NTSB Factual Report

On December 18, 1999, at about 0917 central standard time, a Swertfeger Velocity 173 Elite, experimental homebuilt airplane, N627KB, registered to a private owner, operating as a 14 CFR Part 91 personal flight, crashed while on approach to Murfreesboro Municipal Airport, (MBT), Murfreesboro, Tennessee. Visual meteorological conditions prevailed and no flight plan was filed. The airplane sustained substantial damage. The private pilot was fatally injured. The flight originated from Decatur, Alabama, (DCU) at an undetermined time.

According to a witness, the accident pilot departed DCU following another pilot. He had talked to the pilots while taxiing out for takeoff at DCU over the airplane radio and determined that they were all going to the same breakfast fly-in. He caught up with the other two airplanes while en route to MBT. Upon arrival at MBT, N627KB entered traffic for runway 18, and he was located behind him. Someone announced on the UNICOM frequency that they were changing the landing runway to runway 36. He broke out of the current traffic pattern, entered downwind for runway 36, landed, and taxied to the parking ramp. A short time later, he heard N627KB state that his engine was out. He turned his airplane around and observed N627KB disappear behind the trees.

Several witnesses on the ground observed the airplane flying lower than normal, and stated they heard sounds like the engine was trying to quit or was cutting on and off or cutting out before the accident.

Two friends of the deceased pilot stated that about a month before the accident that they had both observed problems with N627KB. One friend stated that the pilot had the habit of taxiing his airplane straight into the hangar, and he would open the hangar door for him. When the pilot advanced the throttle forward from the idle position, the engine sputtered, black smoke came out of the exhaust and the engine quit. The engine was very hard to start, as it would start and quit again. The other friend stated that he flew with the deceased pilot on November 29, 1999. He reduced power to do some slow flight. As the plane began to slow it began to vibrate. He told him, he thought the engine had quit. The pilot increased throttle and nothing happened. He asked the pilot if the engine was fuel injected and he replied that it was. He instructed the pilot to pull the mixture. He complied with the request and the engine fired up.

Examination of the airframe revealed no evidence to indicate any mechanical failure or malfunction prior to the accident. All components necessary for flight were present at the accident site. Control continuity could not be established.

The engine was transported to the Murfreesboro airport and examined. The engine remained attached to the engine mounts and firewall with the propeller and hub extension attached. The cooling baffles were removed, the tops of the engine cylinders were discolored and were tan in color. The top spark plugs were removed and were very black and sooty. The remains of the propeller were removed. The crankshaft rotated freely. A thumb compression test confirmed good compression and suction in all cylinders. The fuel servo air ducting contained fragments of leaves and small pieces of tree bark. The flange where the air ducting is attached to the fuel servo was noted to have what appeared to be an excess of orange sealant material inside the flange. A fuel line located on the bottom of the firewall had a white towel wrapped around it. Fuel was present in the flow divider, but was not present in the fuel line between the fuel servo and the flow divider. The bottom spark plugs were removed and were very black and sooty. The fuel servo was removed and forwarded to the NTSB Investigator-In-Charge for further analysis. For additional information see the FAA inspector statement and Textron Lycoming Aircraft Mishap Investigation Single engine Final Report, which are attachments to this report.)

Review of records on file with the NTSB revealed the engine on N627KB had been installed in another Velocity 173, N28KJ, which experienced a loss of engine power and crashed on May 14, 1996. Review of the Textron Lycoming Accident Investigation Report revealed that the engine was the same engine that was installed on N627KB. The serial number on the servo fuel injector on N28KJ was 42088. The serial number of the servo fuel injector installed on N627KB was 42083.

Examination of the servo fuel injector was conducted at an authorized repair station. The data plate indicates the Parts List Number is 2524054-7. Bendix Service Bulletin RS-86 dated December 23, 1983, recommends the fuel diaphragm assembly to be replaced at the next overhaul or repair. The fuel diaphragm had not been replaced. The servo had not been updated to the latest -10 servo. Precision Airmotive Corporation Service Bulletin Fuel System, PRS-97 dated October 22, 1990, states the time between overhaul for all fuel system components is 10 years.

The main fuel strainer servo screen was removed and no foreign object damage was present. Rust was present inside the regulator plug. A homemade air scoop shroud had been fabricated for the intake duct. RTV sealant was used as a gasket. A seal was safety wired on the access plug to the regulator calibration nut. The seal has the letters EO on the tag.

The servo fuel injector was placed in a test bench and a functional check was performed. Fuel was pouring out of the venturi causing an erratic air flow through the regulator and an erratic fuel flow. The regulator air cover was removed for examination of the air diaphragm. The air diaphragm assembly was not changed IAW Bendix Service Bulletin Fuel Systems RS-61 Rev.1 dated February 1, 1979. The fuel diaphragm stem was bent. The air cover and diaphragm was removed to determine the source of the fuel leak. Fuel was observed flowing out of the fuel diaphragm stem and center body bellows. The center body was removed with the fuel diaphragm attached to the center body bellows. No FOD was present. The bottom calibration nut was removed from the fuel diaphragm stem. The fuel diaphragm was removed from the bellows. An leakage check was performed. The check revealed the bellows was split and air was leaking through the bellows.

AD 78-23-10, dated March 15, 1978, states, "Compliance required within the next 10 hours in service after the effective date of this AD, unless previously accomplished. To prevent an in flight power loss due to an over rich condition caused by the failure of the center body bellows seal assembly, replace the center body bellows seal assembly and tube bushings in accordance with Accomplishment and identification instructions in the applicable Bendix Energy Controls Division Service Bulletin No. RS-52 Rev. 2 revised May 12. Examination of the center body bellows revealed that it had been modified (drilled out) to a larger size, and a plastic sleeve had been installed. Conforming bushings had been installed on the fuel diaphragm stem through the center body bellows. The two individual bushings had been soldered together as one assembly instead of an individual assembly as required by Precision Airmotive Corporation Maintenance Manual, Form 15-381G,change 1, dated June 1, 1992. The maintenance manual states on page 1, revision 1- 6/1/92, "Warning: The use of any nonspecified parts, or parts which do not strictly conform to the specifications and drawings for this model fuel injector can cause product malfunctions which could result in damage to, or destruction of, equipment and injury to and/or death of personnel. Use only the replacement parts specified in the illustrated parts breakdown section." It could not be determine who or when the servo fuel injector was last worked on.

Postmortem examination of the pilot was conducted by Dr. John E. Gerber, Associate Medical Examiner, Forensic Sciences Center of Davidson County, Nashville, Tennessee, on December 19, 1999. The cause of death was multiple blunt force injuries. Postmortem toxicology of specimens from the pilot was performed by the Forensic Toxicology Research Section, Federal aviation Administration, Oklahoma City, Oklahoma. These studies were negative for carbon monoxide, cyanide or ethanol. Diphenhydramine 0.119 (ug/ml, ug/g), an over the counter sedating antihistamine was detected in the blood, and 1.768 (ug/ml, ug/g) was detected in the liver. Chlorpheniramine 0.124 (ug/ml, ug/g), an over the counter sedating antihistamine was detected in the liver.

The servo fuel injector, fuel pump, and eight spark plugs were released to Mr. Phil Powell, Insurance Adjuster, Carson Brooks, Atlanta, Georgia, on February 28, 2000.

NTSB Probable Cause

The failure of an unknown maintenance person to comply with an Airworthiness Directive (replace center body bellows seal assembly and tube bushings) and Service Bulletin (replace fuel diaphragm) resulting in an in-flight power loss due to an over rich condition caused by the failure of the center body bellows seal assembly, and subsequent forced landing and in-flight collision with terrain.