Operators must take into account the runway slope, when its value is greater than ± 2%. Otherwise, it is considered to be null. 

In the event of an aircraft system failure, known prior to dispatch and affecting the landing distance, the available runway length must at least be equal to the required landing distance with failure. This distance is equal to the required landing distance without failure multiplied by the coefficient given in the MMEL, or to the performance with failure given by the Flight Manual. 

4.1.1. RLD Dry Runways 

The aircraft’s landing weight must permit landing within 60% of the Landing Distance Available at both the destination and any alternate airport. That gives: 

RLD dry = ALD / 0.6 ≤ LDA 

4.1.2. RLD Wet Runways 

If the surface is wet, the required landing distance must be at least 115% of that of a dry surface. 

RLD wet = 1.15 RLD dry ≤ LDA 

A landing distance on a wet runway, shorter than that above but no less than that required on a dry runway, may be used if the Airplane Flight Manual includes specific additional information about landing distances on wet runways. This is not generally the case for Airbus aircraft. 

4.1.3. RLD Contaminated Runways 

For JAR operators, if the surface is contaminated, the required landing distance must be at least the greater of the required landing distance on a wet runway and 115% of the landing distance determined in accordance with approved contaminated landing distance data. 

ALD contaminated x 1.15  

RLD contaminated = the greatest of or RLD wet  

For contaminated runways, the manufacturer must provide landing performance for speed V at 50 feet above the airport, such that: 

1.23 VS1g ≤ V ≤ 1.23 VS1g + 10 kt 

In certain contaminated runway cases, the manufacturer can provide detailed instructions such as antiskid, reverse, airbrakes, or spoiler. And, in the most critical cases, landing can be prohibited. 

4.1.4. RLD with Automatic Landing (DRY) 

Regulations define the required landing distance for automatic landing as the actual landing distance in automatic landing multiplied by 1.15. 

This distance must be retained for automatic landing, whenever it is greater than the required landing distance in manual mode. 

4.2. Go-Around Requirements 

4.2.1. Normal Approach 

During dispatch, only the approach climb gradient needs to be checked, as this is the limiting one. 

The minimum required gradient is the one defined during aircraft certification 

(C.f. 3.3.1 Approach Climb). Operators have a choice of go-around speed (from 1.23 VS1g to 1.41 VS1g), and configuration (3 or 2) to determine the Maximum weight limited by go-around gradient. 

In the rare case of a go-around limitation during dispatch, operators can select CONF 2 and 1.4 VS1g for go-around calculation, and should no longer be limited. Nevertheless, even if the regulation authorizes such assumptions, it is important to warn pilots about the speed and configuration retained, as soon as they are not standard (CONF 3 and 1.23 VS1g). 

In a normal approach, the required climb gradient is 2.1% for twin and 2.7% for four engine aircraft, independently of airport configuration and obstacles. During dispatch, operators can account for the gradient published in the airport approach chart. 

4.2.2. CAT II or CAT III Approach 

“JAR-OPS 1.510 

(a) For instrument approaches with decision heights below 200 ft, an operator must verify that the approach mass of the aeroplane, taking into account the take-off mass and the fuel expected to be consumed in flight, allows a missed approach gradient of climb, with the critical engine failed and with the speed and configuration used for go-around of at least 2.5%, or the published gradient, whichever is the greater. The use of an alternative method must be approved by the Authority”. 

In case of a CAT II/III approach, the gradient is 2.5% (all aircraft types) or more if the approach charts require a higher value for obstacle consideration. 

4.3. Conclusion 

. Landing weight must satisfy the structural constraints. So, the first limitation is: 

LW ≤ maximum structural landing weight 

. Landing weight is limited by aircraft performance (runway limitation and go-around limitation). Thus, the second condition is: 

LW ≤ maximum performance landing weight 

. Therefore, from these two conditions, it is possible to deduce the expression of the maximum allowed landing weight called maximum regulatorylanding weight (MLW):