AIM Text
- Title 14 CFR specifies the pilot and aircraft equipment requirements for IFR flight. Pilots are reminded that in addition to altitude or flight level requirements, 14 CFR section 91.177 includes a requirement to remain at least 1,000 feet (2,000 feet in designated mountainous terrain) above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown.
- IFR Altitudes. (See TBL 3-3-1.)
TBL 3-3-1
IFR Altitudes
Class G AirspaceIf your magnetic course (ground track) is:
And you are below 18,000 feet MSL, fly:
0° to 179°
Odd thousands MSL, (3,000; 5,000; 7,000, etc.)
180° to 359°
Even thousands MSL, (2,000; 4,000; 6,000, etc.)
Source: FAA Aeronautical Information Manual · current edition · paragraph 3-3-3.
Research Notes
AIM 3-3-3 covers IFR Requirements in Uncontrolled Airspace — IFR ops in Class G.
IFR in Class G: Legal but NOT recommended. ATC has no authority and provides no separation. Two IFR aircraft in clouds in Class G are responsible for their own separation — see-and-avoid in IMC is impossible.
When this arises: Approach to non-towered airports in Class G. IFR clearance terminates at the IAF (Initial Approach Fix). The aircraft proceeds without ATC separation services into the Class G airspace below.
Best practices: Maintain CTAF self-announce. Use ADS-B In for traffic awareness. Be aware of other IFR aircraft approaching the same airport.