Night flying has both benefit and beauty – there is usually less air traffic to contend with, and a clear night offers beautiful star-studded skies above and twinkling towns below. However, the limitations that darkness puts on human vision, along with the effects of pilot fatigue at day’s end raise the risk of night flying. Statistically, although there are not as many accidents at night as during the day, those accidents that do occur have a significantly higher fatality rate. This subject report touches on the main issues involved in night flying: The limitations of night vision, night illusions, lighting and night blindness, weather minimums, regulations, and tips for making your night flight pleasurable and safe.
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This subject report contains important information relating to night flying, and should be used to help educate and prepare for a night flight. The report covers everything from aero-medical factors surrounding night flying, to terrain avoidance procedures when flying at night. Aero-medical factors discussed range from how the eye processes decreased visible light at night, to the illusions a pilot may encounter at night. Need a refresher on the federal regulations dealing with night flying? This subject report will walk you through what is required for recency, certification, weather minimums, and much more.
As the sun sets, our familiar looking earth undergoes a full makeover. Depth and altitude perceptions are seriously altered, and visual acuity diminishes. In order to better understand night vision, let’s look at how our eyes work. They are comprised of rods and cones. Cones are responsible for our color vision, and are concentrated toward the back of the retina. Rods, on the other hand, are unable to discern color, but are very sensitive and enable us to see in the dark. Because rods are located on the outer edges of the retina, peripheral night vision is stronger than vision straight ahead, so we will see better if we look at objects off center at night, rather than straight on.
Try not to look at any bright lights 30 minutes prior to the time of your night flight. Sudden exposure to light after your eyes have adjusted to the dark can cause temporary blindness and drastically decrease your night vision. Keep this in mind when taxiing around other aircraft, as your strobe lights can ruin another pilot’s night vision. When taxiing, avoid looking directly at Runway End Identifier Lights, seen as flashing strobes at the end of some runways.
A few tips:
Once you are in the cockpit, be sure you have at least one spare flashlight, or at least spare batteries. These should be easily accessible from your position in the aircraft. Preferably the flashlight would be dimmable and/or capable of switching between white and red light. Know where all of the switches are located for both internal and external lights, and make sure your electrical system is in good condition.
These illusions that can be hazardous during night flight:
The basic VFR weather minimums of FAR 91.155 for the most part do not differentiate between night and day. It is only for operations in Class G (uncontrolled) airspace that the regulation specifies some higher minimums for night flight. The minimums in the other classes of airspace, all controlled (Classes A, B, C, D, and E), are the same, night and day.
The daytime minimums for Class G airspace (below 10,000 feet msl and above 1,200 feet above the surface) are visibility of 1 mile and clearance from clouds of 500 feet below, 1,000 feet above, and 2,000 feet horizontal. At 1,200 feet or less above the surface (regardless of msl altitude) the daytime cloud clearance minimum is "clear of clouds." That's pretty significant. At or below 1,200 feet agl in uncontrolled airspace, we can operate daytime VFR with as little as one-mile visibility and clear of clouds.
At night, the visibility minimum for uncontrolled airspace increases to three statute miles for both altitude spectrums, making it the same as in controlled airspace. The cloud clearance minimums at night, while the same as controlled airspace for operations above 1,200 feet above the surface, increase for lower altitude operations from "clear of clouds" to the same as controlled airspace, i.e., 500 feet below, 1,000 feet above, and 2,000 feet horizontal distance from clouds. So, at night, the VFR weather minimums in all uncontrolled airspace up to 10,000 feet msl are the same as controlled airspace. In other words, there are no relaxed VFR weather minimums at night in uncontrolled airspace.
The fuel requirements for flight in VFR conditions, as specified in FAR 91.151, are increased for night operations. At night, a flight under VFR conditions must begin with enough fuel to fly to the first point of intended landing, and to fly after that for at least 45 minutes assuming normal cruising speed. The daytime minimum is 30 minutes. The fuel requirement for rotorcraft VFR flight is not different for night. Day or night, the flight must begin with 20 minutes fuel reserve. As a reminder, in computing these fuel requirements a pilot must consider wind and forecast weather conditions. The fuel requirements for flight in IFR conditions are not different for night and day.
Certification rules for night flying
A specified amount of night flying is required for certification as a private or commercial pilot. For example, under FAR 61.109, an applicant for a private pilot certificate must generally (there are restrictive exceptions) have at least 3 hours of night flight training that includes a long cross-country flight and 10 takeoffs and 10 landings in a single-engine or multiengine airplane, depending on the rating sought. Under FAR 61.129, an applicant for a commercial pilot certificate has comparable night flight-training requirements and exceptions. There are similar night flight-training requirements for helicopter and other ratings. All of this night time is required to be computed with reference to the technical regulatory definition of night in FAR 1.1.
Recent experience requirements
On the other hand, here is one of the places that the definition of night is different from the FAR 1.1 definition. FAR 61.57(b) contains the recent night-flying experience requirements to carry passengers at night. The title of the regulation uses the term "night" but defines that term as the "period beginning one hour after sunset and ending one hour before sunrise." This definition is narrower. It makes the period of darkness shorter.
To refresh, the rule requires that a pilot must have made at least three takeoffs and three landings to a full stop during nighttime, as it is here narrowly defined, in order to be current to carry passengers during a nighttime period defined in the same way. The required takeoffs and landings must have been made in an aircraft of the same category, class, and type (if a type rating is required), or in an approved training center simulator adjusted to simulate night.
Night special VFR
The opportunity to operate special VFR under FAR 91.157 — that is, with lower than basic VFR weather minimums — is more restrictive at night. The term "night" does not appear in this regulation. Rather, it is implied because, according to the regulation, special VFR operations may only be conducted "between sunrise and sunset" — unless the flight meets other criteria. So, essentially it is a nighttime restriction, night being implicitly defined as the time other than "between sunrise and sunset." Unless the operation is between sunrise and sunset, a special VFR operation may not be conducted unless the aircraft is equipped for IFR flight and the pilot is IFR rated and current. During daytime special VFR operations, these IFR restrictions do not apply. The IFR restrictions do not apply to helicopters. In Alaska, the IFR restrictions apply when the sun is six degrees or more below the horizon.
Terrain avoidance is more difficult at night. Pay careful attention to the Maximum Elevation Figure (MEF) on sectional charts, which represents the highest elevation, including terrain and other vertical obstacles (towers, trees, etc.), within a quadrant. A quadrant is the area bounded by ticked lines dividing each 30 minutes of latitude and each 30 minutes of longitude. MEF figures are depicted to the nearest 100' value. The last two digits of the number are not shown. MEFs are shown over land masses as well as over open water areas containing man-made obstacles such as oil rigs. A Minimum Enroute Altitude should be picked based on the MEF and other factors such as airspace. Holding this altitude will keep you, your passengers, and your plane safe during night flights, when seeing the ground is often difficult, and in some cases not possible.