AIM Text
Pilots are urged to report any bird or other wildlife strike using FAA Form 5200-7, Bird/Other Wildlife Strike Report (Appendix 1). Additional forms are available at any FSS; at any FAA Regional Office or at https://www.faa.gov/airports/airport_safety/wildlife/. The data derived from these reports are used to develop standards to cope with this potential hazard to aircraft and for documentation of necessary habitat control on airports.
Source: FAA Aeronautical Information Manual · current edition · paragraph 7-5-3.
Research Notes
AIM 7-5-3 covers Mountain Wave — the standing-wave phenomenon downwind of mountains.
Mountain wave physics: Strong steady winds (typically 25+ kts at ridge level) blowing perpendicular to a mountain ridge create standing waves on the downwind (lee) side. These waves can extend hundreds of miles downwind and to altitudes well above the ridge.
Wave characteristics:
- Wavelength: ~10-50 NM
- Vertical velocity: can exceed 1,500-2,000 fpm up and down
- Lenticular clouds ("flying saucers") often mark wave crests
- Severe turbulence in rotor clouds at the base of waves
Recognizing mountain wave:
- Lenticular clouds (smooth, lens-shaped, stationary)
- Cap clouds on mountain peaks
- Rotor clouds (turbulent, ragged, in lines)
- Wind shear at altitude (sudden airspeed/altitude changes)
Operational impact: Severe up/downdrafts can cause altitude excursions of 1,000+ feet without pitch changes. Rotor turbulence can cause structural overload. Wave at altitude is what makes glider records — pilots reach FL400+ in lee waves. But for powered aircraft it's typically a hazard.
Avoidance: Cross ridges at higher altitudes (50% above ridge height where possible). Cross at 45° to maintain escape options. Time crossings for lower-wind hours.