STATESVILLE, NC, USA
N1551K
BEECH A36
THE FLIGHT WAS ON AN IFR FLIGHT PLAN, AND THE WEATHER IN THE VICINITY WAS VFR CONDITIONS. THE PILOT HAD BEEN CLEARED TO DESCEND FROM 9000 FT TO 7000 FT. RADAR DATA SHOWS THAT THE AIRCRAFT DESCENDED TO 7000 FT, LEVELED OFF MOMENTARILY, AND THEN MADE A STEEP RIGHT TURN AND BEGAN A DESCENT. ATTEMPTS TO COMMUNICATE WITH THE PILOT AFTER THE DESCENT WERE UNSUCCESSFUL. THE AIRCRAFT IMPACTED THE TERRAIN AT A HIGH RATE OF SPEED IN A NOSE DOWN LEFT TURN. THE WRECKAGE WAS DISTRIBUTED ON A HEADING OF 170 DEG, OVER AN AREA APPROX 540 FT LONG. THERE WERE NO RECORDED INSTANCES OF PRIOR MECHANICAL PROBLEMS WITH THE AUTOPILOT SYSTEM.
HISTORY OF FLIGHT On May 22, 1994, at 1306 eastern daylight time, a Beech A36, N1551K was destroyed following an uncontrolled collision with terrain near Statesville, North Carolina. The commercial pilot was fatally injured in the collision. The aircraft was being operated under the provisions of 14 CFR Part 91 by the pilot. Visual meteorological conditions existed at the time, and an instrument flight rules flight plan was in effect for the flight. The flight departed Arlington, Tennessee at 1021, and was enroute to Mocksville, North Carolina. The flight was cleared by air traffic control to descend from 9000 feet to 7000 feet for Mocksville. Radar data showed that the aircraft descended to 7000 feet, leveled off momentarily, and then began a descending right turn. No further communications were established with the pilot of the aircraft. Witnesses, located approximately one mile north of the accident site, stated the aircraft passed over at tree top level traveling from south to north. The aircraft then made a sharp climbing course reversal and disappeared over the trees. Another witness, located approximately 1000 feet north of the accident site, stated that the aircraft passed over his residence just above the tree tops. He stated that at that time, the aircraft was in an approximate 90 degree left wing down attitude. The aircraft contacted a group of trees, impacted the terrain, a lawn mower, and a mobile home. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with airplane single engine and instrument airplane ratings. He held a third class medical certificate with a limitation for the use of eyeglasses while operating aircraft. No pilot log books were located for the pilot. His medical application dated August 30, 1993 showed at that time, he had approximately 1300 hours of flight experience. The pilots wife stated that he had suffered a seizure while at home on the evening of January 22, 1994. His personal physician confirmed that the pilot had been admitted to the hospital on January 22, 1994 with what appeared to be a seizure. He stated that all tests to determine the cause of the seizure were negative. He stated that the pilot had been taking an anti inflammatory drug in combination with aspirin, and that he felt that might have caused the problem. Additional personnel information may be obtained in this report on page 3 under section titled Pilot Information. AIRCRAFT INFORMATION The Beech A36 is a single engine, 6 place, retractable tricycle landing gear airplane. The aircraft had been modified with a turbonormalizing system in accordance with supplemental type certificate number SA5223NM. Additional aircraft information may be obtained in this report on page 2 under section titled aircraft information. METEOROLOGICAL INFORMATION Visual meteorological conditions existed at the time of the accident. Witnesses in the area reported that the skies were clear, and there was a light wind in the area out of the west. Additional meteorological information may be obtained in this report on page 3 under section titled Weather Information. WRECKAGE AND IMPACT INFORMATION The aircraft impacted the terrain on a heading of 170 degrees. The area of the accident was sparsely populated, and consisted of gently rolling woodlands and pasture land. There was general disintegration of the aircraft over an area of approximately 540 feet in length. (See Wreckage Distribution Diagram for Details.) All flight control surfaces were accounted for in the aircraft wreckage. All flight control cable fractures showed signs of typical tensile overload failure. The aircraft engine suffered severe impact damage which removed all of the engine accessories and the number five and six cylinders. The engine interior appeared clean, and had slight carbon deposits in the combustion areas. The spark plugs were clean, and exhibited little wear when compared with a manufacturer's inspection chart. There was fuel found in the fuel lines attached to the fuel servo. The propeller blades were separated from the hub. The propeller blades showed signs of "S" bending, and twisting toward low pitch. There were chordwise scratches on the surface of the blades. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy of the pilot was conducted by the North Carolina Office of The Chief Medical Examiner in Chapel Hill, North Carolina. The Medical Examiner lists the cause of death as multiple traumatic injuries sustained in the aircraft accident. No toxicological examination was conducted due to the absence of suitable specimens. TEST AND RESEARCH A test of the aircraft autopilot system was conducted at the facilities of Allied Signal Aerospace, Incorporated in Olathe, Kansas on July 20, 1994. The test were conducted under the supervision of Aviation Safety Inspector Gary Benson of the Kansas City Federal Aviation Administration Flight Standards District Office. The following is a synopsis of those tests.(See Attached Laboratory Notebook for Details.) KS 270A Pitch Servo The servo motor pinion gear was in contact with the edge of the through hole of the base plate. There was a static impact mark on the edge of the through hole. When an autopilot (AP) clutch engage signal was provided by the test set the engage solenoid engaged normally and it disengaged when the engage signal was removed. The servo motor did not run when the engage signal was applied. The engage solenoid would also disengage when test set power was turned off. When a servo command signal was applied the servo motor ran in the correct direction for the applied command signal. the servo motor breakout voltage was 1.5 volts in both directions. Linear servo speed control was demonstrated with varying command signals for both directions of rotation. The trim sense micro switches functioned for both a clockwise and a counterclockwise torque. KM 275 Pitch Servo Mount The base plate was warped and there were both static and rotational marks on the inside of the capstan gear housing. There was an impact mark on the upper land of one of the capstan teeth. The slip clutch torque values were measured at 21 inch pounds clockwise, and 20 inch pounds counterclockwise. The specification in the installation manual is 18 plus or minus 2 inch pounds. KS 272A Trim Servo The servo cover was broken exposing the interior components. There was dirt on most of the interior components. A piece of debris was on one of the servo motor brushes. The transfer relay bracket was bent so that the relay was in contact with the servo motor. There was a crack in the servo housing near the printed circuit board. When an auto electric trim engage signal was provided by the test set the engage solenoid engaged normally, and it disengaged when the engage signal was removed. The engage solenoid would also disengage when test set power was turned off. When a manual electric trim engage signal was provided by the test set the engage solenoid engaged normally, and it disengaged when the engage signal was removed. The engage solenoid would also disengage when test set power was turned off. The servo motor would not run in either direction when a manual electric trim command signal was applied. The servo motor would not run in the clockwise direction when an auto electric trim command signal was applied. The servo exhibited a shorted condition when a counterclockwise direction auto electric trim command signal was applied. It was verified that the trim transfer relay worked. The manual electric trim drive voltage was plus 19.1 volts. The specification calls for a voltage between 15.5 volts. and 21.0 volts. KM 275 Trim Servo Mount The base plate was warped and there were both static and rotational marks on the inside of the capstan gear housing. There were impact marks on the upper lands of several of the capstan teeth. The slip clutch torque values were measured at 40 inch pounds clockwise and 40 inch pounds counterclockwise. The specification in the installation manual is 40 plus or minus 3 inch pounds. KS 271A Roll Servo The servo base plate was warped and the servo motor pinion gear was missing. There were four static impact marks on the pinion gear through hole of the base plate. There were several cracks in the servo cover. The engage plate assembly was broken and part of the assembly was missing. The engage solenoid housing was broken. One of the servo motor brushes was missing which precluded testing the servo motor. When an engage signal was provided by the test set the engage solenoid engaged normally and it disengaged when the engage signal was removed. The engage solenoid would also disengage when test set power was turned off. KM 275 Roll Servo Mount The base plate was warped, and the capstan assembly and the capstan bearing post were missing. There were both static and rotational marks in the capstan housing. ADDITIONAL INFORMATION The aircraft wreckage was released to the owner's insurance representative, Mr. Mark Thompson of USAIG, on May 24, 1994.
A LOSS OF CONTROL FOR UNDETERMINED REASON(s).
Source: NTSB Aviation Accident Database
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