Accident Overview
On March 2, 2021, at about 0747 eastern standard time, a Cessna P210N, registration N4629K, was substantially damaged in an accident near Johnstown, New York. The pilot, the sole occupant, was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot's Account
The pilot reported that approximately 30 minutes after reaching a cruise altitude of 10,000 ft above mean sea level, he began hearing an unfamiliar buzzing or humming noise that became progressively louder. Attempting to troubleshoot, he decided to divert to an airport along his route. Soon after, he detected the smell of electrical fumes and observed smoke in the cockpit. He informed the air traffic controller of the smoke and requested diversion to Fulton County Airport (NY0) in Johnstown, New York. He opened his window, descended toward the airport, listened to the local weather, and performed a landing checklist while entering the left downwind leg for runway 28. During the landing roll, the landing gear collapsed. The pilot attempted to maintain control, but the airplane skidded on the runway and tipped to the left, resulting in substantial damage to the left elevator.
Postaccident Examination
During a postaccident interview, the pilot stated that while he visually confirmed the landing gear was extended, he did not verify that the gear status light was green, indicating the gear were locked down, before landing. He and a mechanic examined the airplane and found that the circuit breaker for the hydraulic pump had popped and a hose near the hydraulic power pack assembly was partially melted. They subsequently removed the hydraulic power pack.
A postaccident examination under the supervision of a Federal Aviation Administration inspector revealed that the plastic sump jar attached to the hydraulic power pack was hanging in the center pedestal by its plumbing and was disfigured consistent with motor assembly overheating. The motor assembly showed signs of contact with the sump jar and had an odor of overheating. The hydraulic pressure switch wires appeared normal. Removal of floor panels revealed evidence of hydraulic fluid, though not enough to indicate an external system leak. No leaks were found in the main landing gear actuators and plumbing. The hydraulic pump motor contactor tested open with an Ohm meter. Because the hydraulic power pack had been removed by the pilot and mechanic, the hydraulic fluid level could not be determined, and no further testing was possible.
Aircraft System Description
The Pilot's Operating Handbook for the airplane described the landing gear system as using hydraulic actuators powered by an electrically driven hydraulic power pack. It specified that the system should be checked every 25 hours to ensure sufficient hydraulic fluid. A caution note stated: “If for any reason the hydraulic pump continues to run after gear cycle completion (up or down), the 30-amp circuit breaker . . . should be pulled out. This will shut off the hydraulic pump and prevent damage to the pump and motor.” During normal operation, placing the gear handle UP runs the pump to retract the gear; upon reaching the up position, hydraulic pressure builds until a pressure switch turns off the pump, trapping pressure. Placing the handle DOWN releases pressure, allowing the gear to free fall to a hanging position, and the pump then builds pressure in the extend lines to push the gear into the down and locked position. Insufficient pressure or fluid can result in the gear hanging down but not locking. A hand-operated hydraulic pump is provided for manual extension in case of hydraulic or electrical failure.
The handbook also included a landing gear malfunction procedure:
- Landing Gear Level – DOWN
- Emergency Hand Pump – EXTEND HANDLE and PUMP (perpendicular to handle until resistance becomes heavy – about 35 cycles)
- Gear Down Light – ON
- Pump Handle - STOW