I read a report on the DC-10 that lost an engine and crashed at O'Hara due to asymmetric forces on the wing?

Question

I read the engine seperated from its pylon, and flipped over the wing, severing the Hydraluic lines, and when the pilot selected retract, the slats and flaps could not, and gradually moved all the way "Down/out" causing aysmmetric thrust and the crash. Have newer aircraft fixed that design, or does a loss of pressure cause the Flaps and Slats to extend, needed or not? It was a DC-10-10,1979 was the year. What are the usual check offs for a such a catastrophic loss (physical that is, the engine has departed the wing) in such a situation?

Answer 1

Flight 191 was taking off from Runway 32R. The weather was clear and the visibility was 15 miles. During the takeoff rotation, the left engine and pylonassembly and about 3 ft of the leading edge of the left wing separated fromthe aircraft and fell to the runway. Flight 191 continued to climb to about 325' above the ground and then began to roll to the left. The aircraft continued to roll to the left until the wings were past the vertical position,and during the roll, the aircraft's nose pitched down below the horizon.

Flight 191 crashed into the open field and the wreckage scattered into anadjacent trailer park. The aircraft was destroyed in the crash and subsequent fire. Two hundred and seventy-one persons on board Flight 191 were killed;
two persons on the ground were killed, and two others were injured. An old aircraft hangar, several automobiles, and a mobile home were destroyed.

The National Transportation Safety Board determines that the probable cause of this accident was the asymmetrical stall and the ensuing roll of the air-
craft because of the uncommanded retraction of the left wing outboard leading edge slats and the loss of stall warning and slat disagreement indication systems resulting from maintenance-induced damage leading to the separation of the No. 1 engine and pylon assembly at a critical point during takeoff. The separation resulted from damage by improper maintenance procedures which led to
failure of the pylon structure.

Contributing to the cause of the accident were the vulnerability of the design of the pylon attach points to maintenance damage; the vulnerability of the
design of the leading edge slat system to the damage which produced asymmetry; deficiencies in Federal Aviation Administration surveillance and reporting sys-
tems which failed to detect and prevent the use of improper maintenance proced-
ures; deficiencies in the practices and communications among the operators, the manufacturer, and the FAA which failed to determine and disseminate the
particulars during previous maintenance damage incidents; and the intolerance of prescribed operational procedures to this unique emergency.

Findings (p. 67)

1. The engine and pylon assembly separated either at or immediately after
takeoff. The flightcrew was committed to continue the takeoff.
2. The aft end of the pylon assembly began to separate in the forward flange
of the aft bulkhead.
3. The structural separation of the pylon was caused by a complete failure of
the forward flange of the aft bulkhead after its residual strength had been
critically reduced by the fracture and subsequent service life.
4. The overload fracture and fatigue cracking on the pylon aft bulkhead's
upper flange were the only preexisting damage on the bulkhead. The length of
the overload fracture and fatigue cracking was about 13 inches. The fracture
was caused by an upward movement of the aft end of the pylon which brought the
upper flange and its fasteners into contact with the wing clevis.
5. The pylon to wing attach hardware was properly installed at all attachment
points.
6. All electrical power to the No. 1 AC generator bus and No. 1 DC bus was
lost after the pylon separated. The captain's flight director instrument, the
stall warning system, and the slat disagreement warning light systems were
rendered inoperative. Power to these buses was never restored.
7. The No. 1 hydraulic system was lost when the pylon separated. Hydraulic
systems No. 2 and No. 3 operated at their full capability throughout the flight.
Except for spoiler panels No. 2 and No. 4 on each wing, all flight controls were operating.
8. The hydraulic lines and followup cables of the drive actuator for the left wing's outboard leading edge slat were severed by the separation of the pylon and the left wing's outboard slats retracted during climbout. The retraction
of the slats caused an asymmetric stall and subsequent loss of control of the aircraft.
9. The flightcrew could not see the wings and engines from the cockpit. Because of the loss of the slat disagreement light and the stall warning system, the flightcrew would not have received an electronic warning of either the slat
asymmetry or the stall. The loss of the warning systems created a situation which afforded the flightcrew an inadequate opportunity to recognize and prevent the ensuing stall of the aircraft.
10. The flightcrew flew the aircraft in accordance with the prescribed emergency procedure, which called for the climbout to be flown at V2 speed. V2 was 6 KIAS below the stall speed for the left wing. The deceleration to V2 speed caused the aircraft to stall. The start of the left roll was the only warning the pilot had of the onset of the stall.
11. The pylon was damaged during maintenance performed on the accident aircraft at American Airline's Maintenance Facility at Tulsa, Oklahoma, on March 29 and 30, 1979.
12. The design of the aft bulkhead made the flange vulnerable to damage when the pylon was being separated or attached.
13. American Airlines engineering personnel developed an ECO to remove and reinstall the pylon and engine as a single unit. The ECO directed that the combined engine and pylon assembly be supported, lowered, and raised by a forklift. American Airlines engineering personnel did not perform an adequate evaluation of either the capability of the forklift to provide the required precision for the task, or the degree of difficulty involved in placing the lift properly, or the consequences of placing the lift improperly. The CO did not emphasize the precision required to place the forklift properly.
14. The FAA does not approve the carriers' maintenance procedures, and a carrier has the right to change its maintenance procedures without FAA approval.
15. American Airlines personnel removed the aft bulkhead's bolt and bushing before removing the forward bulkhead attach fittings. This permitted the forward bulkhead to act as a pivot. Any advertent or inadvertent loss of forklift support to the engine and pylon assembly would produce an upward
movement at the aft bulkhead's upper flange and bring it into contact with the wing clevis.
16. American Airlines maintenance personnel did not report formally to their maintenance engineering staff either their deviation from the removal sequence contained in the ECO or the difficulties they had encountered in accomplishing
the ECO's procedures.
17. American Airline's engineering personnel did not perform a thorough evaluation of all aspects of the maintenance procedures before they formulated
the ECO. The engineering and supervisory personnel did not monitor the performance of the ECO to ensure either that it was being accomplished properly or if their maintenance personnel were encountering unforeseen difficulties in
performing the assigned tasks.
18. The nine situations in which damage was sustained and cracks were found on the upper flange were limited to those operations wherein the engine and pylon assembly was supported by a forklift.
19. On December 19, 1978, and Feb. 22, 1979, Continental Airlines maintenance personnel damaged aft bulkhead upper flanges in a manner similar to the damage noted on the accident aircraft. The carrier classified the cause of the damage as maintenance error. Neither the air carrier nor the manufacturer interpreted the regulation to require that it further investigate or report the damages to the FAA.
20. The original certification's fatigue-damage assessment was in conformance with the existing requirements.
21. The design of the stall warning system lacked sufficient redundancy; there was only one stickshaker motor; and further, the design of the system did not provide for crossover information to the left and right stall warning computers
from the applicable leading edge slat sensors on the opposite side of the aircraft.
22. The design of the leading edge slat system did not include positive mechanical locking devices to prevent movement of the slats by external loads following a failure of the primary controls. Certification was based upon acceptable flight characteristics with an asymmetrical leading edge slat condition.
23. At the time of DC-10 certification, the structural separation of an engine pylon was not considered. Thus, multiple failures of other systems resulting from this single event was not considered.

Answer 2

You have it completely wrong. When the engine separated at rotation and flew over the top of the wing it severed hydraulic lines that provide pressure to the leading edge slat actuators. Without pressure the slats on that wing retracted resulting in a loss of lift on that wing. It was the slat retracting with the oposite slat still extended that caused the loss of control not the loss of the engine itself. Had the slat not retracted the crew would have likely recovered, continued the climbour and returned for landing. even with the weight embalance. The crew never touched the flap/slat selector since they thought they were dealing with an engine failure. During an engine out takeoff you would never retract the flaps until completion of the second segment climb. The crew had no idea that the engine had completely separated from the wing nor that the slats on that wing had retracted. When flight crews duplicated the exact same sequence of events in the simulator every crew crashed. There was simply nothing that the crew could have done differently given the information they had and the multiple failures they had to deal with.

Answer 3

Faulty engine mounting procedure led to a damaged pylon bolt which eventually led to the engine breaking away. With the other front engine on takeoff power, the pilots already had an asymmetric power condition which led to the aircraft veering to one side.

Coupled with the above, the slats on the side of the disabled engine also retracted due to lack of hydraulic pressure with which they were kept extended. This resultant loss of lift coupled with the missing engine further aggravated the situation which could not be controlled and led to the crash.

Since 1979 many design improvements have been made (including correct maintenance procedures) which has made the DC-10 a safe and reliable aircraft. This is a rather understated aircraft but its applications even up to this date show the aircraft to be a very fine example as a pioneer in the field of wide body jets.

Answer 4

As Baron says, when an engine drops off and the other/s continue to run at full thrust, the aircraft will be trying to turn in the direction of the missing engine. Pretty hard to fight this obviously.

The airline employees did damage the pylon, but the design of the engine mount was such that it was EASY to damage it. Better designs and strict adherence to proper procedures corrected that.

Answer 5

It was bad maintenance at American Airlines that caused the crash (though other airlines were doing the same thing, what they did was remove the engine and the pylon in one go instead of separately, that caused metal fatigue to build up (in which case it was only a matter of time before an engine came off)). All the airlines that were incorrectly maintaining the aircraft changed their procedures to do it properly.

Well maintained aircraft tend not to fall out of the sky while badly maintained craft tend to do so a lot.

Answer 6

Well, what you read is somewhat correct. First for your info and learning...the engine pylons are designed to make the engine "thrust" up and over the wing in the event of a pylon breaking and engines leaving the plane. What happened was 2 things. The sudden loss of a hydraulic source to the left side of the airplane resulted in assymetrical flap/slat retractions resulting in assymetrical lift...adding to this was assymetrical thrust...being produced from the good engine running at take off power...which is higher than climb or cruise power...this produces a yaw/roll situation as well....and with these 2...put alot of people....their bags...and ALOT of fuel...you have a heavy....essentially ONE highly efficient right wing...with one engine in the wrong spot....produced a sad tragedy.....hope this helps you!!

Jonathan S
ATP-LRJET
CFI
AGI

Answer 7

Pretty techy question. I know the crash you are talking about, though. I would think the a/c was simply not designed to have something as heavy as an engine go dropping off and was downed due to the out of balace condition. They can't have major pieces go falling off. There is no "check off" for a departing wing or tail either. I think the assymetric thrust PROBABLY was caused by the missing engine?? Ya think???
Ultimately the problem was improper maintenance, they were removing/installing engines with forklifts to save time and cracked the engine spar.

Answer 8

Looks as though most of you guys answered this right, however the DC-10 does not have leading edge wing slats. They do however have leading edge wing flaps to increase lift.

Answer 9

Check out findings NTSB findings 6, 8, 9, 21 from this link:
http://www.kls2.com/cgi-bin/arcfetch?db=sci.aeronautics.airliners&id=[e-mail]%3E&match=50&query=dc

Answer 10

http://www.airdisaster.com/forums/showthread.php?t=55171
front fan blow away
middle engine #2
engine stayed intacked