Plan to shut down Alaska NDB, TWEB opposed

June 9, 2011

Pilots would lose a vital ground-based navaid in a mountainous area with poor GPS reception, as well as transcribed weather broadcasts (TWEB), under an FAA plan to decommission the Summit nondirectional radio beacon (NDB) near Cantwell, Alaska.

Pilots can comment on the proposal, which is the subject of an FAA aeronautical study, until June 25.

TWEB information is critical to flight safety in remote areas such as the region around Cantwell. The information is broadcast over some VOR and NDB frequencies, as depicted by a small "T" in the navaid box on aeronautical charts. The broadcasts often include route-specific surface weather reports and forecasts. Up to five reporting stations' weather observations can be included in a TWEB, as well as winds aloft, sigmets, and airmets. TWEB information also may be obtained by telephone in some locations. The number of TWEBs is shrinking, but they remain a critical source of weather information in remote areas.

Many pilots have told AOPA that they rely on the Summit NDB for en route navigation in the region, which experiences poor GPS signal reception because of the proximity of Mount McKinley, AOPA said in a letter to the FAA. “With no alternate ground-based navigation option and unreliable GPS signal coverage, pilots are placed in grave danger with no navigational facilities available to them. The loss of this navaid combined with a frequently unreliable GPS signal presents an unacceptable risk to pilots in the Cantwell, Alaska area,” wrote AOPA Aviation Technical Specialist Patrick Smith in formal comments submitted June 6.

The nearest alternative ground-based navaids are more than 60 miles away and suffer from constraints on line-of-sight signal reception in the area, adding to the “unacceptable risk” of the decommissioning plan.

In urging the FAA to withdraw the NDB’s decommissioning, AOPA reiterated that general aviation “cannot afford to lose critical, all-weather en route navigation in the National Airspace System.”

Members can comment on the proposal until June 25. Please forward a copy of your comments to AOPA.