Engine Failure Of Flight 191 Engineering Essay

Engine Failure Of Flight 191 Engineering Essay

The loss of the engine by itself should non hold been plenty to do the accident. [ 12 ] Flight 191 would hold been absolutely capable of returning to the airdrome utilizing its staying two engines, as the DC-10 is capable of remaining airborne with any individual engine out of operation. However, several other factors combined to do a ruinous loss of control.

The engine separation had severed the hydraulic lines that controlled the aircraft ‘s leading-edge wing splines ( retractable devices that decrease a wing ‘s stall velocity during takeoff and landing ) . The harm to the lines caused a loss of hydraulic force per unit area, which in bend led to uncommanded abjuration of the outboard slats in the left wing. [ 1 ] Unlike other aircraft designs, the DC-10 did non include a separate mechanism to lock the splines in topographic point. [ 1 ]

Research workers examined the flight informations recording equipment ( FDR ) and conducted air current tunnel trials and flight simulator trials to understand the flight of flight 191 after the engine detached and the splines retracted. These trials established that the harm to the flying prima border and abjuration of the splines increased the stall velocity of the left wing from 124kt to 159kt. [ 1 ]

Comparison of the FDR informations and the simulator trials showed that the pilots of flight 191 had followed the process for engine failure at take-off. This process called for the captain to travel to VHYPERLINK “ hypertext transfer protocol: //en.wikipedia.org/wiki/V_Speeds # Other_reference_speeds ” 2 ( standard safety takeoff velocity ) which for flight 191 was 153kt, 6kt below the stall velocity. [ 1 ] At the clip the engine fell off the aircraft, flight 191 was already going at 165kt, safely above the stall velocity. Therefore, by decelerating the aircraft to 153kt in conformity with the exigency process, the pilots unwittingly induced the stall which proved fatal. Following this accident, McDonnell Douglas revised the process, reding that if the aircraft was already winging faster than V2 plus 10kt the pilots should keep a border of 10kt above V2. [ 1 ]

The DC-10 incorporates two warning devices which might hold alerted the pilots to the impending stall: the slat dissension warning visible radiation which should hold illuminated after the uncommanded abjuration of the splines, and the stall warning system ( stick-shaker ) which activates near to the stall velocity. Unfortunately, both of these warning devices were powered by an electric generator driven by the no. 1 engine ; following the loss of that engine, they both became inoperative. [ 1 ]

[ edit ] Engine separation

An FAA diagram of the DC-10 engine and pylon assembly bespeaking the failed aft pylon attach adjustment.

From an examinaton of the degage engine, the NTSB concluded that the pylon fond regard had been damaged before the clang. [ 1 ] Research workers looked at the plane ‘s care history and found that its most recent service was eight hebdomads before the clang, in which engine figure one had been removed from the aircraft, nevertheless the pylon, the set uping keeping the engine onto the wing, had been damaged during the process. The original process called for remotion of the engine prior to the remotion of the engine pylon, but American Airlines had begun to utilize a process that saved about 200 man-hours per aircraft and “ more significantly from a safety point of view, it would cut down the figure of gulfs ( i.e. , hydraulic and fuel lines, electrical overseas telegrams, and wiring ) from 72 to 27. “ [ 1 ]

The new process involved mechanics taking the engine with the pylon as one unit, instead than the engine, and so the pylon. A big forklift was used to back up the engine while it was being detached from the flying – a process that was found to be extremelly hard to put to death successfully, due to troubles with keeping the engine assembly directly while it was being removed.

The field service representative from the maker, McDonnell-Douglas, said it would “ non promote this process due to the component of hazard ” and had so advised American. However, McDonnell-Douglas “ does non hold the authorization to either O.K. or disapprove the care processs of its clients. “ [ 1 ]

The accident probe besides concluded that the design of the pylon and next surfaces made the parts hard to service and prone to damage by care crews. The NTSB reported that there were two different attacks to the one-step process: utilizing an overhead hoist or utilizing a forklift. United Airlines used a hoist ; American and Continental Airlines used a forklift. Harmonizing to the NTSB, all the instances “ wherein impact harm was sustained and clefts found involved the usage of the forklift. “ [ 1 ]

Under the process American used, if the forklift was in the incorrect place, the engine would sway like a see-saw and jam against the pylon fond regard points. The forklift operator was guided by manus and voice signals ; the place had to be spot-on or could do harm. Management was cognizant of this. The alteration to the aircraft involved in Flight 191 did non travel swimmingly. Engineers started to unplug the engine and pylon, but changed displacement midway through. When work continued, the pylon was jammed on the wing and the forklift had to be repositioned. This was of import grounds because, in order to unplug the pylon from the wing, a bolt had to be removed so that the rim could strike the clevis. The process used caused an indenture that damaged the clevis pin assembly and created an indenture in the lodging of the self-aligning bearing, which in bend weakened the construction sufficiently to do a little emphasis break. The break went unnoticed for several flights, acquiring worse with each flight. During Flight 191 ‘s takeoff, adequate force was generated to eventually do the pylon to neglect. At the point of rotary motion, the engine detached and was flipped over the top of the wing.

[ edit ] Conclusion

The findings of the probe by the National Transportation Safety Board ( NTSB ) were released on December 21, 1979: [ 1 ]

The National Transportation Safety Board determines that the likely cause of this accident was the asymmetrical stall and the resulting axial rotation of the aircraft because of the uncommanded abjuration of the left flying outboard taking border splines and the loss of stall warning and slat dissension indicant systems ensuing from maintenance-induced harm taking to the separation of the No. 1 engine and pylon assembly at a critical point during takeoff. The separation resulted from harm by improper care processs which led to failure of the pylon construction.

Lending to the-cause of the accident were the exposure of the design of the pylon attach points to maintenance harm ; the exposure of the design of the taking border slat system to the harm which produced dissymmetry ; lacks in Federal Aviation Administration surveillance and describing systems which failed to observe and forestall the usage of improper care processs ; lacks in the patterns and communications among the operators, the maker, and the FAA which failed to find and circulate the specifics sing old care harm incidents ; and the intolerance of prescribed operational processs to this alone exigency.

The NTSB determined that the harm to the left flying engine pylon had occurred during an earlier engine alteration at the American Airlines aircraft care installation in Tulsa, Oklahoma on March 29 and 30, 1979. [ 1 ] The grounds came from the rim, a critical portion of the pylon assembly.

[ edit ] Aftermath

First respondents study the Flight 191 clang site in Des Plaines, Illinois.

Problems with DC-10s were discovered as a cause of the accident, including lacks in both design specifications and care processs which made harm really likely. In response to this incident, American Airlines was fined by the United States authorities $ 500,000 for improper care processs [ 12 ] .

Two hebdomads after the accident, on June 6, the FAA ordered all DC-10s to be grounded until all jobs were solved. The prohibition was lifted on July 13. [ 13 ]

The clang of another DC-10 in November 1979, Air New Zealand Flight 901, would merely add to the DC-10 ‘s negative repute at the clip – nevertheless, Flight 901 was caused by several human and environmental factors non related to the airworthiness of the DC-10, and the aircraft was later wholly exonerated in that accident. Although McDonnell Douglas employees participated in an “ I ‘m proud of the DC-10 ” run, the company ‘s portions fell more than 20 % following the clang of Flight 191. In 1997, the McDonnell Douglas company was taken over by its challenger, Boeing.

Despite the safety concerns, the DC-10 went on to outsell its closest rival, the Lockheed L-1011 TriStar, by about 2 to 1. This was due to the L-1011 ‘s launch being delayed, the debut of the DC-10-30 long scope theoretical account without a viing TriStar discrepancy, and the DC-10 holding a greater pick of engines ( the L-1011 was merely available with Rolls-Royce engines, while the DC-10 could be ordered with General Electric or Pratt HYPERLINK “ hypertext transfer protocol: //en.wikipedia.org/wiki/Pratt_ & A ; _Whitney ” & amp ; HYPERLINK “ hypertext transfer protocol: //en.wikipedia.org/wiki/Pratt_ & A ; _Whitney ” Whitney engines ) . The DC-10 plan besides benefited from obtaining a U.S. Air Force contract to develop a long-range refueller, which culminated in the KC-10 Extender. Lockheed had no such support for the TriStar, and halted production in 1982.

NTSB probe

The clang of flight 191 brought ferocious unfavorable judgment from the media because it was the 4th fatal accident affecting a DC-10 at the clip. Six hundred and 22 people had died in DC-10 accidents, including flight 191. As the conditions was perfect for winging and there was no indicant that a flock of birds or another plane caused the clang, the remains of engine # 1 raised serious concerns of the safety of the DC-10. The detached engine was non the lone concern, as the populace wanted to cognize whether the degage engine was the lone cause of the clang. Research workers wondered if a fire was perchance the cause, as this was backed up by testimony from air traffic accountant Ed Rucker who said he saw a ‘flash ‘ from the wing. This raised concerns that 191 was the consequence of a terrorist onslaught. Sixty informants who saw the plane on the track ruled out a bomb, as they all saw engine # 1 swing frontward so toss up and over the top of the wing, which pointed to structural failure as the cause.

The findings of the probe by the National Transportation Safety Board ( NTSB ) were released on December 21, 1979. It revealed the likely cause to be attributable to damage to the left flying engine pylon that occurred during an earlier engine alteration at American Airlines ‘s aircraft care installation in Tulsa, Oklahoma on March 29 and 30, 1979. citation web |url=http: //amelia.db.erau.edu/reports/ntsb/aar/AAR79-17.pdf |title=NTSB ( National Transportation Safety Board ) Report ] Evidence came from the rim, a critical portion of the pylon assembly. It was revealed to be damaged before the clang, and research workers looked at the plane ‘s care history and found it was serviced eight hebdomads before the clang. The pylon was damaged due to an ill-thought-out engine remotion process. The original process called for remotion of the engine prior to the remotion of the engine pylon. To salvage clip and costs, American Airlines, without the blessing of McDonnell Douglas, had begun to utilize a faster process. They instructed their mechanics to take the engine with the pylon all together as one unit. A big forklift was used to back up the engine while it was being detached from the wing. This process was highly hard to put to death successfully, due to troubles with keeping the engine assembly directly while it was being removed.

This method of engine-pylon remotion was used to salvage adult male hours and was encouraged despite differences with the maker ‘s specifications on how the process was supposed to be performed. The accident probe besides concluded that the design of the pylon and next surfaces made the parts hard to service and prone to damage by care crews. Harmonizing to the History Channel, citation picture

rubric = The Crash of Flight 191

url = hypertext transfer protocol: //store.aetv.com/html/product/index.jhtml? id=71451

publishing house = The History Channel

publisherid = AAE-71451

medium = DVD ] United Airlines and Continental Airlines were besides utilizing a one-step process. After the accident, clefts were found in the bulkheads of DC-10s in both fleets.

The process used for care did non continue swimmingly. If the forklift was in the incorrect place, the engine would sway like a see-saw and jam against the pylon fond regard points. The forklift operator was guided by manus and voice signals ; the place had to be spot-on or could do harm, but direction was unaware of this. The alteration to the aircraft involved in flight 191 did non travel swimmingly ; applied scientists started to unplug the engine and pylon but changed displacement midway through ; when work continued, the pylon was jammed on the wing and the forklift had to be re-positioned. This was of import grounds because, in order to unplug the pylon from the wing, a bolt had to be removed so that the rim could strike the clevis. The process used caused an indenture that damaged the clevis pin assembly and created an indenture in the lodging of the self-aligning bearing, which in bend weakened the construction sufficiently to do a little emphasis break. The break went unnoticed for several flights, acquiring worse with each flight that the plane had taken. During flight 191 ‘s takeoff, adequate force was generated to eventually do the pylon to neglect. At the point of rotary motion, the engine detached and was flipped over the top of the wing.

The loss of the engine by itself should non hold been plenty to do the accident. During an interview on Seconds From Disaster, Former NTSB research worker Michael Marx mentioned there were other incidents where the engine fell off, yet they landed without incident. Flight 191 would hold been absolutely capable of returning to the airdrome utilizing its staying two engines, as the DC-10 is capable of remaining airborne with any individual engine out of operation. Unfortunately, several other factors combined to do a ruinous loss of control.

The separation of the engine severed electrical wiring and hydraulic lines which were routed through the taking border of the wing. The harm to the lines caused a loss of hydraulic force per unit area, which in bend led to uncommanded abjuration of the outboard slats in the port wing. The DC-10 design included a back-up hydraulic system which should hold been plenty to maintain the splines in topographic point ; nevertheless, both lines are excessively close together, a design besides used on the DC-9. There should hold been adequate fluid to maintain the splines extended, so research workers wanted to cognize why they were ne’er re-extended by the pilot. The reply came from the terminal of the recording on the CVR. The figure 1 engine powered both the recording equipment and the slat warning system, which left the pilot and copilot with no manner of cognizing about the place of the splines. Research workers examined the FDR to see what occurred after the engine detached. The process called for the captain to travel to V2 which he did absolutely, but research workers found that it said nil about incidents where the velocity was already above V2, as it was in this instance. Therefore, the pilot had to cut down velocity. Simulator trials were done to see if this made a difference ; 13 pilots followed the process 70 times and non one was able to retrieve. The NTSB concluded that cut downing velocity when the splines are back may really hold made it more hard for the pilot to retrieve control of the aircraft. When a DC-10 is about to procrastinate it gives two warnings: The first is the stick-shaker which causes the yoke to vibrate, and the 2nd is a warning visible radiation that flashes. These combined warnings should hold alerted the pilots to increase velocity instantly. American Airlines had chosen to hold the stick-shaker on the pilot ‘s side merely, but the stick-shaker did non run because it was powered by the losing left engine. In the event of an engine failure, it is possible for the flight applied scientist to exchange the pilot ‘s controls to a backup power supply. However, research workers determined that in order for him to entree the necessary switch, the applied scientist would hold had to unfasten his place belt, stand up, and turn around.

The DC-10 hit the land with a bank of 112AA° , and at a nose-down attitude of 21AA° . The NTSB concluded that given the fortunes of the state of affairs, the pilots could non be moderately blamed for the resulting accident.

In his book “ Blind Trust ” , [ cite book | rubric = Blind Trust | last=Nance | first=John J. | authorlink=John J. Nance | publishing house = William Morrow & A ; Co | isbn = 0-688-05360-2 | twelvemonth = 1987 ] John J. Nance argues that the 1978 Airline Deregulation Act caused mayhem and induced cost-cutting in the industry, bring forthing a serious eroding of the border of safety for riders. Nance argues that the industry “ reverted from an industry under partial surveillance to an industry running on the award system ” .

Aftermath

Problems with DC-10s were discovered as a cause of the accident, including lacks in both design specifications and care processs which made harm really probably. Since the clang happened merely before a Western Airlines DC-10 crashed in Mexico City and five old ages after a Turkish Airlines DC-10 crashed near Paris, the FAA rapidly ordered all DC-10s to be grounded until all jobs were solved. The consequence of the problem-solving was an arguably more efficient and safe DC-10.

The US authorities fined American Airlines $ 500,000 for improper care processs, but the insurance colony for the replacing of the aircraft gave American Airlines $ 25,000,000 beyond the sum of the fine.Fact|date=June 2007

Although the company ‘s employees participated in an “ I ‘m proud of the DC-10 ” run, McDonnell Douglas portions fell more than 20 % following the clang of Flight 191. The DC-10 itself had a bad repute, but ironically it was frequently caused by hapless care processs, and non design defect. In 1997 the McDonnell Douglas company was taken over by its challenger, Boeing, which moved its corporate central office from Seattle to Chicago.

Despite the safety concerns, the DC-10 went on to outsell its closest rival, the Lockheed L-1011, by about 2 to 1. This was due to the L-1011 ‘s launch being delayed and the DC-10 holding a greater pick of engines ( the L-1011 was merely available with Rolls-Royce engines, while the DC-10 could be ordered with General Electric or Pratt & A ; Whitney engines ) .