CHI04CA261 · Abbott RAF 2000

The amateur-built gyrocopter sustained substantial damage during a forced landing after takeoff. Prior to takeoff, the pilot had performed a 30-40 minute ground run to check the engine cooling system that had been modified prior to the flight. The pilot reported that the engine operating temperature during the ground run was 140 degrees F and there were no coolant leaks. The pilot reported that during the takeoff, the gyrocopter's climb performance was not as good as he had anticipated. By the end of runway, the gyrocopter had climbed to about 200 feet above ground level (agl), and the engine started to lose power. The pilot declared an emergency and attempted to return to the runway. The pilot reported that the gyrocopter "did not have enough altitude or speed to make a proper landing." The pilot landed the gyrocopter in a grassy area at the end of the runway. A visual inspection of the cylinders with a borescope revealed that both aft cylinders exhibited evidence of scoring and overheating. The gyrocopter pilot/owner had altered the engine cooling system by moving the radiator approximately four inches aft of its original location, because the engine operating temperature was higher than normal (190-200 degrees F). By moving the radiator aft, it moved the radiator further away from the engine exhaust system, and it provided for increased cooling system fluid capacity by lengthening the radiator hoses. The pilot/owner was unable to return all the coolant that he had drained from the radiator prior to the modification, back into the radiator after the modification was made. The cooling system modification was made at the advice of the airframe kit manufacturer, however, the pilot/owner was not a mechanic and he did not have the required cooling system service instructions available at the time the modification was made.

Verbatim NTSB analysis and probable cause from the NTSB dataset