FAA 7460-1 › Montana ›
Building or using a crane near Townsend (8U8)?
Townsend in Townsend, 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.
No address handy? Try 16700 Saticoy St, Van Nuys, CA 91406
How tall can you build near 8U8 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, 3,875 ft above sea level:
| Distance from nearest runway | Notice required above (height over 3,875 ft) | …which is this elevation (AMSL) |
|---|---|---|
| 250 ft | 2 ft | 3,877 ft |
| 500 ft | 5 ft | 3,880 ft |
| 1,000 ft | 10 ft | 3,885 ft |
| 2,000 ft | 20 ft | 3,895 ft |
| 3,000 ft | 30 ft | 3,905 ft |
| 5,000 ft | 50 ft | 3,925 ft |
| 7,500 ft | 75 ft | 3,950 ft |
| 10,000 ft | 100 ft | 3,975 ft |
| 15,000 ft | 150 ft | 4,025 ft |
| 20,000 ft | 200 ft | 4,075 ft |
| Beyond 20,000 ft | Only the 200-ft-above-ground rule applies (77.9(a)) | |
If your ground is lower than 3,875 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 | 4,000 ft | 3874.7 / 3892.6 |
Filing Form 7460-1 near 8U8
- 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
- 7S6 — White Sulphur Springs (26 nm)
- HLN — Helena Rgnl (27 nm)
- 3U9 — Boulder (27 nm)
- 9S5 — Three Forks (27 nm)
- MT15 — Fort Harrison Aaf (31 nm)
- BZN — Bozeman Yellowstone Intl (36 nm)
Source: FAA airport, runway and runway-end data (NASR cycle effective 2026/10/01). Screening only — the FAA issues determinations.