FLAMINGO, FL, USA
N169BH
Agusta A109A II
The No. 2 engine lost oil pressure in flight and the pilot shut it down. About 2 minutes later, after the pilot turned to a landing area, the transmission chip detector light illuminated. While making a precautionary landing in an unlit parking lot the pilot had to pull up to clear trees and touched down about half way across the parking lot. While attempting to stop the helicopter encountered wet grass and skidded into a wooded area. Post crash examination of the No. 2 engine showed the No. 8 bearing oil scavenge line was blocked by carbon and the engine oil had been pushed through a seal into the gas producing section of the engine. The metal on the transmission chip detector plugs came from the free wheeling unit washers which had worn.
On September 6, 1996, about 0413 eastern daylight time, an Agusta A109A II, N169BH, registered to and operated by Biscayne Helicopters, Inc., as a Title 14 CFR Part 91 positioning flight, collided with trees while making a precautionary landing following failure of one engine, at Flamingo, Florida. Visual meteorological conditions prevailed at the time and a visual flight rules flight plan was filed. The helicopter received substantial damage and the airline transport-rated pilot and two flight nurses were not injured. The flight originated from Miami, Florida, the same day, about 0350. The pilot stated this was a positioning flight from Miami to Key West, Florida, to pick up a patient for an air ambulance flight. While in cruise flight at 2,500 feet, about 10 miles southwest of Flamingo, Florida, the No. 2 engine turbine out temperature began to rise. Shortly after this the oil pressure for this engine dropped to 0. He shut down the engine and turned toward the Flamingo visitors area of Everglades National Park, for a precautionary landing. The helicopter would not hold altitude. About 2 minutes after shutting down the No. 2 engine, the main transmission chip master caution light illuminated. He attempted to extinguish the light twice by using the chip fuzz burner. The light continued to illuminate. He arrived over the Flamingo Visitors Center parking lot at 1,000 feet altitude. It was extremely dark with very few ground lights. As he approached the parking area from west to east, he was using the helicopter's spot light to illuminate the area. He observed trees in his path and pulled up to fly over them, using all available power. The low rotor speed warning horn sounded and the aircraft began to vibrate. He touched down at between 50 and 60 knots, in the parking area, in a level attitude. While braking to stop, the helicopter encountered an area of wet grass and began to skid. Before he could stop the forward momentum, the helicopter collided with trees on the east side of the parking lot. Postcrash examination of the No. 2 engine showed the engine oil tank was empty and that there was no evidence of a oil leak from the engine. The tailboom, just aft of the No. 2 engine exhaust had a slight oil film on it. Teardown examination of the No. 2 engine showed the engine rotated normally and all rotating wheels were in place. There was a slight puddling of oil inside the gas producer support and the first and second stage gas producer wheels were oil soaked. The No. 8 bearing turned freely and a large piece of carbon was obstructing the No. 8 bearing oil scavenge pump pick up tube. Oil had bypassed through the unworn No. 8 bearing labyrinth seal into the engine gas producer section. See the Allison On Site Investigation Report. Examination of the transmission showed that the transmission chip detector light was still illuminated after the accident. Operation of the fuzz burner one time extinguished the light. Examination of the chip detector plugs showed they had slight metal contamination. Teardown examination of the transmission showed no evidence of mechanical failure or malfunction of the transmission. A slight amount of metal material was found in the bottom of the transmission and the free wheel unit washers were found to be worn. The manufacturer reported this to be from normal wear. See the attached Augusta report. Metallurgical examination of the metal fuzz from the main transmission chip detector plugs and the metal material found in the bottom of the main transmission was conducted by the NTSB Materials Laboratory, Washington, D.C. The metal on the chip detectors and in the bottom of the transmission case was consistent with metal from the worn free wheel unit washers. See the attached NTSB Materials Laboratory Report. The pilot reported he was unable to maintain altitude after shutting down the No. 2 engine and that he could only maintain 95-96% of main rotor rpm. Examination of the No.1 engine showed the bleed line from the engine scroll to the heater valve was found to not have a sealing "O" ring installed. Manufacturer representatives reviewed the last engine power check documentation and found it had been plotted incorrectly. Re-plotting of the power check using the recorded numbers showed the engine was producing 3 % below minimum required power. They attributed this to the bleed air leak and improper engine rigging, which they stated was the cause for failure to maintain 100 % main rotor rpm. See the attached Agusta report.
The pilot being unable to stop the helicopter after encounter wet grass after making a precautionary landing in an unlit parking lot following loss of power in one engine and illumination of a transmission chip detector light.
Source: NTSB Aviation Accident Database
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