NTSB Identification: LAX00LA013.
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Accident occurred Thursday, October 14, 1999 in LOS ANGELES, CA
Probable Cause Approval Date: 08/21/2001
Aircraft: Bell 206B, registration: N16889
Injuries: 3 Serious.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot turned right toward the helipad and descended at a rate of about 1,300 feet per minute until he intercepted a standard approach profile. He reported that as he increased collective pitch, the rotor rpm immediately drooped to 90 percent. The low rotor rpm horn and light came on and the pilot fully lowered the collective. He estimated that his altitude at that time was between 100 to 150 feet agl and his airspeed was about 60 knots. He declared an emergency to the air traffic control tower and turned left toward an open area between terminals 5 and 6. The pilot realized he might not have sufficient altitude to clear the terminal buildings, so he pulled collective pitch, which further decayed the rotor rpm but provided additional lift. As he descended to his intended landing point, a twin-engine turboprop airplane turned into the ramp area and he veered to the right to avoid it. He stated that he fully lowered the collective and realized that he'd have to perform a run-on landing with little or no flare. He pulled all remaining collective pitch before impacting the ground. The helicopter contacted the ground in a tail-low attitude, slid forward approximately 60 feet, and made a 180-degree turn. The right front chin bubble shattered on impact. Both landing gear skids were forced upward through the cabin. The helicopter came to rest on its belly. The pilot attempted to shut the engine off by rolling the throttle past the idle cutoff position but was not able to manipulate the throttle. He turned off the fuel shutoff valve, generators, and battery. The pilot stated that he had not experienced any problems with the helicopter prior to the accident. The engine was removed and run in a test cell. Due to a breakdown of the test cell, the engine run could not be completed. Immediately before the test cell failed, an uncommanded decrease in rpm was observed. The fuel control unit and power turbine governor were removed and bench tested. The static bench testing of the fuel control unit and power turbine governor indicated that both components were slightly out of calibration. According to Rolls Royce, the irregularities noted on the power turbine governor were consistent with a high-time governor and/or impact or vibration damage. The governor had 246.5 hours remaining before the next overhaul. The Rolls Royce investigator reported that the discrepancies noted might result in a 2 percent increase or decrease of N2 rpm with a corresponding reduction or increase of the collective lever. He stated that the fuel control discrepancies were insignificant deviations. The engine was then transported to Scottsdale, Arizona, where a complete and normal run was accomplished. During the test run, several aggressive accelerations/decelerations were conducted with no discrepancies noted. The test included: initial idle; seal run in to maximum power; five power point checks; governor droop; and a final idle setting. The engine performance met all required specifications. A copy of the performance data is appended to this file. The power turbine governor was bench tested again by Allied Signal.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot-in-command's excessive rate of descent and improper use of the collective control, which resulted in a low rotor rpm condition and inadvertent settling with power. Full narrative available
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