175 or 250 watt transponder? [Archive]

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Itsaplane

January 8th 09, 08:01 PM

Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except > 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)

Mike[_8_]

January 8th 09, 08:17 PM

On Jan 8, 1:01*pm, Itsaplane > wrote:
> Needing a replacment, my transponder shop told me that above 15k' the
> FAR's require a 250 watt transponder (125w below 15k').
>
> True?
>
Eric,

Have you tried Freeflight?

http://www.freeflightsystems.com/index.htm

Mike

> I'm pretty sure that sailplane owners are mostly installing 175 watt
> units and flying them to 18k' (and higher in wave windows). *Right?
>
> If this 15k' rule is real, I'm supposing that, since gliders aren't
> required to have a transponder except in certain airspace (this
> airspace is all below 15k' -- except Class A...) that we're generally
> free to install anything we want (except > 18k' in Class A?).
>
> Bottom line -- 175 watts or 250 watts?
>
> Eric Rupp
> ER
> (My Terra TR250D transponder is inop and I'm having trouble getting
> parts - anybody have a dead one that we might be able to salvage from?)

John Smith

January 8th 09, 08:20 PM

Bottom line: If you want to fly above 15k in airspace where a
transponder is mandatory, then 250W is required or you will not fly
there. Otherwise install whatever you want. As there is little
difference in price as well as in power consumtion, I don't see why you
would want to go for the weaker unit, though.

A side note: If you want to stick with a mode C transponder, then there
are a lot of used ones available in Europe pretty cheaply, as Europe is
mandating mode S now and everybody must switch. If on the other hand you
want to buy a new unit, then go for mode S. It doesn't cost much more,
it draws less current and it will have a much better resell value.

Richard[_9_]

January 8th 09, 08:21 PM

Ramy

January 8th 09, 08:42 PM

On Jan 8, 12:17*pm, Mike > wrote:
> On Jan 8, 1:01*pm, Itsaplane > wrote:> Needing a replacment, my transponder shop told me that above 15k' the
> > FAR's require a 250 watt transponder (125w below 15k').
>
> > True?
>
> Eric,
>
> Have you tried Freeflight?
>
> http://www.freeflightsystems.com/index.htm
>
> Mike
>
>
>
> > I'm pretty sure that sailplane owners are mostly installing 175 watt
> > units and flying them to 18k' (and higher in wave windows). *Right?
>
> > If this 15k' rule is real, I'm supposing that, since gliders aren't
> > required to have a transponder except in certain airspace (this
> > airspace is all below 15k' -- except Class A...) that we're generally
> > free to install anything we want (except > 18k' in Class A?).
>
> > Bottom line -- 175 watts or 250 watts?
>
> > Eric Rupp
> > ER
> > (My Terra TR250D transponder is inop and I'm having trouble getting
> > parts - anybody have a dead one that we might be able to salvage from?)- Hide quoted text -
>
> - Show quoted text -

Freeflight does no service the Terra transponder, but Gulf Coast
Avionics in Lakeland , Florida does . They can be reached at
863-709-9714.

Ramy

Darryl Ramm

January 8th 09, 09:04 PM

Darryl Ramm

January 8th 09, 10:09 PM

On Jan 8, 12:21*pm, Richard > wrote:
> On Jan 8, 12:01*pm, Itsaplane > wrote:
>
>
>
> > Needing a replacment, my transponder shop told me that above 15k' the
> > FAR's require a 250 watt transponder (125w below 15k').
>
> > True?
>
> > I'm pretty sure that sailplane owners are mostly installing 175 watt
> > units and flying them to 18k' (and higher in wave windows). *Right?
>
> > If this 15k' rule is real, I'm supposing that, since gliders aren't
> > required to have a transponder except in certain airspace (this
> > airspace is all below 15k' -- except Class A...) that we're generally
> > free to install anything we want (except > 18k' in Class A?).
>
> > Bottom line -- 175 watts or 250 watts?
>
> > Eric Rupp
> > ER
> > (My Terra TR250D transponder is inop and I'm having trouble getting
> > parts - anybody have a dead one that we might be able to salvage from?)
>
> Eric,
>
> I don't believe that is true. *I think that is from the specifications
> from the Becker transponders. * The Microair T2000 *is 200w and specs
> say 62,000 feet.
>
> http://www.craggyaero.com/microair.htm
>
> Richardwww.craggyaero.com

Yes it's true, but it's also not...

The above/below 15,000' comes from TSO-C74c see
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgTSO.nsf/0/ACBBA541FF4C071D86256DC10067F209?OpenDocument

See other specifications there to explain the differences, but for
power output the TSO requirments are

---QUOTE---

2.11 Transmitter Power Output.

a. For equipment intended for installation in aircraft which operate
at altitudes above 15,000 feet, the peak pulse power available at the
antenna end of the transmission line of the transponder must be at
least 21 db and not more than 27db above 1 watt at any reply rate up
to 1,200 per second for a 15-pulse coded reply.

b. For equipment intended for installation in aircraft which operate
at altitudes not exceeding 15,000 feet, the peak pulse power available
at the antenna end of the transmission line of the transponder must be
at least 18.5db and not more than 27db above 1 watt at any reply rate
up to 1,200 per second for a 15-pulse coded reply.

c. The standards of this section assume a transmission line loss of
3db and an antenna performance equivalent to that of a simple quarter
wave antenna. In the event that these assumed conditions do not apply,
the equipment must be adjusted as necessary to provide a transmitter
power output equivalent to that specified.
---END QUOTE---

But how to interpret this? The way I read these TSO requirements are -

below 15k feet 18.5dbW to 27dBW = 70.8W to 501W power at coax output
at the antenna
above 15k feet 21dbW to 27dBW = 126W to 501W power at coax output at
the antenna

below 15k feet 18.5dbW+3dB to 27dBW+3dB = 141W to 1kW power at
transponder output
above 15k feet 21dbW+3dB to 27dBW+3dB = 251W to 1kW power at
transponder output

Where I have assumed the 3dB cable loss in part(c).

I'm not aware of any requirement for what power output manufactures
are required to quote. Are they talking about the power output at the
transponder or the TSO-C74c specified power at the antenna input with
assumed 3dB cable loss? I suspect manufactures normally want to quote
the biggest power output they can however in the case of Microair I
assume they are talking about 200W at the antenna coupling since they
would not meet the ~250W requirement. Maybe one of their dealers can
clarify this. (and yes technically as well there is ambiguity about
peak vs. other power measurements, but again I'd assume manufactures
are going to quote peak to maximize the number and since that is also
what the TSO talks about).

Anybody got a different interpretation of the TSO?

Darryl

Tim Mara[_2_]

January 8th 09, 10:29 PM

the transponder manufacturer (Becker) "recommends" 250 Watt above 15,000'
but to the best of my knowledge there is no FAA requirement for transponder
power
tim

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

"Richard" > wrote in message
...
On Jan 8, 12:01 pm, Itsaplane > wrote:
> Needing a replacment, my transponder shop told me that above 15k' the
> FAR's require a 250 watt transponder (125w below 15k').
>
> True?
>
> I'm pretty sure that sailplane owners are mostly installing 175 watt
> units and flying them to 18k' (and higher in wave windows). Right?
>
> If this 15k' rule is real, I'm supposing that, since gliders aren't
> required to have a transponder except in certain airspace (this
> airspace is all below 15k' -- except Class A...) that we're generally
> free to install anything we want (except > 18k' in Class A?).
>
> Bottom line -- 175 watts or 250 watts?
>
> Eric Rupp
> ER
> (My Terra TR250D transponder is inop and I'm having trouble getting
> parts - anybody have a dead one that we might be able to salvage from?)

Eric,

I don't believe that is true. I think that is from the specifications
from the Becker transponders. The Microair T2000 is 200w and specs
say 62,000 feet.

http://www.craggyaero.com/microair.htm

Richard
www.craggyaero.com

Eric Greenwell

January 8th 09, 10:33 PM

John Smith wrote:
> Bottom line: If you want to fly above 15k in airspace where a
> transponder is mandatory, then 250W is required or you will not fly
> there.

Do you have a reference to the regulation concerning power requirement?
I haven't been able to find it, and people just seem to rely on the
product descriptions when I ask about it.

hough.
>
> A side note: If you want to stick with a mode C transponder, then there
> are a lot of used ones available in Europe pretty cheaply, as Europe is
> mandating mode S now and everybody must switch. If on the other hand you
> want to buy a new unit, then go for mode S. It doesn't cost much more,
> it draws less current and it will have a much better resell value.

Can you tell me which Mode S transponder you are talking about? The ones
that I see for sale in the USA are much more expensive ($600 comparing
the 175W and 150W models of Becker; $1100 comparing the 250W models of
Becker).

--
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

Alan[_6_]

January 9th 09, 08:17 AM

In article > Darryl Ramm > writes:
>On Jan 8, 12:21=A0pm, Richard > wrote:
>> On Jan 8, 12:01=A0pm, Itsaplane > wrote:
>> > Needing a replacment, my transponder shop told me that above 15k' the
>> > FAR's require a 250 watt transponder (125w below 15k').
>>
>> > I'm pretty sure that sailplane owners are mostly installing 175 watt
>> > units and flying them to 18k' (and higher in wave windows). =A0Right?
>>
>> > Bottom line -- 175 watts or 250 watts?
>>
>> > Eric Rupp
>> > ER

>Yes it's true, but it's also not...
>
>The above/below 15,000' comes from TSO-C74c see
>http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgTSO.nsf/0/ACB=
>BA541FF4C071D86256DC10067F209?OpenDocument
>
>See other specifications there to explain the differences, but for
>power output the TSO requirments are
>
>---QUOTE---
>
>2.11 Transmitter Power Output.
>
>a. For equipment intended for installation in aircraft which operate
>at altitudes above 15,000 feet, the peak pulse power available at the
>antenna end of the transmission line of the transponder must be at
>least 21 db and not more than 27db above 1 watt at any reply rate up
>to 1,200 per second for a 15-pulse coded reply.
>
>b. For equipment intended for installation in aircraft which operate
>at altitudes not exceeding 15,000 feet, the peak pulse power available
>at the antenna end of the transmission line of the transponder must be
>at least 18.5db and not more than 27db above 1 watt at any reply rate
>up to 1,200 per second for a 15-pulse coded reply.
>
>c. The standards of this section assume a transmission line loss of
>3db and an antenna performance equivalent to that of a simple quarter
>wave antenna. In the event that these assumed conditions do not apply,
>the equipment must be adjusted as necessary to provide a transmitter
>power output equivalent to that specified.
>---END QUOTE---
>
>But how to interpret this? The way I read these TSO requirements are -
>
>below 15k feet 18.5dbW to 27dBW =3D 70.8W to 501W power at coax output
>at the antenna
>above 15k feet 21dbW to 27dBW =3D 126W to 501W power at coax output at
>the antenna
>
>below 15k feet 18.5dbW+3dB to 27dBW+3dB =3D 141W to 1kW power at
>transponder output
>above 15k feet 21dbW+3dB to 27dBW+3dB =3D 251W to 1kW power at
>transponder output
>
>Where I have assumed the 3dB cable loss in part(c).

I am sure I quoted way too much.

The guide says you can use the real cable loss if it isn't 3 dB. That makes
life easier for most with gliders, as a short length of low loss cable will do
better than 3 dB.

175 watts is 1.43 dB above the 21 dBW requirement for use above 15,000 feet.
So you simply need to get the loss below 1.43 dB in the feedline. That appears
to be not very difficult. For example, Times Microwave LMR240 cable shows up
as a total loss of 1.07 dB when connected to a load with an SWR of 1.5:1. It
takes 16 feet of this cable to get the loss to 1.42 dB.

If that is cutting it too close, you can get a better matching antenna, or
use a lower loss cable. At 1.2:1 SWR, that same 16 feet of LMR240 has a total
loss of 1.36 dB. LMR400 cuts the loss to 0.74 dB even with a 1.5:1 SWR. (It
has 0.69 dB loss for 16 feet with a perfect match at the end.)

Unfortunately, many aircraft installations use smaller lighter and more
flexible coax -- such as RG58, which will give 1.9 - 2.9 dB loss (too much).
(There is a lot of variety in types of RG58.)

Alan
wa6azp

John Smith

January 9th 09, 09:12 AM

Eric Greenwell wrote:

> Do you have a reference to the regulation concerning power requirement?
> I haven't been able to find it, and people just seem to rely on the
> product descriptions when I ask about it.

Actually, I do, too. I see no reason not to believe the manufactorers.
According to Funkwerk, output requirements are higher for tansponders
which are operated in aircraft flying at altitudes above 15,000ft or
speeds above 175kt. Unfortuately (of fortunately), gliders often operate
higher than 15,000ft.

I write this with the European situation in mind where Mode S is already
mandatory. As air traffic is typically an international thing, I would
assume that the FAA and EASA have been reasonable enough to discuss this
and to agree to the same requirements.

BTW, problably not the cheapest but one of the more popular mode S
transponders in Europe is the TRT800H by Funkwerk.
http://www.funkwerk-avionics.com/cms/front_content.php?idcat=47&idartlang=229&OldParentId=34&changelang=4

Darryl Ramm

January 9th 09, 01:35 PM

On Jan 9, 12:17 am, (Alan) wrote:
> In article > Darryl Ramm > writes:
[snip]
> The guide says you can use the real cable loss if it isn't 3 dB. That makes
> life easier for most with gliders, as a short length of low loss cable will do
> better than 3 dB.
>
> 175 watts is 1.43 dB above the 21 dBW requirement for use above 15,000 feet.
> So you simply need to get the loss below 1.43 dB in the feedline. That appears
> to be not very difficult. For example, Times Microwave LMR240 cable shows up
> as a total loss of 1.07 dB when connected to a load with an SWR of 1.5:1. It
> takes 16 feet of this cable to get the loss to 1.42 dB.
>
> If that is cutting it too close, you can get a better matching antenna, or
> use a lower loss cable. At 1.2:1 SWR, that same 16 feet of LMR240 has a total
> loss of 1.36 dB. LMR400 cuts the loss to 0.74 dB even with a 1.5:1 SWR. (It
> has 0.69 dB loss for 16 feet with a perfect match at the end.)
>
> Unfortunately, many aircraft installations use smaller lighter and more
> flexible coax -- such as RG58, which will give 1.9 - 2.9 dB loss (too much).
> (There is a lot of variety in types of RG58.)
>
> Alan
> wa6azp

Lets drill into this more...

Alan raises a good point by talking about a practical installation.

Since the approval agency doing the TSO (or equivalent) approval won't
know the actual cable loss of a particular installation they are going
to have to assume 3dB. And changing cable losses in a practical
installation won't change the transponder TSO-C47c approval type. It's
called out in the approval doc and required to be marked on the
transponder, etc. So I don't see how a manufacturer can avoid meeting
the +3dB power requirements. Which means that Microair is quoting the
3dB corrected theoretical antenna input power on their TSO Type 1A
approved transponder or I'm misunderstanding something.

A Type 1B transponder with lower power output might be just as good
for our uses in practice as a Type 1A (above 15000' spec) especially
with a good antenna installation and as Alan points out may meet the
power requirements of a Type 1A transponder. Which might all make some
pilots less concerned about worrying about all this in practice,
especially if a Type 1B transponder draws less power battery power
than a type 1A. But would that be legal? And does the transponder
Type approval really matter to us? Well FAR 91.215(a) might come to
our rescue...

---QUOTE---
(a) All airspace: U.S.-registered civil aircraft. For operations not
conducted under part 121 or 135 of this chapter, ATC transponder
equipment installed must meet the performance and environmental
requirements of any class of TSO-C74b (Mode A) or any class of TSO-
C74c (Mode A with altitude reporting capability) as appropriate, or
the appropriate class of TSO-C112 (Mode S).
---END QUOTE---

Note - that's just a "must meet the performance of" not a "must be TSO
approved". So this leaves open the possibility (especially for
experimental gliders, and Eric's glider is experimental) that you can
legally use a transponder outside its TSO Type altitude limits. One
gate to this would obviously be that the tests required under FAR
91.413 (ie. Part 43 Appendix F which circle back to the TSO specs)
must show that it did meet the Type 1A (above 15,000') requiremnts.
Who knows for sure whether the FAA would ever argue that you would
have to do more than that with a modern Type 1B transponder to show
"must meet the [1A] performance". But I'd be pretty surprised to see
this being an issue in practice.

It would be great to hear if other people have different
interpretations of the TSO and FAR requirements.

(I've deliberately kept this to Mode-C, not Mode-S, transponders here
since that what I think Eric is looking at).

The important practical thing, especially in high traffic areas, is to
have a transponder installed and turned on. If a lower power
consumption transponder is important to extend battery life then I'd
personally rather see people install that than turn off the
transponder during flight. Of course there may be options to install
more battery capacity, etc.

Darryl

Darryl Ramm

January 9th 09, 02:41 PM

On Jan 9, 5:35*am, Darryl Ramm > wrote:
> On Jan 9, 12:17 am, (Alan) wrote:
> > In article > Darryl Ramm > writes:
> [snip]
>
> Since the approval agency doing the TSO (or equivalent) approval won't
> know the actual cable loss of a particular installation they are going
> to have to assume 3dB. And changing cable losses in a practical
> installation won't change the transponder TSO-C47c approval type. It's
> called out in the approval doc and required to be marked on the
> transponder, etc. So I don't see how a manufacturer can avoid meeting
> the +3dB power requirements. Which means that Microair is quoting the
> 3dB corrected theoretical antenna input power on their TSO Type 1A
> approved transponder or I'm misunderstanding something.
[snip]
> Darryl

And I'll answer my own self-doubt about how Microair can have a Type
1A 200W transponder. Microair state in their installation manual "The
T2000SFL allows for 1.5dB cable loss from the unit to the antenna.".
That gets incorporated as a part of the TSO and supplants the generic
3dB assumption in the TSO and so I'm sure they are talking about
actual output power from the transponder being 200W.

Darryl

Bob Kuykendall

January 9th 09, 06:05 PM

On Jan 9, 1:12*am, John Smith > wrote:

> Actually, I do, too. I see no reason not to believe the manufactorers...

I have this bridge for sale...

kd6veb

January 9th 09, 06:09 PM

Hi Gang
This is what I call a weird discussion. Why? Think about it all of
you. How many of you know the difference in DBs between the 2 power
levels? Is it a very large number or a very small number? If it is a
very small number is it significant? One last question how accurate a
piece of measuring equipment would you need to have to distinguish
between the 2 power levels? Be honest each of you. Without seeing any
other responses to my post, post your answers to my 4 questions.
A clue! If you answer the 4 questions correctly you won't waste your
time ever discussing this subject again period! My low power watt
Beckers on each of my flying 3 machines (Stemme, LSA and ultralight
SparrowHawk) are just fine, thank you, for going to any altitude I
choose to. No one but no one (meaning ATC) could ever tell whether I
had a low or high power transponder! And, of course, neither could you
without checking the power levels under lab conditions.
Dave

Bob Thompson

January 9th 09, 06:25 PM

This is an interesting thread because I'm also considering the
purchase of a transponder.
Unfortunately, it's necessary to pay attention to what's legal in
addition to what does the job.
If for any reason you bump into someone at 16K (and wouldn't I love to
get there) you can bet that the NTSB and the other guy's lawyer will
know the difference.

Andy[_1_]

January 9th 09, 06:27 PM

On Jan 9, 11:25*am, Bob Thompson > wrote:
> If for any reason you bump into someone at 16K (and wouldn't I love to
> get there) you can bet that the NTSB and the other guy's lawyer will
> know the difference.

Bumping into someone at 16 k is not legal. You're screwed anyway.

Andy

Eric Greenwell

January 9th 09, 06:30 PM

John Smith wrote:
> Eric Greenwell wrote:
>
>> Do you have a reference to the regulation concerning power
>> requirement? I haven't been able to find it, and people just seem to
>> rely on the product descriptions when I ask about it.
>
> Actually, I do, too. I see no reason not to believe the manufactorers.
> According to Funkwerk, output requirements are higher for tansponders
> which are operated in aircraft flying at altitudes above 15,000ft or
> speeds above 175kt. Unfortuately (of fortunately), gliders often operate
> higher than 15,000ft.

My problem is the manufacturers do not specifically say their 250W
transponders are required by the FAA, in gliders, above 15,000'. They
often refer to EASA or other regulations that just hint at it, or make
non-specific remarks that may apply only to certified airplanes. It
looks like Darryl has found what I want, however.
>
> I write this with the European situation in mind where Mode S is already
> mandatory. As air traffic is typically an international thing, I would
> assume that the FAA and EASA have been reasonable enough to discuss this
> and to agree to the same requirements.

And they probably have, for international operations, but for gliders in
just the USA? Or in a wave window? We should not assume anything about
in-country requirements, because regulations do vary. Note that Europe
is going to Mode S and 8.33 radio channel spacing; the USA is not.

> BTW, problably not the cheapest but one of the more popular mode S
> transponders in Europe is the TRT800H by Funkwerk.
> http://www.funkwerk-avionics.com/cms/front_content.php?idcat=47&idartlang=229&OldParentId=34&changelang=4

I know there are many choices in Europe for Mode S, but I am aware of
only two brands sold in the USA that have units suitable for gliders:
Becker and Garrecht. The least costly is still $600 more than a Mode C unit.

If the Mode S units had a significantly lower power requirement, they
might be worth the extra money. Comparing the datasheets of the Becker
models, both the standby and operating drains seem similar. Perhaps I am
misinterpreting the figures.

The Garrecht unit seems to promise a worthwhile reduction in drain, in
part because it does not require an external encoder. It costs almost
$1000 more than a Becker + encoder, however.

Perhaps some enterprising soaring supply company should buy a lot of
those unusable Mode C transponders from Europe and offer them for sale
to USA customers at attractive prices.

--
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

Darryl Ramm

January 9th 09, 07:14 PM

On Jan 9, 10:25*am, Bob Thompson > wrote:
> This is an interesting thread because I'm also considering the
> purchase of a transponder.
> Unfortunately, it's necessary to pay attention to what's legal in
> addition to what does the job.
> If for any reason you bump into someone at 16K (and wouldn't I love to
> get there) you can bet that the NTSB and the other guy's lawyer will
> know the difference.

I think the NTSB and FAA gave shown sensible restraint here. For
example in how they handled questions of transponder non-usage with
the Minden Hawker/ASG-29 mid-air collision. I believe they get the
need to focus on getting gliders to have transponders installed and
used in high traffic areas and I suspect they realize that other
actions they take at times could hurt that overall effort. But that's
just my impression.

To Dave's point I agree this technically a very silly thing to worry
about (which I tried to say earlier), and I also like the 175W Becker
transponder and highly recommend it. [So Dave please stop reading
now :-)] On the other hand when we get into these things about what's
legal etc. Lets actually get into the TSOs, FARs etc. what *exactly*
are the requirements. Otherwise we end up in even less useful
discussion about what people think with no proof points to validate
from. Hopefully some requiremtns are now clearer to folks but you can
also see its actually *not* clear that we need a TSO'ed Type 1A
transponder above 15,000' (just one that meets the TSO requirements,
but again however that is supposed to be determined). My personal
opinion is I'd ask a repair shop to install the Becker 175W
transponder and if it passes the install test I'm happy.

Back to worry about FAA action. I'm going out on a limb here (and I am
definitely not an aviation or any other kind of lawyer) but for FAA to
raise issues that a Type 1B transponder that during calibration checks
met the Type 1A power output yet was not acceptable for use under FAR
91.413 above 15,000' would raise the issue that the calibration tests
themselves really are not sufficient for checking the entire US fleet
of Type 1A transponders for their compliance with requirements. I'd be
kind of surprised the FAA wanted to go there. And more importantly
again I suspect they get the focus needs to be in getting transponders
installed.

BTW I much prefer the Becker Transponder (which I've installed in my
DG-303 and ASH-26E) from a usability viewpoint to other models,
especially the Microair (which is in rental gliders I fly). Other
people may disagree.

Darryl

DRN

January 9th 09, 07:16 PM

On Jan 9, 1:09*pm, kd6veb > wrote:
>* This is what I call a weird discussion. Why?

Because it is RAS: Rampant Aviation Speculation. (with many DB)

But you already knew that ;-)

Richard[_9_]

January 9th 09, 07:26 PM

On Jan 8, 12:01*pm, Itsaplane > wrote:
> Needing a replacment, my transponder shop told me that above 15k' the
> FAR's require a 250 watt transponder (125w below 15k').
>
> True?
>
> I'm pretty sure that sailplane owners are mostly installing 175 watt
> units and flying them to 18k' (and higher in wave windows). *Right?
>
> If this 15k' rule is real, I'm supposing that, since gliders aren't
> required to have a transponder except in certain airspace (this
> airspace is all below 15k' -- except Class A...) that we're generally
> free to install anything we want (except > 18k' in Class A?).
>
> Bottom line -- 175 watts or 250 watts?
>
> Eric Rupp
> ER
> (My Terra TR250D transponder is inop and I'm having trouble getting
> parts - anybody have a dead one that we might be able to salvage from?)

Eric,

There must be no soaring anywhere that RAS members live. I am amazed
at where this thread has gone.

Buttom line the vast majority of the transponders sold in the USA for
sailplanes are Mircoair T2000, Becker 175w and Becker 250W (less of
these).

IMHO any one of these will be sufficient and relaible at the altitudes
that sailplanes fly, use with an ACK A-30 encolder (less power draw
than the Amer-King encoder and smaller). The Microair is shorter that
the Becker. Both fit in a 2.25" hole. My customers have had good
results with all.

Decide what you want to pay and any of the above will be
satisfactory.

The Garrecht is not a good idea in the USA because it is not certified
in the USA, also the lead time is 6 months.

Mode S is more expensive and I would not spend the money. Becker Mode
S are available in the USA.

Richard
www.craggyaero.com

DRN

January 9th 09, 08:09 PM

On Jan 9, 2:16*pm, DRN > wrote:
> Because it is RAS: Rampant Aviation Speculation. (with many DB)

Correction, that should be DBA ;-)

Greg Arnold[_2_]

January 9th 09, 08:26 PM

Bob Thompson wrote:
> This is an interesting thread because I'm also considering the
> purchase of a transponder.
> Unfortunately, it's necessary to pay attention to what's legal in
> addition to what does the job.
> If for any reason you bump into someone at 16K (and wouldn't I love to
> get there) you can bet that the NTSB and the other guy's lawyer will
> know the difference.

As long as the transponder signal was picked up by ATC and the bumpee's
TCAS, I doubt if the transponder issue would be relevant from a legal
standpoint. If the signal wasn't picked up, then it might be relevant,
though I don't understand why the signal wouldn't be picked up --
someone flying at 18,000' will never be more than 3000' farther from the
ATC radar than someone flying at 15,000'. A 3000' variance in distance
shouldn't make a significant difference in the strength of the signal.
Maybe this would become an issue if you were flying at 35,000', and were
directly above the ATC radar.