• Military Menu                       

• Introduction
• Systems
• Facilities
• Agencies
• Industry
• Operations
• Countries
• Hot Documents
• News
• Reports
• Policy
• Budget
• Congress
• Links

• WMD
• Intelligence
• Homeland Security
• Space

Army restricts Black Hawk flights

by Tonya Johnson

WASHINGTON (Army News Service, May 3, 2002) - Hundreds of Black Hawk helicopters were grounded except for mission-essential flights May 1 after a potential transmission problem was discovered in one.

Approximately 960 Black Hawks in both the active Army and National Guard have been restricted, officials said, as the Army conducts an assessment to see if the problem is isolated or if other Black Hawks have a similar problem. Under the restriction, only mission-essential flights such as medical evacuation and combat are allowed.

The restriction involves the UH-60A utility helicopter, EH-60A electronic warfare version and the UH-60Q medivac chopper. The UH-60L helicopters were not affected because they have a different transmission.

The transmission problem was detected when an Army aviation unit, the 57th Medical Company, at Fort Bragg, N.C., experienced persistent low oil pressure problems with the transmission of one of its UH-60A Black Hawks.

The transmission was sent to Corpus Christi Army Depot, Texas, for repair. The part was disassembled and a cracked planetary carrier was determined as the reason for the low oil pressure. The planetary carrier, manufactured by RAF Industries, is a large plate-shaped component within the transmission that has no finite replacement life.

The Army Aviation and Missile Command, Corpus Christi Army Depot and Sikorsky, the designer of the aircraft, are investigating to find out the possible cause of the cracked carrier, officials said.

"The Black Hawk has a great performance record, and this is the first cracked planetary carrier found in 3.5 million flight hours," said Bob Hunt, Army Aviation and Missile Command spokesperson. "The Army Aviation and Missile Command, Corpus Christi Army Depot and Sikorsky are working vigorously to solve this issue. A lot of people are putting in a lot of hours to get to the bottom of this."

If a planetary carrier is cracked, stress is placed on the transmission gears and could cause internal shim damage, officials said. If pieces of the shim fall into the transmission oil sump, the transmission filter could become blocked and cause low oil pressure.

When the part doesn't function, it can't transfer engine power to the main rotor system. The rotor system could continue to operate without power allowing an autorotation landing or the failed carrier could cause a jam causing the rotor system not to work.

But Hunt said the restriction shouldn't affect Army readiness. More than 500 L series Black Hawk helicopters will be used until the Army can resolve the problem. The restrictions will also not stop Black Hawks in Afghanistan from flying combat missions, Hunt said.

There have been no Black Hawk accidents in the past due to a planetary carrier crack or failure, Hunt said. There also haven't been any major problems with the Black Hawks in years, he said. The last major maintenance problem occurred in the late 1980s when there was a problem with the aircraft stabilator.

Hunt said an update concerning the restriction will be issued within the next seven to 10 days.