The three motions & four forces of the airplane

[Farhan Najar]

What are the three motions of the airplane and how these axes stabilize the motions?

1. longitudinal axis, controls the roll [banks]
Stability= depending upon three factors:
1- location of the wing with respect to the CG
2- location of the horizontal tail surfaces with respect to the CG
3- area or size of the airfoil


2. lateral axis, controls the pitch [up & down]
Stability= depending upon four factors:
A- dihedral (The angle between the left and right wings)
B- sweepback ( The rearward inclination [slopes backwards] of the wing surface)
C- keel effect (pendulum stability)
D- weight distribution

3. vertical axis, controls the Yaw [left or right]
Stability= when turbulence or rudder application causes the aircraft to yawing to one side, the opposite wing presents a longer leading-edge perpendicular to the relative airflow. The airspeed of the forward wing increases and it acquires more drag than the back wing. The additional drag on the forward wing pulls the wing back, turning the aircraft back into its original path.


What are the four forces acting on the airplane when it is flying?
1. Lift (caused by the air pressure)
2. Gravity (pulling downward because of the weight)
3. Thrust (caused by the action of the propellers or jet engines)
4. Drag (caused by the air friction/resistance)

 

[Clip4]

You need to go back to the drawing board.

 

[dmspilot]

Doesn't make any sense. That's like saying the Earth's axis controls its orbit around the sun.

 

[Clip4]

Longitudinal axis, roll [bank] occurs on this axisi
Stability may be positive, neutral, or negative in flight.
1- In straight level flight, a very small amount of positive stability may occur from dihedral effect.
2. An airplane in a shallow bank should exhibit positive stability
3. An airplane in a medium bank should exhibit neutral stability.
4. An airplane in a steep bank should exhibit negative stability.

 

[Clip4]

Doesn't make any sense. That's like saying the Earth's axis controls its orbit around the sun.

Wait, you mean the sun does orbit the earth? How is this possible? The earth is flat.

 

[flyingron]

This is all well defined (as far as the FAA is concerned) in Chapter 5 of the Pilot's Handbook of Aeronautical Knowledge:

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/07_phak_ch5.pdf

They get the basic forces right and the stability issues. Of course, then they go off the depend with the inane, incorrect "balanced forces" definition of aircraft coordination.