GM1 CAT.POL.A.430 & CAT.POL.A.435 Landing — dry runways & Landing — wet and contaminated runways

CAA ORS9 Decision No. 15

LANDING DISTANCES AND CORRECTIVE FACTORS

The AFM provides performance data for landing distance under conditions defined in the applicable certification standards. This distance, commonly referred to as the ALD, is the distance from the position on the runway of the screen height to the point where the aeroplane comes to a full stop on a dry runway.

The determination of the ALD is based on the assumption that the landing is performed in accordance with the conditions and the procedures set out in the AFM on the basis of the applicable certification standards.

Operator landing technique may differ from that assumed in the AFM for certification purposes. The aircraft may approach the runway faster and/or higher than assumed; the aircraft may touch down further along the runway than the optimum point; the actual winds and other weather factors may be different from those assumed in the calculation of the ALD; and maximum braking may not be always achievable. For this reason, the LDA is required by CAT.POL.A.430 and CAT.POL.A.435 to be longer than the ALD.

The margins by which the LDA shall exceed the ALD on dry runways, in accordance with CAT.POL.A.430, are shown in the following Table 1.

Table 1: — Corrective factors for dry runways

Aeroplane category	Required Margin (dry runway)	Resulting factor (dry runway)
All aeroplanes	ALD < 70 % of the LDA	LDA = at least 1.43 x ALD

If the runway is wet and the AFM does not provide specific performance data for dispatch on wet runways, a further increase of 15 % of the landing distance on dry runways has to be applied, in accordance with CAT.POL.A.435, as shown in the following Table 2.

Table 2: Corrective factors for wet runways

Aeroplane category	Resulting factor (dry runway)
All aeroplanes	LDA = at least 1.15 x 1.43 x ALD = 1.64 x ALD