ORIGINAL: flythesky
Let's consider this as an object moving thru space at an absolute speed and direction, lets not talk about airspeed yet. In your diagram the plane is moving up at a speed of 20 kts and has a certain amount of energy from it's motion, it is then directed to the left, loses 5kts and a portion of it's energy in the turn, and then proceeds to the left at 15kts with the remaining energy. To say otherwise is to say that it somehow instantly lost the energy that it has. Now we consider air speed. Moving to the left at 15kts it encounters air moving to the right at 20kts. The result is that air is moving over the plane at 35kts.
If we can agree on this we can continue to analyze the rest of the scenario.
ORIGINAL: Lnewqban
Thanks, Larry.
I have modified the schematic; see the attachment.
It seems that your square loop cannot be performed properly with those velocities, because it will look like a bump to you.
Note the values in magenta that I have modified.
I know that it is confusing; I recommend trying the loop in calm conditions to have all the velocities correct, and then add wind velocity to see what happens.
I will be back on this tomorrow.
Larry,
We cannot agree on that.
This morning, I was thinking that one problem with the example is that the speed of the airplane does not match with the speed of the wind in real life.
Any plane being able of fying so slow as 15~20 knots without stalling must have a very low wingload.
I don't know of planes with low wingload that can perform compensated aerobatic maneuvers in winds of 20 knots.
I suggest reducing the wind speed or increasing the minimum speed of the airplane in your example.
So many people cannot be wrong.
It seems that we have been talking different concepts so far.
Could you define airspeed and groundspeed for all of us trying to discuss this?
I agree with these definitions shown in Wikipedia:
http://en.wikipedia.org/wiki/Airspeed:
"Airspeed is the speed of an aircraft relative to the air.
.....
The measurement and indication of airspeed is ordinarily accomplished on board an aircraft by an airspeed indicator ("ASI") connected to a pitot-static system. The pitot-static system comprises one or more pitot probes (or tubes) facing the on-coming air flow to measure pitot pressure (also called stagnation, total or ram pressure) and one or more static ports to measure the static pressure in the air flow. These two pressures are compared by the ASI to give an IAS reading."
Note that a sensor located in the leading edge of the wing is needed to measure the airspeed; hence,
the LE is the point of reference for such measurement.
http://en.wikipedia.org/wiki/Groundspeed
"Ground speed is the speed of an aircraft relative to the ground. Information displayed to passengers through the entertainment system often gives the aircraft groundspeed rather than airspeed.
Ground speed can be determined by the vector sum of the aircraft's true airspeed minus the current wind speed and direction; a headwind subtracts from the ground speed, while a tailwind adds to it. Winds at other angles to the heading will have components of either headwind or tailwind as well as a crosswind component.
An airspeed indicator can only indicate the aircraft's speed relative to the air mass. The air mass as a whole may be moving over the ground due to wind, and therefore some additional means to provide position over the ground is required. This might be through navigation using landmarks, radio aided position location, inertial navigation system, or GPS. When more advanced technology is unavailable, an E6B flight computer is often used to calculate groundspeed.
Ground speed is quite different from airspeed. When an aircraft is airborne the ground speed does not determine when the aircraft will stall, and it doesn't influence the actual aircraft performance such as rate of climb."
Note that a sensor located on the ground is needed to measure the ground speed; hence,
the ground is the point of reference for such measurement.
Again, these concepts are confusing for many pilots; I recommend trying the loop in calm conditions to have all the velocities correct, and then add wind velocity to see what happens.
Even better, let's try the example of the hot air balloon that has been used in other similar threads:
Imagine that you are in the basket of a hot air baloon, while you are flying your RC plane in a normal circular pattern around that balloon.
The wind is making the balloon drift in one direction, but you don't know what is the speed of the wind and the balloon.
However, you are able to keep the circular pattern of your plane around the balloon.
An an observer on the ground will see deformed shape of the loop that you are seeing from the balloon.
If there is a strong wind, both persons cannot see the same shape.
If there is zero wind, an observer on the ground will see the same shape of the loop that you are seeing from the balloon.
Can you explain how that happens?