TAKEOFF SAFETY TRAINING AID(4)

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There are essentially two sources of additional performance potential, or "margins", inherent to takeoffs performed using the assumed temperature method to reduce thrust. First, since the takeoff performance was initially calculated using full takeoff thrust, the applicable minimum control speed restrictions at full thrust have already been accounted for in determining the limits weights and speeds. Therefore, if at any time during the takeoff, the pilot decides that the safety of the takeoff is in question, the engine thrust may be increased to the full-rated value, without danger of exceeding the minimum control limits.
The second source of additional performance in a flexible temperature takeoff is due to the true airspeed difference that exists between actual temperature and the higher flexible temperature. This results in less actual distance being required for the airplane to reach 35 feet or to come to a stop in an RTO. This appendix contains examples which illustrate these additional margins that are inherent to reduced thrust takeoff calculations using the flexible temperature method.

 

Reduced Thrust Examples
Airbus Model A300B4-203
And example of the conservatism inherent in the use of the assumed (flexible) temperature method of reduced thrust calculation.
Conditions A300B4
GE CF6-50C2
Sea level
O A T = 15°C
8900ft runway
Actual airplane weight = 148 T permits assumed (flexible) temperature of 40°C
Parameters  Actual temp is 15°C and assumed (flexible) temp is 40°C  Actual temp is 40°C  Margin 
N1 (%)  111  111 
V1 (KIAS/TAS)  153 / 153  153 / 159  - 6 KTAS 
VR (KIAS/TAS)  155 / 155  155 / 161  - 6 KTAS 
V2 (KIAS/TAS)  160 / 160  160 / 167  - 7 KTAS 
Thrust at V1, Lbs per engines  37.760  37.760  0 Lbs 
Far field length ---ft  8398  8860  462 ft 
Accelerate-stop distance (engine-out) ---ft  8148  8860  732 ft 
Accelerate-go distance (engine-out) ---ft  8398  8860  462 ft 
Accelerate-go distance (all-engine) ---ft  7735  8300  564 ft 
Second segment gradient %  2.69  2.52  0.0 % 
Second segment rate of climb ---ft per minute  407  425  - 18 Fpm 

 

Reduced Thrust Examples
Airbus Model A310-300
And example of the conservatism inherent in the use of the assumed (flexible) temperature method of reduced thrust calculation.
Conditions A310-300
GE CF680-C2A2
Sea level
O A T = 15°C
10000ft runway
Actual airplane weight = 155 T permits assumed (flexible) temperature of 40°C
Parameters  Actual temp is 15°C and assumed (flexible) temp is 40°C  Actual temp is 40°C  Margin 
　
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