Accident Overview
On a charter flight from La Grande Rivière, Quebec, to Puvirnituq, Quebec, Propair Flight 450, a Swearingen SA226-TC (serial number TC-215E), experienced a runway excursion during landing. The aircraft had 13 persons on board. The co-pilot was flying from the right-hand seat. After an instrument approach to runway 19, the aircraft broke through the cloud layer and the co-pilot switched to visual for final approach.
Upon landing, as soon as the nose gear touched down, the aircraft veered left. The co-pilot applied full right rudder and reduced throttles to GROUND IDLE in preparation for reverse thrust. Shortly after, the pilot-in-command took control and left the throttle levers at GROUND IDLE. Noticing the aircraft drifting further left, he applied full right rudder without effect. As a last resort, he pressed the PARK button for the nosewheel steering system, but the aircraft continued left, exited the runway approximately 2,000 feet from the threshold, turned 90 degrees relative to the runway center line, and fell down a 6-foot embankment, where the nose gear and main landing gear separated. One passenger sustained minor injuries, and all occupants evacuated via emergency exits. The main door was jammed.
Aircraft and Runway Information
The aircraft was equipped with a variable authority nosewheel steering system controlled by an electrically controlled hydraulic servo-valve. System controls include an ARM switch, a PARK button, and a button on the left throttle lever that is hard to reach from the co-pilot's seat. The nosewheel steering system is not used during normal takeoff or landing but is intended for low-speed ground maneuvers. The PARK button increases nosewheel deflection to 60 degrees left or right, but the system must be armed and the left power lever button depressed or right speed lever retarded to LOW. The system will not activate if a malfunction is detected or if the nosewheel is more than 3 degrees from the rudder pedal position.
The runway at Puvirnituq is 5,000 feet long by 100 feet wide with a gravel surface that was hard-packed, rough, and wet at the time of the accident. No standing water was present. Runway shoulders were about 30 feet wide, with a drop-off of about 6 feet where the aircraft left the runway.
Crew and Operations
Both pilots were certified and qualified for the flight. The pilot-in-command had 1,050 flying hours on type, and the co-pilot had 350 hours on type. Both were familiar with gravel runway operations. Neither had taken a course on cockpit resource management (CRM). CRM training, which improves crew coordination, was not mandatory for commuter airlines at the time.
On final approach, the pilot-in-command engaged the nosewheel steering ARM switch according to pre-landing checks. The main gear touched down at about 110 knots, and the nosewheel touched down about two seconds later.
Investigation Findings
Examination of the wreckage and aircraft controls revealed no malfunctions that could have contributed to the accident. The hydraulic servo-valve was tested and showed no pre-impact damage. No signs of failure were found on tires or brakes. The runway condition was not a factor; a 15-knot crosswind from 45 degrees was considered negligible for this type of aircraft. The aircraft was within weight and center of gravity limits, and all applicable Airworthiness Directives were completed.
The investigation considered that the left turn on landing may be attributed to a deflection of the nosewheel. Although such a deflection was not confirmed by analysis, other factors were eliminated. The co-pilot did not inform the pilot-in-command of difficulty maintaining directional control. The pilot-in-command, after taking controls at about 80 knots, was surprised by the force required on the right rudder pedal. He did not attempt to engage the nosewheel steering system because the rudder pedals were more than three degrees from the nosewheel position, which would have prevented activation. He did not use reverse thrust in accordance with standard operating procedures for gravel runways. No significant braking was applied. The landing roll marks showed no skidding.
The emergency procedures for an uncommanded nosewheel deflection were described by the company chief pilot as unclear and not well understood by pilots. There were no memorized checklist items for such an event, making it difficult to reference the manual during the emergency.
The manufacturer had issued Service Bulletin SB226-32-058 in May 1995, proposing optional replacement of the hydraulic servo-valve to improve system operation. The operator had the bulletin among records but had not complied. A printing error in the index of service bulletins had been corrected. The history of such servo-valves shows that contamination of hydraulic fluid can degrade operation and cause a situation similar to this accident.
Emergency Evacuation
After the aircraft came to rest, all occupants evacuated without difficulty via emergency exits, as the main door was jammed. One passenger sustained minor injuries.
Weather and Conditions
The accident occurred during daylight. Weather reported by the crew: sky overcast at 1,900 feet, no precipitation, visibility over 15 miles, winds from 140 degrees magnetic at 15 knots.