AWO.A.HUD.112 CS AWO.A.HUD.112 Head-up display landing distance

- (a) The following definitions should apply when considering the concept of a flare cue: - (1) 'flare cue' : a flare cue is specific symbology displayed on the HUD that supports the flare manoeuvre; for this purpose, a flare cue may be implemented as a 'flare prompt' or 'flare guidance'. - (2) 'flare prompt' : a flare prompt advises the pilot when it is time to initiate the control inputs for the flare manoeuvre and transition to landing; a flare prompt should not provide command guidance for manoeuvring the aeroplane with regard to the rate or magnitude of manual inputs, alignment to runway heading nor touching down at a specific point on the runway. - (3) 'flare guidance' : provides explicit command guidance for the pilot to flare the aircraft from the initiation of the manoeuvre until touchdown. - (b) The term 'flare cue' is used in this AMC as a general term that describes either a 'flare prompt' or 'flare guidance'. - (c) The determination of the landing distance when using a HUD or equivalent display should be performed when one of the following features are part of the intended design: - (1) flare guidance; - (2) a flare prompt in combination with flare guidance; or - (3) a flare prompt, if the height at which the flare is prompted differs from the one at which the landings without using the HUD or equivalent display are performed to the extent that it could have an impact on the landing distance. - (d) A flare cue provided on a HUD or equivalent display is typically provided in the vertical axis by means of a symbol that prompts the pilot to initiate the flare at a suitable moment, and can guide the pilot to control the vertical flight path to touchdown. - (e) For a HUD or equivalent display that is used for landing and designed to provide display features such as a flare cue to support the pilot's task of executing the landing: - (1) The landing distance assessment should cover all the conditions scheduled in the AFM, including landing in abnormal conditions and, if applicable, specific operations. - (2) The requirements of CS 25.125 should be applied, except that the configuration, procedure and speed should be those recommended in the associated procedures for using a HUD or equivalent display. - (3) The operating procedures, aeroplane configuration, approach speed, thrust management, piloting techniques and the landing distance data applicable for landings using a HUD or equivalent display with a flare cue should be furnished in the AFM.

- (4) The landing distance as derived under (e)(2) should be compared with the landing distance determined without the flare cue (unfactored landing distance as per CS 25.125):

(i)If the landing distance using the flare cue is longer than without it, the unfactored landing distance with flare cue is the one derived under (e)(2).

(ii)If the landing distance is the same (flare cue does not modify the air time and speed reduction), then the unfactored landing distance with flare cue is equal to the landing distance established in accordance with CS 25.125. A minimum factor to be applied to the unfactored landing distance with flare cue should be determined to account for the difference between:

(A)the flight path angle used in the analysis for compliance with the specifications of CS 25.125 and that which is used for the flare cue (typically -3.0°);

(B)the touchdown sink rate used in the analysis for compliance with the specifications of CS 25.125 and the one as per the intended design of the flare cue.

The AFM should provide the unfactored landing distance with the flare cue and the minimum factor as determined above.

- (iii) In any case, the landing distance may not be shorter than the landing distance established in accordance with CS 25.125 without using the flare cue.

[Issue: CS-AWO/2]