Last updated: 06/25/2007
|How is flying a helicopter different than an airplane?|
I suppose that to start with, we could start out with what seems to be the same! Both have sticks (although many airplanes have a yoke and control wheel instead of a stick, but it does essentially the same thing). Both have foot pedals. Both have throttles. Both have engines. Those are about the only things they have in common.
So what's the deal? Let's start with takeoffs. Airplanes need some kind of relatively flat surface (like a runway). The pilot points the aircraft in the right direction, applies power, and lets the aircraft accelerate until it reaches a particular speed, then pulls gently back on the stick to cause the nose to raise. Shortly thereafter (we hope), the airplane becomes airborne and starts to climb. If there's anything in the way, like wires, trees, or buildings, the pilot better be able to climb over them (or otherwise avoid them), otherwise it's gonna get ugly! There are some tricks to clearing obstacles, but basically all takeoff profiles are pretty similar.
Helicopters, on the other hand, don't need no stinkin' runway. Our takeoff starts with a hover. Once we're in that hover, we can taxi to some other point on the field, or start a takeoff. In either case, it doesn't matter what's under us, because we're now flying over it! From a hover I have a choice of three major takeoff profiles (and everything in-between).
If I have a runway, I may elect to do a "normal" takeoff. From the hover, all I do is lower the nose slightly and let the ship begin to accelerate. As it gets up to 15 knots (kt) or so, the nose wants to come up, but I don't let it. What I want to have happen is to be at 50 feet about the same time I hit 50 kt. After it gets up to 60 kt, I use the stick to find a nose angle which maintains that speed (best climb speed) until I reach my desired altitude. Then I move the stick forward to level out and accelerate to cruise speed. That's the safest profile in case of a mechanical failure.
Ok, but suppose there's obstacles? I might elect to do a max performance takeoff. When I'm ready to start, I raise the collective up until I reach the maximum power setting. I nose forward to start accelerating, but don't accelerate beyond 40 kt until I'm clear of the obstacle. After that, accelerate to the usual 60 kt and level off at the desired altitude.
But what if it looks like I can't clear the obstacle? In an airplane, that's a real "oh shit" moment, because you're going to crash. In a helicopter all I have to do is stop my forward motion by pulling back on the stick, then pull back a little more, lower the collective a bit, and fly backwards to where I started from. Beats the hell out of flying into a tree, doesn't it?
When all else fails, there's always a true vertical departure. It's the least safe if there's a mechanical failure, but sometimes it's the only option if you're in a very confined area. You just raise the collective to max power, go straight up until you're clear of the obstacle, then nose down like a normal takeoff. No big deal.
What about landings? An airplane needs that runway (or flat surface, anyway) again. The pilot tries to manage things so that he's sinking around 500 feet per minute (fpm), and at some fairly narrow speed range as he crosses the runway threshold. Too fast and the plane will float a long way before slowing enough to land. Too slow and the wing may enter a stall, in which case the landing will be very hard indeed (can you say crash?). Assuming the pilot has all that stuff right, he'll raise the nose (this is called the "flare"), and allow the airplane to settle down (gently, we hope) onto the runway. The time at which the flare should start is judged by the appearance of the runway ahead; he's looking for a particular sight picture to tell him when the time has come. Once that happens, we all hope he can stop the airplane before running off the end of the runway!
Helicopter pilots don't focus on the runway at all (assuming there is one). We focus on the exact spot we want to come to a hover over. On a runway, that might be where there is a taxiway intersection, it might be a helipad, or it might just be an arbitrary spot in a field or elsewhere. The descent is started by lowering collective, and I'm looking for the same 500 fpm initially, and an airspeed of 60-65 kt. As I get closer to my chosen spot, I will continuously manipulate the stick and collective so I get slower and slower as I near my spot. I don't have to reference the runway to do that! All I have to do is monitor where my spot is on the windshield. If it's moving down, I need to steepen my descent, if it's moving up, then my descent is too steep.
While there are an infinite number of choices in terms of a descent profile, terrain and weather influence the choice. If the landing area is confined, a vertical descent from a high hover may be the only way in. If the weather is hot and the landing is at a high elevation, I may not have enough power to come to a hover. So in this case we want a runway or other flat surface, do a very shallow profile with the intent to ease the ship down onto the skids at 15-20 kt if necessary.
To sum it up then, there's nothing very similar at all!