VFR Flight Following and Altitudes
Yesterday, for example, I spoke with a pilot inbound to Charlottetown, PEI. He was at 5,500 feet in a C172, and seemed to me to remain there for a long time, and pretty close in to the airport. I asked him when he planned to descend, and he said, "As soon as you let me down." Ok. I try to be diplomatic in such situations and hope that my words and tone convey the message properly wihtout sounding too trite. The basics are needed here.
It's unlikely that this same pilot would have considered a need for permission for descent if he weren't talking to me for flight following. So why now? It seems that some pilots think ATC is always the one in control once their radios are tuned to their frequency. This isn't always the case. The rules are the same whether in contact with ATC or not, and all depend on the class of airspace in which the aircraft is operating. In the case of CYYG above, the entire area around is Class E airspace, including the control zone itself. This means IFR aircraft require a clearance (and therefore permission from ATC to descend), but VFR aircraft do not. Whether in contact with ATC or not, the pilot may climb or descend at pilot's discretion. Other rules still apply, mind you, such as cruising altitudes and direction of flight. The one thing I will ask of a VFR pilot in contact with ATC is that he should advise ATC when he plans to descend. The controller may be working other aircraft in your area and may have already determined that you are not traffic for other flights since you last checked in and told him you'd be maintaining 4,500 enroute to Timbuktu. Once you change your mind and descend, you suddenly become an issue for the other guy at 4,000 feet, 3,500 feet or whatever.
So the important thing is class of airspace, not contact with ATC. If you're in Class D, C or B airspace, there is a whole new component introduced. In each of these cases, permission from ATC is required, and if you want to climb or descend, it's as simple as asking. I understand American pilots are subjected to a different mindset. Especially in busier areas, controllers can be a bit snippy from time to time if requests are made. We in Canada are often confronted with pilots who will simply not request descent, but rather wait until ATC initiates a clearance for it. This often includes American VFR pilots, since, it seems, they don't carry enough information to determine what class of airspace they're in and don't want to do anything wrong. I can appreciate this, but I also believe in carrying charts and having a certain amount of situational awareness.
It's a good time to refresh your memory on what is required of you for each class of airspace you intend to fly in, if you're not already familiar. Then again, perhaps another look at the rules would be in order anyway, since you never know what you may "learn" again for having forgotten or simply not had the occasion to use.