Full scale deflection on the CDI during an ILS approach corresponds to how many degrees off?

Full scale deflection on the CDI during an ILS approach corresponds to how many degrees off?

• A. 5
• B. 2.5
• C. 10
• D. 0.5

Answer: (B)

Full-scale deflection on the CDI means you’re at the maximum lateral deviation the instrument will display. For the localizer part of an ILS, that maximum is 2.5 degrees off the course. So when the CDI needle is fully deflected to one side, you’re 2.5° away from the localizer centerline. To reestablish the approach path, steer back toward the localizer course until the CDI centers. The other numbers aren’t used for the localizer’s full-scale indication, since ±2.5° is the standard maximum display.

Full-scale deflection on the CDI means you’re at the maximum lateral deviation the instrument will display. For the localizer part of an ILS, that maximum is 2.5 degrees off the course. So when the CDI needle is fully deflected to one side, you’re 2.5° away from the localizer centerline. To reestablish the approach path, steer back toward the localizer course until the CDI centers. The other numbers aren’t used for the localizer’s full-scale indication, since ±2.5° is the standard maximum display.