What happened
An Air Tindi Ltd. de Havilland DHC-3T (Turbo) Otter, registration C-FXUY, was preparing for a charter flight from the Air Tindi dock in Yellowknife, Northwest Territories, to Blachard Lake. The aircraft was carrying two crew members, seven passengers, and 840 pounds of cargo.
During the takeoff roll, the aircraft reached an airborne speed of approximately 55 mph, which was below the standard 60 mph requirement. As the aircraft climbed, the pilot attempted to use the forward control column to counteract a significant pitch-up tendency, but the controls failed to respond. Despite efforts to trim the nose forward, the aircraft continued to pitch up until it stalled at an altitude of roughly 50 feet. The aircraft subsequently struck the water in East Bay with a 45-degree left bank and a nose-down attitude. The impact caused the left wing and left float to detach, and the aircraft settled on its left side. While the aircraft sustained substantial damage, the crew and passengers successfully evacuated before the plane submerged, and no serious injuries were reported.
The investigation
The investigation established that the aircraft's center of gravity (C of G) was significantly behind the allowable rearward limit. The aircraft had been used as a weight for towing purposes earlier that day, requiring 40 imperial gallons of fuel to be placed in the rear tank to prevent the aircraft from being front-heavy on the float cart.
During the final loading for the charter flight, an error occurred during refueling. While the pilot intended to add enough fuel to the forward tank to balance the weight, a dock hand added only 10 imperial gallons to the forward cell. Although the pilot was aware that the aircraft was likely in an aft C of G configuration, he did not perform a formal weight and balance calculation, partly due to the flight being delayed by one hour and the pilot's desire to maintain the schedule. Additionally, the pilot had only three hours of sleep the previous night and was nearing the end of a long duty day.
Findings
- The aircraft was loaded with a center of gravity located beyond the rearward limit, which caused the aircraft to exceed its aerodynamic pitch control capabilities.
- The pilot failed to complete a weight and balance report before departure, which prevented him from recognizing the extreme severity of the aft C of G position.
- The use of standard passenger weights led to an underestimation of the total passenger weight, increasing the risk of exceeding maximum takeoff weight limits.
Safety action
Following the investigation, Air Tindi implemented several changes, including:
- Prohibiting the use of fuel as ballast for aircraft towing.
- Increasing operational oversight and requiring pilot briefings to ensure weight and balance calculations are performed before every departure.
- Implementing a new procedure for weight and balance calculations.
- Adjusting the company's standard passenger weight models to better reflect actual weights and accounting for carry-on baggage as cargo.