REF NAV DATA — Navaid Lookup

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📍 Route: EGLL approach briefing⏱ ~3 minutes📊 5 steps🎓 Foundations

Before an approach, real crews verify the navaids they are about to use. REF NAV DATA is where you look them up.

What this scenario covers

REF NAV DATA returns the database record for a navaid, waypoint, airport or runway: identifier, frequency, position and class. It is a lookup page — nothing you do here changes the flight plan.

The scenario looks up two VORs you would expect on a Heathrow ILS 09L approach: one for the initial fix and one for the intermediate. Confirming their frequencies against the plate is a normal part of the briefing.

How it applies in flight ops

The check exists because the navigation database and the chart in your hand can disagree — a database out of cycle, a navaid decommissioned, or a frequency change published between updates. The chart is the authority.

It is also a fast way to sanity-check a suspicious waypoint. If the FMC has taken a name you did not expect, looking it up tells you whether it is the fix you meant or a same-named one on the other side of the world.

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Everything about this scenario is on this page, steps included — reading it costs nothing and always will. What Premium adds is doing it: the CDU validates every entry as you make it, tells you when an entry was accepted but wrong, and saves your progress across devices.

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Step-by-step: REF NAV DATA — Navaid Lookup

  1. Open the REF NAV DATA page. From IDENT, press INIT REF then LSK 1R for NAV DATA.

    REF NAV DATA is information-only. Unlike the Airbus MCDU RAD NAV page, the Boeing CDU does NOT tune the VHF NAV radios — that happens on the cockpit pedestal panel above the throttles. The CDU's job is letting the crew verify frequencies and positions before they need them in the cockpit.

  2. Look up DVR (Dover VOR). Type DVR and press 1L.

    DVR (Dover) is the primary VOR on the south coast of England — the gateway for traffic arriving Heathrow from Europe. Frequency 114.95 MHz. A 737 inbound EGLL from the south crosses DVR before joining the OCK or BIG arrival sequence.

  3. Now look up BIG (Biggin VOR). Type BIG and press 1L.

    BIG (Biggin) is a TMA VOR south-east of London Heathrow at 115.10 MHz, often used for the ILS 09L final intermediate. Verifying its frequency on REF NAV DATA gives you a sanity check before pulling out the approach plate — if the database disagrees with the plate, something is wrong (stale AIRAC, plate misprint, etc.).

  4. Look up a navaid that is not in the database to see how the page reacts. Type ZZZZ and press 1L.

    The CDU's navaid database only contains navaids in the current AIRAC cycle's coverage area. Idents not present return NOT IN DATABASE — useful confirmation that you typed the right code, or that an obscure navaid is too far from your current FMC region of operation. Always cross-check the AIRAC cycle on IDENT if a known navaid is missing.

  5. Look up DVR one more time to end on a known good value. Type DVR and press 1L.

What to take away

  • REF NAV DATA is read-only — a database lookup, not an entry page.
  • Verify approach navaid frequencies against the chart, every time.
  • The chart wins when the database disagrees.
  • Same-named waypoints exist; the lookup is how you catch one.

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Background reading

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