Aviation In Canada

Thursday, May 05, 2005

"Descent at your discretion..."

A lot of people already know the meaning of the phrase in the title. The question I have today, fishing for comments, relates to a common radio exchange in the Moncton FIR, though I can't say how common it is elsewhere.

Pilot: "Moncton, ACA123 request descent."
ATC: "ACA123, descend to one zero thousand, altimeter two niner eight seven."
Pilot: "Cleared to one zero thousand, ACA123. Confirm that's at our discretion?"

This makes me wonder. First off, when a pilot calls for descent, I assume he's ready for descent, either now or in the next minute or so. And when the same pilot above starts descent from FL350 a mere 100 NM from destination, does he really intend to level off somewhere in the interim? Additionally, why would he ask to confirm that descent is at his discretion, when there was no mention of the term in the clearance issued following his request?

I will often offer descent clearance to a pilot, traffic permitting, of course, before the pilot asks for lower. When I do, I'll state that descent is at pilot's discretion. It saves a radio transmission, keeping the frequency clear for when I want to use it, and gives the pilot the flexibility to commence descent when he's ready. But when a pilot asks for lower, I find it strange that he would ask if his descent clearance he just received would be at his discretion. If the pilot would ask in his request, "request descent at pilot's discretion," this would make a whole lot more sense to me, regardless of when he was asking for it. I would now know what to expect from him.

Is there something I'm missing?