"William W. Plummer" wrote in message
news:3xhLc.132243$IQ4.127452@attbi_s02...
Ron Natalie wrote:
"Thomas Borchert" wrote in message
...

Ron,


Each aircraft registration has a mode S. It's
constant whether the N number changes


What's the difference between N number and aircraft registration in
the above quote?


You can change the N number. The Mode S is tied to the aircraft itself
(the
model and serial #).

So the Mode S number bound to the airframe. Is that the Airworthiness
Certificate? It's all sort of strange because you can replace your
transponder, a wing, radios, fuel tanks, the engine... just what is the
"aircraft"? One view is that it is the file card-size plate that
identifies the aircraft. But I thought that has the N-number on it.

Let me guess: the aircraft is the same as the N-number and that cannot
be changed. The Mode-S number is simply a reflection of the N-number.
Removing the transponder from a plane probably requires the technician
to zero the Mode-S number in the transponder. Installing a transponder
requires the tech to lookup the Mode-S number based on the N-number

Actually, one of the connectors on the rack into which the
transponder is installed has a set of contacts that are encoded
with the code for that aircraft. *Any* transponder plugged into
that position has the info for that specific airframe. Same kind
of technique is used for CVR, FDR and several other boxes.