FAA Instrument Rating Airplane (IRA)Flight Instruments and SystemsHard
During the takeoff roll, a pilot glances at the attitude indicator just before rotation and notices it already displays a slight nose-up pitch attitude, even though the airplane is still on the runway. What is the most likely explanation for this indication?
- AForward acceleration causes a gyroscopic erection/precession error that produces a false nose-up (climb) indication
- BA blocked static port is causing an erroneous pitch trend on the display
- CThe gyro has completely failed and requires immediate maintenance
- DThe nose wheel strut has actually extended, causing a real pitch-up attitude
Show answer & explanationAnswer & explanation
Correct answer: A. Forward acceleration causes a gyroscopic erection/precession error that produces a false nose-up (climb) indication
Rapid forward acceleration, such as during takeoff roll, causes the attitude indicator's erecting mechanism to misinterpret the acceleration as a gravity vector shift, resulting in a temporary false nose-up pitch indication that disappears once acceleration stabilizes.
Why the other options are wrong
- B. The attitude indicator is a gyroscopic instrument and is not affected by static port blockage.
- C. A momentary acceleration-induced error does not indicate gyro failure; it self-corrects once acceleration stops.
- D. The actual pitch attitude of the airplane on the ground does not change from strut extension in this manner during takeoff roll.
Attitude Indicator Acceleration Error
Rapid linear acceleration (e.g., during takeoff roll) can cause the attitude indicator's erection mechanism to misread the resultant force as gravity, producing a temporary false pitch-up indication.
- Error is most pronounced during rapid acceleration/deceleration
- Self-corrects once acceleration stabilizes
- Similar principle to compass acceleration errors but affects the gyro's erecting system
Memory trick: Speeding up on the runway fools the gyro into thinking it's climbing.