Background
On August 23, 2020, a Cessna 150 (registration SP-WRO) was conducting training flights for the Private Pilot License (PPL(A)) at Wrocław Airport (EPWR). The crew was performing navigation exercises as part of Training Task C4, which included entry and landing at the controlled airport.
Incident Description
During the first takeoff from Runway 29, at an altitude of approximately 500–600 feet, engine rpm dropped by 200–300 rpm. The crew declared an emergency and requested landing on Runway 11. The landing was executed without any consequences. After taxiing to the apron, the engine parameters were checked and found to be within normal limits. Following coordination with Wrocław Tower, a decision was made to attempt another takeoff from Runway 29. The second takeoff and initial climb proceeded normally until reaching about 400–500 feet, when engine rpm again dropped by 200–330 rpm. The crew again decided to land on Runway 11, and the landing was completed without further issues.
Investigation and Cause
A subsequent engine inspection revealed a burned exhaust valve in cylinder number 4. The exhaust valve burn caused a loss of combustion chamber seal, leading to reduced compression during the compression stroke and consequently a decrease in engine rpm. The investigation determined that the cause of the incident was the exhaust valve burn, which resulted in compression loss in cylinder 4 and an eventual drop in engine rpm. No contributing circumstances were identified.