Accident Overview
On an instrument flight rules (IFR) flight from Hay River to Fort Smith, Northwest Territories, a Northwestern Air British Aerospace Jetstream 31 (flight number PLR734) experienced a hard landing on Runway 29 at Fort Smith. The aircraft sustained damage but remained on the runway; all five occupants evacuated without injury.
Flight History
The flight conducted an IFR approach to Runway 11 but executed a missed approach. The crew then flew a full procedure approach for Runway 29. At approximately 0.2 nautical miles from the threshold, the crew sighted the approach strobe lights and continued for a landing.
Event Sequence
Prior to touchdown, the aircraft entered an aerodynamic stall. It landed hard on the runway at 1515 mountain standard time. The left main landing gear collapsed upon impact. There was no post-impact fire.
Injuries and Damage
The two flight crew members and three passengers were uninjured. They evacuated the aircraft through the left main cabin door. Damage was limited to the collapsed left main landing gear.
Probable Cause
The investigation identified the following causes and contributing factors: 1. Icing conditions were encountered; the airframe de-icing boots were not cycled, and the Vref speed was not increased to offset icing effects. 2. An abrupt change in aircraft configuration (reduction in power to flight idle and addition of 35° flap) caused the speed to decrease rapidly. 3. The aircraft entered an aerodynamic stall due to decreased performance caused by icing, with insufficient altitude to recover before impact.
A finding as to risk noted that the company had not incorporated the British Aerospace Notice to Aircrew into its standard operating procedures at the time, requiring crews to make configuration changes late in the approach, increasing the risk of an unstabilised approach.