Transponder Praise

On July 2 (a day with blue skies, a few scattered CUs and typical east
coast haze) a friend and I were thermalling our ASW-20 and ASW-19
sailplanes at 6,000 feet 3 miles SE of Blairstown, NJ (a clearly
marked glider port some 40 miles from Newark Airport and Teterboro
Airport). My Zaon MRX alerted us to traffic at our altitude 5 miles
away, which then rapidly closed on us. Despite our best efforts over
the next 30 seconds, neither my friend nor I saw anything approaching.
Then suddenly we saw a business jet in a 45-50 degree bank less than a
mile away. Apparently my transponder caused a TA on his TCAS, he
looked outside and saw our wings flashing, and he turned away from the
impending collision.

I realize not everyone flies in a high traffic area like that around
NY and PHL. But especially for my soaring friends who fly the
Governor’s Cup course, I strongly recommend you put a transponder in
your ship. They cost less than a glide computer, and while they won’t
tell you where you are, a transponder might just get you home someday…

-John

Transponders are a good thing.. when the other guy has TCAS or TIS
capability.
I would venture a guess it's 50-50 he never saw you and simply reacted to
the TA commands.
The small GA aircraft without a TIS display will still never see you.
BT


"jcarlyle" <jmcarlyle@**********> wrote in message
news:30c0c557-f35c-447d-ac49-759881440553@m3g2000hsc.************.com...
On July 2 (a day with blue skies, a few scattered CUs and typical east
coast haze) a friend and I were thermalling our ASW-20 and ASW-19
sailplanes at 6,000 feet 3 miles SE of Blairstown, NJ (a clearly
marked glider port some 40 miles from Newark Airport and Teterboro
Airport). My Zaon MRX alerted us to traffic at our altitude 5 miles
away, which then rapidly closed on us. Despite our best efforts over
the next 30 seconds, neither my friend nor I saw anything approaching.
Then suddenly we saw a business jet in a 45-50 degree bank less than a
mile away. Apparently my transponder caused a TA on his TCAS, he
looked outside and saw our wings flashing, and he turned away from the
impending collision.

I realize not everyone flies in a high traffic area like that around
NY and PHL. But especially for my soaring friends who fly the
Governor’s Cup course, I strongly recommend you put a transponder in
your ship. They cost less than a glide computer, and while they won’t
tell you where you are, a transponder might just get you home someday…

-John

On Jul 5, 11:27 pm, Soarin Again <shadowl...@yahoo.com> wrote:
> At 16:34 05 July 2008, jcarlyle wrote:
>
> > My Zaon MRX alerted us to traffic at our altitude 5 miles
> >away, which then rapidly closed on us. Despite our best
> >efforts over the next 30 seconds, neither my friend nor
> >I saw anything approaching.
> >Then suddenly we saw a business jet in a 45-50 degree
> >bank less than a mile away. Apparently my transponder
> >caused a TA on his TCAS, he looked outside and saw our
> >wings flashing, and he turned away from the impending collision.
>
> Assuming that you are talking nautical miles.  If you are alerted
> to the aircraft at 5 miles and within 30 seconds he is at 1 mile
> then is apparently doing 480 knots (well above the 250 kt limit
> below 10,000 msl).
> If you don't see him and you know he is at your altitude and
> closing at that high of a rate, why not just pull full spoilers and
> dive to vacate that altitude as quickly as possible?
> Is there a better option available?

The distance measurements with PCAS are approximate and only based on
radiated power from the other aircraft's transponder and can be fooled
as the aircraft change atitudes/altirudes relateive to each other.

With two gliders flying near each other and both thermalling (so that
you are most visible to other traffic) I'd be trying to stay with the
other glider (traffic might see and try to avoid one glider and hit
the other), I'd be focused on scanning for the traffic and not be
shoving the nose over and pulling spoilers unless I could see the
traffic and thought that was a good thign to do. If traffic is
getting close on PCAS and I can't see it I will bank or turn the
glider to have a good look around.


Darryl

jcarlyle <jmcarlyle@**********> wrote in news:286ac151-8584-4de5-8eac-
1e832ed09182@m36g2000hse.************.com:

[snip]
> visible to them, and allows me to look at what was my 6 o’clock. I
> also tend to get more vigilant when I’m nearing a VOR as well as when
> I'm flying at a multiple of 1000 feet, as I figure other traffic tends
> to fly at those locations and altitudes.
>
Keeping a sharp eye out around VOR's is good. Avoiding VOR's is probably
better. Still a lot of traffic without GPS out there.

Assuming you're in the USA: IFR traffic will be on the 1000's, VFR will be on
the 500's. Within 3000 AGL all bets are off.

--
---
there should be a "sig" here

Eric, I wasn't too impressed with the antenna extenders that Zaon
offers. They use RG-174 cable, and while it's OK for short runs it
would markedly decrease the signal strength running from my tail cone
to my instrument panel. I've found several places on line that offer 6
meter male to female RP SMA cables made from LMR 200 for less than
$15. The attenuation with LMR 200 at 1 GHz is 10 dB per 100 feet,
rather than the 22 dB per 100 feet with RG-174.

I guess there's a possibility that high interrogation rates could mess
up the Zaon range estimate, but even here in the PHL NY area the
transponder's transmitting triangle only flashes about once a second.
Could be that there are many, many transmissions per flash, but I've
noticed that generally if the Zaon says the range is within 3 miles of
me it is pretty accurate (to my "calibrated" eye, that is).

-John

On Jul 7, 2:39 pm, Eric Greenwell <flyguy...@verizon.netto> wrote:
> Shadowing is certainly a possibility. I've also wondered if the amount
> of radar interrogations can cause the same thing; e.g., where I fly in
> SE Washington state, my transponder is triggered only 5-10 times a minute.
>
> Rather than just relocating the antenna, you can get Zaon's dual antenna
> option. That puts antennas top and bottom on the aircraft, essentially
> eliminating all shadowing. It might be easier than moving one antenna to
> the tail, but it's pricey at $280 for the option, plus two blade antennas.
>
> --
> Eric Greenwell - Washington State, USA

You're absolutely correct on the heights! Since most of my close calls
have come from IFR traffic, though, I tend to become more antsy at
multiples of 1000. Doesn't mean I let down my guard at other
altitudes...

-John

On Jul 7, 11:31 pm, Clark <c...@uswest.net> wrote:
> Keeping a sharp eye out around VOR's is good. Avoiding VOR's is probably
> better. Still a lot of traffic without GPS out there.
>
> Assuming you're in the USA: IFR traffic will be on the 1000's, VFR will be on
> the 500's. Within 3000 AGL all bets are off.