Should I use the AS (Pitot tube)?

ArduPlane Plane 3.3
1

Should I use the AS (Pitot tube) ?
Good afternoon!
Prompt me please, I have to use necessarily the AS, or the autopilot can work without it?
I’m afraid the plane can fall with a fair wind.

thanks for answers.

2

You can fly without it, just set enough cruise throttle, and tailwind after turn won’t be a problem

3

AutoPilot uses a minimum speed of the AS in its algorithms flight?

4

It will fly better with AS, especially if the wind is a bit stronger as the aircraft will then use airspeed to fly rather than groundspeed. Without AS you will just have to fly a bit faster as mentioned.

5

I have no airspeed probe on most of my airplanes. They fly perfectly well with no probe.

I have two problems with the current hardware/firmware:

  1. Both the analog and digital probes are not very well temperature compensated. Earlier this year I was collecting data and running aerodynamic performance calculations on my test aircraft. I found that temperature drift made computing aircraft lift and drag difficult with lots of data scatter. Turning off the airspeed probe and doing a couple of loiter circles to compute the winds resulted in much cleaner data. The problem is better pitot-static transducers like full-scale aircraft have are very expensive.
  2. The other problem is failure management. There is a failure mode that will result in a full power nosedive into the ground. If the pitot probe gets plugged (bug strike) the airspeed will read very low and the firmware will dive and increase power because it thinks it is stalling. Maybe dual airspeed systems with the proper failure management logic would solve that problem.

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6

thanks for answers

7

You can set a maximum airspeed and groudspeed difference to avoid issues if the airspeed sensor gets clogged. It is designed to notice if there is a large difference between the two then ignore the airspeed sensor if it is true.

Also, you can set minimum ground speed which can help as well.

Flight performance with the airspeed sensor is much better and recommended by the Devs.

8

You can fly without an AS sensor and you will be fine.

Yes a blocked Pitot tube is a problem. People should be calibrating their airspeed sensor before flight and checking their readings - this will indicate if you have an issue. Pre-arming checks will also help with this. I’ve never heard of an AS sensor getting blocked during flight - its normally on the ground where it gets clocked with grass or dirt. SITL supports testing of pitot tube hardware failures. SIM_ARSP_FAIL (float) sets the m/s value you want the airspeed to report. Use zero (0) to use the normally generated airspeed, otherwise it is set statically (plus the noise) at the value you set which will simulate a clogged tube.

There has been some discussion on this here:
github.com/diydrones/ardupilot/ … -118551971

Thanks, Grant.