"A Guide to Transponders in Sailplanes" - updated!

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.

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.

This argument seems rather like deciding to put your seat belt on in a
car just before you have a crash!

Anyway, this rule isn't an option, it is mandatory. If you have a
transponder the regs say it MUST be on while you are flying. No pilot
discretion here.

And don't give me the battery argument. Electricity is the fuel for
your instruments, including your safety ones such as the radio and
transponder. In my book, starting a flight with insufficient battery
power is as irresponsible as flying a power plane cross-country with
insufficient fuel.

It's the pilot's responsibility to make sure that he has everything
needed for a safe flight and to comply with regulations and that
includes power for the instruments.

Mike

On Feb 14, 9:42 pm, Mike the Strike wrote:
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.

This argument seems rather like deciding to put your seat belt on in a
car just before you have a crash!

Anyway, this rule isn't an option, it is mandatory. If you have a
transponder the regs say it MUST be on while you are flying. No pilot
discretion here.

And don't give me the battery argument. Electricity is the fuel for
your instruments, including your safety ones such as the radio and
transponder. In my book, starting a flight with insufficient battery
power is as irresponsible as flying a power plane cross-country with
insufficient fuel.

It's the pilot's responsibility to make sure that he has everything
needed for a safe flight and to comply with regulations and that
includes power for the instruments.

Mike

I should add that the article is excellent - the battery issue and
turning transponders off is the only point that I disagree with. With
a $2,000+ transponder in a $50,000+ sailplane, it seems ironic that
people are too mean to add another $10 battery. A dedicated 7 Ah
battery will power a Microair transponder for 12 to 15 hours, in my
experience. This is a no-brainer.

We have had a collision between an aircraft and a sailplane whose
transponder was turned off "to save the batteries", so this isn't just
a theoretical problem.

Mike

On Feb 14, 8:42 pm, Mike the Strike wrote:
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.

This argument seems rather like deciding to put your seat belt on in a
car just before you have a crash!

And that is the only time you need to have it on - it has no value at
any other time.

Actually, the argument is more about encouraging people to install the
seat belt in the first place, and hope they will use it when it
matters.

Anyway, this rule isn't an option, it is mandatory. If you have a
transponder the regs say it MUST be on while you are flying. No pilot
discretion here.

The nuance here is that we are not required to have transponders
installed, so it seems reasonable to argue that pilot A, who turns on
the transponder for some of the flight, is improving safety more than
pilot B, who doesn't install a transponder. Yes, pilot A is operating
contrary to the regulations and pilot B isn't, but which one is making
flight safer? Our SSA representatives that discuss these things with
the FAA say the FAA much prefers pilot A.

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