Definition
A specific paragraph within Title 14 of the Code of Federal Regulations, Part 91, section 155, that addresses VFR flight visibility and cloud clearance requirements when operating in Class G airspace beneath the ceiling of a Class B, C, D, or E surface area at an airport. It permits a helicopter, powered parachute, or weight-shift-control aircraft to operate clear of clouds with reduced visibility under specified conditions, and it also restricts fixed-wing aircraft from landing or taking off, or entering the traffic pattern, at an airport in Class G airspace beneath such a ceiling unless ground visibility is at least 3 statute miles (or, if ground visibility is not reported, flight visibility during landing/takeoff/traffic pattern operations is at least 3 statute miles).
Plain English
A short rule inside the federal aviation regulations that sets the visibility and cloud-distance limits for flying VFR in uncontrolled airspace right under a controlled airport's airspace ceiling. In plain terms: if you're flying under the 'shelf' of a busy airport's airspace, the regulation tells you how clear the weather has to be before you can land, take off, or fly the traffic pattern there.
Context Anchor
Seen when studying basic VFR weather minimums, especially before departing from or arriving at an airport inside controlled airspace that begins at the surface.
Derivation
In a regulation citation, “section” means a numbered part of a rule. “91” refers to Part 91, the operating rules for most general aviation flying, “155” is the specific rule on basic VFR weather minimums, and “(c)” points to one paragraph inside that rule.
Why Pilots Care
It determines whether a VFR flight can continue legally when the ceiling drops near an airport or whether an ATC clearance or flight plan is required instead.
Grounding Statement
If the cloud base over the controlled airport area is below 1,000 feet, normal VFR flight under that cloud layer is not allowed there.
Intuition Check
Do not read section 91.155(c) as a general weather minimum for every place and every situation. It is a specific rule for VFR flight beneath a ceiling in controlled airspace that is designated to the surface for an airport.
Example Sentence 1
Because the field sits beneath the Class C shelf and the ATIS reported ground visibility of only 2 miles, section 91.155(c) prohibited him from entering the traffic pattern VFR.
Example Sentence 2
The instructor used section 91.155(c) to explain why a lower ceiling forces either a flight plan or an ATC clearance near the airport.