H23873
Air Data Pressure Instrument System Component Location  505 
34-12-0  Figure 1  Nov 15/67 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

2.  Airspeed/Mach Indicators
A.  Pneumatic Instruments
(1)  
The airspeed/mach indicator is a combination of two flight instruments which presents an integrated display of indicated a airspeed and mach number (Fig. 2).

(2)  
Indicated airspeed is displayed through the range of 60 to 420 knots. The indicator dial scale is calibrated linearly in 2-knot increments between 60 and 160 knots, and logarithmically in 10-knot increments between 160 and 420 knots. A pointer, rotated by a mechanically connected pressure diaphragm, indicates the airspeed range through a single revolution. Two reference pointers (bugs) are provided on the bezel for pilot convenience in presetting airspeed reminders, such as V1 and V2.

(3)  
The mach mechanism is actuated by an evacuated capsule whose linkage is such that it rotates a subdial at an angular rate which varies linearly with the logarithm of the static pressure. This subdial is graduated in increments of 0.02 mach and reads from 0.5 to 1.0 mach.

(4)  
The airspeed dial and mach subdial scale factors are selected so that the single pointer shows airspeed on the outer perimeter of the dial and mach number on the subdial scale through a cutout in the main dial adjacent to the high airspeed markings.

(5)  
A manually operated airspeed command knob rotates the airspeed command index around the outer periphery of the main dial. When the auto throttle system is installed, the airspeed command knob is used to set the airspeed to be maintained (Ref 22-31-0). The VMO pointer locates and accents the maximum operating airspeed of the airplane as a function of altitude.

B.  Servoed Instruments
(1)  
The airspeed/mach indicator is a combination of two flight instruments presenting an integrated display of computed airspeed and mach number (Fig. 2). The central air data system is designed to utilize a combined instrument in which the altitude assembly, the airspeed assembly and the mach number assembly are operated from air data computer processed information.

(2)  
Computed airspeed derived from the air data computer, which is corrected for static pressure source error, drives the airspeed pointer from 60- thru 450-knot range of airspeed. The mechanism produces linear rotation of the pointer in two knot calibration increments between 60 and 160 knots, and logarithmically in 10-knot increments between 160 and 450 knots. An airspeed valid signal from the air data computer is also provided to the A/S flag.

(3)  
Mach number indication is presented on a two drum digital readout through the range .40 to .99 mach. Below .40 mach the readout is covered by a mach flag. The mach readout mechanism is driven by corrected electronic mach number signals processed by the air data computer. Upon power failure, or loss of 28 volts dc from the air data computer, a striped red and white OFF flag will appear to cover the digital mach readout.

(4)  
The colored pointer on the indicator shows maximum operating speed of the airplane as a function of corrected altitude mach and airspeed from the air data computer. The "INOP" flag indicates the absence of an operational performance data computer system. Pulling the bug set knob out will retract flag. White peripheral pointers may be set manually to any desired airspeeds. When operating in the manual mode, an "M" flag will appear in view at the top of the indicator.

(5)  
The airspeed/mach indicator operates from a 26 volt ac power supply controlled by a circuit breaker on electronic panel P18-2. 

517 
Feb 15/79  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-12-0 Page 2A/2B 

K85824
5C8  Airspeed/Mach Indicators 
Jan 20/83  Figure 2  34-12-0 
Page 3 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

3.  Instantaneous Vertical Speed/Rate of Climb Indicators
A.  Instantaneous vertical speed/rate of climb indicators are provided for both the captain and first officer and are operated by static pressure applied to both the inside of the instrument case through an orifice and to the interior of a flexible diaphragm within the case. As the airplane changes altitude the pressure inside the diaphragm changes more rapidly than that inside the instrument case. The resulting differential causes the diaphragm to expand or contract, and the amount of change is proportional to the rate of change of altitude and is indicated by a radial pointer in thousands of feet per minute. An accelerometer is incorporated in the instrument also, and provides indication of instantaneous vertical speed (Fig. 3).
　
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