Updated October 2026
The angle of incidence is the fixed angle between a wing's chord line and the airplane's longitudinal axis. The designer sets it and the factory bolts it in. The angle of attack is the angle between the chord line and the relative wind, and the pilot changes it with the elevator all flight long. The wing stalls at its critical angle of attack, roughly 16 to 20 degrees in most designs.
The two get mixed up because they share a reference line, the chord, and because older British textbooks use the word "incidence" for what American pilots call angle of attack. In an FAA classroom they are different things. One is a piece of geometry you cannot touch. The other is the single number that decides whether the wing is flying.
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Angle Of Incidence: Fixed By The Designer
The FAA's Pilot's Handbook of Aeronautical Knowledge (PHAK, FAA-H-8083-25C) defines angle of incidence as the acute angle between the chord line of an airfoil and the longitudinal axis of the aircraft. Picture a straightedge from the wing's leading edge to its trailing edge and a line running nose to tail through the fuselage; the angle between them is the incidence. On most light trainers it is a small positive angle, with the leading edge a little higher than the trailing edge relative to the fuselage.
Why tilt it at all? Because the designer wants the wing at an efficient angle of attack in cruise while the fuselage flies roughly level through the air. A level fuselage presents the least frontal area, so it costs the least drag, and it keeps the cabin comfortable and the view over the nose good. Too little incidence and the whole airplane cruises nose-up to get the wing working. Too much and it cruises nose-down, dragging its tail.
The horizontal tail has its own incidence, chosen with the wing's to set the balance of the airplane. Many airliners can change the tail's angle in flight with a trimmable stabilizer. The pilot of a Piper Warrior or a Cessna 162 changes neither. For you, incidence is a fact about the airplane that you learn once, for the written test, and then fly with.
Angle Of Attack: Changed By The Pilot
Angle of attack, in the PHAK's words, is the acute angle between the chord line and the direction of the relative wind. The relative wind is the airflow the wing meets, and it always blows from the direction opposite the flight path. Change the flight path or the pitch, and the angle of attack changes with it.
That is why angle of attack is not the same as pitch attitude. In a power-off glide the nose can sit almost level while the airplane descends, and the relative wind is coming up from below, so the angle of attack is larger than the attitude suggests. In a climb at VY, 79 knots in our Warriors, the nose is up but the wing is at a moderate angle, because the flight path is pointing up too.
The elevator is the angle-of-attack control. Pull back and the tail goes down, the nose rises, and the wing meets the air at a steeper angle. At a fixed weight in level flight, every airspeed has its own angle of attack: slow down and the angle has to go up to keep making the same lift. The lift equation (lift = coefficient of lift × ½ × air density × velocity² × wing area) explains why, and our aerodynamics hub walks through it term by term.
Relative Wind, Chord Line And Camber: The Reference Lines
Three lines carry most of this subject. The chord line is an imaginary straight line from the leading edge to the trailing edge. Camber is the curvature of the upper and lower surfaces, and on a trainer's wing the upper camber is the more pronounced. The mean camber line runs halfway between the two surfaces. The relative wind is not on the wing at all; it is the direction of the oncoming air.
Draw the airplane's longitudinal axis through the fuselage and the chord line through the wing, and the angle between them is the incidence. Draw the relative wind arriving at the wing, and the angle between it and the chord line is the angle of attack. The chord line is the shared side of both angles, which is exactly why people confuse them.
One more piece: as angle of attack increases, the center of pressure, where the wing's lift effectively acts, moves forward. At low angles it moves aft. It is part of why you retrim after every change of power and airspeed.
| Question | Angle Of Incidence | Angle Of Attack |
|---|---|---|
| Measured between | Chord line and the airplane's longitudinal axis | Chord line and the relative wind |
| Who sets it | The designer, at the factory | The pilot, with the elevator |
| Changes in flight | No (fixed wing, fixed tail on our trainers) | Constantly |
| What it decides | Fuselage attitude in cruise, drag, view over the nose | How much lift the wing makes, and whether it stalls |
| Where you meet it | Written test, aircraft design questions | Every takeoff, turn, stall and landing |
| Instrument that shows it | None | An angle-of-attack indicator, if fitted; otherwise inferred from airspeed and load |
Critical Angle Of Attack And The Stall
Every wing has one angle at which the airflow over the top can no longer follow the curve and separates. That is the critical angle of attack, and the PHAK puts it at approximately 16 to 20 degrees depending on the design. Go past it and the wing stalls. The handbook adds the line every examiner wants to hear: a given airplane always stalls at the same angle of attack regardless of airspeed, weight, load factor or density altitude.
Designers also decide where on the wing the stall starts. Most straight wings are built to stall at the root first, so the outboard sections and the ailerons keep working while the buffet tells you what is happening. They do it by twisting the wing so the root runs at a higher angle of attack than the tip, or by fitting stall strips on the inboard leading edge. Training airplanes are also designed so the nose drops in a stall, which lowers the angle of attack for you, provided the center of gravity is inside its limits. An aft CG is the case the handbook singles out as the hardest to recover from.
The recovery follows from the definition. You cannot fix an angle-of-attack problem with power alone. Lower the nose until the wing is flying again, then level the wings, then add power. Our page on slow flight and stalls lays out the full sequence from the Airplane Flying Handbook and the stalls you will fly on the private checkride.
Why Angle Of Attack Matters More Than Airspeed
The stall speed on the airspeed indicator is true for one weight, one configuration and wings level at 1 G. Change any of those and the speed at which the wing reaches its critical angle changes with it. The angle itself does not.
Bank is the clearest proof. In a level 60-degree turn the load factor is 2.0, the Airplane Flying Handbook notes, and stall speed rises with the square root of load factor, so by about 41 percent. The Warrior's clean stall speed of 50 knots becomes roughly 71 knots in that turn. A pilot who has learned "stall equals 50 knots" can stall a perfectly healthy airplane at 70 by pulling hard, which is an accelerated stall.
Weight works the other way. A lighter airplane needs less lift, so it reaches the critical angle at a lower speed. The same arithmetic sets maneuvering speed, which falls as the airplane gets lighter.
The scene we brief every student on is the turn from base to final. The airplane overshoots the centerline, the pilot is low and slow, and the instinct is to tighten the turn with rudder and back pressure. Every input raises the angle of attack on a wing that is already working hard, and the inside wing, the one going slower, reaches its critical angle first. The fix is a go-around, not a tighter turn. The PHAK makes the same point when it describes angle-of-attack indicators as tools for stall margin awareness: speed alone is not a reliable way to stay away from the stall.
Dihedral, Anhedral And Washout: The Other Wing Angles
Dihedral is the upward angle of the wings from the root to the tip, measured from the airplane's lateral axis. Its job is lateral stability. When a gust drops one wing, the airplane starts to slip toward the low side, and the low wing meets the relative wind at a slightly higher angle of attack than the high one. It makes a little more lift and rises back toward level. Stand behind a Piper Warrior on the ramp and the upward angle of its low wing is easy to see.
Anhedral is the opposite, a downward angle. It shows up on some high-wing and swept-wing designs that would otherwise be too stable in roll. Sweep counts as dihedral in disguise: the PHAK's rule of thumb is that about 10 degrees of sweepback gives the effect of roughly 1 degree of dihedral. High-wing airplanes also get a pendulum-like steadiness the handbook calls keel effect, which is part of why a high wing like the Cessna 162's needs less visible dihedral than a low wing.
Washout is the twist built into a wing so the tip runs at a lower angle of incidence than the root. It is the design detail behind the root-first stall described above. At the root the angle of attack is higher, so the root stalls first while the tips, and the ailerons on them, keep flying. Washout is the one place where the two angles on this page meet: a change in incidence along the span, built in so the angle of attack does the right thing near the stall.
What You Feel In The Warrior And The DA20
Both are low-wing trainers. They announce the critical angle differently.
Our Warriors, N3034Q and N6312C, have the semi-tapered Piper wing: constant chord inboard, tapered outboard. Over the Simi Valley practice area the stall comes with plenty of warning. The buffet arrives, the nose goes soft, the stall horn sounds well before the break, and with the ball centered the break is gentle and straight ahead. It is a forgiving place to learn what a high angle of attack feels like in your hands. More detail is on our Piper Warrior PA-28-161 page.
The Diamond DA20-C1s, N306EF and N308EF, have a long, high-aspect-ratio wing that comes from Diamond's motorglider designs, and a control stick instead of a yoke. The stall is benign with clear buffet. What the DA20 teaches better than anything else on our ramp is speed control on final: arrive a few knots fast and that efficient wing keeps flying down the runway in ground effect. It is certificated in the utility category, so it is the airplane for our CFI spin endorsement. That course is $2,000 for 3 hours in the airplane, 2 in the full-motion simulator and classroom work. A spin is a stall in which one wing is stalled more deeply than the other, so the whole course is an extended lesson in this page. The airplane's own page, Diamond DA20-C1, has the specifications.
You can feel both before you choose. A two-hour beginner lesson in the Warrior or the Cessna 162 is $349, and in the DA20 it is $549. Inside a course package the Warrior is $179 an hour and the DA20 $229.
Checkride And Written Questions
14 CFR 61.105(b)(10) and (11) put aerodynamics and stall awareness on the private pilot's required knowledge list. The Private Pilot ACS (FAA-S-ACS-6C) tests aerodynamics under Performance and Limitations (PA.I.F.K3). In our experience the oral questions arrive like this:
- "What is angle of attack, and what controls it?" The angle between the chord line and the relative wind; the elevator.
- "Can the pilot change the angle of incidence?" No. It is fixed when the airplane is built.
- "Can you stall at 100 knots?" Yes. The wing stalls at its critical angle of attack, at any airspeed.
- "Why does stall speed go up in a turn?" The load factor goes up, the wing needs a higher angle of attack for the same speed, and it reaches the critical angle sooner.
- "What does dihedral do?" It gives lateral stability by making the lower wing meet the air at a slightly higher angle in a slip.
Answer with the definition first and an example from the airplane second, and most examiners move on. The private pilot course in Los Angeles covers this in ground school before your first stall lesson, so the flying confirms what you already know.
Related Reading
- Slow flight and stalls, the maneuvers where the critical angle of attack stops being theory.
- Piper Warrior PA-28-161, specifications and V-speeds for the airplane most of our private pilots fly.
- Diamond DA20-C1, the long-winged trainer and spin airplane.
- CFI spin endorsement, spin training in the DA20 under 14 CFR 61.183(i).
- Maneuvering speed explained, the structural speed built on stall speed.
- Aerodynamics for student pilots, the hub for every aerodynamics page.
Angle Of Incidence And Angle Of Attack FAQ
What Is The Angle Of Incidence On An Airplane?
It is the fixed angle between the wing's chord line and the airplane's longitudinal axis, set when the airplane is built. The pilot cannot change it in flight. Some older British textbooks use the word incidence to mean angle of attack, which is the source of a lot of confusion.
Is Angle Of Incidence The Same As Angle Of Attack?
No. Angle of incidence is measured against the fuselage and never changes. Angle of attack is measured against the relative wind and changes every time the pilot moves the elevator or the flight path changes.
What Is The Critical Angle Of Attack?
It is the angle of attack at which the wing stalls. The FAA's Pilot's Handbook of Aeronautical Knowledge puts it at roughly 16 to 20 degrees for most designs, and for a given airplane it stays the same at any weight, airspeed or density altitude.
Can You Stall An Airplane At Any Airspeed?
Yes. A stall happens at the critical angle of attack, not at a speed. In a level 60-degree turn the load factor is 2.0 and stall speed rises about 41 percent. A Warrior that stalls at 50 knots wings-level stalls at about 71 knots in that turn.
Does Pitch Attitude Tell You The Angle Of Attack?
Not on its own. Angle of attack is measured from the relative wind, which comes from the direction opposite the flight path. In a glide the nose can be nearly level while the angle of attack is high, and in a climb the nose can be high while the angle of attack is moderate.
What Is Dihedral On A Wing?
Dihedral is the upward angle of the wings from root to tip. In a slip the lower wing meets the air at a slightly higher angle of attack, makes more lift and rises, which gives the airplane lateral stability. About 10 degrees of sweepback has roughly the effect of 1 degree of dihedral.
Find The Critical Angle With An Instructor Beside You
Reading about angle of attack is one thing; feeling the buffet build and the nose go soft is what makes it stick. Start with a discovery flight, 60 minutes in a Piper Warrior from Van Nuys for $229, with you in the left seat. Already set on training? Book a free consultation and we will show you where aerodynamics, stalls and the checkride sit in a private pilot plan, from the $10,400 Standard package with $2,500 down.
Book A Discovery Flight — $229 Book A Free Consultation Call (818) 330-1318
