What is the difference between angle of incidence and the angle of attack?

Question

What is the difference between angle of incidence and the angle of attack?

Answer 1

B.Z. Coffee... you finished writing that Pilot manual to replace the FAA's version yet??

Answer 2

The angle of incidence is the angle between some (usually an airfoil's) chord line and the longitudinal axis of the aircraft.  It could be the mean aerodynamic chord line of the wings or tail planes, it could be some specific chord line such as the wing tip or wing root on a wing or tailplane, or the chord line of anything.

On most aircraft the wing's mean aerodynamic chord line is not fixed; it can differ with different flap positions.

The angle of attack is the angle between the local airflow and an airfoil's chord line.

Answer 3

The angle of incidence is a fixed value for an airplane.  It represents the angle between the longitudinal axis and the chord line of the wing.

The angle of attack is the angle between the chord line and the relative wind.  This angle changes in flight and does not correspond directly with the angle of incidence as an airplane's flight path is rarely ever parallel with the longitudinal axis.

Let me know if this makes any sense.  I'll go more in depth if this doesn't answer your question.  Just trying to keep it simple for now.

Answer 4

The angle of incidence is the angle between the aircraft's longitudinal axis and the chord of the wing.

The angle of attack is the angle at which relative wind(flight path )meets wing.

Datum line????

I was taught that the . The datum line is an arbitrary point that the designers use to measure  from for weight and balance . Some might choose the fire wall for instance, might be the elsewhere but is defiantly nothing to do with angle of incidence.

In simple terms It is the angle the wing is mounted to the fuselage relative to the level longitudinal line that goes from  fore to aft of the plane....SHEESH>>>

Answer 5

Pretty decent answers so far, but I'm gonna throw a monkey wrench into the works. Not ALL angle of incidences are permanently fixed and unable to be changed. The exception to the rule is the F-8 Crusader.

That is all.

Answer 6

Most answers good. Most airfoils do produce some lift at a 0 degree AOA. A symmetrical airfoil wont, more commonly seen on aerobatic aircraft.

Answer 7

The angle of incidence is defined in yourdictionary.com as "the angle that a light ray or electromagnetic wave striking a surface makes with a line perpendicular to the reflecting surface."

Here is a link to the definition:

http://www.yourdictionary.com/angle-of-i...

If you would like to see a visual representation of the angle of incidence check out the link below.

http://scienceworld.wolfram.com/physics/...

The angle of attack can defined as "the acute angle between the chord of an airfoil and the line of relative air flow."

The definition can be found at:

http://www.yourdictionary.com/angle-of-a...

Aerospaceweb.org provides the best in depth explanation of the angle of attack. The definition is easy to follow and includes lot of pictures and diagrams. I would highly recommend that you browse through it.

http://www.aerospaceweb.org/question/aer...

I hope this provides clarification between the two types of angles.

Answer 8

Angle of Incidence is the angle between the datum line of the aircraft and the wing chord. This is a fixed angle decided during the design stage of the aircraft.

Angle of attack is the angle between the relative airflow and the wing chord. This varies with the pilot's inputs on the pitch of the aircraft while flying.

Answer 9

The angle of attack is the angle at which the wing meets the oncoming flow of air.  The angle of incidence is the built-in angle that the wing forms with the rest of the fuselage.  The angle of incidence is normally greater than zero, because this allows the aircraft to fly level under certain conditions while still maintaining the positive angle of attack necessary to remain aloft.

Answer 10

Hi!

The angle of incidence is built into the aircraft, and cannot be changed. This angle is the angle that the wing makes with a level surface (such as if the ground if the aircraft were parked).

The angle of attack (commonly abbreviated AoA), is the angle that the chordline of the airfoil makes with the relative wind. So if you were in straight and level flight, maintaining altitude, the angle of attack would be zero degrees.

When an aircraft exceeds a critical angle of attack (which is determined by the design of the airplane), the airflow will peel off of the wing, causing the wing to stop producing lift. The aircraft is, in this scenario, stalled.

Hope this helps.