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Choppers Won’t Be Grounded, But Flying is Restricted

September 9, 1986

WASHINGTON (AP) _ The Army has concluded it does not have to ground two aging helicopter models that have suffered a rare pattern of engine failures, but it has imposed special flight restrictions on them.

The flight restrictions will remain in place until the Army replaces certain engine gears in affected OH-6 and OH-58A light observation helicopters, a spokesman said Tuesday.

That replacement process will begin in January. It will take about a year to modify all 1,700 affected helicopters, at a cost of some $2 million, said Jim Wittmeyer, a spokesman for the Army’s Aviation Systems Command.

In the meantime, the Army and National Guard units that use the helicopters have been ordered to maintain a minimum altitude of 400 feet during flights; to have a fire crew standing by during engine starts, and to ban passengers from the chopper back seats.

The Army disclosed last month it had opened an air-safety investigation focusing on the two copters and would decide whether to ground them.

Lt. Col. Craig MacNab, another Army spokesman, said at the time the investigation was prompted when the Corpus Christi Army Depot in Texas found that an engine failure aboard an OH-6 last June 7 resulted when ″an internal gear of the engine failed due to fatigue.″

The engine failure on that OH-6, which was assigned to the Tennessee Army National Guard, did not result in a crash or any injuries. A subsequent review of historical records, however, determined there had been five similar failures over the past seven years.

″During the period from October 1978 through June 1986, there have been six of this type of engine failure for the OH-6 and OH-58A fleets out of approximately 2.5 million hours flown,″ the Army said on Aug. 11.

″Although the incidence of this failure is small, the Army’s primary concern is safety. Therefore, this pattern of engine failure is worth a deliberate and precautionary study followed by future action if necessary.″

MacNab said the internal gear tends to fail as the copter is turning its engine on or off.

The Army has roughly 360 OH-6 copters assigned to the National Guard; 850 OH-58A’s assigned to active-duty units, and 490 OH-58A’s assigned to the National Guard.

The two copters, dating to the late 1960′s and early 1970′s, use an engine made by the Allison Division of General Motors.

The engine went out of production in 1973 and its gears are no longer under warranty, according to the Army.

The OH-6 was made by Hughes Helicopter, which is now a subsidiary of the McDonnell Douglas Corp., while the OH-58A was made by Bell Helicopter Textron, a division of Textron Inc.

″The Army’s OH-6 and OH-58A helicopters, which have the same type engine, will not be grounded as a result of failure of an internal gear that caused engine failure,″ the service said in a prepared statement.

″Rather, it has been determined that some operational flying restrictions can afford maximum aircrew safety in the event of other failures before the gear can be replaced. These restrictions will not interfere with the training and other missions that active-duty and National Guard units accomplish with the aircraft.″

Wittmeyer said Tuesday the engine gears will be replaced by mechanics at seven Army depots during the next year.

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