Cargo Crash at Bagram
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I had thought that perhaps a specially reinforced floor might have been installed in a cargo 747, but I can see how you explanation is lighter and still fit for purpose.
KenV, this isn't my area of expertise (I'm an engine guy). But my understanding is for Boeing built 747 Freighters and Boeing Converted Freighters (BCF, which is what the Bagram freighter was), they don't use seat tracks. The floor structure is someone unique to the freighter (and yes it is strengthened relative to the passenger main deck floor). The 747F main deck has a fairly elaborate cargo handling system which incorporates stops and hold-downs for the standard air-cargo pallets. Unfortunately those are not suitable for hauling large military vehicles, so alternate means are required.
Freighter conversions done by others often repurpose the seat tracks for cargo restraint, but not those done by Boeing.
However the rest of what you posted appears spot on.
Freighter conversions done by others often repurpose the seat tracks for cargo restraint, but not those done by Boeing.
However the rest of what you posted appears spot on.
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Seat track on a 747 is only good for 5000lbs…You can attach a 25000 lbs chain to a D ring in a seat track but its only going to give you 5K. If you strap stuff down correctly. You will not have a problem..Use locks when you can and every one lives….
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"You call, we haul"
The "Interviews' Document" is particularly telling - there is a huge amount of detail on the practices and the loading of the accident flight - number of chains/straps/palettes etc.
Seems to me that the "You call, we haul" philosophy of the company may well have had something to do with this accident and the flight load master was put in a difficult and unprecedented position: the 3X18 ton MRAP Cougars were behemoths and together with the lighter 12 ton MRAPS, an unfamiliar/exceptional payload, which had to be loaded & attached in improvised fashion with no particular guidance.
The double pallet system, used on this occasion and many others, by the company was too large to be attached to the floor and was therefore 'floating' with only strapping to the aircraft. A National Air Cargo loader (who previously worked for DHL) and who helped load the flight said:
All 5 MRAPs were loaded in a central line, with at least one lighter 12 ton MRAP in front of the 3 Cougars. (Note, there is a discrepancy in one of the interviews, with the same loader implying both lighter MRAPs were at the front and then later saying one was fore and one aft. The aft MRAP was:
. The loaders also mention a final smaller pallet in the T2 position with only a light scaffolding load, but which was actually secured to the floor by 'bear claws'.
The Principal Operations Inspector (POI) for National Airlines said he was aware the
The company seem to have acknowledged all this with a current moratorium on 'floating' pallets (i.e. unsecured to the floor) until the manual is updated, a specialist team to advise on exceptionally heavy loads, plus support for load masters who wish to refuse a load.
One person saw fluid leaking from the tail of the aircraft. Sweepers found some debris near the runway characterised as “metal” but it doesn't seem certain they were 100% certain it was from the accident flight.
Seems to me that the "You call, we haul" philosophy of the company may well have had something to do with this accident and the flight load master was put in a difficult and unprecedented position: the 3X18 ton MRAP Cougars were behemoths and together with the lighter 12 ton MRAPS, an unfamiliar/exceptional payload, which had to be loaded & attached in improvised fashion with no particular guidance.
The double pallet system, used on this occasion and many others, by the company was too large to be attached to the floor and was therefore 'floating' with only strapping to the aircraft. A National Air Cargo loader (who previously worked for DHL) and who helped load the flight said:
The Cougars were 18 tons, and this was the first time they had ever loaded something that large. There were no floor locks used on the MRAPs since the pallets were center loaded.
All 5 MRAPs were loaded in a central line, with at least one lighter 12 ton MRAP in front of the 3 Cougars. (Note, there is a discrepancy in one of the interviews, with the same loader implying both lighter MRAPs were at the front and then later saying one was fore and one aft. The aft MRAP was:
just beyond the aft cargo door
The Principal Operations Inspector (POI) for National Airlines said he was aware the
FAA was currently conducting enforcement proceedings against National, primarily because they had 5 MRAP (Mine-Resistant Ambush Protected) vehicles on the main deck, using tie downs on seat tracks, which could have exceeded seat track limits. He also had an issue with the manuals and if they were complete or not
One person saw fluid leaking from the tail of the aircraft. Sweepers found some debris near the runway characterised as “metal” but it doesn't seem certain they were 100% certain it was from the accident flight.
From the photos I have seen in the linked NTSB report, the heavy equipment was tied down to pallets using chains. If you look through the documents you'll find them. So where would the straps come into the equation? Are the pallets then strapped to the fuselage of the aircraft?
Yes. There are fixed side rails along the outboard edge and pop up do hickeys (hi tech name) down the centerline. With regular pallets there are "pallet locks" that lie flush as the pallets roll over them and then are pulled up to form a 4 inch high "X" that catches the aft edge of the forward pallet and the forward edge of the pallet behind them. However with outsize objects you have a "floating" load that doesn't fit with the pallet locks. All you can do is strap and strap and strap.
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pozidrive....Can you clarify what you mean by "K". I guess it isn't Kelvin in this context.
From TRANSCOM loading guide on the C-130:
RESTRAINT:
1. Pallets are restrained to aircraft by detent locks. If pallet is properly built and nets installed correctly, no additional restraint is required.
2. Tie-down rings which have a 10,000 lb. rated capacity are installed in 20-inch grid pattern on the cargo floor.
3. 25,000 lb. tie-down rings are not available when dual rail system is installed. (Exception: Two, 25,000 lb. tie-down rings are located just forward of the ramp hinge.)
4. Tie-down rings located on aircraft ramp and cargo compartment walls have a rated strength of 5,000 lb.
5. Tie-down rings mounted on the aircraft dual rails at 10,000 lb.
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KenV, this isn't my area of expertise (I'm an engine guy). But my understanding is for Boeing built 747 Freighters and Boeing Converted Freighters (BCF, which is what the Bagram freighter was), they don't use seat tracks. The floor structure is someone unique to the freighter (and yes it is strengthened relative to the passenger main deck floor). The 747F main deck has a fairly elaborate cargo handling system which incorporates stops and hold-downs for the standard air-cargo pallets. Unfortunately those are not suitable for hauling large military vehicles, so alternate means are required.
Seat track on a 747 is only good for 5000lbs…You can attach a 25000 lbs chain to a D ring in a seat track but its only going to give you 5K.
Can you clarify what you mean by "K". I guess it isn't Kelvin in this context.
If as indicated by post #700 those 18-ton vehicles were loaded "floating" along the centerline, the floor was likely overloaded. The pallets are designed to transfer their loads to their edges and the edges of the pallet transfer their loads to the cargo rails, which in turn trasnfer their loads to the seat track system which distribute the loads over multiple floor beams. A free floating pallet would not be able to transfer their loads to the rails and would instead transfer the load directly into the floor beams. This creates many point loads and does not distribute the load as designed. This condition is OK under 1G when loading or unloading the aircraft, but not inflight. In the event of a high maneuver or gust load, the floor would have failed, although probably not catastrophically. But it would have required a lot of expensive repairs before the next flight. It would seem that the aircraft never got a chance to experience a maneuver or gust load since it crashed seconds after take off. But with no pallet locks involved in their restraint, it would have required a whole LOT of straps to properly restrain this load, and therefore a whole lot of D rings. I don't know the specific configuration of this freighter, but I doubt there would have been enough D rings to properly restrain three 18-ton and one 12-ton vehicles.
Last edited by KenV; 6th Feb 2015 at 20:57.
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The pallets are designed to transfer their loads to their edges and the edges of the pallet transfer their loads to the cargo rails, which in turn trasnfer their loads to the seat track system which distribute the loads over multiple floor beams.
Normally, pallets distribute their load through the rollers. The rails are horizontal guides only, and do not directly carry any vertical loads. In fact, since the normal cargo nets are attached to the edges of the pallets, the edges would be more likely to be warped slightly UPWARD, and NOT transfer any down force to the edge of the pallets.
For an oversize load, straps may be attached to the rails and/or tracks, which results in a net UPWARD load on the track/rail, and an opposite additional down force on the rollers under the pallet.
In flight, vertical restraints attached to the rails and tracks MAY also incur additional upward loads, as they provide the primary vertical restraint in turbulence. End locks in the tracks provide primary fore/aft restraint, and the rails provide lateral restraint.
With a "floating" load, ALL restraint is carried through the straps to the rails and tracks, so there will always be a net upward force on them, and the weight of the load plus restraint will be carried on the rollers. Fore/aft restraint MAY be provided by the end locks, IF they are appropriately located.
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As I figured...probably over weight...
Bagram 747 Crash Update | Opinion - Conservative
Each vehicle was 33 metric tons - 72,000 lbs. 90,000 over the 280,000 for the aircraft.
Over gross + load shift due to busted straps, locks, bailing wire, whatever they were using, = uncontrollable aircraft.
No doubt a high performance teep departure out of Bagram to avoid ground fire might have contributed to a vehicle jumping a chock, strap breaking, etc...
Bagram 747 Crash Update | Opinion - Conservative
Each vehicle was 33 metric tons - 72,000 lbs. 90,000 over the 280,000 for the aircraft.
Over gross + load shift due to busted straps, locks, bailing wire, whatever they were using, = uncontrollable aircraft.
No doubt a high performance teep departure out of Bagram to avoid ground fire might have contributed to a vehicle jumping a chock, strap breaking, etc...
It would have been prudent to strap the FWD and AFT most 12T vehicles to 9G FWD/AFT, instead of the usual 3G. They would also need 1.5G vertical restraint.
Number of straps required for the 12T vehicles:
FWD + AFT: 12.000 x 9 / 2250 (capacity of standard strap) = 48 FWD + 48 AFT.
SIDE + VERT: 12.000 x 1.5 / 2250 = 8 L + 8R + 8 VERT
Total number of straps required for each of those two vehicles alone would therefore be 120.
For the 18T vehicles, 3G FWD/AFT is sufficient, for the following calculation:
FWD + AFT: 18.000 x 3 / 2250 = 24 FWD +24 AFT
SIDE + VERT: 18.000 x 1.5 / 2250 = 12L + 12R + 12 VERT
Total number of straps needed: 84.
All in all we're looking at 492 straps. It's been a while since I was onboard a 747 freighter, or had a close look at the AHM, but I'm pretty sure finding enough restraint points would be a serious challenge - if at all possible.
Number of straps required for the 12T vehicles:
FWD + AFT: 12.000 x 9 / 2250 (capacity of standard strap) = 48 FWD + 48 AFT.
SIDE + VERT: 12.000 x 1.5 / 2250 = 8 L + 8R + 8 VERT
Total number of straps required for each of those two vehicles alone would therefore be 120.
For the 18T vehicles, 3G FWD/AFT is sufficient, for the following calculation:
FWD + AFT: 18.000 x 3 / 2250 = 24 FWD +24 AFT
SIDE + VERT: 18.000 x 1.5 / 2250 = 12L + 12R + 12 VERT
Total number of straps needed: 84.
All in all we're looking at 492 straps. It's been a while since I was onboard a 747 freighter, or had a close look at the AHM, but I'm pretty sure finding enough restraint points would be a serious challenge - if at all possible.
Last edited by SMT Member; 8th Feb 2015 at 16:31.
Don't forget though that you can double-up on the tiedown rings. That is to say, you can have one ring securing a "forward" restraint strap with another "aft" restraint strap also hooked into it.
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timber
Chains connect the vehicles to the pallet. Straps then connect the vehicle to the aircraft. A primary purpose of the timber dunnage was revealed on a web site of the military unit that planned the tiedown procedures for these vehicles. The website items are no longer discoverable. If someone else can search and find this, please indicate on pprune. The unit claimed the timber was to prevent the join between the two pallets from bending upward during ground handling. There was no other statement about the purpose of the timber.
It does seem obvious that other purposes would include load distribution and the prevention of movement on the vehicle suspension.
If the timber moved sufficiently, there would be 3 consequences:
1 Ground handling at destination would need reconsideration
2 Load distribution would suffer
3 Tightness of straps and chains that were fitted against the support of the timber would be compromised by the absense of this support, allowing vertical movement of the vehicle on its suspension. If all or part the vehicle lowers by suspension compression, tiedowns tension will vary.
The restraint system seems inadequate, even if the timber does not move. Any unplanned movement can damage the restraint or make it less effective.
I have also carried very heavy equipment on roller equipped military aircraft. Unplanned movement of the load would have been of huge concern.
It does seem obvious that other purposes would include load distribution and the prevention of movement on the vehicle suspension.
If the timber moved sufficiently, there would be 3 consequences:
1 Ground handling at destination would need reconsideration
2 Load distribution would suffer
3 Tightness of straps and chains that were fitted against the support of the timber would be compromised by the absense of this support, allowing vertical movement of the vehicle on its suspension. If all or part the vehicle lowers by suspension compression, tiedowns tension will vary.
The restraint system seems inadequate, even if the timber does not move. Any unplanned movement can damage the restraint or make it less effective.
I have also carried very heavy equipment on roller equipped military aircraft. Unplanned movement of the load would have been of huge concern.
Last edited by autoflight; 20th Feb 2015 at 12:21.
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Sweepers found some debris near the runway characterised "as metal" but it doesn't seem certain they were 100% certain it was from the accident flight
"Following the accident, the United States Air Force recovered a segment of white hydraulic (return) tubing from Runway 03 in the area of Taxiway C (Charlie). Following an examination of the tubing, Boeing indicated that the tube was part of Hydraulic System #2 and was installed in the area aft of the aft pressure bulkhead."
As the runway was swept after the departure of every heavy, the debris couldn't have come from anything other than the accident flight.
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I don't follow this at all.
Normally, pallets distribute their load through the rollers. The rails are horizontal guides only, and do not directly carry any vertical loads. In fact, since the normal cargo nets are attached to the edges of the pallets, the edges would be more likely to be warped slightly UPWARD, and NOT transfer any down force to the edge of the pallets.
Normally, pallets distribute their load through the rollers. The rails are horizontal guides only, and do not directly carry any vertical loads. In fact, since the normal cargo nets are attached to the edges of the pallets, the edges would be more likely to be warped slightly UPWARD, and NOT transfer any down force to the edge of the pallets.
The load on the pallet is netted down to the pallet at the pallet's edges. Thus the upward vertical loads and the left and right lateral loads are picked up only by the pallet rails. The rails provide all upward, left, and right restraint through the pallet's edges. The forward and aft longitudinal loads are picked up by the pallet locks which are part of the rail system. So the rails also provide all fwd and aft restraint, again thru the pallet edges.
Since this load was (reportedly) a "floating load" the rails and locks picked up none of the loads. The upward vertical loads and left and right lateral and fwd and aft longitudinal loads had to be picked up by the various straps and nets restraining the pallets. Each D ring the straps and nets were attached to were only good for 5 klbs. It seems likely that the restraint scheme was inadequate, the restraints failed, and the load shifted aft. If (as reported) parts that belong in the tail section aft of the pressure bulkhead were found on the runway (presumably on the departure end of the runway beyond the point where the aircraft rotated) then the load shifted aft violently enough to rupture the pressure bulkhead AND the aft fuselage skin, enabling parts to fall out of the tail section after rotation. If that was indeed what happened, it seems likely that there was insufficient pitch authority to counteract the aft CG shift, resulting in the crash. There's a small chance such a failure could rupture the hydraulic lines controlling the elevators, which would result in loss of pitch control to counteract the aft CG shift, also resulting in the crash.
Hope this clarified.
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They definitely lost system one, evident by the fact the nose gear doors were open but the gear failed to retract, and they show that the wing gear is retracted from the computer generated pictures and overlay of the gear in a down position.
System 1 & 2 hydraulic pressure and return lines are grouped together on the left side passing through the rear pressure bulkhead so it's possible system 2 was lost as well.
If so they would have lost both the left inboard and left outboard elevator leaving them with only 50% elevator control and 1/2 rate stabilizer movement.
It appears from the simulator (not designed or certified for outside CofG) exercise that full nose down elevator and forward trim "may" have allowed them to control the aircraft but that's with full flight controls!
System 1 & 2 hydraulic pressure and return lines are grouped together on the left side passing through the rear pressure bulkhead so it's possible system 2 was lost as well.
If so they would have lost both the left inboard and left outboard elevator leaving them with only 50% elevator control and 1/2 rate stabilizer movement.
It appears from the simulator (not designed or certified for outside CofG) exercise that full nose down elevator and forward trim "may" have allowed them to control the aircraft but that's with full flight controls!
@SMOC
The Chariman's Factual Report
http://dms.ntsb.gov/public%2F57000-5...3%2F567126.pdf
is pretty chilling.
Cargo Loadmasters are not certified. Only briefly trained. Are not trained in securing loads like 18 tonne vehicles at all. Pallets were secured to seat rails and other places. Some seat rails used were not approved by Boeing for the purpose.
The final report is going for sure to be highly critical of parts of the operation.
FDR factual report - simulations
http://dms.ntsb.gov/public%2F57000-5...3%2F567192.pdf
At least one 12 tonne vehicle broke free and struck the pressure bulkhead (witness marks) and severed the FDR, CVR and #1 and #2 (and poss #3) hydraulic systems. THS jack screw possibly severed too.
Loss of THS jack screw, or loss of hyd combined with cg shift rendered aircraft uncontrollable in pitch.
Loss of jack screw would turn elevator into a 'servo tab' on THS and reverse controls.
FDR and CVR are the first things to go and nothing at all of the anomalous event is recorded.
http://dms.ntsb.gov/public%2F57000-5...3%2F567193.pdf
CVR transcript
Some load shift had occurred on previous flight. This had been a fuel stop.
System 1 & 2 hydraulic pressure and return lines are grouped together on the left side passing through the rear pressure bulkhead so it's possible system 2 was lost as well.
If so they would have lost both the left inboard and left outboard elevator leaving them with only 50% elevator control and 1/2 rate stabilizer movement.
If so they would have lost both the left inboard and left outboard elevator leaving them with only 50% elevator control and 1/2 rate stabilizer movement.
The Chariman's Factual Report
http://dms.ntsb.gov/public%2F57000-5...3%2F567126.pdf
is pretty chilling.
Cargo Loadmasters are not certified. Only briefly trained. Are not trained in securing loads like 18 tonne vehicles at all. Pallets were secured to seat rails and other places. Some seat rails used were not approved by Boeing for the purpose.
The final report is going for sure to be highly critical of parts of the operation.
FDR factual report - simulations
http://dms.ntsb.gov/public%2F57000-5...3%2F567192.pdf
At least one 12 tonne vehicle broke free and struck the pressure bulkhead (witness marks) and severed the FDR, CVR and #1 and #2 (and poss #3) hydraulic systems. THS jack screw possibly severed too.
Loss of THS jack screw, or loss of hyd combined with cg shift rendered aircraft uncontrollable in pitch.
Loss of jack screw would turn elevator into a 'servo tab' on THS and reverse controls.
FDR and CVR are the first things to go and nothing at all of the anomalous event is recorded.
http://dms.ntsb.gov/public%2F57000-5...3%2F567193.pdf
CVR transcript
Some load shift had occurred on previous flight. This had been a fuel stop.
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Jet Jockey, That's a bit harsh calling it a joke.
I can understand the situation where an operation gradually changes, in this case from standard palletised loads to heavy vehicles. The effects of this change aren't acknowledged. The training and procedures aren't updated to reflect the change. The people involved don't realise they are working beyond their competence.
I hesitate to use the old cliche, but isn't it the Swiss Cheese again?
I can understand the situation where an operation gradually changes, in this case from standard palletised loads to heavy vehicles. The effects of this change aren't acknowledged. The training and procedures aren't updated to reflect the change. The people involved don't realise they are working beyond their competence.
I hesitate to use the old cliche, but isn't it the Swiss Cheese again?