Narrative:

My preflight that day was normal. It was to be my 3rd practice flight of the day flying in the aerobatic box. The flights generally last about 20 minutes on average.exterior preflight - I check and top fluids before and after each flight; as was the case on this flight. Check secure oil door. I check my control linkages and hinges. I check the control surface attach points for signs of mechanical stress. I check my spades for security. I check my wheel pants for security and tire inflation. I check my prop for signs of structural failure and seal leakage. I check all skins for missing screws during the walk-around.interior preflight - prep pilot seat belts. Check and put on parachute. Enter cockpit and secure belts. Put on headset. Set altimeter to zero feet. Reset G meter. Close canopy. Startup - check fuel valve on center tank. Full rich. Full throttle. Master on. Primer pump on till fuel lines pressurized then pump off. Throttle open .375'. Fuel mixture lean cut-off. Clear prop and crank. Set mixture as required when engine fires. Set rpm and warm engine as necessary while studying flight sequence card. For this flight; I performed my standard warm engine run-up. Set brakes; 1800 RPM and do mag check twice to confirm <50 rpm drop both mags. Check oil pressure and oil temp green. Close throttle and check idle. Set RPM to 1000-1050.tower cleared me for takeoff; early right turn; frequency change approved. I repeated the instructions and proceeded to taxi into position for takeoff. I lined up; checked mixture; gauges; and then throttled up.a few seconds into the 2900 RPM throttle up; I noticed the canopy lift and separate. I recall the canopy exiting towards the rear of the aircraft maintaining contact along the right side of the airplane. I recall the apparent trajectory and angle of the departing canopy requiring a spontaneous and reasonably rapid posture adjustment to avoid contact with the part. As all of this was happening the aircraft veered left towards the grass. I recall quickly assessing the situation. I surmised that I was unable maintain alignment with the runway and any serious attempt to do so would likely result in balling the aircraft up via a ground loop. I decided to ride it out straight ahead into the grass for best personal and aircraft safety options. I recall maintaining aft elevator and appropriate rudder in order to maintain straight ahead direction as best I could on the relatively rough terrain in an aircraft not designed for such conditions. I was unable to see the signage due to the limited forward visibility; however; I do recall striking was eventually became known as an airport runway sign. The aircraft came to a stop in the grass with the engine idling. I shut off the master; mags; and fuel; and exited the aircraft; stunned.I've thought back through from beginning to end; and I don't recall doing anything different during this flight than the previous 250 flights in this airplane. The absolute shock of what was happening caused the event; which probably lasted 20 seconds; to get blurry. I recall taking a few seconds to process the situation; which inevitably escalated during that time. If I could change anything it would be to have triple checked the canopy latch and to have been able to close the throttle a few second earlier. Perhaps I could have maintained contact with the runway instead of entering the grass.

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Original NASA ASRS Text

Title: The Pilot of an aerobatic monoplane reported the canopy flew off during takeoff roll.

Narrative: My preflight that day was normal. It was to be my 3rd practice flight of the day flying in the aerobatic box. The flights generally last about 20 minutes on average.Exterior preflight - I check and top fluids before and after each flight; as was the case on this flight. Check secure oil door. I check my control linkages and hinges. I check the control surface attach points for signs of mechanical stress. I check my spades for security. I check my wheel pants for security and tire inflation. I check my prop for signs of structural failure and seal leakage. I check all skins for missing screws during the walk-around.Interior preflight - Prep pilot seat belts. Check and put on parachute. Enter cockpit and secure belts. Put on headset. Set altimeter to zero feet. Reset G meter. Close canopy. Startup - check fuel valve on center tank. Full rich. Full throttle. Master on. Primer pump on till fuel lines pressurized then pump off. Throttle open .375'. Fuel mixture lean cut-off. Clear prop and crank. Set mixture as required when engine fires. Set rpm and warm engine as necessary while studying flight sequence card. For this flight; I performed my standard warm engine run-up. Set brakes; 1800 RPM and do mag check twice to confirm <50 rpm drop both mags. Check oil pressure and oil temp green. Close throttle and check idle. Set RPM to 1000-1050.Tower cleared me for takeoff; early right turn; frequency change approved. I repeated the instructions and proceeded to taxi into position for takeoff. I lined up; checked mixture; gauges; and then throttled up.A few seconds into the 2900 RPM throttle up; I noticed the canopy lift and separate. I recall the canopy exiting towards the rear of the aircraft maintaining contact along the right side of the airplane. I recall the apparent trajectory and angle of the departing canopy requiring a spontaneous and reasonably rapid posture adjustment to avoid contact with the part. As all of this was happening the aircraft veered left towards the grass. I recall quickly assessing the situation. I surmised that I was unable maintain alignment with the runway and any serious attempt to do so would likely result in balling the aircraft up via a ground loop. I decided to ride it out straight ahead into the grass for best personal and aircraft safety options. I recall maintaining aft elevator and appropriate rudder in order to maintain straight ahead direction as best I could on the relatively rough terrain in an aircraft not designed for such conditions. I was unable to see the signage due to the limited forward visibility; however; I do recall striking was eventually became known as an airport runway sign. The aircraft came to a stop in the grass with the engine idling. I shut off the master; mags; and fuel; and exited the aircraft; stunned.I've thought back through from beginning to end; and I don't recall doing anything different during this flight than the previous 250 flights in this airplane. The absolute shock of what was happening caused the event; which probably lasted 20 seconds; to get blurry. I recall taking a few seconds to process the situation; which inevitably escalated during that time. If I could change anything it would be to have triple checked the canopy latch and to have been able to close the throttle a few second earlier. Perhaps I could have maintained contact with the runway instead of entering the grass.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.