Three Critical Angles


PITCH ANGLE VS ANGLE OF ATTACK VS FLIGHT PATH ANGLE

Whether we are professional pilots or weekend warriors heading off for $100 hamburgers on Saturday morning excursions, it is very easy to fall out of touch with fundamental aerodynamic concepts. We know they are there and most pilots are generally familiar with their names. However, when a layman or (even worse) our instructor, asks us to provide an explanation of various aerodynamic concepts we begin to realize they have often become fuzzy or hidden in a dark corner of our mind.

In this discussion, let’s briefly look at few “Critical Angles” we really should clearly understand as pilots. For some, this will be a confirmation exercise; for others, it may be the first time these three critical angles have been brought together as a combined discussion. In either case, remaining clear on aerodynamic basics is a core component to ensuring safety of flight each and every day. With the understanding this short snippet of information below is meant to be a discussion generator, let’s proceed as follows:

  1. Review the brief definitions of each critical angle,
  2. Watch the included flash animation dealing with these concepts in a practical “slow down” situation, and finally
  3. Consider posing questions, or simply posting feedback, in the Airplane Upset Recovery Training forum under the following topic:
    http://www.upsetrecovery.com/forum/viewtopic.php?f=5&t=26

DEFINTIONS:

Three important angle definitions are crucial to fully comprehending the relationship between Angle of Attack (AOA), Pitch and the aircraft’s Flight Path. Please review the definitions below followed by a viewing of the included flash animation.

Angle of Attack:

  • Is the difference between the pitch attitude and the flight path angle.
  • Determines whether the aerodynamic surfaces on the airplane are stalled or not.

Flight Path Angle:

  • Is the angle between the flight path vector and the horizon.
  • Is also the climb or descent angle.

On the newest generation jet transports, flight path angle can be displayed on the primary flight display (PFD) as shown in animation below. Flight path angle can also be inferred from the vertical speed indicator (VSI), or from the observed rate of change of the altimeter, in relation to a known ground speed.

Pitch Attitude or Pitch Angle:

  • Is the angle between the longitudinal axis of the airplane and the horizon.
  • Is displayed on the attitude indicator or artificial horizon.

Dumping the “Techno Jargon”…

Here’s how you explain these concepts to your great grandmother who would rather drive from NY to LA than fly a lap around the traffic pattern with you. You’ll need to be patient. However, with a little help from your favorite airplane model in-hand, she’ll get it. If you want to learn something and maximize your ability to retain the information, teach it. Great Grandma is an excellent start.

Pitch:
Is where the wing/nose is pointing.

Pitch Angle or Pitch Attitude:
Is the angle between Pitch and the Horizon.

Flight Path:
Is where the wing is going through the air.

Flight Path Angle:
Is the angle between the Flight Path and the Horizon.

Angle of Attack:
Is the angle between Pitch and Flight Path.

FLASH: INTEGRATION OF PITCH, AOA AND FLIGHT PATH ANGLES
This animation depicts these three critical angles in a developing stalled flight scenario during a thrust-deficient “slow down”. Please turn up the volume and click the image in the lower right portion of the box below to launch the animation.

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