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IFR Flight Instruments

Primary Instruments



Unusual Attitudes

The unusual attitudes that show up in test questions are generally climbing or descending turns. Questions will be accompanied by an instrument panel depiction similar to the one shown below. Your first step should be to reference the attitude indicator. It is the primary pitch instrument when determining attitude.



In practically every case, power should be your first consideration. If the nose is low the danger becomes excessive speed and subsequent structural damage. If the nose is high a stall becomes the main danger. Because of this remember these two rules:
(a) Nose High - add power (blue: power through)
(b) Nose Low - remove power (brown: power down)

The next issue involves the lift vector. If the nose is low, level the wings. This increases the vertical component of lift all by itself. Then, gently pitch up to level flight. If the nose is high, pitch down (forward elevator) first, then level the wings last.

(a) Nose High - add power, pitch down, level wings

(b) Nose Low - remove power, level wings, pitch up (gently)


Magnetic Compass

The magnetic compass is the most fundamental navigational instrument in existence. It is a required instrument. Because it floats in a fluid, it is prone to certain errors caused by motion of the aircraft. These are called magnetic dip errors because the compass physically dips out of its displayed plane of rotation (relative to the aircraft). This occurs during aircraft turns and changes in airspeed. These are referred to as turning errors and acceleration errors.

During turns to/from northerly headings, the compass will initially show a turn in the opposite direction, then lag behind the turn. Undershoot north - roll out early.

During turns to/from southerly headings, the compass will lead the turn. Undershoot south - roll out late.

Turning errors are most pronounced when turning through northerly or southerly headings.
Acceleration errors are most pronounced when accelerating or decelerating on easterly or westerly headings.
Note that both the Pilot's Handbook of Aeronautical Knowledge and the Instrument Flying Handbook erroneously describe the lead and lag motions of the compass during northerly or southerly turns.

Prior to takeoff pilots should check their compass operation. Confirm that the compass is full of fluid, that it swings freely, and that it agrees with known headings.





Download Instrument Flying Handbook (FAA-H-8083-15B)
Chapters 5-7 - PDF (28.9 mb)