Warning to users of Zaon PCAS MRX

On Feb 19, 9:28*pm, Eric Greenwell wrote:
Bruno wrote:
On Feb 19, 8:07 pm, Eric Greenwell wrote:

Bruno wrote:

I have now had my unit fail twice without any indication of failure.
It still seemed to be working fine until I saw a jet whiz by real
close and realized that I hadn't had any alerts for a flight or two.
Again, the unit turned on and seemed to be acting fine. *I sent it
back to Zaon and they were great and replaced the board to fix it the
first time.

Do you know if a failed unit like yours can still pick up the glider's
own transponder? If it cannot, that would give transponder equipped
gliders an easy way to test their MRX.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

I have a transponder and no you don't pick up yourself. *After reading
Randy's reply I think this problem might be a little more wide spread.
Glad to be getting the word out. *Bruno - B4

OK, pilots with transponders can check their unit without needing
another plane around; of course, they still have be interrogated by
ground radar or a TCAS system within 10 miles or so (not sure what the
range is). If your MRX isn't picking up your transponder AND you can see
the transponder is replying, then the MRX is likely bad. Contact the
factory about it.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

In case people don't know how to do this. Push on the multifunction
button on the left to get to the "Local" screen to see what the MRX
thinks is your local transponder squawk code and altitude, either from
the internal altimeter or transponder (read you user manual).

BTW it should be possible at least in principle for the MRX to know
the local transponder altitude but not the squawk code - e.g. if the
local Mode C transponder is being interrogated by an airborne TCAS
which make Mode C but not Mode A interrogations (so the transponder
does not get asked to transmit its squawk code. This might happen when
on the ground or at low altitude where there are no SSR
interrogations. Since the MRX is a black-box it's unclear exactly what
it does here. It would be interesting to check if the MRX can show
this situation outside SSR coverage.

If your glider does not have a transponder and your towplane does it
is possible that the MRX will think the towplane transponder is your
own (until you get off tow and the altitude difference between what it
thinks is the local transponder and its internal altimeter become too
large). It may also be possible that even if you have a local
transponder that the MRX still thinks the towplane tranponder is
yours. So you might see things like intermittent alerts that comes or
go or an alert for the tow plane once you get off tow, but not while
on tow.

It is also possible that the MRX (or any other PCAS unit) gets
confused by transponders both in the tow plane and glider replying to
interrogations (what's called synchronous garbling). TCAS (and SSR)
systems try to de-garble several overlapping signals like this but it
is unclear what the MRX can actually do there, if anything.

I think the MRX PCAS is a great safety/traffic awareness enhancement
and I've flow with them from soon after they were first available. I
have great experience with Zaon customer support. I broke my MRX
antenna off while swinging my leg over the top of my instrument
pedestal and I sent the unit in to have that fixed and have the unit
upgraded with a headphone jack and they did this a reasonable cost (I
can't remember exactly how much they charged) and they fixed the
antenna and also threw in a free spare one.


Darryl