Hendrickson Glasair 3

Full Narrative

On August 3, 2024, about 1125 eastern daylight time, an experimental, amateur-built Glasair 3 airplane, N121CH, was substantially damaged when it was involved in an accident near Oxford, Maine. The airline transport pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight.
The flight was the airplane’s seventh test flight in phase 1 of the amateur build. The purpose of the flight was to evaluate takeoff and landing performance. Following normal engine run-up and ground operations, the pilot departed from Oxford County Regional Airport (81B), Oxford, Maine, and conducted multiple takeoffs and landings at Auburn/Lewiston Municipal Airport (LEW), Auburn, Maine, and at 81B.
While on downwind leg of the airport traffic pattern at 81B, the pilot noted some engine roughness after reducing power to 25 inches manifold pressure. He attempted to troubleshoot the problem with the ignition switches and the fuel selector. After returning the magnetos to the BOTH position, the engine lost all power. He then turned the airplane toward the airport while again checking the ignition switches, then focused on performing a forced landing. After clearing some trees by extending the wing flaps, the pilot landed the airplane on the perimeter road, where it collided with a fence and came to rest in grass near the departure end of runway 33. The airplane sustained substantial damage to the wings and fuselage; the landing gear separated during the forced landing.
Federal Aviation Administration (FAA) inspectors performed a postaccident examination of the airplane. The fuel selector was placed in the header tank position and fuel flow was observed from the firewall-mounted gascolator. The observed flow rate appeared adequate to provide the engine with sufficient fuel flow to sustain power. Fuel was drained into a clear container and visually inspected for debris and contamination. No debris or contamination was noted. The engine throttle, mixture, and propeller control cables operated smoothly and freely throughout their full range of motion.
The ignition switch was tested with a digital multimeter. Both magneto P-leads from the airframe were present and operated properly. Additionally, the ignition switch wiring and associated wiring connections were visually inspected. Wiring associated with the ignition system appeared secure, properly connected, and serviceable with no obvious loose, frayed, or damaged wiring observed during the inspection.
Flight control continuity was verified for the ailerons, elevator, and rudder. All corresponding cockpit controls operated freely throughout the observed range of motion and maintained continuity to their respective control surfaces.
Postaccident examination of the airframe revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.
Review of engine data provided by the mechanic showed that during the flight, fuel flow and manifold pressure adjustments matched until the end of the flight when the fuel flow seemed to remain at around 33 gallons per hour, even after the engine rpm had come to a complete stop.

The engine was shipped to the manufacturer for examination and testing. The engine mounts were removed and the top two were fragmented from impact forces. Replacement engine mounts were then installed to facilitate an engine test run. The upper plugs were removed, the crankshaft was rotated a full 360° multiple times, compression and suction were observed on all cylinders in the correct firing order, and the impulse coupling could be heard snapping, confirming mechanical continuity throughout the engine. The No. 2 rocker box cover was removed and the crankshaft-to-camshaft timing was confirmed. The magnetos were timed at 23° before top center (BTC); the engine’s data tag shows the magneto timing should be 20° BTC. No damage was observed to the ignition leads. The sparkplugs were all finger tight; the electrodes were not worn, were black in color, and exhibited a carbon fouling condition per the Champion Aviation Check-A-Plug Chart AV-27. During the engine run, the rpm drops were within limits when testing the magnetos, 86.5 - 94.2 on both sides.
No contamination was observed on the fuel inlet screen. The fuel pump remained secure to the accessory housing and the inlet and outlet fittings were in place. The engine-driven fuel pump produced within-limit fuel pressure during the engine run.
The oil filter was removed and cut open. No metal particles were observed in the pleats of the oil filter element. The oil suction screen was not removed for examination.
Two engine runs were performed on consecutive days; in both runs, the engine passed the production test. Fuel flow fluctuation was observed during full rated power operation; however, once the fuel tank pump was turned on, which applies 5 psi from the tank to the inlet of the engine-driven fuel pump, the fuel flow stabilized. The fuel flow transducer remained installed during the first run, and during the second run it was replaced with a union. Air was blown through the transducer, which was unobstructed and the paddle wheel could be heard spinning.