Turkish Airlines Flight 981 (Crash 1974)

[flash8]

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] (https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981#cite_note-Tetelman-12)

Now, I thought I knew everything publically available surrounding Ship 29, having read the report in depth, all of the books available and various websites over many years - however I never knew this and am quite astounded (referenced from Wikipedia).


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.

[DaveReidUK]

This puts a different slant on some aspects of this crash.

Does it ?

Who is suggesting that in flight the door would be subject to even 15 psi ?

[blind pew]

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.

[flash8]

Does it ?I think so, not that it was ultimately contributory but that this was completely omitted from the subsequent investigation and report. That it didn't make it is puzzling because much of the report centered around the latching mechanism and any modifications even if found to be irrelevant would have been covered.


Who is suggesting that in flight the door would be subject to even 15 psi ?
Not an engineer however this may well have influenced other components and hastened the failure.

Off topic Blind Pew is your book still available? The machinations of BEA circa '72 hold great interest for me.

[DH106]

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.

[Feathers McGraw]

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.

[Anilv]

Read 'Destination Disaster' a book by Paul Eddy. Read it more than 30 years ago and have been re-reading it every 5 years or so .

Anilv

[DH106]

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.

Exactly my point - pressure by definition is 'force per unit area', NOT a point force. So at the very least the quoted units of 'psi' are incorrect. Pounds force perhaps?