Accident Details
On a charter flight from Yellowknife, Northwest Territories, to Blachford Lake, an Air Tindi Ltd. de Havilland DHC-3T (Turbo) Otter (registration C-FXUY, serial number 142) experienced a stall shortly after takeoff. The aircraft, equipped with a Pratt and Whitney PT6-34A engine and SI-3-8100 floats, was loaded with two crew, seven passengers, and 840 pounds of cargo. The pilot conducted a pre-flight passenger briefing covering life preservers and emergency exits.
Sequence of Events
During the takeoff run at about 1912 mountain daylight time, the aircraft performed normally. It became airborne at approximately 55 mph, below the normal 60 mph. The pilot applied forward control column to counter a pitch-up tendency but received no response. After trimming the nose forward, the aircraft continued pitching up until it stalled at about 50 feet above the water. The left wing dropped, and the aircraft struck the water in East Bay in a nose-down, 45° left bank attitude. On impact, the left wing and left float detached, and the aircraft came to rest on its left side. The crew evacuated passengers before the aircraft submerged, with assistance from local boaters. No serious injuries occurred, but the aircraft sustained substantial damage.
Weight and Balance Issues
Earlier that day, the aircraft sustained damage to the left water rudder bracket while mooring at Daring Lake. To repair it, the aircraft was towed from the water, requiring additional ballast: 40 imperial gallons of fuel were added to the rear tank, and the pilot and an aircraft maintenance engineer sat on the rear floats. The repair was completed at about 1800. The pilot then took a short flight to burn off the rear fuel but returned promptly when passengers for the 1800 flight were waiting.
Aware of the tail-heavy configuration, the pilot requested 20–30 imperial gallons of fuel be added to the forward tank, but an inexperienced dock hand added only 10. Cargo was split: 300 pounds in row five and 540 pounds in the aft cargo bay. Passengers were seated in the first four rows. The pilot did not have further fuel added despite knowing the weight imbalance, as passengers were already loaded and the flight was one hour behind schedule. He was aware the aircraft was likely aft of the center of gravity (C of G) limit but did not complete a C of G calculation.
Air Tindi used standard passenger weights (200 lb adult male, 165 lb adult female). Actual average male weight was 230 lb; the sole female was 150 lb. Actual total passenger weight was 1532 lb, versus 1365 lb calculated. The aircraft's total take-off weight was 8873 lb, below the 9000 lb maximum. However, the C of G was 158.8 inches aft of datum, 10.5 inches beyond the aft limit of 148.3 inches.
Investigation Findings
The Transportation Safety Board determined that the aircraft was loaded such that its C of G exceeded the rearward limit, exceeding aerodynamic pitch control capability. Additionally, the pilot did not complete a weight and balance report, so the severity of the aft C of G was unrecognized. The use of standard passenger weights underestimated actual weight, increasing the risk of inadvertent overweight loading. The pilot had only three hours of sleep the previous night and had been on duty for 12 hours, which may have contributed to rushing preparations.
Emergency Evacuation
All occupants escaped without serious injury. The pilot and ground crew attendant exited through the right cockpit door, assisted two passengers, then evacuated others via the right rear cargo doors after the cockpit door became unusable. Two passengers used the roof emergency exit. The low-energy impact, upright position of the aircraft, clear orientation, accessible exits, and effective crew command facilitated the successful evacuation.
Safety Actions Taken by Air Tindi
Following the occurrence, Air Tindi implemented changes: discontinuing use of fuel as ballast for towing; increasing operational oversight and pilot briefings to ensure weight and balance calculations; adopting a new weight and balance procedure; and adjusting standard passenger weights to better reflect actual loads (summer: male 200 lb, female 165 lb; winter: male 206 lb, female 171 lb, with carry-on baggage weighed separately).
Probable Cause
The aircraft was operated with a center of gravity beyond the rearward limit due to inadequate weight and balance calculation, leading to loss of pitch control and subsequent stall.