**4. The reference and programmed reduced cumulative noise thrust management at take-off and approach**

### **4.1 Take-off**

Conventional TM applied to subsonic jet aeroplanes at take-off is considered as reference TM during the take-off. It includes the take-off and cutback power settings.

The proposed programmed TM using the PLR includes 7 flight path segments: take-off power (segment 1), throttling to power setting providing reduced lateral noise (segment 2), power setting providing reduced lateral noise (segment 3), restoring maximum climb power setting (segment 4), maximum climb power setting (segment 5), throttling to power setting providing reduced flyover noise (segment 6) and power setting providing reduced flyover noise (segment 7).

The throttle ratio value TR is equal to TR = thrust/full thrust,

where thrust corresponds to the thrust value for the current power setting; full thrust corresponds to the thrust value for the maximum power setting at the current flight conditions.

The **Figure 3** shows the changes of the take-off thrust throttle ratio TRto depending on the distance from the brake release point and used take-off TM applied to SCA with MTOM of 55 000 kg and turbofan with BPR = 2.5.

The main purposes of the flight path segments are following:


The power settings on the segments 3 and 7 correspond to the lower power settings, providing the lateral and flyover noise reduction accounting the airworthiness and noise certification procedure restrictions in term of the minimal climb gradients [6].

**Figure 3.**

*The change of the take-off thrust throttle ratio TRto depending on the distance from the brake release point for reference and programmed take-off TM.*

The proposed programmed TM includes rational choice of the TM parameters like the location of the beginning and end points of the segment 3, the beginning point of the segment 7, the thrust throttle ratio on the segments 3 and 7, the thrust acceleration and throttling rates on the segments 2, 4 and 6 (see **Figure 3**). All parameters are optimized in the paper under the minimum take-off noise criteria.

As seen in the **Figure 3**, the optimal take-off throttle ratio TRto values for the segment 3 and in beginning point of the segment 7 are equal to 0.8 (i.e. the engine power should be reduced by 20% vs. maximum power setting) and 0.74 (i.e. the engine power should be reduced by 26%) accordingly. The optimal distances for location of the beginning and end points of the segment 3 and the beginning point of the segment 7 should be equal to 2300, 4000 and 5800 m respectively. The optimal take-off thrust throttling rates on the segments 2 and 6 should be equal to 15 and 2.5% of thrust per a minute.

The **Figure 4** shows the SBJ flight path for the turbofan with BPR = 2.5 using the reference and programmed take-off TM.

Despite the fact that the use of programmed TM leads to a lower initial climb trajectory (see **Figure 4**), it is possible to recover the altitude above the flyover RP. It is mainly obtained due to the optimal choice of the programmed TM parameters, impacted on the flight above RP.

#### **4.2 Approach**

The conventional TM applied to the subsonic jet aeroplanes at approach providing the approach flight path with the glide slope angle θ = −3o is considered as the reference approach TM. It usually includes use of the engine power setting close or equal to the flight idle.

The proposed programmed approach TM includes the use of the engine power setting lower than the flight idle.

*Estimation of Cumulative Noise Reduction at Certification Points for Supersonic Civil… DOI: http://dx.doi.org/10.5772/intechopen.97465*

**Figure 4.**

*The SBJ take-off SBJ flight path for turbofan with bypass ratio BPR = 2.5 using reference (green line) and programmed (red line) take-off TM.*

#### **Figure 5.**

*The change of approach thrust throttle ratio TRapp depending on the glide slope angle* θ *and bypass ratio BPR for the reference (at* θ *=* −*3 o ) and programmed (at* θ *higher than -3o ) approach TM.*

**Figure 5** shows the change of approach thrust throttle ratio TRapp depending on the glide slope angle θ and engine BPR.

It can be seen that with an increase in the angle θ from −3 to-6<sup>o</sup> , the approach throttle ratio TRapp decreases from 0.2 to 0.11–0.12. At the same time, a change

**Figure 6.**

*The SBJ approach flight paths with the different glide slope angles*θ *for and turbofan with bypass ratio BPR = 2.5.*

of BPR in the range from 2.5 to 5.0 practically does not affect the change of the engine power setting.

On the **Figure 6** SCA approach paths with different glide slope angle θ are presented for turbofan with BPR = 2.5. Changing the engine power setting and θ leads to an increase of the flight altitudes above the approach RP, located at a distance of 2000 m from the runway threshold.

The flight altitudes above the approach RP does not change with a change of BPR. And at the same time it significantly increases (by about 100 m) with an increase of the angle θ from −3 to -6o (**Figure 6**).
