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The 'MEASURE' to 'CONTROL' transition
When either of the Pt, Ps1 or Ps2 outputs are changed from Measure or Leak to Control mode,
a sequence of events takes place that needs explaining. Since the controlling portion of the
6600 is isolated from the output during Measure or Leak modes, it will usually be at a
pressure quite different from that at the output. Simply introducing the controlling section
into the pneumatic system connected to the output will cause a surge in pressure (or vacuum)
at the output. To prevent such a surge, the 6600 measures the pressure at the output, shuts-off
the output from the internal 6600 pneumatics, and then controls the pressure within the
internal control mechanism to match the pressure at the output. Once this is done, the 6600
controlling section is connected to the output. This process is termed as Equalization.
While the 6600 is undergoing this process, the term 'EQZN' is displayed on the main screen in
place of the "Actual" value. The whole process usually takes about 15 seconds or less to
complete. During the 'EQZN' process, the Main Operating screen will appear as shown
below.
2-output format
Units:
Actual:
Target:
Units:
Actual:
Target:
Once the Equalization process is complete, the Actual values appear on the Main Screen.
Following the Equalization process, only when the actual value on the Ps1 and Ps2 outputs
are less than 2000 feet from Ground and the Pt output is less than 100 knots, the 6600 will
automatically inject a small vacuum on the Ps1 and Ps2 outputs and a small pressure on the Pt
output. This is done to determine the volume of the Pitot and Static system on the aircraft, so
that the 6600 can automatically adjust the gain of it's control mechanism. Due to this, the
actual value will always increase in both altitude and in knots for about 5 seconds, regardless
of the target value. Once this process is complete, the actual values will move towards the
target values.
This process is part of the "Measure" (or "Leak") to "Control" transition, and will take place
only when the transition to "Control" takes place within 2000 feet of Ground and 100 knots.
knots
C
EQZN
20.0
knots
C
EQZN
20.0
Feet/min
EQZN
EQZN
3000
3-output format
Feet
EQZN C
0
37
Feet
C
0
Feet
EQZN
C
0
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