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Wheels Down

Even though the Space Shuttle doesn't deploy its landing gear until reaching an altitude of only a few hundred feet, not much more than 15 seconds before landing, that would probably make most general aviation pilots a little nervous.

Even though the Space Shuttle doesn't deploy its landing gear until reaching an altitude of only a few hundred feet, not much more than 15 seconds before landing, that would probably make most general aviation pilots a little nervous. But depending on the circumstances, even our own well-established points for putting out the wheels might not be early enough...

In aviation, we like to avoid tight spots. (And no, the Shuttle can't do a go-around if the gear doesn't go down.) For VFR approaches, to ensure that gear extension is performed on every approach, we usually don't wait 'til the last minute -- we usually put the gear down somewhere between mid-field and abeam the touchdown zone on downwind. Under instrument conditions, we usually do it at the Final Approach Fix on non-precision approaches, or at glide-slope intercept on precision approaches. Both visual and instrument versions involve "positional imprinting" and the familiar "GUMP" acronym. This also achieves another goal, which is descent management. With the proper approach power, configuration, and airspeed, just lowering the gear confers about a 500 foot-per-minute descent, allowing the balance of your time and workload for simply monitoring and fine-tuning.

Things usually become widely accepted because they work, which would especially apply to the critical procedural sequences related to landing an airplane. However, very few if any can be considered sacrosanct and there are always other ways to do things. Simply applying the conservative response rule means that it might sometimes be better to do it sooner. Let's say you're on an instrument approach and you have a situation wherein you are busier than usual, due to distractions (for example, from turbulence). In this case, you might prefer confirming that the gear is actually down, and you might rather get the pitch and trim inputs accomplished sooner, so you could subsequently be better able to focus on navigational challenges. Even for VMC situations, in a busy pattern you might be better off having to spend even those very few seconds of head-down time outside the pattern, rather than waiting until you're in it. (Of course in the situation where turbulence is involved, it is often better to get the gear down sooner, simply to expedite the process of slowing below maneuvering speed.) The one final benefit to doing it sooner is that you have fewer things to deal with at the same time, should the gear not go down as expected.

In visual conditions, you simply exit the pattern, go somewhere quiet to troubleshoot, run through the emergency gear extension procedure if you have to (and then come back and do a low pass to have someone double-check, before trying it for real). In instrument conditions, however, it gets more risky. If you lower the gear at the Initial Approach Fix instead, and there's a problem, you have just exempted yourself from the very unenviable position of having to track an approach course. Of course, concurrently, you'll have to plan to begin your descent at the appropriate time, monitor your time to the Missed Approach Point, converse with ATC about the problem, and go through the emergency extension procedure. The temptation to continue the approach could be overwhelming. And even if you discontinue the approach, ATC sends you somewhere quiet to sort it out, and you're spared from such a Chinese fire drill, you'll still have to follow vectors or perhaps a complicated missed approach procedure. (The obvious solution here is to forget about the gear for now and safely go where they send you, then deal with it, and come back and try again.)

To Err: The thing of it is, we're human, we easily forget things, and we make mistakes. It only gets worse when we get busy. As I'm sitting here right now, I just looked up at my AOPA Air Safety Foundation calendar for the current month (October, 2002) and noticed that they have Halloween on October 30. Nobody caught it; not even the eagle-eyed folks at the ASF. And I can guarantee you that none of them had their hands full flying an airplane when they did the press proofs.

It's one thing to forget the milk that your wife just asked you to stop off and buy at the grocery store, on your way home from work. It's something else again to forget the very thing around which we have supposedly ingrained expectations and a time-honored process: lowering the gear. Then again, speaking for my own gender, men have been known to forget their anniversaries. Now there's something a bit more serious than spilt milk (though perhaps without the punishment of a gear-up landing).

The one big disadvantage to getting it out of the way sooner is that it can represent a significant change to your sequence of previously-established configurations and power levels, which might add at least a peripheral distraction to your existing workload (i.e., old habits are hard to break). You have to weigh that against the potential situations where you might be better off getting some of the work out of the way sooner, in order to spread it out a little. (For an example of what I mean by a peripheral distraction, say you do put the gear down early on the inbound 45. You look at your airspeed a minute later, see it slower than you expected, and then realize "oh, yeah, that's right; the gear is down".) Speaking of devil's advocate, most gear problems aren't really gear problems; they're light bulb or micro-switch problems, so all that fuss is often over nothing. But you never know...

There are several different types of gear extension systems. With manual gear extension systems, there are no hydraulic lines, no wires; there's just a lever to shove. Pneumatic systems are uncommon, but have simple backups. Electro-mechanical systems don't need hydraulic fluid, but absolutely depend on the other kind of juice. And hydraulic system demands during any emergency extension scenario in a high-workload situation (such as single-pilot IFR) would involve head and hand-turning, manipulating an inconveniently located crank a few dozen times, while you fly an approach in IMC. It will have you feeling (and looking) like a frenzied Don Martin character. Electro-hydraulic systems need both electricity and hydraulic fluid. Here is one place where low-wing aircraft are anything but below the salt, especially with late-model Pipers. Here, a loss of hydraulic fluid will actually result in the gear extending, whereas a Cessna's must extend forward against the slipstream, and absolutely requires a hand pump (which only works if the hydraulic system does). Here too, if you've gotten in deep enough, landing gear-up may realistically be your only safe option.

THE BOTTOM LINE: There's nothing absolutely wrong or incorrect about the way you were probably taught. The basic concept here is to minimize any potential complications. Wouldn't you rather find out about a gear problem before you were in a busy pattern, or approach corridor, or during the busiest phase of an instrument approach? If there were a problem, would you not prefer having more time to deal with it, at a less busy time? True, you pass up that traditional imprinting point, and forsaking the usual "gear down, go down" times you'll have to use some other method of introducing a first approximation for your desired rate of descent (such as reducing power by three inches of manifold pressure, or 300 rpm). And of course, it will take you longer to get there. And in the vast majority of cases, while you're coming in more slowly, whether that's just a 45 to the downwind, from the IAF (or even if you don't extend the gear until the outbound leg on the approach), is the cost of a few extra minutes of flying time worth it for single pilot IFR, or peace of mind? It might be.

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