Understanding FAR 91.155: Basic VFR Weather Minimums Explained
If you’re a pilot or aviation enthusiast, you’ve likely encountered Federal Aviation Regulations (FARs), now codified under Title 14 of the Code of Federal Regulations (14 CFR). One of the key rules for Visual Flight Rules (VFR) operations is § 91.155, which outlines the basic weather minimums required to fly VFR. These minimums ensure safety by specifying required visibility and distance from clouds in different airspaces.
In this blog post, we’ll break down the entire regulation, including its structure and key components. Then, we’ll dive deeper into paragraphs (c) and (d), as they often raise questions among pilots. This explanation is based on the current text from the electronic Code of Federal Regulations (eCFR). Note that regulations can be amended, so always check the official sources for the latest version.
Overview of § 91.155
The regulation sets the minimum flight visibility and cloud clearance distances for VFR flights in various classes of airspace. It applies to all aircraft operating under VFR, with some exceptions noted in the text.
Paragraph (a): General VFR Minimums Table
Paragraph (a) provides the core of the rule: No one may operate under VFR if visibility or cloud distances fall below the specified levels for the airspace and altitude. Here’s the table summarizing these minimums:
| Airspace | Flight Visibility | Distance from Clouds |
|---|---|---|
| Class A | Not Applicable | Not Applicable |
| Class B | 3 statute miles | Clear of Clouds |
| Class C | 3 statute miles | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| Class D | 3 statute miles | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| Class E (Less than 10,000 feet MSL) | 3 statute miles | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| Class E (At or above 10,000 feet MSL) | 5 statute miles | 1,000 feet below, 1,000 feet above, 1 statute mile horizontal |
| Class G (1,200 feet or less above the surface, regardless of MSL altitude) | ||
| - For aircraft other than helicopters (Day) | 1 statute mile | Clear of clouds |
| - For aircraft other than helicopters (Night) | 3 statute miles | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| - For helicopters (Day) | 1/2 statute mile | Clear of clouds |
| - For helicopters (Night) | 1 statute mile | Clear of clouds |
| Class G (More than 1,200 feet above the surface but less than 10,000 feet MSL) | ||
| - Day | 1 statute mile | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| - Night | 3 statute miles | 500 feet below, 1,000 feet above, 2,000 feet horizontal |
| Class G (More than 1,200 feet above the surface and at or above 10,000 feet MSL) | 5 statute miles | 1,000 feet below, 1,000 feet above, 1 statute mile horizontal |
This table covers controlled (A-E) and uncontrolled (G) airspaces, with variations for day/night and altitude. Exceptions are referenced in paragraph (b) and § 91.157 (Special VFR).
Paragraph (b): Exceptions in Class G Airspace
In uncontrolled airspace below 1,200 feet above ground level (AGL), certain operations have relaxed rules:
- Helicopters: Can operate clear of clouds in an airport traffic pattern within 1/2 mile of the runway/helipad if visibility is at least 1/2 statute mile.
- Airplanes, powered parachutes, or weight-shift-control aircraft: At night, if visibility is between 1 and 3 statute miles, they can operate clear of clouds in an airport traffic pattern within 1/2 mile of the runway.
These allow for safer operations near airports in marginal conditions.
Paragraph (e): Clarification on Class E Airspace
This paragraph notes that an aircraft at the base of Class E airspace is considered within the airspace below it, ensuring consistent application of rules.
Deep Dive into Paragraph (c)
Paragraph (c) states: “Except as provided in § 91.157, no person may operate an aircraft beneath the ceiling under VFR within the lateral boundaries of controlled airspace designated to the surface for an airport when the ceiling is less than 1,000 feet.”
In simpler terms, this prohibits VFR flight under a cloud ceiling below 1,000 feet in surface-based controlled airspace (like Class B, C, D, or E at airports). This airspace extends from the surface up to a certain altitude around airports.
Why? Safety. Low ceilings increase the risk of controlled flight into terrain (CFIT) or other hazards near airports. If the ceiling is below 1,000 feet, pilots must either fly IFR (Instrument Flight Rules) or request Special VFR clearance under § 91.157, which allows operations with reduced minimums (e.g., clear of clouds and 1 statute mile visibility) but requires ATC approval.
Key points:
- Applies only to controlled airspace at the surface.
- “Beneath the ceiling” means you’re flying VFR under the clouds.
- Doesn’t apply if you’re above the clouds or in uncontrolled airspace.
For example, if you’re approaching an airport in Class D airspace and the reported ceiling is 800 feet, you can’t fly VFR into that airspace without Special VFR.
Deep Dive into Paragraph (d)
Paragraph (d) reads: “Except as provided in § 91.157 of this part, no person may take off or land an aircraft, or enter the traffic pattern of an airport, under VFR, within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport— (1) Unless ground visibility at that airport is at least 3 statute miles; or (2) If ground visibility is not reported at that airport, unless flight visibility during landing or takeoff, or while operating in the traffic pattern is at least 3 statute miles.”
This focuses on airport operations in controlled surface airspace. It requires at least 3 statute miles of visibility for VFR takeoffs, landings, or pattern work.
Breakdown:
- Ground visibility: This is the official visibility reported at the airport (e.g., via METAR or AWOS).
- If no ground visibility is reported (common at smaller airports), pilots use their own flight visibility assessment.
- Applies specifically to surface areas of Class B, C, D, or E around airports.
- Again, Special VFR (§ 91.157) can be an exception with ATC clearance.
This ensures pilots have adequate visibility for critical phases of flight near airports, reducing collision risks. For instance, if ground visibility is 2 miles, you can’t depart VFR; you’d need IFR or Special VFR.
Why These Rules Matter
FAR 91.155 is all about promoting see-and-avoid principles in VFR flying. By mandating minimums, the FAA helps prevent accidents due to poor weather. Paragraphs (c) and (d) add extra layers of protection around busy airport environments.
If you’re studying for a pilot certificate or just refreshing your knowledge, remember: Always check current weather against these minimums, and when in doubt, stay on the ground or go IFR.
For the full official text, visit the eCFR page for § 91.155. Safe flying!