"A Guide to Transponders in Sailplanes" - updated!

This guide, originally published in Soaring in 2002, and updated in
2004, is now expanded another 10 pages to include information on Mode
S transponders, ADS-B equipment, portable transponder detectors like
the Zaon MRX, and the "glider TCAS" (FLARM).

Other new sections are "Myth-information about transponders" and "Why
doesn't the SSA..." Even if you have a transponder already, you might
enjoy reading those two sections.

The updated Guide is available from the Soaring Safety Foundation
website at:

http://tinyurl.com/y739x4

or you can go to the site and find it yourself:

http://www.soaringsafety.org/

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric,

Excellent document - should be required reading for all glider (and
power) pilots.

One comment - you state that a transponder will not provide protection
from "tactical aircraft like fighters that don't use TCAS". While it
is true that fighters don't have TCAS, most Air Force fighters
(specifically, all F-15s and most F-16s) have active transponder
interrogators (in addition to their air-to-air radar) that can detect
transponder equipped gliders very easily. Even the old F-4 that I
used to fly in had a crude but effective transponder interrogator, and
we used it a lot to find VFR traffic when low flying in MOAs (the
antique steam-powered radar in the F-4 left a lot to be desired at low
altitude...)

The A-10, as far as I know, isn't equipped with either air-to-air
radar or an interrogator - so if you share aispace with Warthogs. keep
an eye out for them!

As far as Navy/Marine fighters - all F-18s have air-to-air radars, but
I think only the latest Hornets have an interrogator. Not sure about
Harriers, but again, the later Harriers have basically the same air-to-
air radar as the Hornet.

Transponders are wonderful, but I really think a detector device like
the MRX is even more essential in some areas.

Cheers,

Kirk
66

On Feb 11, 12:47 am, "kirk.stant" wrote:
Eric,

Excellent document - should be required reading for all glider (and
power) pilots.

One comment - you state that a transponder will not provide protection
from "tactical aircraft like fighters that don't use TCAS". While it
is true that fighters don't have TCAS, most Air Force fighters
(specifically, all F-15s and most F-16s) have active transponder
interrogators (in addition to their air-to-air radar) that can detect
transponder equipped gliders very easily. Even the old F-4 that I
used to fly in had a crude but effective transponder interrogator, and
we used it a lot to find VFR traffic when low flying in MOAs (the
antique steam-powered radar in the F-4 left a lot to be desired at low
altitude...)

The A-10, as far as I know, isn't equipped with either air-to-air
radar or an interrogator - so if you share aispace with Warthogs. keep
an eye out for them!

As far as Navy/Marine fighters - all F-18s have air-to-air radars, but
I think only the latest Hornets have an interrogator. Not sure about
Harriers, but again, the later Harriers have basically the same air-to-
air radar as the Hornet.

Transponders are wonderful, but I really think a detector device like
the MRX is even more essential in some areas.

Cheers,

Kirk
66

THanks, Kirk, I'll look into these and update as needed. We're on the
road to the convention at the moment.

Eric

Very nice update. One missing issue: installation legalities. I konw
some pilots have gotten 337s. I know that many have not. Do we really
need a 337? What reg says so (I looked to no avail)? Why, for example,
would a transponder need a 337 but a radio does not? What is, really,
required to legally install a transponder?

John Cochrane

On Feb 11, 11:00 am, BB wrote:
Very nice update. One missing issue: installation legalities. I konw
some pilots have gotten 337s. I know that many have not. Do we really
need a 337? What reg says so (I looked to no avail)? Why, for example,
would a transponder need a 337 but a radio does not? What is, really,
required to legally install a transponder?

John Cochrane

I've skirted around the legalities, because it's a confusing issue to
me, too. I would like to address it, however, so if someone
knowledgeable can provide me with info on it, or point to a good
source (documents or person(s)), I'll be glad to add a section on it.

Otherwise, we'll have to wait until I can dig it out myself!

You say to mount the aerial under your thigh.... not a good idea for a
200 watt transmitter cause it will cook your balls. Most Transponders
have a minimum distance allowed from people, like 3 feet. Please check
this out !

Eric Greenwell wrote:
On Feb 11, 11:00 am, BB wrote:
Very nice update. One missing issue: installation legalities. I konw
some pilots have gotten 337s. I know that many have not. Do we really
need a 337? What reg says so (I looked to no avail)? Why, for example,
would a transponder need a 337 but a radio does not? What is, really,
required to legally install a transponder?

John Cochrane

I've skirted around the legalities, because it's a confusing issue to
me, too. I would like to address it, however, so if someone
knowledgeable can provide me with info on it, or point to a good
source (documents or person(s)), I'll be glad to add a section on it.

Otherwise, we'll have to wait until I can dig it out myself!

absolutely....installing a transponder doesn't require any documentation if
it's in a experimental other than maybe a logbook entry and a new
wt/bal......BUT turning it on does!
Any Transponder equipped aircraft has to have a static system test and be
signed off by an approved avionics repair station prior to use....these all
then can be monitored by ATC... without this what is to prevent a
transponder equipped glider flying at 10,000' and reporting to ATC that he
is actually at 9000' and directly in line with the flight path of a 747!
Also.....consider, a Transponder equipped aircraft is also REQUIRED to have
the transponder ON and reporting at all times from wheels up to wheels
down......not just as I have heard many glider pilots saying they "only use"
the transponder when they are flying at or near areas of high traffic....
think about this....
tim

Please visit the Wings & Wheels website at www.wingsandwheels.com

Eric Greenwell wrote:
On Feb 11, 11:00 am, BB wrote:
Very nice update. One missing issue: installation legalities. I konw
some pilots have gotten 337s. I know that many have not. Do we really
need a 337? What reg says so (I looked to no avail)? Why, for example,
would a transponder need a 337 but a radio does not? What is, really,
required to legally install a transponder?

John Cochrane

I've skirted around the legalities, because it's a confusing issue to
me, too. I would like to address it, however, so if someone
knowledgeable can provide me with info on it, or point to a good
source (documents or person(s)), I'll be glad to add a section on it.

Otherwise, we'll have to wait until I can dig it out myself!

On Feb 14, 7:44 am, "Tim Mara" wrote:
absolutely....installing a transponder doesn't require any documentation if
it's in a experimental other than maybe a logbook entry and a new
wt/bal......BUT turning it on does!
Any Transponder equipped aircraft has to have a static system test and be
signed off by an approved avionics repair station prior to use....these all
then can be monitored by ATC... without this what is to prevent a
transponder equipped glider flying at 10,000' and reporting to ATC that he
is actually at 9000' and directly in line with the flight path of a 747!

Even worse would be the glider reporting it was at 9000' and have the
747 at 10,000'. ATC deals with this by acknowledging the VFR target
might not be reporting until they've had contact with the pilot and
verified the altitude.

Also.....consider, a Transponder equipped aircraft is also REQUIRED to have
the transponder ON and reporting at all times from wheels up to wheels
down......not just as I have heard many glider pilots saying they "only use"
the transponder when they are flying at or near areas of high traffic....
think about this....

A lot of us have thought about this, including people in the FAA, and
decided it's a lot better to have a transponder on in areas that need
it, instead of risking a dead battery (meaning NO radio or
transponder) later in the flight, or discouraging pilots with marginal
batteries from installing a transponder. I covered this in the the
"Guide". Take a look at that section and see if it promotes flight
safety better than strict adherence to the "always on" rule; also,
take a look at the "Why doesn't the SSA ..." section that addresses
the FAA's official position.

I found this an interesting article, and largely ties in with my personal
experiences with transponders. However I have two comments:

On Thu, 14 Feb 2008 10:44:57 -0500, Tim Mara wrote:

Any Transponder equipped aircraft has to have a static system test and
be signed off by an approved avionics repair station prior to
use....these all then can be monitored by ATC... without this what is to
prevent a transponder equipped glider flying at 10,000' and reporting to
ATC that he is actually at 9000' and directly in line with the flight
path of a 747!

Firstly, Regulations aside. I am not sure that the error of cockpit
static verses static from the static ports makes a significant difference
in altitude readings in a typical glider. All of our Flight Recorders and
Barographs read cockpit static and I have never heard of a trace that had
obvious errors (eg trace 500' into controlled due to static errors, or a
significant deviation between GPS altitude and baragraph altitude that
could not be explained by the atmospheric conditions on the day.) Now a
power aircraft with a pressurized cabin presents a different challenge ...

Secondly, the problem with batteries is that there is no practical way to
"certify" the amount of energy available in the battery before the
flight. It can be estimated from the state of charge and the known age/
condition, but it can't be measured like the fuel level in a tank. Worse
still, when a battery fails during flight its performance degrades
gradually so may not be immediately apparent to the pilot that there is a
problem. In this situation the transponder display might look healthy
while ATC get an inaccurate signal, a weak one or none at all. (I have
seen my encoder read 400' out when running of a deteriorating battery.)

For this reason I believe it is essential to have at least two 7Ah
batteries, as well as a means to switch between them so they can be used
as a "main" battery to a "standby" one. At least when you switch over you
know the first battery is depleted, if it happens prematurely then you
know it needs to be replaced.

Ian

Tim Mara wrote:


...a Transponder equipped aircraft is also REQUIRED to have
the transponder ON and reporting at all times from wheels up to wheels
down....


Yes, we keep bumping against this reg whenever the subject comes up.

What is the rationale behind such a requirement?

Whose interests does it serve to differentiate between uninstalled
transponders and unused transponders?

Is it just another example of bureaucratic passive/aggressive
bitchiness, or is there an actual Safety of Flight context that
thoughtful glider pilots can appreciate?



Jack