(a) AP/FD/A/THR common condition This condition results from the monitoring functions below:
-
monitoring of the validity of the ADIRS input parameters (two ADIRS must be valid). This monitoring consists in a check of the SSM and refreshment period. The monitoring of the main parameters is made by vote or comparison.
-
monitoring of LGCIUs parameters. This monitoring is made in the FAC which informs the FMGC of the validity of the LGCIU parameters. One LGCIU at least must be healthy. This condition is not required at landing or during go around.
-
internal monitoring of the guidance portion healthy.
-
internal monitoring of the management portion healthy. This condition is not required at landing or during go around.
NOTE : The monitoring functions common to the AP/FD and A/THR are
____ described in 22-11-00 AP/FD Engagement.
(b) A/THR specific condition This condition specific to A/THR includes the conditions below:
-A/THR must be either in the manual speed or in the auto speed control mode (Ref. 22-10-00 AP/FD)
-
the two ECUs/EECs must be healthy
-
the FCU must be healthy
-no discrepancy between the N1/EPR target computed in the FMGC and the N1/EPR feedback from each ECU/EEC when the A/THR is active
-the various parameters used in the flight envelope protection such as VLS, VMAX, etc. must be healthy
-no action on one of the two A/THR instinctive disconnect pushbutton switches lasts more than 15s.
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(2)
Disengagement conditions The presence of one of the conditions below causes the disengagement of the A/THR:
(a)
Loss of one common or specific condition described above (loss of the ADIRS or FAC parameter validity does not cause A/THR disengagement as long as the Alpha floor protection is active).
(b)
"Synchronization between FMGC" condition. This condition forces the disengagement if the A/THR function on the opposite FMGC is disengaged and on condition that this FMGC has priority.
(c)
Action on the A/THR pushbutton switch, with the A/THR function already engaged. This action has no effect in LAND TRACK mode.
(d)
Action on one of the A/THR instinctive disconnect pushbutton switches.
(e)
AP/FD loss condition i.e. total loss of AP/FD below 100ft with the RETARD mode not engaged.
(f)
Go around condition i.e. one throttle control lever is placed in the non active area (> MCT) below 100ft without engagement of the GO AROUND mode on the AP/FD.
(g)
One engine start on the ground.
(h)
Both throttle control levers placed in the IDLE position.
(i)
ECU/EEC autothrust control feedback i.e. the A/THR being active at level of the FMGCs, one of the two ECUs/EECs indicates that it is not in autothrust control mode.
(j)
both throttle control levers placed in the REVERSE position.
(3)
A/THR ACTIVE logic After engagement, the A/THR is active if:
-
the two throttle control levers are between IDLE and CL (CL
included)
- one throttle control lever is between IDLE and CL (including CL), and the other is between IDLE and MCT (including MCT) with FLEX TO limit mode not selected
-
the Alpha floor protection is active whatever the position of the throttle control levers.
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D. Realization of the Engage or Disengage Logic (Ref. Fig. 002) The engagement of the A/THR function is duplicated in each FMGC at level of the guidance, command and monitoring channels. The A/THR ENGD signal that the ECUs/EECs receive via the FCU and the EIUs comes from the command channel. The A/THR ENGD C and M discrete outputs used in the A/THR instinctive disconnect circuit (Ref. Para. 2.E.) take into account the result of computation of the command and monitoring channels. The Alpha floor condition from the FACs is used in the command and monitoring processors for the elaboration of the Alpha floor protection. This causes the automatic engagement of the A/THR. When both FACs are healthy, the logic condition makes engagement of the Alpha floor protection only when both FACs deliver the Alpha floor condition. If one FAC is not healty and the Alpha Floor condition is present, the protection is achieved by the other healty FAC. A comparison between the command and monitoring channels at level of this protection is performed. If there is a difference between these channels, the A/THR function is disengaged. The comparison between the computed N1/EPR target and the N1/EPR target feedback sent by each ECU/EEC is performed at level of the command and monitoring channels of each FMGC. Any excessive deviation is taken into account at level of the A/THR engage logic of the command and monitoring channels.
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