Which navigation aids are commonly used as a GNSS substitute to determine aircraft position?

Which navigation aids are commonly used as a GNSS substitute to determine aircraft position?

• A. VOR and DME
• B. ILS and MLS
• C. ADF and transponder
• D. GPS and GLONASS

Answer: (A)

Ground-based radio navigation aids like VOR and DME let you determine where you are without relying on satellites. VOR gives the aircraft a direction (bearing) from the station, while DME gives your distance from that station. When you have signals from more than one VOR/DME station, you can pin down your position by the intersection of the lines or distance rings created from those stations. This is why VOR combined with DME is commonly used as a GNSS substitute for positioning, especially when satellite navigation is unavailable or degraded. The other options don’t serve as reliable GNSS substitutes for en-route position fixes: ILS and MLS are precision approach systems, not general-position navigation tools; ADF provides bearing information to an NDB but is less precise and not typically used for accurate position fixes; transponders offer identity and altitude information but not direct position; GPS and GLONASS are GNSS themselves, not substitutes for GNSS.

Ground-based radio navigation aids like VOR and DME let you determine where you are without relying on satellites. VOR gives the aircraft a direction (bearing) from the station, while DME gives your distance from that station. When you have signals from more than one VOR/DME station, you can pin down your position by the intersection of the lines or distance rings created from those stations. This is why VOR combined with DME is commonly used as a GNSS substitute for positioning, especially when satellite navigation is unavailable or degraded.

The other options don’t serve as reliable GNSS substitutes for en-route position fixes: ILS and MLS are precision approach systems, not general-position navigation tools; ADF provides bearing information to an NDB but is less precise and not typically used for accurate position fixes; transponders offer identity and altitude information but not direct position; GPS and GLONASS are GNSS themselves, not substitutes for GNSS.