# Physics of Passengers on an Airplane

• Forty-Two
This is because your inertial frame is no longer aligned with the motion of the aircraft. In summary, the forces you feel in an airplane turn are due to the combined effects of gravity and centripetal force.f

#### Forty-Two

I was recently riding on an airplane and became intrigued by how I could not feel when the airplane was turning.

I then tried to figure out the physics behind this sensation but to no avail. Could anyone provide an explanation from a physics standpoint as to why I am unable to feel when the airplane banks in a turn?

The airplane banks slowly so you can't feel the rotation and the g-force is always down - and not very intense - so you don't feel the turn.

The force that you feel while in an aircraft is caused by acceleration, not gravity. The amount (within a limited range) and direction of force is controlled by the aircraft's thrust and it's control surfaces, which are controlled by the pilot (or autopilot). This video will demonstrate my point.

Last edited by a moderator:
Thank you!

I had never thought of the rotational motion of the airplane and that makes sense.

I thought about it a bit more and guessing there is a relationship between how sharply the plane is banking and how large of a "circle" (cannot think of a better way to say it) the plane goes in (thus the radius), then there must be a relationship between how much the plane banks and what I guess is centripetal force. Is the amount of centripetal force you receive proportioned exactly as to mimic the force of gravity you normally feel?

Hopefully that makes sense, perhaps I am making to difficult a question out of this.

I had never thought of the rotational motion of the airplane and that makes sense.

I thought about it a bit more and guessing there is a relationship between how sharply the plane is banking and how large of a "circle" (cannot think of a better way to say it) the plane goes in (thus the radius), then there must be a relationship between how much the plane banks and what I guess is centripetal force. Is the amount of centripetal force you receive proportioned exactly as to mimic the force of gravity you normally feel?

In a car, when you go around a bend you feel a sideways force. In a aircraft with a good pilot, the bank angle is such that the combined force of gravity (that you always feel) and the reaction to the centripetal force is directed straight down through your seat so you do not feel a sideways force that you normally associate with turning motion, but you do feel slightly heavier. There are sensors in your inner ear that detect sideways motion but hey do not work in this situation and they tell you that you are still vertical. See the animation of how the inner ear sensors work here http://www.bbc.co.uk/science/humanbody/body/factfiles/balance/balance_animation.shtml

The centripetal force does not exactly mimic the force of gravity. In a fighter plane in a very tight turn, the g forces of turning are very noticeable no matter how good a pilot you are.

As some of the other posts have said, the basic reason is that for a proplery "balanced" turn, the resultant of the centripetal acceleration (towards the center of the turn) and gravity (weight) acts "downward" relative to the aircraft. The only effect you feel is a slight increase in the magnitude of the acceleration (i.e. extra weight) but for normal flying in a passenger aircraft this is small. You need to turn with a bank angle of 60 degrees to double your weight (i.e. 2G acceleration). Commercial passenger flights would never reach even 30 or 40 degrees, except in an emergency situation like avoiding a collision with another aircraft.

I have flown a full circle of a 40 degree banked turn in an Airbus A330 (with test pilots on the flight deck, not a commercial flight!) and you can start to feel a bit of G force under those condtions. Looking along the wing and seeing the ground zipping past only 1500 feet below was also an "interesting" experience.

These effects can be dangerous flying a small aircraft manually in poor visibilty, because without a clear visual reference it is easy to become disoriented and misjudge what the plane is reallly doing.

It can be because of large radius of curvature of the turning path.here Centrifugal force is pushing d person sideways not centripital force.since d person is in a non inertial frame he would feel a pseudo force acting radially outward.
Increase in weight is due addition of component of tat force. It depends on the angle of plane of turning with horizontal.
Thank you,

I have certainly, many times, felt an airplane turning. If the turning radius is large enough, of course, you would not feel that.

One thing that's very noticeable and somewhat disconcerting is if you yaw or slide sideways, such as when making a crosswind landing.

As yioup says, the rotation about the vertical axis can sometimes be felt, especially if you at the same time turn your head along an axis that is not vertical, like up/down, and especially at the start and end of the turn. During a constant rate turn the inner ear sense will "dampen out" the feeling of rotation (luring early aviators who flew blind without instruments to enter the deadly spiral of death), leaving only the dizzy feeling when nodding your head.

I can recommend [1] for a nice overview of the surprising array of psychological effects that occurs in aviation, although I gather many of these effects probably would be unnoticed and of minor interests for passengers on a commercial flight.

[1] Principles and Practice of Aviation Psychology, http://books.google.dk/books?id=IQWB8UfvQy0C [Broken]

Last edited by a moderator:
Any change of a moving direction vector WILL affect one's inner ear, thus your body should be aware of it.
Some people are less "sensitive" to such changes, it seems.
Not sure if that's due to inner-ear biological differences in different people or what.
Could be a neuroscience thing as well. With that being how the brain interprets the changing signals.

Wow thanks for all the responses.

I did not know difference between centripetal force and centrifugal force. Thank you for enlightening me.

I believe I understand the physics a little better and will have to look into the physiology of the inner ear a little bit more.

Again thanks for the information.