FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesEasy
A pilot is flying an ILS approach to Runway 36. The approach plate indicates that the ILS frequency for Runway 36 is 110.3 MHz, and the associated DME is collocated with the localizer. What frequency should the pilot tune to receive DME information for this approach?
- AThe pilot must consult the A/FD for a separate DME frequency.
- B112.5 MHz, which is a standard VOR frequency for DME.
- C110.3 MHz, as DME is automatically tuned with the ILS frequency.
- D108.0 MHz, if collocated with the localizer.
Show answer & explanationAnswer & explanation
Correct answer: C. 110.3 MHz, as DME is automatically tuned with the ILS frequency.
For an ILS, when DME is collocated with the localizer, the DME interrogator in the aircraft automatically tunes to the correct DME channel when the pilot tunes the ILS frequency. This is a standard feature of modern avionics.
Why the other options are wrong
- A. Consulting the A/FD for a separate DME frequency is unnecessary when DME is collocated and paired with an ILS.
- B. 112.5 MHz is a VOR frequency, and DME associated with VORs requires tuning the VOR frequency, but for ILS, it's automatic.
- D. 108.0 MHz is a localizer frequency, but not the one specified for this approach.
ILS Frequency Pairing (DME)
When DME is collocated with an ILS, tuning the ILS localizer frequency automatically tunes the associated DME.
- DME operates on UHF frequencies but is paired with VHF NAVAIDs.
- Pilot only needs to tune the localizer frequency.
- This simplifies cockpit workload during ILS approaches.
Memory trick: Localizer and DME, a perfect pair, no need to despair!