Induced Drag: The Voices of Experience

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Debbie Gary

The less drag a plane has on it, the faster it can fly, potentially. The shape of a plane — boxy versus sleek — affects the drag. The things you hang on your airplane — camera mounts, smoke generators, wing walkers — increase the drag. But, for an air show pilot maneuvering close to the ground, where every knot counts, the one kind of drag you care about, every minute, is the one that you feel in your body, when you pull Gs, and control with your hand when you move the stick. It is induced drag.

A tiny release of back pressure to reduce this drag, can get a stalled plane flying again. Induced drag increases with rough handling and decreases with smooth flying and a sensitive touch. Truly understanding how your hand on the stick controls induced drag can mean the difference between life or death on a pull out.

Wayne Handley

“You control induced drag from the cockpit by your drag lever, which is your elevator. An airplane cannot stall if the wing is unloaded, if it has zero Gs on it. How hard you pull the stick is how you control induced drag, so unload that sucker. Just unload it. If you go to zero G, you are not creating any induced drag.”

Kirby Chambliss

“Skip Stewart and I were doing Tinxtix. They weren’t blowing up stuff, yet, but we were both in high alpha, hanging on the props, going down the runway together. And, in El Salvador, right on the end of the runway, it drops off into a 250 foot ravine that is basically where two mountains come together. There is no bottom as far as something you can land on, or even a flat surface; it is all jungle.

“We were hanging on the prop, maybe had 40 knots, I don’t know, but just hanging on the prop. Just moving across the ground with the wingtip probably 3 or 4 feet above the ground, just cruising.

“Then, just as we went across the end of the runway, my engine went, Whop! Bam! Just stopped. So, from the time it stopped to the time I hit the first tree, if it was ten seconds, I’d be surprised.

“I dumped the nose the first time and tried to load the wing. I know the airplane like the back of my hand, but I am usually loading it with power on. So, without power, I tried to load it and it wouldn’t load. Dumped it again, got it to load, got the wing loaded again; in other words, I got it flying. Probably had three seconds.

“Then, I intentionally hit the left wing on a tree and took two feet off the left wing, then I took two feet off the right wing, then knocked the engine off the front. I got the tail. I got about everything you could. Instead of taking one really big hit, that would have probably croaked me, I took three smaller ones and then got out of the airplane. It was upside down, on the side of the hill, still 15 feet down from the very bottom.

“It was all just a jungle of trees and it was pretty steep. The only thing I did was bruise my right arm. So, I was able to crawl out as I had just enough room between the canopy and the ground.

“I was really lucky, I’ll tell you. I only had a few seconds to get the airplane flying. Obviously, falling is not good, so to be able to get the airplane to fly…I just had a couple of seconds to do that. I think that is probably what really saved me, just instinct to basically take over. Boom, nose down, load it, nope, unload, second time load, got it flying, left wing, tree, bang! I had time to say two bad words and think in my mind, ‘Oooh, this is going to hurt.’ And that was about it.

“You’ve got to fly the biggest piece down, they say. When you are vertical at 250 feet when it quits, you’ve got to get the plane flying first, then fly the plane.” 

Greg Koontz

“You can unload the wing a lot more in ground effect with the wheels almost touching the ground and maintain more speed for the next maneuver because you can reduce the induced drag. You can actually accelerate. Just watch yourself closely low to the ground how much you can unload the airplane to stay there. You can watch the airspeed pop up.

“Another place you can change induced drag for your benefit is sometimes at the top of maneuvers. I’ll use a humpty bump, for instance, to go over the top and actually come out with a little more energy than if I keep using a hammerhead. I can unload the wing completely and float over the top and actually the plane is going to try to accelerate because there is no load on the wing. If you sit there at zero G, you are going to have that angle of attack right at zero and the airplane will accelerate better than if you are pulling hard over and down, which would tighten your radius and keep the wing loaded and decrease the amount of your acceleration. By letting it float, the airplane will make a wider radius and accelerate.

“If you watched Bobby Younkin…he used to take off in the Super Decathlon and start from the ground and within about five maneuvers he was doing outside loops. He was building energy with every maneuver and that was the kind of thing he would do constantly. Another thing, I used to always pop the plane in the air around 60 and hold it in ground effect building up speed. But he would roll the wheels with no lift being created with the tail high in the air to accelerate all the way to 100 and I started trying it and you will accelerate to 100 a lot faster. It is quite noticeable, because the friction of the tires with the ground is not near what the induced drag is with the airplane trying to accelerate in the air.” 

Greg Shelton

“I watched a guy in a low performance biplane making climbing turns after his maneuvers that carried him over to the 1,000 foot line. Then, when he dived back in he would be off-center, so he would have to roll into a turn as he was diving and put G on it, which cost him energy. In a T-6, that will cost you 10 to 15 mph.

“So, if you come down the centerline, paralleling the crowd, you always want to turn out first, away from the crowd, pull the nose up, reverse and, when you are at the apex of your turnaround, you are back on the 500 foot line. So now when you unload and dive in, you are not putting any G on it to make a turn. You are not putting any induced drag on it. Then, the steeper you make it, the less drag you put on it, the faster it is going to go, not only because of gravity, but also because you are unloading the wing more.”

Bill Stein

“What I try and do is to tell people about every mistake that I’ve made that is relevant. I try and tell them about all the mistakes that everybody else I know has made, that are relevant. And this one is about really understanding increasing and decreasing induced drag.

“This mistake was at Salinas. I tell people I love the ACE program because, when I was at 500 foot I made a 250 foot mistake and, when I was at 250 foot I made a 150 foot mistake. I totally botched the thing. I was at Salinas and it was actually a humid day, which is unusual, and it was hot. But I’m at sea level and I’m in my crappy old Pitts and smoke is everywhere and, pretty much, I botched a maneuver. And I am in this kind of deep stall. I’m just in this buffet and I’m thinking, ‘What the heck!’ And I sit there in this buffet sinking at whatever rate a Pitts sinks, for 150 feet before I think, ‘Oh!’ And kind of get myself together and push the stick forward and let the airplane fly, then go.

“So that was at an air show that I did that.  And I was totally head-up-my-ass surprised that this happened, because there have been very few times in my aerobatic career that I’ve been surprised that something happened. I was totally out of energy.

“I tell that story to people and that is my very visceral understanding of the induced drag control lever which is the elevator.”

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Deb Gary
Deb Gary is a former air show performer, member of the ICAS Foundation Air Show Hall of Fame and freelance writer whose work has been published in Air Shows Magazine and Smithsonian Air & Space Magazine.