feat(athr/fadec): improved reverse thrust limit based on TOGA limit

.github/CHANGELOG.md

@@ -84,6 +84,7 @@
 1. [FWC] Implement non-cancellable master warning for overspeed and gear not down - @tracernz (Mike)
 1. [EFB] Checklist restructure to add more capabilities and use json configs - @frankkopp (Frank Kopp)
 1. [FLIGHTMODEL] Landing lights or RAT extended now have drag - @Crocket63 (crocket)
+1. [ATHR/FADEC] Improved reverse thrust limit - @aguther (Andreas Guther)
 
 ## 0.11.0
 

fbw-a32nx/docs/Configuration/ModelConfiguration.ini

@@ -33,8 +33,8 @@
 
 [autothrust]
 ; !! WARNING CHANGE AT YOUR OWN RISK !!
-; sets the target N1 for full reverse
-;thrust_limit_reverse = -45.0
+; sets the target N1 in percentage of TOGA limit for full reverse
+;thrust_limit_reverse_percentage_toga = 0.8
 
 ; !! WARNING CHANGE AT YOUR OWN RISK !!
 ; if enabled, thrust limits IDLE, CLB and TOGA are taken from local variables

fbw-a32nx/src/base/flybywire-aircraft-a320-neo/SimObjects/AirPlanes/FlyByWire_A320_NEO/engines.cfg

@@ -4,7 +4,7 @@ minor = 0
 
 [GENERALENGINEDATA]
 engine_type = 1 ; 0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
-min_throttle_limit = -0.2 ; Minimum percent throttle.  Generally negative for turbine reverser
+min_throttle_limit = -1.0 ; Minimum percent throttle.  Generally negative for turbine reverser
 master_ignition_switch = 0
 starter_type = 2 ; 0=Electric, 1=Manual, 2=Bleed Air
 max_contrail_temperature = -39.724

fbw-a32nx/src/systems/instruments/src/EWD/N1Limit.tsx

@@ -52,7 +52,7 @@ export class N1Limit extends DisplayComponent<N1LimitProps> {
         });
 
         sub.on('autoThrustLimit').whenChanged().handle((l) => {
-            this.autoThrustLimit = l;
+            this.autoThrustLimit = Math.abs(l);
         });
 
         sub.on('thrustLimitType').whenChanged().handle((l) => {

fbw-a32nx/src/wasm/fbw_a320/src/FlyByWireInterface.cpp

@@ -223,13 +223,11 @@ void FlyByWireInterface::loadConfiguration() {
 
   // --------------------------------------------------------------------------
   // load values - autothrust
-  autothrustThrustLimitReverse = INITypeConversion::getDouble(iniStructure, "AUTOTHRUST", "THRUST_LIMIT_REVERSE", -45.0);
-
-  // initialize local variable for reverse
-  idAutothrustThrustLimitREV->set(autothrustThrustLimitReverse);
+  autothrustThrustLimitReversePercentageToga =
+      INITypeConversion::getDouble(iniStructure, "AUTOTHRUST", "THRUST_LIMIT_REVERSE_PERCENTAGE_TOGA", 0.813);
 
   // print configuration into console
-  std::cout << "WASM: AUTOTHRUST : THRUST_LIMIT_REVERSE    = " << autothrustThrustLimitReverse << std::endl;
+  std::cout << "WASM: AUTOTHRUST : THRUST_LIMIT_REVERSE_PERCENTAGE_TOGA    = " << autothrustThrustLimitReversePercentageToga << std::endl;
 
   // --------------------------------------------------------------------------
   // load values - flight controls
@@ -2407,6 +2405,9 @@ bool FlyByWireInterface::updateAutothrust(double sampleTime) {
   idThrottlePosition3d_1->set(idThrottlePositionLookupTable3d.get(thrustLeverAngle_1->get()));
   idThrottlePosition3d_2->set(idThrottlePositionLookupTable3d.get(thrustLeverAngle_2->get()));
 
+  // update reverser thrust limit
+  idAutothrustThrustLimitREV->set(idAutothrustThrustLimitTOGA->get() * autothrustThrustLimitReversePercentageToga);
+
   // set client data if needed
   if (!autoThrustEnabled || !autopilotStateMachineEnabled || !flyByWireEnabled) {
     ClientDataLocalVariablesAutothrust ClientDataLocalVariablesAutothrust = {

fbw-a32nx/src/wasm/fbw_a320/src/FlyByWireInterface.h

@@ -76,7 +76,7 @@ class FlyByWireInterface {
   bool wasPaused = false;
   bool wasInSlew = false;
 
-  double autothrustThrustLimitReverse = -45;
+  double autothrustThrustLimitReversePercentageToga = 0.0;
 
   bool flightDirectorConnectLatch_1 = false;
   bool flightDirectorConnectLatch_2 = false;

fbw-a32nx/src/wasm/fbw_a320/src/model/Autothrust_data.cpp

@@ -180,13 +180,13 @@ Autothrust::Parameters_Autothrust_T Autothrust::Autothrust_P{
 
   0.0,
 
-  -20.0,
+  -100.0,
 
   -2.0,
 
   0.0,
 
-  -20.0,
+  -100.0,
 
 
   { 1.8, 1.8, 1.0, 1.2, 1.2 },

fbw-common/src/wasm/systems/systems/src/engine/reverser_thrust.rs

@@ -6,7 +6,7 @@ use uom::si::{
     mass::kilogram,
     ratio::{percent, ratio},
     torque::newton_meter,
-    velocity::{foot_per_second, meter_per_second},
+    velocity::{foot_per_second, knot, meter_per_second},
 };
 
 use crate::{
@@ -29,37 +29,53 @@ impl ReverserThrust {
             current_thrust: Force::default(),
         }
     }
-    fn update(&mut self, engine: &impl Engine, reverser_position: &impl ReverserPosition) {
-        self.current_thrust = if reverser_position.reverser_position().get::<ratio>()
-            > Self::MIN_REVERSER_POS
-        {
-            let current_thrust_force =
-                Force::new::<newton>(engine.net_thrust().get::<kilogram>() * 9.80665);
-
-            // Total net thrust with reverser will need to cancel out forward thrust generated by engine + added desired reverse thrust
-            (current_thrust_force
-                + current_thrust_force * Self::reverse_thrust_ratio_from_n1(engine.corrected_n1()))
-                * reverser_position.reverser_position()
-        } else {
-            Force::default()
-        };
+    fn update(
+        &mut self,
+        engine: &impl Engine,
+        reverser_position: &impl ReverserPosition,
+        longitudinal_velocity: Velocity,
+    ) {
+        self.current_thrust =
+            if reverser_position.reverser_position().get::<ratio>() > Self::MIN_REVERSER_POS {
+                let current_thrust_force =
+                    Force::new::<newton>(engine.net_thrust().get::<kilogram>() * 9.80665);
+
+                // Total net thrust with reverser will need to cancel out forward thrust generated by engine + added desired reverse thrust
+                (current_thrust_force
+                    + current_thrust_force
+                        * Self::reverse_thrust_ratio_from_n1(engine.corrected_n1())
+                        * Self::reverse_thrust_ratio_longitudinal_velocity(longitudinal_velocity))
+                    * reverser_position.reverser_position()
+            } else {
+                Force::default()
+            };
     }
 
     fn current_thrust(&self) -> Force {
         self.current_thrust
     }
 
     fn reverse_thrust_ratio_from_n1(engine_n1: Ratio) -> Ratio {
-        let n1_breakpoints = [0., 15., 20., 50., 55.];
+        let n1_breakpoints = [0., 15., 20., 50., 55., 100.];
 
-        let reverse_thrust_ratio = [0., 0., 0.15, 0.4, 0.42];
+        let reverse_thrust_ratio = [0., 0., 0.04, 0.31, 0.31, 0.31];
 
         Ratio::new::<ratio>(interpolation(
             &n1_breakpoints,
             &reverse_thrust_ratio,
             engine_n1.get::<percent>(),
         ))
     }
+
+    fn reverse_thrust_ratio_longitudinal_velocity(longitudinal_velocity: Velocity) -> Ratio {
+        let longitudinal_velocity_knots = longitudinal_velocity.get::<knot>();
+
+        if longitudinal_velocity_knots >= 0. {
+            Ratio::new::<ratio>(1.0)
+        } else {
+            Ratio::new::<ratio>((0.1151 * longitudinal_velocity_knots).exp())
+        }
+    }
 }
 
 pub struct ReverserForce {
@@ -98,7 +114,11 @@ impl ReverserForce {
         reverser_position: &[impl ReverserPosition],
     ) {
         for (engine_index, reverser) in self.reversers.iter_mut().enumerate() {
-            reverser.update(engine[engine_index], &reverser_position[engine_index]);
+            reverser.update(
+                engine[engine_index],
+                &reverser_position[engine_index],
+                Velocity::new::<meter_per_second>(context.local_velocity().to_ms_vector()[2]),
+            );
         }
 
         let total_force = self.reversers[0].current_thrust() + self.reversers[1].current_thrust();