Backgrounder: A17Q0030

Investigation findings for TSB investigation A17Q0030 Mid-air collision near Montréal/St-Hubert Airport, Quebec, March 2017

Investigations conducted by the Transportation Safety Board of Canada (TSB) are complex – an accident is never caused by just one factor. The March 2017 mid-air collision near the Montréal/St-Hubert Airport, Quebec was no exception. There were many factors that caused this accident, the details of which are contained in the 7 findings as to causes and contributing factors. Furthermore, there were 8 findings as to risk as well as 3 other findings.

Findings as to causes and contributing factors

  1. The student pilot of C-FGOI climbed 400 feet above his altitude restriction of 1100 feet and struck C-GPNP from below.
  2. The two aircraft collided at an altitude of approximately 1500 feet; as a result of the collision, both aircraft sustained significant damage and were rendered uncontrollable.
  3. A broken wire caused the push-to-talk keying signal on C-GPNP’s radiocommunication system to transmit intermittently prior to entering the control zone and immediately preceding the collision.
  4. Troubleshooting the aircraft’s radiocommunication problem distracted the pilot of C‑GPNP; the pilot thus inadvertently allowed the aircraft to descend 100 feet below his altitude restriction of 1600 feet.
  5. With his attention focused inside the cockpit, the pilot of C-GPNP did not see C-FGOI in time to avoid a collision.
  6. It could not be determined why the student pilot of C-FGOI climbed after levelling off at his assigned altitude.
  7. Neither pilot saw the other aircraft in time to avoid a mid-air collision, partly owing to the inherent limitations of the see-and-avoid principle.

Findings as to risk

  1. If pilots have only the minimum required proficiency in the language used with air traffic control, there is a greater risk of miscommunication between the pilots and controllers, and of misunderstanding critical information.
  2. If airspace design relies on limited vertical separation between converging tracks in congested airspace that is mainly used by pilots whose flight skill levels and language proficiency vary, there is an increased risk of traffic conflicts.
  3. If air traffic control tower unit operations manuals do not provide explicit directives on staffing and workload, controller workload in high-traffic situations may exceed controller staffing levels, increasing the risk of ineffective air traffic control.
  4. If air traffic controllers do not allow sufficient time to obtain a complete readback of instructions, there is a risk that errors in pilot readbacks may go unnoticed and uncorrected.
  5. If all involved pilots are not provided with information regarding conflicting traffic, there is an increased risk that use of the see-and-avoid principle will not be optimized.
  6. If student pilots are authorized to conduct solo flights before they have successfully demonstrated an operational level of language proficiency in accordance with the proficiency scale set out in the Canadian Aviation Regulations, there is an increased risk of miscommunication.
  7. If Transport Canada only conducts limited oversight of language proficiency testing, there is a risk that designated examiners will not apply the Canadian Aviation Regulations language proficiency scale as intended to ensure that applicants demonstrate the required ability to speak and understand at an operational or expert level.
  8. If pilots operating under visual flight rules rely solely on information from air traffic controllers to avoid other aircraft, there is an increased risk of collision in controlled airspace.

Other findings

  1. Without a clear separation between a language-testing service provider and a flight-training provider, there is potential for a real or perceived conflict of interest.
  2. Because of its limitations, the see-and-avoid principle cannot be used as the sole means of preventing aircraft collisions when operating under visual flight rules.
  3. As established by the TSB in previous reports, a number of viable and economical on‑board alerting systems exist or are under development. These technologies offer the potential to significantly reduce the risk of mid-air collisions.