Interesting thing with transponders

[JS]

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

[Paul Remde]

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
>

[kirk.stant]

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

[JS]

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

[BT[_3_]]

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
>

[Eric Greenwell]

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)

[Hagbard Celine]

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

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

[Brian Whatcott]

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

[Wayne Paul]

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/Identification_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
>

[bildan]

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/Identification_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.

[Darryl Ramm]

On Mar 5, 10:04*pm, Hagbard Celine > wrote:
> " No "havoc" is created by two transponders sqawking 1200 near each
> other."
>
> Tell that to the Dutch who fly in the Schiphol area...

Shiphol had a problem with the back-end processing and display of Mode
S derived traffic data on their display screens. In hindsight this
seems an awfully obvious thing they missed with Mode S transponder
mandates.

Some summary to the problem is at

http://eurocontrol.int/msa/public/standard_page/Schiphol_Transponder_Procedure.html

Transponders provide visibility for gliders to both ATC and airliner/
fast jets TCAS and are therefore a critical item anywhere we are
mixing those types of aircraft. And I fail to see how a particular
display capacity/planning problem at Shiphol is that relevant to any
general idea of carriage of transponders.

Darryl

[Darryl Ramm]

On Mar 5, 3:57*pm, JS > wrote:
> 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

Jim

I'm still completely missing the point of your post.

If two gliders are squakwing 1200 they will set of a relatively low-
intensity traffic warning. The controllers should be used to this
happening a lot with GA and (for your area) glider traffic. If both
aircraft are squawking 1200 the controllers likely can't even talk to
the pilots involved. Is anybody suggesting they would rather not have
transponders that enable them to "see" gliders and therefore be able
to route military traffic around them?

If either aircraft is squawking something other than 1200 then it is
on a flight plan or flight following and the controller should want to
know about the alert. If they don't I'd really like to know why.

If a glider contacts approach and requests flight following or similar
and they are flying in formation or close to other gliders it is
common sense for them to alert the controller there are other gliders
in the close proximity (whether they are transponder equipped or not).
You should talk to the controllers about the procedures they want you
to use in those circumstances.

If you are in close truly close formation (which might happen in some
buddy flying) ATC may prefer you to deactivate the transponder on all
but one aircraft in the formation. This helps avoid false alerts and
avoids the Mode-C synchronous garbing issue that Eric alluded to. The
procedure is described in the AIM. This is not something that glider
flights, even buddy fights, would normally do. But again if there are
false alert issues with your local control facility talk to them about
when, if ever, they would want you to use this.

Darryl

[JS]

On Mar 6, 11:47 am, Darryl Ramm > wrote:
> If you are in close truly close formation (which might happen in some
> buddy flying) ATC may prefer you to deactivate the transponder on all
> but one aircraft in the formation.

Correct, that is what was suggested by ATC... Especially if a glider
has been issued a discrete code. If the glider is on the discrete code
during tow, turn the transponder in the towplane to Standby until the
glider releases. All but one glider in the thermal or group flight
turns their transponder to SBY.
(Think of what these standby transponders do for PCAS use.)

The point of my initial post is that there is a lot more to using a
transponder in an aircraft that is routinely maneuvered close to other
aircraft than first meets the eye!
And keep looking out the window.
Jim

[Darryl Ramm]

On Mar 6, 4:32*pm, JS > wrote:
> On Mar 6, 11:47 am, Darryl Ramm > wrote:
>
> > If you are in close truly close formation (which might happen in some
> > buddy flying) ATC may prefer you to deactivate the transponder on all
> > but one aircraft in the formation.
>
> * Correct, that is what was suggested by ATC... Especially if a glider
> has been issued a discrete code. If the glider is on the discrete code
> during tow, turn the transponder in the towplane to Standby until the
> glider releases. All but one glider in the thermal or group flight
> turns their transponder to SBY.
> (Think of what these standby transponders do for PCAS use.)

Jim

Sorry but I'm not following the last part of the comment either about
"standby transponders" or at least I am not follwoing if you are
thinking this is a problem or not. Once off tow both transponders
would be on and the PCAS system should operate normally. While on tow
a PCAS unit like the Zaon MRX in the glider squawking standby might
think the towplane's transponder is its own and supress the tow plane
as a threat. I'd argue that is not a problem and actually what you
want--you want the PCAS to suppress the alert and while on tow you
know where the tow plane is (I hope!). And that allows any other
threats coming close to be warned about. Experience from people who
fly with a PCAS in their glider without a transponder (or transponder
in standby) with a tow plane with a transponder would be interesting.

I think it is absolutely the wrong advice to say that gliders should
be turning off and on their transponders without coordinating this
with ATC. That seriously cannot be what ATC wants? For example in
discussions of this with Reno approach, they want this only for close
formation flights (i.e not typical glider flights) and only when those
flights have contacted Reno approach and advised that it is a flight
of multiple aircraft with leader squawking.

The advice to turn off transponders when in thermals just seems
impractical and dangerous, let alone a violation of FARs. You want
people to do this if the other gliders are squawking 1200 or if they
are assigned a discrete code? How do you know they are on a discrete
code or not? Who decides who turns off a transponder and who turn one
on and when. Is this radio chatter going to happen over the approach
frequency?

If a tow plane contacts approach for flight following then they need
to let approach know it is a tow/formation flight with glider
squawking standby--so the controller is not surprised when the glider
pops up on his radar.

Pilots also should not be trying to docuble-guess the decorrelation
capability of TCAS interrogators. i.e. Even with just Mode-C equipped
threats a TCAS equipped aircraft can see multiple aircraft even if
their signals overlap a fair amount. You don't want to be thinking you
are turning off your tranpodner might be helping ATC and then make you
invisible to TCAS that could otherwise "see" you. Especially since
TCAS-II issues vertical resolution advisories there is a risk a TCAS-
II could issue an RA that would fly the aircraft straight into you as
it tries to avoid a gilder in the thermal that is above or below you
with its transponder on. (I'm not talking about the case of a thermal
stacked with many tens of gliders with Mode-C transponders, there have
been some studies of the problem of transponder synchronous garbling
in those cases). BTW if any of those gliders have a Mode-S transponder
like the Trig TT-21 then this avoids the Mode-C synchronous garbling
issues and TCAS and ATC are capable of unambiguously seeing a
relatively large number of individual threats in the same proximity.

Bottom line. I would hope people turn on the transponder and leave it
on unless they are using flight following for a formation/tow flight
and if so then talk to the local ATC facility about how they want to
handle the radio procedures. I know there are battery concerns, but
turning off for long periods to save battery power is different (but
also a violation of FARs), and I'd hope with modern transponders this
is really a not a requirement.


Darryl

[Darryl Ramm]

On Mar 6, 6:31*am, brian whatcott > wrote:
> 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

All USAF C5 an KC-10 have TCAS-II/ETCAS (military variant). I
occasionally get to share airspace with KC-10s out of Travis AFB and
glad they have TCAS-II and I have a transponder (and I'm usually on
flight following with Travis approach if close to Travis).

I believe all KC-135s got TCAS-II/ETCAS in the Pacer/CRAG upgrade
program starting back last decade. Maybe some initially got only TCAS-
I.

C-130s have TCAS. And so on. I think the general assumption today
should be that military transport aircraft have TCAS-II. Outside
tactical exercises I expect those TCAS systems to be operating. When
operating normally all these system will interrogate mode C and S
transponders independent of ground radar or other interrogators.

Darryl

[Eric Greenwell]

bildan wrote:
> 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?
>> "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.
>>>
>>>> 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.
That's not the case in eastern Washington State, which has a lot of C17s
running around. The tower at Grant County informs them of potential
conflicts in their area, though nowadays, most/all have TCAS and aren't
dependent on the tower for timely information.

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

[JS]

I must have been hallucinating during the briefing at Joshua approach.
Time to give up.
Jim

[kirk.stant]

On Mar 5, 9:41*pm, "BT" > wrote:
As Jim said... but not entirely accurate. And a response by another
> responder, not entirely accurate.

> "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.

Well, yes. A-10s, T-38s, T-45s don't have radars so can't interrogate
(although the latter two may have TCAS - I would hope they do!).
Early F-16s and F-18s didn't have interrogators, but all the later
versions do, as do all F-15s, etc. While fighters do not have TCAS,
I think a lot of trainers do, for obvious operational safety reasons.

Plus, there is Link 16, which lets each fighter in a flight see what
the rest is seeing, and what AWACS is seeing - another way to detect
other aircraft.

But that is just gravy - the important point here is that military
aircraft operating in joint use airspace WILL have a transponder on -
so flight following should work - talk to center if you are going
through a MOA that is hot!! - and if all else fails and you see a
problem developing in a MOA between gliders and military aircraft -
call on Guard (121.5) and they will likely hear you - beats a midair
anyday and you get to talk to your tax money at work, literally.

Kirk
"retired military aviator" and one time interrogator of civilian
transponder traffic in MOAs from the pit of his F-4 (and that was 30
years ago!)

[kirk.stant]

On Mar 7, 10:57*am, JS > wrote:
> I must have been hallucinating during the briefing at Joshua approach.
> Time to give up.
> Jim

Jim, I'd be really interested to hear what what is being said in the
Joshua approach briefing. It could be a misunderstanding, or an
actual lack of knowledge between agencies and users on each other's
capabilities - not the first time that has happened.

Has there been a reciprocal briefing of glider operations and
capabilities to Center and AF personnel?

I know when I've worked with the AF on similar issues in the Luke area
(coordinating for regional contest, which would be transiting hot MOAs
during the week), there were often misconceptions (!!) that had to be
cleared up, on both sides.

Cheers,

Kirk
66

[[email protected]]

On Mar 6, 8:46*pm, Darryl Ramm > wrote:
> On Mar 6, 4:32*pm, JS > wrote:
>
> > On Mar 6, 11:47 am, Darryl Ramm > wrote:
>
> > > If you are in close truly close formation (which might happen in some
> > > buddy flying) ATC may prefer you to deactivate the transponder on all
> > > but one aircraft in the formation.
>
> > * Correct, that is what was suggested by ATC... Especially if a glider
> > has been issued a discrete code. If the glider is on the discrete code
> > during tow, turn the transponder in the towplane to Standby until the
> > glider releases. All but one glider in the thermal or group flight
> > turns their transponder to SBY.
> > (Think of what these standby transponders do for PCAS use.)
>
> Jim
>
> Sorry but I'm not following the last part of the comment either about
> "standby transponders" or at least I am not follwoing if you are
> thinking this is a problem or not. Once off tow both transponders
> would be on and the PCAS system should operate normally. While on tow
> a PCAS unit like theZaonMRXin the glider squawking standby might
> think the towplane's transponder is its own and supress the tow plane
> as a threat. I'd argue that is not a *problem and actually what you
> want--you want the PCAS to suppress the alert and while on tow you
> know where the tow plane is (I hope!). And that allows any other
> threats coming close to be warned about. Experience from people who
> fly with a PCAS in their glider without a transponder (or transponder
> in standby) with a tow plane with a transponder would be interesting.
>
> I think it is absolutely the wrong advice to say that gliders should
> be turning off and on their transponders without coordinating this
> with ATC. That seriously cannot be what ATC wants? For example in
> discussions of this with Reno approach, they want this only for close
> formation flights (i.e not typical glider flights) and only when those
> flights have contacted Reno approach and advised that it is a flight
> of multiple aircraft with leader squawking.
>
> The advice to turn off transponders when in thermals just seems
> impractical and dangerous, let alone a violation of FARs. You want
> people to do this if the other gliders are squawking 1200 or if they
> are assigned a discrete code? How do you know they are on a discrete
> code or not? Who decides who turns off a transponder and who turn one
> on and when. Is this radio chatter going to happen over the approach
> frequency?
>
> If a tow plane contacts approach for flight following then they need
> to let approach know it is a tow/formation flight with glider
> squawking standby--so the controller is not surprised when the glider
> pops up on his radar.
>
> Pilots also should not be trying to docuble-guess the decorrelation
> capability of TCAS interrogators. i.e. Even with just Mode-C equipped
> threats a TCAS equipped aircraft can see multiple aircraft even if
> their signals overlap a fair amount. You don't want to be thinking you
> are turning off your tranpodner might be helping ATC and then make you
> invisible to TCAS that could otherwise "see" you. Especially since
> TCAS-II issues vertical resolution advisories there is a risk a TCAS-
> II could issue an RA that would fly the aircraft straight into you as
> it tries to avoid a gilder in the thermal that is above or below you
> with its transponder on. (I'm not talking about the case of a thermal
> stacked with many tens of gliders with Mode-C transponders, there have
> been some studies of the problem of transponder synchronous garbling
> in those cases). BTW if any of those gliders have a Mode-S transponder
> like the Trig TT-21 then this avoids the Mode-C synchronous garbling
> issues and TCAS and ATC are capable of unambiguously seeing a
> relatively large number of individual threats in the same proximity.
>
> Bottom line. I would hope people turn on the transponder and leave it
> on unless they are using flight following for a formation/tow flight
> and if so then talk to the local ATC facility about how they want to
> handle the radio procedures. I know there are battery concerns, but
> turning off for long periods to save battery power is different (but
> also a violation of FARs), and I'd hope with modern transponders this
> is really a not a requirement.
>
> Darryl

I have been only loosly following this thread. I'm pretty confused at
this point, but now have specific questions.

We have a ZAON PCAS in our club glider. We are now installing a
transponder too. I understand that the PCAS will know that the
glider's own transponder is not a threat so it will filter it out.

If we tow behind a towplane which also has a transponder, what will
happen? Will the PCAS see the tow plane as a threat, and display
that? But another airplane might be on a collision course... but
the PCAS will not see that because it sees the towplane as the closest
threat?

OR..........will the PCAS think that the towplane transponder is
actually the glider's transponder since it stays at the same relative
altitiude and position? Will it filter out both the glider's
transponder and the tow planes' transponder?

Should we put the glider's transponder to "stand by" during tow? If
we do, will the PCAS then think the tow plane's transponder is really
the glider's transponder and filter it out, allowing the PCAS to see
other targets?

Should we just say "screw it" and ignore the PCAS entirely during tow?

Cookie

[Darryl Ramm]

On Mar 9, 6:31*pm, " >
wrote:
> On Mar 6, 8:46*pm, Darryl Ramm > wrote:
>
>
>
> > On Mar 6, 4:32*pm, JS > wrote:
>
> > > On Mar 6, 11:47 am, Darryl Ramm > wrote:
>
> > > > If you are in close truly close formation (which might happen in some
> > > > buddy flying) ATC may prefer you to deactivate the transponder on all
> > > > but one aircraft in the formation.
>
> > > * Correct, that is what was suggested by ATC... Especially if a glider
> > > has been issued a discrete code. If the glider is on the discrete code
> > > during tow, turn the transponder in the towplane to Standby until the
> > > glider releases. All but one glider in the thermal or group flight
> > > turns their transponder to SBY.
> > > (Think of what these standby transponders do for PCAS use.)
>
> > Jim
>
> > Sorry but I'm not following the last part of the comment either about
> > "standby transponders" or at least I am not follwoing if you are
> > thinking this is a problem or not. Once off tow both transponders
> > would be on and the PCAS system should operate normally. While on tow
> > a PCAS unit like theZaonMRXin the glider squawking standby might
> > think the towplane's transponder is its own and supress the tow plane
> > as a threat. I'd argue that is not a *problem and actually what you
> > want--you want the PCAS to suppress the alert and while on tow you
> > know where the tow plane is (I hope!). And that allows any other
> > threats coming close to be warned about. Experience from people who
> > fly with a PCAS in their glider without a transponder (or transponder
> > in standby) with a tow plane with a transponder would be interesting.
>
> > I think it is absolutely the wrong advice to say that gliders should
> > be turning off and on their transponders without coordinating this
> > with ATC. That seriously cannot be what ATC wants? For example in
> > discussions of this with Reno approach, they want this only for close
> > formation flights (i.e not typical glider flights) and only when those
> > flights have contacted Reno approach and advised that it is a flight
> > of multiple aircraft with leader squawking.
>
> > The advice to turn off transponders when in thermals just seems
> > impractical and dangerous, let alone a violation of FARs. You want
> > people to do this if the other gliders are squawking 1200 or if they
> > are assigned a discrete code? How do you know they are on a discrete
> > code or not? Who decides who turns off a transponder and who turn one
> > on and when. Is this radio chatter going to happen over the approach
> > frequency?
>
> > If a tow plane contacts approach for flight following then they need
> > to let approach know it is a tow/formation flight with glider
> > squawking standby--so the controller is not surprised when the glider
> > pops up on his radar.
>
> > Pilots also should not be trying to docuble-guess the decorrelation
> > capability of TCAS interrogators. i.e. Even with just Mode-C equipped
> > threats a TCAS equipped aircraft can see multiple aircraft even if
> > their signals overlap a fair amount. You don't want to be thinking you
> > are turning off your tranpodner might be helping ATC and then make you
> > invisible to TCAS that could otherwise "see" you. Especially since
> > TCAS-II issues vertical resolution advisories there is a risk a TCAS-
> > II could issue an RA that would fly the aircraft straight into you as
> > it tries to avoid a gilder in the thermal that is above or below you
> > with its transponder on. (I'm not talking about the case of a thermal
> > stacked with many tens of gliders with Mode-C transponders, there have
> > been some studies of the problem of transponder synchronous garbling
> > in those cases). BTW if any of those gliders have a Mode-S transponder
> > like the Trig TT-21 then this avoids the Mode-C synchronous garbling
> > issues and TCAS and ATC are capable of unambiguously seeing a
> > relatively large number of individual threats in the same proximity.
>
> > Bottom line. I would hope people turn on the transponder and leave it
> > on unless they are using flight following for a formation/tow flight
> > and if so then talk to the local ATC facility about how they want to
> > handle the radio procedures. I know there are battery concerns, but
> > turning off for long periods to save battery power is different (but
> > also a violation of FARs), and I'd hope with modern transponders this
> > is really a not a requirement.
>
> > Darryl
>
> I have been only loosly following this thread. *I'm pretty confused at
> this point, but now have specific questions.
>
> We have a ZAON PCAS in our club glider. * We are now installing a
> transponder too. *I understand that the PCAS will know that the
> glider's own transponder is not a threat so it will filter it out.
>
> If we tow behind a towplane which also has a transponder, what will
> happen? *Will the PCAS see the tow plane as a threat, and display
> that? *But another airplane might be on a collision course... * but
> the PCAS will not see that because it sees the towplane as the closest
> threat?
>
> OR..........will the PCAS think that the towplane transponder is
> actually the glider's transponder since it stays at the same relative
> altitiude and position? *Will it filter out both the glider's
> transponder and the tow planes' transponder?
>
> Should we put the glider's transponder to "stand by" during tow? *If
> we do, will the PCAS then think the tow plane's transponder is really
> the glider's transponder and filter it out, allowing the PCAS to see
> other targets?
>
> Should we just say "screw it" and ignore the PCAS entirely during tow?
>
> Cookie

Probably yes to all the above, with a big does of "it depends" like it
depends on the exact pressure altitude the Zaon reads, the relative
power it sees from the different transponders as to which of the
transponders it locks onto (or if it sees synchronous garbling).

If the Zaon thinks the tow plane is a threat it will not display other
threats. Until they become more of a threat in which case you see the
"NEW" message. It is also possible it thinks your own transponder is a
threat at times. Remember the threat algorithm is biased towards
threats at a similar altitude.

What do people who tow behind a tow plane with a Zaon MRX see (with or
without their own local transponder?) I often self launch my ASH-26E
(with Zaon MRX and transponder) so am not the right person to answer
the question.

One thing I am pretty sure on is you should not be turning on and off
transponders unless in touch with ATC. And if ATC does prefer that
talk to them about the radio and other procedures they want followed.



Darryl

[Brian Whatcott]

JS wrote:
>/snip/
> As previously suspected, military aircraft do not use transponders
/snip/

> Jim
>

???

[[email protected]]

>
> > I have been only loosly following this thread. *I'm pretty confused at
> > this point, but now have specific questions.
>
> > We have a ZAON PCAS in our club glider. * We are now installing a
> > transponder too. *I understand that the PCAS will know that the
> > glider's own transponder is not a threat so it will filter it out.
>
> > If we tow behind a towplane which also has a transponder, what will
> > happen? *Will the PCAS see the tow plane as a threat, and display
> > that? *But another airplane might be on a collision course... * but
> > the PCAS will not see that because it sees the towplane as the closest
> > threat?
>
> > OR..........will the PCAS think that the towplane transponder is
> > actually the glider's transponder since it stays at the same relative
> > altitiude and position? *Will it filter out both the glider's
> > transponder and the tow planes' transponder?
>
> > Should we put the glider's transponder to "stand by" during tow? *If
> > we do, will the PCAS then think the tow plane's transponder is really
> > the glider's transponder and filter it out, allowing the PCAS to see
> > other targets?
>
> > Should we just say "screw it" and ignore the PCAS entirely during tow?
>
> > Cookie
>
> Probably yes to all the above, with a big does of "it depends" like it
> depends on the exact pressure altitude the Zaon reads, the relative
> power it sees from the different transponders as to which of the
> transponders it locks onto (or if it sees synchronous garbling).
>
> If the Zaon thinks the tow plane is a threat it will not display other
> threats. Until they become more of a threat in which case you see the
> "NEW" message. It is also possible it thinks your own transponder is a
> threat at times. Remember the threat algorithm is biased towards
> threats at a similar altitude.
>
> What do people who tow behind a tow plane with a Zaon MRX see (with or
> without their own local transponder?) I often self launch my ASH-26E
> (with Zaon MRX and transponder) so am not the right person to answer
> the question.
>
> One thing I am pretty sure on is you should not be turning on and off
> transponders unless in touch with ATC. And if ATC does prefer that
> talk to them about the radio and other procedures they want followed.
>
> Darryl- Hide quoted text -
>
> - Show quoted text -

Thanks Darryl,

I guess in a practical sense we should just leave the transponder on
altitude and squawk 1200 during tow and the entire flight too.

Whatever the PCAS says....it says.........probably no useful PCAS
during tow........we should just ignore.

Perhaps in the future there may be some procecure agreed upon by ATC.

Cookie

[Jason Kramb]

Kirk, I was at the same tour that Jim was. The scenario was in
relationship to how a controller sees aircraft on his screen and what
alarms go off when two aircraft are near each other. Here's how I
understood it.

In general, two aircraft squawking 1200 are on VFR, not talking to the
controller, and if they get close to each other, as say a towplane and
glider might, or two gliders in the same thermal or wave might be, no
alarm goes off and the controller won't (and really can't) do anything.
He's not talking to either plane and they might not even be on his
frequency.

However, if a plane is assigned a discrete code, anytime that plane goes
near another plane, including those squawking 1200, an alarm will go off
on the controllers screen about potential collisions. Now, with
gliders, this isn't going to happen all that much. Unless another GA
plane on flight following comes nearby or a glider asks for clearance in
a wave window, I don't think that we end up with discrete squawk codes
all that often. In Cal City, there are two possible wave window
clearance dictates, and with one of them, discrete codes are not
necessarily assigned. However, in the other one, they are, and there is
the possibility that two gliders on discrete clearance codes can (and
may want to) fly near each other. This obviously will drive controllers
nuts, so it may simply be courteous to mention to the controller than
you are going to fly near each other as a flight, and switch your
transponder to standby if the controller agrees. Of course, if you
break away, notify the controller again such that he still knows where
you are.

This has nothing to do with standard VFR 1200 traffic. Nor anything to
do with the special 0440 code used in the Reno area (and which is
specially programmed into the Reno area controller's screens to behave
like a 1200 squawk). In the MOA's around Cal City, in one of the wave
window clearance, all non-1200 traffic is diverted around the window, so
the only potential conflicts are other gliders. In the other, military
traffic may use the same area as the wave window, and the military
planes may or may have the transponder data from gliders with discrete
codes (we didn't really talk about that). But military pilots probably
will end up staying away from the wave window area if they're smart once
the controller mentions that the window is active and there are gliders
in the area.

I think that summed up the brief talk had with the controller supervisor
at Joshua. Maybe someone else who was there can correct me.

Jason Kramb




On 3/7/2010 1:22 PM, kirk.stant wrote:
> On Mar 7, 10:57 am, > wrote:
>> I must have been hallucinating during the briefing at Joshua approach.
>> Time to give up.
>> Jim
>
> Jim, I'd be really interested to hear what what is being said in the
> Joshua approach briefing. It could be a misunderstanding, or an
> actual lack of knowledge between agencies and users on each other's
> capabilities - not the first time that has happened.
>
> Has there been a reciprocal briefing of glider operations and
> capabilities to Center and AF personnel?
>
> I know when I've worked with the AF on similar issues in the Luke area
> (coordinating for regional contest, which would be transiting hot MOAs
> during the week), there were often misconceptions (!!) that had to be
> cleared up, on both sides.
>
> Cheers,
>
> Kirk
> 66

[kirk.stant]

Jason,

Thanks for the explanation; that all makes sense. It would seem that
if the discrete code becomes a problem in a wave window, then a common
code (like the Reno 0440 code) would be one way for ATC to handle it -
that would still give TCAS protection for airliners, bizjets, etc.

It looks like there was some confusion about military aircraft
transponder use - bottom line: in common use (civilian and military)
airspace, military aircraft are handled just like civilian aircraft
with transponders - if IFR they are talking to center and get normal
IFR handling, if VFR (say in a MOA running low altitude intercepts)
then they are like other VFR traffic with transponders (and many with
TCAS and interrogators): They may not be talking to center (they will
be on their own freq) so having a TPAS in a glider will definitely
help, and a transponder in the glider may help the military aircraft
detect and avoid the glider.

Good conversation, all in all, IMHO.

Cheers,

KIrk
66