CABAZON, CA, USA
N214MM
ENSTROM F28C
THE PILOT SAID THE HELICOPTER HAD JUST LEVELED OFF IN CRUISE WHEN IT MADE AN UNCOMMANDED LEFT YAW ACCOMPANIED BY AN ENGINE OVERSPEED. THE PILOT ENTERED AN AUTOROTATION, DIAGNOSING THE PROBLEM AS A LOSS OF POWER THROUGH THE DRIVE TRAIN. DURING THE AUTOROTATION, HE ATTEMPTED TO 'REJOIN' THE NEEDLES, BUT WAS ONLY SUCCESSFUL IN INCREASING ENGINE RPM. AS HE APPROACHED HIS PLANNED TOUCHDOWN POINT, HE TURNED ON THE LANDING LIGHT WHICH ILLUMINATED UTILITY WIRES THAT HE HAD NOT SEEN PREVIOUSLY. HE MADE A CYCLIC CLIMB OVER THE WIRES, BUT DID NOT HAVE SUFFICIENT AIRSPEED, ALTITUDE, OR MAIN ROTOR RPM REMAINING TO CUSHION THE TOUCHDOWN. SUBSEQUENT POSTACCIDENT TEARDOWNS AND INSPECTIONS REVEALED NO MECHANICAL ABNORMALITIES.
On December 10, 1994, at 1835 hours Pacific standard time, an Enstrom F28C, N214MM, sustained substantial damage during an emergency autorotative landing at Cabazon, California. The aircraft was owned by Skyline Aviation and was conducting a ferry flight. Visual meteorological conditions were prevalent at the time and no flight plan had been filed. Neither the certificated commercial pilot nor his pilot rated passenger was injured. The flight originated from an off-airport location in Cabazon at 1830 on the day of the accident. The pilot reported that the flight took off eastbound from Cabazon near the Interstate 10 freeway and had just leveled off at 1,100 feet msl and 70-80 mph when the nose of the aircraft made an uncommanded 90-degree left yaw accompanied by an engine overspeed. He stated that the nose yawed to a heading of 360 degrees while the aircraft continued to travel in an easterly direction across the ground. He entered an autorotation and then diagnosed the problem as a loss of power through the drive train. During the autorotation, he attempted to "rejoin" the needles, but was only successful in increasing engine rpm. Looking for a suitable forced landing area through the darkness, the pilot selected a nearby road that ran parallel to the freeway. As he approached his planned touchdown point, he turned on the landing light which illuminated wires in front of him that he had not been able to see previously. At approximately 100 feet agl, he made a successful cyclic climb over the wires, but as a result, he did not have sufficient airspeed, altitude, or main rotor rpm remaining to cushion his touchdown. The aircraft landed and the left skid collapsed which allowed the aircraft to roll onto its left side. The landing sequence resulted in structural damage to the fuselage. After landing, the pilot shut down the aircraft. Both pilots were able to exit the aircraft unassisted. A postaccident inspection of the aircraft was conducted by a representative of the helicopter manufacturer supervised by a Federal Aviation Administration (FAA) airworthiness inspector. No abnormalities were noted during the inspection; however, the inspectors were unable at that time to make an accurate assessment of the condition of the clutch. As a result, the clutch was removed and transported to the component manufacturer for further inspection. The manufacturer performed a teardown inspection under the supervision of the FAA principal maintenance inspector. No abnormalities were identified as a result of that inspection.
AN UNKNOWN EVENT (PRESUMABLY A COMPONENT/SYSTEM FAILURE) THAT RESULTED IN LOSS OF DRIVE TRAIN POWER TO THE MAIN ROTOR SYSTEM. FACTORS RELATED TO THE ACCIDENT WERE: DARKNESS AND THE OBSTRUCTION (TRANSMISSION LINE) IN THE EMERGENCY LANDING AREA.
Source: NTSB Aviation Accident Database
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