Flying at night under the stars is an amazing experience, particularly on a clear and cloudless night, which allows for VFR night flying. Winds are generally calmer and there’s far less traffic in your airspace than during the day.
Many countries do however not permit night flying under Visual Flight Rules (VFR). All flights are then conducted under Instrument Flight Rules (IFR) and a pilot needs to be instrument rated to conduct any flight or part thereof between 15 minutes after sunset and 15 minutes before sunrise.
The reason is safety. Night flying under VFR comes with a set of additional risks compared to flying during day time. A competent pilot should be aware of these risks and make sure adequate safety precautions are applied.
In South Africa night flying under VFR is allowed and he has recently been out there on a VFR night flight to enjoy the beauty of the land under the African night sky. Here are some considerations, he thinks, a pilot should be aware of when heading out there on a VFR flight at night.
Physiological factors
There are a couple human factors which make night flying different from day flying. The reason is simple, it’s dark at night.
Darkness means that everything that is not lit, is black! That includes the ground, a mountain, the sky, the horizon etc. It is all pitch dark and with no recognizable visual difference between them. Unless its full moon or near full moon.
The central part of our eyes and vision recognizes colors, but not light. Only the peripheral part of our eyes, which contains the rods can recognize light. So, if everything is dark, there is no color, and hence you cannot effectively recognize an object with your central vision. To recognize an object, such as another aircraft’s navigation lights, at night, you have to look at it slightly off center. Trying to identify an object at night by looking straight at it, is a bad strategy. You won’t see that mast, hill or tower straight ahead of you if its not well-lit.
Our depth perception is also dependent on peripheral vision. If everything around is dark, you don’t know how high above the ground you are. Your only visual cues during an approach and landing are your runway threshold, -end and -center lights. To be safe, you should thus use your altimeter to cross check!
Illusions
The first important illusion, which may occur during night at an airfield with dim or weak lightning is the “black hole effect”.
Because as said above, at night everything is dark. That means there’s no visible horizon which separates the ground from the sky. Consequently you have limited to no depth perception during your approach. That leads to pilots tending to approach the runway at a far lower altitude than they believe they are. With the possibly fatal consequence of controlled flight into terrain (CFIT). That is flying a perfectly flyable aircraft into some part of the earth’s surface, without seeing it. Life is certainly better without such an experience.
Another common illusion during night is a “false horizon”. Because there’s no visible horizon it’s very easy to confuse the light of a star with the light of a house on the ground, or vice versa. That may lead you to think you are flying in level flight, whilst in fact you fly with a bank angle. A situation which tends to have similarly unhealthy consequences like a loss of situational awareness due to the black hole effect.
The best remediation in both cases is to use your instruments to cross check your flight attitude and altitude. You don’t have to be instrument rated to use the instruments of your aircraft. Even if you are flying under the rules of visual flight, use your instruments. It’s definitely safer.
Operational considerations
Instrument settings
If you are flying into a remote unmanned airfield at night, there won’t be an air traffic controller who can provide you with the local pressure setting (QNH) for your altimeter. The prevailing pressure is more than likely different from your departure aerodrome. That means your altimeter does not indicate your true altitude. Whatever setting you chose, it’s merely a guess and you might be higher or lower than what the instrument indicates to you.
The same applies to temperature. There won’t be anyone who can advise you what the local temperature is. At night temperatures can be lower than standard atmosphere to which your altimeter is calibrated, and it will over-read, i.e. you are lower than what the instrument is indicating.
He recommends to consult the QNH charts for the area you want to fly to before departure, and check any weather reports for forecasted temperatures. It’s then still guess work to set your altimeter, but at least it’s an informed guess.
Then fly the approach with a reasonable safety margin to compensate for altimeter reading errors. Try to reach the threshold of the runway at a safe indicated altitude taking the length of the available landing distance of the runway into account. A target spot landing at the threshold at night on a poorly lit airfield can easily go wrong.
Runway lightning
It is also advisable to check the runway lightning system available at your destination airport in your planning. Large airports with precision instrument approaches have strong and extended lightning facilities. Remote airfields don’t. Lights are often weak and dim to an extent that they are hard to identify from the air.
Also keep in mind that some lights are designed in such a manner that they are only identifiable from a certain direction. For example, runway threshold lights or -end lights only appear green or red when you approach them. When you fly towards them at a 90 degree angle, you won’t see them. So don’t try to find a green or red light from the air when approaching the runway from an angle. You won’t find it.
Situational awareness
Situational awareness is your life saver, at night in particular. You can easily lose situational awareness at night due to the illusions discussed above. There might be no lit objects around your airfield such as houses, roads etc. and the runway lights might be dim. You won’t know how high you are above the ground when approaching, unless it’s full or nearly full moon.
If you are familiar with instrument flying, check if there is an instrument approach plate available for your intended aerodrome of landing. Also check if the relevant navigation facility if serviceable. Otherwise that plate is of little use.
If all is available, then fly the instrument approach procedure even under a VFR flight plan. It keeps you in protected areas until you should be able to see that runway ahead of you.
What is equally important is situational awareness in terms of other potential traffic around you. It’s not easy to spot the navigation lights of another aircraft when there are stars and lit objects on the ground. In the video below it’s easy to spot the other aircraft, because your are looking at a lit screen (and if you don’t see it in the video, then don’t fly at night). In real flight, you will only see it in your peripheral vision or looking at it off center. Remember, your central vision doesn’t recognize any light.
Make sure you are on the correct radio frequency, make sure you are aware of the position and direction of other traffic relative to your own, and communicate with others where you are and what you intend to do. It’s teamwork up there, in the interest of everyone.
Lastly, any respected pilot should appreciate the men and women who paint runway and taxiway markings. They don’t paint for fun or aesthetic purposes. They paint for our safety. One good way to show appreciation is to stick to those markings even at daytime, when you need them less than at night. Good airmanship is an honorable thing to do.