Accident Overview
A Robinson R22 helicopter, registration C-GVAR and serial number 2110, departed the Region of Waterloo International Airport in Ontario for a local training flight with a student and an instructor on board. At 1131 Eastern Standard Time, approximately one minute after takeoff, the helicopter crashed in a drainage swamp on airport property. The instructor sustained fatal injuries, and the student was seriously injured. The helicopter was destroyed by impact forces; there was no post-impact fire. The emergency locator transmitter did transmit a signal.
Pre-Flight and Departure
The flight was planned as a basic navigation training exercise extending about 28 miles southwest of the airport. The pre-flight inspection, start-up, and engine run-up were completed near the company's hangar, located west of the air traffic control tower. Buildings blocked the tower's view of the hangar area, so company procedure required repositioning (air taxi) after run-up to a departure area south of the approach path to Runway 08. After C-GVAR moved to the grassy departure area, there was a short delay due to tower frequency congestion. During this five-minute period, the crew practiced touchdowns and lift-offs from a hover. At 1130, the air traffic controller instructed C-GVAR to lift off at the crew's discretion and make a turn around the control tower for a southbound departure.
Engine Failure and Circumstances
The helicopter's engine was not running at impact, although no mechanical anomalies were found that would have prevented its operation. The weather conditions at the airport were highly conducive to carburetor icing. The temperature/dew point spread, combined with operations over wet grass, would have intensified the rate of ice accumulation. The investigation could not determine whether the carburetor heat control was adjusted as required during the hover over wet grass or during takeoff; however, when the helicopter struck the ground, the carburetor heat was selected to cold. This could have resulted from not applying carburetor heat, or if ice had already formed and caused a rough-running engine, the carburetor heat may have been de-selected. In either case, the engine likely stopped due to ice blocking airflow through the carburetor.
The possibility that the mixture control was inadvertently selected to idle cut-off was considered unlikely, as the student would have had to remove the mixture guard, pull the control to idle cut-off, and return it to full rich without instructor intervention. The carburetor heat being in the cold position further suggested this scenario was unlikely.
Descent and Collision
At the time of engine failure, the helicopter was at low altitude over a group of hangars with multiple overhead wires strung between numerous poles. The closest obstacle-free spot was a field 60 feet beyond the crash location. The quick yawing following engine failure likely resulted from torque changes due to power loss, which decreased forward velocity and increased the angle of descent. In an attempt to decrease the descent angle and reach the field, the pilot likely raised the collective, causing rotor rpm to decrease to a point where flight could no longer be sustained. The helicopter subsequently fell almost vertically into the swamp, short of the field.
Findings
The Transportation Safety Board determined that environmental conditions were conducive to serious carburetor icing, but it could not be determined if carburetor heat was applied. The engine failed during departure most likely due to ice accumulation in the carburetor. The departure path took the helicopter over buildings and obstacles that would have made a successful autorotation difficult. The pilot likely raised the collective in an attempt to reach a suitable field, causing rotor rpm to decay to a point where flight could no longer be sustained, and the helicopter fell almost vertically into the swamp.