static pressure port

[elossam]

Hi friends
I can´t place my static pressure port into the fuselage because it has airflow inputs to refresh the electronics and there it could get irregular readings.
At the same time I can´t use a double port on each side of the fuselage with a "Y" tube due to operational reassons that makes quite difficult the tube conection to the AP on every flight.

Here the question. Should it be possible to use a double static port with a "Y" placing the end of the tubes, one above the wing and the other below it so it can balance the presures and give a right reading?

I´ve tested all other options including a double pitot tube (dinamic inside and static outside) but I´m wondering what about this other kind of placement. Could it be an option?

Regards

[rbeall]

Honestly in practice...having airflow through the cockpit won't significantly affect your altitude reading. However if you are talking about a significant amount of mass flow then the best option is to just make a static port and stick it as far away from the aircraft as possible. The basic construction of a static port is just a tube with end plugged and 4 holes drilled along the edge. You want to put this as far away from the leading edge as possible because any interference will cause a bias. That being said it really isn't that critical unless you are looking for accuracy. Most full scale aircraft have static ports just below the cockpit window. This obviously introduces interference because the flow is having to wrap around the front of the fuselage. However in the testing phase of the aircraft they put a pitot probe out the very front of the aircraft and capture the bias. Then from that point forward they just subtract the bias out and walla. But like I said if you stick a static probe a couple inches in front of the leading edge you should be more than good.

The two on a Y connection is a terrible idea. The pressure won't "equalize". You will in fact be averaging the two, however if you say move one forward or back (say the top) it will change and therefore change the average. So is the first placement correct or the second? Or the infinite positions in between?

Hope this helps

[elossam]

I know, I was told today why the "Y" on both sides of the wing can´t work. The diference of pressures is not constant, (may be not lineal as well) to airspeed variations so I can get a good reading for a single speed but a big inaccuracy at other different speeds.
The actual pitot in use was made with two concentric tubes having the inner one for dinamic readings and the outer one with four perpendicular holes for the static readings. I works fine but a) it´s difficult to build and b) It´s more difficult to make it removable in a fast way.

We tried first to read form inside the fuselage, later we use two reading lines with an "Y" placing them on both sides of the fuselage and getting with that solution a better reading than previously with the single/inner port.

The actual pitot with both ports included help us not to need a manual connection of the tubes to the AP every time we want to fly (the AP unit is placed in the wing) but we need to make it removable as well for transport and easy changes in case of tube damage. Looks like the best solution is to use two separate single tubes. Accuracy is very important, specially at low speeds due to the narrow marging between a good observation speed and the stall speed of the model.

thanks for your interest Rbeall.
Elossam

[rbeall]

Yeah, that's what we have always done is use two tubes. They are pretty easy to make. Because they are so easy we just made tubes for each wing which facilitated switching ap's

which ap are you using?

[elossam]

Ap04r