(c)  
The Altitude Hold mode (not at the selected altitude) is entered as the normal termination of the Altitude Hold Capture mode or by selecting a new altitude when in Altitude Hold mode (at the selected altitude). This mode can be disengaged by selecting any other pitch mode. Altitude Hold mode (not at the selected altitude) engaged is indicated by ALT HOLD, black or green, annunciated on the FMA and the ALT HOLD pushbutton on the MCP illuminated.

(5)  
Vertical Speed (V/S) Mode

(a)  
The vertical speed mode provides pitch commands to fly the selected rate of climb or descent. This mode has both an armed and an engaged state.

(b)  
With the autopilot engaged in command, the mode is engaged by pressing the vertical speed pushbutton. When selected, the vertical speed display window unblanks and displays the existing vertical speed. The thumbwheel near the display can now be used to increase or decrease the selected vertical speed. The selected vertical speed is acquired.

(c)  
The vertical speed mode becomes armed only if currently in altitude hold mode (at the selected altitude) and a new altitude is selected which is more than 100 feet away from previously selected altitude. The altitude hold mode holds the old altitude and the FMA annunciation shows altitude hold and V/S arm. The armed mode allows engagement of V/S by moving the vertical speed thumbwheel without having to press the vertical speed pushbutton.

(d)  
Vertical speed also automatically engages if the airplane is in the altitude acquire mode and a new altitude is selected which is more than 100 feet away from previous selection. At this time, the vertical speed mode engages and the existing altitude rate appears in the vertical speed display window. The thumbwheel may now be moved to change the climb or descent rate. When the new altitude acquire 0.05g circular path is intercepted, altitude acquire will re-engage, disengaging V/S. V/S is annunciated on FMA white on black when the mode is armed and black on green when the mode is engaged.

(6)  
Level Change (LVL CHG) Mode

(a)  
The Level Change mode provides pitch commands to fly the selected speed or Mach (except if any envelope placard is exceeded). The level change mode always commands the airplane toward the selected altitude on the mode control panel. The level change mode can be selected by pressing the LVL CHG pushbutton on the MCP. Level change is automatically engaged to provide elevator control when a performance limit, alpha floor (minimum) speed, Vmo and Mmo (maximum) speed is detected.

(b)  
If a speed mode was not engaged prior to engaging the level change mode, the speed select window will display the existing speed at the time of engagement. If a speed mode was engaged prior to engaging the Level Change mode, the selected or target speed used by the preceding speed mode will be retained as the selected speed.

(c)  
If Vmo or Mmo is detected, Level Change will limit the speed to Vmo or Mmo. However, if a lower altitude is selected and the level change mode can not control to Vmo or Mmo and satisfy a minimum descent rate, the autopilot will disconnect and the Flight Director Bars will bias out-of-view. Likewise, if Alpha Floor (minimum rate speed) is detected, Level Change will command a minimum speed. If a higher altitude is selected, and Level Change can not control to a minimum speed and satisfy a minimum climb rate, the autopilot will disconnect and bias the Flight Director bars out-of-view.

(d)  
Speed, black or green, is annunciated on the A/P-F/D portion of the FMA, when level change mode is engaged.

(7) 
 PDC Speed

(a)  
The PDC Speed mode provides pitch commands to maintain the target airspeed (except if any envelope placard is exceeded) from the PDC. This mode can only be engaged to fly speed-on-elevator by pressing the PDC pushbutton on the MCP. In this mode the speed select window blanks but the PDC target speed is presented on the MASI speed bug and on the engaged page of the PDC control display unit. PDC SPD, black on green, is annunciated on the A/P-F/D portion of the FMA, when the mode is engaged.

(b)  
The displayed speed on the MCP window, when displayed, should agree with the airspeed bug on the mach-airspeed indicator within +2 knots.

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May 20/82  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  22-11-01 Page 43 

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I.  AP/FD Cruise Mode Capabilities
(1)  
When the autopilot or flight director is commanded to a speed mode, the auto throttle will be commanded to an EPR mode. If the autopilot or flight director is commanded to a mode other than a speed mode, the auto throttle will be commanded to a speed mode. The PDC will always be autoengaged to a mode consistent with the EPR limits being observed by the A/T.
　
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