(1)  
The inputs into the PDCS are as follows:

(a)  
Air data computer - fine and coarse altitude and airspeed

(b)  
DME interrogators - distance information

(c)  
Fuel summation unit - total fuel quantity

(d)  
EPR indicator - EPR information

(e)  
Air conditioning switches -bleed air logic

(f)  
Anti-icing switches - bleed air logic

(g)  
TAT probe - total air temperature

(h)  
Omega Navigation System - distance and ground speed

(2)  
The computer outputs include:

(a)  
EPR indicators - target EPR command bug signal

(b)  
Mode annunciators - digital mode logic

(3)  
On GJ 2509 and 2510;

(a)  
Flight control computers - autothrottle engage logic, ARINC 429 digital data bus 1) Mach/Airspeed indicators -target command bug airspeeds

(b)  
Autothrottle computer - autothrottle engage logic, BITE test logic, ARINC 429 digital data bus

C.  The computer and CDU receive 115v 400 Hz ac power from the ELEX POWER bus No. 1 through the PRFM DATA COMPUTER circuit breaker on the P18 panel. The mode annunciators receive 28VDC power from the ELEX POWER bus through the PDCS MODE ANN circuit breaker on the P18 panel.
5C8 
Jun 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  34-18-0 Page 1 

K79321
Performance Data Computer System - Component Location  5C8 
34-18-0  Figure 1  Jun 20/88 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

2.  Control/Display Unit (CDU) (Fig. 1)
A.  The control/display unit (CDU) contains the controls and cathode ray tube display necessary to operate and monitor the PDC system. Internal to the CDU is a power supply, logic circuits to encode and decode information exchanged with the computer and cathode ray tube display circuits.
B.  The CRT displays all input/output flight mode and performance function data. The data is displayed in 6 rows in alphanumeric format. Most flight modes and performance functions have more than one display available. The multiple displays (pages) contain different operating conditions or information. The top of each page has page title, page number and number of pages available for the mode or function displayed. A question mark in the display indicates missing data that must be entered into the computer. A caret ( ) or asterisk (*) at the end of a line indicates information that may be entered manually.
C.  The flight mode selector and TURB key on the CDU determine flight mode displayed. The flight modes available are standby (STBY), take-off (TO), climb (CLB), cruise (CRZ), descent (DES), holding (HOLD), continuous (CON), go-around (GA) and turbulence (TURB). All modes are selected on the flight mode selector except TURB (turbulence), which is selected by pressing the TURB switch. TURB can only be selected in the CRZ mode.
D.  For flight modes, the ENGAGE key engages the EPR and Mach/Airspeed command bugs unless otherwise commanded by the AFCS. If data is verified by the computer to be valid, engageable, and different from data presently engaged, the ENGAGED switch illuminates. After engagement, the ENGAGED switch extinguishes, the appropriate mode annunciator light illuminates, and the command bugs are driven to the displayed values. After flight mode is engaged, another flight mode or performance function may be displayed on the CDU. The command bugs continue to be driven by the engaged flight mode. The ENGAGE switch illuminates to indicate the displayed data is not driving the command bugs.
E.  The keyboard switches consist of three display management keys and eleven performance function and data entry keys.
(1)  
The three display management keys are:

(a)  
RCL -If a performance function is being displayed and RCL is pressed, the display reverts to the mode selected on the flight mode selector. If the mode on the mode selector is engaged, the page engaged will be displayed. If the mode on the mode selector is not engaged, page one will be displayed.

(b)  PAGE -The page keys advance (→
) or reverse (←
) the page being displayed.

(2)  
The performance function/data display keys are used for performance function selection and data entry.

(a)  The minus key (.
) is used for entering negative data values and calling up test pages.

(b)  The flight performance functions include: flight level intercept (↑
x↓
), reference speed (VREF), ground speed (GS), range (RNG), FUEL, temperature (TEMP), flight level (FL), TRIP, and WIND.
　
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