AIM Text
A pilot departing VFR, either intending to or needing to obtain an IFR clearance en route, must be aware of the position of the aircraft and the relative terrain/obstructions. When accepting a clearance below the MEA/MIA/MVA/OROCA, pilots are responsible for their own terrain/obstruction clearance until reaching the MEA/MIA/MVA/OROCA. If pilots are unable to maintain terrain/obstruction clearance, the controller should be advised and pilots should state their intentions.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-4-9.
Research Notes
AIM 4-4-9 covers altitude restrictions — when ATC imposes specific altitude requirements at specific points along a route.
Common altitude restrictions:
- 'Cross [fix] at [altitude]': Aircraft must be at the specified altitude when crossing the fix (no earlier than the fix, and no higher/lower than the altitude depending on phrasing).
- 'Cross [fix] at or above [altitude]': Must be at the altitude or higher when crossing
- 'Cross [fix] at or below [altitude]': Must be at the altitude or lower when crossing
- 'Maintain [altitude] until [fix]': Cannot leave the assigned altitude until reaching the fix
SID/STAR altitude restrictions: Many published Standard Instrument Departures and Standard Terminal Arrival Routes have built-in altitude restrictions at specific waypoints. These restrictions are MANDATORY when the SID/STAR is part of the clearance, unless ATC specifically cancels them.
The 'descend via' clearance: Common on arrivals. "Descend via the JOFLY ARRIVAL" means follow all altitude restrictions on the published STAR. This shifts altitude management to the pilot (working from the chart) rather than ATC issuing each restriction separately.
Reference: § 91.123; AIM 4-4-9; AIM 5-4-1 (Arrival Procedures).