These paper documents are referred to as “Regulatory TakeOff Weight” charts (RTOW). The charts must be generated for each runway heading, and can be produced for different takeoff conditions at the convenience of the applicant (temperature, wind, QNH, flap setting, runway status, inoperative items). 

They provide the: 

Maximum Takeoff Weight (MTOW) 

Takeoff speeds (V1,VR,V2) 

Limitation code 

Minimum and maximum acceleration heights. 

Figure C29 shows an example of an A319 RTOW chart. 

Example: MTOW and speeds determination 

DATA 

Takeoff from Paris-Orly, Runway 08 

Slat/Flap configuration: 1+F 

 

OAT = 24oC 

Wind = Calm 

QNH = 1013 hPa 

Air conditioning: Off 

Runway state: Dry 

RESULT 

MTOW = 73.6 tons 

 V1 = 149 Kt, VR = 149 Kt, V2 =153 Kt 

MTOW limited by: second segment and obstacle(2/4) 

Note: In case of deviation from the chart reference conditions (QNH, air conditioning…), corrections have to be applied to the MTOW and the speeds. 

7. FLEXIBLE AND DERATED TAKEOFF 

The aircraft actual takeoff weight is often lower than the maximum regulatory takeoff weight. Therefore, in certain cases, it is possible to takeoff at a thrust less than the Maximum Takeoff Thrust. It is advantageous to adjust the thrust to the actual weight, as it increases engine life and reliability, while reducingmaintenance and operating costs. 

These takeoff operations generally fall into two categories: Those using the reduced thrust concept, known as flexible takeoffs in the Airbus world, and those using a specific derated thrust level named derated takeoffs. 

7.1. Flexible Takeoff 

A takeoff at reduced thrust is called a flexible takeoff, and the corresponding thrust is called flexible thrust. 

7.1.1. Definition 

“AMJ 25-13 / AC 25-13 (4)(c) Reduced takeoff thrust, for an aeroplane, is a takeoff thrust less than the takeoff (or derated takeoff) thrust. The aeroplane takeoff performance and thrust setting are established by approved simple methods, such as adjustments, or by corrections to the takeoff thrust setting and performance.” 

In this case, “the thrust for takeoff is not considered as a takeoff operating limit.” 

As shown in Figure C30, the actual takeoff weight is less than the maximum permissible takeoff weight obtained from a RTOW chart. Therefore, it is possible to determine the temperature at which the needed thrust would be the maximum takeoff thrust for this temperature. This temperature is called “flexible temperature  (TFlex)” or “assumed temperature”. Moreover: 

“AMJ 25-13 / AC 25-13 (5)(a) The reduced takeoff thrust setting 

(2) Is based on an approved takeoff thrust rating for which complete aeroplane performance data is provided 

(3) Enables compliance with the aeroplane controllability requirements in the event that takeoff thrust is applied at any point in the takeoff path 

(4) Is at least 75% of the maximum takeoff thrust for the existing ambient conditions” 

Consequently, the flexible temperature is the input parameter through which the engine monitoring computer adapts the thrust to the actual takeoff weight. This method is derived from the approved maximum takeoff thrust rating, and thus uses the same certified minimum control speeds. 

In addition, thrust reduction cannot exceed 25% of the maximum takeoff thrust, thus leading to a maximum flexible temperature, as shown in Figure C30. 

To comply with the above requirements, flexible takeoff is only possible when the flexible temperature fulfils the following three conditions: 

TFlex > TREF TFlex > OAT TFlex ≤ TFlex Max 

Regulations require operators to conduct periodic takeoff demonstrations, using the maximum takeoff thrust setting, in order to check takeoff parameters (N1, N2, EPR, EGT). The time interval between takeoff demonstrations may be extended, provided an approved engine condition-monitoring program is used. 

7.1.2. Flexible Takeoff and Runway State 

“AMJ 25-13 / AC 25-13 

(f) The AFM states that [reduced thrust takeoffs] are not authorised on contaminated runways and are not  authorised on wet runways unless suitable performance accountability is made for the increased stopping distance on the wet surface". 

Airbus operational documentation (RTOW, FCOM) provides performance information for flexible takeoffs on wet runways. As a result, a flexible takeoff is allowed on a wet runway, while it is forbidden on a contaminated one.