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Pilots Must Understand And Evaluate Bad Weather Conditions And Night Flying

Pilots Must Understand And Evaluate Bad Weather Conditions And Night FlyingMany pilots have had the experience of hearing about a weather-related accident and thinking themselves immune from a similar experience. Interviews with pilots who narrowly escaped aviation weather accidents indicate that many of the unfortunate pilots thought the same thing — that is, until they found themselves in weather conditions they did not expect and could not safely handle.

Given the broad availability of weather information, why do general aviation (GA) pilots continue to find themselves surprised and trapped by adverse weather conditions? Ironically, the very abundance of weather information might be part of the answer: with many weather providers and weather products, it can be very difficult for pilots to screen out non-essential data, focus on key facts, and then correctly evaluate the risk resulting from a given set of circumstances.
With improper equipment, ineptitude on the part of the pilot or bad weather, night flying can certainly be dangerous. However, with precautionary planning and with an understanding of night vision shortcomings, night flying can be one of the most pleasant experiences connected with aviation.

About one-tenth of all general aviation accidents occur at night, while fewer than 10 percent of the flying is done after dark. Presuming that night flying is more dangerous than day flying on the basis of statistics is a fallacy. The airplane does not discriminate between light and dark.

Conditions of night flight are different from daytime flying and it is the pilot’s knowledge, or lack of it, combined with a lack of visual clues that present an extra challenge.

A pilot may be subjected to times when the destination airplane lies beyond the rays of the setting sun. Perhaps an engagement becomes a compelling reason to venture out into the black of night.
Flying at night in the mountains is a matter of determining the weather condition to arrive at a personal go/no-go decision. For those who decide to fly at night, an understanding of night vision differences and adjusting the flight operation accordingly, will increase the margin of safety.

Perceive –Process –Perform Risk Management Framework

Perceive: weather hazards that could adversely affect your flight.
Process: this information to determine whether the hazards create risk, which is the potential impact of a hazard that is not controlled or eliminated.
Perform: by acting to eliminate the hazard or mitigate the risk

For many GA (general aviation) pilots, the FAA Flight Service Station (FSS) remains the single most widely used source of comprehensive weather information.

The specific weather information pack aged into a standard briefing includes a weather synopsis, sky conditions (clouds), and visibility and weather conditions at the departure, en route, and destination points. Also included are adverse conditions, altimeter settings, cloud tops, dew point, icing conditions, surface winds, winds aloft, temperature, thunderstorm activity, precipitation, precipitation intensity, visibility obscuration, pilot reports (PIREPs), AIRMETs, SIGMETs, Convective SIGMETS, and Notices to Airmen (NOTAMs), including any temporary flight restrictions (TFRs).

A few guidelines for getting weather data from FSS:
  • DO: be sure to get the right FSS. When you dial the standard number, 1-800-WX-BRIEF from a cell phone, this number will connect you to the FSS associated with your cell phone’s area code – not necessarily to the FSS nearest to your present position. If you are using a cell phone outside your normal calling area, check the Airport/Facility Directory to find the specific telephone number for the FSS you need to reach.
  • DO: know what you need, so you can request the right briefing “package” (outlook, standard, or abbreviated).
  • DO: use the standard flight plan form to provide the background the briefer needs to obtain the right information for you. Review the form before you call, and develop an estimate for items such as altitude, route, and estimated time en route so you can be sure of getting what you need to know.
  • DO: be honest – with yourself and with the briefer – about any limitations in pilot skill or aircraft capability.
  • DO: let the FSS specialist know if you are new to the area or unfamiliar with the typical weather patterns, including seasonal characteristics. If you are unfamiliar with the area, have a VFR or IFR navigation chart available while you listen to help sharpen your mental picture of where the weather hazards may be in relation to your departure airport, proposed route of flight and destination.
  • Do: Ask questions, be assertive. Smart pilot ask questions to resolve ambiguities about weather.
The three basic elements of weather are:
  1. Temperature: (warm or cold);
  2. Wind: (a vector with speed and direction); and
  3. Moisture: (or humidity).

Temperature differences (e.g., uneven heating) support the development of low pressure systems, which can affect wide areas. Surface low pressure systems usually have fronts associated with them, with a “front” being the zone between two air masses that contain different combinations of the three basic elements (temperature, wind, and moisture).

What can weather do to you? Temperature, wind, and moisture combine to varying degrees to create conditions that affect pilots. The range of possible combinations is nearly infinite, but weather really affects pilots in just three ways. Specifically, the three basic weather elements can:

  • Reduce visibility
  • Create turbulence
  • Reduce aircraft performance
How do you evaluate weather data?

One approach to practical weather analysis is to review weather data in terms of how current and forecast conditions will affect visibility, turbulence, and aircraft performance for your specific flight.

Perform – Making a Weather Plan

The third step in practical preflight weather planning is to perform an honest evaluation of whether your skill and/or aircraft capability are up to the challenge posed by this particular set of weather conditions. It is very important to consider whether the combined “pilot-aircraft team” is sufficient. For example, you may be a very experienced, proficient, and current pilot, but your weather flying ability is still limited if you are flying a 1980s-model aircraft with no weather avoidance gear. On the other hand, you may have a new technically advanced aircraft with moving map GPS, weather datalink, and autopilot – but if you do not have much weather flying experience, you must not count on the airplane’s capability to fully compensate for your own lack of experience. You must also ensure that you are fully proficient in the use of onboard equipment, and that it is functioning properly.

One way to “self-check” your decision (regardless of your experience) is to ask yourself if the flight has any chance of appearing in the next day’s newspaper. If the result of the evaluation process leaves you in any doubt, then you need to develop safe alternatives. Think of the preflight weather plan as a strategic, “big picture” exercise. The goal is to ensure that you have identified all the weather-related hazards for this particular flight, and planned for ways to eliminate or mitigate each one. To this end, there are several items you should include in the weather flying plan:

Escape Options: Know where you can find good weather within your aircraft’s range and endurance capability. Where is it? Which direction do you turn to get there? How long will it take to get there? When the weather is IMC (ceiling 1,000 or less and visibility 3 nm or less), identify an acceptable alternative airport for each 25-30 nm segment of your route.
Reserve Fuel: Knowing where to find VFR weather does you no good unless you have enough fuel to reach it. Flight planning for only a legal fuel reserve could significantly limit your options if the weather deteriorates. More fuel means access to more alternatives. Having plenty of fuel also spares you the worry (and distraction) of fearing fuel exhaustion when weather has already increased your cockpit workload.
Terrain Avoidance: Know how low you can go without encountering terrain and/or obstacles. Consider a terrain avoidance plan for any flight that involves:

  • Weather at or below MVFR (ceiling 1,000 to 3,000; visibility 3 to 5 miles)
  • A temperature/dew point spread of 4° C. or less;
  • Any expected precipitation; or
  • Operating at night.

Know the minimum safe altitude for each segment of your flight. All VFR sectional charts include a maximum elevation figure (MEF) in each quadrangle. The MEF is determined by locating the highest obstacle (natural or man-made) in each quadrangle, and rounding up by 100 to 300 feet. Source

NIGHT VISION

Even a competent attitude-instrument pilot will need to use his outside vision during a night flight, if only in the transition during takeoff and landing.
What you see, or don’t see, in the dark is dependent on the state of dark adaptation of your eyes.

If you enter a dark area, your vision improves slowly. After six to seven minutes the eyes are 100 times more sensitive than when you entered the dark. Full adaptation takes 30 minutes, at which time the rods of the eye are 100,000 time more sensitive. This is due to the buildup of a photosensitive chemical called visual purple, the key to night vision. Visual purple is dependent on vitamin A (carrots, eggs, milk, cheese and most vegetables). Vitamin A cannot be stored by the body; it is necessary to eat well-balanced meals before night flying.

Although it takes 30 minutes for dark adaptation to occur, it can be lost in a second or two of exposure to bright light. Minimize the use of white light in the cockpit and keep it as dim as possible.

Dark adaptation is an independent process in each eye. If you are exposed t light, close one eye to preserve half your dark adaptation.

SCANNING TECHNIQUES

The cones of the eye, used for day vision, provide peripheral vision. Night vision uses rods. This creates a blind spot in the center of the eye at night. If you detect something with peripheral vision, the natural tendency is to turn and look directly at it. Night vision is impossible at the center of the eye, so a technique called “off-center scanning” must be developed. Look six to 12 degrees away from the object you wish to see.

AUTOKINESIS

A visual illusion may occur at night if you stare at one light for a long period of time. Involuntary muscle twitches cause the light to be displayed on a different portion of the eye, creating false motion, where the light appears to move. Avoid autokinesis by the off-center scanning technique.

NIGHT TAKEOFF AND DEPARTURE

Before departing from a mountain airport at night, firmly fix in your mind the nature of the terrain and obstructions adjacent to the airport. Pilots have no intention of making an emergency landing shortly after takeoff, especially at night, but it does not hurt to survey the terrain during daylight conditions to form a plan of action.

With the interior lights adjusted to the minimum brightness that affords instrument readability, initiate a normal takeoff.
Acceleration error in the attitude indicator will cause an indication of a higher nose attitude than during a regular climb. As a consequence, some pilots have lowered the nose to the normal attitude and have flown into the ground.
The moment the airplane leaves the ground on a dark night, it is enveloped in black. Outside visual reference becomes impossible. Maintain a positive rate of climb based on the airspeed indication, regardless of the attitude indicator display.

CLIMB OUT

If you become disoriented during the climb out, terrain clearance becomes a big concern. Fly toward the rotating beacon. At airstrips without lighting, fly toward any light on the ground.

TERRAIN CLEARANCE

Proper preflight planning includes studying charts and developing a plan of action. Still, at some time during a night flight, you are going to experience a moment of fear arising from your concern about terrain clearance.
If there are any light around, use them. Fly directly toward the light. As you approach this light, select another light. If the light flickers or disappears, there is something between you and the light. Immediately choose another light to fly toward.
If there is only one usable light in the area, a shuttle climb in a holding pattern may be the most prudent course of action.

To perform a shuttle climb, make a 90-degree turn (direction depends on obstructions) and immediately turn the opposite direction for 270 degrees. This is the same as a 180-degree turn, but keeps the airplane confined to a small geographical area.
Before passing beyond the ground light, perform a 180-degree turn back to the ground light. Continue this maneuvering while climbing to a safe en route altitude before proceeding on course.

WEATHER

It is difficult to see and avoid weather at night. The first indication of a cloud may be a glow emanating from the navigation lights, or a brilliant flash of the strobes being diffused throughout a cloud.

VFR pilots should do an immediate 180-degree turn.
Restricted visibility conditions become apparent with the gradual disappearance of lights on the ground or when they become fuzzy and flow.
Remember, the horizontal visibility through a restriction such as fog, haze or smoke is must less than when looking down through it from above.
Pilots get into trouble trying to land at an airport with fog because they fly over and can see the runway, but when on final approach they can’t see anything.

APPROACH FOR LANDING

Distances at night are deceptive, due to lack of illumination and inability of the pilot to judge them by the usual method of comparing the size of different objects. At night, fly towards an airport light and make a standard pattern, rather than attempting a straight-in approach. The perception of distance can be dealt with by flying the downwind leg until the touchdown point is half-way between the wing tip and tail. They turn onto the base leg.
The only way to approach a runway in the mountains at night, with complete safety, is to incorporate the “spot method for landing” technique. The flare and landing is accomplished in the same manner as during the day. There may be a tendency to look too far down the runway, causing the flare to be too high.

NIGHT FLYING TIPS
  • Always carry a workable flashlight (You can recognize the pilot who has flown at night without a flashlight. He’s the one that has two or more flashlights in his bag).
  • Close one eye when exposed to bright light.
  • Force the eyes to view off-center.
  • Blink the eyes if they become blurred.
  • Do not attempt violent or abrupt maneuvers at night.
  • Watch for the disappearance of ground lights or an area of glow around the navigation lights. This indicates enteringinstrument conditions.
  • Remember the deceptiveness of altitude and speed at night.
  • A normal approach looks steeper at night, creating an illusion of overshooting.
  • Distance judgment at night is less accurate than by day. A simple visual assessment can lead to a premature descent. source Night Flying
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