AMC1 SPA.HOFO.160(c)(2) Helicopter terrain awareness and warning system (HTAWS)

CAA ORS9 Decision No. 26

HTAWS configured for offshore operations should meet all of the following criteria:

(a) The acceptable standard referred to in SPA.HOFO.160(c)(2) is as follows:

(1) For new HTAWS installations and upgrades to existing HTAWS installations performed prior to 1 January 2025 the HTAWS should be granted with ETSO-C194 approval and meet the criteria detailed in (b) through (e) below utilising the alert envelopes defined in UK CAA CAP 1519.

(2) For new HTAWS installations and upgrades to existing HTAWS installations performed from 1 January 2025 the HTAWS should meet the requirements of ETSO-2C522 including Mode 7a or, alternatively, be demonstrated to be compliant with technical requirements set out in EUROCAE ED-285/RTCA DO-376 including Mode 7a. The HTAWS should also provide altitude callouts meeting the requirements of CAT.IDE.H.145 and SPA.HOFO.160(a)(2).

(b) The HTAWS should provide caution and warning alerts, with at least an aural indication, for at least the following conditions:

(1) Mode 1: Excessive rate of descent;

(2) Mode 3: Loss of airspeed or height after take-off;

(3) Mode 4: Flight into terrain when not in landing configuration/gear position warning;

(4) Mode 5: Excessive downward deviation from an instrument approach glidepath;

(5) Mode 6: Altitude callouts meeting the requirements of CAT.IDE.H.145 and SPA.HOFO.160(a)(2).

(6) Mode 7: Loss of airspeed/low energy state on approach.

The functionality provided by the Offshore Envelopes listed in points (1) to (6) above must be available throughout all normal flight conditions.

(c) The HTAWS should provide aural alerts that meet the following criteria:

(1) The aural alerts should be appropriately prioritised;

(2) The implementation of the aural alerts should be consistent with the design philosophy of the aircraft type;

(3) The aural alerts should be continuously provided until the condition for alerting the crew no longer exists.

(d) Where provided, HTAWS visual alerts should meet the following criteria:

(1) The visual alerts should be consistent with the design philosophy of the aircraft type;

(2) Caution alerts should be indicated using an amber indicator light. This may be supplemented with an amber text message that is obvious, concise, and consistent with the aural message;

(3) Warning alerts should be indicated using a red indicator light. This may be supplemented with a red text message that is obvious, concise, and consistent with the aural message.

(e) Where the HTAWS includes alerting functions that are not specifically designed for offshore operations, these should be segregated from the dedicated offshore functionality. Automatic transition to and from the offshore mode on crossing the coastline may be provided. However, manual selection and the ability for the pilot to override the automatic transition by manually selecting the desired mode should always be provided. A clear indication should be given to the pilot of the selected mode of operation.