(2)
The VOR/LOC and AUTO APP positions of the mode select switch are the radio modes. The VOR/LOC position requires only the roll channel to be engaged; however, the pitch channel can also be engaged. The AUTO APP position requires both pitch and roll channels to be engaged. Selection of VOR/LOC allows the airplane to capture a VOR radial or localizer beam. Course error and radio deviation then cause the autopilot to fly the airplane onto the selected course indicated on the course deviation indicator.
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Control wheel steering can be used to aid putting the airplane on-course. The roll control wheel steering goes to high detent when the airplane is on-course. Use of roll control wheel steering with the airplane on-course trips the mode select switch back to the MAN position. Operation of the autopilot is similar for the AUTO APP position except if either the pitch or roll control wheels are moved out of high detent when roll on-course or glide slope capture, the switch trips back to MAN. If a localizer frequency is selected, selection of TURB trips the mode select switch back to MAN.
(3) Selecting HDG OFF locks out the automatic wings leveling feature of the roll channel when the bank angle is less than 5 degrees, thereby allowing the airplane to be maneuvered with control wheel steering and allowing the airplane to fly at any attitude. The pitch channel does not have to be engaged for HDG OFF; however, it can be engaged.
C. Heading-Nav Mode Select Switch
(1)
The heading-nav mode select switch is normally centered. When centered, the autopilot controls the airplane in either attitude hold or heading hold (if MAN is selected). The heading-nav switch is always centered if the autopilot has captured a VOR radial, localizer beam or glide slope beam.
(2)
The HDG SEL position can be selected provided the roll channel is engaged and the LBS or VBS has not dropped out (capture), regardless of the position of the mode select switch. The autopilot flies the airplane to whatever heading is selected on the course deviation indicator. Control wheel steering cannot be used in HDG SEL without tripping the HDG SEL switch back to center.
(3)
The NAV position can be selected provided the roll channel is engaged and the selected OMEGA system is providing a nav valid output. The autopilot flies the airplane to the desired track which is computed by the OMEGA system and provided to the autopilot as a steering signal. Control wheel steering cannot be used in NAV mode without tripping the NAV switch back to center. The pitch channel does not have to be engaged for either HDG SEL or NAV; however, it can be engaged.
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D. Pitch Mode Select Switch
(1)
The normal position of the pitch mode select switch is OFF. The pitch channel maintains the airplane attitude at time of engagement. Pitch control wheel steering can then be used to maneuver the airplane. With the control wheel back in detent, the pitch channel keeps the airplane at the new established attitude.
(2)
Positioning the pitch mode select switch to ALT HOLD requires the pitch channel to be engaged and a valid altitude good logic from the air data computer. The pitch channel keeps the airplane flying at the established altitude at the time of selecting ALT HOLD. The mode select switch can be in any position. The pitch mode select switch remains in ALT HOLD provided the glide slope has not been captured. Pitch control wheel steering can not be used when in ALT HOLD without tripping the switch back to OFF. The roll channel does not have to be engaged to select ALT HOLD.
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