The aircraft reaches 180 degrees, and is now accelerating at 2Gs downwards. The downward force is not felt by the passengers, again because their entire frame of reference is accelerating at the same speed, only the force pushing them into their seats. The aircraft reaches 90 degrees, and is accelerating to the right at 1G, and downwards at 1G. Since the downward component affects the passengers and plane equally, there is no measurable effect on the G forces with respect to the passenger's frame of reference. The force felt by the passengers is still exactly 1G - the force created by the wings, and it is still pointed vertically through the plane. Since no effort is made to change the amount of force being generated by the wings, the downward component of that thrust (as measured from an external reference point) will lessen, allowing the aircraft to start accelerating downwards while also accelerating to the right. The maneuver is initiated by rolling the plane (clockwise, with respect to the pilot) with the ailerons. It's why instrument training involves so much instruction and reminders to trust the instruments, not your body. Rotational forces are not considered - most people are unable to kinesthetically perceive any rotation which occurs at less than 5 degrees per second, and don't realize that they could be upside down and still feeling like they're right side up. The G's are measured from the frame of reference of the passengers in respect to the aircraft. The pilot takes no action to increase the amount of lift. Given - the force imparted by the wings is 1G (enough to cancel the force of gravity), and will always be pointed straight through the roof of the aircraft. Trying to come up with a better explanation for the first. Not all planes can do it because the engine needs to be very powerful to support horizontal flight, and the wings need a neutral airfoil shape to provide lift when upside down. The second is an aileron roll done purely with the ailerons, engine and tail, not using the lift generated by the wings. And my frame of reference for g-forces are the people on board the aircraft. So my statements are for that interpretation of the word "roll". 2002): (the inside of this airplane: )ĮDIT: (after reading some comments) To me a roll is over when the airplane is back to straight and level, after 360 degrees. Here is an image from my flying some years ago, in a Grob 115C Acro (rented from Attitude Aviation, Livermore, CA, ca. I (in my small and somewhat underpowered aircraft) go below 1G when I get close to the top, because if I tried to maintain 1G the nose of the airplane would have to drop (towards the earth in that position), and I want to keep that at a minimum, so that I don't end the roll with the nose in too much of a nose-down attitude from which I will have to pull out. When you go even slightly negative it becomes a completely different matter, both in terms of real effects (fuel, oil, lose stuff flying around the cabin) as well as psychologically: Even though you made the harness extra tight with as much force as you could muster in preparation for an aerobatic flight with negative G forces, when you get here it feels as if you hang upside down in the harness and the seat is miles away from you, as if you dropped a few centimeters and now literally just hang in the airplane. The real turning point, in real effects as well as psychologically, is when you approach 0G, the feeling only starts at less than 0.5G when you begin to feel more and more weightless. I'm a private pilot who has done aerobatics, exactly 1G doesn't work - and it's completely unnecessary (though you can stay pretty close to it, so that someone with their eyes closed would not know they were rolled).īut just about the video as "proof of 1G":Īs long as you stay positive you are fine, even psychologically with passengers not used to it. That demonstrates that there are no negative G forces.
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