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Comment by cfj | Hacker News Reader

Technically called an aileron roll.

https://en.wikipedia.org/wiki/Aileron_roll

An aileron roll will experience -1G - something you really don't want to do in an airliner. A barrel roll is specifically named because its like driving around the inside of a barrel; the plane always maintains positive Gs.

Correct, a barrel roll requires 90 degree changes-of-course through the manouevre.

Think of the seam-line on a toilet-roll tube; that's the path a barrel roll requires. Lots of pitch and roll, it is not a simple manoeuvre and has to be taught:

https://www.youtube.com/watch?v=hASm6-2QLDU

To my knowledge no airliner has ever been barrel-rolled, it is a high-stress manoeuvre.

Tex himself never claimed it was a barrel roll.

To my knowledge no airliner has ever been barrel-rolled, it is a high-stress manoeuvre.

Tex himself never claimed it was a barrel roll.

I think you've confused them; Tex says, quoted in the article, "The barrel roll is a one G maneuver and quite impressive, but the airplane never knows it’s inverted", while the aileron roll causes negative G at the "top" when the plane is inverted.

Tex is incorrect or misquoted, a 1G barrel roll is next to impossible. More than 1G must generally be pulled at the entry point if you're even going to make the first loop. Even aerobatic champions in Su-26s struggle to do it, and those things have ridiculous power-to-weight.

Furthermore, if you were watching a barrel roll you'd see the aeroplane's nose turn towards you as an observer. That'd didn't occur.

What did Tex call it? The exact words out of his mouth:

"So I came across and did a chandelle"

https://www.youtube.com/watch?v=hASm6-2QLDU

Well, it certainly wasn't that as a chandelle is an FAA-certified check-manouevre involving a climbing turn.

I know it's heresy to question 'national heroes' but frankly Tex didn't know what manouevre he did.

All we know is he hacked something on the day, and it worked.

Are you confusing a roll with a loop???

I fly RC, and pulling back hard on the elevator will rip the wings off a plane, particularly at the bottom of a loop. Alas, I know this from personal experience :-)

Just rolling around the longitudinal axis with the ailerons is pretty low stress, though, at least in a "snap" roll. You loose some altitude, but the load on the wing at the end of the roll is pretty minimal.

Making small elevator changes during the roll to pull back (generate positive G) during the sideways and inverted parts of the roll, and ease off (preventing more G than just gravity/lift of wing) as you return to an upright position is doable with practice. You will loose some altitude, it won't be a "straight" tube/barrel traced.

> Furthermore, if you were watching a barrel roll you'd see the aeroplane's nose turn towards you as an observer. That'd didn't occur.

Not if the entry trajectory is away from you, as is the case in all the videos I have seen - were you thinking of Tex's description of it as a chandelle here?

He uses the unqualified term 'roll' elsewhere in the interview, and the maneuver certainly qualifies, as the craft performed a 360-degree rotation around the longitudinal axis and finished on close to the entry heading. Movement of the camera to follow the aircraft may have concealed its barrel shape, but if you follow the fuselage orientation, you can see changes in heading consistent with a barrel roll, though possibly around an oval or pear-shaped barrel.

Regardless of what you call it, I don't think the maneuver as filmed could be performed at nearly 1G. I wonder if what Hoover was trying to convey was 1) he didn't go negative G, and 2) he didn't pull any more Gs than a chandelle, which, as you say, is a standard check-maneuver (I do not know if the latter is true (with respect to G forces), though the entry into, and exit from, a barrel roll have some resemblances to a chandelle.)

No. The 707 did an actual Barrel Roll, not an Aileron Roll.

No, definitely not a barrel roll. Watch the video and it's clearly obvious that it's not a barrel roll. Also, a barrel roll isn't a 1g maneouver.

The only 1g maneuver that starts and ends with level flight is level flight.

No, a barrel roll is different to an aileron roll. The wikipedia article linked to shows the difference.

A barrel roll requires heading and altitude changes, an aileron roll should not.

Yes, the are different. However what the OP is pointing out is that Tex actually did an aileron roll and not a barrel roll. (Watch the video and it's pretty obvious).

I watched the video and it looks like a barrel roll to me. The airplane doesn't maintain altitude nor heading. Also that engineer who took a photo while kneeling next to a window would have been on the ceiling at that point if it had been an aileron roll.

If you look at 1:56 on the AviationExplorer video you'll see there is little or no pitch change, so it couldn't be a barrel roll. I'm not sure how you can tell that it's heading is changing from that video.

According to wikipedia "An aircraft performing an aileron roll will actually fly along a slightly helical path, and a very light, positive g force will be maintained" so the photographer wouldn't have been on the ceiling.

I don't know which AviationExplorer video you're referring to, but there's supposedly only one video of the maneuver so I assume the one in the article is the same thing.

I see quite a large pitch change there. The aircraft starts more or less level, then pulls up. While inverted it begins to move substantially nose down. As for heading, at the beginning of the video it's pointed well to the left, and at the end of the maneuver the fuselage is lined up with the camera.

Wikipedia is confused or imprecise. Either that "positive g force" refers to the force on the aircraft relative to the Earth, or it's just wrong. Reading through the original reference that statement comes from, I believe it's the former. The book says:

"...we have managed to substantially increase the angle of attack, to a point where the inverted wing is capable of maintaining altitude."

If you're maintaining altitude while inverted, you're not pulling positive gees relative to the airplane, but you are pulling positive gees relative to the Earth.

You can browse most of the chapter on aileron rolls in the book in question on Amazon:

http://www.amazon.com/Basic-Aerobatics-Geza-Szurovy/dp/00706...

https://www.youtube.com/watch?v=AaA7kPfC5Hk

See around 1:56. No significant heading or pitch changes that I can see, although it is difficult to tell because the camera is so far away.

Yeah it's was confusing, an aileron roll wouldn't allow for this https://www.youtube.com/watch?v=pMWxuKcD6vE (posted above). Unless you rotate faster than gravity pulling the water down.

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