If a single rating is selected on the DC TRS page 1, this
rating will be used as the rating by the perf computer.
The
choices are:
. Takeoff
● Flex
. Go-around
● Climb
● Cruise
● Max Continuous
A DAU channel switch takes place if one or more
following parameters are invalid, as determined
of the
by the validity
or the applicable range and rate tests: Nl, N2, EPR, fuelflow,
and fuel quantity.
The switch only takes place if the
nonselected channel has all valid data. N2 is included in this
list to
allow perf and autothrottle to use a common selection
logic.
The DAU
N1 reasonable test consists of range and rate checks.
For the range test, the minimum rpm is O and the maximum rpm
will be 110
percent.
The rate test will be failed if a rate in
excess of 5 percent
per sample is detected. IfNl is
considered invalid for a given channel of a DAU for 400
milliseconds, then the data from the other channel will be
used.
The DAU EPR reasonable test consists of range and rate checks.
For the range test, the minimum EPR is 0.8 and the maximum EPR
will be 2.0. The rate test will be failed if a rate in excess
of 0.06 EPR per sample is detected. If EPR is considered
invalid for
a given channel of a DAU for 400 milliseconds, then
the data from the other channel will
be used.
Fuel quantity has no validity so a simple range and rate test
is performed. For the range check the minimum quantity is O lb
and the maximum is 16,500 lb for each DAU. We would expect the
performance computer to continue to operate properly with these
values since they are valid inputs to the tables. The flight
manual lists a maximum value of 14,750 lb. The total fuel
quantity is the sum of the two separate values from the two
DAUS.
The rate check fails if the change is greater than 875
lb per
sample. The validity should be set valid only if both
DAUS have valid data.
Fuel flow has no validity so a simple range and rate test is
performed. The fuel flow must be between O and 10,485 lb/hr
(per the ASCB specification). The max value in the FUELFLOW
table is 10,355 lb/hr, and the performance calculations will
operate without error up to this value.
Total fuel flow is the
sum of the two separate values from the two DAUS. The rate
test fails when the change is greater than 320 lb/hour per
sample.
The validity should be set valid only if both DAUS
have valid data.
22-14-00
Page 298.173
Aug 15/91
Use or disclosure of information on this page k subject to the restrictions on the Mle page of this document.
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