One of Winter's Flying Traps - Whiteout

Article by Francis Bélanger and Denis Veilleux, published in the November-December 1998 issue of La Brousse, reprinted with permission

As winter approaches, it is recommended that you review particular aspects of what the snowy season holds in store for you. Among other things, it is wise to review your aircraft’s operations manual, check the equipment that has to be carried for winter flights and think about the weather features associated with flying in winter. Besides snow and cold, winter presents a number of new phenomena with which we have to come to terms. One of these is the whiteout. We will focus on this phenomenon, because it holds great risks for the safety of a flight.

Definition

(A.I.P., AIR 2.12.7)

"An atmospheric optical phenomenon of the polar regions in which the observer appears to be engulfed in a uniformly white glow. Neither shadows, horizon nor clouds are discernible; sense of depth and orientation is lost; only very dark, nearby objects can be seen. Whiteout occurs over an unbroken snow cover and beneath a uniformly overcast sky when, with the aid of the snowblink effect, the light from the sky is about equal to that from the snow surface . . ."

More simply put, the phenomenon occurs when you are in the presence of a large flat area and the overcast sky blends in with the ground. You get the impression of being inside a bowl of milk or a ping-pong ball. It is impossible to make out the horizon and distance from the ground. Pilots flying VFR therefore lose all the essential clues for continuing their flight safely, even if visibility remains adequate and the ceiling is high.

The phenomenon can be caused or amplified by mist (BR), blowing snow (BLSN) or precipitation in the form of small ice or snow crystals (IC). (See the table of weather codes in the MET section of your A.I.P.)

The hazards

Here is an excerpt from a TSB accident report:

"The pilot of the C-185 departed in VFR conditions and climbed to 400 ft. AGL. Five miles on, he encountered whiteout conditions over a lake. His instruments indicated a descending left turn. He did not trust them, because he did not feel the turn. When he realized that the instruments were not lying, it was too late. The aircraft hit the ice, and the left wing was sheared off. Fortunately, once all the pieces came to rest, the pilot was unhurt and able to walk away."

Should you encounter such conditions when flying VFR, you would likely suffer spatial disorientation for lack of visual cues. No longer able to see the horizon, you may go into a turn without realizing it. The turn may become a spiral, ending, in the worst case, in impact with the ground. If you do not lose control of your aircraft, you may become one more statistic in the CFIT tables. As it is impossible to determine your altitude visually, slow descent might not be detected before impact occurs. The best-case scenario would be for you to come away with one more piece of experience to your credit as a pilot, without bending metal.

Prevention and preparation

As we have no control over this kind of phenomenon, the only ways to reduce the hazards of whiteout are to:

1. Avoid it;
2. Recognize it; and
3. Trust your instruments.

Avoiding whiteout is not easy, especially if you are flying in areas above the tree line (the limit on mountains and high latitudes beyond which trees will not grow because of the cold). In this case, the weather conditions in which you are willing to fly will be a determining factor. In the areas of the far north it is not easy to fly VFR in completely overcast weather. Discounting the possibility of staying on the ground, an IFR flight would be your best bet to minimize the hazards of whiteout. Unfortunately, this is not always possible. Before deciding to depart, you would do well to analyse weather briefings and forecasts. Do not trust overcast ceilings, even light precipitation and winds stronger than 15 kt. Wind favours the development of BLSN aloft if associated with mechanical turbulence or an unstable air mass. Ice crystals or light snow are then raised aloft and reduce horizontal visibility, producing a whiteout. Note that area forecasts (FA) report only winds exceeding 20 kt.

If you are operating in areas farther south, below the tree line, you have to distrust the same factors as you would if you were planning to fly over large expanses, such as frozen bodies of water. Whiteout is easily avoided simply by changing course to always keep the treetops, a chain of islands, a road, a railway or a power transmission line within your field of view. These objects will help you to retain sufficient visual clues to perceive depth and determine the attitude of your aircraft.

Careful study of the proposed route will help you to determine the kind of terrain and obstacles that you will be flying over. You will be able to identify places where the whiteout phenomenon would be likely and to alter your route to avoid areas that you believe to be risky. The sacrifice of a little time and fuel is really a very small price to pay to ensure a safe flight.

Despite all the precautions in the world before your flight, and even if you stay alert during the flight, you may still encounter whiteout conditions. The phenomenon could be manifested in various signs, depending on your experience and the phase of flight. Disorientation (see A.I.P., AIR 3.9), loss of the sense of balance, nausea and the feeling of having entered an all-white envelope are all possible sensations. You may also not experience any sensation at all, and that is where the greatest danger lurks. If you are qualified for VFR only and briefly consult your instruments, you may have the same reaction as the pilot in the example given above. As your vision and centre of balance no longer provide you with accurate clues, you will tend not to believe what your instruments tell you. This is a normal reaction because your piloting skills are based mainly on VFR and "flying by the seat of your pants." If you should find yourself in such a trap, what should you do?

Our recommendations

Regardless of the situation you encounter, it is always important to keep your head. First, it is essential to be willing to use your instruments to help you, even if they seem to be wrong. I am assuming here that they were in good working order on departure, and that you are unable to pass over to IFR. Here is how to proceed:

1. Consult the attitude indicator - Keep the wings parallel with the ground and fly level.
2. Note the altitude - Make sure to establish yourself at a high enough altitude to cross obstacles without danger.
3. Check your heading - Maintain a heading that will take you to terrain or ground presenting objects that you can distinguish.

Turning back might be an option, but I recommend it only if weather conditions seem to be worsening to the point of jeopardizing your VFR flight. Such a manoeuvre involves nothing less than making a 180-degree turn without any visual reference, that is, in IFR! Can you perform such a manoeuvre? Each case is unique. You alone can weigh the risks and decide on the best course of action to re-establish a safe and comfortable flight regime.

The whiteout phenomenon is very real, and it has outwitted more than one pilot in the past. Regardless of the type of landing gear on your aircraft and where you fly, this phenomenon can catch you unaware. A good measure of prevention will be your main asset for avoiding whiteouts, with weather conditions and the terrain being the two factors to analyse. If you are unlucky enough to encounter this phenomenon, stay calm and perform minimum manoeuvres. If you have to manoeuvre, do so gently. Changes in attitude should be of the order of 3°. As for banks for turns, between 10° and 15° will be enough.

As winter can severely test your piloting skills, it would be wise to undertake rigorous preparation. We suggest taking a few hours of your time to practice IFR under dual control. IFR is a skill that erodes with time. If you have not done this kind of flying for more than a year, you are probably a little rusty! Remember, the more well-honed tools you have in your chest of pilot skills, the more ready you are to face the challenges of piloting your aircraft.

On that note, good flying and happy holidays!

Your ideas, impressions and comments about the contents of this article may be submitted by e-mail to This email address is being protected from spambots. You need JavaScript enabled to view it. or by regular mail through the secretariat of the APBQ.

Essay: Kennedy's Design-induced Sprial

by Stanley N. Roscoe, PhD, published with permission from Aero Innovation Inc., Montreal, Quebec.

Attitude Indicators: What moves?

The three display modes all indicate a bank to the right. The left indicator is rotated counterclockwise. In the centre indicator, the aeroplane symbol is rotated clockwise. In the right indicator, the horizon is the same as on the left, but, in addition, the aeroplane symbol is rotated clockwise by the pilot's aileron input, indicating that the plane will continue to roll to the right. The instrument represented on the left is the standard system in today's aeroplanes, including John Kennedy's Piper Saratoga II. With the display at the right, pilots maintain wings-level flight merely by aligning the aeroplane symbol with the horizon, a natural response.

Flight experiments support the conclusion that John Kennedy Jr. became spatially disoriented in the absence of a visible horizon in conditions of poor visibility. The overwhelming probability is that he wound up in what is known by pilots as a "graveyard spiral." That is exactly what 19 out of 20 similarly trained pilots did with the loss of a visible horizon in an experiment at the University of Illinois 45 years ago (Bryan, Stonecipher and Aron, 1954).

Later experiments at Illinois have shown that a simple addition to the conventional "artificial horizon" indicator on the instrument panel can virtually eliminate this type of accident, one that kills many people every year in general aviation and can even occur in commercial aviation (Roscoe, 1997). For the aviation community to correct this situation, someone in the media has to expose the problem, someone in government has to listen, and someone important has to die.

In conditions of poor visibility, inexperienced pilots get into screaming spiral dives in several ways, but this is the most common: While the pilot is looking for lights on the ground or other horizon reference, the aeroplane slowly rolls into a banked attitude. With no horizon visible, the pilot looks at the "artificial horizon" indicator in the cockpit and notices that the horizon bar is not level. The initial reaction is to roll the horizon bar back to level, which rolls the aeroplane into a steeper bank. This is known as a horizon control reversal.

In a steep bank, the nose of the aeroplane drops, and the aeroplane starts to lose altitude. To hold altitude the pilot pulls back on the wheel, which tightens the turn and steepens the spiral dive. At this point the pilot is confused, totally disoriented and no longer in control of the aeroplane. Such a sequence can and does happen very rapidly, and the resulting crash is invariably attributed to pilot error. No doubt the pilot made the error, but what caused the error is never determined, nor the probable cause reported.

The term "pilot error" is misused when such errors can be prevented by an experimentally proven equipment modification. In the case of flight attitude control, all that is needed is to cause the "little aeroplane" symbol on the artificial horizon indicator to rotate in direct response to aileron control inputs. Thus, to return to a wings-level attitude, the pilot merely has to align the aeroplane symbol with the displaced horizon bar and maintain that alignment as the real aeroplane and the artificial horizon bar, rotating in opposite directions, both return to wings-level.

To illustrate, if the aeroplane rolls to the right, the horizon bar rolls left. The pilot notices this and applies left aileron to align the aeroplane symbol with the horizon bar, causing the plane to start rolling back towards wings-level. As this is going on, the pilot gradually reduces the left aileron input to maintain alignment until the ailerons are neutral when the wings are level. Thus, straight-ahead flight is restored.

Stanley N. Roscoe, PhD, WW II pilot, is emeritus professor of aviation engineering psychology and aeronautical and astronautical engineering, University of Illinois at Urbana-Champaign; emeritus professor of psychology, New Mexico State University; former head of the Display Systems Department of Hughes Aircraft Company; president of ILLIANA Aviation Sciences Limited of McKinleyville, California, and Las Cruces, New Mexico; and senior vice-president of Aero Innovation, Inc., an aviation human factors company of Montreal, Quebec. For more on this topic, visit http://www.aero.ca/e_kennedy%27s_spiral.html.

Flight Itinerary, ELT, and Survival Plan

One Monday in early March, a pilot and his friend were preparing to go on a fishing trip from lac aux Sables to lac Drouin, Quebec, in a ski-equipped Piper PA12 in visual flight rules (VFR) conditions. The pilot told his wife they would be back Friday if the weather permitted, but said she was not to worry if conditions were poor, because they would wait until the weather improved.

After three uneventful days of fishing, the two men decided to depart lac Drouin at noon on Thursday and return to lac aux Sables one day before they had planned to avoid bad weather. On the same day, a commercial carrier in Latuque grounded its aircraft because of adverse weather, including freezing rain and reduced visibility.

A few minutes after take-off, the aircraft encountered snow, then mist, and finally entered mist, but the pilot still did not adopt a new plan. The aircraft crashed in cruise flight on lac Sincennes, about 40 mi. west of Latuque, in conditions conducive to white-out. The aircraft was severely damaged, but both occupants survived the crash.

The pilot sustained head injuries, and the passenger’s jaw and two legs were fractured. The men moved away from the aircraft because they feared it would catch fire. A short time later, the pilot gave the passenger a sleeping bag that he kept in the aircraft, and told him he was going for help. Unfortunately, there was no emergency locator transmitter (ELT) on the aircraft, and, of course, the only person who knew their itinerary was told that they would not return until Friday. But even worse: she was told not to worry if they didn't make it back on Friday.

By Sunday, having received no news from her husband, the pilot’s wife told a friend that her husband had not yet returned, but that she thought he was staying at the cabin until the weather cleared. Search and Rescue (SAR) was notified at 19:20 EST on Sunday, and the aircraft was found the next morning, Monday, around 08:30.

The pilot’s body was found half a mile from the wreckage. He had dug three holes in the snow at different locations, probably for shelter from the weather. The injured passenger could not seek shelter in the wreckage because the pain from his fractures was too intense. He spent three nights in the sleeping bag on the frozen surface of the lake. By Sunday morning — the first nice day — his legs were both frozen but he was able to crawl to the wreckage. The severely injured passenger was finally rescued on Monday morning, but his legs had to be amputated below the knee.

Analysis - What’s left to analyse? The events recounted above are clear enough, and the lessons are also clear. Your flight plan or itinerary is crucial, and you absolutely must file it like a professional, no matter where you are going. Never make a vague plan or your rescue could be at risk.

If you must depart sooner, always advise a responsible person by whatever means are available before departing, or as soon as possible afterward. If proper notification is impossible, stick to your original plan or leave later, not sooner, but advise the authorities to avoid an unnecessary search.

If you have no ELT on board and you fly over isolated areas, you are taking unacceptable risks. This recent accident is exactly what we are all trying to prevent, and it is regrettable that the story had to be told here.

Finally, in a survival situation, there are some basic rules that everyone should know. First, it is essential to provide for your own well-being and that of your passengers. That means: give first aid, find or build a shelter as close as possible to the accident site, and, if you can, make a fire to keep warm and maintain morale. Once physical protection is taken care of, find a source of water, and, if possible, food. Think about preparing signal fires, especially if the site is hard to see from the air. If you venture away the site for any reason, blaze your trail on the trees so you can find your way back. SAR will find you sooner or later. If you have never had survival training, call the nearest SAR Centre for further details.

The passenger's life was almost certainly saved by the sleeping bag, and this proves the value of having survival gear on board. However, is it possible that both men could have survived if the pilot had stayed with the passenger so they could keep each other warm, and so they could reassure each other while waiting? At the very least, the pilot would have had a greater chance of survival. The decision to go for help in these circumstances, although honourable, was, it would seem, an error in judgment as to the initial action to take in a survival situation.

And last but not least, regarding flight in marginal weather - as we all know - aviators should never play Russian roulette with the weather because five out of six chambers will be loaded!