The Transportation Safety Board is blaming carburetor icing for a helicopter crash that killed 29-year-old pilot Tiffany Hanna in November 2011.

The helicopter had departed the Region of Waterloo International Airport with Hanna and student Scott Puillandre, who was manning the controls, on board under cool but clear conditions.

But the Robinson R22 crashed into a drainage swamp about a minute after takeoff. Hanna was killed and Puillandre seriously injured.

The Transportation Safety Board (TSB) says the crash was caused by carburetor icing, which in turn caused the helicopter’s engine to fail.

According to the report “Environmental conditions were conducive to carburetor icing…The helicopter’s engine failed during departure most likely due to ice accumulation in the carburetor.”

Carburetor icing occurs when cold air enters a cold carburetor and forms ice, narrowing the flow through the carburetor and reducing power output.

A carburetor heating system is available to prevent this type of situation.

The TSB report says after reaching about 200 feet above the ground, Hanna told Puillandre to apply heat.

But it’s unclear if that happened and the TSB says the carburetor heat control knob was found in the cold position. Puillandre has said his memory of the crash isn’t clear.

After the engine shuddered, Hanna took control as the helicopter descended, swerving left and right.

But the TSB says the area where the helicopter was flying was surrounded by buildings and obstacles, making any emergency maneuver difficult to execute.

Hanna left behind two young sons and there has been an outpouring of support for the family since the crash.

Her death has also led to the approval of a number of recommendations to improve emergency response times after serious communications issues following the crash.