Height Measurement

[ardisd]

Have a eagle tree pro system on my Boomerang have no problem measuring speed appears to be accurate but the altitude is very inaccurate has anyone any suggestions how i can fix the problem.

Static tube is at least 2 inches away from the fuselarge

[billpa]

Hi Ardisd,

Sorry to hear about your problem.

Can you give us more information about the inaccurate altitude problem? Note that if it appears that your plane (or boomerang?) is higher or lower than the equipment is reporting, it may be that it is actually as high as reported. It's sometimes hard to judge.

Regards,

Bill, for Eagle Tree

[ardisd]

I have done quite a number of tests over the last few months flying the model in what appears to be level flight and the height according to the dashboard differs by 10's of metres at random while the speed is constant, so good in fact that I kmow the boomerang will stall at 29mph enclosed two pictures of the pitot tube in stallation.

Note the pitot is a tube within a tube the centre hole is for measuring speed and the outer tube has 4 1mm holes drilled 90 degrees apart

[billpa]

Hi ardisd,

I think I see the problem. Your static port is not going to work correctly, I'm afraid, if I am interpreting the photo correctly. The static holes appear to be embedded in the cowling, which will not work - pressure will build up in the mouth of the cowling. The static holes need to be in undisturbed air, away from the leading edge of the wing. I would recommend using your tube for pitot readings only, and perhaps adding another tube on the other wing, which is static-only.

Please see the link below, which describes how to create a static-only tube from a standard piece of brass tubing.

http://www.eagletreesystems.com/Support/Manuals/seagull%20pro%20flight%20system%20instruction%20ma nual.pdf

Regards,

Bill, for Eagle Tree

[ardisd]

I have put some notes on the pictures hope this makes it clear the reason for making it detachable is the last one got bent and they are quite hard to make

[billpa]

Hi ardisd,

Ah, thanks for the clarification. Ignore everything I said above from the "Hi" to the "Regards". :-) That's a nice pitot/static tube!

Some things I can think of that might cause the problem are:

1) could the static tube be leaking, or getting some sort of "blowback" turbulence from the mounting pod? One way to verify this is to fly with the pitot port of the airspeed sensor connected to the static port, and the static port of the airspeed sensor connected to a different static tube, which is mounted on the side of the fuselage, completely flush with the surface. If you get non-zero airspeed readings, something is amiss with one or both of the pickups.

Another way to check for leaks would be to apply some pressure to the pitot port, and verify that the altitude doesn't change. If it does not, then apply pressure to the static port, and make sure that there is not bleed-off of air.

2) Less likely, something could be wrong with the altimeter Do you see the sudden 10's of meter drift with the recorder just sitting still?

Hope this helps!

Regards,

Bill, for Eagle Tree