GM2 CAT.POL.A.230 & CAT.POL.A.235 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 actual landing distance (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.

As a matter of fact, any particular landing may be different from the landing technique that is 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.230 and CAT.POL.A.235 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.230, are shown in the following Table 1.

Table 1: Corrective factors for dry runways

Aeroplane category	Required margin (dry runway)	Resulting factor (dry runway)
Turbojet-powered aeroplanes	ALD < 60 % of the LDA	LDA = at least 1.67 x ALD
Turbopropeller-powered aeroplanes	ALD < 70 % of the LDA	LDA = at least 1.43 x ALD
Aeroplanes approved under CAT.POL.A.255	ALD < 80 % of the LDA	LDA = at least 1.25 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.235, as shown in the following Table 2.

Table 2: Corrective factors for wet runways

Aeroplane category	Resulting factor (dry runway)
Turbojet-powered aeroplanes	LDA = at least 1.15 x 1.67 x ALD = 1.92 x ALD
Turbopropeller-powered aeroplanes	LDA = at least 1.15 x 1.43 x ALD = 1.64 x ALD
Aeroplanes approved under CAT.POL.A.255	LDA = at least 1.15 x 1.25 X ALD = 1.44 x ALD

However, for aeroplanes that are approved under CAT.POL.A.255, when landing on wet runways, CAT.POL.A.255 further requires the flight crew to apply the longer of the landing distance resulting from the above table and the landing distance resulting from the application of CAT.OP.MPA.303(a) or (b) as applicable. If performance information for the assessment of LDTA is not available as per CAT.OP.MPA.303(b)(2), the required landing distance on wet runways should be at least: 1.15 x 1.67 x ALD for turbojet-powered aircraft and 1.15 x 1.43 x ALD for turbopropeller-powered aircraft.