N46147Taylorcraft L-2M · 1943

On December 21, 2018, about 1330 Pacific standard time, a Taylorcraft L-2M airplane, N46147, was substantially damaged when it was involved in an accident near Walla Walla, Washington. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he departed with 16 gallons of fuel onboard and climbed to about 3,500 ft mean sea level (msl) at a 500 foot-per-minute (fpm) rate of climb. After experiencing about 30 minutes of rough air, the pilot climbed to 6,500 ft msl, also at a 500-fpm rate of climb, but could not find smooth air and returned to his original cruise altitude for the remainder of the flight. About 30 minutes from the destination, he noted that the fuel quantity gauges “showed low fuel,” but he thought that he had adequate fuel to make it to the airport. About 15 minutes from the destination, the engine "sputtered" and then lost all power. He verified that the oil temperature and pressure were normal and applied full throttle, rich mixture, carburetor heat, verified that the fuel selector was in the ON position, and that the magnetos were set to both. The pilot was unable to restore engine power and performed an off-airport landing to an open area. During the landing roll, the airplane nosed down and contacted the ground.

Examination of the airplane revealed substantial damage to the engine mounts and firewall. The recovery team that responded to the accident site reported that the fuel tanks and header tank were void of fuel and that the fuel system was not compromised.

The 1353 recorded weather observation at ALW included wind from 220° at 11 knots, 10 statute miles visibility, clear skies, temperature 06°C (43°F), dew point -01°C (30°F), and an altimeter setting of 30.13 inches of mercury.

The potential for carburetor ice was graphed using a carburetor ice chart from the Federal Aviation Administration's Special Airworthiness Information Bulletin CE-09-35, "Carburetor Ice Prevention," published on June 30, 2009. According to the chart, the airplane was at risk of serious icing at glide power and may have been at risk of serious icing at cruise power.

During a follow-up interview with the pilot, he reported that he may have experienced fuel exhaustion during the accident flight. According to the pilot, the previous owner informed him that the engine's average fuel consumption was 4 gallons per hour (gph); however, the pilot did not corroborate this information with another source, as the previous owner was experienced in building airplanes. Further, the owner also told the pilot that the airplane was equipped with two 6-gallon wing tanks and one 4-gallon header tank. The pilot fueled the airplane to capacity and completed his fuel performance computation based on a 16-gallon fuel capacity and 4 gph fuel consumption. The previous owner furnished the pilot with historical records for the accident airplane; however, a flight manual was not among them. The pilot's total flight time en route was 2 hrs and 15 minutes, and he recalled leaning the fuel/air mixture out during cruise flight.

A fuel performance computation was completed using the flight plan information provided by the pilot. The airplane was equipped with a Continental O-200, air-cooled, reciprocating engine. According to an industry expert, the fuel consumption for this make/model and engine configuration is 5-6 gph or more.

Additionally, the total fuel quantity for the airplane was 14 gallons, as the header tank's capacity was actually 2 gallons, not 4 gallons. Based on these values, the airplane would have burned about 1.2 gallons in the approximate 12 minutes that elapsed during takeoff and while climbing to 3,500 ft, and then 6,500 ft at a 500 fpm rate of climb. This would have left the pilot with 12.8 total gallons of fuel for the remaining 2 hours and 3 minutes of flight, which equates to a fuel consumption of about 6.4 gph.