The Angle of Attack Vs. Pitch – Are They the Same Thing?
It is important to note that, while they can be related, aircraft pitch attitude
is not the same as the angle of attack. The angle of attack is a relationship
between the chord line and the oncoming airflow. Pitch attitude is the
relationship between the aircraft nose and the horizon.
It might seem like we are dealing with semantics, but you must understand this
concept.
Here’s why.
Let’s say you dive the aircraft down at a 45° angle towards the ground (from a
safe altitude) before hauling back sharply on the control column.
Your pitch attitude is -45° during the early stages of the maneuver.
A low-pitch attitude means a low angle of attack, far away from our critical angle,
right?
Nope!
Once the aircraft is stabilized in its dive, your pitch attitude is true -45°. However,
that is regarding the earth’s horizon. The angle of attack, formed between the
wing chord line and oncoming airflow, will be much closer to somewhere around
3°. To make life easy, let’s say the critical angle of attack (where the wing will
stall) is 15°.
When you haul back on the control column, even though your pitch
attitude is well below 15°, your angle of attack isn’t… meaning it won’t take much
to exceed the critical angle. Many pilots have stalled in a dive.
In fact, you should remember this simple rule: –
An airplane can stall at any altitude or airspeed if the critical angle of attack is
reached.
Inverted, in a climb, a dive, wings level… It doesn’t matter. If the angle of attack
exceeds a given value, you will stall the aircraft.
It is also possible to stall at high speed. Stalls tend to happen at slower speeds
because the aircraft’s angle of attack is already high to ensure enough lift is
produced to keep the aircraft flying. This leads to a high-nose attitude, which is
why many incorrectly assume that high pitch and high angle of attack are always
the same.