Part II of The ANN Interview With Avidyne's Dan Schwinn

By ANN Senior Correspondent Kevin R.G. "Hognose" O'Brien

• Read Part One

Aero-News: Can you give me an example of something, a way they used it (surprising uses of Avidyne's technology)?

Dan Schwinn: I'll give you -- which one?

Aero-News: Well, we'll come back to when they were doing things that were more difficult than they need to be, because I do want to talk about training on these sophisticated systems. But talk about something they're doing, that's something you didn't expect. Did these guys teach you a capability of your system that you didn't know about, in a way?

Dan Schwinn: Well, one of the big debates around datalink weather has been on the tactical versus strategic use of datalink. Tactical
meaning: ten degrees to the right, ten degrees to the left, have to go around this little spot, take a left around this little spot, take a right around that one. Strategic meaning, line of storms is here, I'll go over it and I'll miss the whole thing.

Aero-News: Almost, a preflight planning versus inflight planning use of it?

Dan Schwinn: It might be in flight, but... in the example that we had last week, we were coming back from Canada. I was sitting in the back.
We had a bunch of guys, two pilots sitting in the back, two in the front. That's like three more pilots than you really need to have on board. (Dan begins sketching on a whiteboard).

Aero-News: Yeah, a bunch of people fidgeting on an airplane.

Dan Schwinn: Yeah. So, it's normal northeast conditions -- you remember, when we had that bad weather last Wednesday and Thursday. So, we're going from here, Canada, down to Bedford. And there's a line of storms in between.

Now, strategically, by looking at this, you could have done either the down and around here (pointing to the southwest end of the storm line), but this went down pretty far south. You could have done the up and around here (pointing to the NE terminus of the storm line). Both valid.

And, of course, this stuff is all moving. And either of these routes is probably fifty percent more mileage. So instead what we do -- and I'm just sitting in the back, kind of enjoying the show -- is, we go right at this (points at a possible fault line in the line of storms), we come over here, tack back like this. (Indicates a zigzag path through the storm line).

The narrowest gap here, between the greens, is maybe half a mile. And we're up over Vermont, or someplace like that. Now, the datalink has two kilometer, one mile resolution on the XM. And there's slant angle, and there's "where is the precipitation really currently" -- we're flying around 8,000, or something like that.

And these guys are going, "We're going to navigate right through this, and there's not going to be anything there, because, look, it says so on the datalink."

And it was true! But it's not definite that it's going to be the case.

Aero-News: It's a probabilistic thing that there's not going to be anything there, perhaps.

Dan Schwinn: Right. Now as we're doing this, there's a big blob of red [most serious activity] here. ANd we're trying to get here as fast as possible. And the question is, do I go way out away from this thing -- do I leave it ten miles? -- or do I slice right by it? And the answer is, if there's convective [activity] in there, you stay ten miles away.
but if there isn't? Go right by it. It's just a bunch of heavy rain.

And that's where the lightning reporting comes in.

Aero-News: It's all which stage of a thunderstorm you're in.

Dan Schwinn: Well, if there's [even] one there. maybe it's just heavy rain. So, in this case, we saw a few little guys down here [lightning strikes far from the precipitation and the planned flight path] and nothing up here [near the flight path]. So we went a little bit closer to it and the ride was perfectly smooth. The whole way, a perfect ride.

It was a textbook demonstration of what you can do with datalink that you could never do without it. You would have been vectored around.
None of this stuff [pointing at the cells that were zigged and zagged around] was going to kill you, either, but you could have had a miserable ride.

Aero-News: And the other thing is, you could have been in the air for half again as long.

Dan Schwinn: And you could have been a lot more worried about it! I mean, we're just cruising along having a ball. It's all there -- you know exactly -- you've got total knowledge. You talk to ATC, you're not asking them, you're saying, "well, we want to deviate 20 degrees right for 30 miles and then we're gonna cut back to the northeast for about 10 miles and then we're gonna head directly to destination, is that OK?" [Puts on ATC voice]: "Sure, sounds like you guys know what you're doing."

You know, they don't care, as long as you're not in a heavy corridor.

Aero-News: So when you're conceiving this integration of systems, you never imagined that people would do these things with it?

Dan Schwinn: You know, you kind of imagine it but you don't really know what's going to happen. And the thing that I found particularly interesting in listening to the discussion between the two guys who were flying -- remember there were four of us pilots, two guys flying and two guys with color commentary in the back -- and I'm sitting there and they're saying, "yup, we're going to be able to go right around it like this and like that," -- and I'm sitting there going, "What do you guys think the accuracy of those green and yellow areas is?"

"Well, it's up there on the screen, it must be exactly right!"

"Well, what age do you think it is?" and the guy looks up on the thing, and there's a little number, and he says, 'Well, it's three minutes old."

But that three minutes is three minutes from when it was composited, which is not necessarily from when the raindrop was formed. It's not much longer than that, but it's just kind of funny to listen to people.
"It's on the screen so it must be exactly correct."

Aero-News: Also, it's possible that -- you know a great deal about what feeds into the system. You have all these different radars on the ground, that are going together, it's all being composited into one picture. And every one is on its own sweep...

Dan Schwinn: And depending on how far away you are from the radar, you're at a different slant angle, and a different slant angle with a different altitude --

Aero-News: Same issue you have with DME or anything that's a line of sight radio signal.

Dan Schwinn: But the point is that -- and this is one that nobody realizes -- you're flying along at 3,000 feet and you look at your screen and your radar's perfectly clear, and then you fly into a rain squall -- "What happened?!" Well, you're 150 miles from the radar, and it can't see anything  -- this whole rainstorm is only 8,000 feet tall.
And the radar's shooting right over the top of it.

Aero-News: Because of the curvature of the earth, sure.

Dan Schwinn: Nobody thinks of that.

Aero-News: Now, is that something -- is it possible that we're going to give pilots overconfidence because they see, "The red ends here and the green ends here, and that's the way it is."

Dan Schwinn: But here's the thing. Are you going to fly through a red rainstorm that's 7.000 feet tall? Are you gonna get hurt? You're gonna get wet, you're not gonna get hurt. The only thing that's really going to hurt you is if there's convective.

I mean, all this stuff -- you can separate this weather business into two things. Or maybe three. One is whether you get wet, two is whether you have a rough ride, and three is whether you actually enter convective weather.

The third one --

Aero-News: That's the one that breaks airplanes and kills people.

Dan Schwinn: -- is the one that breaks airplanes. And all of these systems can help you avoid that. A few lightning specks... the red... but in fact, they're giving you indications. They're giving you false positives of convective.

It could be heavy rain or it could actually be convection. There's no way to tell the difference on an onboard radar or ground-based radar.

Aero-News: You can't see air movement with radar.

Dan Schwinn: That's where the 'sferics are kind of nice.

It's an evolving area.

To Be Continued...

FMI: www.avidyne.com