Approach Techniques Aircraft Energy Management during Approach(6)

Comply with the engine and aircraft certification requirements (U.S. FAR – Part 33 and FAR – Part 25, respectively, or the applicable equivalent regulation).

The engine certification (FAR – Part 33) ensures a time of 5 seconds or less to accelerate from 15 % to 95 % of the go-around thrust. 
The aircraft certification (FAR – Part 25) ensures that the thrust achieved after 8 seconds from power application (starting from flight/approach idle) allows a minimum climb gradient of 3.2 % for go-around.
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 4
Certified Thrust Response –Typical
Go-around from Low Speed / Low Thrust

Table 1 indicates the thrust required (in % of the TOGA thrust) in order to achieve the following maneuvers:
 
Maneuvers
 % of TOGA Thrust
 
Flying a stabilized approach  (3-degree glide path / VAPP)
 20 %
 
Arresting altitude loss and achieving level flight
 30 %
 
Achieving “Positive Climb”
 > 30 %
 

Table 1
Thrust Required during GA Initiation

Figure 5 illustrates the go-around trajectories associated with flying an approach with:
Speed on the target final approach speed (VAPP) with idle thrust;

Speed below VAPP (VAPP – 10 kt) with idle thrust.

In case of go-around, the initial altitude loss and the time required for recovering  the initial altitude are increased if airspeed is lower than the final approach speed and/or if thrust is set at idle. In particular, the effect of lack of thrust (i.e. thrust at idle) is significant in terms of altitude loss.
　
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