Quote:
Originally Posted by N121PP
While flying at night, I have always wondered what purpose the lights on the wings really serve? Is it like the headlights on a car? I have noticed they are not turned on until right before takeoff and on final approach. Do they somehow help the pilots see? I also noticed they are turned off for taxiing.
There are several different sets of lights on an airplane:
• Nav lights
• Taxi lights
• Landing lights
• Wing illumination lights (aka ice observe lights)
• Strobe lights
The Nav lights are customarily left on at all times, even at the gate. These are the wingtip lights (red on the left wing; green on the right wing) and a white light on the tail. These help in determining the direction of flight of another plane. If the red light is on the right, the plane is coming at you. I've heard a few mnemonics for this: "Red, Right, Returning" or "Red, Right, Wrong" (i.e. coming at you).
Taxi lights are used any time we are moving on the ground. Although useful at night for illuminating the taxiway, the main reason we use them is to make us more visible to other aircraft. If we're at a stop on the ground, the taxi lights are turned off...a clear signal to everyone (including ground traffic such as baggage carts and fuel trucks) that we're not moving. Before moving again, we turn them on and this alerts anyone around that we're getting ready to move.
Ice observe lights illuminate the wing surface and can be used to check for ice build-up.
Strobe lights are used from take-off until exiting the runway after landing. They are sometimes turned off when flying in clouds at night as they can become distracting and disorienting.
When we take the runway for takeoff, all lights are turned on for maximum visibility (including ice observe lights) and kept on until we reach 18,000'. They make a huge difference, even during daylight. On many planes the landing lights are on the nose gear, so after gear retraction they aren't illuminating anything.
The reason we use 18,000' is because this is the base of Positive Control Airspace within the U.S. Once above that altitude, all other aircraft are on instrument flight plans and there should be no rogue VFR traffic. We will sometimes flash the lights above 18,000 if ATC calls converging traffic...kind of a friendly "hello" to the passing traffic.
We can taxi safely without the taxi lights. All taxiways have blue edge lighting, which is adequate for maintaining position, and at bigger airports the taxiways have green centerline lighting. We could also takeoff and land without lights of any kind. The runway edge (and sometimes centerline) lights provide guidance for takeoff and perspective for landing.
Quote:
Originally Posted by chiglet
In the UK at least, I believe it's mandatory for aircraft to keep landing lights on in the climb out until above FL100 (or something like that). I'm sure OP will have done a few departures from the UK in darkness so can correct me.
Outside the U.S., the altitude for Positive Control Airspace varies. I've seen ranges from 3000' on up to 18,000', depending on the country. Most European countries have a PCA floor of around 6000', give or take a thousand or so. I'm not aware of any specific country's lighting requirements, but our custom of keeping all lights on below 18,000' satisfies even the most restrictive.