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

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 10/28/2010 7:29 AM, Mike Schumann wrote:
On 10/27/2010 11:16 PM, Eric Greenwell wrote:


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?

I'm not an expert on either FLARM or ADS-B. I believe that ADS-B
currently only transmits absolute position. Future enhancements might
transmit trajectory, which would be most useful for aircraft with
Flight Management Systems where the trajectory is well defined and
could be used by the ATC system for airspace management.

Regardless of whether or not the trajectory is transmitted, a
sophisticated receiving system (either FLARM or ADS-B based), can
remember each aircraft's position data and compute it's current
trajectory. While a glider might be moving 75 ft / sec, this is
obviously in a relatively forward direction.
You may be underestimating the value of transmitting the projected path.
When another glider is first detected, your unit has only one position
report and can not determine the flight path from that single point, and
it will take several more precious seconds to determine the flight path
of the potential threat; however, because the projected path is
transmitted every second, your unit immediately knows it.

Neither the transmitting nor the receiving FLARM or ADS-B system can
predict an abrupt change in course that a pilot flying manually might
command. However, every aircraft has physical limits on roll rates,
etc. that restrain the potential change in direction that can occur
within the one second update interval of these systems. As a result,
the systems can, theoretically, compute a pear shaped threat envelope
for each aircraft and limit collision warnings to those situations
where these envelopes intersect.

It would be interesting to get more detailed information on the exact
algorithms that FLARM uses in it's collision threat analysis and
compare this to the actual unit performance in situations where
gliders are flying at close distances in formation or in gaggles.
This could also help pilots understand the limitations of these
systems so they don't develop a false sense of security in situations
where these systems are not reliable.

I'm sure the developers have tested their algorithms with thousands of
simulations using IGC files from gliders in many situations. The Parowan
accident simulation at

http://www.gliderpilot.org/Flarm-Par...dairSimulation

shows what can be done. It would be interesting, informative, and
entertaining if there was a website or application that would let us run
IGC files we select in a simulation like this. I'm curious about how
Flarm would react in a few situations I've encountered. Doing
simulations on a pilot's own files might be more persuasive of the value
of Flarm than even the most well-written explanations, and much more
easily understood than the algorithms themselves.

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

On 10/28/2010 2:14 PM, Eric Greenwell wrote:
On 10/28/2010 7:29 AM, Mike Schumann wrote:
On 10/27/2010 11:16 PM, Eric Greenwell wrote:


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?

I'm not an expert on either FLARM or ADS-B. I believe that ADS-B
currently only transmits absolute position. Future enhancements might
transmit trajectory, which would be most useful for aircraft with
Flight Management Systems where the trajectory is well defined and
could be used by the ATC system for airspace management.

Regardless of whether or not the trajectory is transmitted, a
sophisticated receiving system (either FLARM or ADS-B based), can
remember each aircraft's position data and compute it's current
trajectory. While a glider might be moving 75 ft / sec, this is
obviously in a relatively forward direction.
You may be underestimating the value of transmitting the projected path.
When another glider is first detected, your unit has only one position
report and can not determine the flight path from that single point, and
it will take several more precious seconds to determine the flight path
of the potential threat; however, because the projected path is
transmitted every second, your unit immediately knows it.

Neither the transmitting nor the receiving FLARM or ADS-B system can
predict an abrupt change in course that a pilot flying manually might
command. However, every aircraft has physical limits on roll rates,
etc. that restrain the potential change in direction that can occur
within the one second update interval of these systems. As a result,
the systems can, theoretically, compute a pear shaped threat envelope
for each aircraft and limit collision warnings to those situations
where these envelopes intersect.

It would be interesting to get more detailed information on the exact
algorithms that FLARM uses in it's collision threat analysis and
compare this to the actual unit performance in situations where
gliders are flying at close distances in formation or in gaggles. This
could also help pilots understand the limitations of these systems so
they don't develop a false sense of security in situations where these
systems are not reliable.

I'm sure the developers have tested their algorithms with thousands of
simulations using IGC files from gliders in many situations. The Parowan
accident simulation at

http://www.gliderpilot.org/Flarm-Par...dairSimulation

shows what can be done. It would be interesting, informative, and
entertaining if there was a website or application that would let us run
IGC files we select in a simulation like this. I'm curious about how
Flarm would react in a few situations I've encountered. Doing
simulations on a pilot's own files might be more persuasive of the value
of Flarm than even the most well-written explanations, and much more
easily understood than the algorithms themselves.


There's no question that FLARM or ADS-B based systems could have easily
prevented the Parowan mid-air. My question is how much you can rely on
this type of equipment to accurately warn you of collisions when you are
flying in gaggles.

Obviously knowing the relative position of other gliders in the gaggle
is helpful. I would be very skeptical, however, of putting my faith in
FLARM or any other system to accurately warn me of a collision with
another glider that was in the same thermal, near my altitude, that was
in my blind spot.

Transmitting the project path of the aircraft is really only beneficial
if the equipment on board the transmitting aircraft has some added
information that is not available to the receiver on the transmitting
aircraft's intent.

With both FLARM and ADS-B systems, the initial visibility of the other
aircraft occurs way before there is any collision threat, so the
receiver should have no difficulty computing the project path of the
other aircraft. ADS-B actually transmits the category of aircraft (i.e.
glider, balloon, etc...) so the receiver can get a pretty good hint on
the type of maneuvers that can be expected.

--
Mike Schumann

Eric Greenwell wrote:
On 10/28/2010 7:29 AM, Mike Schumann wrote:

It would be interesting to get more detailed information on the exact
algorithms that FLARM uses in it's collision threat analysis

I tend to assume that if there is one thing that the developers want to
keep, then it's this algorithm. ;-)

But from real life experience, it seem's to work pretty well.

It would be interesting, informative, andentertaining if there was
a website or application that would let us runIGC files we select
in a simulation like this.

Entertaining... well... but educative indeed. And it would provide the
FLARM developers with a huge test crew for free.

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

On 10/28/2010 11:32 AM, Mike Schumann wrote:


There's no question that FLARM or ADS-B based systems could have
easily prevented the Parowan mid-air. My question is how much you can
rely on this type of equipment to accurately warn you of collisions
when you are flying in gaggles.

Obviously knowing the relative position of other gliders in the gaggle
is helpful. I would be very skeptical, however, of putting my faith
in FLARM or any other system to accurately warn me of a collision with
another glider that was in the same thermal, near my altitude, that
was in my blind spot.
This situation is addressed at

http://www.gliderpilot.org/FlarmFlig...andPerformance

where it states that the human eye is better than Flarm. I don't think
anyone has claimed Flarm is better in every possible situation, and
users and Flarm itself repeatedly state you must still look outside to
have the best protection; however, I believe Flarm will indicate there
is a glider behind you, something a pilot might not always be aware of,
so it still has value in this situation.

Transmitting the project path of the aircraft is really only
beneficial if the equipment on board the transmitting aircraft has
some added information that is not available to the receiver on the
transmitting aircraft's intent.

With both FLARM and ADS-B systems, the initial visibility of the other
aircraft occurs way before there is any collision threat, so the
receiver should have no difficulty computing the project path of the
other aircraft. ADS-B actually transmits the category of aircraft
(i.e. glider, balloon, etc...) so the receiver can get a pretty good
hint on the type of maneuvers that can be expected.
I can think of three situations where the time involved can be reduced:

1) two gliders approaching head on. At 100 knots each - a 200 knot
closing speed - that's only 18 seconds or so to collision. How many
seconds of warning do you lose while collecting enough points to make a
good estimate of the projected paths - 5 seconds, 10 seconds? I don't
know, but I'd prefer to know sooner than later.

2) Ridge or mountain flying, where the transmissions are blocked by the
terrain. Once they round the corner of the ridge, there may not be
enough time to calculate a projected path.

3) shortened range due to signal blockage by the wings or fuselage.


--

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

Mike Schumann wrote:
My question is how much you can rely on
this type of equipment to accurately warn you of collisions when you are
flying in gaggles.

In gaggles: Not at all. Period. Simply not possible - and not
necessairy, either.

"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