CEN20LA262

While in cruise flight and after the pilot engaged the autopilot, a portable air conditioning unit was plugged into the airplane’s electrical system. When the unit was plugged into the system, the pilot heard a loud noise like a “firecracker” from the engine compartment, and the autopilot disengaged. The pilot ran the emergency checklist for an electrical failure and noticed a drop in engine rpm. Attempts to rectify the electrical issue and regain engine rpms were unsuccessful. The pilot located a private 3,000 ft grass airstrip to land on. As he approached the airstrip, he noticed a stack of large round hay bales on the edge of the runway. The pilot felt that trying to pull up over the bales would induce a stall, so he turned to the right just as the airplane touched down. About 100 ft after the airplane touched down, the left wing impacted the hay bales, which caused the airplane to spin left and come to a sudden stop. The airplane sustained substantial damage to the left wing. A postaccident examination of the airplane electrical systems did not determine the reasons for the reported electrical problems. The examination of the engine revealed that it was poorly maintained; however, it was not clear if this condition resulted in the loss of engine rpm or if the loss in rpm was related to the electrical system.

On July 4, 2020, about 2200 central daylight time, a Beech F35 airplane, N4219B, was substantially damaged when it was involved in an accident near Ravenna, Texas. The pilot sustained minor injuries and passenger was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The flight originated at Stan Stamper Municipal Airport (HHW), Hugo, Oklahoma, about 1915. According to the pilot, the engine run-up and departure were normal with no anomalies with the airplane in the beginning of the flight. Shortly after the airplane reached cruising altitude and the pilot engaged the autopilot, the pilot instructed the passenger to plug in the "icebox cooler" they had brought along for in-flight air conditioning. He explained they had used the cooler on the previous flight to Oklahoma from its built-in battery, but the battery capacity in the cooler was low so it would require 12 volts from the airplane's system to operate. When the 12-volt plug was inserted into the airplane's 12-volt outlet, the pilot heard a loud pop, or a “firecracker” sound, from under the engine cowling. At that time, the autopilot disengaged, and the airplane pitched up. The pilot instructed the passenger to push the nose down to avoid a stall while he completed the airplane’s "Electrical System Failure" checklist. He noted no circuit breakers were popped. As the airplane’s nose was lowered, the pilot reached under the dash to manually re-trim the pitch wheel to an increased nose-down position. As the airplane regained airspeed, he noticed a drop in engine rpm. The pilot advanced the throttle, changed the fuel selector to the left main tank, and cycled each magneto on and off, with no change in engine performance noted. The pilot used a GPS to find the nearest airport, which was a private 3,000 ft grass airstrip located about 4.5 miles from his location. The pilot waited until they were closer to the airstrip to begin the manual extension of the landing gear. With the landing gear down and locked, he entered the traffic pattern for a right downwind to the north runway but was unable to extend the electrical flaps. He subsequently had to break off his base leg and aim for a landing on the “numbers.” As he approached the runway into the sun, he noticed about 10 large round hay bales stacked 8 ft tall on the edge of the runway. The pilot felt that trying to pull up over the bales would induce a stall, so he turned to the right just as the airplane touched down. About 100 ft after the airplane touched down, the left wing impacted the stack of hay bales, and the airplane spun left and came to a sudden stop. The airplane sustained substantial damage to the left wing. Postaccident examination of the airplane by a mechanic revealed no anomalies with the airplane’s electrical system. The engine examination revealed low compression on all cylinders. The spark plugs were “badly worn,” and the fuel screen was 80% clogged. The mechanic reportedthat “a cause [of the electrical failure] could not be determined because everything operated properly.” Several attempts to obtain a completed National Transportation Safety Board Pilot/Operator Accident Report (Form 6120.1) and the maintenance records for the airplane were unsuccessful.