### Alt drop loiter_turns

While flying several circles with different radius (in Auto_mode with the command loiter_turns) my vehicle starts losing altitude when it has a speed of 10 m/s. The first idea was that this was caused by the aerodynamic effect that causes the barometer altitude to suddenly climb, but like you can conclude from the logs this isn't the problem. The barometer altitude gives the correct altitude.. Does anyone know what the problem is? I attached the logs.

Thanks,

Stijn.

17.BIN

#### Replies

• I just programmed your mission and did 7 turns from 5m to 35m and did not lose any altitude on each turn nor through the entre mission. Also there was a strong wind about 15mph which also did not effect the mission.

• What was the speed and turn rate you were flying with? We are flying against the speed limit, if you set an unrealistic high turn rate (for example 20 deg/s), wp_speed at 2000 cm/s, wp acceleration at 500cm/s² the copter will try to go as fast as possible in every circle. This is what we did, and then it started to drop in altitude.

• From the logs it looks like the copter can not turn at the rate you set.  We can see from the logs that as it turns it starts to loose altitude.  When it get to the end of the circle in this case clockwise it sees that it is too low to reach the next way point and slows down and climbs to reach it.  It then repeats this.  The last loop has the farthest to go and looses the most altitude before you switch to loiter to prevent it from hitting the ground.

Also since the copter is rotating as it turns it has to apply yaw which could also be causing it to fall.

• That's possible, but I think if the copter can't reach the rate you set as parameter, the arducopter code uses the rate that is calculated from the actual velocity of the vehicle and the radius of the circle.

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