On Thu, 9 Oct 2003 14:11:35 -0700, Eric Greenwell
wrote:

In article ,
says...
I want to know how to change the zero offset value (screen #10 ASI
reading), which is wrong. Can it be done without opening the 302 -
opening it will break the security seal and prevent it being used for
badge claims !!!

I was told a while ago that the ASI zero offset is determined
automatically by the instrument whenever it is turned on, and does not
require any adjustment by the pilot.


Hopefully there is a solenoid valve then that brings the pitot and
static to the same pressure during the power up cycle(you should hear
a click as it cycles). Otherwise there will be some interesting
effects in any reasonable wind, particularly in crosswinds.
Another method uses a pressure switch that switches mechanically at
some given airspeed thus telling the instrument what the sensor offset
is. Hopefully the pressure switch has a stable trip point.

The original CNAV had a solenoid valve in the airspeed measurement
system as did our B20 system back in the 1980's.
I think Peschges used the pressure switch in the VP2 at least.

Mike Borgelt