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Effect of Rate target value :
The Rate target value affects the rate of change of Ps1, Ps2 and also sometimes, Pt. The Rate
target value can be entered in four different units, depending on the selected units for Ps1.
The four Ps1 units are : feet, meters, inHg and mbar. Feet and meters are considered as
"altitude" units. InHg and mbar are considered as "engineering" units. The 6600 maintains
two distinct Rate target values for "altitude" units and "engineering" units.
When a Rate target value is entered as 6000 feet/min it is automatically converted to 1828.8
meters/min. But it is not converted to inHg/min or mbar/min. Conversely, when a Rate
target value is entered as 4.000 inHg/min it is automatically converted to 135.46 mbar/min.
But it is not converted to feet/min or meters/min. The 6600 distinctly maintains two Rate
target values of 6000 feet/min for "altitude" units and 4.000 inHg/min for "engineering"
units.
If Ps1 is in Control mode and the units for Ps1 are "altitude" units then the 6600 will ramp
towards the Ps1 target using the Rate target value in "altitude" units, i.e. 6000 feet/min. If Ps1
is in "engineering" units then the 6600 will ramp towards the Ps1 target using the Rate target
value in "engineering" units, i.e. 4.000 inHg/min.
The Pt output has four "airspeed" units - knots, Mach, mph, kmph. When the Pt output is in
one of these four "airspeed" units, the Rate of change of the Pt output is controlled by the
"Knots Rate" which is setup using Function 3. (section 3.5.3). While in "airspeed" units, the Pt
output is not affected either by the "altitude" rate or by the "engineering" rate.
The Pt output also has five "engineering" units - Pt inHg, Qc inHg (differential), Pt mb, Qc
mb (differential), and EPR (Pt divided by Ps1). While the Pt output is in any one of these
"engineering" units, its Rate of change is the "engineering" rate entered in the Rate target
value. If the "engineering" rate was entered as 4.000 inHg/min then the Pt output will ramp
towards its target value at 4.000 inHg/min.
The Ps2 output has four "engineering" units - inHg, mbar, Differential inHg (Dfin), and
Differential mbar (Dfmb). The Ps2 output has two "altitude" units - feet and meters. The Ps2
output also has two "airspeed" units – knots and kmph.
When the Ps output is in
"engineering" units it will use the "engineering" rate (i.e. 4.000 inHg/min) to ramp towards
the target. When the Ps2 output is in "altitude" units it will use the "altitude" rate (i.e. 6000
ft/min). When the Ps2 output is in "airspeed" units it will use the "Knots Rate" (section 3.5.3)
to ramp towards the target.
Because of the distinct use of the "engineering" rate and the "altitude" rate, it is
recommended that the Rate target values be set in both "engineering" and "altitude" units.
The default values set at the factory are 4.000 inHg/min for the "engineering" rate and 3000
feet/min for the "altitude" rate. The default value for the "Knots Rate" is 500 knots/min.
To summarize the effects of the Rate target value on Ps1, Ps2 and Pt, let us assume that the
factory defaults, shown above, are in effect. Then the following table shows which Rate value
will be effective depending on the units selected for each output.
28
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