Accident Briefs: April 2017

The commercial-rated pilot and passenger (who owned the airplane) were conducting a cross-country business flight. Several witnesses reported observing the accident airplane overhead; one witness stated that the engine made a "sputtering" sound like it was running out of gas. She stated that the airplane was flying north and then turned west when it began to "nose dive" out of sight.

A review of the radar data revealed that the airplane approached the destination airport from the southeast and proceeded north, tracking above the runway about 400 feet above ground level (AGL). The airplane then climbed to 900 feet AGLand continued northbound. About 8 miles north of the destination airport, the airplane was about 1,100 feet AGLand then entered a left turn and descended. The last radar point showed the airplane on a southwest heading and about 350 feet AGL. The airplane impacted the ground with its left wing low, cartwheeled to the right, and came to rest upright in a harvested cornfield. The main wreckage was found about 460 feet southwest of the last radar point.

The accident airplane likely encountered low-level wind shear and clear air turbulence and a wind shift that switched from a gusting headwind to a gusting tailwind in a short amount of time.

The right main fuel tank, which the selector valve indicated was selected at the time of the accident, was found empty and was not breached. The engine carburetor did not contain any fuel. A postaccident examination of the engine and airframe did not reveal any preimpact mechanical malfunctions or anomalies that would have precluded normal operation.

The pilot reported that the main tanks were full and the tip tanks were empty, so it is likely that the airplane contained 60 gallons of fuel before departure. The radar data revealed that the accident flight was 3 hours 16 minutes long. Based on the accident flight, the engine would have consumed about 40 gallons of fuel from initial taxi to the accident site. This should have left about 20 gallons remaining in the tanks, which would have been enough to fly to the destination airport in addition to reserve fuel.

The accident airplane was equipped with a single fuel quantity indicator gauge for the six fuel tanks; only one tank could be monitored at any given time. Switches on the instrument panel allowed the pilot to select which tank to monitor on the gauge. The pilot and airplane's new owner had limited experience in the airplane and with the airplane fuel indicating system, so they likely had the fuel indicator selected to another fuel tank and did not appropriately monitor the level of fuel in the right main tank, which was selected to feed the engine. Based on witness statements and the evidence obtained on-scene, it is likely that the engine was starved of available fuel. Once engine power was lost, the pilot then failed to maintain control of the airplane while flying in gusting wind and low-level wind shear conditions.

Probable Cause: The pilot's loss of airplane control in gusting wind conditions and low-level wind shear, following a loss of engine power due to fuel starvation. Contributing to the accident was the pilot's failure to properly monitor the fuel level inflight because of his unfamiliarity with the fuel system.

1 Uninjured

The pilot of the tailwheel-equipped biplane reported that during the takeoff sequence of a touch-and-go landing he decided to try a 2-point takeoff. He further reported that he was aware of the left turning tendency when raising the tail, however the "left turning factor happened much faster than [he] anticipated"; he was unable to recover with full right rudder inputs and the biplane veered to the left off the runway. During the runway excursion, the pilot brought the throttle to idle and the biplane impacted tumbleweeds.

The biplane sustained substantial damage to both right wings.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

Federal Aviation Administration's Airplane Flying Handbook, FAA-H-8083-3B (2016), contains a section titled "Normal Takeoff Roll" for tailwheel airplanes which states:

It is important to note that nose-down pitch movement produces left yaw, the result of gyroscopic precession created by the propeller. The amount of force created by this precession is directly related to the rate the propeller axis is tilted when the tail is raised, so it is best to avoid an abrupt pitch change. Whether smooth or abrupt, the need to react to this yaw with rudder inputs emphasizes the increased directional demands common to tailwheel airplanes, a demand likely to be unanticipated by pilots transitioning from nosewheel models.

Probable Cause: The pilot's failure to maintain directional control during takeoff, which resulted in a runway excursion.

3 Uninjured

The pilot of a tailwheel-equipped airplane reported that during the landing roll, he encountered a crosswind gust from the right. Subsequently, the airplane swerved off the runway to the right and ground looped. During the ground loop, the left wing and left horizontal stabilizer impacted the ground, which resulted in substantial damage.

The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation.

The pilot reported on the National Transportation Safety Board Accident/Incident Report Form 6120.1 the wind direction was variable at 8 to 9 knots, with gusts at 2 to 5 knots. The destination airport was not equipped with an automated weather observation system.

Probable Cause: The pilot's failure to maintain directional control during the landing roll in gusty crosswind conditions, which resulted in a runway excursion and a ground loop.