Schweizer 2-33A Glider C-GCSK - Epilogue

Report / May 16, 2015 / Project number: Schweizer C-GCSK - B Category

Location: Lachute, Quebec
Date: 2015-05-16
Status: Investigation Complete

The accident occurred during a training flight in support of the Air Cadet Gliding Program. The flight was to be part of the Annual Proficiency Check for a pilot working towards becoming a passenger-carrying qualified cadet. The accident occurred during the initial climb out on aero-tow with an O-1 Superdog and a Schweizer 2-33A glider used for training and familiarization of cadets.

The initial take-off sequence progressed normally until the aircraft reached a position above the Alpha-taxiway, at which time a momentary partial loss of power was felt. When they reached 100 feet AGL, the tow plane experienced another partial loss of power and felt a reduction in climb rate.

The glider was too low and too far for a 180° turn back to the runway and there were no good options for an off field landing. A soccer field was noted off to the right and the glider instructor opted to release at a speed of about 45 mph and a height of around 100 feet AGL, less than 50 feet above the trees, to try for the field. Immediately following the release, the soccer field was hidden behind the tree tops. The glider instructor turned in the direction of the soccer field when the right wing suddenly dropped. The glider instructor tried to apply opposite aileron but there was no reaction from the glider. The glider made contact with the trees, dropped nose down towards the ground and came to a sudden stop when the nose of the glider impacted the soft earthen floor of the wooded area.

Once the glider released, the tow plane was able to return and land at the airfield. Communication with the glider was established quickly and the glider instructor confirmed they were "OK". The glider damage was assessed as very serious (Category-B), and one of the glider crew suffered minor injury.

The investigation determined two possible causes for the tow plane loss of power. First, the carburetor flapper valve rigging was such that it allowed the hinge assembly in the heat box to open, essentially activating the alternate air (heated air) to be fed to the carburetor, causing a loss of power. Second, the tow plane was operated under various icing conditions throughout the day, and carburetor icing may have caused a loss of power. It could not be determined with certitude in what proportion each of the two scenarios actually contributed to this accident.

Preventive measures included a modification on the entire Superdog fleet to replace the carburetor heat box, and tools are to be developed to better equip tow plane pilots to assess conditions of icing during operations.

The occurrence involved a glider and a tow plane, and this report includes a review of the entire sequence of events involving both aircraft.

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