… who remembers them?
This afternoon I was supposed to go flying with a student in a Pa44. The weather was awful but flyable, maybe some icing to be expected above 5000ft, but it was warm enough on the ground for a safe operation. We had been warned that the heater of the aircraft might still be unserviceable (it was when I last flew the plane 5 days ago – but then it was almost 10 degrees C warmer than today) so while my student was setting up her navaids, I tried to get the heater going. Successfully, so all looked good. We still had some trouble taxiing out in the rain as the weak heater was not really able to defog the windshield. After the run-up at the holding point, we got an alternator warning light and both ammeters read zero. All combinations of switch settings and CB resetting didn’t fix it, so we had to call the flight off. Tower cleared us to taxi back home along the runway, the radio already started to crackle. We made it safely home and the tower controller told us: “Since your afternoon is already wasted, you might as well visit us in the tower” (my student is very nervous on the radio, apologises all the time when she reads back something wrongly, and I guess he did that to show her that controllers are just normal people no one needs to be afraid of).
So we went to see the tower (I hadn’t myself been there for quite some time). We were given a very comprehensive tour of all the stations, met some very nice people (the oldest one is half my age and one of the girls I already knew as she is the wife of one of my former first officers) and then I saw the new light gun they had received only a few days ago. With LEDs. Very smart, no spiral cable hanging from the ceiling required any more. Steady, blinking, red, green white. Must have cost more than my car. And guess what? To the side they had taped a piece of paper showing the meaning of the different light codes – we pilots are not the only ones who can’t remember 
Nice story. Should remind us that a visit to the tower should be part of any PPL training. Outside of busy hours of course.
After a new tower was built, with greenish glass, a Cub with radio problems was given a red light, without ATC opening the window. The pilot had difficulty making out the colour, but decided it was green. 
Interesting … several Croatian airports received new light guns recently – it’s probably technology upgrade.
what_next wrote:
… who remembers them?
Like most things in life, it is better to understand the logic behind the signals rather than rote learning…
Fairly obviously Red = bad, Green = good…
Solid is reserved for more critical commands like Cleared to land….because it is less reliable / certain to be able to pass a solid light signal (vs an intermittent signal), solid green is reserved for a Clearance to land….if for some reason the guy holding the light gets a sneezing fit or otherwise interrupts the solid light the result is Safer…. ie join the circuit and await clearance…
Similarly solid red means continue holding away from the circuit and await green…if a sneezing fit ensues the result is Safer (for the airfield) in the sense that you will interpret it as Go Away and find somewhere else to land..
For my skill test for PPL in 1992, my examiner wanted to see if I could land using the lights. He called the tower and requested the light approach, but we saw no lights. A short while after he called by radio again, and the ATC said he was using the light. We just continued by radio. It turned out the light system was defunct, it haven’t been used for ages (if ever at all at ENKB, the airport was opened in 1970).
Notes are always a good idea. This is LGMT TWR light gun. I have used it once, it works.
Green: OK
Red: not OK
like the traffic lights.
