FTW95FA266

The airplane was observed in level flight with the engine '...sputtering, cutting out....' The 'left wing dropped, then the right wing dropped, and the airplane rolled into a spin to the left.' As the airplane rotated toward the ground, witnesses described the 'motor running wide open.' Fibrous foreign material was found on all fuel system screens. The fuel system components were bench tested and the metering unit screen was also tested during an exemplar engine run. All testing was within manufacturer specifications. Fuel samples from the refueling locations tested within the standard specifications for aviation gasoline 100LL. The fuel metering screen foreign material and the bladder fuel cells contained types of fibers; however, a definitive source of the fibers could not be determined. Maximum gross weight (3,600 lbs) CG range is 82.1 inches to 83.8 inches. Weight at the time of the accident was calculated at 3466.5 lbs with a CG of 87.00 inches.

History of flight

On July 2, 1995, at 1006 central daylight time, a Beech V35B, N2777T, collided with terrain during an uncontrolled descent near Huntsville, Arkansas. The private pilot and 3 passengers sustained fatal injuries and the airplane was destroyed. The airplane was being operated as a personal flight by the co-owner under Title 14 CFR Part 91. The flight originated from Mountain Home, Arkansas. Visual meteorological conditions prevailed for the personal cross country flight and a flight plan was not filed.

During personal interviews, conducted by the investigator-in- charge, and on the enclosed statements witnesses reported the following information. The airplane was observed in level flight with the engine "winding up and slowing down"; "cutting out"; "going on and off"; "sputtering, cutting out"; and "surging in and out like trying to get fuel." One witness reported that subsequently, the "left wing dropped, then the right wing dropped, and the airplane rolled into a spin to the left for a long time and didn't pull out." Witnesses reported the airplane "dive nose first doing complete rotations"; "spin out of the sky falling with the motor running wide open"; "flat spin with engine winding up"; and "hit ground flat." The airplane impacted the ground on County Road 137, 7 miles southeast of Huntsville, Arkansas, approximately 50 nautical miles from the departure airport.

During a telephone interview, conducted by the investigator-in- charge, the owner reported the following information. The airplane was based at Arlington Municipal Airport, Arlington, Texas, and upon a return flight from Shreveport, Louisiana, on June 26, 1995, the airplane was fueled at Arlington (receipt enclosed) for the flight to the Mountain Home, Arkansas, resort. On June 29, 1995, the airplane arrived at the Baxter County Regional Airport where the main fuel tanks were refueled (enclosed receipt) with 38.3 gallons. On June 2, 1995, at approximately 0845, the pilot via telephone obtained a VFR weather briefing from Jonesboro Flight Service Station for the return flight to Arlington, Texas. The owner stated that there were "no previous discrepancies" with the airplane. He further stated the takeoff climb setting for flight was "25 inches" and "2,500 RPM's." Upon reaching altitude, cruise settings were "23 inches" and "2,300 RPM's" followed by a "leaning of the mixture."

During an interview, conducted by local authorities, Mr. Bryan Spain (one of the group at the resort), reported the following information. The pilot and 3 passengers were dropped off at the Baxter County Airport and the remaining 8 resort party members drove to Little Rock, Arkansas, and returned home on an airline flight. Some of the bags for the pilot and passengers were placed on the airliner.

Aircraft information

Flight log data obtained from the airplane indicated a tachometer reading of 957.3 on June 29, 1995. Additional maintenance data is included in the enclosed Maintenance Record Group Chairman's Report.

Wreckage and impact information

The airplane came to rest in a ditch with the right wing extending onto the adjacent dirt road. A portion of the engine cowling, one propeller blade, and the baggage door separated from the airplane. See the enclosed wreckage diagram.

The airplane cabin and cockpit area remained intact and were compressed downward and forward. Tachometer reading was 960.68. Fuel tank integrity was compromised. The propeller hub shattered and both blades separated from the engine and the propeller blades exhibited bending with the propeller tips showing bending, twisting, and striations. The propeller components were forwarded to McCauley for examination. Flight control cable continuity was confirmed to the cockpit area.

The engine, a Continental IO-520-BA, S/N 562374, was examined at the site. Portions of the crankcase and oil sump were destroyed. The engine firewall was crushed against the accessory section of the engine. When the engine was removed from the firewall, the throttle body unit was found crushed and detached from the engine. Engine continuity was confirmed, both magnetos sparked, and the top spark plugs were clean.

The fuel pump, P/N 638154-2, S/N C017609B, was removed and the drive coupling was intact. The pump shaft rotated by hand.

The fuel metering unit, P/N 629904-2, S/N B257629A, was examined and, at the initial removal, the air throttle fuel metering screen contained foreign material and liquid over "approximately 40 per cent" of the screen area. The foreign material covered the outside of the cylindrical shaped screen from one end to the other. The foreign material "appeared as a fibrous band directly across from the fuel inlet port when the screen was threaded into the metering unit."

The fuel manifold unit P/N 631427A6, S/N B097611C was disassembled and fuel was present in the unit. Foreign material that "appeared as granular deposits" was found on the fuel screen and material "similar in appearance" was also noted on the outlet port that connected to the fuel pressure line. The fuel nozzles were removed and no foreign material was noted in the nozzles.

The fuel selector was positioned on the "left" main fuel tank. The fuel selector unit, P/N 55034, was removed and visual examination of the screen revealed at least 3 types of foreign material that "appeared as fibrous, white granular pieces, and red flakes."

Visual examination of portions of the bladder fuel cells (P/N 2121-9 and 2121-10) did not reveal foreign material in the fuel cells. A fuel sample, from the left main fuel cell, was visually examined and the fuel was a "blue color" with no contaminants noted.

All fuel system filters exhibiting foreign material were retained by the NTSB for further examination and testing. The bladder fuel cells were removed on July 13, 1995, by the NTSB for further examination.

Four luggage bags and an empty golf club bag were reported as recovered from the airplane by local authorities. Total baggage weight was estimated as 75 pounds. Local authorities estimated the right front seat passenger's weight as 150 pounds, and the aft seat passengers at 190 and 160 respectively. Maximum gross weight (3,600 lbs) center of gravity (CG) range is 82.1 inches to 83.8 inches. Weight at the time of the accident was calculated at 3466.5 pounds with an aft CG of 87.00 inches.

Medical and pathological information

The autopsy was performed by the medical examiner division of the Arkansas State Crime Laboratory at Little Rock, Arkansas. According to Dr. Canfield, of the Federal Aviation Administration Civil Aeromedical Institute at Oklahoma City, Oklahoma, toxicology findings were negative.

Test and research

The fuel metering unit, fuel pump, and fuel manifold were disassembled and the location of the foreign material (visually examined at the site) on the fuel metering unit screen was determined to be 180 degrees from the fuel inlet port. No foreign material was found in the fuel pump. The fuel manifold screen (containing the foreign material visually examined at the site) was removed from the unit and the fuel manifold (new screen installed) flowed fuel out of the 6 outlet fittings. See the enclosed Maintenance Group Chairman's Report for additional details.

Fuel samples from the refueling operators at Arlington,Texas,and Mountain Home (Gassville), Arkansas, were tested by the respective manufacturers (enclosed statements) and met the specifications for Aviation Gasoline 100LL.

On August 2, 1995, the fuel metering unit and fuel manifold were examined (enclosed report) at the manufacturer and the foreign material on the manifold valve screen was estimated to "restrict less than 15 percent of the total screen area." The foreign material on the metering screen "may have been restricting about 25 percent of the total screen area." The foreign material fro