NTSB Identification: MIA04LA122.
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Accident occurred Tuesday, August 24, 2004 in West Palm Beach, FL
Probable Cause Approval Date: 09/13/2005
Aircraft: Robinson R-22, registration: N4062X
Injuries: 2 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

According to the flight instructor, the student pilot was practicing autorotations with the instructor at an indicated altitude from about 1,500 to 500 feet. The flight instructor decided to fly back to their departure airport, and while doing so the flight instructor idled the helicopter engine to simulate an engine out for the student pilot. When the student pilot went to recover from the simulated engine out, the helicopter engine did not respond to any power inputs. The flight instructor heard a low RPM horn, and took over the flight controls of the helicopter. The instructor proceeded to re-enter autorotation, flared, leveled the helicopter, and landed in an uneven field. The helicopter came to rest on its side. The helicopter engine was removed from the airframe and taken to a certified engine overhaul facility with NTSB and FAA oversight. The engine operated through several parameters, engine start, magneto check, and a series of several rapid throttle advancements from idle, to full engine power. No abnormalities were noted with the test. A differential compression check was conducted and the following compressions were recorded: Cylinder one, 15/80 PSI, cylinder two, 15/80 PSI, cylinder three, 20/80 PSI, cylinder four, 15/80 PSI. The cylinders were removed, and sent to ECI, Engine Components Inc., for further examination of the pistons and cylinders, with FAA oversight. Pistons, pistons pins, and combustion chambers of all four cylinders displayed discoloration, consistent with of high engine temperature operation.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The partial loss of engine power due to low cylinder compression during recovery from a practice autorotation resulting in a hard landing and damage to the helicopter.

Full narrative available

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