ED Decision 2021/005/R
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.
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.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 < 70Â % 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 15Â % 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 |
Landing distance (ALD) is from screen height to full stop on dry runway. LDA must exceed ALD by factors: 1.43 for dry, 1.64 for wet when AFM lacks wet data.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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