Turkish Airlines Flight 981 (Crash 1974)
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Turkish Airlines Flight 981 (Crash 1974)
In the company's investigation, it was noted that during a stop in Turkey, ground crews had filed the cargo door's locking pins down to less than a quarter of an inch (6.4 millimetres), when they experienced difficulty closing the door. Subsequent investigative tests proved the door yielded to approximately 15 psi (100 kPa) of pressure, in contrast to the 300 psi (2,100 kPa) that it had been designed to withstand.[12]
From the referenced Chicago tribune article:
Shortly after Alan Tetelman* of Failure Analysis arrived in Paris to inspect the wreckage, he noted that the pins on the cargo door had been filed down deliberately. By asking a few questions, he then learned that on a stop in Turkey, the ground crews had trouble closing the door, which then closed effortlessly by taking less than a quarter inch off the pins. By doing so, it was proved through tests, the door yielded to about 15 pounds of pressure, while it had been designed to withstand 300 pounds.
This puts a different slant on some aspects of this crash. Again I am astounded by this as it is entirely new to me.
Any thoughts?
* Professor of Engineering and Applied Science UCLA - Who then lost his life in 1978 in the PSA 727 mid-air... an amazing coincidence.
Falsified documentarian
After the US carrier had the door fail after being hit by a coffin there was a mandatory modification. Which hadn't been made but the paperwork had been falsified and stamped at Douglas.
Flew the sister ships including the one allegedly responsible for the Concorde crash.
Flew the sister ships including the one allegedly responsible for the Concorde crash.
Thread Starter
Does it ?
Who is suggesting that in flight the door would be subject to even 15 psi ?
Off topic Blind Pew is your book still available? The machinations of BEA circa '72 hold great interest for me.
How can the door as a whole be subject to many times the pressure of standard pressurisation loads?
Do these figures refer to pressures exerted on some of the door's locking components perhaps? But you'd more normally see such values expressed as a force rather than a pressure.
Do these figures refer to pressures exerted on some of the door's locking components perhaps? But you'd more normally see such values expressed as a force rather than a pressure.
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I don't think that the figures quoted apply to pressure per square foot, they apply to the linear force required to close the locking mechanism.
The locking pins were designed to baulk on a flange that rotated to clear their path as the locking motor drove the mechanism over centre. After the Windsor incident changes were made to increase the load required by increasing the pin length and then later by adding a support bracket that prevented the locking shaft from bending. The electrical cabling was beefed up too, presumably to try to reduce any voltage drop as the motor approached stall and the current increase then caused a torque reduction. These changes were supposed to put closing the handle on an improperly secured door beyond human strength, but had not all been applied to the THY aircraft involved.
The problem with the particular door on the Paris flight is that not only had the pins been shortened but the limit switch had been shimmed to indicate door closed when it wasn't anywhere near to being so. There was also a porthole with an indicator showing the position of the locking mechanism, however the operator working that day had not been trained on what it meant and also couldn't read the english text painted around it. Because of the mis-rigging the door closed easily under motor drive and the locking handle closed without any apparent effort.
The locking pins were designed to baulk on a flange that rotated to clear their path as the locking motor drove the mechanism over centre. After the Windsor incident changes were made to increase the load required by increasing the pin length and then later by adding a support bracket that prevented the locking shaft from bending. The electrical cabling was beefed up too, presumably to try to reduce any voltage drop as the motor approached stall and the current increase then caused a torque reduction. These changes were supposed to put closing the handle on an improperly secured door beyond human strength, but had not all been applied to the THY aircraft involved.
The problem with the particular door on the Paris flight is that not only had the pins been shortened but the limit switch had been shimmed to indicate door closed when it wasn't anywhere near to being so. There was also a porthole with an indicator showing the position of the locking mechanism, however the operator working that day had not been trained on what it meant and also couldn't read the english text painted around it. Because of the mis-rigging the door closed easily under motor drive and the locking handle closed without any apparent effort.