Accident de Havilland Canada DHC-8-102 C-GTAI,

ASN Wikibase Occurrence # 320348

Date:	Tuesday 24 February 2015
Time:	18:25
Type:	de Havilland Canada DHC-8-102
Owner/operator:	Air Canada Express
Registration:	C-GTAI
MSN:	078
Year of manufacture:	1987
Engine model:	Pratt & Whitney Canada PW120A
Fatalities:	Fatalities: 0 / Occupants: 18
Aircraft damage:	Substantial, repaired
Category:	Accident
Location:	Sault Ste. Marie Airport, ON (YAM) - Canada
Phase:	Landing
Nature:	Passenger - Scheduled
Departure airport:	Toronto-Pearson International Airport, ON (YYZ/CYYZ)
Destination airport:	Sault Ste. Marie Airport, ON (YAM/CYAM)
Investigating agency:	TSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Air Canada Express flight 7795 was a scheduled domestic flight from Toronto/Lester B. Pearson International Airport, Canada, to Sault Ste. Marie Airport.
On board the DHC-8-102 aircraft were 15 passengers, 2 flight crew members, and 1 cabin crew member. The captain performed the role of pilot flying (PF) and the first officer performed the role of pilot monitoring (PM).
Just prior to descent from cruise altitude, the PF briefed the PM for the expected approach into Sault Ste. Marie. The PF was aware of the marginal weather conditions and included the possibility of a go-around and diversion in the briefing.
As part of the briefing, the flight crew set the approach speed bugs to the appropriate speed for aircraft weight and flight conditions. The crew determined that the applicable landing reference speed (Vref) was 96 knots, which required an approach speed bug setting of 101 knots.
When the aircraft was approximately 42 nautical miles (nm) from CYAM, the controller at the Toronto Area Control Centre cleared the flight to descend to 5000 feet above sea level (ASL) and, given the expected weather conditions, requested that the crew report when they had the airport in sight for the visual approach.
As AC7795 reached 15 nm from Sault Ste. Marie in level flight at 5000 feet ASL, the crew reported that the in-flight visibility was reduced due to ice crystals. In consideration of this, they requested to be cleared for the VOR/DME approach to runway 30, rather than the visual approach, and were cleared as requested.
While descending out of 3000 feet ASL, the flight crew passed through the area of ice crystals and acquired the airport visually. Although the flight was now in visual conditions, the crew noticed a significant snow shower approaching the arrival runway from the west. They reported these conditions to the controller, who cleared the flight for the visual approach, instructing them to deviate as necessary from the VOR approach.
At 18:21:34 the aircraft passed over the final approach fix, 8.7 nm from the runway threshold, at a height of 2840 feet above ground level (AGL) and an indicated airspeed of 204 knots. The aircraft was descending on a 3° vertical path, although this was done visually, rather than with avionics-based vertical navigation guidance.
The aircraft slowly decelerated from 204 to 181 knots while maintaining the 3° vertical path in descent from 2840 feet to 1500 feet.
At 18:22:50, when AC7795 was 5 nm from Sault Ste. Marie, the flight crew contacted the Sault Ste. Marie control tower for landing clearance. The controller informed the crew that the wind was from 310° magnetic (M) at 22 knots with gusts to 29 knots, and mentioned the line of weather currently rolling across the runway. The controller further informed the crew that, due to this weather, the runway visual range (RVR) visibility had decreased to 1100 feet, with the runway lights set to level 4 intensity. The PM responded that they could see the approaching weather.
At 18:23:05 and at 1500 feet, the power levers were moved toward flight idle and the engine torque reduced to between 3% and 4%. The aircraft began to decelerate more rapidly.
The tower controller then informed AC7795 that the RVR had now reduced to 1000 feet, with the runway lights now at level 5 (full) intensity. Wind was reported as from 310°M at 25 knots, and JZA7795 was cleared to land.
At 18:23:49, at 1000 feet and 2.8 nm from the runway threshold, the flaps were extended to 15° and the PF increased torque to 25%. The aircraft's airspeed was 148 knots.
Between 1000 feet and 500 feet on approach, the aircraft generally maintained the 3° vertical path as the speed decreased from 148 to 122 knots. The engine torque varied during that time between 5% and 30% to account for configuration changes and wind gusts.
At 500 feet, the airspeed was 122 knots, or 21 knots higher than the bugged approach speed of 101 knots. The aircraft was on the appropriate vertical path and torque was steady at 25%. The PF made the 8° left turn to align the aircraft with the runway heading.
At 18:24:56, air traffic control (ATC) provided one last update to JZA7795, stating that the RVR was now 1200 feet.
At 200 feet and at an airspeed of 124 knots, the PF began to reduce torque to idle and, as a result, the airspeed began to decrease rapidly. Although the aircraft's nose-up pitch was gradually increased and vertical speed was relatively stable, the vertical path steepened due to the decreasing airspeed and resultant ground speed reduction. The aircraft drifted below the 3° vertical path. This would normally be visually indicated by 4 red lights on the precision approach path indicator (PAPI), meaning the aircraft is too low.
At some point below 200 feet, the flight crew lost visual reference to the ground due to the approaching weather system of blowing snow. The approach was continued.
At 18:25:15, the terrain awareness and warning system (TAWS) issued a verbal alert to the pilots indicating that the aircraft's height was 50 feet.
Then, at 20 feet, torque was increased toward 30%. At 18:25:19, the aircraft contacted the ground approximately 450 feet (137 meters) prior to the runway threshold at an airspeed of 94 knots.
The ground preceding the runway was covered in approximately 8 to 12 inches of snow.
The aircraft was in a level pitch attitude when it contacted the surface and touched down with a peak vertical acceleration of 2.32g.
Following touchdown, the nose landing gear assembly and wheel struck and damaged an approach light located 300 feet prior to the runway threshold. The flight crew heard a thump, but had not seen the light and were unsure what had caused the noise.
The aircraft came to a stop on the runway centreline, approximately 1500 feet past the threshold. The flight crew assessed the ground visibility as very poor, due to the blowing snow.
Unsure of the aircraft's status, the flight crew informed the tower controller that the aircraft may have landed short of the runway and may have clipped the nosewheel. The crew asked the control tower to send a vehicle to their position to assess the situation, and requested that a bus be sent to move the passengers.
When the emergency vehicles arrived and assessed the condition of the aircraft, no significant damage was noticed. Upon receiving this information, the flight crew elected to taxi the aircraft to the gate.
The aircraft taxied to the gate without further incident, and the crew shut down the engines and deplaned the passengers.
The crew did not believe there was damage to the aircraft and, therefore, did not pull the circuit breaker to prevent the cockpit voice recorder data from being overwritten. As a result, relevant data that would have been captured on the 30-minute cockpit voice recorder was overwritten while the aircraft remained electrically powered at the gate.
After exiting the aircraft at the gate, the crew was notified of damage to an approach light and contacted maintenance to have the aircraft inspected.
The aircraft sustained significant damage, mostly localized to the area near the nose landing gear, which had struck the approach light.
The nose gear and nose gear doors were damaged and required replacement. Additionally, both main landing gear were determined to have exceeded load limits and required replacement.

Findings as to causes and contributing factors:
1. The company standard operating procedures require an approach speed of Vref + 5 knots; however, this is being interpreted by flight crews as a target to which they should decelerate, from 120 knots, once the aircraft is below 500 feet. As a result, the majority of examined approaches, including the occurrence approach, were unstable, due to this deceleration.
2. Due to ambiguity in the guidance and uncertainty as to the required speeds during the approach, the crew did not recognize that the approach was unstable, and continued.
3. On the approach, the pilot flying reduced power to idle to reduce the approach speed from 122 knots toward 101 knots at 200 feet above ground level. This steepened the aircraft's vertical path.
4. The rapidly decreasing visibility resulted in the airport environment and the precision approach path indicator lights becoming obscured; as a result, the steepened vertical profile went unnoticed and uncorrected.
5. Although the loss of visual reference required a go-around, the crew continued the approach to land as a result of plan continuation bias.
6. The terrain awareness and warning system did not alert the crew to the aircraft's proximity to the ground once the aircraft was below 50 feet, possibly due to the rapid rate of closure. This lack of warning contributed to the crew not being aware of the aircraft's height above ground.
7. Due to the uncorrected steepened vertical profile, loss of visual reference, and lack of normal terrain warning, the aircraft contacted the surface approximately 450 feet prior to the runway threshold.

Findings as to risk:
1. If guidance provided to flight crews allows for large tolerance windows, and crews are not trained to recognize an unstable condition, then there is a continued risk that flights that are unstable will be continued to a landing.
2. If approaches that require excessive deceleration below established stabilization heights are routinely flown, then there is a continued risk of an approach or landing accident.
3. If crews do not report unstable approaches and operators do not conduct flight data monitoring but rely only on safety management system reports to determine the frequency of unstable approaches, there is a risk that these issues will persist and contribute to an accident.

Accident investigation: