FAA 7460-1 › Montana ›
Building or using a crane near Ravalli County (HRF)?
Ravalli County in Hamilton, Montana is a public-use airport. Under 14 CFR 77.9, anything within 20,000 feet of its runways that rises above a 100:1 slope needs FAA Form 7460-1 at least 45 days before construction. Check your exact site free.
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How tall can you build near HRF without filing?
The notice surface rises 1 foot for every 100 feet of horizontal distance from the nearest point of the nearest runway, starting at the runway's elevation. Using the lowest runway-end elevation, 3,632 ft above sea level:
| Distance from nearest runway | Notice required above (height over 3,632 ft) | …which is this elevation (AMSL) |
|---|---|---|
| 250 ft | 2 ft | 3,635 ft |
| 500 ft | 5 ft | 3,637 ft |
| 1,000 ft | 10 ft | 3,642 ft |
| 2,000 ft | 20 ft | 3,652 ft |
| 3,000 ft | 30 ft | 3,662 ft |
| 5,000 ft | 50 ft | 3,682 ft |
| 7,500 ft | 75 ft | 3,707 ft |
| 10,000 ft | 100 ft | 3,732 ft |
| 15,000 ft | 150 ft | 3,782 ft |
| 20,000 ft | 200 ft | 3,832 ft |
| Beyond 20,000 ft | Only the 200-ft-above-ground rule applies (77.9(a)) | |
If your ground is lower than 3,632 ft you can build taller by the difference; if it's higher, less. Cranes count at their maximum height. The free check above uses USGS ground elevation for your exact spot.
Runways and notice boundary
Dashed line: the 20,000-ft area where the 100:1 notice slope applies; inner line: 5,000 ft.
| Runway | Length | End elevations (ft AMSL) |
|---|---|---|
| 17/35 | 5,200 ft | 3635.6 / 3632.4 |
Filing Form 7460-1 near HRF
- File online through the FAA's OE/AAA system at least 45 days before construction or before applying for a building permit, whichever is first. Filing is free.
- You need NAD 83 coordinates, site ground elevation, structure height above ground and above sea level.
- Construction on airport property always needs notice, whatever the height.
More: Do I need to file Form 7460-1? · Cranes and Form 7460-1
Other public-use airports nearby
- M62 — Rotorcraft (3 nm)
- 32S — Stevensville (16 nm)
- 4U7 — West Fork Lodge (24 nm)
- U05 — Riddick Fld (34 nm)
- MSO — Missoula Montana (40 nm)
- 3U3 — Bowman Fld (52 nm)
Source: FAA airport, runway and runway-end data (NASR cycle effective 2026/10/01). Screening only — the FAA issues determinations.