Timeline for How to determine angle of bank caused by shift in centre of gravity in an aircraft?
Current License: CC BY-SA 4.0
11 events
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| Mar 5, 2019 at 2:16 | comment | added | jim | @MichaelHall the Boeing 747-400. I don't think I was very clear about the maximum bank angle question. Sorry. I meant to ask how can you calculate the threshold bank angle for the aircraft rolling back to it's position. | |
| Mar 5, 2019 at 0:47 | comment | added | Michael Hall | @Jim, at some maximum bank angle the aircraft will NOT roll back to upright. This would vary by aircraft. Do you have a specific airplane you are interested in? | |
| Mar 5, 2019 at 0:36 | comment | added | jim | Given this roll stability now would there be a way to calculate the maximum bank angle before the aircraft rolls back to its position? | |
| Mar 4, 2019 at 23:56 | comment | added | Robert DiGiovanni | Actually, Dutch Roll is a wallowing of a massive aircraft due to the inertial momentum of its side to side roll (top heavy) and insufficient directional stability (usually from a damaged vertical stabilizer). Also, let's not confuse a graveyard spiral, exacerbated by back pressure on the yoke, from spiral instability designed in to avoid Dutch Roll tendencies. If one scaled up a Cessna 172 to 747 size, it would be too stable, hence design tradeoffs. The 747 is low wing, but has dihedral for roll stability. | |
| Mar 4, 2019 at 22:13 | comment | added | Michael Hall | ... and if you shift weight from side to side within the fuselage the aircraft will not end up in a graveyard spiral. | |
| Mar 4, 2019 at 22:11 | comment | added | Michael Hall | Ok Jan, I respect that you prefer to keep an air of mystery about you, but it would be helpful if you were to establish your credibility in this matter. My experience matches what I have been taught; that dihedral and other effects produce positive stability in the roll axis. I can demonstrate this by banking to 5-10 degrees, centering the ball, and letting go of the controls. The aircraft will come back to wings level. If we are just splitting engineering hairs over the contribution of yaw then so be it, but I stand by my assertion that most GA aircraft are stable in roll. | |
| Mar 4, 2019 at 22:03 | comment | added | Jan Hudec | @MichaelHall, the dutch roll is the only mechanism that provides any kind of positive stability. Above certain bank angle, the yaw-roll coupling provides a negative stability instead, but that is also yaw-roll coupling. In coordinated flight, roll stability is always neutral. | |
| Mar 4, 2019 at 21:42 | comment | added | Michael Hall | I'm not saying that there isn't some small amount of dutch roll as the aircraft recovers from an upset, but to imply negative stability in roll as the norm is misleading. | |
| Mar 4, 2019 at 21:38 | comment | added | Jan Hudec | @MichaelHall, it is not possible to have stability in pure roll. Aircraft do have roll-yaw and yaw-roll coupling that makes small excitations in roll produce dutch roll instead of runway bank, but it usually only works at low bank angles, because otherwise the dutch roll would be rather uncomfortable. | |
| Mar 4, 2019 at 21:33 | comment | added | Michael Hall | Some aircraft are not stable in roll, but most are. | |
| Mar 4, 2019 at 20:31 | history | answered | Jan Hudec | CC BY-SA 4.0 |