What happened
On 21 January 1995, a Royal Air Maroc Boeing 747-400, registration CN-RGA, was undergoing de-icing preparations at the de-icing centre of Montreal (Mirabel) International Airport. The aircraft was being prepared for a scheduled service to Casablanca, Morocco, via New York. During the process, the engines were running, and the crew was communicating with the de-icing team via a specific VHF frequency.
Following a radio transmission heard by the crew stating "dégivrage terminé" (de-icing completed), the pilot requested taxi clearance from the apron controller. Believing the de-icing vehicles had cleared the area, the captain released the brakes and began to taxi. Approximately 26 seconds later, after moving 95 feet, the aircraft's horizontal stabilizers struck the telescopic booms of two de-icing vehicles. The impact caused the vehicles to overturn and the cherry-pickers to fall. While the two vehicle drivers sustained minor injuries, the three occupants of the cherry-pickers sustained fatal injuries.
The investigation
The investigation examined the communication chain between the flight crew, the apron controller, and the Canadian Airlines International Ltd. (CAIL) de-icing crew. It was established that the flight crew heard a message indicating de-icing was finished but did not receive a direct confirmation that the perimeter was clear. The investigation also looked into the training of the de-icing personnel, specifically the chief attendant, and the regulatory requirements for foreign carriers operating in Canada at the time.
Findings
- The flight crew initiated taxiing before the aircraft's perimeter was clear due to confusion in radio communications.
- There was a lack of established de-icing procedures within Royal Air Maroc.
- The CAIL de-icing crew failed to comply with established safety procedures.
- The chief de-icing attendant had not received formal training for de-icing aircraft with engines running.
- Communication equipment used during the operation was inadequate or inappropriate.
- There was a lack of operational supervision and failure to adhere to radio protocol.
- The regulatory framework at the time was less demanding of foreign air carriers than it was for Canadian carriers.
Safety action
Following the accident, several regulatory and procedural changes were implemented. ICAO published new guidelines for aircraft ground de-icing operations to standardize responsibilities and communications. New Canadian Aviation Regulations (CARs) were introduced to ensure foreign operators also maintain robust ground icing programs. Additionally, CAIL updated its procedures to require both visual and verbal acknowledgement before terminating de-icing operations and implemented new training and communication tools, such as cue cards, to prevent recurrence.