Propeller Blade Fracture Leads to Cabin Depressurization on ATR 42

Q: What aircraft was involved and where did it happen?

The accident on 1994-03-13 involved an Inter-Canadien ATR 42-300 C-GIQV, operated by and Cabin Depressurization, at Val D'Or, Quebec 53 mi SE, CA.

On March 13, 1994, an Inter-Canadien ATR 42-300 C-GIQV operated by and Cabin Depressurization was involved in an aviation accident near Val D'Or, Quebec 53 mi SE, CA. Investigators recorded the probable cause as: Corrosion pitting had occurred on the surface of the taper bore of the No. 2 blade as a result of water combining with chlorine deposits on the cork in the taper bore. The chlorine was associated with the bleaching of the corks during their manufacture. This summary draws on records from the Transportation Safety Board of Canada (TSB).

Sourcesthe Transportation Safety Board of Canada (TSB)Primary reportUpdated 1785068748Data API Editorial standards

On March 13, 1994, an ATR 42 suffered a right propeller blade fracture at 17,000 feet, causing cabin depressurization. The crew landed safely at Dorval. Investigation traced the fracture to corrosion pitting from chlorine deposits on corks.

History of the Flight

On 13 March 1994, an ATR 42 aircraft, registration C-GIQV, operated by Inter-Canadien as flight 1678, departed Val D'Or Airport, Quebec, en route to Montreal International (Dorval) Airport, Quebec. On board were two pilots, one flight attendant, and 23 passengers, totaling 26 occupants. The flight proceeded under instrument flight rules. At approximately 17,000 feet above sea level, a violent explosion occurred as the No. 2 blade of the right propeller fractured in flight. The blade penetrated the fuselage, causing cabin depressurization. The crew executed emergency procedures, including engine failure checks and a descent, and landed at Dorval without further incident at 1116 EST.

Injuries to Persons

No fatal or serious injuries were reported. Two passengers experienced ear discomfort and nausea due to the depressurization. They were taken to a hospital for examination and recovered with no permanent damage.

Damage to Aircraft

Damage was confined to the right side of the aircraft aft of the propeller disc. The front portion of the right engine separated from the remainder, with three engine mounts torn away. A vertical cut measuring 104 cm by 2.5 cm was found on the fuselage. The seat adjacent to the cut was partially cut, and two landing gear hydraulic lines were slightly bent.

Analysis

Investigation determined that corrosion pitting had occurred on the surface of the taper bore of the No. 2 blade. The corrosion resulted from water combining with chlorine deposits on the cork used in the taper bore. The chlorine originated from the bleaching of corks during manufacture. One corrosion pit initiated fatigue cracks that caused the blade to fracture. The fracture point was not detectable during preflight inspections, and no abnormal vibrations were recorded. The crew responded appropriately to the depressurization and engine failure, deciding to continue to Dorval after assessing damage and aircraft handling.

Cause

Corrosion pitting had occurred on the surface of the taper bore of the No. 2 blade as a result of water combining with chlorine deposits on the cork in the taper bore. The chlorine was associated with the bleaching of the corks during their manufacture. One of the corrosion pits was the point of origin of the fatigue cracks that caused the propeller blade to fracture.

Probable cause