V = Environment
Weather is a major environmental consideration. As pilots set their own personal minimums, they should evaluate the weather for a particular flight by considering the following:
- What are the current ceiling and visibility? In mountainous terrain, consider having higher minimums for ceiling and visibility, particularly if the terrain is unfamiliar.
- Consider the possibility that the weather may be different from forecast. Have alternative plans and be ready and willing to divert should an unexpected change occur.
- Consider the winds at the airports being used and the strength of the crosswind component. [Figure 3-5]
- If flying in mountainous terrain, consider whether there are strong winds aloft. Strong winds in mountainous terrain can cause severe turbulence and downdrafts and be very hazardous for aircraft even when there is no other significant weather.
- Are there any thunderstorms present or forecast?
- If there are clouds, is there any icing, current or forecast? What is the temperature-dew point spread and the current temperature at altitude? Can descent be made safely all along the route?
- If icing conditions are encountered, is the pilot experienced at operating the aircraft’s deicing or anti-icing equipment? Is this equipment in good condition and functional? For what icing conditions is the aircraft rated, if any?
Evaluation of terrain is another important component of analyzing the flight environment.
- To avoid terrain and obstacles, especially at night or in low visibility, determine safe altitudes in advance by using the altitudes shown on visual flight rules (VFR) and instrument flight rules (IFR) charts during preflight planning.
- Use maximum elevation figures (MEF) [Figure 3-6] and other easily obtainable data to minimize chances of an inflight collision with terrain or obstacles.
- What lights are available at the destination and alternate airports (e.g., visual approach slope indicator (VASI), precision approach path indicator (PAPI) or instrument landing system (ILS), glideslope guidance)? [Figure 3-7] Is the terminal airport equipped with them? Are they working? Will the pilot need to use the radio to activate the airport lights?
- Check the Notices to Airmen (NOTAMS) for closed runways or airports. Look for runway or beacon lights out, nearby towers, etc.
- Choose the flight route wisely. An engine failure gives the nearby airports supreme importance.
- Are there shorter or obstructed fields at the destination and/or alternate airports?
- If the trip is over remote areas, are appropriate clothing, water, and survival gear onboard in the event of a forced landing?
- If the trip includes flying over water or unpopulated areas with the chance of losing visual reference to the horizon, the pilot must be prepared to fly IFR.
- Check the airspace and any temporary flight restrictions (TFRs) along the route of flight.
Night flying requires special consideration.
- If the trip includes flying at night over water or unpopulated areas with the chance of losing visual reference to the horizon, the pilot must be prepared to fly IFR.
- Will the flight conditions allow a safe emergency landing at night?
- Preflight all aircraft lights, interior and exterior, for a night flight. Carry at least two flashlights—one for exterior preflight and a smaller one that can be dimmed and kept nearby. [Figure 3-8]
The human eye will see nothing outside that is dimmer than the flight deck lighting. Always fly at night with the interior lights as dim as possible. As the flight progesses and the eyes adjust to the darkness, usually the interior lights can be dimmed further, aiding the outside vision. If the interior lights will not dim, that would increase the risk factors by restricting the pilot’s outside vision—probably not the time for a night flight.
Although weather, terrain, airport conditions, and night versus daylight flying each produce unique challenges, together these factors conspire against a pilot’s senses. It is important to understand that unwittingly these factors can create visual illusions and cause spatial disorientation producing challenges the pilot did not anticipate. [Figure 3-9] Even the best trained pilots sometimes fail to recognize a problem until it is too late to complete a flight safely.
An accident involving a Piper PA-32 and an airline transport pilot illustrates how visual illusions can create problems that lead to an accident. In this case, the aircraft collided with terrain during a landing. The sole occupant of the airplane was an airline transport pilot who was not injured. The airplane owned and operated by the pilot, sustained substantial damage. The personal transportation flight was being operated in visual meteorological conditions (VMC) in mid-afternoon. Although it was not snowing, there was snow on the ground.
Originally on an IFR flight plan, the pilot canceled his IFR clearance when he had the airport in sight. According to the pilot, he was familiar with the airport, having landed there repeatedly in the past. However, it had just snowed, leaving a thin layer of snow and mixed ice on the runway. The pilot in this case allowed his familiarity with the airport coupled with his flight experience give him a false sense of confidence. As a result, he failed to realistically assess the potential snow and ice hazard on the runway—an assessment overshadowed by his own self-assurance exacerbated by his familiarity and experience.
On the day of the accident, the runway was covered with one inch of snow and ice. Previously plowed snow lined the runway. Although he had not landed on a snow-covered runway in 10 years, the pilot felt his knowledge of the runway environment and familiarity with the airfield would compensate for this lack of currency in landing in these types of conditions. During the final approach, the visual cues normally available to a pilot were not present. That is, the snow-covered terrain presented problems for the pilot in ascertaining proper depth of field, recognized as a visual illusion. When he landed, his normally available lateral visual cues were obscured by the snow, causing him to come in at a higher altitude than he normally would have. Disoriented by the snow and lacking knowledge on how to adapt properly to these conditions, he was unable to determine his position relative to the runway centerline and landed left of the intended point. By focusing his attention on the snow banks, he drifted further toward the edge of the runway causing one of the airplane’s main gears to miss the runway surface.
The risk at hand could be addressed in the following manner. Does landing on snow and ice require any special skills? Do you have these skills? Are you current in using these skills? If landing in ice and snow requires special airmanship skills that transcend normal pilotage and you do not have that skill or you are no longer experienced in this situation, then the risk is increased and you need to recognize that just because you are a pilot does not mean you are proficient at doing all of the maneuvers you are legally qualified to perform. Examine seaplane ratings, mountain training, and tail-wheel proficiency. This proficiency starts to wane the moment a pilot stops performing maneuvers requiring these skills.
Immediately after touching down, the wheel that was off the edge of the runway hit a snow-covered mound of previously plowed snow. The impact threw the airplane sideways and it collided with more of the previously plowed snow. During this sequence, all three landing gear struts collapsed and the underside of the airplane sustained considerable structural damage.
What could this pilot have done to prevent this accident from happening? In addition to maintaining currency in landing on a snow-covered runway, he could have prevented this accident by choosing an alternate airport that had a cleared runway. He could have taken another pilot, junior or senior to his overall experience who has landed in similar conditions recently. Certainly he could have been better prepared. He could have read about landing in these conditions and better prepared himself for landing on snow and ice. He could have planned. Before landing on snow-covered terrain, a pilot needs to understand how to accomplish the landing since the techniques are not the same as those for landing on a clear, dry runway. In this example, the pilot applied the same methods of ascertaining depth perception as normally used if the terrain were not blanketed in snow.
In this case, the basic underlying problem was the pilot’s failure to prepare for the conditions. He knew the challenge that faced him, and he had the assets to prepare himself better, yet he did not. In reality, the hazard in this case is not just the snow or the challenges it presented, but the pilot himself in being overly confident and even complacent to his responsibilities. Had this aircraft been carrying passengers and had the accident occurred under slightly different conditions, the end result could have been tragic.
The first and key step in preparing for a new situation is to recognize that one may not have the required skill set—the step of recognzing personal limitations. The next step is acquiring that skill set. A pilot who has never landed on snow, or one whose skills have eroded from lack of recent practice, can do the following to acquire or renew the skill set necessary for a successful landing in snow conditions:
- Review reference materials to reinforce and increase knowledge about visual illusions and their causes:
- Fly with an instructor pilot or other PIC who has had significant experience in landing on snow.
- Participate in a training designed specifically for landing in unusual places and environments. Many pilots attend classes on mountain flying in which they learn techniques to use in the absence of standard visual cues.