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Manual Venting of the Aircraft Pitot and Static
Systems
ADTS status on power failure
On removal of power, the main output valve linking external ports Pt and Ps to the internal pressure
controllers will automatically close. The aircraft pitot and static systems remain safe but with the last
applied pressures now isolated and maintained in the hoses.
ADTS status on restoration of power
When power is restored to the ADTS the normal self test routine for the ADTS will be performed and
at the end of this the ADTS will exactly equalize the internal manifold pressures to match those of the
external aircraft hoses and then the output valves will be reopened. This process will at all times
protect the aircraft pitot and static systems from adverse pressure transients, differentials or exces-
sive rates.
When the output valves are fully opened, the normal parameter measurement screens become avail-
able from the Dashboard and full control is again available. The testing may then either continue from
the same point (when the power failure occurred) or the aircraft pitot and static systems may be
safely controlled back to ground pressures.
Actions if power cannot be quickly restored
Two courses of action are possible at this point:
1)
Leave the ADTS connected to the aircraft pitot and static systems with pipes safely isolated but
maintaining trapped pressures until such time as power can be restored.
2)
Use the manual let-down valves on the ADTS front panel to safely bleed the trapped hose pres-
sures back to ambient ground. This must be carried out in a way that ensures the Pt to Ps differ-
ential pressure remains at zero while the whole connected system is brought to ground
pressure.
Open the valves slowly while monitoring the cockpit gauges for any excessive rate of change.
The order the manual let-down valves are opened is:
M
V
A
ANUAL
ENTING OF THE
IRCRAFT
P
S
S
ITOT AND
TATIC
YSTEMS
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