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In SPEED AUTO CONTROL (except in EXP mode), a magenta SPEED CHANGE "o" symbol is displayed at the next point where the speed target will automatically step up or down to command an acceleration or a deceleration.

 (5)
 Engine out computation An engine out is detected automatically by the system according to various signals transmitted by the FADECs. During an engine out, in take-off, climb, cruise or go around phase, only the engine out maximum altitude is computed, and no other predictions are available. SPEED AUTO CONTROL is possible, but none of the FM vertical modes (CLB, DES, or FINAL) are available. If the engine-out occurs in descent or approach phase, the same predictions as in twin-engine are computed and the same modes are available (DES and FINAL). It is possible to manually override engine out detection to force the FMS to revert to dual engine state with the EO CLR prompt.

 (6)
 Altitude planning This function computes the distance and time required to reach a predetermined altitude. This calculation is made for the active speed mode (ECON or manual speed) and for the EXPEDITE mode. It is available only in takeoff, climb and descent phase.

 (7)
 Performance factor In order to adjust the aircraft/engine model versus the actual aircraft performance, it is possible to define a performance factor. This value can only be set on ground before engine start.

 (8)
 Overview of alternate The system provides time and fuel predictions for up to 6 alternate destinations defined in data base in the airport file. A seventh airport may be selected by the crew and the NO ALTERNATE option is also evaluated. Airway distance is used in this computation.

 (9)
 Maximum altitudes A maximum recommended altitude is computed and displayed on the MCDU. It uses limitations from the engine max climb thrust, buffeting (0.2 g margin) and max certified altitude. An absolute maximum altitude is computed and limits the CRZ FL entry. It is defined as the previous one except that a 0.3 g buffet margin is used.

 (10)
 Max holding time When the aircraft flies in a holding pattern, the system computes the maximum time the aircraft can remain in the holding pattern. For this computation, it uses the fuel policy, the alternate selection and assumes 0 extra fuel.

 D.
 Operational Use The interface between the crew and the FMS is performed through the various CRTs in the cockpit and particularly the MCDU and the ND. This section deals with the general rules defining the use of these computers from an FMS standpoint. The general use with two FMGCs is also explained. The MCDU is used to select data in the system (pilot entry) and to display most FMS information to the pilot. Although the MCDU is used for various systems (CFDIU, AIDS, ACARS), it is coupled by priority to the FMGC. This means in particular that a direct access to an FMGC page can be obtained by selecting the corresponding mode key. The MCDU keyboard is composed of an alphanumeric part used for pilot entry. When the pilot presses one of these keys, the corresponding symbol is written on the 14th line of the MCDU screen (the scratchpad line). When all data are entered in the scratchpad, the pilot must then press the line select key to insert the information in the scratchpad. It is possible to clear this information partially or entirely by means of the CLR key.

 Specific rules concerning format, possible entries or clearing functions
 are explained in section 22-74-00.
 The MCDU keyboard features several mode/page keys:

 -The MCDU MENU gives access to a menu page which allows selection of the coupling of the MCDU to any other system (Ref. 22-80-00).
 -10 page keys give access to the corresponding pages. Some pages are usually displayed according to the flight phase: INIT and F-PLN pages before takeoff, F-PLN and PERF pages during takeoff, F-PLN and PROG pages during climb, cruise and descent, and F-PLN and PERF pages during approach and go around. Pages may automatically vary in data and format according to the flight conditions. For example, the F-PLN page is modified each time the flight plan is sequenced. Some pages may also give access to other pages through a hierarchy described in section 22-74-00.
 -3 mode keys are used to modify the displayed page when all the information to be displayed does not fit in one page. These keys allow either vertical slewing or horizontal slewing.
 In order to display the information, the FMGC is constrained to satisfy various rules. They are applied also to any other computer linked to the MCDU. These rules concern:
 -data format
 -character size
 -use of various symbols
 -color use. These rules, when applicable are common with the EIS color
 rules. Besides the data displayed by the system through the whole set of pages, the FMGC may also display various messages in the scratchpad. They may be used for:
　
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