Event Description
A Mooney M20F aircraft departed on a flight. As the pilot turned crosswind after takeoff, a partial loss of engine power occurred. The pilot executed a return to the departure airport and landed without further incident. On the ground, the engine operated smoothly, and the pilot conducted extensive ground runs without being able to replicate the power loss. The pilot did not arrange for maintenance personnel to inspect the aircraft before the next flight.
On a subsequent takeoff, the engine again lost power. This time, the pilot performed an off-airport landing in a field.
Engine Examination
Following the off-airport landing, an examination of the engine was conducted. The spark plugs were found to have soot deposits. The fuel injector servo, manifold, and nozzles were checked and found to be functioning normally. However, the rubber intake boot located between the air filter and the fuel servo was discovered to be partially collapsed.