Accident Overview
A Perimeter Aviation Ltd. Swearingen Aircraft Corporation SA226-TC, registration C-FTNV, serial number TC-239E, was operating a scheduled passenger flight from Winnipeg, Manitoba, to Norway House, Manitoba. The aircraft carried two crew members and seven passengers. The accident occurred at 0834 central standard time during daylight hours.
Flight Crew
The captain held a valid airline transport pilot licence endorsed for the SA226-TC, with over 6000 total flight hours, approximately 4500 on type, and 45 hours in the last 30 days. He had flown a series of flights in the accident aircraft the previous day, was off duty at 1800, and reported for duty at 0600 on the accident day. He was well rested. The first officer held a valid airline transport pilot licence for aeroplanes, endorsed for the SA226-TC, with over 4000 total hours and approximately 15 hours on type in the last 30 days. He was off duty the previous day, reported at 0545, and was well rested.
Aircraft
Maintenance records indicated the aircraft was maintained and certified according to accepted standards. The aircraft operated within approved gross weight and center-of-gravity limits.
Weather
The 0800 central standard time Norway House automated weather observation station (AWOS) reported visibility nine statute miles; ceiling 600 feet overcast, 1200 overcast, 4700 overcast; temperature −7°C; wind 010° true at six knots. The ceiling was transmitted to the crew approximately 11 minutes before the accident. For landing on Runway 05, the wind was a 45° crosswind from the left at six knots.
Airport
Norway House Airport (CYNE) elevation is 734 feet above sea level. Runway 05/23 is crushed rock, 3922 feet long and 100 feet wide. At the time, the runway was 10% bare and dry and 90% compact snow. Runway edge lights were located 10 feet outside the edge, with snow cleared to within 3 feet inside the lights; cleared snow was thrown past the edge lights, progressively increasing from 0 to approximately 3 inches toward the edge of the extended surface.
Accident Sequence
After touchdown on Runway 05, the crew selected propeller reverse. The aircraft veered left. Despite attempts to regain directional control, the aircraft departed the left side of the runway, entered loose snow, traversed a shallow ditch, climbed a rocky embankment, and came to rest on its belly with all three landing gears collapsed. The crew and passengers exited through the main door stairway and over-wing exits. No injuries were reported.
Ground marks showed the aircraft touched down near the runway center, approximately 300 feet beyond the threshold. Main wheels straddled the centerline for 270 feet; nosewheels touched and all gears tracked straight for another 250 feet. The tracks then arced left to about 35° left of runway heading, straightened briefly, then gradually arced right. The aircraft passed through runway edge lights and left the runway side about 1000 feet from touchdown. The arcing right turn continued as the aircraft descended into a snow-filled ditch. Tire marks were continuous and uniform from touchdown to departure.
Aircraft Systems
Nosewheel steering was not used when the aircraft turned left; marks indicated nosewheels castered normally with no skidding or wide-tracking. Brakes were not applied; main wheels were free-turning post-accident with no overheating. Wing flaps were retracting when the turn began, both at the same position. Impact damage precluded functional testing of nosewheel actuator and sensors, but the engines, propellers, brakes, and flap components were damaged and could not be tested.
Cockpit Voice Recorder
The cockpit voice recorder was analyzed. Spectral analysis of propeller and engine sounds indicated both engines running and propellers producing sounds consistent with an estimated 1935 rpm, though resolution was insufficient for precise measurement.
Beta System Indication
Each engine has a Beta system. After landing, when power levers are at ground idle, Beta pressure builds to activate Beta lights. Beta lights may come on separately, but when both engines achieve Beta pressure, thrust reverse should function uniformly.
Aircraft Damage
The aircraft sustained substantial damage: all three landing gear assemblies failed; both propellers and engines were damaged from ground strikes; both engine mounts suffered bending deformation; and the aircraft was assessed as non-repairable due to impact with the rocky embankment.
Propellers
The left propeller drive decoupled from the engine within the gearbox assembly; the right propeller drive remained coupled despite extensive blade damage. Both propellers were being driven when blades struck the ground. Ground contact turned blades beyond normal reverse travel limits. Teardown found no internal pre-impact failures. Light marks at the same relative position on both Beta tubes indicated propeller blades were at approximately 10° when marks were made.
Power Controls
Power lever and speed lever cables maintained attachment and integrity. Engine mounts were distorted, and nacelles displaced. Post-accident examination showed that when power levers were at flight idle, both propeller pitch controls indicated 42° on the pitch index, and full travel was achieved when moved to full reverse. Left power lever movement achieved full range at the engine. Right engine displacement was more pronounced, so the right power control attained only 95% of full travel in the high power range. After cable disconnection, full travel was available for propeller pitch and fuel controls. All control rods and linkages were correctly attached and maintained integrity.
Fuel Control Mounting and Support
The fuel control assembly comprises a fuel pump, fuel control unit, flow regulator, and concentric input shaft. The mounting pad for the fuel pump on the rear of the engine accessory drive case is the primary attachment and support. The assembly weighs approximately 25 pounds and extends over 12 inches rearward and below the engine case. Eleven inches aft of the fuel pump mount, a two-piece triangular support attaches to a split line on the engine case and to the fuel control assembly. Three bolts on the accessory case attach the upper support (part number 868767-1) to the engine case; two bolts fasten the lower support (part number 867915-1) to complete the triangle and attach to the fuel control assembly. Spacers are brazed onto the three upper bolt holes for alignment.
Weather and Runway Assessment
Weather and runway conditions were appropriate for the landing and were not considered to have contributed to the deviation. Tire marks indicated nosewheel steering and brakes were not applied. The left turn was consistent with asymmetric reverse thrust (more from the left propeller). The tracks straightened briefly, suggesting balanced reverse thrust, then turned right in response to crew control inputs.
Engines and Propellers Assessment
The calculated propeller rpm of 1935 was lower than normal, but this may reflect sonogram limitations. Damage to both propeller blades was consistent with ground strikes under power; bending may have been lessened by contact with loose snow before gear collapse. All controls functioned normally considering deformation. With cables disconnected, all controls worked normally. The left engine fuel control support assembly failed, affecting the sequencing of Beta pressure and Beta lights.