Flying Upside down

How can stunt planes fly upside down?

Regarding Cecil’s closing remark about falling out of a plane, isn’t it true that one continues to be pressed down into one’s seat even while flying inverted? I seem to recall seeing a stunt pilot on tv pouring a glass of water while performing a barrel roll.

No, stunt pilots have seatbelts. That’s what keeps them in their seats while inverted.

That might certainly be possible during a maneuver like a loop where there can be a centrifugal effect.

But the article seems to be addressing straight and level (but upside down) flight. Cruising along in a level path, the pilot would be inclined to fall out just as if the aircraft were suspended upside down in a museum. There’s no aerodynamic force or acceleration that will keep him held up. He needs a restraint.

On a slightly different note, one thing the article doesn’t address is that for some aircraft there’s no real distinction between upside down and right side up. The Extra 300 is a great example. That purpose-built stunt plane has a mid-set wing with a symmetrical airfoil. In other words, it’s the same wing upside down. That aircraft, in general, will perform just about identically upside down, except for the fact that the controls are all backwards.

As a matter of fact, most conventional wings are capable of providing sufficient lift even when upside down. Sure, the more highly-cambered the airfoil is, the more inefficient it will be when made to go upside down. And if you keep dialing up the camber, you’ll finally get to a point where there’s no way to generate sufficient lift upside down. But from an aerodynamic standpoint, there’s nothing terribly weird or difficult about upside-down wings.

Cambered airfoils are designed to increase effectiveness and efficiency when generating normal, right-side-up lift. This is done at the expense of being able to fly well upside down. This is usually fine, because there’s no real need to get your Cessna 182 inverted. But stunt planes are certainly not going to use wings that are so good in the up direction that they don’t work in the down.

It depends on how he does the barrel role. If it is a simple quick role about the main axis of the plane then he will feel upside down for part of it and not be able to pour the water unless he does some funky contortions while doing it. If, however, it is more of a corckscrew role it is possible to keep all positive gs, though while upside down it will likely be less than 1 g. I this case he could pour the water in a standard orientation, but one would hope he was too busy flying the plane.

Agreed. In fact I think this article explains things pretty well, whereas the “flying upside down” one is a little more open to interpretation.

Fighter jets, of many various wing shapes and profiles, are able to fly upside down for indefinite periods of time, without altering the AoA. I suppose though, they are able to use an excess of thrust to keep things ticking along.

This is another excellent resource. If I had to explain the concept at a primary school (or pub!) level, I would start with the Newtonian aspect i.e. air being deflected in one direction provides lift in the other.

Yes it does. The author of that Staff Report, I hear, is a frickin’ genius.

IIR my aerobatics manual correctly (want to fly someday) a barrel roll is defined as a corkscrew roll as compared to a roll around the axis, the barrel represents the outer edge of the flight path. If that makes any sense.

Want to fly someday and you are already studying up on aerobatics? Ambitious. I didn’t know the correct terminaology so I assume you are right. What do they call a role around the axis your are flying?

Actually they do alter their AoA, it’s just that they only need a small change when they are flying at high speed, so you don’t see it easily.

I don’t remember that, sorry. I took flying lessons years ago, got close to finishing my private license (about 10 hours from completion) was planning to go commercial. Then my girlfriend and I got pregnant, now I am a happily married man of 16 years, with two kids and no money for flying :slight_smile: I do buy flight sims every now and again and the aerobatics book was purchased to practice proper rolls, loops and so on.

One day when I start to fly again, I intend to stay with a private license and get a small aerobatic plane. If I get rich somehow it will be a Waco Super Classic, if not it will be something cheaper. I figure if you are going to dream, dream big.

A barrel roll is the cork screw type of roll where positive gs can be maintained throughout.

A roll around the aircraft’s longitudinal axis is generally called a slow roll and requires “top” rudder to keep the nose up while passing through 90 degrees bank, it also requires a fair amount of forward elevator passing through the inverted.

Another type of roll is the aileron or stick roll. It involves raising the nose slightly above the horizon and then rolling using aileron only (although some rudder should be used on entry and exit to prevent adverse yaw.) As the aircraft rolls you allow the nose to drop through the horizon (a similar amount to the initial nose up.) Depending on how fast you roll and how much you let the nose drop, the gs while inverted can be slightly positive.

Barrel Roll, Slow Roll, Stick Roll. Got it, thanks.

To mangle an old saying, there’s more than one way to turn a cat upside. Those names for rolls are what I was taught, and how I was taught to do them. But aerobatic manoeuvres collect a variety of names and there are numerous techniques for performing them. Don’t be surprised if other people have different ideas about what an aileron or slow roll are.