This morning's threads about transponders and collisions prompted...
During the trip to Joshua Approach which Cindy Brickner organised
last week, amongst other things we were presented with what happens at
the Air Traffic Control end when we are sending our location to them
via transponder.
If you are issued a discrete squawk code by ATC, and fly close to
another aircraft with a transponder; turned on and ALT encoding,
discrete or VFR (1200) code; then ATC computers start making noise
about the possible crash. They can only suppress so much of this
before the warnings sound like "something out of Star Wars".
Apparently two aircraft squawking VFR are visually reported as a
conflict but do not have the same level of alert.
Close to another aircraft could be:
On tow behind a transponder-equipped towplane.
Sharing a thermal.
Pair flying.
Not that gliders ever do any of that.
So as we're all moving toward using radios and transponders to keep
separation, be aware of the havoc we may be wreaking at ATC. Not a
good way to make friends! If you're Mode S, they have your
registration too!
As previously suspected, military aircraft do not use transponders,
so they get your position verbally from ATC but your current
transponder-based collision warning systems will do nothing.
Look out the window,
Jim