N6464VHelio H-295 · 1969

On September 16, 2016, about 0820 Alaska daylight time, a tundra tire-equipped Helio Courier H-295 airplane, N6464V, sustained substantial damage following a loss of control and subsequent runway excursion during takeoff from a remote, unimproved airstrip near Fairbanks, Alaska. The airplane was being operated by Wright Air Service, Fairbanks, Alaska, as a visual flight rules (VFR) on-demand commercial flight under the provisions of 14 Code of Federal Regulations (CFR) Part 135. The certificated airline transport pilot and one passenger were not injured. Visual meteorological conditions prevailed, and a VFR flight plan had been filed.

During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge on September 20, the pilot stated that everything seemed normal as he initiated the takeoff. About 300 feet into the takeoff roll, the airplane veered sharply to the left, exited the airstrip and impacted brush and trees, resulting in substantial damage to the fuselage and left horizontal stabilator.

The initial examination of the airplane, reported by the pilot, revealed that the tailwheel separated from its attach point and folded underneath the empennage. A trench was visible in the airstrip's surface that began about 300 feet from the point where the takeoff roll was initiated and continued to where the airplane impacted the brush and trees.

The tailwheel A-frame consisted of two arms extending forward of a flanged downtube, with a brace cross tube present between the two forward facing arms. The tailwheel A-frame was attached to the airframe at the forward ends of the arms, and to a shock absorber on the aft side of the down tube. Corner braces reinforced the attachments between the arms and the downtube. The corner brace between the left arm and the downtube was buckled and cracked, and the left arm was fractured where it was welded to the downtube. The tailwheel A-frame assembly was sent to the NTSB's Materials Laboratory in Washington D.C. for examination.

An NTSB Senior Materials Engineer reported that visual and magnified optical examinations of the fractures in the left arm revealed a matte gray fracture on slant planes consistent with a ductile overstress fracture. However, a portion of the fracture surface had a fracture in a plane perpendicular to the surface across most of the fracture with small shear lips present. Two areas had no shear lips at the surface and were oxidized with smooth curving boundaries, consistent with fatigue. The right arm had a crack that was opened in the laboratory. Examination of the fracture revealed that a portion of the fracture surface at the upper side of the right arm was on a plane perpendicular to the surface and was oxidized with curving black arrest lines, features consistent with fatigue. The remainder of the fracture surface had matte gray features on slant planes across the thickness of the arm wall. The fatigue regions in the left and right arms were up to 0.016 inch deep and 0.066 inch deep, respectively. The fracture surfaces where the brace tube between the arms had separated from the right arm were examined. The fracture features had matte gray features on slant planes consistent with ductile overstress fracture. In addition, fracture features where the shock absorber attachment ear fractured had features consistent with ductile overstress fracture. (Refer to the Materials Laboratory Factual Report in the public docket for further fracture information)

The closest weather reporting facility was Fairbanks International Airport, Fairbanks, Alaska, about 42 miles south of the accident site. At 0753, an aviation routine weather report (METAR) from Fairbanks Airport, was reporting in part: wind from 050° at 4 knots; visibility, 10 statute miles; sky condition, broken clouds 5,500 feet, broken clouds 7,500 feet, broken clouds 15,000 feet; temperature, 39° F; dew point 37° F; altimeter, 29.36 inHG.

On September 13, 2015, about 0840 Alaska daylight time, a tundra tire-equipped Helio Courier H-295 airplane, N6464V, sustained substantial damage during takeoff following a runway excursion from a remote unimproved airstrip near Delta Junction, AK. The airplane was being operated by Wright Air Service Fairbanks, Alaska, as a visual flight rules (VFR) on-demand charter flight under the provisions of 14 Code of Federal Regulations (CFR) 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. The flight departed a remote unimproved airstrip near Delta Junction, Alaska, at about 0840 destined for Fairbanks, AK.

During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) 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. He stated that 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 went on to state that following the accident he departed the airstrip in the same make and model airplane with a similar load and the airplane lifted off in about 600 feet. In addition, he stated that it was possible that 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.

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.

The airplane was equipped with a Lycoming GO-480-G1D6 engine, the pressure carburetor was replaced with a Bendix fuel injection system, under the 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 IIC, along with the rest of the investigative team. 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.

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 that joins 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.

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 was reporting, in part: wind calm; visibility, 10 statute miles; few clouds 1,000 feet, few clouds 13,000 feet, scattered clouds 17,000 feet, scattered clouds 20,000 feet; temperature, 28 degrees F; dew point 27 degrees F; altimeter, 30.14 inHG.