Hi Willit Run, on the 737 you don't need to pull one thrust lever to get the horn with landing flaps selected, if one leg is not down and locked.
Hi ASFKAP, it doesn't matter which green light...
Let's say the right main gear.
Another question, as raised by Willit Run:
if the horn and the GPWS also at 500ft remain silent, the gear is probably down and locked.
Do these two additional systems receive their inputs from the same proximity switch of the green/red lights?
How many proxy switches are installed on each leg?
Some airplanes, and all cargo airplanes, have a double set of green lights.
I've heard this secondary indicating system is connected to the Horn/GPWS system, so to the same proxys.
Is it true?