ISTOCK/ALIAKSANDR BUKATSICH


ACCIDENT RECOVERY


By David Jack Kenny


Quick Thinking Immediate, decisive pilot action averts a catastrophic in-flight failure.


H


ELICOPTERS ARE PRIZED FOR THEIR ABILITY TO FLY VERY SLOWLY, right down to a hover. But the mechanical components enabling this ability operate within very narrow tolerances. Imbalances or mechanical slop in rapidly rotating assemblies can propagate into complete failure in minutes.


Characteristically operating aircraft at low altitudes with a very limited gliding range, helicopter pilots must rely not only on their training and airmanship but their gut-level awareness, as well, to get ailing machines onto the ground before they fly apart.


The Accident


On the morning of Dec. 7, 2019, VH-OXI, a US Army– surplus UH-1H, was dispatched from Wauchope, New South Wales (NSW), Australia, to conduct water drops on a bushfire near the Crawford River. The aircraft was equipped with a 1,200 l (317 gal.) bucket on a 45.72 m (150 ft.) line. The ground-based air attack crew directed the pilot to the river dip site and then the drop site. The first drop was uneventful. But upon returning to


the river, just before dipping the bucket, the pilot heard what he described as a “burring noise” accompanied by a “buzzing” vibration through the airframe. He immedi- ately abandoned the dip.


80 ROTOR MARCH 2021


As he began to fly out of the hover over the river, the noise and vibration returned, intensifying as the collec- tive was raised. He dropped the bucket and radioed the air attack crew he’d be landing immediately. Increasing levels of noise and vibration on the way to an unconfined landing site convinced him the helicopter’s condition was deteriorating, so he diverted to a small clearing where he’d have to bring the ship to a hover to land. Slowing to a 10 ft. hover, the helicopter began yawing right and didn’t respond to left pedal. Closing the throttle to idle failed to slow the rotation, so the pilot “dumped the collective,” and the helicopter landed hard about 180 degrees opposite its initial heading.


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