Date: 202010
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Sail Plane
Operator: Other Flight School
Operating under: Part 91
Flight plan: VFR
Mission: Training
Flight phase: Final Approach
Airspace: Class G ZZZ
ATC / advisory: CTAF ZZZ
Aircraft component: Cockpit Canopy Window
Component problem: Failed
Reporter organization: Other Flight School
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: While conducting a CFI checkout in a Grob-103C; the canopy came open and separated from the aircraft during final approach with a forward slip.This was my second training flight in the glider; the purpose of the checkout was to allow me to provide flight instruction in the Grob-103C. I normally provide instruction in Aircraft Y. The Grob-103C we were flying was recently inspected - 100-Hour and Annual - and was flying frequently at the flight school. Before flight; we performed our standard pre-flight inspection and pre-takeoff checklist which included ensuring both canopies were closed and locked. I was seated in the front seat; having flown side secured canopies often; [I] closed the canopy latch and tested the canopy by pushing up on the side to ensure it was securely closed. I noted no problems during closing and locking the canopy.After executing our pre-takeoff procedure; my Instructor and I proceeded on aerotow to 3;000 AGL; released; and performed some basic maneuvers - stalls; slow flight; and thermalling. After gliding for approximately 15 minutes; we elected to enter the pattern on the downwind leg. While turning from base to final; we decided to slip the aircraft to practice flying without airbrakes. After slipping for approximately 8 seconds; the front canopy suddenly opened and departed the aircraft. I immediately came out of the slip; nosed down for approach speed; and opened the airbrakes. I was able to land the glider with normal maneuvers and noted no change to the controllability of the glider.Upon examination of the glider; there was no structural/significant damage. There were no injuries to either crew. There was a slight score to the fiberglass on the right wing and damage to the canopy hinges. The canopy was later recovered in a field where the fiberglass appeared to have shattered on impact. Analyzing the situation; I am still unsure why the canopy separation occurred; but if I could improve my process; I would have examined the canopy all along its edges after securing the latch to insure there were no gaps or leaks. In addition; I probably would have looked closer during preflight at the edges/seals of the canopy from the exterior to ensure there were no abnormalities on either canopy when closed and locked.




Synopsis: Sailplane Flight Instructor reported a canopy separation mid-flight resulting in a return to the departure airport.