When weather permits, VFR is often a good choice: it gives you more control over your route and altitude than you would have IFR, generally speeds up the trip (since you don’t have to be spaced and sequenced as much during departure and arrival, especially at busy airports), makes it easier to avoid icing in winter time, and just all-round feels nice. When there are clouds somewhere along the route, however, you have to make an important decision: VFR underneath, or VFR over the top?
The decision is hardest when the clouds are right around the best cruise altitudes for your plane, say, 3,000 to 8,000 feet for a normally-aspirated piston aircraft like my Warrior. If you fly underneath, you could end up dealing with precipitation, marginal visibility, hills and towers, and (of course) lots of turbulence; if you fly over the top, you could end up dealing with strong headwinds, and, most importantly, you could get stuck up above an overcast. For my return to Ottawa from Teterboro, mindful of the Catskill and Adirondack mountains along my route, I chose to go on top at 9,500 feet for the smooth air and lack of mountains to fly into; and yes, I got stuck.
I knew that things weren’t going my way when the broken cloud layer closed up to an overcast near Saranac Lake, NY instead of breaking up to scattered. I checked the Massena, NY ASOS (I had planned to descend there, over the flat land) and it was also calling overcast; the Ottawa ATIS, which was coming in from 100 miles away at that altitude, was calling broken clouds. Halfway between Saranac Lake and Massena, I was handed off to Montreal Centre for flight following, and I talked to them about the situation, warning that I might need an IFR clearance to get down. The controller insisted that the latest weather for Massena was showing scattered (as I’m sure it was, as far as the data available to the controller went), so I said that I could wait until closer to Ottawa.
In the end, I got my clearance for an IFR descent inside Ottawa Terminal airspace. I knew that the cloud layer was too thin to hold any large, supercooled water droplets, so icing wouldn’t be a major issue; still, I activated all of the meagre ice-prevention gear at the Warrior’s disposal before starting down: pitot-static heat on, carb heat full, heat on defrost. The clouds were less than 1,000 feet of stratocumulus, and I was through them and back VFR in a couple of minutes, as expected.
Now, let’s try some what ifs. What if I hadn’t been flying an IFR-capable aircraft, or weren’t IFR current? There was no hole that a VFR pilot could have used — the biggest one I saw near Ottawa was about 50 meters long, and mostly there were no holes at all. Canadian VFR pilots require a special rating and 15 hours instrument time to fly VFR over the top, but US pilots have no such requirement. If I had been a new American PPL, with (say) 70 hours experience, arriving at Ottawa stuck on top of the overcast with only my required 30 minutes VFR fuel reserve, how would ATC have dealt with me? Obviously, Montreal didn’t have up-to-date information about Massena — might they have sent me somewhere similar, where I might have found nothing but more overcast? The centre controller could tell that I wasn’t in trouble by my calm tone of voice and the specificity of my request (“I might need an IFR clearance to get down” rather than “I need to find some way to get down” or even “oh my god! oh my god!”), so I was handled much more casually than my hypothetical VFR-only pilot. I’d like to know how they would have handled that pilot, who might have been getting more and more panicky as the fuel got lower and the cloud layer stayed solid underneath.
My flight met all the requirements for VFR over top — the sky was clear at my point of departure, Massena was forecast scattered, giving me a way down, etc. — but I still got stuck. Does VFR over the top make sense for non-instrument rated pilots? Certainly, it’s safer than scud running around mountains, but I would not have wanted to be up there without the IFR option. At least a much bigger required fuel reserve would be a good idea.