LONG BEACH, CA, USA
N7234Y
Revolution MINI-500
After taking off, the helicopter had climbed about 250 to 300 feet, when the engine abruptly lost power. The pilot attempted an autorotation, but said he was able to maintain only 80 percent rotor rpm, which was insufficient to prevent a hard landing. The pilot reported that the main rotor low pitch stop had recently been changed from -1.8 degree to -0.5 degree, as recommended by a factory representative. Also, the pilot stated that he was aware of a phenomenon called 'cold-freeze' (engine seizure without over temp) that (according to him) had occurred with other engines of this make/modle. He believed there was a possible engine seizure and that reduced settings of the rotor low pitch stops could have resulted in low rotor rpm. No preimpact mechanical problem was found that would have resulted in loss of engine power.
On October 26, 1997, at 1233 hours Pacific standard time, a Revolution Mini-500 experimental helicopter, N7234Y, was destroyed and the commercial pilot seriously injured when it impacted terrain following takeoff at Daugherty Field, Long Beach, California. The aircraft had completed one circuit of the helicopter traffic pattern and landed on Helo Pad 3. It was then cleared for a second circuit of the helicopter traffic pattern. The pilot stated that on the second takeoff, the engine quit abruptly at an altitude of 250-300 feet agl. He then attempted an autorotation, but could get only 80 percent rotor rpm which was insufficient to prevent a hard touchdown. (The pilot stated in his report that he felt this was due to a recent change in the main rotor low pitch stop from -1.8 deg. to -0.5 deg. which had been recommended by a factory representative.) The pilot also stated that he was aware of a phenomenon called "cold-freeze" (engine seizure without over temp) that had happened several times with the Rotax engine. He felt that a possible engine seizure, combined with the change in the rotor low pitch stop, were contributing factors to the accident rather than fuel starvation or mechanical malfunction of the helicopter.
loss of engine power and low rotor rpm for undeterminted reasons. The factory representative's recommendation to reduce the main rotor low pitch stop (from -1.8 degree to -0.5 degree) may have been a related factor.
Source: NTSB Aviation Accident Database
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