BY JOEL STOLLER (From AOPA Flight Training, September 2004.)
When was the last time you went out to the airport at night to do some touch and goes and brush up on your night flying skills? To fulfill the night currency requirements to carry passengers, they actually need to be full-stop landings, but we'll explore the regulatory aspects of night flying a little later.
Ninety-five percent or more of flight time logged by private pilots takes place in daylight. This statistic seems to warrant a close review of night flying techniques, since we seem to fly at night so infrequently. As members of the human species and from a physiological point of view, we are better adapted for daytime activities.
Anatomy textbooks speak of human vision comprising two types: photopic vision for daytime and scotopic vision for nighttime. The visual receptor cells packed into the eye's retina are called cones and rods; they convert light into the electrical energy needed to generate nerve impulses conducted through the optic nerves. Only about 10 percent of the light that enters the eyes reaches the receptor cells — most of it is reflected or absorbed in other parts of the eye. There are about 7 million relatively thick cones in the human eye used for daytime, or what could be termed color, vision and about 120 million slender rods used for night vision. The low illumination of nighttime demands a huge increase in these receptor cells in order for any light reception to take place at night.
Chapter 8-1-6 of the Aeronautical Information Manual, Medical Facts for Pilots, addresses a few concerns of pilots while operating at night. In darkness, vision becomes more sensitive to light; a process called dark adaptation. Dark adaptation usually takes 30 minutes in total darkness, but it can be achieved in 20 minutes under dim red cockpit lighting. Red light severely distorts colors on aeronautical charts and causes difficulty when trying to focus on objects inside the cockpit, so white cockpit lighting is necessary for chart and instrument reading and should be used as necessary — but keep the overall cockpit illumination at your lowest comfortable level. Cabin altitude pressures above 5,000 feet, smoking, exhaust fumes (carbon monoxide), and vitamin A deficiency also impair dark adaptation. Sudden exposure to a bright light ruins dark adaptation within seconds, so pilots should close one eye when a light (for example, a flashlight in the cockpit) is used, to preserve some degree of night vision.
Night for aviators is defined as "the hours between the end of evening civil twilight and the beginning of morning civil twilight, as published in the American Air Almanac, converted to local time." Note that "civil twilight ends in the evening when the center of the sun's disk is 6 degrees below the horizon and begins in the morning when the center of the sun's disk is 6 degrees below the horizon."
So now you know exactly when you should log night time. Remember, to act as pilot in command while carrying passengers, you must have made at least three takeoffs and landings to a full stop in the preceding 90 days in the same aircraft category, class, and type, during the period beginning one hour after sunset and ending one hour before sunrise.
Thomas Edison's invention of the light bulb is the little miracle that makes all of this night activity possible. What lights do you need to fly safely at night? Common sense dictates the answer here, but some are regulatory in nature. A safe nighthawk always carries at least two working flashlights in the flight bag and a penlight in his or her pocket. Next is to be sure that all required aircraft lights for night operations are installed and working. Check all lights on your preflight walk-around. These include the position lights (or what are sometimes placarded navigation or nav lights): left wing red, right wing green, and aft or tail position white. These position lights must be on from sunset to sunrise. An anticollision light system is also required for night (and day) operations, which may include one or more strobe and/or rotating beacons that may be colored either red or white.
If your aircraft has a rotating beacon and supplementary strobes, keep the strobes off until cleared for takeoff. Use the "lights, camera, action" (lights on, transponder on, power normal and airspeed alive) callout to help you remember this as you acknowledge takeoff clearance from the tower, or when you are ready to take the active runway at an airport without an operating control tower. Strobes on at night while taxiing can harm other pilots' night vision.
This is also the time to turn on landing lights to bring attention to the fact that you are rolling on takeoff. (Some single-engine aircraft have a dual taxi/landing light configuration, with the taxi light either a lesser wattage lamp or aimed more toward the near foreground area ahead of the aircraft's taxi path). Remember that other aircraft operating on adjacent taxiways or runways may not be monitoring the same frequency or controller from whom you just received your takeoff clearance.
While getting some currency at night with an instructor, simulate a "burned out" landing light approach and landing to a full stop. It can and does happen — and may happen to you some night for real. You must now gauge your depth perception in the landing flare with the white runway edge lights, as there will be little forward illumination. Being prepared for any eventuality is the only way to operate safely in a world ruled by "Murphy's Law" — anything that can go wrong, will go wrong. If you have access to a realistic night simulator, practice a few of these in the simulated environment. If you regularly use simulators at your flight school to supplement training, choose the night simulation if available to increase your confidence in a night cockpit and night flight scenario.
If aircraft marshallers (usually line personnel from the fixed-based operator) are available at your airport for parking and exiting parking areas, use them as a safety resource at night. This is part of a wide-ranging use of cockpit resource management, as every pilot should employ every available resource to enhance safety. The hand signals are the same for night or day operation (found in Section 4-3-25 of the AIM); marshallers employ red-lighted wands at night.
Blue surface lights indicate the edges of taxiways, and larger airports have green taxiway centerline lighting as well. Always check local notices to airmen (notams) before night operations to determine the status of an airport's taxiway and runway lighting. Occasionally, segments of taxiway lighting may be inoperative, adding a new hazard to taxiing at night — the line between pavement and grass may be extremely difficult to see or determine. Use caution, and taxi slowly.
I have come to the conclusion after many hours of night flying in VFR conditions that there are four major concerns that must be addressed in your night flight training and any subsequent night flying you do after earning your private pilot certificate. Number one is the optical illusion that occurs while flying on clear moonless nights over sparsely populated areas. (Interestingly, this phenomenon is also readily seen at jet cruising altitudes.) The widely spaced lights below, such as street lamps or home porch lights, seem to blend with visible stars above the horizon, making it difficult to ascertain where the actual horizon is to establish the proper reference for straight-and-level flight. Obviously this can lead to spatial disorientation in the cockpit while trying to establish a level pitch attitude or to complete turning maneuvers using visual cues. The lack of visual cues at night is one reason that night flying is often compared to instrument flight. Nearer to metropolitan areas or in the airport environment, this appears to be less of a problem, because ground lighting better defines the actual horizon. If you ever begin to feel disoriented at night, use your artificial horizon and airspeed and altimeter trends to regain control while disregarding false motion sensations created by your inner ear balance system. This is a fundamental precept of instrument flying.
The next night caution for pilots is another disorienting phenomenon in VFR conditions (exacerbated by a little summertime haze) that results when flying toward a large body of water. As the shoreline is reached and the ground below you disappears, the horizon is now basically lost, and you are essentially flying in "instrument conditions" even though the visibility may be reported as six miles or better. While approaching and landing at an airport with featureless terrain and few ground lights (sometimes called "the black hole approach"), an illusion can be created that the aircraft is at a higher altitude than it actually is (see "Bottomless Pit," October 2003 AOPA Flight Training). Obstacles in the approach path near the runway threshold, such as 50-foot trees, are difficult to see clearly at night until you are virtually just above them. Always use the VASI/PAPI light system for glidepath guidance, and if this is not available, keep rates of descent the same as you would during a normal daylight approach and landing (500 to 700 fpm rate of descent on final). Remember the basic VASI memory cue: "Red over white — you're all right, red over red — you should dread."
The third night caution involves obstacles. These come in a variety of forms, including buildings near approach paths, TV/radio antenna towers, and electrical utility towers. The most commonly observed obstacle lighting is "aviation red obstruction lights," flashing aviation red beacons that flash 20 to 40 times per minute or burn steady red on structures not taller than 200 feet. The next type you have observed is "medium or high intensity flashing white obstruction lights" on structures 500 feet or higher. A word of caution here: If the obstruction happens to be a TV/radio antenna tower, there may be guy wires (steel cables) radiating from the top of the structure down to the ground, 360 degrees around the structure. These are not lighted in any way, and they may be impossible to see at night. So keep a safe distance away from these structures (1,000 feet above within a horizontal radius of 2,000 feet) and you'll avoid any cables that may extend horizontally from the lighted vertical structure. What you can't see may definitely hurt you! These obstacles are clearly marked on VFR sectional charts — be sure that your charts are current and always check notams before flying, as the "information age" is creating an ever-increasing amount of new communications towers.
The final major concern of most pilots flying at night is engine failure. Engine failure in good weather and daylight conditions is challenging enough. Now add some of the additional hazards that we have been discussing to the picture, and to quote a phrase, "You definitely have your hands full." Assuming a restart is not possible and you are not within gliding distance of an airport, more altitude always allows you more time to come to a suitable decision on the best off-airport site for landing. Your procedures are basically the same as if the emergency occurred in daylight, and choosing an obstacle-free field, landing into the wind, is the ideal choice. However, determining which obstacles lurk below at night may not be possible. Use your best judgment during the evaluation phase, and concentrate on flying the airplane, maintaining airspeed and airplane control on final. A sparsely lit two-lane road may look suitable, but remember the hidden hazards of telephone and electrical poles and wires bordering or crossing the road.
En route, if you see a red wingtip position light, it's on the right of the other aircraft and the traffic is approaching. Diverging traffic would show the opposite, and you would also see the white aft position light.
Approaching your destination airport, the tower may not be operating during the midnight hours, so you may need to activate the runway lighting via the com-radio-controlled pilot controlled lighting (see AIM Section 2-1-6 for more). These systems are installed at many nontowered airports as well. If you key your microphone seven times within five seconds on the designated frequency (usually CTAF or tower frequency), the highest intensity available will activate, including VASI/REIL (visual approach slope indicator/runway end identifier lights), approach lighting, and all runway and taxiway lights. Five times within five seconds yields medium intensity, and three times within five seconds activates the lights at low intensity. Fifteen minutes' lighting duration is now available.
The airport rotating beacons for civilian use alternate white and green. Don't confuse this with a military airport beacon that alternates white, white, and green. Your VFR night destination may have a military field nearby, so be familiar with any military operations areas along your route. (See "CFI to CFI: Blackout Dates Apply," for a discussion of military nighttime operations and GA pilots.)
Another classic "trap" during night cross-country flights occurs when there are two airports relatively nearby (within 20 nm of each other) that have similarly configured runways. Many pilots have lined up perfectly for a straight-in approach to one airport's runway only to realize that what really lies ahead is another airport 10 miles from the intended destination. Even professional pilots have made this mistake. Use standard technique when approaching an uncontrolled airport at night, circling 1,500 feet above field elevation to view the lighted wind tee or windsock if there is one, before entering the pattern. The current Airport/Facility Directory lists all of these important details about what is available at destination airports that you must incorporate into your preflight planning.
The basic flying techniques and procedures for day and night flying are essentially the same. Flying fundamentals never change. Your airplane doesn't know whether the moon is out or not, but the stage on which you are performing has a definite new look at night.
Joel Stoller is a Boeing 717 captain for Midwest Airlines. He has been a CFI for nearly 25 years, and has more than 17,000 flying hours.