliner had such a guard.

[Jeroen Hoppenbrouwers]

The London patrols are clear, but I fear the Bangkok guard was "just" to prevent people climbing into the wheel wells as stowaways.

[Balt]

Hi all,

avherald updated after the Afghan transport ministry released the (preliminary?) report.
It went as suspected: 80 ton load shift during takeoff roll, apparently with sufficient impact that the aircraft was shedding parts on the runway still, severed control cables and linkages.

Here's the link:

http://avherald.com/h?article=46183bb4&opt=0