SHREVEPORT, LA, USA
N24AD
Nanchang CJ-6A
The single engine tandem airplane departed the airport to join a similar aircraft for a local flight. While maneuvering at an estimated altitude of 1,000 feet, the pilot reported 'going down, engine quit.' The pilot of the other airplane reported that he observed the airplane entering a left turn to try to make a field. The pilot witnessing the accident added that 'the pilot tried to extend his glide, experiencing an accelerated stall. The aircraft impacted the ground wings level in a 20 to 30 degrees nose down attitude, bounced, and caught on fire.' The initial point of impact was approximately 50 feet beyond a line of tall trees. Examination of the carburetor revealed that the throttle plate was found jammed in the full open position and the diaphragm assembly was found to be ruptured and very brittle, giving the appearance of being 'dry-rotten.' Particles of the broken diaphragm were found throughout the carburetor assembly. The airframe and engine logbooks for the airplane were stored in the airplane at the time of the accident and were presumed destroyed. The investigation was unable to establish the date of the last overhaul/repair on the carburetor assembly or when the failed diaphragm was installed.
HISTORY OF FLIGHT On May 16, 1996, at 1722 central daylight time, a Nanchang CJ-6A aiplane, N24AD, was destroyed following a loss of control during a forced landing near Shreveport, Louisiana. The commercial pilot and his passenger were fatally injured. Visual meteorological conditions prevailed and a flight plan was not filed. The aircraft was owned and operated by 3 private owners under Title 14 CFR Part 91. The flight originated from the Shreveport Downtown Airport about 5 minutes before the accident. According to one of the owners, N24AD departed the Shreveport Downtown Airport a few minutes after another Nanchang CJ-6A, N10JE, which he was already airborne in the local area. The pilots of both airplanes had previously agreed to join up for a flight within the local area, and therefore were monitoring a common frequency. As the two pilots were talking on the radio, with approximately a one mile separation, the pilot of N24AD stated "stand-by, going down, the engine quit." The pilot of N10JE twice asked if he had "fuel flow and ignition" to which the other pilot replied "it's all there." The pilot of N10JE estimated that N24AD was at an altitude of 1,000 feet at the time of the reported loss of engine power. The airplane was last observed entering a left turn to try to make a field. According to the pilot of N10JE, "the pilot tried to extend his glide, experiencing an accelerated stall. The aircraft impacted the ground wings level in a 20 to 30 degrees nose down attitude, bounced, and caught on fire." PERSONNEL INFORMATION The commercial pilot was a certificated instrument flight instructor with single and multiengine land ratings. He had accumulated a total of 1,280 flight hours, with a total of 55 hours in the accident airplane, all of them within the last 90 days. The pilot held a first class medical certificate issued on July 21, 1995, with no waivers or limitations. The non-rated passenger, who was seated in the aft seat, was a friend of the pilot who was reported to be on his first flight on an airplane. According to a mechanic that met the passenger before boarding, the passenger was briefed for the local flight. AIRCRAFT INFORMATION The single-engine tandem two-seat airplane was manufactured in Red China in 1982 as a Nanchang CJ-6A as a primary military trainer for the Chinese armed forces. The airplane was registered in the experimental category. The airplane was imported to the United States on July 22, 1992, with 3,935.39 flight hours and 3 previous overhauls. A special airworthiness certificate was issued by the FAA on August 11, 1992. The last annual inspection was performed on November 1, 1995, at 4281.0 flight hours. According to the owners, the airframe, engine, and propeller logbooks were in the airplane at the time of the accident, and were presumed destroyed in the post-impact fire. Fourteen pages of selected pages of the engine and airframe logbooks had been previously copied during the last annual inspection. They were provided to the investigator-in-charge and are enclosed in this report. The three owners of the airplane were: Steven L. Pursley, James L. Partington, and Charles A. Morgan. The previous owner of the airplane, John S. Thigpen, of Alexandria, Louisiana, sold the airplane to the present owners on February 27, 1996. According to one of the owners, an air valve associated with the airplane's pneumatic system was replaced and adjusted prior to the accident flight. No maintenance was performed on the engine or engine related system prior to the accident. The airplane was flown twice by the same pilot on the day of the accident. Each flight was reported to have lasted approximately 10 minutes and no anomalies were reported by the pilot on either flights. The airplane was topped-off with 100LL fuel the day before the accident. Based on an estimated fuel consumption of approximately 20 gallons per hour, 40 gallons of fuel were estimated to be on board the airplane at the time of its last takeoff. METEROLOGICAL INFORMATION Shreveport AWOS (SHV) reported the weather as clear below 12,000 feet with visibility at greater than 10 miles. The temperature was 84 degrees and the dew-point was 68 degrees. The winds were from 160 degrees at 10 knots. The altimeter setting was 29.95 inches. Density altitude was estimated at 1,600 feet. WRECKAGE AND IMPACT INFORMATION The initial ground impact was on a measured heading of 340 degrees magnetic. The aircraft came to rest on a heading of 280 degrees, approximately 50 feet beyond the initial point of impact. The initial point of impact was approximately 50 feet beyond a line of tall trees. No evidence of impact with the trees was found during a detailed examination of the trees. The initial impact point was a ground scar approximately 13 feet in length resembling the left wing and the fuselage of the airplane. A gouge was noted in the ground scar with blue paint chips in it matching the primer used on the propeller. The airplane came to rest on its belly. All flight control surfaces remained attached to the airframe and continuity was established to all of the flight controls. The landing gear and flaps were found in the retracted position. The single row 9-cylinder radial engine was found upside down with the propeller still attached to the crankshaft. The propeller blade angle was in the low pitch/high RPM position. The propeller blades did not exhibit any "S" bending, striations, or chordwise scratches. Blade number B2176 was bent back toward the engine, and the other blade was undamaged. The crankshaft was bent slightly at the propeller flange. It was noted that the oil in the engine appeared very clean. There were no internal signatures of lubrication starvation or thermal distress found within the engine. The magneto switches for the front and rear cockpits were both located. They were both found in the "both" position. The top of the right hand magneto was broken off. Both magnetos were removed, and both shafts were rotated freely by hand. The engine has a single pump that provides pressure for both the fuel and the oil system. The pump was removed, and it rotated by hand freely. The K-14G1 pressure carburetor, serial number 906D361, was broken off about two inches above its mount to the accessory section. The external body of the aluminum carburetor assembly sustained thermal damage; however, no thermal deformation was found. The carburetor assembly was removed from the engine and transported to a shop at the airport for a detailed inspection and examination. The throttle plate was found jammed in the full open position. The finger strainer for the air system contained some small, non-ferrous metal particles. The diaphragm assembly was found to be ruptured and very brittle, giving the appearance of being "dry-rotten." Particles from the broken diaphragm were found throughout the carburetor assembly. O-rings and other non-metallic components within the carburetor assembly did not exhibit signs of thermal distress. The oil sump located between the number 4 and the number 5 cylinder was broken off. Both the number 4 and number 5 cylinders together had broken off of the crankcase and had taken off the piece of the accessory section that joined them together. Number 5 cylinder had the exhaust valve rocker box broken off. The generator and propeller governor were still connected to the engine. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy and toxicological tests were ordered and performed. The autopsy was performed by Brenda K. Reames, M.D., on May 17, 1996, at bossier City, Louisiana, as requested by the Caddo Parish Coroner's Officer. The cause of death for the pilot was blunt trauma of the head and trunk. According to the pathologist, the carbon monoxide level was less than 1%, indicating that inhalation of smoke did not contribute to this death. Toxicological tests were negative. FIRE No evidence of pre-impact fire was found during the investigation. The post-impact fire burned across from one fuel tank to the other, destroying both cockpits aft of the engine firewall. The airborne witness told local law enforcement investigators that "the airplane burst into flames as soon as it came to a stop during the accident sequence." SURVIVAL FACTORS The airplane was equipped with a five-point restraining system. The seat belts and shoulder harnesses for both cockpits were found latched. No physical evidence of any attempt to egress the airplane were made from either cockpit. Fire suppression equipment from the local fire department and law enforcement personnel arrived at the scene of the accident within 7 minutes of the occurrence. The accident was not survivable due to that impact forces encountered were beyond the human tolerance levels. ADDITIONAL INFORMATION The airplane was released to the owner's representative at the conclusion of the field investigation.
a loss of engine power due to failure of the pressure carburetor diaphragm which led to restricted fuel flow through the carburetor and eventual fuel starvation. Factors contributing to the accident were the unsuitable terrain and tall trees which resulted in the pilot's inadvertent stall during the forced landing.
Source: NTSB Aviation Accident Database
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