Studying for the PSTAR I see that a flashing green signal while in the circuit means "return for landing" but this is not actually defined anywhere. What does that mean?

NORDO = "is an aircraft flying without a radio"


What I was taught that this meant was ...

... because they could not communicate with you, but they wanted you to not land on this pass (interval a mess, crossing traffic, winds maybe wrong, a dozen other things that might crop up) it was more or less "the runway will be ready for you if you take another lap in the pattern." This also gives them a bit of time to get all of the other aircraft in the pattern out of the way of the aircraft in distress. (And the steady green ought to confirm that on the next pass, if all things go well).

Tower operators would rather get that aircraft who can't talk to them onto the ground. What they want to avoid in this case (again, this is what I was taught by a salty old Navy controller when I was in flight school) is that they wanted to avoid the aircraft attempting to land being "spooked" by a red light and thinking they can't land at this field. And then waving off and flying off in search of another field while still NORDO.

The green light is the 'friendly' light between choices of red and green. Put in the chief's colloquial jargon: "Flashing green lets the pilot know "the runway will be there for you when you come back for your next approach."

The Canadian Aeronautical Information Manual, which has all of the signals to include the two that are relevant to this question, can be found here.

The teaching that I got may no longer be current, but the lights shown to a NORDO airborne aircraft still mean the same thing as they did when I was taught.

Steady Green: cleared to land
Flashing Green: return to land (to be followed at the proper time by steady green)

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  • $\begingroup$ what's the practical difference between flashing green and steady red, then? $\endgroup$ – KBriggs Mar 14 at 1:36
  • $\begingroup$ You don't know what you'll see on the next pass with a steady red. I need to dig up our old flying manuals to give you anything more than that. that may take a day or two. $\endgroup$ – KorvinStarmast Mar 14 at 1:36
  • $\begingroup$ got it, thanks! $\endgroup$ – KBriggs Mar 14 at 1:37

My understanding of light gun signals was taught to me a little differently. For simplicity, I will concentrate on light gun signals for airborne aircraft only.

  • Alternating Red and Green is exercise extreme caution.
  • Steady Red is give way to other traffic. Which implies that you should stay in the pattern. But, you are not cleared to land.
  • Steady Green is a clearance to land.
  • Flashing Red is a request to leave the airport area. This would imply that you need to remain outside the traffic pattern.
  • Flashing Green is the signal in question. Based on the definitions of the other signals, this would imply that you should enter or return to the pattern. But, you are still not cleared to land until you get a Steady Green.

So to put it into a nutshell that may be easier to remember:

  • Green means approval and Red means denial.
  • Steady means for the runway and Flashing means for the pattern.
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    $\begingroup$ "Alternating Red and White" should be "Alternating Red and Green". Also note that this signal is not applicable in Canada (as the question is tagged) but does apply in the USA. $\endgroup$ – user2070305 Mar 14 at 19:01
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    $\begingroup$ @user2070305 - I thought I had edited this before. Thanks for the catch. $\endgroup$ – Dean F. Mar 14 at 19:40

The answers above are pretty much correct, but it is nice to cite sources.

Since the question is relating to studying for a PSTAR and is tagged Canada, first the Canadian sources:


Aeronautical Information Manual (Canada)

Section 4.2.11 Visual Signals - Aircraft on Ground

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4.4.7 Visual Signals - Aircraft in Flight

Table 4.3-Visual Signals for Aircraft in Flight

United States

The Canadian signals are similar, but not exactly the same, as US FAA ATC signals, so adding these for US pilots who find this question

§ 91.125 ATC light signals

§ 91.125 ATC light signals

In the Airman's Information Manual (US FAA), the signals are described in Section 4-3-13


  • Canada doesn't specify the use of alternating red/green signal
  • USA doesn't specify the use the blinking runway lights nor the firing of the red pyrotechnical light
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    $\begingroup$ In the US, to close a runway, a big “X” on the runway is used. In some areas, a large, blinking, lit up “X” is used to mark a temporary closure. $\endgroup$ – Dean F. Mar 14 at 19:49

Logically it would seem to mean to fly a circuit around the traffic pattern and watch for a steady green light on the next final approach.

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  • $\begingroup$ I'm sure some other superior answer will eventually overshadow this one, but it's a start. $\endgroup$ – quiet flyer Mar 14 at 1:17
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    $\begingroup$ @KorvinStarmast -- "I'm sure some other superior answer will eventually overshadow this one"-- as has now happened, nice job on that. $\endgroup$ – quiet flyer Mar 14 at 1:38

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