H28466
LOC Switching Logic Diagram 500
22-11-0 Figure 12 Aug 15/68
Page 46
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
heading/beam integrator during the localizer on-course submode.
3) Cross-beam rate signals are applied to rate sensor past de-energized switch RS-22, summing point 11, and an amplifier. The rate sensor serves the same function as for the VOR on-course submode except the sensor trips when the cross-beam rate drops to 2 millivolts per second rather than tripping for a heading course error of less than 15 degrees, which is the case during the VOR mode. (See figure 12.)
4) The bank angle command limit for this submode is the same as that for the VOR on-course submode (+ 8 degrees), but the roll rate command limit is increased to 7 degrees per second.
(e) The localizer approach on-course submode is initiated during the on-course submode after the glide slope is engaged by the pitch axis and the airplane altitude (sensed by the radio altimeter) is less than 1500 feet. This submode differs from the on-course submode as follows: 1) Gain programmer decreases the amplitude of the radio beam deviation signal as a function of altitude (gain programming), starting with the initiation of the approach on-course submode. The program control signals are supplied by the pitch channel in which radio deviation gains are also programmed to compensate for beam convergence as the transmitter is approached.
2) Heading course error signals are removed from summing point 12 and therefore from summing point 2 by energized switch RS-19 of figure 6. Heading information for this submode is provided by the heading computer which reverts to the heading hold (clamped) configuration. Heading error signal gain is decreased during this submode by energized switch RS-7. Heading error signals are applied to summing point 2, both directly and through summing point 3 and the lagged roll integrator. Summing heading error signals with the inverted integral of signal from the lagged roll integrator produces washed-out heading error signals to provide mode damping without contributing to beam standoff in the presence of wind shear. Roll attitude signals from the vertical gyro are also fed to the lagged roll integrator to produce the lagged roll signals which provide additional damping and improve the wind shear performance during the approach on-course submode.
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May 15/68 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-11-0 Page 47
3) The bank angle command and roll rate command limits remain the same for this submode as for localizer on-course.
(8)
Turbulence Penetration Mode
(a) Although the turbulence penetration mode is primarily an autopilot pitch axis mode, it also affects the roll axis. Whenever the pitch channel is placed in turbulence penetration, the roll axis bank angle command limit is 8 degrees and the localizer mode is made inoperative.
(9)
Warning Lights
(a) The disengage warning light circuit operates in the following manner. When electrical power is applied to the airplane, power is applied to the disengage lights, flasher and warning light module. (See figure 13.). If the warning lights illuminate steadily, one or more of the pitch, roll, or yaw self-test switches is in a test position other than OFF. Proper operation of the autopilot is dependent upon all self-test switches being in the OFF position. Upon autopilot channel engagement, 28 volts dc engage interlock voltage is applied through a nuisance suppressor time delay (0.1 second) to a capacitor in the base circuit of a gating transistor. When interlock voltage is interrupted the gating capacitor is grounded and a momentary negative pulse developed across the capacitor triggers the transistor which fires the SCR. The SCR conducts and provides a ground for the flasher, thereby causing the warning lights to illuminate and flash. Positive voltage on the transistor base keeps the transistor turned off. However, the SCR continues to conduct and the warning lights continue to flash. The SCR ceases to conduct and the lights are extinguished when the light circuits are reset by depressing either warning light cap or by depressing either disengage switch. Once the lights are reset, they are rearmed to monitor the remaining interlock. If the autopilot is disengaged through operation of either disengage switch, the warning lights will illuminate momentarily while the switch is depressed and then go out.
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