Rain on ramp
6 min read

During pilot training, some aviation procedures are dutifully explained, yet the context around the procedure is lacking. By “context” I mean the reason, possibly historical, that a rule, process, or procedure is in place, typical scenarios of use, and modes or mechanisms of failure. One prominent example is that of “Special Visual Flight Rules.” Few other procedures elicit mystery and wonder from fellow pilots, wondering how or why these secret code words could be used.

Prior to flying hundreds of hours in the weather-filled Northeast, I also did not recognize the purpose of “special VFR,” particularly once I became instrument rated. Why would not one just file IFR? How could one be guaranteed to be in improved conditions as there are few class G areas left? My instructors had typically never used the procedure before heading off to the airlines, where they would never require it, and thus had little real-world experience with context. After I joined a medical clinic with a weekly aerial commute day or shine, I understood the critical value that this procedure provides.

Patchy fog

Clear blue skies to the northwest, but dense fog to the southeast.

Every pilot learns that special VFR minimums are defined in the Federal Aviation Regulations Section 91.157, which says that special VFR operations may be conducted with air traffic control permission (but ATC will not ask you if you want it), remaining clear of clouds, and at night the pilot needs to be instrument rated and plane instrument capable. The special VFR area extends from the “upward extension of the lateral boundaries of the controlled airspace designated to the surface for an airport” below 10,000 feet.

Let us break all of this down to the basics. What are the purposes of visual weather minimums? Obviously, to ensure that all of us pilots can see each other in time to avoid colliding, when there is no central controlling agency to guard against two pilots being in the same place at the same time. Different classes of airspace have different weather minima primarily due to the density of traffic expected at those locations; more dense or faster traffic equals higher visibility minimums. When weather is above minimums, IFR traffic, controlled by air traffic control at all times, has to be mixed with visual traffic, who may not even have a radio.

At the airport, special VFR allows a controller to transiently lower minimums around an airport so a pilot can leave controlled airspace under visual conditions. Behind the scenes, the controllers will ensure no aircraft in the SVFR pilot’s direction of flight, coordinating with TRSA/TRACON as needed, and issue special VFR clearance. The pilot can fly VFR with Class G minimums until leaving the controlled airspace. Upon leaving the SVFR airspace, the pilot must comply with appropriate weather minimums, typically class E airspace in the continental USA. Thus, unless staying in class G airspace, the pilot must have better visibility upon leaving the lateral boundaries of the SVFR airport (typically class C or D).

Controllers will never suggest special VFR to a pilot. This is primarily to promote safety and prevent putting pressure on a pilot who may not understand the nuances of special VFR or feel comfortable with the procedure. Additionally, special VFR requires protection of airspace to the VFR pilot which temporarily prevents IFR traffic from operating in that area, so busy airports and many class B/C airports specifically prohibit special VFR. While I have never been denied special VFR, on rare occasion I have had to wait many minutes before it was granted while the coordination takes place, similar to obtaining an IFR clearance.

Fog on river

Radiation fog occurs when the ground cools overnight, typically in the shortening days of late fall.

I will describe some typical use cases which illustrate the utility of this tool.

1. The airport is IFR, but it is clearly and obviously sunny that-a-way!

At a routine destination of mine, there is often a bank of advection fog that will sweep over some low mountains and cover half of the airport. There will be minimal visibility in one direction, while in the other direction there will be 10+ miles visibility with an unlimited ceiling, occasionally with the fog even obscuring one half of the runway.

Clearly, taking off and heading in one direction is safe under VFR, while not in the other direction. However, the field is IFR, preventing the non-instrument rated pilot from taking off in a clearly safe environment toward almost instantly better weather. In this case, special VFR will allow takeoff under the “technically IFR” airport conditions and continued flight in safe class E minimums.

2. Lifting morning fog

During my commute I would leave early in the morning, and on cool autumn days there would be radiation fog over the airport. Sometimes the airport would be IFR, however clearly around 100 feet up it would be clear skies. Rather than file IFR, special VFR would allow takeoff from an IFR class D airport in 1-3 miles visibility and continued flight above the fog, which would burn off before I reached my destination.

Occasionally I would ask for special VFR as the ATIS indicated IFR, and controllers would say “hold on…” and the ATIS would be updated with current VFR conditions as the fog lifted. Nevertheless, SVFR would allow takeoff into the obviously improving and near-VFR weather.

3. Icing conditions

A third useful and complex situation for SVFR use involves protection of aircraft from entering icing conditions. At a class D airport I frequent, minimum IFR altitudes are 5,500 feet MSL due to mountains and limitations of radar coverage, and initial IFR instructions will include a climb to 5,500 regardless of destination.

In winter months, the field will often be IFR with visibility of 1-3 miles and a ground temperature of, say 46 degrees F. With the field at 1200 ft, expected freezing levels would be approximately 46-32 = 14 degrees, and 14 deg/ 5.5 deg per 1000ft = 2545 feet, or 3700 MSL. However, just a few miles away from the mountains, IFR altitudes drop to 3500 feet and there is TRACON with approaches to the destination airport.

Rain on ramp

Be sure to calculate those freezing levels in cold rain!

Under these conditions filing IFR is neither prudent nor legal, which would require flight into potentially the worst kind of icing with freezing rain, and the controllers are not able to routinely assign altitudes below the minimum IFR altitudes. However, using special VFR often I have been able to take off from the class D airport into improving conditions and stay below the freezing level, and continue with flight following. Occasionally I switch to IFR and obtain an approach into the destination if needed, now in a region where the enroute and OROCA are now well below the freezing level. As I am talking with the controllers and they know my plans, flying on a discrete squawk code, the whole process is streamlined and performed without difficulty.

I would not advise non-instrument rated pilots to use special VFR unless conditions 1 and 2 are quite clear, and it is extremely obvious that there will be no weather surprises. At night, where clouds are often not visible, a current instrument rating is a must for safe and legal operation. I have been markedly surprised by what appeared to be improving conditions that rapidly deteriorated even when taking off in marginal VFR, not just under SVFR with airport IFR. As Richard Collins says, “The weather you get is not what is promised, the weather you get is what you get.” One needs to always be prepared for those adverse possibilities. Used wisely, special VFR can be a useful tool in the careful operation of light GA aircraft.

G. Stuart Mendenhall
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19 replies
  1. dave sandidge
    dave sandidge says:

    George, thanks for writing about SVFR. I used it often when I was flying a Fairchild Metro III for a commuter airline out of a small GA field in central Virginia (our mx base), down southeast to Richmond everyday to begin passenger services back and forth between Richmond and Washington. The procedure often saved us several minutes each morning while our passengers were impatiently waiting… (We’d enter a left downwind and land on runway 2 under a SVFR clearance while IFR traffic were using the ILS to runway 34). I wonder, too, if a SVFR clearance into and out of Aurora, Ill. (or was it Dupage…), would have saved that Cirrus pilot who ended up killing himself and his two daughters and a boyfriend. ATC would have granted it, and he would have been able to operate, albeit with marginal safety, instead of “getting stuck all day.” He was not IFR rated.

    • G. Stuart Mendenhall
      G. Stuart Mendenhall says:

      Thank you for the comment. You are absolutely right, I listened to that pilot in the ASI “In too deep” again, and perhaps if he just thought he could use SVFR to get in and out he would have landed… However, the pilot sounded so nonplussed / confused he may not had any ability to use it effectively. Certainly when flying in that sort of marginal weather he would have been better served to simply have the instrument rating!

  2. Ron Horn
    Ron Horn says:

    Thank you for the excellent review of SVFR. I do almost all of my flying in the arid Southwest so I’m not sure I’ve ever been introduced to the condition. Being a VFR pilot I’m glad to be reminded of it.

  3. G. Stuart Mendenhall
    G. Stuart Mendenhall says:

    You are welcome – the procedure can add to safety when used in appropriate situations, but just enjoy the sunny days. There are not as many of them in the Northeast!

  4. Helo 1
    Helo 1 says:

    I was once denied a SVFR request while transitioning the shoreline transition for KLAX 100 ft. AGL or below. I had already transitioned this corridor earlier in the day but the ceiling dropped along with the visibility, upon my return. I circumnavigated inland in order to avoid the surface class Bravo airspace, only to find out later that SVFR is clearly noted as “SVFR NOT AVAILABLE” on the Terminal Chart. Lesson learned ;-)
    Helo 1

  5. James Frankenfield
    James Frankenfield says:

    I remember, years ago, when Richard Collins, in one of his superb editorials, had filed IFR to terminate at Trenton N.J., when he was advised that the field was below IFR miniums. This was before the field had ILS. His solution….asked for a SVFR which allowed for a safe and legal approach and landing. Jim

  6. John
    John says:

    G.S.M: Thanks for a nice summary of both the rule, and how it works for you.

    During the summer months in many western States smokey conditions can be widespread. Frequently visibilities hover between 1 and 2 miles. SVFR is a tool for short hops that would otherwise be impossible VFR or IFR when one or more of the departure/destination pair lack approaches. It is also a tool best used with IFR training and the rating to go with it.

  7. Mort Mason
    Mort Mason says:

    In Alaska, “Special VFR” was known simply as a “Zone Clearance”, and was almost never granted for arrivals. I have performed untold numbers of Zone Clearances. Typically, they are granted as: ‘Cleared below 500 feet to five miles east of the field. No clearance will be granted for a return to this field’. Also typically, such clearance is granted when heavy snow showers limit visibility to less than one-half mile and the ceiling is undetermined. This, of course, leads to some serious scud running. All in all, not for the faint of heart, and I don’t recommend it . . .

  8. Warren Webb Jr
    Warren Webb Jr says:

    Excellent review of SVFR. At Hartford-Brainard KHFD, there were plenty of times during the year when the weather was below basic VFR down to vis 1 and I had lessons scheduled. Special VFR allowed us to do the lesson. Plus I thought it had another great benefit – the students could get a first hand look at really marginal weather from the cockpit. The point I would make is get a good briefing to avoid this stuff. But just in case they did find themselves in some marginal weather, another benefit was that these lessons got them somewhat adjusted to maintaining safe control in very marginal conditions.

    I also could depart and arrive sometimes with primary students when the main runway 2/20 was socked in. Runway 29 started on the west edge of 2/20 – I’d depart to the west into decent VFR conditions and land on runway 11, with 2/20, closer to the river, still unusable.

  9. G. Stuart Mendenhall
    G. Stuart Mendenhall says:

    Dry vs moist vs environmental lapse rate. It basically depends on air moisture in addition to other factors (movement of air masses). For theoretical / rule of thumb calculations, it is safer to use a higher lapse rate and assume a lower freezing level and be pleasantly surprised, than encounter lower freezing or icing conditions.


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