Surviving VFR into IMC
VFR into IMC events have a distressingly high fatality rate. Here's why they happen and some strategies for surviving based on research into reports from pilots who successfully handled the challenge.
Perhaps you've seen the widely distributed aviation video 178 Seconds to Live. The narrative starts: “The sky is overcast and the visibility poor. That reported five-mile visibility looks more like two and you cannot judge the height of the overcast. . .”
It continues: “. . . You find yourself unconsciously easing back just a bit on the controls to clear those none- too-imaginary towers. With no warning, you are in the soup. . .”
And then, dramatically, “You now have 178 seconds to live!”
Or do you?
As a survivor of a Visual Flight Rules (VFR) into Instrument Meteorological Conditions (IMC) incident that lasted a lot longer than 178 seconds, I often wondered about the veracity of 178 Seconds to Live. It certainly wasn’t true in my case. Where had this video come from? Was it a follow on to those old “scare ‘em straight” propaganda movies they fed us in high school? A post about the video on a social media site mentioned a “study with 20 subjects.”
I started doing research. The oldest reference to the phrase “178 seconds to live” in a VFR into IMC narrative I located was an article with the same title published in the January/February 1993 issue of FAA Aviation News. I then discovered that the “study” was really part of an experiment—the results of which had nothing to do with what eventually became 178 Seconds to Live. And, after the research I conducted into surviving a VFR into IMC encounter, I can’t help but wonder whether teaching that a pilot has but 178 seconds to live has caused fatalities because a some who got into what is a frightening situation gave up rather than do what was needed to survive.
In 1954, the University of Illinois published a report entitled The 180—Degree Turn Experiment. The objective of the experiment was to see if 20 non-instrument-rated pilot subjects could be taught a technique for making a 180-degree turn and controlled descent in instrument meteorological conditions. In order to document the progress of the subjects, there had to be a baseline established for the abilities of each at the beginning of the project. Each pilot was evaluated on his or her ability to maintain control of an airplane under simulated instrument conditions. During his or her initial flight, each subject eventually placed the airplane into what the report referred to as “an incipient dangerous attitude.” The minimum time to reach an incipient dangerous attitude was 20 seconds; the maximum time was eight minutes. The average was 178 seconds.
178 seconds was the average of baseline measurements taken for the purpose of evaluating the results of an experiment.
I think it is also important to note that most of the subjects had little or no experience with the type of aircraft used in the experiment, a Beechcraft Bonanza, and that they were flying it with only a bare minimum of instruments—what we would call partial panel.
Over the years, that baseline measurement took on a life of its own. It morphed from being the initial evaluation of a subject’s ability to control a complex aircraft in simulated, partial panel IMC into an urban myth that an unwary pilot can survive for less than three minutes in an inadvertent IMC encounter. Variations of “178 Seconds to Live” have been promoted by the civil aviation authorities of both Canada and Australia.
Are pilots who encounter IMC on a VFR flight doomed as the video claims? Hardly. While they are seriously at risk, a look at the NASA Aviation Safety Reporting System reports finds that pilots can and do survive VFR into IMC encounters. Researchers at NASA sent supplemental questionnaires to 120 survivors of VFR into IMC events who had sent in what we pilots refer to as “NASA reports” of the encounters (ASRS GA Weather Encounters). The results of the study of the questionnaires returned to NASA researchers present an interesting picture of VFR into IMC incidents and how pilots who have experienced VFR into IMC have successfully coped with the situation. I’ll talk about successful coping techniques after a brief digression into the types of crashes that result from VFR into IMC and how they come about.
VFR into IMC Accident Categories
VFR into IMC accidents almost invariably fall into one of two categories: controlled flight into terrain (CFIT) and loss of control. CFIT, tends to occur in more mountainous regions where terrain and obstacles present a hazard to flight. Loss of control accidents are most often the result of spatial disorientation.
CFIT tends to be the result of a pilot attempting to maintain visual contact with the ground by descending to stay under the weather. In many cases, higher terrain is obscured by clouds and cannot be seen until it is too late to avoid hitting it. An example of this would is an infamous Colorado crash that occurred in August 2008. A instrument-rated pilot loaded his family into a Cessna 182 and departed from Steamboat Springs, Colorado en route to Houston, Texas. The flight departed in marginal VFR conditions with the cloud bases below the mountain tops and the cruising altitude the pilot selected. The aircraft impacted terrain at 12,300 feet on Mt. Guyot in the central Colorado Rocky Mountains. (NTSB No.: DEN08FA141)
As most every pilot knows, spatial disorientation occurs when the brain receives conflicting information from the body's senses that are used to determine orientation relative to the earth. Bluntly: we can no longer tell which way is up. To better understand this, we need to know a little about our senses.
Most people learn in school about the five senses, sight, sound, taste, smell and touch. In reality, we have more senses than that and three play important roles in how we determine our orientation relative to the earth.
Our visual system is what we rely on the most for our sense of orientation. Naturally, it’s our primary sense for determining the airplane's orientation while flying. What might be a surprise is that most of what we use for visual orientation comes from our peripheral vision. When we lose our peripheral vision, as is the case when flying in IMC, we have to rely on our central vision and the use of the aircraft's instruments to understand the airplane's orientation relative to the earth.
The vestibular system, our inner ear is the second of the three orientation senses. It consists of two components that we use to maintain our balance: The semicircular canals and the otolith organ. The otolith organ contains a gelatinous layer that slides over hair cells. When the gelatinous layer causes the hair cells to bend, they trigger nerve impulses that the brain interprets as movement.
The semicircular canals also contain hair cells but are filled with a liquid and are oriented perpendicular to each other. A good way to think of them is that each semicircular canal corresponds to an axis and the three semicircular canals represent roll, pitch, and yaw. These canals are sensitive to rotational movement. The three semicircular canals can be thought of as rate-based gyroscopes.
Both the otolith organ and the semicircular canals are susceptible to the laws of physics. YouTube is full of videos of water being poured into a glass while an air- plane is doing a barrel roll. Bob Hoover was perhaps one of the first to make this demonstration popular. The positive—and coordinated—G load maintained throughout the maneuver allows the water to be poured regardless of the attitude of the aircraft relative to the earth. The same thing happens in our inner ear, fooling the brain into an erroneous perception of the body's orientation relative to the earth.
Finally, the proprioceptive system gives us our overall sense of body position, movement and acceleration. In flying, it can be thought of as “the seat of the pants.” The sensation of movement, the amount of effort required, and the sensation of pressure are communicated via the proprioceptive system. The proprioceptive system is the least involved of the three senses in an IMC situation. Most of our information will be from the visual system, and to a lesser extent, the vestibular system.
Fooling the Inner Ear
As mentioned before, the inner ear can be fooled by acceleration that simulates the effects of gravity on the fluid in our inner ear. Bob Hoover is among many who have demonstrated that any positive G maneuver can “fool” fluid into seemingly defying gravity. If we think of the fluid in our inner ear as behaving identically to the iced tea in Bob Hoover’s famous demonstration, we can envision how our inner ear can send the wrong messages to our brain.
Full motion simulators are designed to fool the inner ear. If you've ever had the opportunity to fly or observe a full motion simulator, you may have noticed how the simulator tilts back during takeoff. This isn't simulating climb; it’s simulating acceleration. As the pilot moves the power levers forward the hydraulics in the simulator tilt it backward. This causes the gelatinous layer in the otolith organ to slide rearward, bending the hair cells and signaling to the brain that the head is tilting back, which it is. However, the visual picture presented to the pilot is of the airplane accelerating down the runway in a level attitude. If the pilot is focusing on the takeoff phase of flight, the brain goes with the visual presentation of forward acceleration and overrides the sensation of tilting backward coming from the otolith organ.
Thousands have tried to dissect the reasons for decisions pilots have made over the decades to start or continue a VFR flight despite obvious warning signs that the weather may not be conducive to doing so. Get-there-itis is one of the most commonly cited. The 2007 NASA GA Weather Encounters study cited a litany of others including time pressure, equipment problems, distraction by passenger or flight crew, fatigue, illness, management pressure, ill patient, insufficient training, insufficient preparation and lack of familiarity with onboard navigation equipment. Awareness of the factors involved in deciding to continue VFR into IMC may help pilots avoid doing so in the future. While researching this article, I found that one of the best training courses for identifying the conditions that lead to VFR into IMC accidents was AOPA’s Weather Wise: VFR into IMC.
Effective Decision Making—Redefining Success
In economics there is the concept of prospect theory. Put simply, prospect theory states that people have a stronger desire to avoid loss than pursue gain.
Decision framing, also known as the framing effect, builds on prospect theory. Decision framing is a bias in which people react differently to a particular choice depending upon how the out- come of the choice is presented. In politics, this is called spin. Outcomes presented as a loss are received negatively and outcomes presented as a gain are viewed more favorable. In their
2001 article, “Visual Flight Rules Into Instrument Meteorlogical Conditions: An Empirical Investigation of the Possible Causes,” published in The International Journal of Aviation Psychology, authors Juliana Goh and Douglas Wiegmann wrote about possible factors that could contribute to VFR flight into IMC. In the article, it was put forth that if a pilot framed the decision to divert as a loss (e.g. wasted time, money, missed opportunity), the pilot might be risk-seeking and choose to continue the flight. If, on the other hand, a pilot frames the decision to divert as a gain (e.g. avoiding loss of lives), the pilot would be more likely to divert. In my opinion, When faced with a potential VFR into IMC situation, it is important to view the decision to escape from the situation as a gain and avoid the temptation to view failure to complete the flight as planned as a loss. By changing this frame of reference, a pilot is more likely to choose to avoid or escape rather than continue into a deteriorating situation. One way to accomplish this reframing is to start with a complete plan B.
One of the factors mentioned in the AOPA Weather Wise course is the problem of “plan continuation bias," a bias towards continuing with the original plan even though there are indications that the situation is deteriorating. Pilots are goal oriented—once they start toward a destination, the do all they can to keep going toward it, even when doing so is no longer in their best interest. One strategy to avoid continuation bias is to have a solid plan B in place prior to the weather encounter. This is more than just an alternate airport; it is a complete plan that provides for an acceptable outcome. An example would be diverting to an alternate airport and renting a car to continue to the original destination. Other alternatives would be to stay over night and continue the next day, call ahead to inform the party you are meeting that you have been delayed by weather and make alternate arrangements. By putting a high priority on having an acceptable alternate outcome already planned prior to departure, the temptation to fixate on completing the flight as originally planned can be avoided. Starting with Plan B reframes escape or diverting as a gain, a positive outcome.
Surviving in the Clag
Avoidance is wonderful—not getting into an emergency situation is always wonderful. My research found that the vast majority of the focus on VFR into IMC education by the FAA and organizations such as AOPA is on avoiding VFR into IMC encounters. However, in the real world, counting on avoidance just isn’t realistic. VFR into IMC encounters occur for a wide variety of reasons. Haze can make it impossible to see a cloud prior to entry. Automated weather reporting stations are widespread but large areas are still not covered and local conditions can vary within a short distance from the reporting station, especially in the west.
Interestingly, another problem is that the ability to accurately perceive visibility varies from individual to individual. In a study published in 2000 by D. Weigmann and J. Goh done at the University of Illinois, 32 subjects were put into a simulator and embarked on a VFR flight with an estimated in route flight time of one hour. During the flight, visibility was gradually reduced from 5 miles to 2 miles. 22 of the 32 subjects continued on after the visibility dropped below the three-mile VFR minimum for operations in the airspace in which they were flying. Pilots can fly into weather where they suddenly cannot control the airplane by outside visual references without realizing they are doing so.
Based on what I learned in the research I conducted after my VFR into IMC encounter, it is my opinion that better training of pilots on how to cope with VFR into IMC is needed. What follows is are recommendations on how to survive a VFR into IMC situation based upon personal experience and research.
Focus on the Instrument Scan.
Surviving an encounter with IMC requires that the aircraft be kept under control. While that’s obvious and basic, it isn’t necessarily easy. The instrument scan is the only way to accomplish this task. A private pilot is required to have a minimum of three hours of instrument time before the checkride. An instrument rated pilot will have some thirteen times more instrument time as of the checkride. It's not surprising that 70 percent of the VFR into IMC survivors in the NASA study were instrument rated. However, instrument rated pilots do succumb to spatial disorientation—approximately 30 percent of the pilots involved in fatal VFR into IMC incidents were instrument rated.
The switch from visual flight to instrument flight requires that the pilot switch from peripheral vision to central vision. And do so quickly. While this change may seem trivial, the conflicting sensations from the vestibular system almost always causes some degree confusion, especially when the need to make the switch is unexpected. Combined with the “startle” factor as well as fright, information to the brain from the vestibular system the pilot may doubt the information being presented by the flight instruments. The conflict can be incapacitating. Above all else, the pilot has to focus on maintaining his or her instrument scan, interpreting what he or she sees and applying appropriate control inputs to keep the airplane under control.
Stay in the Fight.
Having to rely on central vision rather than peripheral vision while battling conflicting sensations from the vestibular system can be exhausting to a pilot not accustomed to flying by reference to instruments or having done so recently. One of the significant challenges to surviving VFR into IMC is, stunningly, resignation. The task of keeping the plane under control is daunting. It may seem overwhelming. What was a stable aircraft in visual conditions suddenly seems like it wants to do anything but fly straight and level, especially if turbulence is involved. It’s not unusual the frustrated pilot to seriously consider just giving up. Giving in to resignation will probably be fatal. As incredibly difficult as things may be, it’s essential that the pilot stay in the fight—remain determined to keep up the instrument scan and keep the airplane under control.
Minimizing head movement will help in the maintaining control battle. The idea is to keep movement of the fluid in the inner ear to a minimum. If you need to look at a chart, table or printed material, raise whatever it is into your line of vision rather than titling your head down. When head movement is required, make the movements slow and deliberate. Routine tasks, such as changing radio frequencies, can become difficult. Break tasks down—for example, if you have to change a radio frequency, do it a little at a time. Change one digit and go right back to the instrument scan and return the airplane to straight and level (it won’t have gotten as far away from right side up as it would had you took the time to put in all of the digits of the new frequency at once). Then change the next digit on the radio and return to your scan. Repeat as needed. When you return to your instrument scan, take as much time as necessary for your vestibular system to settle down before making another change.
To my surprise, I found that in many of the fatal VFR into IMC accidents, the pilot elected to continue to fly in the conditions. That’s foolish. Once you’ve got the airplane under control, the most important next step is to take action to get out of the situation. You’ll probably have a number of options from which to choose. In the 2007 NASA study on GA weather encounters, 46 of 99 pilots who responded chose to land as soon as possible (don’t overlook landing in a field). Others were able to either descend below the weather, deviate around it or get on top of it. The 180-degree turn was used 19 percent of the time. AWOS/ASOS/ATIS broadcasts or on-board weather via ADS-B or satellite can be used to find nearby airports that have acceptable conditions. Having a prepared plan B can make the decision to escape easier and avoid the temptation of plan continuation bias. Your Plan B already has an acceptable outcome built into it—it’s time to use it.
If time and circumstances permit, get on the radio and get help. You’re a pilot; you use resources to complete your flights. When you’re in a jam, ATC can be an extraordinarily valuable resource. ATC can identify airports with suitable conditions for landing and give you vectors to get there. A controller can contact other pilots who may be able to provide PIREPS on areas of VMC. However, the task of identifying the correct frequency for an ATC facility may be more than the pilot can handle at the time. If you are in the habit of using VFR fight following, monitoring local ATC frequencies or having 121.5 selected on the other comm radio, your workload will be reduced. The reality is that you have a life-threatening emergency. Make a call on 121.5, you’ll almost invariably get an answer from an ATC facility. If you’re too low, the chances are good someone flying higher will hear you and help out by relaying your calls to ATC. Your objective is to reduce your workload so that more concentration can be devoted to flying the airplane. Plus, because you have an emergency, if you can get in contact with ATC, declare it. That gives a controller the freedom to put you absolutely first in line for assistance—something you need right now. Don’t be hesitant to declare an emergency because you’re worried about paperwork, there isn’t any—the paperwork myth comes from an old John Wayne movie.
Aviation has a fascination with the morbid. We study accidents in hopes of learning how to avoid the same type of accident in the future. We know a lot about how people die in airplanes—we need to know more about how to survive. While every VFR into IMC crash is investigated we need to know more about the encounters that were handled successfully. Pilots who survive and file NASA reports have helped others—their reports were a part of the VFR into IMC survival strategy in this article. I hope you never have a VFR into IMC event, but if you do, I hope you are able to handle it and that you’ll help other pilots by filing a NASA report and explain how you dealt with the situation.
David Rowland is a long-time private pilot and professional computer analyst specializing in system crashes and performance. He survived a protracted VFR into IMC event some years ago.