56-101-01175 Revision H Page | 51
menu (Example: with Limits = default, ALR for ROC = 1,000 ft/min and RtCAS = 25
kts/min) the Test Set will automatically switch into Control mode with the Target values
set to the current ALT and CAS values and the Test Set pneumatic controller will try to
overcome the leak and stabilize the pressures on the STATIC (Ps) and PITOT (Pt) ports.
When this occurs, the following message will be displayed: “Excessive Leak Detected”.
The Leak Test ATP profiles are only available when the Display Setup is configured for
Aeronautical display mode. When the user selects Pressure or EPR “Engine Pressure
Ratio” display mode, the Leak Test ATP is not available, only the Leak Rate Timer
feature is available under these two display modes.
D. Control mode
The Control mode provides a two-channel pneumatic controller. The DPS1000 controller
is referred to as the PCM (Pneumatic Control Module.) This module provides an
absolute pressure controller for the STATIC (Ps) channel and a differential pressure
controller for the PITOT (Pt) channel.
The two-channel precision controller is used to control and simulate the Target pressure
and vacuum set point conditions and rates as requested by the user setting Target set
points.
The pneumatic controller is capable of controlling the STATIC (Ps) channel pressure
with a resolution of ~ 0.0002 inHg while maintaining the PITOT (Pt) channel differential
pressure with a resolution of ~0.0004 inHg. The precision custom controller provides the
ability to maintain a constant CAS “Airspeed”, even during high rates of ROC enabling 0
kts CAS (the most demanding control situation) to be well maintained under
considerably high slew rates of 6,000 ft/min or higher.
When the DPS1000 transitions into Control mode, the display indicates “Wait
Resuming Control.” During this transition period (~ 4 seconds) the PCM is responsible
for establishing the same controlled pressures as last measured on the STATIC (Ps) and
PITOT (Pt) ports while in Leak Measure mode. During the Leak Measure mode to
Control mode transition, the Target set points are always preloaded with the same value
as the existing pressure measured on the ports at the time the Control mode was
selected.
The following internal control sequences occur:
1. The pressures presently on the STATIC (Ps) and PITOT (Pt) ports are measured
and recorded.
2. The output valves located internally on the DPS1000 pneumatic control manifold
(SvPs_Out and SvPt_Out, reference DPS1000 Internal Pneumatic diagram,
Appendix C) are closed to isolate the pneumatic controller from the aircraft or
instrument under test. This is done to ensure that no transient pressure spikes are
seen or impressed onto the UUT or aircraft while the internal control manifold is
establishing the same control pressures that were last measured on the STATIC (Ps)
and PITOT (Pt) ports. During this process the Test Set displays “Wait Resuming
Control”. Once the PCM has established stable internal control vessel pressures the
output valves (SvPs_Out and SvPt_Out) are opened.
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