RAD NAV: DELIBERATE TUNING AND INDEPENDENT CHECKS
RAD NAV means radio navigation. The page shows tuning information for the radio aids used by the aircraft. The flight-management system can tune suitable aids automatically, while a deliberate manual entry can hold a particular selection. We inspect the page to understand what is selected and why. A stored manual choice deserves attention later, because the flight plan may change while that choice remains in place. [26, PDF pp. 469-470,474,477]
An aid can have an identifier, a frequency and an associated course. Each item helps describe the installation or reference being used. The practical exercise asks you to compare the actual selection with the chart, including any entry you have made manually. If an obsolete manual selection is cleared, the system may return to automatic tuning or display brackets where no aid is currently auto-tuned. Read the result instead of assuming it. [26, PDF pp. 469-470,474,477]
For Heathrow's planned ILS, the Instrument Landing System, we check the selected runway and approach against the current chart. The localizer provides lateral guidance towards the runway alignment, while the glideslope provides vertical guidance down the approach. The correct identifier, frequency and course help establish that we are preparing the intended installation. An accepted frequency for a different runway is still a different approach. [26, PDF pp. 469-470,474,477] [53, PDF pp. 2-4]
We do not supply a remembered Heathrow frequency in the teaching dataset. It depends on the actual runway and procedure you will use. Make the selection from current information and repeat the check during arrival preparation, particularly after a runway change. When the aid is receivable, include its identification in the confirmation; a tuning entry and the received signal are related checks rather than the same observation. [26, PDF pp. 469-470,474,477] [53, PDF pp. 2-4]
There are now two useful pictures to compare. The navigation display's route line represents the lateral flight plan. Raw radio indications show the aircraft's relationship to the selected radio aid. Looking at both helps us assess whether the aircraft is where the procedure expects it to be. Neither picture becomes more convincing simply because it is displayed in a familiar colour. [26, PDF pp. 469-470,474,477]
For the first flights, give each entry a clear purpose: identify the intended aid, verify the selection, and understand any manual override. Later, after vectors or a changed approach, return to those same checks. The page becomes much less mysterious when its fields belong to an actual runway, chart and aircraft position. By then, RAD NAV is simply another useful place to look, with a rather brisk abbreviation above the door. [26, PDF pp. 469-470,474,477]
IN PRACTICE: RAD NAV: verify the aid you actually intend to use
Before you begin: Use the chart for the selected runway/approach and the active database. Do not supply a Heathrow ILS frequency or course from memory for this exercise.
1. Read the current tuning state
Action. Press RAD NAV and inspect the displayed radio-navigation selections. Identify entries you have forced manually, as distinct from selections made by the system for the current flight phase.
Check. You know which selections may persist because of your own intervention. Automatic tuning has not been assumed simply because the page contains sensible-looking frequencies. [26, PDF p. 122] [26, PDF pp. 469-470,474,477]
2. Crosscheck the ILS against the chart
Action. For the actual intended ILS, compare the runway designation, localizer identifier, frequency and front course. Review the selected approach in F-PLN as part of the same check.
Check. The chart, approach selection and tuning refer to the same installation and runway end. No example frequency has become a flight input. [26, PDF p. 474] [26, PDF pp. 199-209]
3. Make a manual entry only when intended
Action. If the procedure calls for manual tuning, enter the charted identifier or frequency into the appropriate ILS field and read back the accepted selection. Complete or verify its course field as required.
Check. The requested aid, rather than a similarly named aid, is selected. The course is the intended front-course reference. [26, PDF p. 474]
4. Confirm identification when reception permits
Action. When the aid is receivable, compare the displayed/received identification with the chart and the tuned selection. At the stand, do not invent a successful signal check for an aid that is not being received.
Check. Database/tuning agreement and actual signal identification have been distinguished. Both will be reviewed before relying on the approach guidance. [26, PDF p. 474] [13, PDF pp. 159-162]
5. Revisit a manual override after a change
Action. After a runway or approach revision, inspect RAD NAV again. To cancel an obsolete manual frequency/identifier, place CLR in the scratchpad and select that field. Then inspect the resulting automatic selection, or brackets if no aid is auto-tuned.
Check. The obsolete override has been removed. Verify the resulting tuning against the revised approach before relying on its guidance. [26, PDF pp. 469-470,474,477]
Complete when: The selected aid and course agree with the intended procedure. Any manual tuning is deliberate, and it will be revisited after a runway or approach change.