Date:	Thursday 6 November 2014
Time:	21:30
Type:	de Havilland Canada DHC-8-402Q Dash 8
Owner/operator:	Air Canada Express
Registration:	C-GGBF
MSN:	4433
Year of manufacture:	2013
Engine model:	Pratt & Whitney Canada PW150A
Fatalities:	Fatalities: 0 / Occupants: 75
Aircraft damage:	Substantial, repaired
Category:	Accident
Location:	Edmonton International Airport, AB (YEG) -   Canada
Phase:	Landing
Nature:	Passenger - Scheduled
Departure airport:	Calgary International Airport, AB (YYC/CYYC)
Destination airport:	Grande Prairie Airport, AB (YQU/CYQU)
Investigating agency:	TSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Air Canada Express flight 8481 departed from Calgary International Airport at 19:47 on a scheduled flight to Grande Prairie Airport.
During takeoff, as the DHC-8-402 aircraft approached rotation speed (Vr), there was a noticeable vibration that ended once the aircraft was airborne. Once the landing gear was retracted and the aircraft was established in the climb, the flight crew discussed the vibration. The cabin crew informed the pilots that a tire had blown.
Company maintenance and operations crews at its dispatch centre were contacted. Because of strong crosswinds, returning to Calgary was not an option, and a decision was made to land at Edmonton International Airport and to switch aircraft owing to the ruptured tire. Maintenance personnel recommended that a hard landing be avoided.
Air traffic control arranged for the aircraft to level at 13000 feet above sea level. The cabin crew confirmed that the number 3 tire had blown and revealed that something had struck the aft fuselage.
Throughout the approach phase of the landing sequence, the landing gear control panel indicated that the landing gear was down and locked. The aircraft touched down very lightly on runway 02 at Edmonton. As the wheels spun up, a pronounced vibration shook the aircraft 2.4 seconds after initial touchdown; while the nose wheel of the aircraft was still airborne, the right main landing gear collapsed. The right-side propeller blades struck the runway, and all were sheared on contact. One large section of a propeller blade penetrated the aircraft cabin next to passenger row 7. At the same time as the propeller contact, the nose landing gear came down hard and its tires ruptured. The aircraft slid slightly to the right and came to a stop off the right edge of the runway, approximately 3200 feet past the touchdown point.

Findings as to causes and contributing factors:
1. The number 3 tire ruptured on takeoff, most likely as a result of impact with a hard object.
2. During landing, the failed number 3 tire was spun by contact with the ground and was maintained at a rotational speed that was the same as or very close to one of the natural frequencies of the main landing gear. This caused the lock links to trigger the proximity sensor electronic unit to de-energize the solenoid sequence valve, thereby relieving system pressure from the extend port of the unlock actuator.
3. The excessive vibration caused the lock links to overcome the force from the downlock springs and unlock the stabilizer brace as a result of gear dynamics, which led to collapse of the right main landing gear.

03:13 UTC / 20:13 local time:
CYEG 070313Z 29004KT 270V340 15SM FEW010 BKN058 OVC110 05/03 A2961 RMK SF1SC5AS3 SF TR SLP049

photo (c) TSB; Edmonton International Airport, AB (YEG/CYEG); 07 November 2014

photo (c) TSB; Edmonton International Airport, AB (YEG/CYEG); 07 November 2014

photo (c) Reinhard Zinabold; Toronto-Pearson International Airport, ON (YYZ/CYYZ); 03 June 2013

photo (c) Timo Blossfeld; Calgary International Airport, AB (YYC/CYYC); 07 July 2014

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