[falcolas]

> everything else requires a deviation from that to change direction

Well, kinda. The trick is that you have 1G downwards constantly, which can be reduced by initiating a descent at the same time you introduce other directional changes. Rotation (the major component of a barrel roll) does not impart G forces, as recognized by the term.

I'm sure few to zero pilots who can keep it at 1G exactly throughout the maneuver, but it is at least theoretically possible (so long as you don't mind losing altitude via the maneuver).

[pedrocr]

>Well, kinda. The trick is that you have 1G downwards constantly, which can be reduced by initiating a descent at the same time you introduce other directional changes.

This isn't possible. In straight and level flight you are experiencing 1G acceleration. To be able to change the plane's orientation in any way you need to impart some acceleration to it and thus deviate from the 1G. For example initiating a descent requires an acceleration downwards which will be felt by the passengers as less than 1G. If you finesse it enough and do it big and wide enough you can probably maintain it within a tolerance for what we consider to be 1G but it's not possible to stay at 1G exactly.

[wongarsu]

In any realistic scenario it's of course only possible to stay within some threshold around 1G. But why would it be theoretically impossible? If I drop the nose down slightly I reduce downward forces to say 0.95G. In the same manouver I accelerate left with 0.31G. Since 0.95^2 + 0.31^2 = 1^2, I still have a net force of 1G on the aircraft. In theory it should be possible to compute a path that keeps me at exactly 1G at all times.

[mikeash]

You can indeed, in theory, start a descent while maintaining exactly 1 gee. But you can't stop that descent without exceeding 1 gee. The best you can do is to maintain your current vertical velocity.

[pedrocr]

I understand 1G as also requiring the vector to be pointing down on the aircraft. If you allow it to point in any direction as long as the vector has length 1 passengers will notice and not all mechanical parts will be guaranteed to work so the fact that it's technically 1G is not enough to guarantee any airplane can do it. I think that's not the usual definition of 1G either as we even talk about negative Gs (and airframes are particularly sensitive to them) which wouldn't make sense in that case.

But it would be cool to see if there's a theoretical path that we can recognize as a barrel roll than keeps exactly 1G of acceleration in any direction needed.

[Sohcahtoa82]

What he's saying is possible, but it wouldn't be a barrel roll anymore.

You can experience 1G while banked 90 degrees by pulling up slightly. However, the plane will be losing altitude as the wings are not generating lift.

[pedrocr]

Once you are banked 90 degrees you can do that but how do you get to that bank while maintaining 1G pointing towards the floor at all times?

[falcolas]

By smoothly transitioning into the turn as you roll. The simple act of rolling the aircraft doesn't change the amount of lift being generated towards the roof of the aircraft. In fact, if you don't increase that force intentionally, you will turn and lose altitude.