Plane & Pilot
Tuesday, November 6, 2012

IFR Strategies In Convective Weather


A tactical flight from coast-to-coast in a Columbia 400 from above the weather to underneath the overcast


At this point, Erie was covered by rain but I assumed correctly, that the weather would be better by the time we arrived.

Eventually, wandering at 15,000 feet through beautiful white peaks and valleys would have required climbing to remain mostly VMC. One excursion through what looked like a benign buildup but lifted the iPad in my lap up to about chest level was encouragement to descend to VMC conditions below. I informed the controller of my request, and we negotiated a stepped descent while he coordinated with the next sector.

Underneath
At the start of this tale, I said that it wouldn't be my IFR skills that shepherded us safely to our destination. Once below the overcast, we had a whole new ball game, and this was to be the most challenging hour of our entire trip. I considered canceling IFR so I'd have free reign to avoid the virga and heavy rain shafts that were scattered around us. But I wanted ATC's attention and assistance, so I elected to remain IFR. From this point on, the challenge was to remain in VMC conditions and studiously avoid anything that looked remotely dangerous.

The hour-plus that it took to finish the flight to Erie illuminated a number of lessons to keep in mind if you try to navigate in VMC under an overcast with limited visibility and scattered thunderstorms, turbulence, virga and the like.

1 If the forecast is for convective activity, your best bet to avoid cumulus activity is usually to fly early in the mornings. The earlier, the better. Evenings might work, as well.

2 Flying VMC below an overcast, especially with occasional or continual low visibilities, requires constantly being heads up. You're watching for weather, clearest routing, indications of turbulence or other weather, and for other aircraft. The point is, you should be looking outside and not surprisingly, while avoiding obvious weather, I found that I was sometimes substantially off my desired course. The moving map was my salvation, and if you don't have a moving map, consistent and accurate navigation is critical. Even if you know the area, it's very easy to get confused and lost when the visibilities are low and weather is an issue.

3 It's obvious when you think about it, but sometimes not so obvious when you're flying, but if possible, always deviate upwind of convective activity, cells, virga and the like. Two reasons: First, if you're upwind of the weather, it won't be moving in your direction, so you're usually safer. Second, there's typically less turbulence on the upwind side. Sometimes, especially with strong winds, you can be miles downwind from a thunderstorm and still feel the effects.

4 There's one very basic tenet I learned while flying with my father from Vero Beach, Fla., to Phoenix, Ariz., when I was only 16. If you plan to file and fly IFR in convective conditions, especially with widespread IMC and embedded cells, always remain VMC. My father and I learned, oh did we learn, to stay away from IMC conditions when there are embedded cells.

5 If you're having trouble holding altitude and/or require continually changing heading to avoid the uglies, request "block altitudes" (especially at higher altitudes) and request a broad maneuvering diversion clearance. You won't always be able to get them, but you absolutely won't get them if you don't ask.



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