I don’t know about you, but most pilots who have never had the opportunity to take off straight up usually think that holding a cyclic and collective in your hands automatically confers upon you unheard-of preternatural powers. Well, it doesn’t work that way. Some of you have heard it, I’m sure. It usually goes something like: ‘You see that little clearing down there? Why, if we had to, I could put us down nice and easy right in there, with room to spare. Yessir, no runways for me!’
Well, hold the phone there, I say. Anyone who has taken more than a few casual helicopter flight lessons already knows there’s more to this picture than I first let on. Yes, helicopters are maneuverable as hell. But that maneuverability has a price, and some people unfortunately pay dearly for it. For starters, there’s this thing called a ‘dead man’s curve‘ (also known as the height-velocity diagram). It doesn’t come from the Barbary Coast, either, but rather from engineering facts. You lose your engine, and your fan becomes a windmill. Above a certain height (which increases as your airspeed decreases), you can theoretically milk rotational energy in your rotor blades just enough (assuming your timing is right) to cancel your precipitous plunge earthward and touch down ever-so-gently. For smaller training helicopters, that curve is measured in hundreds of feet above ground.
When I first took helicopter lessons, every invoice I got from the front desk at my FBO (in fact, everybody’s, including their much larger fixed-wing clientele) had this printed at the bottom: ‘Learn to fly straight up! See Todd, and learn to fly helicopters!‘ Well, maybe in a multi-million dollar, twin-turbine, corporate trophy aircraft with a high-inertia rotor system, but in a Robinson? No way, Jose! Take off straight up in the winter, into a thirty-knot headwind, maybe (and still, at some risk). But on a nice calm spring day? You’d have to be nuts!
CONFINED AREA OPERATIONS
If you’ve ever seen an air ambulance ‘medevac’ helicopter coming in for a landing to a hospital emergency unit, do they zoom in like an angry hornet out of the blue, over the treetops, and do a quick-stop over that landing pad? Well maybe in a combat zone, but chances are, even if those medics have someone grievously maimed back there, barely clinging to life, that pilot is going to be doing several things, and doing them very methodically. To paraphrase Robin Williams in ‘Good Morning, Vietnam‘, an accident here would not look good on your resume … Here’s what’s important:
Poles & Wires: Any time a helicopter pilot lands off-airport, he should treat it like a confined area landing, that is, one where the area is limited by terrain or obstructions. A medevac helicopter taking seemingly forever to arrive at an unfamiliar helipad — makeshift or otherwise — is actually doing two things: he (or she) is making a ‘high reconnaissance’, then a ‘low’ one. What’s the motivation? How about wire strikes — they’re one of the leading killers in helicopter flying. From a few hundred feet up poles are very hard to spot too. (That’s important to remember during any fixed wing forced-landing site selection, by the way.)
The Sucker Punch: Another good reason is that small clearings, especially on windy days, are another form of ‘sucker hole‘ for chopper pilots. Once you descend (especially if your descent rate is excessive) below a line of obstacles, you may lose your headwind and can drop below ‘effective translational lift.’ It’s right about then that one can find oneself descending into one’s own downwash (the so-called ‘vortex ring state‘) after which a power recovery is not possible. (Let’s just note here that the body does not recover well from spinal compression injury.) Besides that, approaches into confined areas are often done at steeper angles (like 15 degrees, and more) and can involve operations ‘inside’ that height-velocity curve, especially in the last few dozen feet. It’s not a comfortable place to hang out for very long!
During a high-recon, typically done at 500 AGL, you’d be checking for landing zone size, shape, obstacles, and wind. Generally, you want to try to visualize the trade-offs you might make to minimize turbulence, and maximize the longest dimension of the site versus the headwind you might have to partially sacrifice. You’ll be starting to plan what options you might have for a forced landing if you have an engine failure on approach or upon departure. You make tentative plans on how you’re going to get in, and how you’re going to get out. You get your pre-landing checks done, then go in for the low recon — it’s like a low approach followed by a go-around. Here is where you look more closely at landing zone slope, surface condition, possible obstacles (again), and double-check on possible squirrely low-level winds. You pick a reference point near the middle length of the touchdown area, both to avoid downdrafts from the upwind boundary, and too steep of an approach over the downwind boundary … and watch out for that tail rotor!. You also want to make certain that the ground looks firm enough (and even enough) to allow a safe landing. Then you circle around, like a normal pattern, and come in again from 500 feet and perhaps a half-mile out. (If it really looks safe, the area is already familiar to you, and you’re dead sure–note the implication inherent in that colloquialism–that you don’t need a re-play, you might opt to just end the low recon with a touchdown.) The idea here — as with fixed wing aircraft — is to keep as much normality as you can in any unfamiliar situation. Unless the landing zone is dusty, or is snow-covered — the thing to avoid here being white-out — then this is where you cautiously lower the collective, and land.
Whew! … Piece of cake, right?