May 25, 1979, O’Hare International Airport, Chicago, Illinois. Flight 191, an American Airlines DC-10 headed for Los Angeles, was cleared for takeoff at 2:59 p.m. Three minutes later, Flight 191 started down runway 32R. Just before the nose lifted off the ground the No. 1 engine and pylon came off the aircraft, rolled over the top of the wing, and fell to the ground. Despite losing one of its three engines, the plane lifted off about 6,000 feet down the runway, climbed out in a wings-level attitude, reaching an altitude of about 300 feet. Soon the aircraft began to turn and roll to the left, the nose pitched down, and the aircraft began a rapid descent. It crashed in an open field and trailer park over a mile northwest of the departure end of the runway.
The aircraft was destroyed on impact, instantly killing all 271 passengers and the flight crew; two more on the ground also lost their lives. Before the plane crashes of September 11, Flight 191 was the deadliest air accident in U.S. history.
The National Transportation Safety Board (NTSB) concluded that the aircraft rolled because the left wing slats (that provide lift) retracted, causing the lift to be greatly reduced on the left wing compared to the right wing. The reasons for the uncommanded retraction of the left wing slats were traced back to the installation of the left wing mounted engine nearly two months before the accident.
The maintenance manual for a modern jet airliner might be 60,000 to 100,000 pages long. Including component manuals for the parts on the aircraft, there can be millions of pages in maintenance manuals instructing technicians how to perform maintenance and repair on a modern jetliner. These manuals dictate how the work is to be performed. If an aircraft presents a problem, the technician has a fault isolation manual to help diagnose the cause. Once the technician determines the cause, the technician has a removal and installation procedure for how to remove the bad part and install the new one.
The Federal Aviation Administration (FAA) is serious about technicians following the rules. Federal Aviation Regulation 43.13, applicable to all aircraft maintenance technicians, reads in part as follows:
(a) Each person performing maintenance […] shall use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual…
For airplane maintenance, the manufacturer generally determines how the work is to be performed. The airline technician is expected to follow the rules. This is the duty to follow a procedural rule. If the tire is flat, the manual dictates how to change the tire. If the engine is not working, the manual describes, in exact detail, how to change the engine.
In the case of Flight 191, the plane’s left engine was changed 55 days before the catastrophic loss of the aircraft. In their investigation, the NTSB found that American Airlines maintenance technicians had developed an alternative means for removing the engine, based in part on perceived time constraints at the maintenance facility. Tragically, this alternate method physically stressed the pylon mounts on the wing, inadvertently fracturing the attachment bolts. As the aircraft rolled down the runway, the forces of engine thrust and the weight of the engine itself caused the engine to separate from the aircraft. The result was the nation’s worst single aviation accident, traceable to a simple failure to follow procedural rules.
There are times in life, and particularly in high-risk or high-consequence industries, where the system designers expend enormous resources to build an optimal procedure. If left to the wisdom of each individual performing safety critical tasks, the risk is too great that one or more individuals might design an inefficient or even hazardous procedure.
Aviation, as an industry, is extremely procedurally rooted. Pilots are told how to fly the aircraft. Technicians are told how to maintain it. The stakes are just too high to leave the procedures to individual choice. Engineers have time and resources to work out procedures, to anticipate possible mistakes, and to work to mitigate their likelihood or impact before they occur. One minor alteration to the procedure, well intended or not, might mean the difference between profitability and loss. One slight alteration to the procedure might mean the difference between success and catastrophic failure.
Nearly every employer imposes the duty to follow a procedural rule on its employees. Many of us work in environments where lessons learned over many years have worked their way into the protocols of how the work is to be performed. For an employee, these procedures impose the duty to follow a procedural rule. The employee follows the procedure; the business organization owns the outcome. In complex environments it will be many employees working together, all doing their part to help the system meet its goals.
Under the duty to follow a procedural rule, we create a system of shared accountability. If we are the system designers, we are accountable for the outcome; the employee within the system is accountable for compliance. When things go bad, we learn together. We learn why the systems did not work, or we learn why the procedure was not followed. It is here that we attempt to understand, in relevant terms, why the breach has occurred. Did our employee inadvertently make a mistake in attempting to follow the procedure? Did our employee knowingly deviate, but under the belief they were in a good, safe place? Did our employee deviate from procedure because there was some other legitimate, compelling interest to be satisfied?
It is in the duty to follow a procedural rule, where console, coach, and punish, applied to the human error, at-risk behavior, and reckless behavior is applicable. It is here we must create an open learning culture between those who create the procedures and those whose job it is to follow them.
Excerpted from Whack-a-Mole by David Marx. Click here for more information on the book.