The pilot was at the hold ready for departure when the airfield was closed because of an accident. He shut the aircraft down and opened the canopy. The airfield reopened after approximately three hours and the pilot repeated his pre-takeoff checks with the exception of a visual check of the canopy locks, which were behind his shoulders.
The canopy opened after takeoff and the pilot reported that he struggled to gain height despite using full power. He concentrated on flying the aircraft and commenced a left hand circuit to return to the runway. He reported that control difficulties due to the canopy being open prevented him from achieving a normal flare. The aircraft landed heavily, damaging the landing gear and propeller.
The pilot concluded that the canopy had been left unlocked and he had not identified the error because he did not check the locks before takeoff. He considered that he had not taken enough time to ensure the pre-takeoff checks were properly carried out and that, given the break, the checks should have be started again from the beginning, despite any time pressure.