Today marks the 45th anniversary of the crash of Turkish Airlines (THY) flight 981, a DC-10-10 (TC-JAV) departing Paris Orly on a short flight to London Heathrow, a continuation of a flight from Istanbul. All 346 people aboard the aircraft were killed, including 12 crew and 334 passengers. This was the first hull loss of a DC-10 though an accident five months earlier had resulted in the death of a passenger aboard a National Airlines DC-10.
The main crash site was in the Ermenonville Forest, northeast of Paris,
though the aft cargo door and other debris including a row of seats
with six passengers was found approximately 15 km
earlier along the flight path. The discovery of the detached cargo door
quickly focused the investigation on similarities to a previous accident
involving American Airlines flight 96 near Windsor, Ontario. The French
investigation concluded the following:
5.2 Causes of the accident
The accident was the result of the ejection in flight of the aft cargo door on the left-hand side: the sudden depressurization which followed led to the disruption of the floor structure, causing six passengers and parts of the aircraft to be ejected, rendering No 2 engine inoperative and impairing the flight controls (tail surfaces) so that it was impossible for the crew to regain control of the aircraft.
The underlying factor in the sequence of events leading to the accident was the incorrect engagement of the door latching mechanism before take-off. The characteristics of the design of the mechanism made it possible for the vent door to be apparently closed and the cargo door apparently locked when in fact the latches were not fully closed and the lock pins were not in place.
It should be noted, however, that a view port was provided so that there could be a visual check of the engagement of the lock pins.
This defective closing of the door resulted from a combination of various factors:
- incomplete application of Service Bulletin 52-37;
- incorrect modifications and adjustments which led, in particular, to insufficient protrusion of the lock pins and to the switching off of the flight deck visual warning light before the door was locked;
- the circumstances of the closure of the door during the stop at Orly, and, in particular, the absence of any visual inspection, through the view port, to verify that the lock pins were effectively engaged, although at the time of the accident inspection was rendered difficult by the inadequate diameter of the view port.
Finally although there was apparent redundancy of the flight control systems, the fact that the pressure relief vents between the cargo compartment and the passenger cabing were inadequate and that all the flight control cables were routed beneath the floor placed the aircraft in grave danger in the case of any sudden depressurization causing substantial damage to that part of the structure.
All these risks had already become evident, nineteen months earlier, at the time of the Windsor accident, but no efficacious corrective action had followed.
Today's Featured Map illustrates the initial path east from Orly to the Coulommiers VOR, where a left turn was made towards the Montdidier VOR, plus the main crash site and the location of the cargo door and associated debris.
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Karl L. Swartz.
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