The 4509 and Q4509 have the same power requirement and should be
interchangeable. Did you check the Q4509 bulb to make sure that you
did not get a bad one? There is no reason that Q4509 can not be used
in place of 4509.

The lights that burned out on me were both regular GE 4509s that came
with the Skycraft kit. I've replaced one of them with the Q4509 (that
I ordered from Spruce, before I knew the second light was going to burn
out, too), and the other with a regular "NAPA" 4509 bulb, which I
bought when the second original 4509 burned out.

I've not burned out a Q4509 in a very long time. (The nose-light --
now rarely used -- is a Q4509, and it's been in there for, well, I
can't remember how long.)

Yes, I have read seen reports that one can use NAPA's tractor bulb
equivalent but since the Galaxy 4509 is even cheaper than autopart
store price, why bother?

Well, the one I bought at NAPA is not a tractor light -- it says
"aircraft bulb" on the box -- but I sure do like your price better.

I wonder where the Galaxy bulb is made? (Both the GE and NAPA/Wagner
lights are made in the USA.) I'll bet it's Chinese, to be SO much
cheaper.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"