diff --git a/libraries/AC_PID/AC_PID.cpp b/libraries/AC_PID/AC_PID.cpp
index 9f3c83d12c..1f1a8cf544 100644
--- a/libraries/AC_PID/AC_PID.cpp
+++ b/libraries/AC_PID/AC_PID.cpp
@@ -55,19 +55,19 @@ int32_t AC_PID::get_leaky_i(int32_t error, float dt, float leak_rate)
 int32_t AC_PID::get_d(int32_t input, float dt)
 {
     if ((_kd != 0) && (dt != 0)) {
-        _derivative = (input - _last_input) / dt;
+        float derivative = (input - _last_input) / dt;
 
         // discrete low pass filter, cuts out the
         // high frequency noise that can drive the controller crazy
-        _derivative = _last_derivative +
-                      (dt / ( _filter + dt)) * (_derivative - _last_derivative);
+        derivative = _last_derivative +
+                      (dt / ( _filter + dt)) * (derivative - _last_derivative);
 
         // update state
         _last_input             = input;
-        _last_derivative    = _derivative;
+        _last_derivative    = derivative;
 
         // add in derivative component
-        return _kd * _derivative;
+        return _kd * derivative;
     }
     return 0;
 }
@@ -83,47 +83,6 @@ int32_t AC_PID::get_pid(int32_t error, float dt)
     return get_p(error) + get_i(error, dt) + get_d(error, dt);
 }
 
-
-
-/*
- *  int32_t AC_PID::get_pid(int32_t error, float dt)
- *  {
- *       // Compute proportional component
- *       _output = error * _kp;
- *
- *       // Compute derivative component if time has elapsed
- *       if ((fabs(_kd) > 0) && (dt > 0)) {
- *               _derivative = (error - _last_error) / dt;
- *
- *               // discrete low pass filter, cuts out the
- *               // high frequency noise that can drive the controller crazy
- *               _derivative = _last_derivative +
- *                       (dt / ( _filter + dt)) * (_derivative - _last_derivative);
- *
- *               // update state
- *               _last_error        = error;
- *               _last_derivative    = _derivative;
- *
- *               // add in derivative component
- *               _output    += _kd * _derivative;
- *       }
- *
- *       // Compute integral component if time has elapsed
- *       if ((fabs(_ki) > 0) && (dt > 0)) {
- *               _integrator        += (error * _ki) * dt;
- *               if (_integrator < -_imax) {
- *                       _integrator = -_imax;
- *               } else if (_integrator > _imax) {
- *                       _integrator = _imax;
- *               }
- *               _output    += _integrator;
- *       }
- *
- *       return _output;
- *  }
- */
-
-
 void
 AC_PID::reset_I()
 {
diff --git a/libraries/AC_PID/AC_PID.h b/libraries/AC_PID/AC_PID.h
index e01b2fae9e..4261256ad3 100644
--- a/libraries/AC_PID/AC_PID.h
+++ b/libraries/AC_PID/AC_PID.h
@@ -124,8 +124,6 @@ private:
     float           _integrator;                                ///< integrator value
     int32_t         _last_input;                                ///< last input for derivative
     float           _last_derivative;                           ///< last derivative for low-pass filter
-    float           _output;
-    float           _derivative;
 
     /// Low pass filter cut frequency for derivative calculation.
     ///