"A Guide to Transponders in Sailplanes" - updated!

On Feb 22, 9:17 am, J a c k wrote:
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

I suspect it is to prevent thinking like "I'll just turn this little
box off and bust whatever FAR I feel like cuz noboby can see me" (even
if ATC can see you as a primary on radar). Seems a perfectly fine
requirement for a powered aircraft and I'd be surprised if gliders
were front and center in any thinking about this requirement. As for
bitchiness, the FAA seems to be showing perfect restraint in not
enforcing the thing you seemed concerned about, and therefore helping
encourage use of transponders in sailplanes. Of course we can keep
whining about this and other requirements and maybe in a long shot end
up with removing a regulation that does not seem to be enforced or
maybe worse end up with more regulations, maybe mandatory Mode-C/ADS-B
for all flight...

For many people flying in high-traffic areas, and that's a lot more
than just around Reno, it is not outrageous to expect them to install
batteries (and/or possibly solar panels at significantly higher cost)
so they can operate transponders thought quite long flights. So there
is no need to turn off those transponders - and in those areas that
*is* a safety of flight issue.

Darryl

Darryl Ramm wrote:


I suspect it is to prevent thinking like "I'll just turn this little
box off and bust whatever FAR I feel like cuz noboby can see me" (even
if ATC can see you as a primary on radar).

And "turning the little box off" is more deleterious to safety, or
enforcement, than no installation at all?



Seems a perfectly fine
requirement for a powered aircraft and I'd be surprised if gliders
were front and center in any thinking about this requirement.


Agreed. Gliders are not often a concern. So why restrict gliders?



...the FAA seems to be showing perfect restraint in not
enforcing the thing you seemed concerned about, and therefore helping
encourage use of transponders in sailplanes.


I'm sure there are several practical considerations involved, including
the difficulty of enforcement. But when an agency "chooses" to enforce
or not enforce a particular reg, alarm bells ought to go off everywhere.
I don't dispute there are mostly rational people in the FAA. My dealings
with them have always been satisfactory. The problem is the process,
which does not seem very rational. The production of incompletely
structured, yet overly complex, regulations is pervasive in aviation, as
elsewhere.



For many people flying in high-traffic areas, and that's a lot more
than just around Reno, it is not outrageous to expect them to install
batteries (and/or possibly solar panels at significantly higher cost)
so they can operate transponders thought quite long flights. So there
is no need to turn off those transponders - and in those areas that
*is* a safety of flight issue.


It is reasonable that a transponder installation will include adequate
power to insure required operation of the equipment, when the
requirement is based on traffic management. It is not reasonable to
require that the installation will support operation in circumstances
where traffic management by ATC is not an issue. Decisions regarding use
of the transponder in circumstances not involving traffic separation or
National Security concerns should be left to the operator.

Non-enforcement is a non-reason. That can change overnight. If a rule is
illogical, or realistically unenforceable, or counter-productive, then
it ought not be a rule.



Jack

On Feb 14, 2:12 am, user wrote:
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 !

I mentioned some pilots have mounted it in that position. I don't
think I said to do it that way. Can you tell me the page and paragraph
that leads you to think I recommended it? Perhaps its not written
clearly.

And to reiterate, it's not a "200 watt transmitter". The peak power of
the pulses is 200 watt, but it's only about a 5 watt max transmitter,
as the pulses are short.

"Eric Greenwell" wrote in message
...

And to reiterate, it's not a "200 watt transmitter". The peak power of
the pulses is 200 watt, but it's only about a 5 watt max transmitter,
as the pulses are short.


I know you are talking about peak power vs average power. However, even
though pulse width is narrow, and thus the average radiation from a 175 or
250 watt transponder might be on the order of 5 watts, I'm not sure the
radiation exposure should be equated to just the low average power.

Consider a single high powered pulse as being one .22 rifle bullet. The
bullet might have on the order of 100 ft pounds of energy and would
obviously do considerable tissue damage. Compare that to several hundred
BB's from a low powered air rifle, the combined energy of which equals the
energy of that one .22 bullet. Same total energy, far less damage. The point
I'm trying to make is that pulsed high energy may well do more tissue damage
than the same total amount of low level energy delivered over a longer time
frame.

I want that transponder antenna installed away from me.

bumper

On Feb 15, 10:18 am, "bumper" wrote:
"Eric Greenwell" wrote in message

...



And to reiterate, it's not a "200 watt transmitter". The peak power of
the pulses is 200 watt, but it's only about a 5 watt max transmitter,
as the pulses are short.

I know you are talking about peak power vs average power. However, even
though pulse width is narrow, and thus the average radiation from a 175 or
250 watt transponder might be on the order of 5 watts, I'm not sure the
radiation exposure should be equated to just the low average power.

Consider a single high powered pulse as being one .22 rifle bullet. The
bullet might have on the order of 100 ft pounds of energy and would
obviously do considerable tissue damage. Compare that to several hundred
BB's from a low powered air rifle, the combined energy of which equals the
energy of that one .22 bullet. Same total energy, far less damage. The point
I'm trying to make is that pulsed high energy may well do more tissue damage
than the same total amount of low level energy delivered over a longer time
frame.

I want that transponder antenna installed away from me.

bumper

A colleague who deals with radiation safety said that the argument
that low energy long-duration doses of radiation are equivalent to
high energy short duration doses is like equating jumping off a 3-foot
wall ten times with jumping off a 30-foot wall once.

Mike

On Feb 15, 12:08 pm, Mike the Strike wrote:


A colleague who deals with radiation safety said that the argument
that low energy long-duration doses of radiation are equivalent to
high energy short duration doses is like equating jumping off a 3-foot
wall ten times with jumping off a 30-foot wall once.

It's my understanding that microwave radiation at these power levels
and the mass of tissue involved will primarily cause heating by
vibrating water molecules, and no significant ionization. The amount
of heating produced depends on the amount of energy delivered and the
amount of mass. So, 5 watts is the important number in this case, and
most of that will not be delivered to the body, but will be radiated
in directions away from the body.

I hope it's clear that I don't recommend putting the antenna close to
your body; however, it but that pilots have done it and have
apparently suffered no ill effects. Unfortunately, I don't know of any
documents addressing this question directly.

Mike the Strike wrote:
On Feb 15, 10:18 am, "bumper" wrote:
"Eric Greenwell" wrote in message

...



And to reiterate, it's not a "200 watt transmitter". The peak power of
the pulses is 200 watt, but it's only about a 5 watt max transmitter,
as the pulses are short.
I know you are talking about peak power vs average power. However, even
though pulse width is narrow, and thus the average radiation from a 175 or
250 watt transponder might be on the order of 5 watts, I'm not sure the
radiation exposure should be equated to just the low average power.

Consider a single high powered pulse as being one .22 rifle bullet. The
bullet might have on the order of 100 ft pounds of energy and would
obviously do considerable tissue damage. Compare that to several hundred
BB's from a low powered air rifle, the combined energy of which equals the
energy of that one .22 bullet. Same total energy, far less damage. The point
I'm trying to make is that pulsed high energy may well do more tissue damage
than the same total amount of low level energy delivered over a longer time
frame.

I want that transponder antenna installed away from me.

bumper

A colleague who deals with radiation safety said that the argument
that low energy long-duration doses of radiation are equivalent to
high energy short duration doses is like equating jumping off a 3-foot
wall ten times with jumping off a 30-foot wall once.

Please ask your colleague if his analogy applies to microwave radiation.
Where I worked, "radiation safety" generally meant "atomic radiation
safety", including ionizing radiation (a bit like the bullet in bumper's
analogy) and gamma radiation. These tend to interact with tissue much
differently than microwave (radio) radiation.

--
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