May 12, 2009

Real Enough

It was a dark and stormy night… I'm sitting in a nice G1000-equipped Cessna 172 on runway 15 at Martin State airport (KMTN), ready for takeoff. It's night time, and there are flashes of lightning illuminating the runway every ten seconds or so. Sitting there I reflect that a dozen or more years ago I sailed the Chesapeake — somewhere out there in the impenetrable darkness a few hundred metres off the departure end of the runway I'm on — for a week on a small sailboat based near Baltimore. Somewhere I still have the Approaches to Baltimore Harbor maritime chart that advises mariners to contact Martin State tower on VHF channel 16 if they'll be transiting the area off the end of the runway and they have a mast or superstructure higher than about 36'. I knew I'd heard of this place before.

More flashes of lightning. Good thing this isn't for real — I'm sitting at the California Airways certified G1000 sim again — but the pre-takeoff tension I always feel on IMC departures feels real enough. For me the transition to IMC out of visual flying immediately after takeoff is always by far the hardest part of real-world IFR flying, mostly because you're typically still getting a feeling for everything at that point — aircraft trim, ATC requests, slightly-unfamiliar instrument layout, orientation, etc. — and in cases like mine, you're a little rusty (I'm sure this is less a problem for the well-practiced out there). At least when you hit IMC on an approach or in cruise your aircraft is (hopefully!) well-trimmed, you're comfortable with the instruments, you've had time to get familiar with things, etc. (in fact, descent into benign IMC in those conditions is something I absolutely love).

John releases me into the void, and the sim gets gratuitously nasty by giving me a pretty realistic-looking bird strike on the way out, smack bang in the middle of the windshield. Talk about topical…. Never mind — on with the show. John repositions me away from the airport, and I dig up the charts for the selected approach: the Martin State (KMTN) VOR/DME OR TACAN Z RWY 15 approach. Take a look at it sometime — you'll see why John's chosen it for this evening's IFR currency workout. The approach is a continuous DME arc that ends at the runway, aligned with the centerline. Cool! Not in itself particularly difficult, but you need to keep pretty much exactly 14.7 DME from Baltimore VOR as you approach the threshold or you'll miss the runway; and DME arcs, while not difficult, can be demanding in cases like this, especially when carried on for a full 90 degrees or so — in a dark and stormy night.

I'm actually most interested in how the G1000 + GFC700 autopilot will handle the arc (I can fly a DME arc fairly well on my own), so when the sim can't find the approach in its database, I'm mildly irritated, but decide to press on regardless, using the raw OBS and DME display against Baltimore VOR, and hand-flying the last few miles. Nothing too strenuous, for sure, and it turns out to be a lot of fun, with a mild mental work out here and there, and it's gratifying to be at 14.7 DME when the runway comes into view just above the MDA. I land, surrounded the sort of weather I'd normally run screaming from in the air or on the Chesapeake, and we suspend the sim to prep the next approach.

* * *

The rest of the "flight" goes well — smoothly and without incident, at least. We'd started with the ILS into Oakland's runway 29 (only because I'll probably never fly it in real life, even though it's my home airport, because I don't really want to pay the landing fee :-)), then Oakland's RNAV 27L as an LPV approach (something I do in real life regularly), then the long arc into Martin State (above). And then — for light relief — the Silver City, Arizona (KSVC) LOC/DME RWY 26 approach which has DME arcs to the localizer from a couple of the outer IAFs. This time the approach is in the database, and I watch with my usual sense of amazement as the G1000 simply flies the plane around the arc smoothly with the autopilot coupled. Well, nothing's ever quite that smooth in the world of sims (otherwise what would be the point?), but nothing went horribly wrong, and, as always, I learned a lot about systems management and the devil lurking in the odd approach detail here or there. Plus it's a fair bit cheaper at the moment than going out in a real G1000 C172…

I've flown that DME arc at Martin State-- it is kinda fun. I flew it in my 172 G1000-- and it also did not have the arc in the database, so I had to fly by hand. For the record, I think there are several other approaches with lower minimums, etc. for that same runway-- so in a "real" situation, you probably wouldn't choose the arc (though it is pretty cool).
Yeah, it's a cool approach, that's why we chose it :-). (I'm jealous that you've actually done it in real life). But it's true that it'd probably be last on my list in hard IMC…
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