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ASN Wikibase Occurrence # 197228
Last updated: 20 October 2017
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Date:03-FEB-2016
Time:19:01
Type:Silhouette image of generic DH8A model; specific model in this crash may look slightly different
de Havilland Canada DHC-8-102 Dash 8
Owner/operator:Air Canada Express
Registration: C-GJMO
C/n / msn: 079
Fatalities:Fatalities: 0 / Occupants: 27
Other fatalities:0
Airplane damage: None
Category:Incident
Location:near Mont-Joli Airport, QC (CYYY) -   Canada
Phase: Approach
Nature:Domestic Scheduled Passenger
Departure airport:Montreal-Pierre Elliott Trudeau International Airport, QC (YUL/CYUL)
Destination airport:Mont-Joli Airport, QC (CYYY)
Investigating agency: TSB Canada
Narrative:
An Air Canada Express DHC-8-102, C-GJMO, operated on flight JZA8964 from Montréal/Pierre Elliott Trudeau International Airport (CYUL), Quebec to Mont-Joli Airport, Quebec, Canada.
While still on the ground at Montréal, the crew reviewed the weather forecast for the occurrence flight, which was scheduled to depart at 17:45. The weather forecast called for severe clear icing conditions and turbulence near Mont-Joli as a warm front was approaching from the west. Because the weather system appeared to be moving faster than originally forecasted, the crew expressed their concern to the company flight dispatcher about possible icing conditions at Mont-Joli, as well as the possibility that the return flight would not be able to leave because of the area of freezing rain that might be affecting the airport by the time the aircraft was scheduled to take off from Mont-Joli. However, the weather still met legal, as well as company, requirements for dispatch, so the crew and the flight dispatcher agreed that the flight could proceed as scheduled.
At 17:57, JZA8964 left Montréal with 24 passengers and 3 crew members on board. The pilot-in-command (PIC) was the pilot flying (PF), and the first officer was the pilot monitoring (PM). After take-off, the aircraft climbed to its cruising altitude of flight level 250. At 18:38, when it was 119 nautical miles (nm) west of Mont-Joli, the aircraft commenced the descent for a planned straight-in area navigation approach for runway 06. To minimize the exposure to icing and turbulence, the crew planned to fly a steeper descent.
At 18:43, the Montréal Area Control Centre controller enquired if the crew was aware of significant meteorological information (SIGMET) J8, advising of an area of freezing rain and severe icing below 6000 feet above ground level (AGL) in an area 30 nm west of Mont-Joli. The PM replied that they had seen the area on the graphical area forecast (GFA).
At 18:48, approximately 55 nm from Mont-Joli, JZA8964 levelled off at 14000 feet for a period of approximately 3 minutes to remain clear of cloud and turbulence. The crew reduced the airspeed from approximately 200 KCAS to 170 KCAS, to avoid being required to carry out a holding procedure because an aircraft was approaching Mont-Joli from the east. The descent resumed at 18:51, 50 nm from Mont-Joli, with an average rate of descent of 1100 feet per minute (fpm).
At 18:50, the PM contacted Mont-Joli Radio to request a pilot weather report from an aircraft on approach ahead of them. That aircraft was on approach for runway 24. When asked, the crew of the approaching aircraft confirmed that they had encountered turbulence starting at 4000 feet and that they had acquired visual contact with the airport at 2200 feet. When questioned about entering the cloud layer and possible icing, the crew replied "11000 feet," but did not provide any further details.
At 18:52, Montréal Area Control Centre cleared JZA8964 for an approach to Mont-Joli and transferred the flight to Mont-Joli Radio. On initial contact, the crew confirmed that they were 12 nm from the initial approach waypoint EPMAL, and were planning an area navigation approach for runway 06.
At 18:56, Mont-Joli Radio asked JZA8964 if they were aware of SIGMET J8, to which the crew replied that they were. Two minutes later, Mont-Joli Radio broadcasted SIGMET J8, in both French and English, over the mandatory frequency.
At 19:00, the PF asked whether it was normal procedure to broadcast a SIGMET live. Mont-Joli Radio replied that it is standard procedure to broadcast all SIGMETs affecting a 20 nm radius around the airport. The PF advised that the broadcast was a distraction while dealing with the higher workload associated with preparing for an instrument approach. A few seconds after this discussion, the aircraft passed the intermediate waypoint APNAM, as it descended through 4300 feet, with an approximate speed of 170 KCAS.
The power was reduced to idle, the gear was lowered, and the speed was stabilized at approximately 150 KCAS in this configuration with the autopilot in vertical speed (VS) mode. At 19:01, the airspeed gradually increased to 171 KCAS as the aircraft descended from 3340 to 2480 feet.
At 19:01:39, the aircraft encountered moderate turbulence when it was approximately 6.1 nm from the threshold of runway 06, descending through 2480 feet. A few seconds later, the maximum landing gear extended speed (VLE) of 172 KCAS was exceeded. The PF disconnected the autopilot, immediately levelled off, and, once the airspeed decreased to 160 KCAS, resumed the descent.
During the turbulence encounter, the PF felt a sudden change in elevator force and perceived this as a reduction of elevator control effectiveness. The crew did not declare an emergency during this event. Shortly after, the PF noticed that the TAIL advisory light for the outer left de-ice boot on the de-icing panel did not illuminate. Given the workload associated with the approach phase, the de-ice boot failure procedure indicated in the Quick Reference Handbook (QRH) was not performed at that time.
The turbulence decreased at 19:03, as the aircraft descended through 1540 feet. The crew lowered the flaps to 5° at 1380 feet and further lowered the flaps to 15° at 970 feet.
JZA8964 landed normally at 19:04 and taxied to the air terminal, where the passengers disembarked. The crew made no pilot weather report regarding turbulence or icing. Post-flight examination of the aircraft showed that the critical surfaces and airframe were free of contaminants and ice. The crew tested the de-icing boot system and noticed an indication of a possible malfunction of the outer left de-ice boot.

Findings as to causes and contributing factors:
1. The landing gear extended overspeed occurred because the aircraft encountered significant increased performance shear while flying out of a low-level jet with the autopilot engaged in vertical speed mode.
2. The combination of turbulence and shear contributed to the temporary difficulty with aircraft control effectiveness on approach.
3. It is likely that the expectation of significant icing, the high workload, moderate turbulence, and attention narrowing contributed to the pilot flying's perception that a reduction of elevator control effectiveness had occurred.

Sources:

http://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/2016/a16q0020/a16q0020.asp

Accident investigation:
cover
Investigating agency: TSB Canada
Status: Investigation completed
Duration: 1 year and 6 months
Accident number: A16Q0020
Download report: Final report

Images:


Cross-section of warm front and descent trajectory (TSB)

Revision history:

Date/timeContributorUpdates
08-Aug-2017 17:03 harro Added
08-Aug-2017 17:08 harro Updated [Photo, ]

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