From 1e5d48d1d97cafef7315e3e9688c807142b945b0 Mon Sep 17 00:00:00 2001
From: david <david>
Date: Sun, 2 Mar 2003 01:43:39 +0000
Subject: [PATCH] Add spdFromMach() and spdFromVCAS().

---
 src/FDM/YASim/Atmosphere.cpp | 19 +++++++++++++++++++
 src/FDM/YASim/Atmosphere.hpp |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/src/FDM/YASim/Atmosphere.cpp b/src/FDM/YASim/Atmosphere.cpp
index 83c6b9748..92d2fbe56 100644
--- a/src/FDM/YASim/Atmosphere.cpp
+++ b/src/FDM/YASim/Atmosphere.cpp
@@ -102,6 +102,25 @@ float Atmosphere::calcMach(float spd, float temp)
     return spd / Math::sqrt(GAMMA * R * temp);
 }
 
+float Atmosphere::spdFromMach(float mach, float temp)
+{
+    return mach * Math::sqrt(GAMMA * R * temp);
+}
+
+float Atmosphere::spdFromVCAS(float vcas, float pressure, float temp)
+{
+                                // FIXME: does not account for supersonic
+    float p0 = getStdPressure(0);
+    float rho0 = getStdDensity(0);
+
+    float tmp = (vcas*vcas)/(7*p0/rho0) + 1;
+    float cp = ((Math::pow(tmp,(7/2.))-1)/(pressure/p0)) + 1;
+
+    float m2 = (Math::pow(cp,(1/3.5))-1)/0.2;
+    float vtas= spdFromMach(Math::sqrt(m2), temp);
+    return vtas;
+}
+
 void Atmosphere::calcStaticAir(float p0, float t0, float d0, float v,
                                float* pOut, float* tOut, float* dOut)
 {
diff --git a/src/FDM/YASim/Atmosphere.hpp b/src/FDM/YASim/Atmosphere.hpp
index 559707a34..b0cfd3d86 100644
--- a/src/FDM/YASim/Atmosphere.hpp
+++ b/src/FDM/YASim/Atmosphere.hpp
@@ -13,6 +13,9 @@ public:
     static float calcVEAS(float spd, float pressure, float temp, float density);
     static float calcMach(float spd, float temp);
     static float calcStdDensity(float pressure, float temp);
+
+    static float spdFromMach(float mach, float temp);
+    static float spdFromVCAS(float vcas, float pressure, float temp);
     
     // Given ambient ("0") pressure/density/temperature values,
     // calculate the properties of static air (air accelerated to the
-- 
2.39.5