Radar Love

“I'm showing heavy to extreme precipitation north, south and east of Anoka. West of the airport I'm just showing heavy precipitation. If you can't get through, what are your intentions?”

Decision time. Whenever an air traffic controller asks “what are your intentions?” it's time to sit up and pay close attention.

Saint Cloud, just a few miles behind me, was in the clear and likely to stay that way so I worked up my best “been there, done that, bored-silly” freight pilot voice and told the Minneapolis Approach controller I'd divert to STC if things got too hairy.

I'd been working the onboard radar hard since leaving Fergus Falls 40 minutes earlier and what I'd seen so far, both on the small display and out the window said it was prudent to continue.

A 30-mile wide line of thunderstorms was working its way through the Minneapolis metro area and a check of the ground-based radar before leaving Fergus hadn't been encouraging.

Yes, there were some small gaps in the line, but airborne I'd be hard-pressed to find them. And should I enter into instrument conditions, which was looking likely, chances were good that I'd stumble blindly into a thunderstorm, which is not a good place to be.

But as luck would have it, my airplane today was equipped with radar, which meant while I might not be able to see the weather visually I could use the radar to hopefully stay out of the worst of it.

Nearly all of the pilots at my company carry either a Garmin 396 or 496 as a backup GPS and full-time on-board weather source. The datalink weather those units can display is simply fantastic and the best safety improvement for aircraft I can think of since, well, maybe ever.

The drawback is the datalinked weather shows you what was, not what is, happening and while the  delay is generally no more than 5 or 10 minutes a thunderstorm can move far enough to ruin your day if you cut it too closely using the datalink. It's a good strategic tool, not so much a tactical one.

Since I'm new to the game and shockingly poor at the moment I've been doing without. But by spring, when thunderstorm season starts up again in anger, I'll have made the investment as well. 

Until then it's a matter of using what wits I have and my eyeballs to stay out of the worst of the weather.

So I continued on.

The view out my window approaching Minneapolis...

... and the corresponding view on the on-board radar. Looks like there's a small gap to shoot for, so I did.

The Minneapolis controller's clearance gave me a perverse chuckle: “Well, o.k. Do what you have to do, just keep me advised of any major heading changes.” Obviously, I was the only one in that particular section of sky and the clearance was the equivalent of “I've done my best to talk you out of it. Y'all be careful out there now.”

Before long the radar was nearly solid with returns and I was in solid instrument conditions but the rain was only light and the ride was smooth. I tilted the antenna up and down, trying to get a sense for where the heaviest rain was.

I'm no expert, but essentially the onboard radar returns a narrow horizontal picture, a slice if you will, of precipitation. Laterally, it's a relatively broad picture but horizontally it's narrow, so you have to adjust the antenna tilt to allow the radar to look up, or down, at the precipitation.

Normally, the drill is to adjust the antenna tilt until you're just getting a bit of ground clutter near the edge of the radar's selected range, which in turn gives you a reasonably accurate picture of any precipitation at the surface along your route.

It is far more art than science and I am a novice in both the art and science of onboard weather radar.

Normally, my cardinal rule is to stay visual when thunderstorms are part of the equation so they can be easily avoided. With the radar set to a 10-mile range and acting as my eyes I set off on my first attempt at picking my way through a line of thunderstorms in instrument conditions.

A few miles in a telltale “donut” appeared directly ahead, perhaps five miles away and I turned to the south.

Again, my lack of expertise is painful, but areas of extreme precipitation are strong enough to attenuate the radar's returns, creating an area on the display of precipitation, followed by an area that indicates no precipitation whatsoever which in turn is followed by an area of precipitation.

So, basically, what looks like no precipitation is actually an area of extreme precipitation and the resulting picture on the radar display looks like a donut. I stay away from the donuts.

As I turned right I noticed a large blank spot on the display without the disturbing donut shape so I headed for it. A few minutes later I broke out into a large hole, ringed by thunderstorms. I could see a good escape route to the southwest and just as clearly could see that Anoka, my destination just a few miles to the east, was getting pasted.

Better yet, I was in the airborne equivalent of my own back yard. I figure I'd spent maybe 1,000 hours within a few miles of where I was right now and I knew every road, clearing and major building by heart.

About the same time, ATC called and asked for my flight conditions. I had good news to report, I was visual with only light mist and a smooth ride but needed to stay where I was for a few minutes to allow the weather to improve over Anoka.

The controller couldn't have been better and asked if I'd like to hold over the Gopher VOR. I took a quick look and sure enough, Gopher was in the the clear so I headed toward it and entered the hold.

Two trips around the hold later (8 minutes, give or take) Anoka was reporting five-mile visibilities in light rain and I flew an easy VOR-9 approach and made my best-ever landing in a Cessna 310 thanks to the soaking wet runway.

On the ramp as the couriers unloaded my cargo it started pouring again and I sat in the cockpit filling out my paperwork and enjoying a spectacular lighting show overhead, thankful I was on the ground.

Without the on-board radar I never would have even tried the flight. With it I never flew into more than moderate rain and encountered nothing but a few minutes of light turbulence. Amazing.

The learning continues.