ILS/VOR CDI Deviation RNAV

There are two types of CDICDI —Course Deviation Indicator display: 2 dot and 5 dot. The key to this question is to remember what full scale deflection means for both of these displays.

  • In VORVOR —VHF Omnidirectional Range mode, full scale deflection is 10°.
  • In ILSILS —Instrument Landing System mode, full scale deflection in the localiser is 2.5°. Remember you can only get to half full scale deflection before you must initiate a go around.
  • In ILSILS —Instrument Landing System mode, full scale deflection in the glidepath is 0.7°. Remember you can only get to half full scale deflection before you must initiate a go around.

After considering what the full scale deflection (FSD) value is, divide it by the number of dots on the instrument and that will give you the answer.

So in VORVOR —VHF Omnidirectional Range mode (FSD 10°) with a five dot display, each dot represents 10/5 = 2° per dot.

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Assuming a 2 dot display, what does each dot represent when the CDICDI —Course Deviation Indicator is in ILS mode?
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