That’s because, in order to get a special VFR clearance from the ATC facility controlling the airspace, ground visibility at the departure airport must be at least one statute mile. If ground visibility is not reported at the airport, as in this situation, then flight visibility must be at least one statute mile.
This has been the problem. Except for the regulatory change, technically, a pilot on the ground cannot determine flight visibility. Flight visibility is by definition determined by a pilot from the cockpit. The FAA interprets this definition to mean that flight visibility can only be determined when an aircraft is airborne.
Ground visibility, on the other hand, is an officially reported condition, not a pilot observed condition. Ground visibility is defined to be “the prevailing horizontal visibility near the earth’s surface as reported by the United States Weather Service or an accredited observer.” A pilot, unless he/she also happens to be an accredited weather observer, cannot report ground visibility.
Unless there happens to be a pilot in flight who reports back the flight visibility conditions (who doesn’t have to be an accredited observer), our pilot on the ground is stuck. ATC has been reluctant to issue a special VFR clearance when the weather at the main airport was reported to be visibility less than a mile. A regulatory change solves this situation, and in explaining it, gives us an opportunity to review the “special VFR” regulation.
Let’s start with the basics (forgive the pun) of FAR 91.155 that all pilots know but like to be refreshed about from time to time. (There are additional requirements for student and recreational pilots). Let’s look particularly at the “basic” (as distinguished from “special”) VFR weather minimums that apply to VFR operations at an airport within controlled airspace. By that I mean an airport that has controlled airspace that begins at the surface of the airport. That’s any airport within Class B, C, and D airspace. That’s also any airport within Class E airspace that begins at the surface of the airport (not an airport that has Class G airspace at its surface with Class E airspace above). The basic VFR visibility minimums that apply in this airspace are: at least three statute miles ground visibility, and at least three statute miles flight visibility. In other words, a pilot may not operate an aircraft to or from such an airport under VFR with less than three miles visibility, both ground and flight.
Also as part of the basic VFR requirements, if the ceiling being reported at the airport is less than 1,000 feet, an aircraft may not be operated VFR beneath the ceiling.
For completeness we must mention that within this airspace the “basic” cloud clearance minimums also apply. Here they are. A pilot may not operate an aircraft at a distance from clouds that is less than 500 feet below, 1,000 feet above, and 2,000 feet horizontally. (Not relevant here, but remember that there are stricter minimums in controlled airspace above 10,000 feet MSL.) There is one interesting exception to these cloud clearance requirements. In Class B airspace, which presumably has the highest density of traffic, an aircraft may be operated closer to clouds than these minimums. The minimum is “clear of clouds,” the same minimum we see in some Class G, uncontrolled airspace, and in special VFR operations. It makes sense, if you think about it. All aircraft in Class B airspace are being provided separation service by ATC. And it would cause problems for the controllers if pilots refused radar vectors or routings because following them would cause less than the required cloud clearances.
Which brings us to the “special VFR” rules of FAR 91.157. We can get a break from the “basic” minimums if we first obtain a special VFR clearance from the ATC facility that has jurisdiction of the airspace. Then the “special” and not the “basic” VFR minimums apply. The special VFR weather minimums are one-mile flight visibility and clear of clouds. Under the special VFR rules, in addition to the flight visibility minimum, there is also a ground visibility minimum. An aircraft may not takeoff or land under special VFR unless ground visibility is at least one mile. If ground visibility is not reported, then flight visibility must be at least one statute mile.
Back to our pilot on the ground at the satellite airport. He can’t take off because ground visibility is not reported at the satellite airport, and he can’t make a flight visibility determination because he is not in flight. This is a dilemma that has now been resolved.
Since May 23, 2000, FAR 91.157 has been amended to expand the term “flight visibility” to include the visibility from the cockpit of an aircraft in takeoff position at a satellite airport that does not have weather reporting capabilities. This allows a pilot at such an airport to determine whether the visibility minimums exist for a special VFR departure. If the pilot on the ground determines that the visibility is one mile or more, special VFR is permissible.
The amendment makes clear that a pilot’s determination of flight visibility from the cockpit of an aircraft on the ground is only for the purpose of the special VFR rule. All other flight visibility determinations must be made in flight. Similarly, it makes clear that this visibility determination is not an official ground visibility report, since the pilot is not an official weather observer. The amendment also makes clear that this relaxation applies only to flights conducted under Part 91.
The rest of the rules governing special VFR operations still apply.
For special VFR at night, the pilot must be rated and current for instrument flight, and the aircraft must be equipped for instrument flight. For this rule (it's different for other rules) night is considered to be the time between sunset and sunrise. (In Alaska, the "instrument" requirement applies when the sun is less than 6 degrees above the horizon.)
Helicopter operators get some additional benefits. A helicopter may be operated special VFR without the one-mile visibility minimum. And for special VFR at night, a helicopter pilot does not have to be instrument rated, and the helicopter does not have to be equipped for IFR.
While a special VFR clearance may be obtained at most airports within controlled airspace, it is not permitted for fixed-wing aircraft at some 33 specifically identified airports; they are indicated on visual charts and in aeronautical publications. As you would guess, they are the airports with the highest traffic density.
Our explanation of the technical difference between ground and flight visibility is important to pilots beyond this rule change. Where an airport in controlled airspace officially reports the weather, a pilot operating an aircraft at that airport (taking off, landing, or entering the traffic pattern) is bound by the reported ground visibility. Otherwise, and most often, the visibility minimum is flight visibility as observed by the pilot from the cockpit. For example, an aircraft transiting the controlled airspace, but not operating at the airport, must maintain flight visibility of at least three miles but is not bound by the officially reported ground visibility.
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John Yodice is the Senior Partner of the Law Offices of Yodice Associates, a law firm experienced in aviation legal matters involving DOT, FAA and TSA certification and compliance, corporate governance, aircraft transactions and more. www.yodice.com