Pilot Initiated His “Climb” Checklist, During Which The Right Engine “Failed Hard.”

Location: Sandersville, Georgia Accident Number: ERA23LA320
Date & Time: August 1, 2023, 09:30 Local Registration: N106VT
Aircraft: Mesnard Velocity Twin Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial) Injuries: 1 Fatal, 1 Serious
Flight Conducted Under: Part 91: General aviation - Personal

Analysis: The pilot and the passenger of the twin-engine, amateur-built airplane were departing for on a cross-country flight, and the pilot reported that after completion of all checklists and ground run-ups the takeoff was normal. At 500 ft mean sea level the pilot initiated his “climb” checklist, during which the right engine “failed hard.” The airplane began to roll to the right and the pilot added left rudder to arrest the roll but was unable; he then added full left aileron, but the airplane continued to roll right. The pilot then performed what he described as a “low yo yo” maneuver and he was able to regain control of the airplane. He reduced throttle on both engines to idle before pitching to maintain 85 kts, which was the simulated single engine best rate of climb airspeed determined during flight testing. The pilot reported that he was too low to return to the airport and the airplane was not climbing while maintaining 85 kts. After scanning the immediate area, the pilot located a small clearing in a swamp and decided to make a forced landing. The airplane impacted a swampy area, substantially damaging the
fuselage, empennage, and both wings. 

Postaccident examination of both engines and the flight controls found no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. The lack of engine cylinder compression found on the right engine was likely due to corrosion, organic debris, and sediment entering the engine during the impact sequence and subsequent soaking in the swamp before recovery. Examination of the airplane’s wiring found the engine control unit (ECU) wiring from the ECU circuit breakers in the cockpit to the ECUs on the aft firewall was chafed and multiple wires were severed in the vicinity of the main landing gear actuator piston track. The wires were not shielded or protected and were clamped to the side of an undamaged covered channel where the landing gear actuator piston ran along with multiple other wires and the aileron control rod. One power wire for the left ECU was severed and both right ECU injector wires were severed. Multiple other wires in the same bundle exhibited cuts and chafing, likely a result of the main landing gear teeter bar rubbing against the wires when the landing gear was raised and lowered. The ECU manufacturer reported that with both right ECU injector wires severed, there would be no power to the electronic fuel injectors for the right engine and combustion would be lost. 

The pilot reported that during the accident flight he never attempted to feather the windmilling propeller of the right engine. Subsequently, the propeller controller would have continued to adjust the propeller blades to a fine pitch attitude in an attempt to maintain the set engine rpm until reaching the fine pitch stop. This adjustment towards fine pitch would greatly increase the drag produced by the propeller and it is likely the unexpected drag the pilot reported experiencing following the loss of engine power.

The pilot stated that during his flight testing of the airplane, he did not shut an engine down in flight nor did he feather a propeller in flight as he thought it was too much of a risk; instead, he simulated single-engine operations by reducing an engine to idle with the propeller set to cruise. All single-engine flight testing was done in this configuration to include Vmc, Vyse, and basic flight with a simulated loss of engine power to one engine. Due to the lack of flight testing with an engine shut down, the investigation was unable to determine why the pilot experienced a loss of control even though the airplane remained above the Vmc and Vyse noted by the pilot in his simulated single-engine testing.

Probable Cause and Findings: The National Transportation Safety Board determines the probable cause(s) of this accident to be -- A total loss of power in the right engine due to the right ECU injector wires being severed by the main landing gear actuator piston teeter bar as a result of a lack of clearance and protection of
the wiring bundle. 

FMI: www.ntsb.gov