diff --git a/flight/modules/StateEstimation/filteraltitude.c b/flight/modules/StateEstimation/filteraltitude.c
index 2b46b35af..aba721ec6 100644
--- a/flight/modules/StateEstimation/filteraltitude.c
+++ b/flight/modules/StateEstimation/filteraltitude.c
@@ -47,7 +47,10 @@
 
 // Private types
 struct data {
-    float state[4]; // state = altitude,velocity,accel_offset,accel
+    float altitudeState; // state = altitude,velocity,accel_offset,accel
+    float velocityState;
+    float accelBiasState;
+    float accelState;
     float pos[3]; // position updates from other filters
     float vel[3]; // position updates from other filters
 
@@ -81,10 +84,10 @@ static int32_t init(stateFilter *self)
 {
     struct data *this = (struct data *)self->localdata;
 
-    this->state[0]  = 0.0f;
-    this->state[1]  = 0.0f;
-    this->state[2]  = 0.0f;
-    this->state[3]  = 0.0f;
+    this->altitudeState  = 0.0f;
+    this->velocityState  = 0.0f;
+    this->accelBiasState = 0.0f;
+    this->accelState     = 0.0f;
     this->pos[0]    = 0.0f;
     this->pos[1]    = 0.0f;
     this->pos[2]    = 0.0f;
@@ -115,13 +118,13 @@ static int32_t filter(stateFilter *self, stateEstimation *state)
             this->pos[0]  = state->pos[0];
             this->pos[1]  = state->pos[1];
             this->pos[2]  = state->pos[2];
-            state->pos[2] = -this->state[0];
+            state->pos[2] = -this->altitudeState;
         }
         if (IS_SET(state->updated, SENSORUPDATES_vel)) {
             this->vel[0]  = state->vel[0];
             this->vel[1]  = state->vel[1];
             this->vel[2]  = state->vel[2];
-            state->vel[2] = -this->state[1];
+            state->vel[2] = -this->velocityState;
         }
         if (IS_SET(state->updated, SENSORUPDATES_accel)) {
             // rotate accels into global coordinate frame
@@ -132,51 +135,51 @@ static int32_t filter(stateFilter *self, stateEstimation *state)
             float current = -(Rbe[0][2] * state->accel[0] + Rbe[1][2] * state->accel[1] + Rbe[2][2] * state->accel[2] + 9.81f);
 
             // low pass filter accelerometers
-            this->state[3] = (1.0f - this->settings.AccelLowPassKp) * this->state[3] + this->settings.AccelLowPassKp * current;
+            this->accelState     = (1.0f - this->settings.AccelLowPassKp) * this->accelState + this->settings.AccelLowPassKp * current;
 
             // correct accel offset (low pass zeroing)
-            this->state[2] = (1.0f - this->settings.AccelDriftKi) * this->state[2] + this->settings.AccelDriftKi * this->state[3];
+            this->accelBiasState = (1.0f - this->settings.AccelDriftKi) * this->accelBiasState + this->settings.AccelDriftKi * this->accelState;
 
             // correct velocity and position state (integration)
             // low pass for average dT, compensate timing jitter from scheduler
             //
             float dT = PIOS_DELTATIME_GetAverageSeconds(&this->dt1config);
-            float speedLast = this->state[1];
+            float speedLast = this->velocityState;
 
-            this->state[1] += 0.5f * (this->accelLast + (this->state[3] - this->state[2])) * dT;
-            this->accelLast = this->state[3] - this->state[2];
+            this->velocityState += 0.5f * (this->accelLast + (this->accelState - this->accelBiasState)) * dT;
+            this->accelLast      = this->accelState - this->accelBiasState;
 
-            this->state[0] += 0.5f * (speedLast + this->state[1]) * dT;
+            this->altitudeState += 0.5f * (speedLast + this->velocityState) * dT;
 
 
             state->pos[0]   = this->pos[0];
             state->pos[1]   = this->pos[1];
-            state->pos[2]   = -this->state[0];
+            state->pos[2]   = -this->altitudeState;
             state->updated |= SENSORUPDATES_pos;
 
             state->vel[0]   = this->vel[0];
             state->vel[1]   = this->vel[1];
-            state->vel[2]   = -this->state[1];
+            state->vel[2]   = -this->velocityState;
             state->updated |= SENSORUPDATES_vel;
         }
         if (IS_SET(state->updated, SENSORUPDATES_baro)) {
             // correct the altitude state (simple low pass)
-            this->state[0] = (1.0f - this->settings.BaroKp) * this->state[0] + this->settings.BaroKp * state->baro[0];
+            this->altitudeState = (1.0f - this->settings.BaroKp) * this->altitudeState + this->settings.BaroKp * state->baro[0];
 
             // correct the velocity state (low pass differentiation)
             // low pass for average dT, compensate timing jitter from scheduler
             float dT = PIOS_DELTATIME_GetAverageSeconds(&this->dt2config);
-            this->state[1]  = (1.0f - (this->settings.BaroKp * this->settings.BaroKp)) * this->state[1] + (this->settings.BaroKp * this->settings.BaroKp) * (state->baro[0] - this->baroLast) / dT;
+            this->velocityState = (1.0f - (this->settings.BaroKp * this->settings.BaroKp)) * this->velocityState + (this->settings.BaroKp * this->settings.BaroKp) * (state->baro[0] - this->baroLast) / dT;
             this->baroLast  = state->baro[0];
 
             state->pos[0]   = this->pos[0];
             state->pos[1]   = this->pos[1];
-            state->pos[2]   = -this->state[0];
+            state->pos[2]   = -this->altitudeState;
             state->updated |= SENSORUPDATES_pos;
 
             state->vel[0]   = this->vel[0];
             state->vel[1]   = this->vel[1];
-            state->vel[2]   = -this->state[1];
+            state->vel[2]   = -this->velocityState;
             state->updated |= SENSORUPDATES_vel;
         }
     }