On Feb 14, 11:27*am, Mxsmanic wrote:
Dave writes:
Just to throw in *.02 re your TCAS comment..................

We have the ZAON XRX on board our Cherokee in a VERY busy environment
(100,000 operations /yr)

I cannot begin to tell you how useful this tool is in tracking
trafffic around us

For $1500 !

The Sandel ST3400 is a TAWS/RMI display that also includes TCAS capability,
with a fancy back-projected LCD display. That's probably why it is so
expensive. I suppose TCAS alone is a lot cheaper.

I looked at the ZAON XRX on their Web site and it looks like a pretty
practical gadget.

The Sandel ST3400 is a display for TCAS. The Sandel does not "include
TCAS" as seems to be implied here.

TCAS I systems start at ~$20k for GA aircraft, not including displays
and other critical components, and for TCAS II in a transport category
aircraft can go to prices you can buy a nice house.

The Zaon MRX and XRX are quire different than TCAS so I'm not sure why
this thread was renamed TCAS. They are examples of PCAS (Portable/
Passive Collision Avoidance Systems) systems not TCAS, i.e. to start
with they don't actively interrogate transponders, instead relying on
listening to replies to interrogations from ground SSR, and airborne
TCAD and TCAS systems. TCAD systems (e.g. the L3 Skywatch) do active
interrogations but are less sophisticated and capable than TCAS
systems, although some of the newer high-end versions of what have
traditionally been TCAD systems are meeting TCAS I requirements. Of
all these systems only TCAS II issues a resolution advisory (RA) (i.e.
instruction to climb/descend to avoid traffic, which override ATC
clearances/instructions). PCAS, TCAD and TCAS I and II acronyms are
pretty much widely accepted (TCAS I and II have very specific
meanings), quite different in technology/capabilities are usually
worth carefully differentiating between.

To the previous post, I agree that PCAS systems are very useful low
cost ways of improving traffic awareness, and I fly with a Zaon MRX
(and transponder) in my motorglider. However as with all systems it
helps to know of their limitations. For PCAS this starts with (1.)
they can only detect Mode C or Mode S transponder equipped aircraft,
(2.) that are actively being interrogated by another source (luckily
there are usually lots of those interrogators out there).

Darryl