What happened
On July 7, 2013, a de Havilland DHC-3 Otter, registration N93PC, crashed into terrain approximately 2,320 feet from the threshold of runway 25 at Soldotna Airport, Alaska. The aircraft was operating as an on-demand charter flight for Rediske Air, destined for Bear Mountain Lodge.
Prior to the accident, the pilot had flown a positioning leg from Nikiski to Soldotna. During the stay in Nikiski, the pilot loaded the aircraft with approximately 300 pounds of estimated cargo, consisting of groceries and lodge supplies. After picking up nine passengers and their baggage in Soldotna, the aircraft departed runway 25. Shortly after takeoff, the airplane experienced a rapid right roll and began losing altitude, impacting the ground with a nose-low and right-wing-low attitude. The impact was followed by an extensive postcrash fire that destroyed the cockpit and cabin area. All 10 occupants (the pilot and nine passengers) were killed.
The investigation
Investigators analyzed a video recovered from a passenger's smartphone, which captured the takeoff sequence. The video showed the aircraft's airspeed decreasing from 68 mph to 44 mph and the angle of attack increasing from 5 degrees to 13.7 degrees over 8.5 seconds, eventually reaching levels consistent with an aerodynamic stall. The video also revealed that the flaps were set to the full-down (landing) position, which contradicted the recommended takeoff procedures in the airplane flight manual.
Engine and propeller examinations showed the engine was operating during impact, with no evidence of internal failure. The investigation also focused on the aircraft's weight and balance. While the load manifest listed a cargo weight of 300 pounds, investigators determined the actual weight of the recovered food and supplies was significantly higher, approximately 613 pounds, plus the weight of liquid items.
Calculations performed by the NTSB indicated that the combination of the actual cargo weight, passenger weights, and baggage caused the aircraft to exceed its maximum gross weight of 8,000 pounds. Furthermore, the center of gravity (CG) was estimated to be at least 5.5 inches aft of the 152.2-inch limit, with some studies suggesting the CG was as far aft as 161 inches.
Findings
- The aircraft was operated with a center of gravity significantly aft of the allowable limit.
- The pilot failed to determine the actual weight of the cargo being loaded.
- The use of the full-down flap setting during takeoff exacerbated the nose-up pitching moment.
- The aircraft's weight exceeded its maximum allowable gross weight.
- The extreme aft center of gravity caused an uncontrollable nose-up pitch, leading to an aerodynamic stall.