.
MEL conditions (i.e., thrust reversers, brake unit, anti-skid or ground spoilers inoperative); and,
.
In-flight system malfunctions resulting in an increased final approach speed, or affecting the lift-dumping or braking capability.
These factors are discussed hereafter and illustrated in Figure 4.
Airfield elevation:
Airfield elevation or a corresponding low QNH value results in a higher TAS and ground speed and, thus, in a greater landing distance.
At 1000-ft airfield elevation or at sea level with an equivalent pressure altitude (i.e. with a low QNH of 980 hPa), the landing distance is increased by 5 % to 10 % (factor 1.05 to 1.10).
Getting to Grips withApproach-and-Landing Accidents Reduction
Runway profile (sl ope):
All Airbus aircraft models are certified for landing operation on runways not exceeding a mean downhill slope of 2%.
The applicable operational regulation (JAR-OPS) requires to account for the runway slope only when the downhill slope exceeds 2%.
Therefore, the landing distance tables published in the FCOM and QRH are applicable without correction within the certified envelope.
The following information is provided for enhanced understanding only.
The runway profile (i.e., downhill slope) affects the landing distance without autobrake.
A 1 % downhill slope increases the landing distance without autobrake by 2 % (factor 1.02).
When autobrake is used, the selected deceleration rate is achieved regardless of the runway slope.
Runway conditions:
Runway contamination increases the rolling drag (i.e., the displacement drag) and the aerodynamic drag (i.e., the impingement drag) but also decreases the braking efficiency.
The following landing distance factors are typical on a contaminated runway:
Factors
Wet 1.3 to 1.4
Standing water or slush 2.0 to 2.3
Compacted snow 1.6 to 1.7
Ice 3.5 to 4.5
Table 1
Landing Distance Factors - Contaminated Runway
Factors Affecting Landing Distance
Page 2
AIRBUS INDUSTRIE
Flight Operations Support
Briefing Note 8.5 - Landing on Contaminated Runway provides expanded and illustrated information for operation on runway contaminated with standing water, slush, snow or ice.
Wind conditions:
In accordance with certification requirements and operational regulations, the published landing distance factors account for:
.
50 % of the head wind component; and,
.
150 % of the tail wind component.
Note :
In case of gusting crosswind, a tailwind component
may exist but is not reported. This condition may be
undetected and therefore be not accounted for.
Type of braking:
Actual landing distances are demonstrated during certification flight tests using the following technique:
.
Flying an optimum flight segment from 50 ft over the runway threshold down to the flare point;
.
Performing a firm touchdown; and,
.
Using full pedal braking, upon main landing gear touchdown.
The published actual landing distances seldom can be achieved in revenue service.
The landing distances published for automatic landing with use of autobrake provide more achievable references for line operations.
Speed Over Runway Threshold:
The actual landing distance ( LD ) is a direct function of the kinetic energy ( E ) to be absorbed.
For an aircraft crossing the runway threshold at a given gross-weight ( GW ) and at the final approach speed ( V APP ), the kinetic energy is:
E = . .GW.( V APP ) 2
Getting to Grips withApproach-and-Landing Accidents Reduction
At given gross weight ( GW ), any increment of or deviation from V APP results in a corresponding increase of energy ( DE ) such that:
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