BURLINGTON, IA, USA
N412LF
FIRST STRIKE BOBCAT
The damaged airplane was found at a location that correlated with a right downwind for runway 18. There were indications that it had collided with trees during a forced landing, then impacted the ground. Initial impact was with a 30 foot tree. Investigation did not be determined how long the airplane had been airborne before the accident. There was no damage to the propeller. The fuel tank had ruptured during impact. The engine and flight controls had continuity. Inspection revealed that the copper fuel line from the carburetor to the strainer was broken at the carburetor ferrule fitting, in an area immediately adjacent to a ferrule nut. Examination of the fracture surface revealed fine crack arrest markings, indicative of fatigue. The fatigue cracking originated on the outside surface of the tube.
History of Flight On July 7, 1995, sometime between 0730 and 1230, central daylight time, an experimental First Strike Bobcat, N412LF, sustained substantial damage during a forced landing due to loss of engine power at Burlington, Iowa. The private pilot was fatally injured. The 14 CFR Part 91 flight departed Burlington Municipal Airport, Burlington, Iowa, on a local flight. Visual meteorological conditions prevailed and no flight plan was filed. An Operations Inspector from the Federal Aviation Administration reported that the airplane wreckage location correlated with a downwind position for runway 18 at Burlington Municipal Airport, Burlington, Iowa. The airplane struck a tree about 30 feet above the ground heading approximately 354 degrees. There was no ground scarring to indicate any forward movement after impact with the ground. The airplane landed inverted with the nose of the aircraft on a 154 degree heading. (See attachments) It could not be determined how long the airplane had been airborne prior to the accident. The wreckage had been located by another airplane flying in the area. The son of the deceased pilot reported to the Des Moines County Sheriff that the airplane had a total fuel capacity of eight gallons. It burned two and a half gallons per hour and it had been filled a week prior to the accident. However, he reported that the hour meter on the aircraft was not working correctly. The inspection of the airplane revealed that the hour meter indicated 0.3 at the time of the accident. (See attachments) The pilot's logbook did not indicate how much he had flown the experimental airplane since certification on June 21, 1995. The last entry in the pilot's logbook was dated April 23, 1994. Personnel Information The pilot held a private pilot's certificate with a single engine land rating. He had a current third class medical certificate. His last recorded biennial flight review was conducted on July 7, 1990, in an Aeronca Chief. He was issued a Temporary Airman Certificate: Repairman, on June 21, 1995. The pilot had built two other experimental airplanes prior to the building the First Strike Bobcat, N412LF. The first plane he built was also a Bobcat which he had flown for about 96 hours between 1986 to 1989. He had no further logbook entries of piloting a Bobcat after 1989. Aircraft Information The airplane was an experimental First Strike Bobcat built by the pilot, serial number 412. The registration number N412LF was issued on February 23, 1995. The pilot kept a logbook which he used to record his progress during the building of the airplane. The log entry on May 17, 1995, indicates that an Airworthiness Inspector from the Federal Aviation Administration had inspected the airplane. The inspector did not issue a Special Airworthiness Certificate on May 17, 1995, but instead listed numerous items that needed to be corrected on the airplane before the certificate could be issued. On May 22, 1995, the pilot noted in his logbook that he had corrected two of the discrepancies involving the fuel line and carburetor. One entry stated that he had installed a rubber retainer over the fuel line. The second entry noted that he had installed a carburetor retainer that secured the carburetor to the engine. The logbook indicates that the pilot had completed all the corrections by May 24, 1995, and had written a letter to the Airworthiness Inspector informing him of the corrections. The Airworthiness Inspector re-inspected the airplane on June 21, 1995 and issued a Special Airworthiness Certificate. (See attachments) Wreckage and Impact Information The Federal Aviation Administration inspectors reported that the airplane was destroyed on impact with the ground. There was no damage to the propeller and the propeller had stopped in a horizontal position. The fuel tank was ruptured with no presence of fuel in the tank. The fuel strainer contained approximately 1/2 cup of aviation grade fuel when drained. A continuity check was performed on the engine and it revealed that the engine rotated freely, had normal valve operation, and had compression on both cylinders. The magneto rotated freely and produced spark at each of the two spark plugs. The two spark plugs showed no evidence of excess fuel when removed. All control surfaces were found intact and found to be operational with the exception of the left aileron due to the separation of the aileron push rod mounting block. The inspection also revealed that the copper fuel line from the carburetor to the strainer was broken at the carburetor ferrule fitting. The fuel line from the carburetor to the firewall consisted of about a six inch copper tube attached to a flexible hose. The carburetor and copper fuel line were removed for analysis by the National Transportation Safety Board. An examination of the carburetor and fuel line was conducted by the Materials Laboratory Division of the National Transportation Safety Board. The inspection revealed that the copper fuel line separated in the area immediately adjacent to a ferrule nut. An examination of the fuel line revealed fine crack arrest markings indicative of fatigue fracture mechanism. The fatigue cracking originated at the outside diameter surface of the tube; however, due to the extent of damage, the exact position of the fracture origin(s) could not be determined. (See attachments) Medical and Pathological Information An autopsy was conducted at the Burlington Medical Center, Burlington, Iowa. The pilot held a valid medical certificate which had an expiration date of August 31, 1995. The toxicology report indicated the following results: 3.100 (ug/ml, ug/g) Procainamide detected in Blood 9.000 (ug/ml, ug/g) N-acetylprocainamide detected in Blood Procainamide was detected in Liver Fluid N-acetylprocainamide was detected in Liver Fluid Procainamide was detected in Lung Fluid N-acetylprocainamide was detected in Lung Fluid Verapamil was detected in Blood Norverapamil was detected in Blood Verapamil was detected in Liver Fluid Norverapamil was detected in Liver Fluid Verapamil was detected in Lung Fluid Norverapamil was detected in Lung Fluid The pilot had a history of hypertension since 1973, and he underwent a triple vessel coronary artery bypass surgery in 1988. He was taking prescription drugs for his medical condition. Additional Information The aircraft wreckage was released to the family of the pilot on July 8, 1995. The carburetor and fuel line were released to Andrew Lewis on November 16, 1995.
fatigue failure of a copper fuel line at the carburetor ferrule fitting, which resulted in fuel starvation. The proximity of trees was a related factor.
Source: NTSB Aviation Accident Database
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