Originally Posted by
jonkster
not trying to make stuff up, apologies if I misunderstand what you are saying but I am not getting what you are saying.
Your argument (as I read it) is that in a constant wind, an aircraft in a constant rate turn, will have (small) changes of airspeed as it moves from a headwind (relative to the ground) to a tailwind (relative to the ground). Is that correct?
Correct
Would you agree in this situation that the only forces that are directed laterally on the aircraft are thrust and drag and inclined lift, all are acting due to interaction with the air?
Correct. Except that the aircraft is accelerating tangentially in the direction of its ground speed. That acceleration can be accounted-for by a component of the centripetal force (horizontal component of inclined lift)
The angle of bank doesn't change so the lateral component of lift is constant.
We do not change thrust.
The aircraft can only generate an acceleration (which would be required to change the airspeed that you say happens) is if we change drag - that is the only force we have left (as far as I can see).
There is a rate of change of airspeed caused by the rate of change of the headwind/tailwind component as the aircraft turns. This is approximately equal and opposite to the rate of change of airspeed caused by the acceleration of groundspeed. Hence the rate of change of airspeed is approximately zero but NOT EXACTLY zero
Why does drag change?
It does not change apart from the effect of increased load-factor
The only way I can see that changing is because airspeed changes but that is assuming the effect we are trying to find the cause of - it would appear to me to be the airspeed changes because the drag changes and the drag changes because the airspeed changes therefore the airspeed changes... ?? ie we are assuming the effect we are trying to prove occurs.
I am not getting where an unbalanced force can come from that causes the (small) airspeed changes you claim are occur.
It is just that the effect of the changing head/tail wind components is slightly greater than the effect of the force components. The airspeed increases slightly in the windward turn and decreases slightly in the leeward turn
Now if the wind velocity varied (eg a gust or windshear in descent/climb etc) then that would cause a change in airspeed but not in a constant wind. What am I missing here?