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Once Again, Design of DC-10 Comes Under Scrutiny

July 21, 1989

WASHINGTON (AP) _ The crash of a United wide-bodied jet in Sioux City, Iowa, demonstrates a problem already highlighted in two other major DC-10 accidents: loss of pilot control with damage to flight control systems.

Other incidents prior to Wednesday’s DC-10 crash, in which 119 people were either dead or missing, have a common thread in the loss of pilot control after a failure that would not ordinarily affect flight controls, such as loss of an engine or a cargo door.

Some of the cases did not cause heavy loss of life, but each has added to concern among government and aviation authorities over design of the DC-10 which the government grounded for more than a month in 1979.

A McDonnell Douglas spokesman said Thursday the out-of-production DC-10 is ″as fit as any other″ airliner and has flown 745 million passengers safely more than 7 billion miles.

Douglas officials declined to comment on evidence that the plane’s hydraulic systems failed in the Sioux City crash, except to say that the manufacturer was cooperating in the federal investigation to determine cause.

But spokesman Don Hanson said DC-10s have three independent hydraulic systems routed through the aircraft so they are as far apart from each other as possible.

″The airplane is so designed that the loss of any one hydraulic system will not affect control of the airplane,″ Hanson said. Even if two systems failed, a pilot still should be able to land safely, he said, and the system has an additional air-driven backup for one of the systems.

Although investigators were looking at explosive failure of the plane’s tail engine as the initial incident in the crash of United Flight 232 in Sioux City, they also were concerned about apparent collapse of the plane’s hydraulic systems as its pilot was attempting an emergency landing on a Denver-Philadelphia flight.

The hydraulic systems link the pilot with wing flaps, tail elevators, rudders, brakes, and other devices that guide the airliner in takeoff, during flight, in landing and on the runway.

Federal Aviation Administration authorities said the DC-10′s pilot first reported ″uncontained engine failure,″ which means parts shot out of the engine, possibly damaging other systems and causing what the pilot later described as ″complete hydraulic failure.″

In 1974, loss of a cargo door caused decompression in a Turkish Airlines DC-10 over France. The plane’s floor buckled, snapping control cables, and the airliner went out of control, killing 346 people. At least two previous incidents had pointed to a cargo door problem, but the problem was not ordered corrected by the FAA until after the Turkish crash.

On May 25, 1979, in Chicago, the engine of an American Airlines DC-10 broke loose and catapulted over the wing during takeoff, breaking hydraulic cables and causing a crash that killed 275 people. Investigators blamed faulty maintenance but also recommended a design review.

McDonnell Douglas spokesman David Eastman said he knew of only one design change that had occurred in the DC-10 since the Chicago crash, involving instrumentation that would warn the pilot when wing slats were improperly positioned.

The two incidents and the latest crash point to serious problems with design of the DC-10, said John Galipault of the Aviation Safety Institute, a nonprofit group that pushes for safer planes.

He said the common element in several DC-10 crashes has been loss of the pilot’s ability to control the aircraft after a catastrophic failure in a single system.

″When that happens, the pilot becomes a passenger,″ he said. ″It reinforces my concern about the airplane. It’s too bad, but it has a terrible safety record.″

According to a National Transportation Safety Board analysis of the Chicago crash, the DC-10 has three hydraulic systems, each powered by two engine- driven pumps. It also has two electric auxiliary pumps. Further backup is provided by an air-driven system which includes a propeller dependent only upon movement of the aircraft through the air.

Problems with the pumps’ design was found early in the 19-year-old history of the DC-10 and corrected, the board said.

But as accidents occurred, controversy over effectiveness of the DC-10′s hydraulic system and its backups increased.

In 1982, McDonnell Douglas discussed possible design changes after an Air Florida DC-10 in Miami aborted its takeoff without injuries after a malfunctioning engine hurled fan blades into the wing and caused hydraulic problems.

In July 1974, failure in a wing engine on a DC-10 en route from Miami to Los Angeles caused loss of hydraulic fluid because of damage to the wing.

After a March 1976 accident in which a flock of birds flew into a DC-10 rear engine, causing it to disintegrate, the safety board concluded that the engine could not safely tolerate such a massive ingestion of foreign objects.

Airliners can fly with one engine out, but there is concern with the DC-10 that failure of any engine which involves it coming apart endangers the hydraulic system.

Other wide-bodied jets, such as the Boeing 747, have differently configured hydraulic and engine systems, also with built-in redundant backups. A Boeing spokesman, David Jimenez, declined to discuss any differences between the aircrafts, saying it would be ″like comparing apples and oranges.″

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