N125MCTomash James MT COYOTE

On July 22, 2020, at 1915 Pacific daylight time, an experimental amateur built Montana Coyote airplane, N125MC, was substantially damaged when it was involved in an accident near Jamul, California. The pilot and pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot-rated passenger, who was also the owner of the accident airplane, after an uneventful 30-minute flight they landed at a nearby airport and refueled. The pilot reported that they filled the fuel tanks to their full capacity during this time, which totaled 24 gallons. The pilot-rated passenger stated that during their subsequent climb out he observed that the climb rate had decreased from 1,100 fpm to 700 fpm and attributed this to the additional fuel weight as the engine sounded normal. According to the pilot, the engine power then began to fluctuate about 30 minutes into the flight. During this time, he observed the engine power decrease by about 200 rpm and immediately return to full power. The engine lost all power seconds after the power fluctuation.

The pilot immediately began searching for a suitable landing site from about 700 ft above ground level (agl). He observed the mixture control in the full rich position as the airplane descended rapidly. The pilot elected to land in a meadow directly in front of him. He deployed full wing flaps as the airplane descended through 100 ft agl and positioned the airplane to touchdown between power poles and barbed wire fence. During the final moments of their descent, the pilot observed the tops of boulders that were in his touchdown path. He turned the airplane 20° right to avoid the boulders and touched down on the tailwheel first and rolled 75 ft before it impacted fence posts. The left main landing gear collapsed, and the airplane skidded another 75 ft before it came to rest.

Postaccident photographs furnished by the Federal Aviation Administration (FAA) showed substantial damage to the left wing. According to first responders, the airplane’s fuel tanks were not breached and were nearly full of fuel when they arrived the night of the accident.

The wreckage was sold to a new owner before the airplane could be examined by federal investigators. According to the new owner, the airplane was equipped with right- and left-wing fuel tanks that drained unfiltered fuel into a header tank through separate fuel lines. The combined fuel was then directed to the fuel gascolator and subsequently to the engine through the carburetor. During his inspection of the accident airplane, he discovered a complete fuel obstruction at the fitting that connected the hose from the fuel header tank to the engine (see figure 1). At the time he observed that the drain plug (the middle fitting in figure 1) was 100% obstructed with dark red deposits. Figure 1 does not show the complete obstruction, which separated after the new owner slammed the fitting on a table.

Figure 1: Header Tank Fuel Line Fittings

According to the new owner, a conditional inspection was completed on the airplane March 9, 2006, at 71.8 tachometer hours. The airplane maintenance records provided to investigators comprised one maintenance entry since 2006, which was annotated as a pre-purchase annual inspection that was signed off August 18, 2019, at 72.4 hrs total time. The inspection annotation did not indicate that the fuel system had ever been modified or inspected. Although the inspection was noted as an “Annual Inspection,” the entry did not follow the Phase 2 operating limitations that were established by the FAA for this airplane on July 19, 1991, which required the endorsement to state,

“I certify that this aircraft has been inspected on (insert date) in accordance with the scope and detail of Appendix D of FAR 43 and found to be in condition for safe operation.”

Appendix D of FAR 43 did not specifically require an inspection of the fuel system for blockages at the time of the accident. It did, however, state,

(b) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the fuselage and hull group:

(2) Systems and components - for improper installation, apparent defects, and unsatisfactory operation.

An NTSB materials laboratory chemical analysis revealed that the red material was chemically similar to several surfactants and antioxidants. These materials are typically used in fuel additives. Based on the color, consistency, and chemical composition, the material on the fittings was consistent with old/evaporated fuel; however, the fuel type could not be determined.