PVFR and the Single Pilot
Visual Flight Rules is a set of operating rules that require reported ceilings to be 1000 feet or more and visibilities of three miles or more for operation under VFR. Part 91 specifies cloud clearance requirements required for operation under Visual Flight Rules. I also found Instrument Flight Rules, or IFR-a set of operating rules that govern flight operations when ceilings are below 1000 feet and/or visibilities are below three miles or when VFR cloud clearance can’t be maintained. Nothing ambiguous there, you might argue.
But the definitions for these same acronyms when they are given in a weather forecast. For example, what does it mean when a terminal forecast predicts the weather at my destination to be VFR at the time of my proposed arrival? In this context I found a description of “VFR weather” as indicated when ceilings are greater than 3000 feet and visibilities are greater than five miles or significantly better weather than that required to operate under “basic VFR” according to the regulations. In the forecast context, IFR weather is defined as ceilings of 500 to 1000 feet, and/or visibilities of one to three miles. Searching further, I found “Low IFR”, described as the condition when ceilings are less than 500 feet and/or visibilities are less than one mile. Finally, I found defined “Marginal VFR”, or MVFR-when ceilings are between 1000 and 3000 feet, and/or visibilities are between three and five miles.
Confused yet? Remember, one set of definitions represents the conditions that must prevail for us to legally operate under a specific set of operating rules. The other set of definitions are used purely for interpreting or “visualizing” forecasts. Different definitions for the same term can be confusing.
In real life, what we really care about when we are operating under VFR is whether we can see well enough to maintain a wings level attitude and navigate by visual references. If you think about it, neither of the above noted definitions for “VFR” gives the pilot assurance that he or she can see well enough to fly in the prevailing conditions. They offer some indication, of course, but no assurances. Part of the problem is the way we learn about weather and its effects on flying during our pilot training days.
When someone uses the term “VFR weather”, what comes to mind? Most folks probably don't visualize three miles visibility and an overcast at 1100 feet. Are we properly equipping our pilots-in-training with the vocabulary and the understanding of what is required to safely operate an aircraft visually? Pilots often hear the magic term “VFR conditions”, and they’re ready to go flying. By the same token, many pilots accept the oft-heard boilerplate from Flight Service stating “VFR flight not recommended” as a commandment. Unfortunately, most pilots are never exposed to actual marginal weather during their flight training. Three or four mile visibility can be very disorienting, and the perspective from five or six hundred feet agl presents a very different view, and a different set of challenges, than flight at 3000 feet agl.
Most of all, I believe we fail to teach primary pilots what is really important is not so much whether the conditions meet some specific set of standards, but rather whether the pilot will actually be able to see anything while in flight. This, after all, is the essence of visual flight. What the operational pilot should really care about is whether he or she can see well enough to keep the aircraft in a desired attitude and successfully navigate to his or her destination. Unfortunately, none of the above weather descriptors necessarily assure the pilot of being able to achieve that outcome safely.
After my experience in Kotzebue, I began to refer to this sort of weather condition as “PVFR”. I define PVFR as: A situation where the meteorological conditions meet the definition of “basic VFR”, but conditions are such that there are too few visual references within the range of the prevailing visibility to keep the airplane upright by reference to a visual horizon, and to safely navigate. In other words, the pilot is actually in Instrument Meteorological Conditions (IMC). PVFR, as you may have guessed, stands for Pretend Visual Flight Rules. To simplify the definition a bit: PVFR prevails when one is in VFR weather conditions, but can’t see anything except the aircraft's instrument panel.
It is not just the multiple definitions that can be a problem for the aviator. First, one must determine what the conditions are, and are most likely to be, throughout the flight. Then one must determine whether those conditions are adequate to safely operate in over the proposed route of flight. Basic VFR conditions in the prairie states may result in IMC in the mountains. When the flight takes us over water or trackless terrain, three miles visibility may not be adequate for safe operation.
Some pilots suggest that this notion of Pretend VFR is principally an Alaskan winter phenomenon, but examples can be found in all seasons and in the lower 48 as well. Not convinced? Try flying in the mountains of our western states during a summer when forest fires are raging.
Flying a Cessna 185 north from Fairbanks one summer day in two to three miles visibility in smoke, I received a report from the pilot of a helicopter to the north of me that conditions deteriorated significantly further north. I executed a 180 degree turn, and as I faced into the sun, my forward visibility went to virtually nothing. A difference in sun angle was enough to completely change the effective visibility. Unfortunately, this occurred in mountainous terrain, and at low altitude. When visibilities lower, most pilots naturally fly closer to the surface, ostensibly to maintain better ground contact. A heart-stopping climb to a safe altitude, followed by a pop up instrument clearance back to Fairbanks completed my flying day, safely, but with plenty of food for thought.
Consider the conditions encountered flying on the east coast in the heat of summer, when visibilities are rarely more than a few miles. I suspect that in those conditions, most pilots are relying much more heavily on their instruments than they may realize or admit. That new GPS unit is pretty handy here, eh? Even though conditions may be above basic VFR criteria, a vacuum failure or electrical failure could easily precipitate a very real emergency, or at the very least some uncomfortable moments.
Now imagine being seven miles off shore over the ocean, at night, with prevailing visibilities in haze of around five miles. I suggest that PVFR may have been an important factor in the John F Kennedy, Jr. accident. If you are seven miles offshore, and the visibility isn’t seven miles or more, there is simply nothing outside the aircraft by which you can maintain visual orientation. As in the previous examples, while this condition may meet the legal requirements for VFR flight, these are, in fact, instrument meteorological conditions. If the pilot is not instrument proficient, and perhaps more importantly, if the pilot fails to recognize that he or she is actually in IMC, the flight is very likely to end in tragedy. Remember, these meteorological conditions would be accurately described as VFR, and would be briefed as such in a pre-flight weather briefing.
So, what can the prudent pilot do to ensure that he or she doesn’t fall into the PVFR trap? First, we all need to give a little more thought and study to the definitions used in weather forecasts. Not just the examples listed above, but for example, in a forecast, what does the term “occasional” mean, as opposed to “frequent” or “intermittent”? How about “widespread” versus “isolated”? A functional understanding of the definitions of weather and forecast terminology is essential to successfully interpreting the available weather products. An appropriate interpretation of the weather briefing and an understanding of what the weather descriptors mean, is vital to safe VFR flight.
Secondly, the next time you are driving your automobile in smog or heavy snow, look critically at what you see out the window, and imagine what that view would mean in an aircraft operating under VFR, perhaps at night. The idea is to learn to picture what forecasted weather actually looks like in real terrain. On days when you opt not to fly because of forecast inclement weather, pay attention to the actual weather conditions that evolve as the day progresses. This will not only help you to visualize weather conditions based on a forecast, but also help you to improve your forecast evaluation skills.
Next, find a competent instrument instructor who is willing to do some VFR flying on a marginal day. Use good judgment in your choice of places to fly, and the weather you fly in. Study the country carefully on a clear day in advance, so that you have a good hazard map of obstacles and their heights prior to flying on a poorer weather day. Above all, in your experimentation, be sure that you have the option of safely transitioning to IFR if need be. This experiment, like mine in Kotzebue, will help you understand that a weather report of basic VFR conditions may or may not imply that it is actually safe to fly in those conditions visually.
The idea is not to train you to fly visually in marginal conditions, but rather to show you how ugly PVFR can be, and how dangerous that operating condition really is. The idea is to encourage you to avoid those conditions.
Above all, every pilot needs to understand the conditions he or she is operating in. You are either in safe, functional visual conditions, or you are in instrument conditions. Unfortunately, there is no clear and well defined line between the two, so learn to evaluate the effect the prevailing conditions may have on your flight. Understand whether you’re fish or fowl on every flight, and never mix the two, except to retreat to safety. If you find yourself creeping into PVFR, it’s time to perform a strategic retreat, and the earlier, the better.
Finally, learn to fly in instrument meteorological conditions, and stay as current on instruments as your budget and schedule will permit. Remember though-every year a number of instrument rated pilots succumb to PVFR and fly their aircraft into a mountain or other object, albeit right side up. The problem these pilots encountered was PVFR of the most insidious sort—VFR conditions which degrade into a condition where there is simply nothing to see out the windshield. Unfortunately, the transition is often subtle, the pilot is reluctant to “pop up” IFR, and after a while, the pilot may not know precisely where he or she is. Denial allows the pilot to get in deeper and deeper. The pilot has now entered deeply into the world of PVFR flight, and there are few conditions more dangerous in general aviation.