AVALON, CA, USA
N3593S
Aerospatiale AS-350D
The helicopter collided with terrain following a loss of engine power while maneuvering at low level on a sightseeing flight. As the helicopter passed about 250 feet above ground level (agl) over a ridgeline, the pilot began a descending and decelerating right turn to observe a herd of buffalo. About midway down the ridge, the low rotor rpm warning horn sounded. The pilot lowered collective and the horn stayed on. He noted the rotor speed was down between 300 and 320 rpm and concluded that he would have to make an immediate landing. The helicopter landed downslope at an estimated 10 to 15 mph, and the tail rotor struck the ground first. The helicopter pitched forward, continued to slide down the hill, collided with trees, and rolled onto its right side. An 80-psi check of the pneumatic system revealed two calibrated leaks and an additional leak. The attachment fitting for the P3 air accumulator on the governor pressure (Pg) line was 3/4 of a turn loose. The engine was removed and shipped to the manufacturer for testing. Several discrepancies due to damaged hardware were corrected during preparation for the test run. The engine was placed in a test stand and started normally. The engine completed a test protocol with no discrepancies noted. The P3 accumulator fitting was loosened and the engine immediately went to flight idle. The engine would not accelerate above idle power with the P3 accumulator fitting loose. Once the fitting was loosened less than finger tight, it continued to loosen to 3/4 to a full turn loose.
HISTORY OF FLIGHT On December 28, 1999, about 1050 hours Pacific standard time, an Aerospatiale AS-350D helicopter, N3593S, collided with terrain following a loss of engine power while maneuvering at low level on a sight-seeing flight over the interior of Santa Catalina Island, Avalon, California. Island Express Helicopters, Inc., was operating the helicopter under the provisions of 14 CFR Part 91 as a for-hire sightseeing flight. The airline transport pilot and five passengers sustained minor injuries; one passenger sustained serious injuries. The helicopter was destroyed. The local flight departed a helipad near Avalon harbor about 1030. Visual meteorological conditions prevailed and a company flight plan had been filed. The accident site coordinates were 33 degrees 24.98 minutes north latitude 118 degrees 27.924 minutes west longitude. The pilot supplied a written statement, and the operator's Federal Aviation Administration (FAA) Principle Operations Inspector (POI) also interviewed him. The pilot stated that he picked up passengers from a cruise ship at Pebbly Beach for a 30-minute flight over the island. Approximately 20 minutes into the flight, the pilot proceeded inland from the Two Harbors area. As the helicopter passed over a ridgeline, the pilot spotted a herd of buffalo in a valley near some dried up watering ponds. He began a descending and decelerating right turn and crossed the ridgeline approximately 250 feet above ground level (agl) at 60 to 70 mph. About midway down the ridge, the pilot and passengers heard the low rotor rpm warning horn. The pilot lowered collective and the horn stayed on. He noted the rotor speed was down between 300 and 320 rpm. He confirmed that the fuel flow control lever was down in the detent in the on (flight) position. The pilot concluded that he would have to make an immediate landing. As the helicopter descended into the terrain, he applied collective and flared to cushion the landing. He stated that the helicopter landed downslope at an estimated 10 to 15 mph, and the tail rotor struck the ground first. The helicopter pitched forward and the nose struck the ground. The helicopter continued to slide down the hill, collided with trees, and rolled onto its right side. The passengers in the dual seat to the left of the pilot were now dangling above him. Everyone except a young male passenger in the back right rear seat was able to exit the helicopter. The young man's leg was pinned under the wreckage. It took approximately 30 minutes to facilitate his exit from the wreckage. The passengers reported that just after they heard the horn sound, they felt the helicopter shake and the pilot report that they were going down. One passenger reported that the float mechanism detached uphill from the accident site, and he dragged it back to the wreckage to help identify their location. When the helicopter did not return at the scheduled time, the operator notified local authorities and a search was initiated. The accident site was located about 1 hour 20 minutes after the accident. PERSONNEL INFORMATION A review of FAA airman records revealed the pilot held an airline transport pilot certificate with a helicopter rating. A class two medical with the limitation, must have glasses for near vision, was issued on February 3, 1999. The pilot stated his total flight time was 11,122 hours with 9,696 hours in rotorcraft. He had 3,930 in this make and model; 119 hours were logged in the last 90 days. AIRCRAFT INFORMATION The helicopter was an Aerospatiale AS-350D, serial number 1063. A review of the airplane's logbooks revealed a total airframe time of 14,085 hours. An annual inspection was completed on September 22, 1999, at a total time of 13,793.2 hours. A 100-hour inspection was completed on December 9, 1999, at a total time of 14,073 hours, and a hobbs meter time of 2,998.2 hours; the revenue meter read 9,126.5. A maintenance log sheet contained a section for the daily flight record, which recorded a revenue meter reading of 9,148.1 and a hobbs meter reading of 3,010.3 on December 23, 1999. The revenue meter read 9,165.1 at the accident site. A Honeywell LTS-101-600A3 engine, serial number LE-43496CE was installed on the helicopter. Total time on the engine at the 100-hour inspection was 6,392 hours. The maintenance manual for the engine detailed inspection requirements. A preflight inspection was to be completed before the first flight of the day and a daily inspection was to be completed after the last flight of the day. The manual scheduled periodic inspections, which included 50-hour and 100-hour inspections. Daily inspection requirements included checking all wiring, fuel, oil, and air tubing for leakage, chafing, and security of mounting. Another requirement was to check the engine and accessories for leakage, cracks, damage, and security of mounting. The daily inspection also required a daily rinse of the compressor section with fresh water. The operator had a night crew that completed the daily checks and a day crew that did the fresh water rinse and preflight checks. The operator was performing these procedures, but did not maintain a log to indicate completion of them. The director of maintenance indicated that following the daily rinse mechanics checked the tightness of fittings with a wrench. The helicopter was equipped with fittings, which required examination during the 100-hour inspection. The maintenance manual directed maintenance personnel to disconnect and remove the Pg, Pr, and Py pneumatic lines from the fuel control, and the Pg and Py pneumatic lines from the PT governor. It said to remove the corresponding pneumatic line fittings from the fuel control and governor. It gave detailed instructions for inspecting and maintaining the fittings prior to reinstallation. METEOROLOGICAL INFORMATION A routine aviation weather report (METAR) for Avalon was not available. The nearest reporting point was Long Beach, California. The METAR issued at 1056 PST stated: clouds few at 10,000 feet, scattered at 15,000 feet; visibility 10 miles; winds from 330 degrees at 5 knots; temperature 73 degrees Fahrenheit; dew point 32 degrees Fahrenheit; and altimeter 30.25 inHg. WRECKAGE AND IMPACT INFORMATION The accident site was on the downslope side of a finger of a ridgeline. The helicopter came to rest on its right side in the bottom of a gully 200 feet from the first identified point of contact (IPC). The debris path was along a magnetic bearing of 100 degrees, and the following references to pieces of wreckage are measured from the IPC and left or right of the debris path centerline. A piece of landing gear skid was abeam the IPC and 10 feet right. The tail rotor drive shaft was 58 feet from the IPC and 21 feet left. The tail rotor drive shaft fractured and separated into several pieces, and the fracture surfaces were angular and uneven. The main rotor blades fractured about 3 feet from the hub; the remainder of one blade separated and came to rest 60 feet right of the main wreckage. TESTS AND RESEARCH The helicopter was examined at Aircraft Recovery Services, Compton, California, on January 4, 2000. During examination of the wreckage, an 80-psi check of the pneumatic system revealed two calibrated leaks and an additional leak. The attachment fitting for the P3 air accumulator on the governor pressure (Pg) line was 3/4 of a turn loose. The engine was removed and shipped to the manufacturer for testing. Several discrepancies due to damaged hardware were corrected during preparation for the test run. A complete report of the test protocol is attached to this report. Highlights of the report are reflected in the following paragraphs. The engine was placed in a test stand and started normally. The engine completed a test protocol with no discrepancies noted. The P3 accumulator fitting was loosened and the engine immediately went to flight idle. The engine would not accelerate above idle power with the P3 accumulator fitting loose. Once the fitting was loosened less than finger tight, it continued to loosen to 3/4 to a full turn loose. ADDITIONAL INFORMATION The wreckage was released to the owner's representative.
A loose pneumatic fitting caused the engine to go to flight idle power at a low altitude, which resulted in a forced landing in hilly terrain.
Source: NTSB Aviation Accident Database
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