Chart Wise: Training and Technique

Forgotten approach options: NDB/ADF.

Chart Wise
Flying an NDB approach requires considerably more pilot attention because of the navaid’s rudimentary functionality.Flying

In an era of satellite-based precision approaches, a pilot’s understanding of how to find the destination airport using a nondirectional beacon might seem a waste of time. But in the United States, hundreds of NDBs remain in service, according to the FAA. Alaska alone has 70.

Flying an NDB approach requires considerably more pilot attention because of the navaid’s rudimentary functionality. An ADF receiver can perform only a single task: make the ADF needle point right at the station. It offers no distance information, nor any visual warning should the station’s reliability wane. Pilots flying an NDB approach must monitor the audio Morse code ID of a station during the entire approach to ensure a continuous signal.

Because nondirectional beacons operate in the frequency spectrum near the AM broadcast band, NDB signals are subject to fluctuations, including wavering signal strength, especially in the winter. Signals can also waver due to thunderstorm activity near the aircraft.

Despite their limitations, NDB approaches still provide a cost-effective system around which to create an IFR approach, at least until a GPS overlay comes along. In some areas, they’re still often the only approach option.

1. Important notes

This NDB approach contains two must-read restrictions to its use. No one is authorized to attempt the approach at night or when the control tower is closed.

2. You need more than an ADF

The NDB to Hailey requires that any aircraft attempting the approach must also be equipped with a separate DME receiver in addition to the standard ADF receiver unit.

3. Missed-approach-point anomalies

The missed approach is reached at 5 DME, a point that is not measured from the end of the runway. Because the DME is measured from the co-located NDB/DME unit, the missed approach point will be reached as the DME counts up, not down. Note too the possibility of confusion because the distance from the missed approach point to the airport is almost exactly the same as from the beacon to the missed approach point.

4. Final approach fix gotcha

It’s critical on the approach to note that the FAF is not when crossing over the beacon, but rather 1 mile after crossing the beacon, before any descent to the MDA may begin.

5. Final approach lineup

This is considered a circling approach with a significant restriction: no circling northeast of Runway 13/31. There’s also a warning to the pilot that even if every element of the procedure works as expected, the final approach course can be expected to place the aircraft about midfield at Hailey.

6. Minimums check

This approach demands at least 5 miles visibility in order to land, not to mention that even at the MDA the aircraft will still be flying more than 2,700 feet above the surface.