fix(fms): fix prediction crash due to invalid thrust limit prediction (…

…#9719) Fix thrust limit prediction Co-authored-by: Benjamin Dupont <[email protected]>
flybywiresim · Jan 9, 2025 · 1ca1ea9 · 1ca1ea9
1 parent 42bb339
commit 1ca1ea9
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Showing 8 changed files with 112 additions and 120 deletions.
diff --git a/fbw-a32nx/src/systems/fmgc/src/flightplanning/A320AircraftConfig.ts b/fbw-a32nx/src/systems/fmgc/src/flightplanning/A320AircraftConfig.ts
@@ -57,36 +57,23 @@ const engineModelParams: EngineModelParameters = {
   numberOfEngines: 2,
   fuelBurnFactor: 1.0,
   cn1ClimbLimit: [
-    [0, 2000, 5000, 8000, 12000, 15000, 17000, 20000, 24000, 27000, 31000, 35000, 39000, 41500],
-    [-54.0, 71.8, 73.6, 75.5, 76.8, 78.1, 78.9, 80.1, 81.5, 81.6, 83.0, 83.6, 83.7, 83.3],
-    [-50.0, 72.5, 74.3, 76.2, 77.5, 78.8, 79.6, 80.9, 82.2, 82.4, 83.8, 84.4, 84.5, 84.0],
-    [-46.0, 73.1, 75.0, 76.9, 78.2, 79.5, 80.3, 81.6, 83.0, 83.1, 84.5, 85.1, 85.3, 84.8],
-    [-42.0, 73.8, 75.6, 77.6, 78.9, 80.2, 81.0, 82.3, 83.7, 83.8, 85.3, 85.9, 86.0, 85.5],
-    [-38.0, 74.4, 76.3, 78.2, 79.6, 80.9, 81.7, 83.0, 84.4, 84.6, 86.0, 86.6, 86.7, 86.3],
-    [-34.0, 75.0, 76.9, 78.9, 80.3, 81.6, 82.4, 83.7, 85.1, 85.3, 86.7, 87.3, 87.5, 87.0],
-    [-30.0, 75.7, 77.6, 79.6, 80.9, 82.2, 83.1, 84.4, 85.8, 86.0, 87.5, 88.1, 88.2, 87.7],
-    [-26.0, 76.3, 78.2, 80.2, 81.6, 82.9, 83.8, 85.1, 86.5, 86.7, 88.2, 88.8, 88.9, 88.4],
-    [-22.0, 76.9, 78.8, 80.9, 82.2, 83.6, 84.4, 85.8, 87.2, 87.4, 88.9, 89.5, 89.6, 89.1],
-    [-18.0, 77.5, 79.5, 81.5, 82.9, 84.2, 85.1, 86.5, 87.9, 88.1, 89.6, 90.2, 90.0, 89.5],
-    [-14.0, 78.1, 80.1, 82.1, 83.5, 84.9, 85.8, 87.1, 88.6, 88.8, 90.3, 90.0, 89.2, 88.7],
-    [-10.0, 78.7, 80.7, 82.8, 84.2, 85.6, 86.4, 87.8, 89.3, 89.5, 91.0, 89.2, 88.4, 87.9],
-    [-6.0, 79.3, 81.3, 83.4, 84.8, 86.2, 87.1, 88.5, 90.0, 90.1, 91.1, 88.5, 87.7, 87.1],
-    [-2.0, 79.9, 81.9, 84.0, 85.5, 86.8, 87.7, 89.1, 90.6, 90.8, 90.2, 87.7, 86.9, 86.4],
-    [2.0, 80.5, 82.5, 84.6, 86.1, 87.5, 88.4, 89.8, 91.3, 90.3, 89.5, 87.0, 86.2, 85.6],
-    [6.0, 81.1, 83.1, 85.3, 86.7, 88.1, 89.0, 90.4, 90.5, 89.5, 88.8, 86.3, 85.5, 84.9],
-    [10.0, 81.6, 83.7, 85.9, 87.3, 88.7, 89.7, 90.0, 89.6, 88.7, 88.1, 85.6, 84.8, 84.2],
-    [14.0, 82.2, 84.3, 86.5, 87.9, 89.4, 89.3, 89.1, 88.7, 87.9, 87.5, 84.8, 83.9, 83.3],
-    [18.0, 82.8, 84.9, 87.1, 88.5, 88.6, 88.4, 88.3, 87.9, 87.2, 86.8, 86.8, 86.8, 86.8],
-    [22.0, 83.4, 85.5, 86.9, 88.0, 87.8, 87.7, 87.5, 87.2, 86.5, 86.1, 86.1, 86.1, 86.1],
-    [26.0, 83.9, 85.7, 86.2, 87.2, 87.1, 87.0, 86.8, 86.5, 85.8, 85.4, 85.4, 85.4, 85.4],
-    [30.0, 84.5, 84.9, 85.4, 86.5, 86.4, 86.3, 86.1, 85.8, 85.1, 85.1, 85.1, 85.1, 85.1],
-    [34.0, 83.8, 84.2, 84.7, 85.8, 85.7, 85.6, 85.5, 85.1, 85.1, 85.1, 85.1, 85.1, 85.1],
-    [38.0, 83.0, 83.4, 83.9, 85.1, 85.0, 84.9, 84.8, 84.8, 84.8, 84.8, 84.8, 84.8, 84.8],
-    [42.0, 82.2, 82.6, 83.1, 84.4, 84.4, 84.3, 84.3, 84.3, 84.3, 84.3, 84.3, 84.3, 84.3],
-    [46.0, 81.4, 81.8, 82.4, 83.7, 83.7, 83.7, 83.7, 83.7, 83.7, 83.7, 83.7, 83.7, 83.7],
-    [50.0, 80.6, 81.1, 81.6, 83.0, 83.0, 83.0, 83.0, 83.0, 83.0, 83.0, 83.0, 83.0, 83.0],
-    [54.0, 79.9, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4, 80.4],
-    [58.0, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2, 79.2],
+    [-2000, 30.8, 56.87, 80.28, 72.0],
+    [2000, 20.99, 48.157, 82.58, 74.159],
+    [5000, 16.139, 43.216, 84.642, 75.737],
+    [8000, 7.342, 38.17, 86.835, 77.338],
+    [10000, 4.051, 34.518, 88.183, 77.999],
+    [10000.1, 4.051, 34.518, 87.453, 77.353],
+    [12000, 0.76, 30.865, 88.303, 78.66],
+    [15000, -4.859, 25.039, 89.748, 79.816],
+    [17000, -9.934, 19.813, 90.668, 80.895],
+    [20000, -15.822, 13.676, 92.106, 81.894],
+    [24000, -22.75, 6.371, 93.651, 82.716],
+    [27000, -29.105, -0.304, 93.838, 83.26],
+    [29314, -32.049, -3.377, 93.502, 82.962],
+    [31000, -34.98, -6.452, 95.392, 84.11],
+    [35000, -45.679, -17.15, 96.104, 85.248],
+    [39000, -45.679, -17.15, 96.205, 84.346],
+    [41500, -45.679, -17.15, 95.676, 83.745],
   ],
   table1502: [
     [0, 0, 0.2, 0.9],

diff --git a/fbw-a32nx/src/systems/fmgc/src/flightplanning/A380AircraftConfig.ts b/fbw-a32nx/src/systems/fmgc/src/flightplanning/A380AircraftConfig.ts
@@ -55,43 +55,24 @@ const engineModelParams: EngineModelParameters = {
   maxThrust: 80_213,
   numberOfEngines: 4,
   fuelBurnFactor: 1.33,
-  /**
-   * Maximum N1 in CLB thrust
-   * @param i row index (tat) in steps of 4°C
-   * @param j col index (pressure altitude, ft)
-   * @returns Corrected N1 (CN1)
-   */
   cn1ClimbLimit: [
-    [0, 2000, 5000, 8000, 12000, 15000, 17000, 20000, 24000, 27000, 31000, 35000, 39000, 41500],
-    [-54, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-50, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-46, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-42, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-38, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-34, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-30, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-26, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-22, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-18, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 102.0, 104.1, 105.5],
-    [-14, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 100.5, 102.5, 103.9],
-    [-10, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 99.1, 100.9, 102.3],
-    [-6, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 99.5, 97.7, 99.3, 100.6],
-    [-2, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 96.2, 98.1, 96.2, 97.7, 99.0],
-    [2, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 94.6, 94.8, 96.6, 94.8, 96.1, 97.3],
-    [6, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 92.1, 93.2, 93.5, 95.1, 93.3, 94.5, 95.7],
-    [10, 82.6, 84.6, 86.8, 88.3, 89.7, 90.7, 90.8, 91.8, 92.1, 93.7, 91.9, 92.9, 94.0],
-    [14, 82.6, 84.6, 86.8, 88.3, 89.7, 89.4, 89.6, 90.4, 90.8, 92.2, 90.5, 91.3, 92.4],
-    [18, 82.6, 84.6, 86.8, 88.3, 88.5, 88.2, 88.3, 89.1, 89.4, 90.7, 89.0, 89.7, 90.7],
-    [22, 82.6, 84.6, 85.6, 87.1, 87.3, 87.0, 87.0, 87.7, 88.1, 89.2, 87.6, 88.1, 89.1],
-    [26, 82.6, 84.6, 84.5, 85.9, 86.0, 85.8, 85.7, 86.3, 86.7, 87.8, 86.1, 86.5, 87.4],
-    [30, 82.6, 83.4, 83.3, 84.7, 84.8, 84.6, 84.4, 84.9, 85.4, 86.3, 84.7, 84.9, 85.8],
-    [34, 81.4, 82.1, 82.1, 83.5, 83.5, 83.3, 83.2, 83.5, 84.0, 84.8, 83.3, 83.3, 84.2],
-    [38, 80.2, 80.8, 80.9, 82.3, 82.3, 82.1, 81.9, 82.2, 82.6, 83.4, 81.8, 81.6, 82.5],
-    [42, 79.0, 79.6, 79.7, 81.1, 81.1, 80.9, 80.6, 80.8, 81.3, 81.9, 80.4, 80.0, 80.9],
-    [46, 77.8, 78.3, 78.5, 79.9, 79.8, 79.7, 79.3, 79.4, 79.9, 80.4, 78.9, 78.4, 79.2],
-    [50, 76.6, 77.0, 77.3, 78.7, 78.6, 78.5, 78.1, 78.0, 78.6, 78.9, 77.5, 76.8, 77.6],
-    [54, 75.4, 75.7, 76.2, 77.5, 77.3, 77.2, 76.8, 76.6, 77.2, 77.5, 76.1, 75.2, 75.9],
-    [58, 74.2, 74.5, 75.0, 76.3, 76.1, 76.0, 75.5, 75.3, 75.9, 76.0, 74.6, 73.6, 74.3],
+    [-2000, 30.8, 56.87, 80.28, 72.0],
+    [2000, 20.99, 48.157, 82.58, 74.159],
+    [5000, 16.139, 43.216, 84.642, 75.737],
+    [8000, 7.342, 38.17, 86.835, 77.338],
+    [10000, 4.051, 34.518, 88.183, 77.999],
+    [10000.1, 4.051, 34.518, 87.453, 77.353],
+    [12000, 0.76, 30.865, 88.303, 78.66],
+    [15000, -4.859, 25.039, 89.748, 79.816],
+    [17000, -9.934, 19.813, 90.668, 80.895],
+    [20000, -15.822, 13.676, 92.106, 81.894],
+    [24000, -22.75, 6.371, 94.588, 83.543],
+    [27000, -29.105, -0.304, 96.203, 85.358],
+    [29314, -32.049, -3.377, 96.82, 85.906],
+    [31000, -34.98, -6.452, 98.568, 86.909],
+    [35000, -45.679, -17.15, 100.977, 89.57],
+    [39000, -45.679, -17.15, 103.085, 90.377],
+    [41500, -45.679, -17.15, 104.509, 91.476],
   ],
   /**
    * Table 1502 - CN2 vs CN1 @ Mach 0, 0.2, 0.9

diff --git a/fbw-a32nx/src/systems/fmgc/src/flightplanning/AircraftConfigTypes.ts b/fbw-a32nx/src/systems/fmgc/src/flightplanning/AircraftConfigTypes.ts
@@ -97,8 +97,13 @@ export interface EngineModelParameters {
 
   /**
    * Maximum corrected N1 in CLB thrust
-   * @param i row index (tat) in steps of 4°C
-   * @param j col index (pressure altitude, ft)
+   * Each row represents a different altitude and the corresponding engine thrust
+   * limits. The columns in each row represent the following parameters:
+   * 1. Altitude (in feet)
+   * 2. Corner Point (CP) - the temperature below which the engine can operate at full thrust without any restrictions.
+   * 3. Limit Point (LP) - the temperature above which the engine thrust starts to be limited.
+   * 4. CN1 Flat - the engine's N1 fan speed limit at the CP temperature.
+   * 5. CN1 Last - the engine's N1 fan speed limit at the LP temperature.
    * @returns Corrected N1 (CN1)
    */
   cn1ClimbLimit: readonly (readonly number[])[];

diff --git a/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/EngineModel.ts b/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/EngineModel.ts
@@ -176,7 +176,61 @@ export class EngineModel {
     return cn1;
   }
 
-  static getClimbThrustCorrectedN1(parameters: EngineModelParameters, altitude: Feet, totalAirTemperature: number) {
-    return EngineModel.tableInterpolation(parameters.cn1ClimbLimit, totalAirTemperature, altitude);
+  static getClimbThrustCorrectedN1(
+    parameters: EngineModelParameters,
+    pressureAltitude: Feet,
+    outsideTemperature: Celsius,
+  ): number {
+    let loAltRow = 0;
+    let hiAltRow = 0;
+
+    // Check for over/under flows. Else, find top row value
+    if (pressureAltitude >= parameters.cn1ClimbLimit[parameters.cn1ClimbLimit.length - 1][0]) {
+      hiAltRow = parameters.cn1ClimbLimit.length - 1;
+      loAltRow = parameters.cn1ClimbLimit.length - 1;
+    } else {
+      hiAltRow = parameters.cn1ClimbLimit.reduce((acc, val, idx) => {
+        return val[0] <= pressureAltitude ? idx + 1 : acc;
+      }, 0);
+      loAltRow = hiAltRow - 1;
+    }
+
+    // Define key table variables and interpolation
+    const cp = Common.interpolate(
+      pressureAltitude,
+      parameters.cn1ClimbLimit[loAltRow][0],
+      parameters.cn1ClimbLimit[hiAltRow][0],
+      parameters.cn1ClimbLimit[loAltRow][1],
+      parameters.cn1ClimbLimit[hiAltRow][1],
+    );
+    const lp = Common.interpolate(
+      pressureAltitude,
+      parameters.cn1ClimbLimit[loAltRow][0],
+      parameters.cn1ClimbLimit[hiAltRow][0],
+      parameters.cn1ClimbLimit[loAltRow][2],
+      parameters.cn1ClimbLimit[hiAltRow][2],
+    );
+    const cn1Flat = Common.interpolate(
+      pressureAltitude,
+      parameters.cn1ClimbLimit[loAltRow][0],
+      parameters.cn1ClimbLimit[hiAltRow][0],
+      parameters.cn1ClimbLimit[loAltRow][3],
+      parameters.cn1ClimbLimit[hiAltRow][3],
+    );
+    const cn1Last = Common.interpolate(
+      pressureAltitude,
+      parameters.cn1ClimbLimit[loAltRow][0],
+      parameters.cn1ClimbLimit[hiAltRow][0],
+      parameters.cn1ClimbLimit[loAltRow][4],
+      parameters.cn1ClimbLimit[hiAltRow][4],
+    );
+
+    if (outsideTemperature <= cp) {
+      return cn1Flat;
+    }
+
+    const m = (cn1Last - cn1Flat) / (lp - cp);
+    const b = cn1Last - m * lp;
+    return m * outsideTemperature + b;
   }
 }
diff --git a/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/climb/ClimbPathBuilder.ts b/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/climb/ClimbPathBuilder.ts
@@ -457,12 +457,7 @@ export class ClimbPathBuilder {
   ): StepResults {
     const { zeroFuelWeight, managedClimbSpeedMach, tropoPause } = this.computationParametersObserver.get();
 
-    const averageCas = (initialSpeed + speedTarget) / 2;
-    const averageClimbSpeedMach = Math.min(
-      managedClimbSpeedMach,
-      this.atmosphericConditions.computeMachFromCas(altitude, averageCas),
-    );
-    const totalAirTemperature = this.atmosphericConditions.totalAirTemperatureFromMach(altitude, averageClimbSpeedMach);
+    const staticAirTemperature = this.atmosphericConditions.predictStaticAirTemperatureAtAltitude(altitude);
 
     return Predictions.speedChangeStep(
       config,
@@ -472,7 +467,7 @@ export class ClimbPathBuilder {
       speedTarget,
       managedClimbSpeedMach,
       managedClimbSpeedMach,
-      EngineModel.getClimbThrustCorrectedN1(config.engineModelParameters, altitude, totalAirTemperature),
+      EngineModel.getClimbThrustCorrectedN1(config.engineModelParameters, altitude, staticAirTemperature),
       zeroFuelWeight,
       fuelWeight,
       0,

diff --git a/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/climb/ClimbStrategy.ts b/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/climb/ClimbStrategy.ts
@@ -132,7 +132,7 @@ export class VerticalSpeedStrategy implements ClimbStrategy, DescentStrategy {
     headwindComponent: WindComponent,
     config: AircraftCtlSurfcConfiguration = DEFAULT_AIRCRAFT_CONTROL_SURFACE_CONFIG,
   ): StepResults {
-    const { zeroFuelWeight, perfFactor, tropoPause, managedClimbSpeedMach } = this.observer.get();
+    const { zeroFuelWeight, perfFactor, tropoPause } = this.observer.get();
 
     const computedMach = Math.min(this.atmosphericConditions.computeMachFromCas(initialAltitude, initialSpeed), mach);
 
@@ -142,8 +142,6 @@ export class VerticalSpeedStrategy implements ClimbStrategy, DescentStrategy {
             this.acConfig.engineModelParameters,
             this.atmosphericConditions,
             initialAltitude,
-            initialSpeed,
-            managedClimbSpeedMach,
           )
         : EngineModel.getIdleCorrectedN1(
             this.acConfig.engineModelParameters,
@@ -261,7 +259,7 @@ export class FlightPathAngleStrategy implements ClimbStrategy, DescentStrategy {
     headwindComponent: WindComponent,
     config: AircraftCtlSurfcConfiguration = DEFAULT_AIRCRAFT_CONTROL_SURFACE_CONFIG,
   ): StepResults {
-    const { zeroFuelWeight, perfFactor, tropoPause, managedClimbSpeedMach } = this.observer.get();
+    const { zeroFuelWeight, perfFactor, tropoPause } = this.observer.get();
 
     const computedMach = Math.min(this.atmosphericConditions.computeMachFromCas(initialAltitude, initialSpeed), mach);
     const predictedN1 =
@@ -270,8 +268,6 @@ export class FlightPathAngleStrategy implements ClimbStrategy, DescentStrategy {
             this.acConfig.engineModelParameters,
             this.atmosphericConditions,
             initialAltitude,
-            initialSpeed,
-            managedClimbSpeedMach,
           )
         : EngineModel.getIdleCorrectedN1(
             this.acConfig.engineModelParameters,
@@ -319,7 +315,7 @@ export class ClimbThrustClimbStrategy implements ClimbStrategy {
     headwindComponent: WindComponent,
     config: AircraftCtlSurfcConfiguration = DEFAULT_AIRCRAFT_CONTROL_SURFACE_CONFIG,
   ): StepResults {
-    const { zeroFuelWeight, tropoPause, perfFactor, managedClimbSpeedMach } = this.observer.get();
+    const { zeroFuelWeight, tropoPause, perfFactor } = this.observer.get();
 
     return Predictions.altitudeStep(
       this.acConfig,
@@ -331,8 +327,6 @@ export class ClimbThrustClimbStrategy implements ClimbStrategy {
         this.acConfig.engineModelParameters,
         this.atmosphericConditions,
         (initialAltitude + finalAltitude) / 2,
-        speed,
-        managedClimbSpeedMach,
       ),
       zeroFuelWeight,
       fuelOnBoard,
@@ -355,21 +349,15 @@ export class ClimbThrustClimbStrategy implements ClimbStrategy {
     headwindComponent: WindComponent,
     config: AircraftCtlSurfcConfiguration = DEFAULT_AIRCRAFT_CONTROL_SURFACE_CONFIG,
   ): StepResults {
-    const { zeroFuelWeight, tropoPause, perfFactor, managedClimbSpeedMach } = this.observer.get();
+    const { zeroFuelWeight, tropoPause, perfFactor } = this.observer.get();
 
     return Predictions.distanceStep(
       this.acConfig,
       initialAltitude,
       distance,
       speed,
       mach,
-      getClimbThrustCorrectedN1Limit(
-        this.acConfig.engineModelParameters,
-        this.atmosphericConditions,
-        initialAltitude,
-        speed,
-        managedClimbSpeedMach,
-      ),
+      getClimbThrustCorrectedN1Limit(this.acConfig.engineModelParameters, this.atmosphericConditions, initialAltitude),
       zeroFuelWeight,
       fuelOnBoard,
       headwindComponent.value,
@@ -391,21 +379,15 @@ export class ClimbThrustClimbStrategy implements ClimbStrategy {
     headwindComponent: WindComponent,
     config: AircraftCtlSurfcConfiguration = DEFAULT_AIRCRAFT_CONTROL_SURFACE_CONFIG,
   ): StepResults {
-    const { zeroFuelWeight, perfFactor, tropoPause, managedClimbSpeedMach } = this.observer.get();
+    const { zeroFuelWeight, perfFactor, tropoPause } = this.observer.get();
 
     return Predictions.altitudeStepWithSpeedChange(
       this.acConfig,
       initialAltitude,
       initialSpeed,
       finalSpeed,
       mach,
-      getClimbThrustCorrectedN1Limit(
-        this.acConfig.engineModelParameters,
-        this.atmosphericConditions,
-        initialAltitude,
-        initialSpeed,
-        managedClimbSpeedMach,
-      ),
+      getClimbThrustCorrectedN1Limit(this.acConfig.engineModelParameters, this.atmosphericConditions, initialAltitude),
       zeroFuelWeight,
       fuelOnBoard,
       headwindComponent.value,
@@ -423,11 +405,8 @@ function getClimbThrustCorrectedN1Limit(
   engineModelParameters: EngineModelParameters,
   atmosphericConditions: AtmosphericConditions,
   altitude: Feet,
-  speed: Knots,
-  maxMach: Mach,
 ) {
-  const climbSpeedMach = Math.min(maxMach, atmosphericConditions.computeMachFromCas(altitude, speed));
-  const estimatedTat = atmosphericConditions.totalAirTemperatureFromMach(altitude, climbSpeedMach);
+  const staticAirTemperature = atmosphericConditions.predictStaticAirTemperatureAtAltitude(altitude);
 
-  return EngineModel.getClimbThrustCorrectedN1(engineModelParameters, altitude, estimatedTat);
+  return EngineModel.getClimbThrustCorrectedN1(engineModelParameters, altitude, staticAirTemperature);
 }
diff --git a/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/cruise/CruisePathBuilder.ts b/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/cruise/CruisePathBuilder.ts
@@ -262,15 +262,7 @@ export class CruisePathBuilder {
     const { zeroFuelWeight, cruiseAltitude, managedCruiseSpeedMach, tropoPause } =
       this.computationParametersObserver.get();
 
-    const averageCas = (speed + finalSpeed) / 2;
-    const averageClimbSpeedMach = Math.min(
-      managedCruiseSpeedMach,
-      this.atmosphericConditions.computeMachFromCas(cruiseAltitude, averageCas),
-    );
-    const totalAirTemperature = this.atmosphericConditions.totalAirTemperatureFromMach(
-      cruiseAltitude,
-      averageClimbSpeedMach,
-    );
+    const staticAirTemperature = this.atmosphericConditions.predictStaticAirTemperatureAtAltitude(cruiseAltitude);
 
     return Predictions.speedChangeStep(
       config,
@@ -280,7 +272,7 @@ export class CruisePathBuilder {
       finalSpeed,
       managedCruiseSpeedMach,
       managedCruiseSpeedMach,
-      EngineModel.getClimbThrustCorrectedN1(config.engineModelParameters, cruiseAltitude, totalAirTemperature),
+      EngineModel.getClimbThrustCorrectedN1(config.engineModelParameters, cruiseAltitude, staticAirTemperature),
       zeroFuelWeight,
       remainingFuelOnBoard,
       headwind.value,

diff --git a/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/takeoff/TakeoffPathBuilder.ts b/fbw-a32nx/src/systems/fmgc/src/guidance/vnav/takeoff/TakeoffPathBuilder.ts
@@ -100,13 +100,12 @@ export class TakeoffPathBuilder {
     const startingAltitude = lastCheckpoint.altitude;
     const midwayAltitude = (startingAltitude + accelerationAltitude) / 2;
 
-    const v2PlusTenMach = this.atmosphericConditions.computeMachFromCas(midwayAltitude, speed);
-    const estimatedTat = this.atmosphericConditions.totalAirTemperatureFromMach(midwayAltitude, v2PlusTenMach);
+    const staticAirTemperature = this.atmosphericConditions.predictStaticAirTemperatureAtAltitude(midwayAltitude);
 
     const predictedN1 = EngineModel.getClimbThrustCorrectedN1(
       config.engineModelParameters,
       midwayAltitude,
-      estimatedTat,
+      staticAirTemperature,
     );
 
     const { fuelBurned, distanceTraveled, timeElapsed } = Predictions.altitudeStep(