Interesting thing with transponders

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

Hi Jim,

If you are arguing against the use of transponders - I must wholeheartedly
disagree. I think they are the best investment you can make it the safety
of your aircraft, and many of the other aircraft sharing the airspace with
you - including passenger jets.

I suppose I could be accused of being biased because I sell transponders.
But my feelings are sincere. I hope that a lot more gliders will put
transponders in their gliders in the future. Very few gliders in here MN
have them - and my gliderport is located in a notch (cutout) of the Class B
airspace. We see a lot of passenger airline traffic. But they probably
don't see us.

Best Regards,

Paul Remde

"JS" wrote in message
...
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

On Mar 5, 2:54*pm, JS wrote:

* 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

What gives you the idea that military planes do not use transponders?
All US (and probably most of the rest of the worlds) military aircraft
have transponders and are required to use them when out of restricted
airspace - mil flights are usually on an IFR flight plan with a
specific assigned Mode 3 squawk until they are in their exercise
airspace and can cancel - and then usually will leave one or modes on
(typically, a USAF jet has modes 1, 2, 3, C, 4, and S).

In addition, fighters can interrogate and detect other transponders
(think super-TCAS), while transports probably all have TCAS or
equivalent - remember, most airspace is not owned by the military, so
we have to share!

Where you can have a problem is with military aircraft on LLTRs - they
may be too low to detect your transponder until too late - so know
where the local LLTRs are and be careful near them. Same for active
MOAs - worth a check with center to find out if a MOA is hot - lots of
Guard and Reserve units train on weekends.

Looking out the window, of course, is always a good thing!

Cheers,

Kirk
66

Forgive me. Most of my flying is in MOAs, so I treat it all as such.
This briefing was for flights in the R-2508 Complex, the collection
of Restricted and Military airspace surrounding Edwards Air Force Base
and China Lake Naval Air Station. It makes up a good percentage of the
southern California task area, regularly used by gliders from Nevada
and California. The complex extends from surface to unlimited.
Thinking of the alternative, I don't mind hearing ATC warning
someone that there's a glider maneuvering at their altitude, 12:00, 5
miles. Had assumed that other than current draw there wasn't a down
side to a certified transponder installation, but an alarm going off
at ATC for no apparent reason is something to be aware of.
Your mileage may vary.
Jim
If you're unfamiliar with the R2508 Complex, and care to have a
look...
http://www.edwards.af.mil/r-2508.asp

If they want us to use transponders.. then they have to put up with the 1200
codes (or discrete glider code) all over their screens.

As Jim said... but not entirely accurate. And a response by another
responder, not entirely accurate.
Yes, if a "discrete" assigned code gets to close to another discrete or 1200
code, alarms go off.
If two 1200 codes get too close, alarms do not necessarily go off, 1200
(VFR) codes implies that the controller does not have the aircraft on the
radio frequency and there is nothing the controller could do about it.

"Most" fighter type aircraft can interrogate Mode 3 transponders on their
air to air search radars and get a return.
"Most" fighter type aircraft do not have TCAS. Modern Aircraft might.
"Transport" military aircraft may or may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a transponder.
" Heavy Bomber" military aircraft may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a transponder.

If a flight of 4 fighters (or more than one) is transitioning airspace
outside of a MOA, ATC will have the wingmen, "Strangle the parrot", so
everyone will only see one transponder return, not four and the ATC radar
will not "go crazy with alerts".

BT "retired military aviator" and one time ATC controller.

"JS" wrote in message
...
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

JS wrote:
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!
No "havoc" is created by two transponders sqawking 1200 near each other.
It can cause signal scrambling problems so the Mode C altitude data is
not read reliably, but ATC still knows where you are! Mode S
transponders can alleviate this problem.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

" No "havoc" is created by two transponders sqawking 1200 near each
other."

Tell that to the Dutch who fly in the Schiphol area...

BT wrote:
/snip/
"Transport" military aircraft may or may not have TCAS, it depends on
their vintage, and they do not have an air to air radar to "ping" a
transponder.
" Heavy Bomber" military aircraft may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a
transponder.
/snip/

BT "retired military aviator" and one time ATC controller.

I know the C-5 has TCAS. It uses squitter mode and interrogates
transponders.
The KC-135 has TCAS. I am almost certain it too interrogates.
(I should know this, but I did not update the transponder model for
the KC-135 simulators, and cannot recall. Military aircraft are subject
to continuous performance updates.)

Brian W

I find the assertion that military aircraft do not have transponders humorous. Wasn't it the military that developed the system back in WWII? Isn't our current system a direct descendant of the original IFF (http://en.wikipedia.org/wiki/Identif..._friend_or_foe) and still uses to original coding system? ("Squawk 1200, etc.)



BTW, I am alive today because of the refusal to allow the USS Long Beach to blindly fire on an aircraft from which it was not receiving a transponder signal. The aircraft in question turned out to be my A-6A Intruder with an inoperative transponder.





"brian whatcott" wrote in message ...

BT wrote:
/snip/
"Transport" military aircraft may or may not have TCAS, it depends on
their vintage, and they do not have an air to air radar to "ping" a
transponder.
" Heavy Bomber" military aircraft may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a
transponder.
/snip/

BT "retired military aviator" and one time ATC controller.

I know the C-5 has TCAS. It uses squitter mode and interrogates
transponders.
The KC-135 has TCAS. I am almost certain it too interrogates.
(I should know this, but I did not update the transponder model for
the KC-135 simulators, and cannot recall. Military aircraft are subject
to continuous performance updates.)

Brian W

On Mar 6, 8:01*am, "Wayne Paul" wrote:
I find the assertion that military aircraft do not have transponders humorous. *Wasn't it the military that developed the system back in WWII? *Isn't our current system a direct descendant of the original IFF (http://en..wikipedia.org/wiki/Identi..._friend_or_foe) and still uses to original coding system? ("Squawk 1200, etc.)

BTW, I am alive today because of the refusal to allow the USS Long Beach to blindly fire on an aircraft from which it was not receiving a transponder signal. *The aircraft in question turned out to be my A-6A Intruder with an inoperative transponder.

"brian whatcott" wrote in ...

BT wrote:
/snip/
"Transport" military aircraft may or may not have TCAS, it depends on
their vintage, and they do not have an air to air radar to "ping" a
transponder.
" Heavy Bomber" military aircraft may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a
transponder.
/snip/

BT "retired military aviator" and one time ATC controller.

I know the C-5 has TCAS. It uses squitter mode and interrogates
transponders.
The KC-135 has TCAS. I am almost certain it too interrogates.
*(I should know this, but I did not update the transponder model for
the KC-135 simulators, and cannot recall. Military aircraft are subject
to continuous performance updates.)

Brian W

You're lucky. I was on the heavy cruiser USS St. Paul watching when
the missile cruiser USS Canberra blasted an AD5 Skyraider out of the
sky with a missile because of an inoperative transponder. The 4-man
A5 crew was lost.

Back to the basic transponder discussion.

It's obvious the US air traffic control system is based on a military
command structure. All information is kicked up the chain of command
for a decision while the ops people at the bottom wait for an answer.
The oxymoron "Military Intelligence" applies.

In a similar way, information on potential air-to-air conflicts is
collected at a 'control center' then, if the situation is deemed
important, the pilots of the conflicted aircraft are notified. The
system assumes a perfect two-way information flow. When closing
speeds exceed 1000 kts, this is a profoundly stupid situation.

I can see no reason why a bunch of civil servants in a concrete bunker
need to know about a potential conflict hundreds of miles away. The
people who need to know are the pilots involved. The pilots have the
most at risk and are the only people in a position to use the
information to save themselves and their passengers. "Controllers"
can talk all they want but the flight paths won't diverge until the
pilots hands move the controls. This is why FLARM and TCAS are so
successful.

It's clear to anyone who understands ADS-B that it undermines the
'central control' idea by providing timely information to pilots thus
putting ground jobs at risk. The painfully slow adoption of ADS-B is
best seen as a labor relations issue.