Bob Hoover Barrel Roll
Why Aviation Stack Exchange recommends it
Aviation Stack Exchange answerers point people to it as a vivid demonstration that a 1G roll keeps the apparent gravity pointed at the floor, so liquids, hanging objects and passengers behave as in level flight.
Recommended by 0 people across 0 different months, 2016 to 2023.
What it is
A 46-second clip of air show pilot Bob Hoover flying a 1G barrel roll while pouring a glass of iced tea. The tea never spills, even as the plane goes inverted, and the description says there is no video trickery.
Cited in 1 Wikipedia article, including Bob Hoover.
What people said
Cites Dan Pichelman · 2016-01 · Aviation Stack Exchange · on “Can we replace an attitude indicator with a ball half full of liquid?”
Nope. In a perfectly flown turn, the ball of liquid would appear to indicate level flight. You might argue that it could replace the "ball" of a turn & bank indicator, but that's about it. It would also be tough to read in turbulence. See also this YouTube video showing Bob Hoover pouring iced tea [this video] while flying the plane through a roll, even while inverted. Your liquid would behave similarly. [LINK]
Cites voretaq7 · 2016-07 · Aviation Stack Exchange · on “Can airliners fly inverted?”
As others have mentioned this is a classic frame of reference [LINK] problem in physics, perhaps second only to the Einstein on a skateboard joke (Professor Einstein enters the classroom on a skateboard and asks who is moving - the students declare that he is, and he responds that from his perspective he's standing still and they're all moving around him before launching into a discussion of special relativity.) See also: Bob Hoover pouring iced tea upside down during a roll. [this video]
Cites David Richerby · 2017-05 · Aviation Stack Exchange · on “Wouldn't a Snow Globe prevent pilots from getting disoriented?”
This doesn't work. A plane can be in arbitrary orientations while the the forces felt by everybody in the plane are directed straight at the floor. A famous example is Bob Hoover pouring tea while rolling a plane [this video] . If Bob Hoover's tea can't tell that it's being poured upwards, nor can your snowglobe. Indeed, this is precisely why pilots become disoriented.
Cites andy-m · 2017-08 · Aviation Stack Exchange · on “Can one fly up side down while a glass of water keeps full due to g-forces?”
Not only can you keep a glass of water full, you can pour one (or tea) while rolling the aircraft yourself if you're Bob Hoover! [this video]
Cites Dave · 2019-03 · Aviation Stack Exchange · on “What happens to unstrapped passengers if the airliner were to fly inverted”
That depends on how the pilot inverted the aircraft. If they pulled a Tex Johnson [LINK] and executed a smooth barrel roll everyone would remain in their seats as it is a 1G maneuver. Even the flight attendants pouring drinks wouldn't spill [this video] . If the Pilot executed an aileron roll the situation would be quite a bit different... [LINK]
Cites Kenn Sebesta · 2021-06 · Aviation Stack Exchange · on “Which aerobatic maneuvers are most likely to make people airsick?”
I'm interested in classifying aerobatic maneuvers by their propensity to cause airsickness. While there will be some variation across a population, I think we can use first principle arguments to show that low-gee loops are much less nausea-, dizziness-, and vertigo-inducing than snap rolls. Likewise, a single 1G barrel roll [this video] is much less disorienting than extended inverted flight. I'm hoping that in a similar vein to how we have documented human physiology during high-acceleration events, there will also be some literature on physiology in aerobatic environments. (For the purposes of this question, I'd like to put anecdotal experiences aside, or at least limit them to the comment sec
Cites HiddenWindshield · 2022-05 · Aviation Stack Exchange · on “Can fuzzy dice help in IMC?”
No. The simple fact is, any kind of hanging indicator would be subject to the same G forces that confuse a human's inner ear. Here's a famous video of pilot Bob Hoover pouring tea while doing a barrel roll [this video] . If you look carefully, there's also some kind of ball hanging from a string that's tied to the platform holding the cup of tea. The ball continues to point toward the belly of the plane, even when the belly of the plane is pointed toward the sky.
Cites Wayne Conrad · 2023-09 · Aviation Stack Exchange · on “Flying upside down without feeling it”
Your friend may be interested in this video featuring the amazing Bob Hoover doing a barrel roll while pouring water into a glass: [this video]