Aviation Accident Summaries

Aviation Accident Summary MIA97LA103

CULLMAN, AL, USA

Aircraft #1

N818D

Hughes TH-55

Analysis

The flight instructor and student pilot remained in closed traffic in order to perform practice maneuvers and emergency procedure training to include autorotations. Witnesses saw the helicopter take off to the west and turn immediately to the right, climb to an altitude of 30 feet above ground level (AGL), and attain an estimated forward airspeed of 20 to 30 knots. The helicopter was then observed in a descent and disappear out of view before the witnesses heard the sound of impact with the ground. Several of the witnesses stated that just prior to impact they heard what sounded like the engine overspeed, and then cut off. The helicopter landed near a telephone pole and support lines. There was no evidence found to indicate that the helicopter contacted the pole or the lines. According to the first people to arrive at the crash site, the student pilot did not know what had happened. The CFI said, 'we had been flying for about an hour. We'd finished our training and were heading back with...[the student] on the controls, when the engine quit. I said I've got it and took the controls, but we were too low, with no time to recover, and crashed.' Examination of the wreckage revealed that the main and tail rotor RPM was low at impact,' because the rotor blades showed little damage. In addition, the engine and airframe examinations revealed no discrepancies. Several attempts were made to talk to the CFI at the hospital to get his factual account of the accident, but all attempts to interview him were unsuccessful. The NTSB Form 6120.1/2, was returned without a statement from the CFI.

Factual Information

On March 28, 1997, about 1645 central standard time, a Hughes TH-55 helicopter, N818D, registered to a private owner, crashed while maneuvering at a low altitude near Cullman, Alabama. Visual meteorological conditions prevailed at the time and no flight plan was filed for the Title 14 CFR Part 91 local instructional flight. The commercial-rated pilot/certified flight instructor (CFI) and student pilot received serious injuries. The helicopter was substantially damaged. The flight originated about 1 hour before the accident. The flight had remained in closed traffic at Folsom Field, in order for the pilots to perform practice maneuvers and emergency procedure training, to include autorotations. Witnesses saw the helicopter takeoff to the west, and turn immediately to the right, climb to an altitude of 30 feet above ground level (AGL), and attain an estimated forward airspeed of 20 to 30 knots. The helicopter was observed in an almost vertical descent, and disappear out of view of the witnesses, before they heard the sound of impact with the ground. One of the witnesses stated that just prior to impact, "...I heard what sounded like the helicopter doing a hovering autorotation, the engine sounded like it over speeded then cut...." Other witnesses also said they had heard what sounded like an overspeed before impact. According to investigators that were at the crash site, ground scars indicated that the helicopter impacted on heading of 040 degrees, with little to no forward movement. The helicopter landed near a telephone pole and support lines. There was no evidence found to indicate that the helicopter contacted the pole or the lines. The first people to arrive at the crash site said that both pilots were alive, and the student pilot said he did not know what had happened. The CFI said, "we had been flying for about an hour. We'd finished our training and were heading back with...[the student] on the controls, when the engine quit. I said I've got it and took the controls, but we were too low, with no time to recover, and crashed." According to the FAA inspector's statement, there was evidence found at the crash site "indicating low main and tail rotor RPM at impact," because the rotor blades showed little damage. In addition, the engine examination revealed no discrepancies. The FAA concluded that "the engine was running at impact." The helicopter examination revealed control continuity on all flight controls and no discrepancies were found with the helicopter. Several attempts were made to talk to the CFI at the hospital to get his factual account of the accident, but all attempts to interview him were unsuccessful. The NTSB Form 6120.1/2, was returned without a statement from the CFI.

Probable Cause and Findings

a loss of engine power for undetermined reasons and the pilot-in-command's failure to maintain control of the helicopter. Factors in this accident were: an improper autorotation as a result of improper collective use and resulting failure to maintain main rotor rpm.

 

Source: NTSB Aviation Accident Database

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