What happened
On a scheduled flight from Toronto–Lester B. Pearson International Airport to Cozumel, Mexico, a Boeing 737-800 (registration C-FTAH) experienced significant instrument discrepancies during its takeoff roll. As the aircraft accelerated, the autothrottle disengaged, and the first officer noticed an airspeed disagree alert. Due to the high-speed nature of the takeoff, the pilot flying transferred control to the captain near the decision speed (V1).
During the initial climb, the crew encountered several conflicting indications. The aircraft's stick shaker activated, and the flight director issued a command to pitch the aircraft nose-down by 5°. Because the flight was conducted in visual conditions, the captain was able to recognize these commands as erroneous and maintained a positive climbing attitude by referencing the outside horizon. The crew eventually identified that the right-side airspeed indication was unreliable and performed the necessary checklists to manage the situation. The aircraft returned to Toronto and landed safely, though the crew requested firefighting services on standby due to the weight of the aircraft.
The investigation
The TSB examined the aircraft's pitot-static system and the performance of the air data and inertial reference units. The investigation looked into the crew's decision-making process, the effectiveness of the airline's Safety Management System (SMS), and the impact of a previous incident involving a pitot tube strike by an owl two days prior. Investigators also reviewed Boeing's existing advisories regarding erroneous airspeed indications and the airline's internal reporting procedures.
Findings
- A failure within the right pitot-static system produced incorrect airspeed data from the right air data and inertial reference unit.
- This failure caused erroneous airspeed indications, stall warnings, and misleading flight director commands during the critical takeoff and climb phases.
- The airline's safety management system did not trigger a risk assessment because the event was not initially recognized as a reportable occurrence.
- Inadequate documentation of aircraft malfunctions in the journey log increased the risk of unresolved technical issues.