INDEPENDENCE, OR, USA
N998TT
Oveross VANS RV-8
Approximately 100 feet above ground level the engine of the pilot/builder assembled RV-8 kit-plane began to run rough. The pilot made a left 90 degree turn to return to land during which all power was lost. He then turned back right and landed hard, collapsing the landing gear. Fueling records revealed approximately 10 gallons of fuel in the right tank per the pilot's estimate. Post-crash examination revealed that the fuel pick-up tube within the right tank had become mis-positioned (twisted) approximately 180 degrees, placing the tube pick-up end at the mid-level of the 21 gallon tank, and resulting in fuel starvation. The pilot had done maintenance on the right tank several weeks earlier including tightening a hex nut which retained the 90-degree elbow fitting holding the pick-up tube in place. Tightening of the hex nut without an anti-rotation bracket could rotate the pick-up tube into a mis-position. The aircraft design and construction predated the dissemination of design plans containing the anti-rotation bracket, and the manufacturer had not issued any notice of the bracket specifications to the pilot/builder. The pilot/builder, unaware of the specifications, had not installed the bracket in the right fuel tank.
On May 7, 2000, approximately 0801 Pacific daylight time, a homebuilt Oveross model Vans RV-8, N998TT, was substantially damaged when the landing gear collapsed during a forced landing immediately after takeoff at the Independence State airport, Independence, Oregon. The pilot was uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14CFR91, and was to have been local. The pilot reported that he took off on runway 34, and "noticed a brief smell of fuel just as I lifted off." He also reported that passing through about 100 feet above ground level, the engine began to run rough and he executed a left 90 degree turn with the intention of returning to land. The engine then stopped, and he executed a second reverse turn back to the north touching down slightly northwest of the upwind end of the runway. An inspector from the Federal Aviation Administration's Hillsboro, Oregon, Flight Standards District Office examined the accident site and interviewed the pilot. The inspector described the gear damage as "both landing gear were spread out touching their respective wings (refer to ATTACHMENT FAA-I). The aircraft was last fueled on April 29, 2000, with 25.5 gallons of 100 low lead aviation fuel. The fueling occurred at the local fixed based operator at the Independence State airport and, according to the pilot, the aircraft's fuel tanks were topped at that time. According to the pilot, the aircraft was flown for approximately 3.1 hours on 6 flights between the fueling and the accident flight. He also reported that the left fuel tank was nearly empty at the time of the accident flight and the right tank was approximately half full (10 gallons). He also reported that he did not visually check the fuel quantity in the fuel tanks prior to the accident flight. A representative of Van's aircraft, the kit manufacture, reported that the aircraft was equipped with two 21 gallon fuel tanks. Each tank extended from the wing root area outboard and between the leading edge of the wing aft to the forward face of the spar. A fuel pickup tube mounted in each tank was positioned so as to utilize virtually all available fuel (minimal unusable fuel). Each pickup, consisting of an aluminum tube formed in a 90 degree arc and with a slotted end, was normally positioned such that the tube was initially oriented down (vertically) and then gradually arced aft so as to parallel the bottom of the fuel tank (refer to DIAGRAM I). The tube's end was crimped off and a number of cuts were made halfway through the tube's diameter which allowed fuel to be picked up while serving as a coarse grade filter. The tube was attached to a 90-degree elbow fitting which then passed through the circular fuel tank access plate. The fuel line to the fuel selector then attached to the elbow fitting on the inboard (fuselage) side of the elbow. Examination of the aircraft schematics for the left tank (reversed for the right tank) revealed that the nut which holds the 90-degree elbow fitting up tight against the access plate would be tightened by rotating the nut clockwise when looking outboard. With no opposing force on the elbow fitting, and while tightening the nut, it would be possible to rotate the elbow and thus deform and reposition the fuel pick-up tube within the tank. This condition would not be identifiable unless the access panel were removed and the pick-up tube examined visually after the tightening process. The pilot reported in a telephone conversation with the investigator-in-charge, that several weeks prior to the accident he had performed maintenance on the right fuel system, specifically tightening the 90-degree elbow fitting nut. Subsequent to the accident he and another RV aircraft builder removed the right fuel tank access plate to effect repairs and found the right tank fuel pick-up line deformed and mis-positioned by nearly 180 degrees. When the fuel tank access plate was positioned in its proper perspective at the tank access port the fuel pickup line was observed to have been deformed and rotated such that the pickup end was seated well above the bottom of the tank (refer to DIAGRAM II and IMAGE I). A review of the design schematics for the RV-8 aircraft provided by the kit manufacturer showed that an "anti-rotation" bracket was specified for each fuel tank 90-elbow fitting. This bracket, a 90-degree elbow piece of metal, was to be affixed to the inside of the fuel tank access plate. The 90-degree elbow was then to be inserted in the hole within the bracket. This arrangement would prevent the elbow from rotating whenever the retaining nut was tightened or loosened. The date of the anti-rotation bracket inclusion (item R6) on the schematic was 08/99 (refer to SCHEMATIC I). No anti-rotation bracket was installed on the accident aircraft. According to records maintained by the Federal Aviation Administration, N998TT had been registered on June 11, 1998. The aircraft's last annual examination was conducted on July 31, 1999, one month previous to the release of the anti-rotation bracket design. The kit manufacturer reported that no service bulletin or newsletter notification had been disseminated regarding the bracket. Additionally, the anti-rotation bracket was common to a number of RV aircraft fuel systems(RV-3, RV-4, RV-6, RV-8 and RV-9) and was, as of August 1999, considered to be standard in the design of these aircraft.
The rotation of the right fuel tank elbow fitting within the tank during previous maintenance. The improper alignment resulted in the fuel pick-up tube being mis-positioned and a subsequent starvation of fuel to the engine. Contributing factors were the non-installation of an anti-rotation bracket to secure the elbow fitting, the kit manufacturer's failure to issue a notice of the bracket design to previous aircraft owners, and the pilot's not establishing/maintaining a proper rate of descent resulting in a hard landing.
Source: NTSB Aviation Accident Database
Aviation Accidents App
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