TAMPA, FL, USA
N35AH
AEROSPATIALE AS-350B
THE PILOT STATED HE FELT A FEEDBACK IN THE CYCLIC CONTROL AND THE CONTROLS LOCKED AS HE MADE A SHALLOW LEFT TURN AT ABOUT 800 FEET. THE HELICOPTER ENTERED A DESCENDING LEFT TURN TOWARD AN ISLAND AND THE PILOT RECEIVED INTERMITTENT HYDRAULIC SYSTEM FAILURE INDICATIONS BUT DID NOT FOLLOW MANUFACTURER'S PROCEDURES FOR HYDRAULIC SYSTEM FAILURE WHICH CALL FOR REDUCTION OF AIRSPEED TO BETWEEN 40 AND 60 KNOTS AND TURNING OFF OF THE HYDRAULIC SYSTEM. HE WAS UNABLE TO REGAIN CONTROL OF THE HELICOPTER PRIOR TO TOUCHING DOWN HARD, TAIL FIRST ON THE ISLAND. THE HELICOPTER THEN SKIDDED INTO THE WATER AND CAME TO REST. POST CRASH EXAMINATION SHOWED THE HYDRAULIC MANIFOLD AND FILTER WERE CLOGGED WITH DEBRIS FROM THE CORROSION OF THE MANIFOLD AND FILTER CAP. MANUFACTURER'S PROCEDURES REQUIRE THE FILTER AND MANIFOLD TO BE EXAMINED AT EACH 500 HOUR INSPECTION. THE HELICOPTER HAD RECEIVED A 500 HOUR INSPECTION ABOUT 6 WEEKS AND 50 FLIGHT HOURS BEFORE THE ACCIDENT.
On May 19, 1995, about 2010 eastern daylight time, an Aerospatiale AS350B, N35AH, registered to American Helicopter Specialties, Inc., crashed while making a forced landing following loss of cyclic control, at Tampa, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the commercial-rated pilot sustained serious injuries. The five passengers were not injured. The flight originated from Peter O. Knight Airport, Tampa, Florida, a short time before the accident. The pilot stated that after departure from the airport they climbed to 800 feet and flew southeast to some islands in Tampa Bay. While maneuvering over the islands in a half standard rate left hand turn he felt the cyclic control "feed back". He righted the helicopter and looked for any unusual indications. None were observed. He again initiated a left turn and again the cyclic feedback returned with the cyclic locking momentarily. The helicopter was now in a descending left turn heading for an island. He began to receive an intermittent hydraulic failure light indication and warning horn. The helicopter touched down on the island, tail first and then skidded off the island. The pilot activated the floats and the helicopter turned around several times before it landed in the water. The helicopter came to rest in the water on the right side. Postcrash examination of the helicopter by NTSB showed that continuity was established within all flight control linkages and that all separation points were typical of impact damage. All hydraulic lines were in place and had sustained no damage. The hydraulic failure warning light bulb was examined. The bulb filament was not stretched. The four flight control hydraulic actuators and hydraulic filter and manifold were removed and sent to FAA inspectors at Van Nuys, California, for testing under their supervision at Hawker Pacific, Sun Valley, California. Testing of the right lateral, fore and aft, and tailrotor actuators showed each operated within normal specifications. Examination of the left lateral actuator showed it operated out of normal specifications and according to Hawker Pacific personnel would have operated erratically on the helicopter. Testing of the hydraulic manifold and filter assembly showed the unit did not contain water and appeared to not have had water seep into the unit as a result of submersion after the accident. The unit was contaminated with foreign debris to the point it would have restricted flow of hydraulic fluid through the unit. This would have resulted in high hydraulic system temperature and low pressure according to Hawker Pacific personnel which would cause loss of hydraulic pressure to the flight control actuators. See attached FAA hydraulic component test report. Examination of the foreign debris and filter element from the hydraulic manifold was performed by the NTSB Material Laboratory. The debris was consistent with products from the corrosion of aluminum. (See the Metallurgist's Factual Report.) Eurocopter (Aerospatiale) maintenance specifications call for examination of the hydraulic manifold and filter each 500 hours. N35AH had received a 500-hour inspection on March 27, 1995, about 50 flight hours before the accident. On January 19, 1995, Eurocopter issued Optional Service Bulletin No. 29.06 for replacement of the hydraulic system 25 micron filter with a 3 micron filter and clogging indicator. N35AH had not had this Service Bulletin complied with. (See the FAA hydraulic component test report and Eurocopter maintenance specifications.) The flight manual for the Aerospatiale AS350 calls for reduction of airspeed to between 40 and 60 knots following illumination of the hydraulic failure light and sounding of the associated warning horn. Following this, the hydraulic system should be turned off and a landing made. The pilot issued a release to Tampa General Hospital allowing the hospital to release the results of toxicology tests performed on specimens obtained from him about 2 hours after the accident. These tests were negative for ethanol alcohol, cannabinoids, and drugs. The aircraft wreckage was released to the registered owner in custody of R. M. Barrett, Claims Manager, USAIG, Orlando, Florida, on May 23, 1995. Components retained by NTSB for testing were released to Mr. Barrett on September 14, 1995.
THE FAILURE OF THE PILOT TO FOLLOW MANUFACTURERS PROCEDURES AFTER FAILURE OF THE HYDRAULIC SYSTEM RESULTING IN LOSS OF CONTROL OF THE HELICOPTER. CONTRIBUTING TO THE ACCIDENT WAS THE FAILURE OF MAINTENANCE PERSONNEL TO FOLLOW MANUFACTURERS PROCEDURES FOR MAINTENANCE OF THE HYDRAULIC SYSTEM.
Source: NTSB Aviation Accident Database
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