FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesHard
A pilot is flying an RNAV (GPS) approach with LNAV minimums and is on the final approach segment, 2 NM from the runway threshold. Approximately what does full-scale CDI deflection represent at this point, and how does it compare to a VOR's sensitivity at the same distance?
- A±0.3 NM, which is narrower (more sensitive) than VOR's ±10° angular deflection at that distance
- B±5.0 NM, much wider than VOR sensitivity
- C±10°, the same angular value as a VOR at any distance from the station
- D±1.0 NM, identical to VOR sensitivity at all distances
Show answer & explanationAnswer & explanation
Correct answer: A. ±0.3 NM, which is narrower (more sensitive) than VOR's ±10° angular deflection at that distance
RNAV GPS approach CDI sensitivity scales linearly from ±1.0 NM in the terminal area down to ±0.3 NM on the final approach segment near the runway, providing tighter lateral guidance than a VOR's constant ±10° angular deflection, which widens in physical distance as range from the station increases.
Why the other options are wrong
- B. ±5.0 NM is the enroute sensitivity, far too wide for final approach.
- C. VOR CDI sensitivity is always ±10° angular, but RNAV sensitivity is linear (NM-based), not angular, so they are not the same.
- D. ±1.0 NM is the terminal-area sensitivity, not the tighter final approach segment value.
RNAV CDI Sensitivity vs VOR
RNAV systems use linear (distance-based) CDI scaling that narrows as the aircraft approaches the runway, while VOR CDI sensitivity is always angular (±10°) regardless of distance from the station.
- RNAV enroute sensitivity: ±5.0 NM full-scale deflection
- RNAV terminal sensitivity: ±1.0 NM full-scale deflection
- RNAV final approach segment sensitivity: ±0.3 NM full-scale deflection at the runway
- VOR sensitivity: always ±10° angular, regardless of distance
Memory trick: RNAV narrows like a funnel; VOR stays a fixed angle cone