Maria Speaks Episode 12: How Helicopters Fly.
Hi, I’m Maria Langer. Welcome to episode 12 of Maria Speaks, How Helicopters Fly.
I thought I’d take a break from my usual computer related topics to talk about something I really enjoy doing: flying helicopters.
For most of my life, I thought it would be pretty cool to know how to fly a helicopter. In October of 1998 I had some extra money and a flexible schedule so I took the plunge and began taking flying lessons.
A lot of people think you need to learn how to fly an airplane before you can learn to fly a helicopter. That just isn’t so. I don’t know how to fly a plane, and frankly, I have no interest in learning. Helicopters have fascinated me since my first helicopter ride at age 8. Airplanes just aren’t as interesting to me. So I skipped the airplane stuff and went right to helicopters.
It took me a year and a half to get my pilot certificate. This wasn’t because I was a slow learner — at least I hope not. It was because I took lessons part time, only an hour or two a week. When summer came, I took the summer off. No one wants to practice doing hovering autorotations when it’s a 115Â°?F outside. I finally got my pilot certificate in April 2000.
I soon realized that I had a problem. I had a pilot certificate but nothing to fly. The closest place to lease a helicopter was Scottsdale, about 70 miles away. I’d drive down there, fly for an hour, and drive back. It wasn’t fun.
Fortunately, I had a good year and some extra money and was able to solve the problem. I bought a used Robinson R22 helicopter. And what I found is that the more I flew, the more I wanted to fly. As I’ve said elsewhere in my blogs, flying is addictive and I’m hooked.
Years went by. I got my commercial helicopter rating and starting taking passengers up in my two place helicopter. I got a summer job at the Grand Canyon flying LongRangers with up to six passengers on board. Then I decided to step up and buy a larger helicopter, and to expand my helicopter tour business. Today, I have 160 hours on my new Robinson R44 four place helicopter. And I still can’t fly enough to satisfy me.
If you like reading flying stories, check my blog. It has lots of stories about flying.
Anyway, what I really wanted to talk about was how helicopters fly. Most people are familiar with the way airplanes fly but few know anything about helicopters. I find myself explaining the controls to passengers all the time. Now I’ll explain them to you.
First of all, a helicopter does indeed have wings. But rather than having big, bolted-on wings like an airplane, a helicopter’s wings are its narrow rotor blades. My helicopter has just two of these blades, but they’re very long — about 16 and a half feet each. Other helicopters have three, four, five, or even more blades, depending on the design and size of the helicopter. Generally speaking, the more blades a helicopter has, the shorter they can be. Of course, if the helicopter is very big, the blades need to be big, too.
To understand how a helicopter’s main rotor blades work to produce lift, start by thinking about an airplane. Everyone has seen an airplane taking off — or has been in one when it took off. It rolls down the runway, gathering speed. This moves air — referred to as relative wind — over the airplane’s wings. The wing is shaped like an airfoil, so higher pressure builds up below the wing than above it, producing lift. Before the pilot reaches the end of the runway, he pulls the airplane’s nose up, which, in turn, changes the angle of attack — the way the wings cut through all the air rushing past. This increases the lift and the airplane takes off.
A helicopter’s rotor blades are also shaped like airfoils and they work pretty much the same way as an airplane’s wings. But instead of speeding forward to increase relative wind, the helicopter rotates the blades while parked. The faster the blades spin, the higher the relative wind. Once the blades are spinning at 100% RPM, the pilot lifts the collective, which changes the pitch or angle of attack on all of the main rotor blades. The result: the helicopter lifts off the ground.
Now I just mentioned one helicopter control: the collective. The collective changes the pitch of all of the main rotor blades the same amount — or collectively. This up-and-down lever is what a helicopter pilot holds in his left hand while flying.
There are three other controls.
The throttle, which is a motorcycle-style twist grip on the end of the collective, is what the pilot uses to add or reduce power. You see, the higher the pitch, the higher the drag. To overcome this drag without losing rotor RPM, the pilot must increase the throttle. Fortunately, most modern helicopters have a correlator or governor or some other kind of device that adjusts the throttle automatically as needed. This greatly reduces the pilot’s workload.
The cyclic is the control the pilot holds in his right hand while flying. The cyclic changes the pitch of each rotor blade individually as it moves to change the direction of the rotor disk. Think of it this way: the rotating blades are like a disk when they’re spinning. The cyclic tilts this disk in the direction you want to fly. Push forward, the disk tilts forward and the helicopter moves forward. Pull back and the disk tilts back and the helicopter slows down or backs up. Left and right do the same thing to the left or right. The cyclic is an extremely sensitive control and doesn’t need to be moved very much to get results. In fact, the hardest part of flying a helicopter is getting a feel for the cyclic.
The last controls are the anti-torque pedals. Remember Newton’s Laws? One of them says that every action has an equal but opposite reaction. Think about the main rotor blades spinning. If the blades spin to the left, the fuselage wants to spin to the right. So a helicopter has a tail rotor (or something equivalent). The blades on the tail rotor are mounted sideways so the “lift” pushes the helicopter’s tail to the right, thus pushing the nose to the left. The anti-torque pedals, which the pilot works with his feet, change the pitch on the tail rotor blades to increase or decrease this lateral “lift.” This keeps the helicopter from spinning out of control.
Sounds pretty simple, no? Well, it isn’t — at least not when you first start practicing it. You see, every time you make a control input with one of the controls, you have to adjust one or more of the other controls. For example, when you raise the collective, you increase drag on the blades, so you (or the governor) have to increase the throttle. But when you increase power with the throttle, the helicopter tries harder to spin to the right, so you need to add left pedal. Since you’re using up some of your power to generate more lift on the tail rotor, you might need more throttle. Get the idea?
One of the most difficult things to do in a helicopter is hover. Hard to believe but its true. It takes the average pilot 5 to 10 hours of practice time just to be able to do it. It took me about 7 hours. I thought I’d never be able to do it and then, one day, I just could.
Hovering requires that you make multiple minute control inputs all the time. There’s no “neutral” position you can put the controls into. It takes constant effort. Add some wind — especially from one of the sides or the back — and you’re working hard. After all, the helicopter is like a big weather vane and the wind just wants to push it around so the nose faces into the wind.
That’s the basics of flying a helicopter. There’s lots more to it, of course. But it isn’t that hard to learn. I like to tell people that if I can do it, just about anyone can.
One more thing. Lots of people think that if a helicopter has an engine failure, it’ll drop out of the sky like a brick. If the pilot does what he should be doing, however, that just isn’t so.
Here’s how it works. Suppose I’m flying along and my engine quits. My main rotor blades were spinning when the engine quit and they have lots of energy stored in them. There’s also energy stored in my altitude, airspeed, and weight. The first thing I do is lower the collective to reduce the drag on the blades. This helps keep them spinning. The helicopter starts a steep descent. I look for a possible landing area — a field, a parking lot, a dry river bed (we have lots of those in Arizona) — and steer towards it as I glide down. About 30 feet off the ground, I pull the cyclic back to bring the nose up and flare. This reduces my airspeed and transfers some of that energy to the main rotor blades. I level out and pull the collective up just before hitting the ground. Remember, pulling the collective up increases lift, so if I do it just right, I’ll cushion the landing. This whole procedure is called an autorotation and I’m required to demonstrate it annually as part of my FAA Part 135 check ride. I also had to do it to get my private and then commercial ratings. In other words, I have to prove that I can do it.
Of course, if I screwed up and didn’t lower the collective right away, drag on the unpowered blades would slow them to the point where they wouldn’t produce lift. Then I’d be in big trouble. Like a falling brick.
Have you ever gone for a helicopter ride? If you haven’t, you should. It’s quite an experience. If you do go soon, remember what I’ve told you and watch what the pilot does. If you’re sitting up front with him, don’t be afraid to ask questions once you’re under way. Most pilots like to talk to passengers about what they’re doing.
I remember a helicopter ride Mike and I took back in 1995 (or thereabouts) while driving cross-country. It was in Florida in the panhandle. There was a Bell 47 parked on the side of the road with a sign that said “Helicopter Rides, $25.” Mike and I climbed aboard and I sat in the middle. I told the pilot that I wanted to learn to fly a helicopter and when we were in cruise flight, he let me put my hand over his on the cyclic. He wanted me to see how little it needed to move to change direction. It was nice of him to do that for me.
Well, I could keep talking about helicopters all day, but I won’t. I’ll save some other stuff for another day.
I hope you enjoyed this topic. It was nice to take a break from talking about computers. I’d love to hear what you think about this episode and my podcasts in general. Write to me at firstname.lastname@example.org.
Thanks again for listening!