diff --git a/libraries/AC_PID/AC_PID.cpp b/libraries/AC_PID/AC_PID.cpp
index a5cf39d4d4..8eae1ea4d0 100644
--- a/libraries/AC_PID/AC_PID.cpp
+++ b/libraries/AC_PID/AC_PID.cpp
@@ -62,8 +62,7 @@ float AC_PID::get_d(float input, float dt)
 
         // discrete low pass filter, cuts out the
         // high frequency noise that can drive the controller crazy
-        derivative = _last_derivative +
-                      (dt / ( AC_PID_D_TERM_FILTER + dt)) * (derivative - _last_derivative);
+        derivative = _last_derivative + _d_lpf_alpha * (derivative - _last_derivative);
 
         // update state
         _last_input             = input;
@@ -109,3 +108,10 @@ void AC_PID::save_gains()
     _kd.save();
     _imax.save();
 }
+
+void AC_PID::set_d_lpf_alpha(int16_t cutoff_frequency, float time_step)
+{    
+    // calculate alpha
+    float rc = 1/(2*PI*cutoff_frequency);
+    _d_lpf_alpha = time_step / (time_step + rc);
+}
diff --git a/libraries/AC_PID/AC_PID.h b/libraries/AC_PID/AC_PID.h
index db92a60017..23b11bc7de 100644
--- a/libraries/AC_PID/AC_PID.h
+++ b/libraries/AC_PID/AC_PID.h
@@ -12,12 +12,12 @@
 #include <math.h>               // for fabs()
 
 // Examples for _filter:
-// f_cut = 10 Hz -> _filter = 15.9155e-3
-// f_cut = 15 Hz -> _filter = 10.6103e-3
-// f_cut = 20 Hz -> _filter =  7.9577e-3
-// f_cut = 25 Hz -> _filter =  6.3662e-3
-// f_cut = 30 Hz -> _filter =  5.3052e-3
-#define AC_PID_D_TERM_FILTER 0.00795770f    // 20hz filter on D term
+// f_cut = 10 Hz -> _alpha = 0.385869
+// f_cut = 15 Hz -> _alpha = 0.485194
+// f_cut = 20 Hz -> _alpha = 0.556864
+// f_cut = 25 Hz -> _alpha = 0.611015
+// f_cut = 30 Hz -> _alpha = 0.653373
+#define AC_PID_D_TERM_FILTER 0.556864f    // Default 100Hz Filter Rate with 20Hz Cutoff Frequency
 
 /// @class	AC_PID
 /// @brief	Object managing one PID control
@@ -38,7 +38,8 @@ public:
         const float &   initial_p = 0.0,
         const float &   initial_i = 0.0,
         const float &   initial_d = 0.0,
-        const int16_t & initial_imax = 0.0)
+        const int16_t & initial_imax = 0.0):
+        _d_lpf_alpha(AC_PID_D_TERM_FILTER)
     {
 		AP_Param::setup_object_defaults(this, var_info);
 
@@ -81,6 +82,9 @@ public:
     /// Save gain properties
     ///
     void        save_gains();
+    
+    /// Sets filter Alpha for D-term LPF
+    void        set_d_lpf_alpha(int16_t cutoff_frequency, float time_step);
 
     /// @name	parameter accessors
     //@{
@@ -116,6 +120,7 @@ protected:
     float           _integrator;                                ///< integrator value
     float           _last_input;                                ///< last input for derivative
     float           _last_derivative;                           ///< last derivative for low-pass filter
+    float           _d_lpf_alpha;                               ///< alpha used in D-term LPF
 };
 
 #endif // __AC_PID_H__