
CM170407AMA
SECTION 9 SAFETY MANUAL OPERATION
9.1 MANUAL VENT
In the event of power loss and failure of the battery, the Ps, Pt and AoA lines can be
returned to ambient pressure by means of manual valves.
The three needle valves (FIG 1 items 15.), located on the front panel, are used for the
manual venting.
Turn counter- clockwise to open the needle valves.
The needle valves must be rotated together, very slowly, to avoid excessive rate values.
Too fast rotation of Pitot Vent needle valve can change too quickly the pitot pressure and
too fast a rotation of Cross Bleed (“Equalize”) needle valves can increase the Altitude Rate
to excessive values.
The suggested procedure is the following:
1. Slowly open the Ps-Pt and Ps-Ps2 cross-bleed valves simultaneously. If the altitude
tends to go outside the safe working limits, then slightly open the Pt vent valve.
2. When both cross-bleed valves are open, slowly open the Pt vent valve until all lines
return to ambient pressure.
CAUTION
When the manual venting is completed, all manual venting needle valves
must be turned fully clockwise to be closed, to restore the seal on pneumatic
circuit.
Do not over-tighten.
FIG 15 SCHEMATIC OF THE MANUAL VENTING VALVES
D.Marchiori Copyright
36
Ps
Pt
Ps2
Equalize Static – AoA
Ambient
Equalize Static – Pitot
Vent Pitot port