Narrative:Air Canada Flight 646, a Canadair Regional Jet, departed Toronto-Lester B. Pearson International Airport, at 2124 h on a flight to Fredericton. The first officer, in the right-hand seat, was the pilot-flying (PF). The forecast and reported weather for the Fredericton Airport for the time of arrival was vertical visibility of 100 feet and horizontal visibility of one-eighth of a mile in fog. The runway visual range (RVR) was 1200 feet for the landing on runway 15 with the runway lights set to strength 5.
The flight was uneventful until the aircraft was on final approach to the Fredericton airport. The autopilot was controlling the aircraft based on commands from the crew, the flight
management system, and signals from the ground-based instrument landing system (ILS) for runway 15 at Fredericton. The aircraft's landing lights were on for the approach and landing.
The captain saw the glow from the runway approach lights through the fog at about 300 feet above ground level (agl), 100 feet above decision height for the approach. At decision
height, 200 feet above the runway, the captain, the pilot-not-flying (PNF), called the lights in sight and the first officer responded that he was landing. The first officer disconnected the
autopilot, at about 165 feet above ground, to hand fly the rest of the approach and landing.
After the autopilot was disconnected, the aircraft drifted above the glide path, and twice the captain coached the first officer to get the aircraft down to the glide path. The first officer
reduced thrust in response to the captain's first mention to get the aircraft down, and he reduced thrust to idle at about 80 feet agl. Moments later, the captain, aware that the aircraft was left of the center line but not knowing the distance traveled down the runway, and not sure that a safe landing could be made, ordered a go-around, which the first officer acknowledged.
The thrust levers were advanced, the first officer selected the go-around mode for the flight director, and he started to increase the pitch of the aircraft to the command bar indications, 10 degrees nose up. About one second after the first officer acknowledged the go-around, the stick shaker (stall warning) activated. As the aircraft reached 10 degrees nose up, about one and one-half seconds after the stick shaker activated, the captain called flaps and selected them to the go-around setting, the warbler tone associated with the stall protection system (SPS) sounded, and the aircraft stalled aerodynamically. The aircraft rolled right to approximately 55 degrees of bank, and the right wing tip contacted the runway about 2700 feet from the threshold and 45 feet left of the center line, the right wing tip bending upwards about four feet from the tip. The aircraft rolled left toward wings level, then, about 260 feet further down the runway, struck it again, this time banked about 20 degrees to the right with the nose down about 12 degrees. The nose wheel assembly broke off, the right winglet broke off, the radome and underside of the nose cockpit area were heavily damaged, and electrical power, except for emergency lighting, was lost. The aircraft rolled left onto its main wheels and, with the engines now at full power, departed the right side of the runway just past the intersection with runway 09/27. The aircraft plowed through the snow, on its main wheels, until it struck a ditch parallel to and about 200 feet from the runway. The aircraft became airborne after striking the ditch, very low to the ground, and flew in an arc to next strike a sand hill about 1000 feet right of the runway. At the top of the hill, the aircraft slewed to the right, struck some trees, one approximately 22 inches in diameter, and came to rest. The aircraft stopped on a heading of 314 magnetic, about 1130 feet west of the runway and 2100 feet from the first impact point on the runway. There was no post-crash fire.
FINDINGS AS TO CAUSES AND CONTRIBUTING FACTORS:
- Although for the time of the approach the weather reported for Fredericton--ceiling 100 feet and visibility mile--was below the 200-foot decision height and the charted ½ -mile (RVR 2600) visibility for the landing, the approach was permitted because the reported RVR of 1200 feet was at the minimum RVR specified in CAR 602.129.
- Based on the weather and visibility, runway length, approach and runway lighting, runway condition, and the first officer's flying experience, allowing the first officer to fly the approach is questionable.
- The first officer allowed the aircraft to deviate from the flight path to the extent that a go-around was required, which is an indication of his ability to transition to landing in the existing environmental conditions.
- Disengagement of the autopilot at 165 feet rather than at the 80-foot minimum autopilot altitude resulted in an increased workload for the PF, allowed deviations from the glide path, and deprived the pilots of better visual cues for landing.
- In the occurrence environmental conditions, the lack of runway centre line and touchdown-zone lighting probably contributed to the first officer not being able to see the runway environment clearly enough to enable him to maintain the aircraft on the visual glide path and runway centre line.
- The first officer's inexperience and lack of training in flying the CL-65 in low-visibility conditions contributed to his inability to successfully complete the landing.
- The situation of a captain being the PNF when ordering a go-around probably played a part in the uncertainty regarding the thrust lever advance and the raising of the flaps because there was no documented procedure covering their duties.
- The go-around was attempted from a low-energy situation outside of the flight boundaries certified for the published go-around procedures; the aircraft's low energy was primarily the result of the power being at idle.
- The sequential nature of steps within the go-around procedures, in particular, in directing the pitch adjustment prior to noting the airspeed, the compelling nature of the command bars, and the high level of concentration required when initiating the go-around contributed to the first officer's inadequate monitoring of the airspeed during the go-around attempt.
- Following the command bars in go-around mode does not ensure that a safe flying speed is maintained, because the positioning of the command bars does not take into consideration the airspeed, flap configuration, and the rate of change of the angle of attack, considerations required to compute stall margin.
- The conditions under which the go-arounds are demonstrated for aircraft certification do not form part of the documentation that leads to aircraft limitations or boundaries for the go-around procedure; this contributed to these factors not being taken into account when the go-around procedures were incorporated in aircraft and training manuals.
- The published go-around procedure does not adequately reflect that once power is reduced to idle for landing, a go-around will probably not be completed without the aircraft contacting the runway (primarily because of the time required for the engines to spool up to go-around thrust).
- The Air Canada stall recovery training, as approved by Transport Canada, did not prepare the crew for the conditions in which the occurrence aircraft stick shaker activated and the aircraft stalled.
- The limitations of the ice-detection and annunciation systems and the procedures on the use of wing anti-ice did not ensure that the wing would remain ice-free during flight.
- Ice accretion studies indicate that the aircraft was in an icing environment for at least 60 seconds prior to the stall, and that during this period a thin layer of mixed ice with some degree of roughness probably accumulated on the leading edges of the wings. Any ice on the wings would have reduced the safety margins of the stall protection system.
- The implications of ice build-up below the threshold of detection, and the inhibiting of the ice advisory below 400 feet, were not adequately considered when the stall margin was being determined during the 1996 certification of the ice-detection system and associated procedures.
- The stall protection system operated as designed: that it did not prevent the stall is related to the degraded performance of the wings.
- The Category I approach was without the extra aids and defences required for Category II approaches.
- Canadian regulations with respect to Category I approaches are more liberal than those of most countries and are not consistent with the ICAO International Standards and Recommended Practices (Annex 14), which defines visibility limits; in Canada, the visibility values, other than RVR, are advisory only.
- Even though a Category I approach may be conducted in weather conditions reported to be lower than the landing minima specified for the approach, there is no special training required for any flight crew member, and there is no requirement that flight crew be tested on their ability to fly in such conditions.
- Air Canada's procedures required that the captain fly the aircraft when conducting a Category II approach, in all weather conditions; however, the decision as to who will fly low-visibility Category I approaches was left to the captain, who may not be in a position to adequately assess the first officer's ability to conduct the approach.
- The aircraft stalled at an angle of attack approximately 4.5 degrees lower, and at a CLmax
0.26 lower, than would be expected for the natural stall.
- On final approach below 1000 feet agl, the wing performance on the accident flight was degraded over the wing performance at the same phase on the previous flight.
- The engineering simulator comparison indicated two step reductions in aircraft performance, at 400 feet and 150 feet agl, as a result of local flow separation in the vicinity of wing station (WS) 247 and WS 253.
- Pitting on the leading edges of the wings had a negligible effect on the performance of the aircraft.
- The sealant on the leading edges of both wings was missing in some places and protruding from the surface 2 to 3 mm in others. Test flights indicate that the effect of the protruding chordwise sealant on the aircraft performance could have accounted for a reduction of 1.7 to 2.0 degrees in maximum fuselage angle of attack and of 0.03 to 0.05 in CLmax
- The maximum reduction in angle of attack resulting from ground effect is considered to be in the order of 0.75±0.5 degree: the aircraft angle of attack was influenced by ground effect during the go-around manoeuvre.
- The performance loss caused by the protruding sealant and by ground effect was not great enough to account for the performance loss experienced; there is no apparent phenomenon other than ice accretion that could account for the remainder of the performance loss.
- Neither Bombardier Inc., nor Transport Canada, nor Air Canada ensured that the regulations, manuals, and training programs prepared flight crews to successfully and consistently transition to visual flight for a landing or to go-around in the conditions that existed during this flight, especially considering the energy state of the aircraft when the go-around was commenced.
- Both the captain and the first officer were licensed and qualified for the duties performed during the flight in accordance with regulations and Air Canada training and standards, except for minor training deficiencies with regard to emergency equipment.
- The occurrence flight attendant was trained and qualified for the flight in accordance with existing requirements.
- The aircraft was within its weight and centre-of-gravity limits for the entire flight.
- Records indicate that the aircraft was certified, equipped, and maintained in accordance with existing regulations and approved procedures.
- There was no indication found of a failure or malfunction of any aircraft component prior to or during the flight.
- When the stick shaker activated, it is unlikely that the crew could have landed the aircraft safely or completed a go-around without ground contact.
- When power was selected for the go-around, the engines accelerated at a rate that would have been expected had the thrust levers been slammed to the go-around power setting.
- The aircraft was not equipped with an emergency locator transmitter, nor was one required by regulation.
- The lack of an emergency locator transmitter probably delayed locating the aircraft and its occupants.
- Passengers and crew had no effective means of signalling emergency rescue services personnel.
- The flight crew did not receive practical training on the operation of any emergency exits during their initial training program, even though this was required by regulation.
- Air Canada's initial training program for flight crew did not include practical training in the operation of over-wing exits or the flight deck escape hatch.
- Air Canada's annual emergency procedures training for flight crew regarding the operation and use of emergency exits did not include practical training every third year, as required. Annual emergency exit training was done by demonstration only.
- The flight crew were unaware that a pry bar was standard emergency equipment on the aircraft.
- The four emergency flashlights carried on board were located in the same general area of the aircraft, increasing the possibility that all could be rendered inaccessible or unserviceable in an accident. (See section 4.1.6)
- That there was a Flight Service Station specialist, as opposed to a tower controller, at the Fredericton airport at the time of the arrival of ACA 646 was not material to this occurrence.
» Airplane’s Low-energy Condition and Degraded Wing Performance Cited in Unsuccessful Go-around Attempt
Official accident investigation report
Follow-up / safety actions
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Toronto-Pearson International Airport, ON to Fredericton Airport, NB as the crow flies is 1053 km (658 miles).