Where certification of installations involving more than one type of precision approach system (e.g. ILS and MLS and/or GLS) is requested, the following considerations should be taken into account:
- (a) Where practicable, the flight deck procedure for the xLS precision approach should be the same. - (b) The loss of deviation data should be indicated on the deviation display. The failure indication on the deviation display for each axis of the xLS may be common. - (c) The specific precision approach system selected as the navigation source for the approach and automatic landing should be indicated positively in the primary field of view (FOV) at each pilot station. - (d) The ILS frequency or MLS/GLS channel data for the selected approach should be displayed to each pilot. - (e) Means should be provided to enable the flight crew to confirm that the intended type of approach system has been correctly selected. - (f) A common set of mode indications for the armed and active conditions is recommended. - (g) The capability of each element of a multi-mode landing system should be available to the flight crew to support dispatch of the aeroplane. - (h) A failure of each element of a multi-mode landing system should be indicated to the flight crew as either an advisory or a caution, during en-route operation. - (i) A failure of the selected element of a multi-mode landing system during an approach should be accompanied by a warning or caution, as appropriate. These alerts may be inhibited at the alert height, if appropriate to the operation. - (j) If an indication of a failure in each non-selected element of a multi-mode landing system during an approach and landing is provided, it should be available to the flight crew as an advisory and should not produce a caution or warning. These advisories may be inhibited at the alert height, if appropriate to the operation. - (k) Failure indications should not mislead the flight crew through a possible incorrect association with the navigation source. For example, it would be unacceptable for ' ILS FAIL ' to be displayed when the selected navigation source is MLS and the failure affects the MLS receiver. - (l) If a HUD (or equivalent display) is used to display approach guidance, an additional aural indication is desirable when the aeroplane reaches the preselected DH.
[Issue: CS-AWO/2]
(See AMC AWO.A.ALS.112)
The effects of failures of the navigation means (facilities external to the aircraft, including signal-in-space (if utilised)) shall be investigated taking into account the Standards and Recommended Practices (SARPs) of ICAO Annex 10 relevant to the characterisation of failures (e.g. monitor thresholds, time-to-alert and transmitter changeover or shutdown times).
[Issue: CS-AWO/2]