Re: FAA To Finally Ditch Floppy Disks & Win-95

c186282 <c186282@nnada.net> wrote:

On 6/14/25 12:34 PM, Rich wrote:

c186282 <c186282@nnada.net> wrote:

On 6/13/25 11:35 PM, rbowman wrote:

On Fri, 13 Jun 2025 22:38:38 -0400, c186282 wrote:
>
>

     In any case it's become very clear that a major update is needed for
     the US airport/routing system. Knowing the govt process, the stuff
     will already be obsolete by the time it's installed, but not nearly
     SO obsolete.

>
In the early '70s we had a contract to build the controllers for the ALS
system. The heart of the controller was an Eagle Signal electromechanical
stepping switch which was pretty much obsolete. The harnesses had to be
laced since the FAA wasn't sure about those new-fangled nylon cable ties.

>
   Ooooh ! Nylon ! EVIL !!!   :-)

 
Not so much that as: Ooooh!, we don't know how well this new "tie"
method will withstand extremes of cold, hot and vibration, and the
current regs.  specify "laced" and we *do* know how lacing withstands
extremes of cold, hot and vibration.

 
  Nylon has been around in quantity since the 40s.  Somehow I doubt
  it's qualities were 'unknown' in the 50s and beyond :-)

What's more likely is its qualities were well known, and known to be
unsuitable for use in aircraft wiring harnesses.

  MORE likely some senator was vested in a biz that made the older
  materials.

In your specific example of aviation wire looms, likely not -- see
below.

  There ARE circumstances where 'natural fibers' CAN outperform
  plastics - esp at very low temperatures where the plastics become
  more brittle.

And just what do you have at altitude?  Very low temperatures, just
exactly what you state "where the plastics become more brittle":

https://matmake.com/properties/standard-atmosphere.html

10k-20k feet -> -60C
25k feet (typical passenger aircraft cruse altutude) -> -50C

  However those circumstances are few.  'Natural fibers' also tend to
  hold MOISTURE - which is bad for HV electricity apps and can lead
  to mold/fungi problems.

Yes, that can be a problem, but having your wire loom become brittle at
-60C as you climb through 10k to 20k in altitude and crack apart is not
going to be very good for your aircraft maintaining its intended flight
path.

Also because (esp.  for EPROMS) the rope memory was much more
radiation hardened than EPROMS of the day were.  Also, for 'long
duration' projects such as that, often each component is designed
and built, then in the end the various parts are pieced together to
produce the "flying candle" you see on launch.  But the "computer"
might have been designed and built five years before that launch,
and minus five years from today might have meant no PROM or EPROMS
were even available at the time.

 
  I'd argue about UV-erasable PROMS and space radiation ...
  the damned things weren't THAT damned sensitive.

Clearly you are unaware of the kind, and amount, of radiation impact
devices sustain once they are outside the shielded environment here on
the surface.  If UV light is energetic enough to erase them in 15
minutes (which was about what it took during their heyday) then there
is way more energetic radiation in space that will wipe your uv-eprom
for you.  Keep in mind, these satelites are usually designed for a
multi-year service life (often decades).  That means your UV Eprom must
not lose its programming after being bomarded by significant amounts
of radiation for 10 or 20 years -- not just a 15 minute soak.  Absent
an actual "radiation hardened" version the standard ones you'd have
been using during the day would not have lasted more than a week or two
before their stored program would have been erased.

  There were also 'fuse PROMS' back then - literal made or broken
  wire connections.  You CAN still buy them, checked recently.  So
  long as they're socketed the firmware can be replaced pretty quick
  and easy.  Low cap by today's standards, but in 1968 or so ...

Those might have been suitable, at least it is unlikely the space
radiation would have blown an unblown fuse (or reconnected a blown
one).  Of course all the read out transistors also have to not be
impacted by the radiation sufficient to produce bit flips, over the
service life of the satelite, for them to be suitable for use.