Overview
A mechanic had completed the installation of a rebuilt engine and was conducting a maintenance test flight with the pilot. According to the pilot, before starting the takeoff roll, he held the brakes, advanced the throttle, and held that position for about ten seconds.
Incident Description
As the airplane climbed through 400 feet above ground level, the pilot noticed a reduction in engine power. In response, the pilot lowered the nose of the airplane and turned on the boost pump. The engine regained power momentarily, allowing the pilot to continue the climb. However, seconds later the engine lost power again.
Forced Landing
The pilot attempted a forced landing on a paved road adjacent to the departure end of the runway. The landing was executed without further incident.
Examination
Following the event, an examination of the airplane failed to disclose any aircraft problem. The engine assembly operated normally during the functional examination, indicating no mechanical fault was found.
Conclusion
No probable cause was determined, as the power loss could not be replicated or attributed to any specific component failure.