Post-Accident Investigations

Cause of the Accident
Like all airline accidents, the crash of Flight 191 was investigated by the NTSB. It is the duty of the NTSB to determine the probable cause of the accident and suggest corrective measures to reduce possible reoccurrences. The

NTSB determined the probable cause of the crash was asymmetric stall and the resulting roll, of the aircraft due to the uncommanded retraction of the left wing outboard leading edge slats; in addition the failure of the stall

warning and slat disagreement indicator systems made it difficult for the crew to determine the nature of the problem. All these failures were the result of the No. 1 engine and pylon separating from the aircraft due to improper

maintenance procedures.
Through numerous simulations of the accident, the NTSB determined that it would have been possible for a flight crew to recover the airplane in a situation like that encountered by the crew of Flight 191, IF the crew had been

fully aware of the situation and IF the crew had followed a very specific course of corrective action. In the case of Flight 191, no one had ever anticipated such a complex series of failures and procedures to handle the situation

had never been developed. Also, because of the failure of the stall warning and slat disagreement indicators, it is likely that the crew was never fully aware of the situation, at least until it was to late to save the airplane. The

NTSB strongly disagreed with McDonnell Douglas’ assessment that the probability of engine detachment and subsequent system failure was extremely low for the DC-10. Finally, in the opinion of the NTSB, the crew of Flight

191 flew the aircraft in accordance with prescribed emergency procedures.
The problems which led to the crash of American Airlines Flight 191 were complex, involving the airlines, the manufacturer, and the FAA. Most of the problems involved a lack of communications at various levels and failure to

identify problems until after a disaster had occurred.
Assignment A
Read the General Information provided on the Flight 191 maintenance problem. Consider each of the following questions carefully in light of that information and write a complete and grammatically correct paragraph answering

each.
1.   Why did Flight 191 crash?
2.   Could knowledge of the maintenance problems encountered by Continental Airlines have prevented the crash of Flight 191?
3.   Considering the knowledge that pylons are frequently removed during maintenance, why was the engine-pylon clearance so small?
4.   Should McDonnell Douglas have paid more attention to American Airlines revised maintenance procedures?
5.   When the engineers at American Airlines developed the revised maintenance procedure, did they give sufficient thought to the implementation of this procedure?
6.   Why didn’t American Airlines maintenance workers report their difficulties in following the new procedures to anyone? Why didn’t someone from management or engineering check on the implementation of the new

procedures?
7.   Was McDonnell Douglas justified in considering the separation of an engine as an extremely unlikely event, and thus not analyzing the situation and developing contingency plans?
8.   The whole mechanism of FAA review of both airlines and manufacturers is based on an adversarial nature. Is this system the best, or might a team effort result in better protection of the public?
9.   Should the DC-10 design have incorporated more redundancy features in the flight control systems?
10.   Should maintenance procedures be more closely inspected? If so, how can the expected resistance of the airlines and the increased cost of such inspections be handled?
Assignment B
Choose one of the following statements, research the topic, and write a two page paper in which you explore the impact of the topic on the crash of Flight 191.
1.   American Airlines Flight 191 crashed when the Number 1 engine and pylon separated from the airplane during rotation and damaged the hydraulic systems. The pylon had been damaged while routine maintenance was

being performed using a procedure designed by American Airlines. Apparently maintenance personnel were not aware that the structure had been damaged. What types of procedures would you recommend to avoid similar

occurrences in the future?
2. The crew of Flight 191 acted properly and was not at fault. However, it is possible that the crew could have saved the aircraft had they had correct information and special training. How far should airlines go in

developing training for “rare occurrence” emergencies?
3. The most important consideration in designing a new commercial airline is increased economic efficiency. Explore the conflict between safety and economics.
4. McDonnell Douglas did not adequately consider the vulnerability of the pylon structure to damage during maintenance because the manufacturer’s maintenance procedure would not damage the pylon. How far should

the manufacturer go in exploring “every possible” scenario of improper maintenance?
5. The DC-10-10 flight control system lacked redundancy which would have allowed cross feeding of sensor information to the opposite flight control computer if one was damaged. The slats also lacked mechanical

locking mechanisms to prevent accidental retraction. Also, the manufacturer did not consider the separation of an engine likely, and therefore did not analyze what would happen if separation occurred. Explore the design and

maintenance changes which resulted from the accident investigation.
6. American Airlines developed ECO R-2693 without adequately considering the difficulties of implementation. What failures in communication affected the development of the ECO and ultimately led to the crash of

Flight 191.
Assignment C
Divide the class into small groups, no more than three to a group. Each group is to choose one of the five roles outlined below and develop a statements outlining the position represented by those in your role in the events

preceding the crash of Flight 191. Develop two statements: (1) what you think was the position of those in your role, and (2) the position that those in your role should have taken.
1. American Airlines Management: You want your airline to make as much profit as possible. You would not knowingly cut corners on safety, but you are always on the look out for methods of reducing costs. While

recognizing the importance of FAA inspections, you generally feel that the government makes your business more difficult. Your company is not against actions to improve passenger safety, but some FAA regulations seem

arbitrary and in your opinion produce little results and lots or paperwork and lost time.
2. American Airlines Engineers: Your management is always instructing you to look for ways to improve efficiency. Consequently, when you come up with a procedure which not only decreases maintenance time, but

limits the number of reconnects and increases safety you eagerly implement it. Company custom dictates that engineer due engineering, and maintenance personnel due maintenance. Thus once you develop your procedure and

transmit it to maintenance, you do not normally think about it again.
3. American Airlines Maintenance Personnel: Your job is to make any repairs to and perform regular maintenance on the companies airplanes. The procedures you follow are very specific and normally do not require you

to ask questions. Occasionally engineering provides you with new procedures designed to increase efficiency. Sometimes these procedures work, sometimes they do not. If there is a major problem engineering is informed, but

this step is usually taken as a last resort..
4. McDonnell Douglas: You are want to sell as many planes as possible. Beyond FAA requirements, the airlines are not really concerned with safety. Improved operating efficiency is what sells a plane. If a customer

damages an airplane during maintenance, there is no reason for you to publish this information. No law required publication and it was the customers fault; you do not want your airplane to be judged guilty by association.
5. FAA: Your duty is to make sure that commercial air travel is safe. It is your responsibility to protect the passenger. Unfortunately, few people a appreciate your efforts. The manufacturers and airlines consider you an

annoyance, while the public generally ignores you. At least until your regulations impede them personally. You must balance safety and economic efficiency.
Assignment D
Working in three person groups, consider the role of the FAA in the commercial airline industry. Research the charter and purpose of the FAA. Consider how the agency addresses the dual role of functioning as both a technical

and bureaucratic organization. In the United States the system is by nature adversarial, is there an alternative relationship? How do political forces effect the operation of the agency? What would happen if the agency did not

exist?
Assignment E
Working in three person groups, consider the maintenance problems associated with the crash of Flight 191. When McDonnell Douglas designed the DC-10-10, did it take routine maintenance into consideration? How could the

airplane have been improved from a maintenance standpoint? How could the engineers at American Airlines have improved ECO R-2693? How could communication between the maintenance personnel and the engineering

personnel at American Airlines have been improved?

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