On October 21, 2023, about 0828 central daylight time, a Powrachute LLC Pegasus powered parachute, N52631, sustained substantial damage when it was involved in an accident near Manhattan, Kansas. The pilot and passenger sustained serious injuries. The powered parachute was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that, before departure from his farm field, he installed a large heavy-duty deer feed bag that partially covered the radiator because he was concerned that the experimental engine would run “too cold” during the flight unless the radiator was partially covered. The radiator, located above the engine, sits aft and above the rear seat. The pilot reported that he departed on the local area flight with a full tank of fuel.

The experimental powered parachute was flying about 400 ft above ground level when the pilot noticed that the engine overheat light illuminated. The pilot decided to continue flying. Shortly after, the engine sustained a total loss of engine power. The pilot performed a forced landing to a road and the powered parachute came to rest upright on a grass embankment near the road. The powered parachute sustained substantial damage to the fuselage and the engine mount.

The postaccident examination revealed that the intact fuel tank was about 7/8 full of fuel with no fuel leaks observed on the airframe. Coolant was drained from the radiator, and the coolant appeared to be in a normal condition. The large heavy-duty deer feed bag was found covering about 3/4 of the radiator surface area and was secured with two bungee cords. The engine was rotated, internal engine continuity was confirmed, and engine compression was noted to meet minimum specifications.

According to the airframe and engine manufacturers, neither company has published any guidance on covering up the radiator for flight operations. According to the Rotax Aircraft Engines 582 UL Operator’s Manual, if an abnormal engine temperature is observed while in flight, “reduce engine power setting to the minimum necessary and carry out a precautionary landing.”

The Federal Aviation Administration Powered Parachute Flying Handbook FAA-H-8083-29 discusses radiators and states in part:

Liquid-cooled engines can overheat for a number of reasons, such as coolant not at proper levels, a leak, a failed water pump, or a blockage of the radiator. Operating an engine above its maximum design temperature can cause a loss of power and detonation. It will also lead to serious permanent damage, such as scoring the cylinder walls and damaging the pistons and rings. Monitor the engine temperature instruments to avoid high operating temperature.

Operating the engine lower than its designed temperature range can cause piston seizure and scarring on the cylinder walls. This happens most often in liquid-cooled powered parachutes in cold weather where large radiators designed for summer flying may need to be partially blocked off.