Airbus A318 [Archive] - PPRuNe Forums

Fargoo

2nd Apr 2009, 18:42

Steep Approach Landing Function of the EFCS.

G. Steep Approach Landing (SAL) Function

(1) General

This function allows operation of the A/C on specific airports where the flight path angle is steeper than 4.5 degrees (instead of 3 degrees).
(2) Activation of the steep approach landing function

The activation of the SAL function is dependent on:
- the function pre-selection by the pilot through the dedicated pushbutton switch,

- normal laws availability,

- correct servo-loop of speedbrakes 3 and 4 (SEC1, Blue and Yellow hydraulic power available),

- slats and flaps in FULL configuration,

- speedbrakes extended.

When the SAL function is active, the following modifications are selected within the ELACs:
- adjustment of the angle of attack protection value to avoid activation of the AOA protection in turn or during flare, to avoid retraction of the speedbrakes and to always keep the same margin between Alpha approach and Alpha prot.
This also includes modification of alpha protection threshold before flare.

- increase of the roll side stick pre-command to compensate for the loss of roll efficiency due to the speedbrake extension.

- modification of spoiler retraction conditions.

- spoilers automatic retraction and modification of Nz command law in order to facilitate the flare maneuver.
The ELACs send the status of the SAL function activation on their output bus. This data is necessary:

- for the FACs to select the suitable characteristic speeds,

- for the FWCs (via the FCDCs) and for the EIS to display memos and warnings,

- for the SECs to select the specific speedbrake deflection,

- for the FMGC to select adequate ATHR/AP/FD settings.
Speedbrakes n 4/3/2 are deflected by 30/30/0 degrees instead of 25/25/12.5 degrees, then before the flare, the speedbrakes are partially and automatically retracted from 30/30/0 degrees to 8/8/0 degrees.
In case of go-around, or AOA protection activation, or alpha floor activation, the speedbrake retraction speed is increased from 5 degrees/sec. to 20 degrees/sec. to improve A/C performance.

Aileron Droop (no different to 319/320?

Roll control surface Kinematics

Full authority of surfaces is:
- + or - 25 deg for the ailerons,

- maximum deflection of 35 deg for the spoilers.
The spoilers 2, 3, 4 and 5 use the same deflection; from configuration 0 to configuration 3, a threshold is included to minimize the drag.
A 5 deg downward deflection of the ailerons ( droop ) is active when the flaps are extended. This position is identified by an index on the AIL scale of the ECAM F/CTL page (Ref 31-51).

- The aileron droop function is ensured by each ELAC.

- The aileron droop function is active on ground or in flight when the flaps are extended; in that case, a 5 deg downward deflection of the ailerons is ordered by the ELAC1 (or by the ELAC2 if it is active on the control of the ailerons).

- The aileron droop function is available as long as one ELAC is able to control the ailerons.

- The ailerons are normally controlled by the ELAC1 through the left Blue and the right Green servo-controls (active mode). The ELAC2 is in stand-by, and the associated servo-controls are in damping mode.
In case of ELAC1 failure, the control of the ailerons is automatically transferred to the ELAC2 which becomes active through the left Green and right Blue servo-controls; in that case, the servo-controls dedicated to the ELAC1 revert to the damping mode.
In case of double ELAC failure, or Blue and Green hydraulic low pressure, all ailerons servo-controls are in the damping mode

EGPWS Steep Approach difference

(h) Steep Approach case:

Steep Approach logic applies when Steep Approach discrete is grounded. When Steep Approach discrete is grounded, Steep Approach Mode 1 envelopes are used and alerts are inhibited below 130ft RA effective in order FWC Steep Approach Callouts to be heard for flare preparation. But if a Mode 1 alert was present above 130ft and alerting conditions are still present while crossing 130ft RA, the alert is not inhibited.
NOTE: The pilot manually selects Steep Aproach function by pressing the STEEP APPR pushbutton on 22VU overhead panel.

From what I can see the only test for the system in maintenance is to check that it cannot be armed with either or both ELACs switched off.

Pilot indication appears to be a Green STEEP APPR Memo on ECAM + a checklist.

Hope all this helps :ok: