FAA Sport Pilot Airplane (SPA)Airspace and NavigationHard
A pilot needs to fly a magnetic heading of 240° and consults the compass correction card, which lists: For MH 210°, steer CH 213°; for MH 230°, steer CH 226°. Using linear interpolation for a magnetic heading of 220°, what compass heading should the pilot fly?
- A207°
- B226°
- C213°
- D220°
Show answer & explanationAnswer & explanation
Correct answer: D. 220°
Interpolating between MH 210° (CH 213°) and MH 230° (CH 226°): the midpoint MH is 220°, halfway between the two listed headings. The corresponding compass heading is halfway between 213° and 226°: (213+226)/2 = 219.5°, which rounds to approximately 220°.
Why the other options are wrong
- A. 207° is not derived from the interpolation between the two given data points.
- B. 226° is the compass heading for MH 230°, not the interpolated value for MH 220°.
- C. 213° is the compass heading for MH 210°, not the interpolated value for MH 220°.
Compass Correction Card Interpolation
When a desired magnetic heading falls between two values listed on a compass correction card, the pilot linearly interpolates between the two nearest compass heading values to determine the compass heading to fly.
- Correction cards list compass headings to fly for select magnetic headings
- Interpolate between listed values for headings not directly shown
- Deviation varies with heading due to aircraft magnetic influences
- Correction card is mounted near the magnetic compass in the cockpit
Memory trick: Between the lines, split the difference