UK Mode S. Our responce is required

Gilbert Smith wrote:

I manage an airstrip close to a CTR and close to the final approach
path to the international airport inside the CTR. We have an agreement
with the airspace authority which confines our flight paths to a safe
area.

A visiting pilot was given a transponder code and told to keep it
selected on his departure scheduled for 15 minutes after landing,
which he duly did. This caused a TCAS alert on a landing passenger
jet. Our agreement now specifies transponders switched off (not even
squawking standby) within 5 miles of our strip.

Gilbert, could you give some more details. Particularly, is your
strip in the UK? Is your agreement a local one with the airport, or is
it with (or known to) the National Air Traffic or Regulatory body?

On the general matter of aircraft location and proximity warning
systems, radar is essentially a product of World War II technology
whereas ADS-B is the future. ADS-B will provide air traffic
controllers and pilots with much more accurate information that will
help keep aircraft safely separated.

Those words come not from me, but from the US FAA.

As I understand it, ADS-B (Automatic Dependent Surveillance-Broadcast)
is a system based on Satellite Navigation that automatically transmits
GPS (or GLONASS or Galileo) position and other data from an aircraft to
other receivers in ATC units and/or other aircraft. It is being tested
by the USA FAA and also in Australia and certainly seems to be the
system of the future. Here is an extract from the FAA Fact Sheet dated
2 May 2006

"ADS-B is the future of air traffic control. Instead of using radar
data to keep aircraft at safe distances from one another, in the
future, signals from Global Positioning Satellites will provide air
traffic controllers and pilots with much more accurate information that
will help keep aircraft safely separated in the sky and on runways.

Although radar technology has advanced, it is essentially a product of
1940s World War II technology. Radar occasionally has problems
discriminating airplanes from migratory birds and rain “clutter.�
Secondary surveillance systems can determine what objects are because
they interrogate transponders; however, both primary and secondary
radars are very large structures that are expensive to deploy, need
lots of maintenance, and require the agency to lease real estate to
situate them.

ADS-B, on the other hand, receives data directly rather than passively
scanning for input like radars, so does not have a problem with
clutter. ADS-B ground stations are inexpensive compared to radar, and
are the size of mini refrigerators that essentially can go anywhere, so
they minimize the required real estate. In addition, ADS-B updates once
a second and locates aircraft with much more precision.

ADS-B also provides greater coverage, since ADS-B ground stations are
so much easier to place than radar. Remote areas where there is no
radar can now have precise surveillance coverage."

--------- end of FAA quote ---------

So why are some Authorities trying to impose expensive and power-hungry
transponders on people who fly mostly in unregulated airspace? Also,
there are many types of aircraft that do not have electrical
generators, such as gliders, hang gliders, para gliders and many motor
gliders (turbos for instance).

Surely, a future system based on Satellite Navigation would be much
better all round. GPS is now being carried in most GA and many sport
aircraft worldwide. A smart avionics engineer should be able to design
a special low-powered transmitter that would take an NMEA or other
output from existing GPS equipment and automatically transmit the data
on (electronic) request. This could be a practical step towards the
full ADS-B system of the future and would not involve the fitting of
transponders to such classes of aircraft, Mode S or otherwise. It
seems very similar to what is already part of ADS-B link technology,
the Universal Access Transceiver (UAT), for which development
(according to the FAA web site) started in the mid-1990s.

Ian Strachan
Lasham Gliding Centre, UK

The US FAA has a long history of requiring certain avionics and then
declaring it obsolete in a few years. The long history of slowly reducing
VHF comm radio channel separation is an example.

Ian is right that a GPS based ATC system is the best way to go. I fear it's
just too simple an answer for the bureaucrats to get their minds around.
There's an old joke that says the most terrifying words in the English
Language are, "I'm from the government and I'm here to help."

Bill Daniels

"Ian Strachan" wrote in message
oups.com...
Gilbert Smith wrote:

I manage an airstrip close to a CTR and close to the final approach
path to the international airport inside the CTR. We have an agreement
with the airspace authority which confines our flight paths to a safe
area.

A visiting pilot was given a transponder code and told to keep it
selected on his departure scheduled for 15 minutes after landing,
which he duly did. This caused a TCAS alert on a landing passenger
jet. Our agreement now specifies transponders switched off (not even
squawking standby) within 5 miles of our strip.

?Gilbert, could you give some more details. Particularly, is your
strip in the UK? Is your agreement a local one with the airport, or is
it with (or known to) the National Air Traffic or Regulatory body?

On the general matter of aircraft location and proximity warning
systems, radar is essentially a product of World War II technology
whereas ADS-B is the future. ADS-B will provide air traffic
controllers and pilots with much more accurate information that will
help keep aircraft safely separated.

Those words come not from me, but from the US FAA.

As I understand it, ADS-B (Automatic Dependent Surveillance-Broadcast)
is a system based on Satellite Navigation that automatically transmits
GPS (or GLONASS or Galileo) position and other data from an aircraft to
other receivers in ATC units and/or other aircraft. It is being tested
by the USA FAA and also in Australia and certainly seems to be the
system of the future. Here is an extract from the FAA Fact Sheet dated
2 May 2006

"ADS-B is the future of air traffic control. Instead of using radar
data to keep aircraft at safe distances from one another, in the
future, signals from Global Positioning Satellites will provide air
traffic controllers and pilots with much more accurate information that
will help keep aircraft safely separated in the sky and on runways.

Although radar technology has advanced, it is essentially a product of
1940s World War II technology. Radar occasionally has problems
discriminating airplanes from migratory birds and rain "clutter."
Secondary surveillance systems can determine what objects are because
they interrogate transponders; however, both primary and secondary
radars are very large structures that are expensive to deploy, need
lots of maintenance, and require the agency to lease real estate to
situate them.

ADS-B, on the other hand, receives data directly rather than passively
scanning for input like radars, so does not have a problem with
clutter. ADS-B ground stations are inexpensive compared to radar, and
are the size of mini refrigerators that essentially can go anywhere, so
they minimize the required real estate. In addition, ADS-B updates once
a second and locates aircraft with much more precision.

ADS-B also provides greater coverage, since ADS-B ground stations are
so much easier to place than radar. Remote areas where there is no
radar can now have precise surveillance coverage."

--------- end of FAA quote ---------

So why are some Authorities trying to impose expensive and power-hungry
transponders on people who fly mostly in unregulated airspace? Also,
there are many types of aircraft that do not have electrical
generators, such as gliders, hang gliders, para gliders and many motor
gliders (turbos for instance).

Surely, a future system based on Satellite Navigation would be much
better all round. GPS is now being carried in most GA and many sport
aircraft worldwide. A smart avionics engineer should be able to design
a special low-powered transmitter that would take an NMEA or other
output from existing GPS equipment and automatically transmit the data
on (electronic) request. This could be a practical step towards the
full ADS-B system of the future and would not involve the fitting of
transponders to such classes of aircraft, Mode S or otherwise. It
seems very similar to what is already part of ADS-B link technology,
the Universal Access Transceiver (UAT), for which development
(according to the FAA web site) started in the mid-1990s.

Ian Strachan
Lasham Gliding Centre, UK

Ian Strachan wrote:
aircraft worldwide. A smart avionics engineer should be able to design
a special low-powered transmitter that would take an NMEA or other
output from existing GPS equipment and automatically transmit the data
on (electronic) request. This could be a practical step towards the

I'm sure most here know FLARM http://www.flarm.com/index_en.html .

While I'd not suggest it to the CAA for ATC because of it's limited
range, it is actually a step in this direction.

Regards
-Gerhard
--
http://gwesp.tx0.org/
Gerhard Wesp / Holderenweg 2 / CH-8134 Adliswil
+41 (0)76 505 1149 / +43 699 815 987 70 (mobile)
+41 (0)44 668 1878 (office)
+41 (0)44 200 1818 (office fax)

On Wed, 09 Aug 2006 17:48:00 +0000, Gerhard Wesp wrote:

Ian Strachan wrote:
aircraft worldwide. A smart avionics engineer should be able to design
a special low-powered transmitter that would take an NMEA or other
output from existing GPS equipment and automatically transmit the data
on (electronic) request. This could be a practical step towards the

I'm sure most here know FLARM http://www.flarm.com/index_en.html .

While I'd not suggest it to the CAA for ATC because of it's limited
range, it is actually a step in this direction.

I have a both a Flarm and Mode C Transponder in my glider.

For those who have not flown with Flarm, I can confirm that they work
exceeding well. The major limitation is the fact that not all gliders
at our club are equipped with it.

There are some clever tricks in Flarms. The transmitters use the clock
signal from the GPS receiver to synchronize their transmissions so that
there are no "collisions". This allows a large number of Flarms to share a
limited amount of bandwidth. I think Flarm technology, coupled with a
higher power transmitter, could go a long way to making transponders
redundant.

I use the transponder on wave days. We can get clearance into a
"window" in controlled airspace, but we have to squawk. We have to talk to
ATC at the same time and we very soon know if they can't see us.
Unfortunately this has happened more often than I like, both with my own
glider and with others at our club.

The problems can be tracked down to many sources:

- Battery problems. (The most common). Even if a battery is fully charged
with healthy voltage on the ground, it does not mean that it is capable of
delivering it's rated current for the duration of a flight. Having two is
essential, but I have had two fully charged, apparently healthy, batteries
fail on the same flight. Often when a battery is under performing, there
is no clear indication - the transponder appears to be working normally -
but ATC can't see me until I swap onto the spare battery.

- Wiring issues. Space in gliders is cramped and access to the available
space if often very difficult. It is just not possible to install heavy
cable racks and heavy connectors with wire locked retaining screws. Hence
the installations in gliders are, on average, less reliable than those in
power aircraft.

- Antenna issues. There is not much volume inside a glider to mount a
transponder antenna and things are worse for those with carbon fuselages.
Many gliders in our club have antenna mounted behind the instrument panel
which is far from ideal. Mine is mounted in the fuselage where other
gliders might have a pop-up engine. But access there is a major issue and
there is still significant shielding from the retracted under-carriage.
Those with external antenna are subject to damage during outlandings,
trailering, rigging and general ground handling.

Perhaps the biggest issue is that we have no means of testing
transponders before flight, we only find out if there is a problem when we
talk to ATC. (Here Flarm has a major advantage over the transponders. We
have receivers as well as transmitters and we can soon detect if one of
them is not working.) I would not be surprised if there are pilots flying
transponder equipped gliders, who squawk regularly in the belief that the
heavy a/c will pick them up on their warning receivers, but in actual fact
are not being seen.

I think it would be very short sighted to assume that if all gliders were
equipped with transponders that they would all be detected by ground
and/or airborne radar. If heavy aircraft are routed between the gliders
that are detected, their could be some surprises.

On the other hand, if all gliders were equipped with high power Flarms, we
would have a very useful glider/glider midair proximity warning system at
the same time as providing an indication of our presence to others.


Ian

(I would be happy to submit my opinions to the UK authorities, but I fly
in South Africa, so would they even consider it?)

Ian,

Yes we would very much like to have your views, if you send them to me by
e-mail I will see that they reach the correct people.

Thank you for your posting.

Regards,

Bill.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Ian" wrote in message
news
On Wed, 09 Aug 2006 17:48:00 +0000, Gerhard Wesp wrote:


Ian Strachan wrote:


aircraft worldwide. A smart avionics engineer should be able to design
a special low-powered transmitter that would take an NMEA or other
output from existing GPS equipment and automatically transmit the data
on (electronic) request. This could be a practical step towards the


I'm sure most here know FLARM http://www.flarm.com/index_en.html .

While I'd not suggest it to the CAA for ATC because of it's limited
range, it is actually a step in this direction.


I have a both a Flarm and Mode C Transponder in my glider.

For those who have not flown with Flarm, I can confirm that they work
exceeding well. The major limitation is the fact that not all gliders
at our club are equipped with it.

There are some clever tricks in Flarms. The transmitters use the clock
signal from the GPS receiver to synchronize their transmissions so that
there are no "collisions". This allows a large number of Flarms to share
a limited amount of bandwidth. I think Flarm technology, coupled with a
higher power transmitter, could go a long way to making transponders
redundant.

I use the transponder on wave days. We can get clearance into a
"window" in controlled airspace, but we have to squawk. We have to talk
to ATC at the same time and we very soon know if they can't see us.
Unfortunately this has happened more often than I like, both with my own
glider and with others at our club.

The problems can be tracked down to many sources:

- Battery problems. (The most common). Even if a battery is fully
charged with healthy voltage on the ground, it does not mean that it is
capable of delivering it's rated current for the duration of a flight.
Having two is essential, but I have had two fully charged, apparently
healthy, batteries fail on the same flight. Often when a battery is under
performing, there is no clear indication - the transponder appears to be
working normally - but ATC can't see me until I swap onto the spare
battery.

- Wiring issues. Space in gliders is cramped and access to the available
space if often very difficult. It is just not possible to install heavy
cable racks and heavy connectors with wire locked retaining screws. Hence
the installations in gliders are, on average, less reliable than those in
power aircraft.

- Antenna issues. There is not much volume inside a glider to mount a
transponder antenna and things are worse for those with carbon fuselages.
Many gliders in our club have antenna mounted behind the instrument panel
which is far from ideal. Mine is mounted in the fuselage where other
gliders might have a pop-up engine. But access there is a major issue and
there is still significant shielding from the retracted under-carriage.
Those with external antenna are subject to damage during outlandings,
trailering, rigging and general ground handling.

Perhaps the biggest issue is that we have no means of testing
transponders before flight, we only find out if there is a problem when we
talk to ATC. (Here Flarm has a major advantage over the transponders. We
have receivers as well as transmitters and we can soon detect if one of
them is not working.) I would not be surprised if there are pilots flying
transponder equipped gliders, who squawk regularly in the belief that the
heavy a/c will pick them up on their warning receivers, but in actual fact
are not being seen.

I think it would be very short sighted to assume that if all gliders were
equipped with transponders that they would all be detected by ground
and/or airborne radar. If heavy aircraft are routed between the gliders
that are detected, their could be some surprises.

On the other hand, if all gliders were equipped with high power Flarms, we
would have a very useful glider/glider midair proximity warning system at
the same time as providing an indication of our presence to others.

Ian

(I would be happy to submit my opinions to the UK authorities, but I fly
in South Africa, so would they even consider it?)

Ian Strachan wrote:

As I understand it, ADS-B (Automatic Dependent Surveillance-Broadcast)
is a system based on Satellite Navigation that automatically transmits
GPS (or GLONASS or Galileo) position and other data from an aircraft to
other receivers in ATC units and/or other aircraft. It is being tested
by the USA FAA and also in Australia and certainly seems to be the
system of the future. Here is an extract from the FAA Fact Sheet dated
2 May 2006

That is still true in part for Australia but ASA (AirServices Oz) has
recently (about 20 July) withdrawn its RFP for lower airspace ADS-B.
Upper airspace appears to still be going ahead but the application of
ADS-B to ALL aircraft - the original aspiration - appears to have been
somewhat curtailed.

AFAIK there are no current suitable low power consumption airborne units
on the market and the ground station network being implemented will
probably not be as extensive as we'd hoped.

Obviously, widespread implementation in the US will have the same
trickledown effect worldwide as almost all other en route systems from
A-N ranges to GPS but there are problems. Avweb discussed some of these
- I'll see if I can find the reference.

This may not have helped your case

GC

Graeme Cant wrote:
Ian Strachan wrote:

As I understand it, ADS-B (Automatic Dependent Surveillance-Broadcast)
is a system based on Satellite Navigation that automatically transmits
GPS (or GLONASS or Galileo) position and other data from an aircraft to
other receivers in ATC units and/or other aircraft. It is being tested
by the USA FAA and also in Australia and certainly seems to be the
system of the future. Here is an extract from the FAA Fact Sheet dated
2 May 2006

That is still true in part for Australia but ASA (AirServices Oz) has
recently (about 20 July) withdrawn its RFP for lower airspace ADS-B.
Upper airspace appears to still be going ahead but the application of
ADS-B to ALL aircraft - the original aspiration - appears to have been
somewhat curtailed.

Yes, this has been publicised in the aviation press. I don't regard
that as any condemnation of ADS-B which is at an early stage of
development and implementation. I guess that ASA are looking at the
bugs and working them out for the future. Very sensible.

After all, the use of prototype ADS-B in Alaska was of the nature of a
trial and it is interesting that, as a result, the magazine Aviation
Week reports that the FAA will increase the ADS-B cover to parts of the
rest of the USA.

As the FAA fact sheet said, "radar is essentially a product of World
War II technology whereas ADS-B is the future". Those of us with an
interest in the long term future of GA and Sport aircraft should latch
on to that, because SatNav-based systems are far more compatible with,
and useful to, what we do compared to radar-based systems.
Particularly if extra equipment is to be forced on some of us by
regulatory authorities on grounds of "safety" whether we think that is
a spurious argument or not.

Ian Strachan
Lasham Gliding Centre, UK