FLARM.....for good, or evil??

On Oct 28, 1:11*am, Andy wrote:
On Oct 27, 8:16*pm, Eric Greenwell wrote:





On 10/27/2010 5:33 PM, Mike Schumann wrote:

On 10/27/2010 3:48 PM, Eric Greenwell wrote:
On 10/27/2010 7:20 AM, wrote:
in "awareness mode", of course a led will indicate where the closer
glider is, but still alarms will only be triggered when a deviation
makes the collision a real possibility.

aldo cernezzi
Since the GPS accuracy is probably much poorer than 10 feet, when a
glider comes within 10 feet, I figure the FLARM should consider that a
collision, no?
I don't know what Flarm does in that case, but my guess is the
*relative* accuracy is much better than the *absolute* accuracy. If
that's true, then each glider might have position errors of much more
than 10 feet, but they'll have nearly the same errors, giving a more
accurate separation distance.

Maybe someone more familiar with GPS in this situation can jump in here
and tell us?

Even if the relative GPS position computed by each glider has 0 error,
you still have the problem that at 50 Knots, each aircraft is moving ~
75 ft / second. *With FLARM (or ADS-B) only transmitting positions
every second, you can't rely on these technologies to protect you from
random course changes that the systems can't possibly predict, if you
are in close proximity.

FLARM does more than transmit positions: it transmits the projected path
of it's glider. Here's what I understand will happen: when the pilot
makes a course change, a new path is calculated and compared to the
paths Flarm has received from nearby gliders. If this new path puts it
on a collision course with any of them, the pilot is warned
"immediately", meaning it does not have to wait one second. The new path
will be transmitted within one second, so the nearby gliders can update
the other glider's path in their database. It might actually be more
sophisticated than that, such as transmitting a new path sooner if the
amount of change is "large", but I don't know what the algorithms are.

This projected path is a key element to the system working properly.
Without it, each FLARM unit would have to calculate the path of every
nearby glider; with it, each unit only has to calculate one path - it's
own. Potentially, it could be using a much higher position rate than
once a second to calculate it's projected path. In any case, the result
is much better than you might think for a system that transmits once a
second.

Does ADS-B transmit a projected path, or just position?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

That's my understanding as well - the Flarm algorithm looks at a range
of potential paths that the glider might maneuver to and calculates
potential collisions on the basis of all potential paths within that
maneuvering envelope. *I expect within a couple of seconds the path
assumes a fair amount of potential maneuvering while over a longer
period of time it would limit extreme maneuvering assumptions to be
closer to an extrapolation of the current path/turn rate. Because it
understands your trun rate it works well in thermals.

I have not heard anything about similar capabilities for ADS-B and I
am confident that it doesn't extrapolate with a glider performance
envelope in mind, since it isn't designed explicitly for gliders. I
would think ADS-B would be particularly challenged in predicting
likely collisions in thermals - much more so than Flarm.

9B- Hide quoted text -

- Show quoted text -

I hadn't really considered how the projected flight path system works
before. But after thinking about it for a bit it has a lot of
potentional. How much the Flarm actually uses I do not know. But it
would be possible for the Flarm to actually learn the possible flight
paths for a given glider and dynamically adjust it's algorithm for
where the glider might be able to go from that. Even without that I
can see that gliders could get very close but have potential flight
paths that would make colliding impossible and as a result would not
create a collision alarm.

Brian

On Thu, 28 Oct 2010 06:53:27 -0700 (PDT), Brian
wrote:


I hadn't really considered how the projected flight path system works
before. But after thinking about it for a bit it has a lot of
potentional. How much the Flarm actually uses I do not know.

Flarm uses ONLY projected flight paths to calculate a collision
probability.

Even without that I
can see that gliders could get very close but have potential flight
paths that would make colliding impossible and as a result would not
create a collision alarm.


This is exactly how Flarm works.
Flarm doesn't care about distances - as long as Flarm doesn't detect a
potential collision cource, you can fly very close to each other
without getting a warning - even if you are circling.



Andreas

On Oct 28, 7:32*am, Andreas Maurer wrote:
On Thu, 28 Oct 2010 06:53:27 -0700 (PDT), Brian
wrote:

I hadn't really considered how the projected flight path system works
before. But after thinking about it for a bit it has a lot of
potentional. How much the Flarm actually uses I do not know.

Flarm uses ONLY projected flight paths to calculate a collision
probability.

Even without that I
can see that gliders could get very close but have potential flight
paths that would make colliding impossible and as a result would not
create a collision alarm.

This is exactly how Flarm works.
Flarm doesn't care about distances - as long as Flarm doesn't detect a
potential collision cource, you can fly very close to each other
without getting a warning - even if you are circling.

Andreas

I think that's the secret for how you make it useful in thermals - if
the system knows you are circling it can do a better job predicting
your curved flight path and potential threats along that path. I
presume that if you assume the full maneuvering envelope of each
glider you'd generate a lot of warnings, so it would make sense to
assume something more limited that strikes a balance between false
positive warnings and missing potential maneuvers that could create a
threat with little advanced notice. Think of a glider pulling up into
a thermal as a good example. I assume that Flarm does all this based
on the following explanation where an expanding projected flight path
envelope is depicted:

http://www.gliderpilot.org/Flarm-WhatDoesItDo

As to ADS-B - without some algorithm for projecting flight paths the
only warning you can realistically generate is a proximity warning.
Even warning only for declining separation distance is a crude form of
relative path prediction, just not a very useful one - particularly
for glider operations with multiple targets and circling flight.

9B

On Oct 28, 8:47 am, Andy wrote:
On Oct 28, 7:32 am, Andreas Maurer wrote:



On Thu, 28 Oct 2010 06:53:27 -0700 (PDT), Brian
wrote:

I hadn't really considered how the projected flight path system works
before. But after thinking about it for a bit it has a lot of
potentional. How much the Flarm actually uses I do not know.

Flarm uses ONLY projected flight paths to calculate a collision
probability.

Even without that I
can see that gliders could get very close but have potential flight
paths that would make colliding impossible and as a result would not
create a collision alarm.

This is exactly how Flarm works.
Flarm doesn't care about distances - as long as Flarm doesn't detect a
potential collision cource, you can fly very close to each other
without getting a warning - even if you are circling.

Andreas

I think that's the secret for how you make it useful in thermals - if
the system knows you are circling it can do a better job predicting
your curved flight path and potential threats along that path. I
presume that if you assume the full maneuvering envelope of each
glider you'd generate a lot of warnings, so it would make sense to
assume something more limited that strikes a balance between false
positive warnings and missing potential maneuvers that could create a
threat with little advanced notice. Think of a glider pulling up into
a thermal as a good example. I assume that Flarm does all this based
on the following explanation where an expanding projected flight path
envelope is depicted:

http://www.gliderpilot.org/Flarm-WhatDoesItDo

As to ADS-B - without some algorithm for projecting flight paths the
only warning you can realistically generate is a proximity warning.
Even warning only for declining separation distance is a crude form of
relative path prediction, just not a very useful one - particularly
for glider operations with multiple targets and circling flight.

9B

Just to give a flavor ADS-B data-out systems as mandated for 2020 in
the USA for power aircraft (basically where a transponder is required
today) will put out the following data

Aircraft ICAO ID (can be made anonymous for a UAT on VFR flight)
Aircraft callsign/flight number (not required for VFR flight)
Time of applicability
GPS Lattitude
GPS Longitude
GPS altitude
Airborne/on-surface status
Northbound ground velocity component while airborne (from GPS)
Eastbound ground velocity component while airborne (from GPS)
Heading while on the surface
Ground speed while on the surface
Pressure altitude
Vertical rate (may be pressure or GPS based)
GPS uncertainty/integrity (which needs information form a fancy TSO-
C145 class WAAS GPS)
Ident (equivalent to transponder ident/SPI)
Distress/Emergency status
ADS-B data-in/display capability
TCAS equipage/status

This is a simplified list and there is various other status/validity
data as well. There is also the concept in ADS-B messages of an
estimated position, and even estimated velocity. But AFAIK this is not
intended for fancy manoeuvrings predictions - it is more intended to
allow different parts of the ADS-B infrastructure to project position
or velocity updated to a single time of applicability. There is space
for future expansion and as an example there is long-term work
underway to look at an ADS-B based replacement for TCAS that could
well utilize extra data transmission than that above, but think well
post 2020 for this to actually happen. My brain hurts enough thinking
about ADS-B as is.

---

BTW my suspicion is given that the FAA currently requires a STC for
any installation for ADS-B data out that it is currently not possible
to install any ADS-B data-out system in the USA in any certified
aircraft (including gliders) that only meets a subset of the 2020
mandate requirements (ie. does not include all the stuff above). Which
I expect the FAA would also require fully TSO-C154c/DO-282B (UAT) TSO-
C166b/DO-260B (1090ES) and with the corresponding TSO-C145 level GPS.
Experimental aircraft are another question since an STC cannot apply
to them. This STC restriction hopefully is short-term as its is going
to have a chilling effect on ADS-B data-out adoption in general
aviation and gliders. Besides some more complex issues you can start
to see even simple installation concerns that are probably causing
this current STC requirement, such as squat switch/or other on-ground
detection, needs to have a single squawk code and ident button across
any installed transponder(s) and ADS-B data-out devices, ability to
transmit a distress/emergency code, ability to turn off the ADS-B
transmissions if requested, etc.

Darryl

"Darryl Ramm" wrote in message ...
On Oct 28, 8:47 am, Andy wrote:

Just to give a flavor ADS-B data-out systems as mandated for 2020 in
the USA for power aircraft (basically where a transponder is required
today) will put out the following data

Aircraft ICAO ID (can be made anonymous for a UAT on VFR flight)
Aircraft callsign/flight number (not required for VFR flight)
Time of applicability
GPS Lattitude
GPS Longitude
GPS altitude
Airborne/on-surface status
Northbound ground velocity component while airborne (from GPS)
Eastbound ground velocity component while airborne (from GPS)
Heading while on the surface
Ground speed while on the surface
Pressure altitude
Vertical rate (may be pressure or GPS based)
GPS uncertainty/integrity (which needs information form a fancy TSO-
C145 class WAAS GPS)
Ident (equivalent to transponder ident/SPI)
Distress/Emergency status
ADS-B data-in/display capability
TCAS equipage/status

This is a simplified list and there is various other status/validity
data as well. There is also the concept in ADS-B messages of an
estimated position, and even estimated velocity. But AFAIK this is not
intended for fancy manoeuvrings predictions - it is more intended to
allow different parts of the ADS-B infrastructure to project position
or velocity updated to a single time of applicability. There is space
for future expansion and as an example there is long-term work
underway to look at an ADS-B based replacement for TCAS that could
well utilize extra data transmission than that above, but think well
post 2020 for this to actually happen. My brain hurts enough thinking
about ADS-B as is.

---

BTW my suspicion is given that the FAA currently requires a STC for
any installation for ADS-B data out that it is currently not possible
to install any ADS-B data-out system in the USA in any certified
aircraft (including gliders) that only meets a subset of the 2020
mandate requirements (ie. does not include all the stuff above). Which
I expect the FAA would also require fully TSO-C154c/DO-282B (UAT) TSO-
C166b/DO-260B (1090ES) and with the corresponding TSO-C145 level GPS.
Experimental aircraft are another question since an STC cannot apply
to them. This STC restriction hopefully is short-term as its is going
to have a chilling effect on ADS-B data-out adoption in general
aviation and gliders. Besides some more complex issues you can start
to see even simple installation concerns that are probably causing
this current STC requirement, such as squat switch/or other on-ground
detection, needs to have a single squawk code and ident button across
any installed transponder(s) and ADS-B data-out devices, ability to
transmit a distress/emergency code, ability to turn off the ADS-B
transmissions if requested, etc.

Darryl

The following is not directed at any individual, it is simply an observation.

Even the old Garmin 12XL provides a lot more information in it's NMEA sentences the most of us realize. It is data output sentences are fully compliant with NMEA 0183 ver 2.0. The following link give an example of the data provided by "GPS engines" to software developer thus minimizing the amount of calculation required in display devices.
http://www8.garmin.com/support/pdf/NMEA_0183.pdf

As I watch these PowerFLARM discussion it is apparent that many assume that things provided by the GPS must be created by the FLARM software.

Let us accept the fact that the PowerFLARM is just an upgrade of previous units that have been proven effective in increasing glider flight safety.

Respectfully,
Wayne

On Oct 28, 1:40*pm, "Wayne Paul" wrote:
"Darryl Ramm" wrote in ...
On Oct 28, 8:47 am, Andy wrote:

Just to give a flavor ADS-B data-out systems as mandated for 2020 in
the USA for power aircraft (basically where a transponder is required
today) will put out the following data

Aircraft ICAO ID (can be made anonymous for a UAT on VFR flight)
Aircraft callsign/flight number (not required for VFR flight)
Time of applicability
GPS Lattitude
GPS Longitude
GPS altitude
Airborne/on-surface status
Northbound ground velocity component while airborne (from GPS)
Eastbound ground velocity component while airborne (from GPS)
Heading while on the surface
Ground speed while on the surface
Pressure altitude
Vertical rate (may be pressure or GPS based)
GPS uncertainty/integrity (which needs information form a fancy TSO-
C145 class WAAS GPS)
Ident (equivalent to transponder ident/SPI)
Distress/Emergency status
ADS-B data-in/display capability
TCAS equipage/status

This is a simplified list and there is various other status/validity
data as well. There is also the concept in ADS-B messages of an
estimated position, and even estimated velocity. But AFAIK this is not
intended for fancy manoeuvrings predictions - it is more intended to
allow different parts of the ADS-B infrastructure to project position
or velocity updated to a single time of applicability. There is space
for future expansion and as an example there is long-term work
underway to look at an ADS-B based replacement for TCAS that could
well utilize extra data transmission than that above, but think well
post 2020 for this to actually happen. My brain hurts enough thinking
about ADS-B as is.

---

BTW my suspicion is given that the FAA currently requires a STC for
any installation for ADS-B data out that it is currently not possible
to install any ADS-B data-out system in the USA in any certified
aircraft (including gliders) that only meets a subset of the 2020
mandate requirements (ie. does not include all the stuff above). Which
I expect the FAA would also require fully TSO-C154c/DO-282B (UAT) TSO-
C166b/DO-260B (1090ES) and with the corresponding TSO-C145 level GPS.
Experimental aircraft are another question since an STC cannot apply
to them. This STC restriction hopefully is short-term as its is going
to have a chilling effect on ADS-B data-out adoption in general
aviation and gliders. Besides some more complex issues you can start
to see even simple installation concerns that are probably causing
this current STC requirement, such as squat switch/or other on-ground
detection, needs to have a single squawk code and ident button across
any installed transponder(s) and ADS-B data-out devices, ability to
transmit a distress/emergency code, ability to turn off the ADS-B
transmissions if requested, etc.

Darryl

The following is not directed at any individual, it is simply an observation.

Even the old Garmin 12XL provides a lot more information in it's NMEA sentences the most of us realize. *It is data output sentences are fully compliant with NMEA 0183 ver 2.0. *The following link give an example of the data provided by "GPS engines" to software developer thus minimizing the amount of calculation required in display devices.http://www8.garmin.com/support/pdf/NMEA_0183.pdf

As I watch these PowerFLARM discussion it is apparent that many assume that things provided by the GPS must be created by the FLARM software.

Let us accept the fact that the PowerFLARM is just an upgrade of previous units that have been proven effective in increasing glider flight safety.

Respectfully,
Wayne

There have been several comment regarding the need for an STC to
install an ADS-B system in a certified aircraft.

This is not unlike the original situation with the installation of IFR
certified GPS systems, in the early 1990s. I was involved in several
installations and most of the concerns were about the placement of
antenna and the effect of spurious signals on navigation.

Today if you get an IFR GPS installed in an aircraft the manufacturer
has a detailed description of antenna placement, cable routing and
possible interaction. This data was collected during the earlier STC
period and as experience with more installations was gained, the FAA
changed the requirements from an STC to a 337, if installed in
compliance with the manufacturer's instructions.

I expect that the STC requirements for the ADS-B will follow the same
path over time.

Mike

On Oct 28, 1:54*pm, SoaringXCellence wrote:
On Oct 28, 1:40*pm, "Wayne Paul" wrote:



"Darryl Ramm" wrote in ...
On Oct 28, 8:47 am, Andy wrote:

Just to give a flavor ADS-B data-out systems as mandated for 2020 in
the USA for power aircraft (basically where a transponder is required
today) will put out the following data

Aircraft ICAO ID (can be made anonymous for a UAT on VFR flight)
Aircraft callsign/flight number (not required for VFR flight)
Time of applicability
GPS Lattitude
GPS Longitude
GPS altitude
Airborne/on-surface status
Northbound ground velocity component while airborne (from GPS)
Eastbound ground velocity component while airborne (from GPS)
Heading while on the surface
Ground speed while on the surface
Pressure altitude
Vertical rate (may be pressure or GPS based)
GPS uncertainty/integrity (which needs information form a fancy TSO-
C145 class WAAS GPS)
Ident (equivalent to transponder ident/SPI)
Distress/Emergency status
ADS-B data-in/display capability
TCAS equipage/status

This is a simplified list and there is various other status/validity
data as well. There is also the concept in ADS-B messages of an
estimated position, and even estimated velocity. But AFAIK this is not
intended for fancy manoeuvrings predictions - it is more intended to
allow different parts of the ADS-B infrastructure to project position
or velocity updated to a single time of applicability. There is space
for future expansion and as an example there is long-term work
underway to look at an ADS-B based replacement for TCAS that could
well utilize extra data transmission than that above, but think well
post 2020 for this to actually happen. My brain hurts enough thinking
about ADS-B as is.

---

BTW my suspicion is given that the FAA currently requires a STC for
any installation for ADS-B data out that it is currently not possible
to install any ADS-B data-out system in the USA in any certified
aircraft (including gliders) that only meets a subset of the 2020
mandate requirements (ie. does not include all the stuff above). Which
I expect the FAA would also require fully TSO-C154c/DO-282B (UAT) TSO-
C166b/DO-260B (1090ES) and with the corresponding TSO-C145 level GPS.
Experimental aircraft are another question since an STC cannot apply
to them. This STC restriction hopefully is short-term as its is going
to have a chilling effect on ADS-B data-out adoption in general
aviation and gliders. Besides some more complex issues you can start
to see even simple installation concerns that are probably causing
this current STC requirement, such as squat switch/or other on-ground
detection, needs to have a single squawk code and ident button across
any installed transponder(s) and ADS-B data-out devices, ability to
transmit a distress/emergency code, ability to turn off the ADS-B
transmissions if requested, etc.

Darryl

The following is not directed at any individual, it is simply an observation.

Even the old Garmin 12XL provides a lot more information in it's NMEA sentences the most of us realize. *It is data output sentences are fully compliant with NMEA 0183 ver 2.0. *The following link give an example of the data provided by "GPS engines" to software developer thus minimizing the amount of calculation required in display devices.http://www8.garmin.com/support/pdf/NMEA_0183.pdf

As I watch these PowerFLARM discussion it is apparent that many assume that things provided by the GPS must be created by the FLARM software.

Let us accept the fact that the PowerFLARM is just an upgrade of previous units that have been proven effective in increasing glider flight safety..

Respectfully,
Wayne

There have been several comment regarding the need for an STC to
install an ADS-B system in a certified aircraft.

This is not unlike the original situation with the installation of IFR
certified GPS systems, in the early 1990s. *I was involved in several
installations and most of the concerns were about the placement of
antenna and the effect of spurious signals on navigation.

Today if you get an IFR GPS installed in an aircraft the manufacturer
has a detailed description of antenna placement, cable routing and
possible interaction. *This data was collected during the earlier STC
period and as experience with more installations was gained, the FAA
changed the requirements from an STC to a 337, if installed in
compliance with the manufacturer's instructions.

I expect that the STC requirements for the ADS-B will follow the same
path over time.

Mike

Absolutely right (and antenna issues are one of the concerns with this
STC requirement as well). Its a matter of when the STC process
migrates to a 337/Field approval. Given the complexity of ADS-B I
wonder what the time frame will really be. And the FCC has stated that
clearly but the STC requirement still seems to have come as a bit of a
surprise to some developers--and maybe regulators where there are
questions if the cost of this was included in disclosures. I see no
way for now but for this to freeze a lot of adoption--but I suspect
from the FAA viewpoint it is needed. I do worry that smaller
manufacturers won't be able to develop many STCs and I am doubtful
you'll see folks willing to develop STCs for gliders. My purpose of
promoting the STC issue is just nobody seemed to be aware of it in
the glider community yet there are (a few) owners starting to look at
install of ADS-B data-out. Some of those owners have experimental
gliders and are in a better position. Those with certified gliders
need to have a discussion with vendors about STCs. In a practical
sense as well most vendors are busy finishing off their "-B" rev data-
out products (e.g. Garmin, Trig and others) and getting TSO approval
on those. And I see that as a gate to STC approval, but clearly they
could be overlapping TSO approval and STC development. And larger
companies beside having lots of STC approval experience may also be
able to leverage past ADS-B STC developed for trails, such as the
GOMEX ADS-B trials.


Darryl

On Oct 28, 4:54*pm, SoaringXCellence wrote:
On Oct 28, 1:40*pm, "Wayne Paul" wrote:



"Darryl Ramm" wrote in ...
On Oct 28, 8:47 am, Andy wrote:

Just to give a flavor ADS-B data-out systems as mandated for 2020 in
the USA for power aircraft (basically where a transponder is required
today) will put out the following data

Aircraft ICAO ID (can be made anonymous for a UAT on VFR flight)
Aircraft callsign/flight number (not required for VFR flight)
Time of applicability
GPS Lattitude
GPS Longitude
GPS altitude
Airborne/on-surface status
Northbound ground velocity component while airborne (from GPS)
Eastbound ground velocity component while airborne (from GPS)
Heading while on the surface
Ground speed while on the surface
Pressure altitude
Vertical rate (may be pressure or GPS based)
GPS uncertainty/integrity (which needs information form a fancy TSO-
C145 class WAAS GPS)
Ident (equivalent to transponder ident/SPI)
Distress/Emergency status
ADS-B data-in/display capability
TCAS equipage/status

This is a simplified list and there is various other status/validity
data as well. There is also the concept in ADS-B messages of an
estimated position, and even estimated velocity. But AFAIK this is not
intended for fancy manoeuvrings predictions - it is more intended to
allow different parts of the ADS-B infrastructure to project position
or velocity updated to a single time of applicability. There is space
for future expansion and as an example there is long-term work
underway to look at an ADS-B based replacement for TCAS that could
well utilize extra data transmission than that above, but think well
post 2020 for this to actually happen. My brain hurts enough thinking
about ADS-B as is.

---

BTW my suspicion is given that the FAA currently requires a STC for
any installation for ADS-B data out that it is currently not possible
to install any ADS-B data-out system in the USA in any certified
aircraft (including gliders) that only meets a subset of the 2020
mandate requirements (ie. does not include all the stuff above). Which
I expect the FAA would also require fully TSO-C154c/DO-282B (UAT) TSO-
C166b/DO-260B (1090ES) and with the corresponding TSO-C145 level GPS.
Experimental aircraft are another question since an STC cannot apply
to them. This STC restriction hopefully is short-term as its is going
to have a chilling effect on ADS-B data-out adoption in general
aviation and gliders. Besides some more complex issues you can start
to see even simple installation concerns that are probably causing
this current STC requirement, such as squat switch/or other on-ground
detection, needs to have a single squawk code and ident button across
any installed transponder(s) and ADS-B data-out devices, ability to
transmit a distress/emergency code, ability to turn off the ADS-B
transmissions if requested, etc.

Darryl

The following is not directed at any individual, it is simply an observation.

Even the old Garmin 12XL provides a lot more information in it's NMEA sentences the most of us realize. *It is data output sentences are fully compliant with NMEA 0183 ver 2.0. *The following link give an example of the data provided by "GPS engines" to software developer thus minimizing the amount of calculation required in display devices.http://www8.garmin.com/support/pdf/NMEA_0183.pdf

As I watch these PowerFLARM discussion it is apparent that many assume that things provided by the GPS must be created by the FLARM software.

Let us accept the fact that the PowerFLARM is just an upgrade of previous units that have been proven effective in increasing glider flight safety..

Respectfully,
Wayne

There have been several comment regarding the need for an STC to
install an ADS-B system in a certified aircraft.

This is not unlike the original situation with the installation of IFR
certified GPS systems, in the early 1990s. *I was involved in several
installations and most of the concerns were about the placement of
antenna and the effect of spurious signals on navigation.

Today if you get an IFR GPS installed in an aircraft the manufacturer
has a detailed description of antenna placement, cable routing and
possible interaction. *This data was collected during the earlier STC
period and as experience with more installations was gained, the FAA
changed the requirements from an STC to a 337, if installed in
compliance with the manufacturer's instructions.

I expect that the STC requirements for the ADS-B will follow the same
path over time.

Mike

Agreed completely. However, note that 1090 MHz
ADS-B (1090ES) uses the existing transponder antenna.
Much simpler than the early GPS situation.
However, UAT...

Hope that helps clarify the (not simple) situation,
Best Regards, Dave "YO electric"