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7) On LH 011-030, 051-070, 082-099; AF 121, 122, 152-199; AT ALL: IB 406-499; GN ALL; MD ALL; VM ALL, the central air data system connects to the autopilot/flight director vertical speed select mode by supplying a two-wire ac generator output representing pressure altitude rate of change from each central air data computer to the mode select panel of the autopilot/flight director (Fig. 6). To use air data computer outputs in the vertical speed mode, the mode select panel has either A or B autopilot engage or flight director ON switches on, the turb/speed mode select switch in the V/S position and the desired vertical speed set on the vertical speed thumb wheel. Once the air data computer that will provide the altitude rate signal has been selected, the input is routed to the vertical speed processor module where altitude rate is compared with desired altitude rate and a difference or error signal generated. The altitude rate error signal is then routed to all three pitch computers in parallel. Thus for vertical speed select or read-out mode, either central air data computer can provide an altitude rate of change error signal to all three pitch computers.
8) The central air data system supports the autopilot/flight director indicated airspeed hold and altitude hold modes by supplying two-wire, ac analog voltages representing indicated airspeed error and altitude error from clutched synchro outputs in the central air data computer to the autopilot/flight director pitch computers (Fig. 7). a) A hold synchro only provides an output when its clutch
is energized, connecting it mechanically with the servo loop of its particular computing module. Any future variation in the parameter being measured by the computing module produces a hold synchro output due to shaft rotation. The hold synchro output is a measure of error or deviation from the value of the parameter at the time the hold synchro clutch was energized.
b) Clutch energized signals are initiated from the autopilot/flight director mode select panel. Hold synchro clutches for the functions of computed airspeed and mach number are energized by setting the turb/speed mode select switch to the IAS or MACH position. Hold synchro clutches for the function of pressure altitude are energized by setting the altitude mode switch to the ALT HOLD position.
(5) System Test Modes
(a) Air Data Computer (P/N's 60B00058 and 60B40126)
EFFECTIVITY
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1) Each central air data computer has a self-test mode initiated by a press-to-test, SELF-TEST button on its front panel. When the SELF-TEST button is depressed, internal error signals slew the servos in all four computing modules to a predetermined simulated flight measurement position, all failure warning outputs are activated, three chassis warning lamps illuminate and the accuracy of each servo loop null is verified (by chassis warning lamps extinguishing within 120 seconds). This test mode remains active until the SELF-TEST button is released. The CAS light will illuminate momentarily when the SELF-TEST button is released. Thus the self-test mode: a) Activates the failure warning logic assembly and all
failure warning flag outputs. b) Checks four of the five chassis warning lamps. c) Checks all computing module servos for slew capability. d) Checks all computing module servo loops for null or
positioning capability. e) Supplies interfaced subsystems with simulated flight outputs and warning flag outputs.
2) Preselected simulations of altitude rate, altitude hold and computed airspeed hold are initiated from the central air data computer front panel. Functional tests of true airspeed servo, mach servo, computed-airspeed servo, pressure altitude digitizer and the altitude reporting lamps are also initiated from the central air data computer front panel. These nine test modes are selected by a rotary switch and initiated by either a PRESS-TO-TEST button or by holding pushbutton B and then A in that order until test is completed. Each of these modes provides an additional means of aircraft interfacing system checkout. The sequence of tests may be random and each mode remains active until the button is released. The self- test circuits introduce simulations without breaking primary signal paths.
(b) Air Data Computer (P/N HG480C1)
1) Each central air data computer has a self-test mode initiated by a PRESS TO TEST button on its front panel. The self-test mode remains active until the PRESS TO TEST button is released.
EFFECTIVITY
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2) Preselected simulations of altitude rate, altitude hold, computed airspeed hold, and mach hold are initiated from the central air data computer front panel. Functional tests of true airspeed servo, mach servo, computed airspeed servo, and pressure altitude digitizer and are also initiated from the central air data computer front panel. The three test modes are selected by a rotary switch and initiated by a PRESS-TO-TEST button. Each of these modes provides an additional means of aircraft interfacing system checkout. The sequence of tests may be random and each mode remains active until the button is released. The self-test circuits introduce simulations without breaking primary signal paths.
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