Aviation Investigation Report A98H0003
1.9.4 Emergency Communications
When pilots transmit a message to indicate an abnormal situation or condition, the degree of danger or hazard determines the terminology to be used. A situation in which the safety of the aircraft or of a person on board is threatened, but that does not require immediate assistance, is a condition of urgency. The internationally recognized spoken expression for urgency is "Pan Pan," which is spoken three times in succession. A situation in which the safety of the aircraft or a person on board is threatened by grave and imminent danger, and that requires immediate assistance is a condition of distress. The internationally recognized spoken expression for distress is "Mayday," which is also spoken three times in succession. If the pilots already have the ATS controller's attention, it has become common practice for them to declare an "emergency," instead of using the term "Mayday." This practice is accepted within the aviation industry.
Nav Canada requires controllers to comply with the directives about emergency communication contained in the ATC MANOPS, Part 6, "Emergencies." Subpart 601 instructs controllers to provide assistance to the aircraft in distress, to use all available facilities and services, and to coordinate with concerned agencies. As well, the ATC MANOPS advises that controllers should keep flight crews accurately informed and exercise their best judgment in difficult situations.
The pilots of SR 111 and the controllers communicated in normal tones in all of their communications prior to the pilots declaration of an "emergency" situation. When the pilots declared an emergency at 0124:42, there was a slight elevation in their voices that reflected a higher sense of urgency. From the time of the Pan Pan call at 0114:15, the controllers at Moncton ACC treated the situation as they would treat an emergency; that is, they responded in the same way they would have had pilots made a Mayday call. Moncton ACC responded to the diversion situation, and their actions were in accordance with their standard practice.
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