"Neil Gould" wrote in message
t...
I don't know, but I would design the system that way. Even at the level of
integrated circuits, there are plug-in replacements for obsolete parts,
and I don't see any advantage to using unique components in this kind of
application.

Unfortunately, some of the people making the decisions in these companies
don't necessarily see it that way... I was looking for a way to hook up the
output from my Northstar M1A LORAN to my laptop a few years ago so that I
could use it as input to a situation awareness program that I was writing...
Although NMEA 0183 was used by all the handheld LORANs and GPSs at that
time, it seems that Northstar chose to use a proprietary format for the data
stream coming out of their unit... While talking with them, I learned that
this was not uncommon within the avionics industry... A system like the
Argus moving map had to be able to understand all the possible data formats
of the various units that it supported...

Standards are great if everyone agrees to support them... Supposedly FireFox
is a true W3C compliant browser (unlike MS's IE)... I've encountered various
web sites that do not work correctly with it, but they work with IE... It
seems that developers get sloppy in that IE allows them to get away with
things that are not W3C compliant... Hell, I've even had to go back and
modify some of my own web apps that I created in the pre-FireFox days to
make them work with FireFox... Luckily it's only been needing to add
"document.getElementById" for each field accessed by a JavaScript function
variable... It seems that IE allowed you to be lazy and not require this...

Oh well, I'm digressing... The point is, don't assume that companies will
make decisions that will give you the most flexibility... They have a vested
interest in tying you to their products... Even if they have a common
interface like the TCP/IP interface that Rockwell was using on the systems
that I worked on, it doesn't necessarily help unless there is a standardized
command packet format... Otherwise, you will find yourself with one device
that although physically able to talk to another device, they might not be
able to understand what each other are saying... With some devices, it might
not be that difficult to come up with a common message protocol that the
device could support, with others, this could be quite extensive... For
example, consider the following devices and what they might need:

ADF:
1. Set frequency
2. Get frequency
3. Get bearing to transmitter
4. Enable audio output
5. Disable audio output

Transponder:
1. Set squawk code
2. Get squawk code
3. Set current mode (standby, Mode-A, Mode-C, Mode-S)
4. Get current mode
5. Initiate IDENT
6. Get IDENT status

Of course, every unit would also need a "Get system health / status" message
for retrieval internal diagnostics... It would be *nice* to know when a
particular device could not be relied upon... grin

I would like to see a system where you could put the actual measuring
devices in one location and the panel only needed to contain the devices
that display the information... For example, you could buy a small 2"-4"
generic display that could be set to display the output for various types of
devices... If one of the displays was acting up, you could change another
display so that it would display the output from the particular measuring
device... One advantage of this might be that although you might have
redundant measuring devices, only one display for the pair might need to be
on the panel... A failed health check might cause an indication to the pilot
that the backup device needs to be made active... Maybe it would even be
possible to toggle between the two devices...

Hell, as long as we're at it, let's give it a panel mount plug so that we
can plug our laptop PC into it also... If you had the building blocks in
place with this sort of TCP/IP controlled devices, just think of what sort
of flexibility that you could get without having to buy a $20K+ avionics
package... Of course, my point of view is as a VFR pilot would would like
some of the capabilities of the flight director type systems, but are not
able (either from a monetary or a physical panel space point of view) to put
one in their aircraft...