DEN99LA042

The airplane had been cruising at 16,000 feet and fuel had been drawn from the left tank for one hour. Approximately 30 seconds after the pilot switched the fuel selector valve from the left main to the right tip tank, the engine lost power. The pilot was able to glide the airplane 10 miles to the Telluride Regional Airport, elevation 9,078 feet msl, but struck the ground about 30 feet short of the runway. The tips tanks were last used 16 months before the accident. The tip tank manufacturer said it was possible that trapped air in the tip tank fuel line could have caused the engine to lose power when the pilot moved the fuel selector to the right tip tank, and it was also possible the pilot flooded the engine with excess fuel when she selected LOW BOOST during the restart attempt. The pilot was unaware of the procedure to follow for purging air from the fuel system.

On February 22, 1999, at 1025 mountain standard time, a Beech V35, N345MD, was destroyed when it lost engine power and landed short of the runway at Telluride, Colorado. The private pilot and two passengers received minor injuries, and one passenger sustained serious injuries. Visual meteorological conditions prevailed, and an IFR flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at Steamboat Springs, Colorado, at 0924.

According to the pilot, both main tanks were filled to capacity and 10 gallons were added to each tip tank on the evening before the accident. According to the stenciled placards on the fuel tanks, each main tank holds 40 gallons (37 gallons usable), and each tip tank holds 20 gallons. The pilot said before fuel was added to the tip tanks, she noticed there was about one or two gallons in each tank.

The pilot and her passengers departed Steamboat Springs, Colorado, on an IFR flight plan to Tucson, Arizona. The airplane had been cruising at 16,000 feet and fuel had been drawn from the left main tank "for 62 minutes" to allow space for returning fuel vapors. The pilot then moved the fuel selector valve to the right tip tank. Approximately 30 seconds later, the engine lost power. She moved the fuel selector valve to the right main tank and switched the electric fuel pump to LOW BOOST. She said she did not readjust the fuel mixture, which had been set for a fuel flow of 15.2 gallons per hour. The pilot declared an emergency with ATC, and glided towards Telluride Regional Airport, elevation 9,078 feet msl, about 10 miles away. The pilot said she lowered the landing gear, but the airplane struck the ground seconds later about 30 feet short of the runway. The airplane slid up onto the runway and collided with a snow bank.

On March 4, the engine and fuel system were functionally tested at the facilities of Beegles Aircraft Service in Greeley, Colorado. Examination of fuel samples that had been drained from each tank disclosed no evidence of water or other contaminants. The fuel was clear and blue in color. Damage precluded use of the right wing, so fuel lines from the left main and tip tanks were connected to the fuel selector valve. Because of the damaged engine mounts, no more than 1,500 rpm was possible. After the engine had run for a few minutes, it was secured. Compressed air was forced into each port in the fuel selector valve and continuity was established. Drawing fuel from the left main tank, the engine was restarted. The fuel selector valve was then moved to the left tip tank. About 20 seconds later, the engine lost power.

According to the pilot, the last time she used the tips tanks was in October 1997.

According to a spokesman for Osborne Tank and Supply (formerly Brittain Industries), manufacturer of the airplane tip tanks, it was possible that air had been drawn into the fuel lines when the tip tanks contained 1 or 2 gallons of fuel, and had become trapped when additional fuel was added the evening before the accident. This would have caused the engine to lose power when the pilot moved the fuel selector to the right tip tank. Power should have been restored when the pilot moved the fuel selector to the right main tank, but the spokesman said it was also possible she may have flooded the engine with excess fuel when she selected LOW BOOST.

The spokesman said that the Supplemental Flight Manual gives instructions on how to purge the tip tanks of trapped air:

"12.4 . . .air may be trapped in the line when tip tanks are subsequently filled. This air pocket in the line may prevent feeding of fuel from the tip tanks. To avoid this condition, operate the power plant from each wing tip tank separately until steady fuel flow is assured during ground run-up prior to flight. Use engine boost pump (low boost on turbo charged engines) if required during fuel switch-over" (emphasis added).

The pilot was asked if she had purged the tip tanks prior to takeoff. She said she was unaware of this procedure.