FAA Aircraft Dispatcher (ADX)Navigation and ATCMedium
A dispatcher is checking VOR service volume classifications for enroute planning. A VOR is designated Class 'H' (High Altitude). What is the usable range at 45,000 feet MSL and above (up to 60,000 ft)?
- A130 nautical miles
- B100 nautical miles
- C40 nautical miles
- D25 nautical miles
Show answer & explanationAnswer & explanation
Correct answer: B. 100 nautical miles
For a High altitude (H) class VOR, the standard service volume provides 40 NM from 1,000 to 14,500 ft, 100 NM from 14,500 to 18,000 ft, 130 NM from 18,000 to 45,000 ft, and 100 NM from 45,000 to 60,000 ft.
Why the other options are wrong
- A. 130 NM applies to the FL180–45,000 ft band, one altitude band lower.
- C. 40 NM applies to the lower altitude band (1,000–14,500 ft), not the highest band.
- D. 25 NM corresponds to a Terminal (T) class VOR, not High altitude class.
VOR Service Volumes
VORs are classified (T, L, H) with standard service volumes defining usable signal range at various altitude bands; High-altitude VORs have the largest overall coverage.
- Terminal (T): 25 NM, 1,000–12,000 ft
- Low (L): 40 NM, 1,000–18,000 ft
- High (H): 40 NM to 14,500 ft, 100 NM to 18,000 ft, 130 NM to 45,000 ft, 100 NM to 60,000 ft
Memory trick: 'High goes far, then shrinks near the top' — H-class range expands then contracts above 45,000 ft.