"A Guide to Transponders in Sailplanes" - updated!

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

"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 14, 9:59*pm, Mike the Strike wrote:
On Feb 14, 9:42 pm, Mike the Strike wrote:
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.

The report I read said the transponder was not turned on because the
transponder installation was not certified. Did you hear different?

It is illegal to operate a transponder without current certification.

Andy

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

On Feb 15, 1:56 pm, Andy wrote:
On Feb 14, 9:59 pm, Mike the Strike wrote:

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

The report I read said the transponder was not turned on because the
transponder installation was not certified. Did you hear different?

It is illegal to operate a transponder without current certification.

Andy

The report I read said the operator was not familiar with the
instruments and was concerned about battery drain. I don't know if
someone operating a ship not their own would even worry about
certification.

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.

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.

On Feb 14, 8:59 pm, Mike the Strike wrote:
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.

That's not what stops pilots - it's the $1000 battery that stops them.
Many gliders require and additional battery when a transponder is
installed, and doing this in certified glider can be expensive.
Experimental certificate gliders can usually get by more cheaply.

A dedicated 7 Ah
battery will power a Microair transponder for 12 to 15 hours, in my
experience. This is a no-brainer.

That is the solution I recommend, but see the cost of implementing it
stops some pilots from adding another battery. A 7 AH battery won't
run a vario, radio, gps, AND a full-time transponder for very long.


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.

And we are all agreed that if that was actually the case, it was a
very foolish decision, because that is a prime area for using a
transponder. But answer this: if that glider had not had a
transponder, would the jet have hit it more gently? He was not
required to have one, after all.

That's not what stops pilots - it's the $1000 battery
that stops them.


Change your two 7ah batteries for readily available
9ah batteries that fit in the same hole at about $25
each. Job done.

No certification / inspector etc needed