Marines: Helicopter Engine to Blame
%mlink(STRY:; PHOTO:; AUDIO:%)
SAN DIEGO (AP) _ Fine, powdery sand damaged a helicopter engine compressor and caused it to stall repeatedly in the days before the Marine Corps aircraft crashed Jan. 20 in Afghanistan, investigators said Tuesday.
Mechanics had taken steps to fix the compressor on the CH-53E Super Stallion, but they lacked the equipment to fully test it and were unaware of the importance of doing so, said Col. Stuart Knoll of Marine Air Group 16 at Miramar Air Station in San Diego, where the helicopter was based.
Two Marines were killed in the crash outside Kabul, Afghanistan’s capital.
The helicopter, loaded with water, sandbags and other supplies, weighed between 65,000 pounds and 67,000 pounds at takeoff, close to its maximum capacity of 69,750 pounds.
``They were operating at over 9,000 feet. They were very heavy. And sometimes when you’re operating at the extremes of the envelope of an aircraft, you can wind up getting compressor stalls,″ Knoll said.
The report indicated the engine compressor stalled in December and again on Jan. 16 and 17. An adjustment was made and the aircraft flew well during a test two days before the crash.
The wrecked helicopter was destroyed to keep it from being scavenged by enemy forces so investigators couldn’t examine the failed engine.
Sand in Afghanistan is far finer than the pebbly sand found at bases in California, investigators said. Mechanics were finding that it was getting past filters and wearing at blades in the engine compressor, which funnels air into the engine and provides thrust.
Investigators said recommendations made in light of the crash include revising maintenance manuals to stress the importance of proper testing of a compressor after such an adjustment. The Marine Corps is also testing a titanium-coated engine which may better resist sand-erosion.