diff --git a/libraries/AC_PID/AC_PID.cpp b/libraries/AC_PID/AC_PID.cpp
index 557b6b5bfb..358535592f 100644
--- a/libraries/AC_PID/AC_PID.cpp
+++ b/libraries/AC_PID/AC_PID.cpp
@@ -336,7 +336,7 @@ float AC_PID::get_d() const
     return _kd * _derivative;
 }
 
-float AC_PID::get_ff()
+float AC_PID::get_ff() const
 {
     return  _pid_info.FF + _pid_info.DFF;
 }
diff --git a/libraries/AC_PID/AC_PID.h b/libraries/AC_PID/AC_PID.h
index 0aa7e35e2c..8f9b7704c9 100644
--- a/libraries/AC_PID/AC_PID.h
+++ b/libraries/AC_PID/AC_PID.h
@@ -72,17 +72,11 @@ public:
     // todo: remove function when it is no longer used.
     float update_error(float error, float dt, bool limit = false);
 
-    //  update_i - update the integral
-    //  if the limit flag is set the integral is only allowed to shrink
-    void update_i(float dt, bool limit);
-
     // get_pid - get results from pid controller
-    float get_pid() const;
-    float get_pi() const;
     float get_p() const;
     float get_i() const;
     float get_d() const;
-    float get_ff();
+    float get_ff() const;
 
     // reset_I - reset the integrator
     void reset_I();
@@ -113,9 +107,11 @@ public:
     AP_Float &filt_E_hz() { return _filt_E_hz; }
     AP_Float &filt_D_hz() { return _filt_D_hz; }
     AP_Float &slew_limit() { return _slew_rate_max; }
+    AP_Float &kDff() { return _kdff; }
 
     float imax() const { return _kimax.get(); }
     float pdmax() const { return _kpdmax.get(); }
+
     float get_filt_T_alpha(float dt) const;
     float get_filt_E_alpha(float dt) const;
     float get_filt_D_alpha(float dt) const;
@@ -131,6 +127,7 @@ public:
     void filt_E_hz(const float v);
     void filt_D_hz(const float v);
     void slew_limit(const float v);
+    void kDff(const float v) { _kdff.set(v); }
 
     // set the desired and actual rates (for logging purposes)
     void set_target_rate(float target) { _pid_info.target = target; }
@@ -150,20 +147,17 @@ public:
 
     const AP_PIDInfo& get_pid_info(void) const { return _pid_info; }
 
-    AP_Float &kDff() { return _kdff; }
-    void kDff(const float v) { _kdff.set(v); }
     void set_notch_sample_rate(float);
+
     // parameter var table
     static const struct AP_Param::GroupInfo var_info[];
 
-    // the time constant tau is not currently configurable, but is set
-    // as an AP_Float to make it easy to make it configurable for a
-    // single user of AC_PID by adding the parameter in the param
-    // table of the parent class. It is made public for this reason
-    AP_Float _slew_rate_tau;
-    
 protected:
 
+    //  update_i - update the integral
+    //  if the limit flag is set the integral is only allowed to shrink
+    void update_i(float dt, bool limit);
+
     // parameters
     AP_Float _kp;
     AP_Float _ki;
@@ -180,6 +174,13 @@ protected:
     AP_Int8 _notch_T_filter;
     AP_Int8 _notch_E_filter;
 #endif
+
+    // the time constant tau is not currently configurable, but is set
+    // as an AP_Float to make it easy to make it configurable for a
+    // single user of AC_PID by adding the parameter in the param
+    // table of the parent class. It is made public for this reason
+    AP_Float _slew_rate_tau;
+
     SlewLimiter _slew_limiter{_slew_rate_max, _slew_rate_tau};
 
     // flags