getting to grips with aircraft performance 如何掌握飞机性能 1(38)

.
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”
　
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