Anti-collision lights during daytime.

[Capt. Geoffrey Thorpe]

OK, I will say up front, Master on, Strobe on, Fuel on, Mags on, throttle closed, choke on...

I dutifully flip the switch on every time I start the engine and assume that something good will come of it.

But, I don't recall EVER actually seeing a strobe / beacon lit up on some other airplane in flight during the day. Night, dusk, yea. If it's dark enough, they show up.

Have any of you ever actually noticed the light before you saw the airplane?

Does it really make any difference to anything (other than being in the rules)?

Or, is there some secret club that I don't know about where everyone turns off the light after takeoff?

 

[Jim Logajan]

But, I don't recall EVER actually seeing a strobe / beacon lit up on some other airplane in flight during the day.

During my PP oral exam, the issue of lights on during the day came up, and I said they weren't required but I would turn them on for flight safety. The DPE rolled his eyes and said he was part of a lengthy study on the subject several decades back (the 1960's I think) and they found lights on during the day didn't make aircraft more visible at all. Zero improvement over unlighted aircraft. He seemed adamant that it was a pointless exercise, and contrary to the claims in the AIM, there wasn't any evidence to support turning on lights during the day to enhance see-and-avoid. On the contrary, all that is accomplished is to reduce the real useful life of incandescent lights for the dark periods when you really need them. Obviously those with LED lights can turn them on to their heart's content.

 

[Jim Logajan]

A useful experiment to do during pre-flight in the sunlight is to notice how close you have to get to clearly see the position and strobe lights; walk a bit away and see whether you think they make the airplane more visible.

Consider the wording of 91.209(b) and the discretion it allows, given that needlessly burning the useful life of filaments in incandescent lamps is not always in the interest of safety. On the other hand, my understanding is that that discretion was likely put in there to cover other situations, such as strobes in fog or to avoid blinding others while on the surface at night.

 

[Jim Logajan]

Really? Start-up to shutdown? This is the first I've heard of this. I was taught transponder to STBY until immediately before takeoff to immediately after clearing the runway post-landing.

I'm aware that certain airports (i.e. BOS and PVD) have ground RADAR that requires the transponder to be left on. I was told that PVD mentions this in the ATIS. How about non-towered airports that don't have RADAR coverage on the ground anyway.

I just want to make sure I'm doing the right thing.

This is a fairly new recommendation for transponder usage - the AIM explanations of changes section indicates that document was changed February 9, 2012.

As to thread creep - the original post asked "Have any of you ever actually noticed the light before you saw the airplane?"

Instead of getting "yes" or "no" answers, people have been reporting their procedures or citing alleged authorities. I'm also guilty of not answering that question.

So - in the day I don't recall ever seeing the light before I've seen the aircraft.