Accident Overview
On September 13, 2015, at approximately 0840 Alaska daylight time, a Helio Courier H-295 airplane, registration N6464V, sustained substantial damage during takeoff from a remote unimproved airstrip near Delta Junction, Alaska. The airplane was operated by Wright Air Service of Fairbanks, Alaska, as a visual flight rules (VFR) on-demand charter flight under 14 Code of Federal Regulations Part 135. The certificated airline transport pilot and two passengers were not injured. Visual meteorological conditions prevailed, and a VFR flight plan had been filed.
Pilot Statement
During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge on September 14, the pilot stated that he was departing from a remote unimproved airstrip estimated to be about 850 feet long, with 800 feet usable. The airplane seemed to accelerate normally, but failed to become airborne at the departure end of the runway, and impacted brush and trees, sustaining substantial damage to the right wing.
In the recommendation section of the NTSB Accident/Incident Reporting Form 6120.1, the pilot further stated that following the accident, he departed the same airstrip in the same make and model airplane with a similar load, and the airplane lifted off in about 600 feet. He also stated that it was possible the engine was not producing full power even though the RPM was at redline, and there were no sounds associated with missing or a power reduction.
Performance Data
A Helio Courier training manual dated October 1968 provided a Takeoff Distance vs Density Altitude chart for hard surfaced runways, which included a ground run correction factor for wet grass and soft turf. At a density altitude of about 928 feet and a gross weight of about 3,340 pounds, the takeoff ground run with the wet grass correction factor was about 480 feet.
Engine Examination
The airplane was equipped with a Lycoming GO-480-G1D6 engine, and the pressure carburetor had been replaced with a Bendix fuel injection system under a Federal Aviation Administration (FAA) field approval process.
On October 2, the engine, while still mounted on the accident airplane's airframe, was operated under the direction of the NTSB investigator-in-charge. The engine ran without any observed anomalies and produced full factory specified RPM. A drop of about 25 RPM was noted for the left and right magnetos. A series of power adjustments from idle to full power were conducted with no hesitation in engine operation noted.
Maintenance Findings
An aviation safety inspector from the Flight Standards Division, System Safety and Analysis Branch inspected the accident airplane following the engine run and noted that the scat tube joining the air box assembly to the air filter assembly was not secured to the filter assembly with the hose clamp as depicted in the Helio Courier parts manual.
Weather Conditions
The closest weather reporting facility was Allen Army Airfield, about 35 miles northeast of the accident site. At 0853, a weather observation from Allen Army Airfield reported: wind calm; visibility 10 statute miles; few clouds at 1,000 feet, few clouds at 13,000 feet, scattered clouds at 17,000 feet, scattered clouds at 20,000 feet; temperature 28 degrees Fahrenheit; dew point 27 degrees Fahrenheit; altimeter 30.14 inches of mercury.