What happened
During the daylight hours of an afternoon in 2001, a Cessna 3/7 performing a highway traffic reporting mission collided with a Cessna 172 training aircraft. The incident occurred approximately 18 nautical miles northeast of Toronto/City Centre Airport within a high-density Visual Flight Rules (VFR) corridor.
The Cessna 337, registration C-GZYO, was orbiting at 2,000 feet while the pilot monitored ground traffic. Simultaneously, a Cessna 172, registration C-GSAR, was descending through the same area during a flight lesson involving an instructor and a student. As the Cessna 337 executed a left turn, it passed beneath the descending Cessna 172. The nose gear of the Cessna 172 struck the left vertical stabilizer of the Cessna 337, causing roughly half of the stabilizer and the left rudder to separate from the larger aircraft.
Following the impact, the instructor in the Cessna 172 believed the aircraft had merely encountered turbulence and proceeded to land safely at Toronto/City Centre Airport. The pilot of the Cessna 337 realized a collision had occurred but did not immediately notify the other aircraft or air traffic control. After performing controllability checks, the pilot returned to Toronto/Buttonville Municipal Airport to land.
The investigation
The investigation examined the operational environment, the equipment on board, and the actions taken by both crews. The collision took place in Class E airspace, where air traffic control does not provide separation or traffic information to VFR aircraft. The investigation noted that the two aircraft were monitoring different radio frequencies, preventing direct communication.
Investigators also reviewed the workload of the Cessna 337 pilot, who was tasked with monitoring highway traffic and conducting live broadcasts. While the environmental conditions were favorable for flight, the high density of traffic in the corridor presented a significant challenge to the 'see and avoid' principle. Furthermore, the investigation looked into the post-collision decisions, specifically the Cessna 337 pilot's choice to perform full rudder travel checks before landing, which increased the risk of an in-flight control failure.
Findings
- The primary cause of the collision was the failure of both crews to see and avoid the other aircraft in time to prevent impact.
- The collision occurred in a busy VFR corridor where ATC does not provide traffic advisories or conflict resolution for VFR operations.
- The Cessna 337 pilot's mission-related tasks, including monitoring ground traffic, diverted attention away from maintaining a vigilant lookout.
- Neither aircraft was equipped with a Traffic Alert and Collision Avoidance System (TCAS).
- The pilots were operating on different radio frequencies, precluding any direct warning of the other's presence.
- The Cessna 337 pilot's decision to perform extensive control surface movements before landing increased the risk of a mechanical failure during flight.