Accident ATR 42-320 C-GWEA,

ASN Wikibase Occurrence # 319755

Date:	Wednesday 13 December 2017
Time:	18:12
Type:	ATR 42-320
Owner/operator:	West Wind Aviation
Registration:	C-GWEA
MSN:	240
Year of manufacture:	1991
Total airframe hrs:	26481 hours
Cycles:	32051 flights
Engine model:	Pratt & Whitney Canada PW121
Fatalities:	Fatalities: 1 / Occupants: 25
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	1,5 km W of Fond-du-Lac Airport, SK (ZFD) - Canada
Phase:	Initial climb
Nature:	Passenger - Scheduled
Departure airport:	Fond-du-Lac Airport, SK (ZFD/CZFD)
Destination airport:	Stony Rapids Airport, SK (YSF/CYSF)
Investigating agency:	TSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
A West Wind Aviation ATR 42-300 collided with trees and terrain shortly after takeoff from Fond-du-Lac Airport (CZFD), Canada. The aircraft was destroyed. Six passengers and one crew member sustained serious injuries. Eighteen other aircraft occupants were also injured. One of the passengers, a 19-year old male, died of his injuries on December 25.
The aircraft arrived at Fond-du-Lac Airport at 17:25 local time. During the descent, the aircraft encountered icing conditions and the anti-icing and de-icing systems were activated. When the de-icing and anti-icing systems were turned off, residual ice remained on portions of the aircraft.
At Fond-du-Lac Airport new passengers boarded and cargo was loaded on the aircraft.
The operator, West Wind Aviation, had some de-icing equipment in the terminal building at the airport, consisting of two ladders, a hand-held spray bottle with electric blanket and wand, and a container of de-icing fluid. However, the aircraft was not de-iced before takeoff, and the takeoff was commenced with ice contamination on the aircraft.
The aircraft took off from runway 28 at 18:11, bound for Stony Rapids.
At 18:12, shortly after takeoff, the aircraft collided with trees and terrain less than a mile west of the end of runway 28. The wreckage path through trees and across terrain was at least 800 feet long. The aircraft came to rest with the forward cabin and cockpit rotated 90° to the right, and the remainder of the fuselage rotated about 35° to the right.

Findings as to causes and contributing factors
1. When West Wind commenced operations into Fond-du-Lac Airport (CZFD) in 2014, no effective risk controls were in place to mitigate the potential hazard of ground icing at CZFD.
2. Although both the flight crew and the dispatcher were aware of the forecast ground icing, the decision was made to continue with the days planned route to several remote airports that had insufficient de-icing facilities.
3. Although the aircrafts ice-protection systems were activated on the approach to CZFD, the aircrafts de-icing boots were not designed to shed all of the ice that can accumulate, and the anti-icing systems did not prevent ice accumulation on unprotected surfaces. As a result, some residual ice began to accumulate on the aircraft.
4. Although the flight crew were aware of the ice, there were no handling anomalies noted on the approach. Consequently, the crew likely did not assess that the residual ice was severe enough to have a significant effect on aircraft performance. Subsequently, without any further discussion about the icing, the crew continued the approach and landed at CZFD.
5. Weather conditions on the ground were conducive to ice or frost formation, and this, combined with the nucleation sites provided by the residual mixed ice on the aircraft, resulted in the formation of additional ice or frost on the aircrafts critical surfaces.
6. Because the available inspection equipment was inadequate, the first officers ice inspection consisted only of walking around the aircraft on a dimly lit apron, without a flashlight, and looking at the left wing from the top of the stairs at the left rear entry door (L2). As a result, the full extent of the residual ice and ongoing accretion was unknown to the flight crew.
7. Departing from remote airports, such as CZFD, with some amount of surface contamination on the aircrafts critical surfaces, had become common practice, in part due to the inadequacy of de-icing equipment or services at these locations. The past success of these adaptations resulted in the unsafe practice becoming normalized and this normalization influenced the flight crews decision to depart.
8. Although the flight crew were aware of icing on the aircrafts critical surfaces, they decided that the occurrence departure could be accomplished safely. Their decision to continue with the original plan to depart was influenced by continuation bias, as they perceived the initial and sustained cues that supported their plan as more compelling than the later cues that suggested another course of action.
9. As a result of the ice that remained on the aircraft following the approach and the additional ice that had accreted during the ground stop, the aircrafts drag was increased by 58% and its lift was decreased by 25% during the takeoff.
10. During the takeoff, despite the degraded performance, the aircraft initially climbed; however, immediately after lift off, the aircraft began to roll to the left without any pilot input. This roll was as a result of asymmetric lift distribution due to uneven ice contamination on the aircraft.
11. Following the uncommanded roll, the captain reacted as if the aircraft was an uncontaminated ATR 42, with the expectation of normal handling qualities and dynamic response characteristics; however, due to the contamination, the aircraft had diminished roll damping resulting in unexpected handling qualities and dynamic response.
12. Although the investigation determined the ailerons had sufficient roll control authority to counteract the asymmetric lift, due to the unexpected handling qualities and dynamic response, the roll disturbance developed into an oscillation with growing magnitude and control in the roll axis was lost.
13. This loss of control in the roll axis, which corresponds with the known risks associated with taking off with ice contamination, ultimately led to the aircraft colliding with terrain.
14. The aircraft collided with the ground in relatively level pitch, with a bank angle of 30° left. As a result of

Accident investigation: