- 5. Estimate time to passing station
- As you fly by an NDB, start when the
ADF needle is exactly off one of your wings (90° or 270° relative bearing on a fixed compass card), time how long it takes the needle to move 10°, then multiply the by 6 to get the approximate time to fly directly to the NDB—for example, if it takes 7 minutes for the needle to move 10°, it would take you more-or-less 7×6=42 minutes to turn and fly straight to the beacon (see the 1-in-60 rule), modulo winds and other approximations. For bonus points, pretend that it’s the 1930s, and you have a DC-3 full of passengers, in the clouds, with no other way to determine your position.
- 4. Tune in distant transmitters
- ADF signals are AM (long wave), so they hug the ground rather than flying straight off at line-of-sight like a VOR signal. That means that if an NDB transmitter (or commercial AM radio tower) has enough watts, you’ll be able to receive it from surprisingly far away. There is still an enthusiasts’ group for spotting NDBs (I first wrote about it in 2004).
- 3. Listen to the news (or the game)
- While commercial AM stations are rarer than they used to be, there are still lots of them, and unlike satellite radio, they don’t require a subscription. Tune in a few: in Canada, the last time I checked, the frequencies were still listed in the Canada Flight Supplement for emergency navigation use.
- 2. Watch for storms
- Don’t throw out your radar, satellite weather link, and/or lightning detector, but an ADF needle will tend to flicker back and forth towards distant lighting, so it’s at least one extra confirmation that there’s bad weather nearby (the needle may also flicker as you pass from water to land, but I’ve never experienced that personally).
- 1. Navigate, and fly holds and approaches
- The ADF isn’t a precision navigation tool, but it still is a useful backup for when GPS is down or jammed. Victor airways, based on line-of-sight VORs, often have high minimum altitudes, which can put you in clouds and icing; because NDB signals hug the ground, NDB airways (where they still exist) or NDB-to-NDB navigation let you stay much lower. Besides, in an emergency, it’s nice to have a needle (besides the GPS) that just says “the airport is this-a-way.” While I suspect I’m alone in this, I like NDB holds and approaches because of their simplicity — once I’ve tuned in the frequency, there are literally no other knobs to touch until I land.
Are there any other ADF/NDB fans still out there?