Proper Way to Insert Multi-Probe

On Thursday, February 15, 2018 at 2:30:07 PM UTC-6, Steve Thompson wrote:
There are clear instructions by ESA at
https://tinyurl.com/ESAFAQEnglish
which suggest cleanliness, light lubrication, and give
orientation advice also. Just saying.

Ah Ha! Oriented UP!

Let the arguing - and bogus explanations - begin!

(FWIW I've always been in the UP camp...position relative to the horizontal, angle of the probe when changing AOA, less chance of hitting it when installing tail dolly...)

Kirk
66

Ah Ha! Oriented UP!


Of course it goes up - it's more virile.

On Thursday, February 15, 2018 at 12:46:27 PM UTC-8, kirk.stant wrote:
On Thursday, February 15, 2018 at 2:30:07 PM UTC-6, Steve Thompson wrote:
There are clear instructions by ESA at
https://tinyurl.com/ESAFAQEnglish
which suggest cleanliness, light lubrication, and give
orientation advice also. Just saying.

Ah Ha! Oriented UP!

Let the arguing - and bogus explanations - begin!

(FWIW I've always been in the UP camp...position relative to the horizontal, angle of the probe when changing AOA, less chance of hitting it when installing tail dolly...)

Kirk
66

I used to always put my probe up (whenever I had the opportunity), but then someone pointed out to me that when the probe is installed down and the glider is in flying position, the probe is quite close to vertical. Seemed that was likely the correct position.

The typical designed probe is designed to point up which gives the intended angle to the airflow and also keeps the tip high and as close to the line of the tailplane. See Rudy Brozel's articles.

Another quite common factor is to avoid the down pointing probe interfering with a fin pitot which is often close below. Dick Johnson tested this and showed that there was significant interference.

On Saturday, 17 February 2018 01:14:48 UTC+2, wrote:

I used to always put my probe up (whenever I had the opportunity), but then someone pointed out to me that when the probe is installed down and the glider is in flying position, the probe is quite close to vertical. Seemed that was likely the correct position.

I'm confused. The adapter for the probe is pointing straight to airflow at flying angle-of-attack. The probe end sticking up or down would have same angle relative to airflow?

Most compensation probes are designed to function with an angle of 70°, not 90° (but some do), between the prong and the airflow. Whatever you do, that angle will change whenever you increase or reduce your airspeed, so the system must have some built-in flexibility. How much flexibility and in what direction (up or down) will probably depend on the design of the probe. So follow the instructions of the manufacturer, would be my advice. ESA Systems says prong up, so that's it for me.

There are two-pronged probes that should be placed with the prongs horizontal.
https://www.esa-systems.com/en/produ...e-dnst-840-mm/
https://www.esa-systems.com/en/produ...robe-dnstatek/
According to a German study, this type gives the best compensation results.

On Thursday, February 15, 2018 at 4:54:24 PM UTC-5, Dave Springford wrote:

Ah Ha! Oriented UP!


Of course it goes up - it's more virile.

Aside from virility raising the sensing point by another 6 inches gets it further above the turbulence coming off the wing root, especially at low speed and high angle of attack.
Also less likely to catch it when removing the tail dolly.
UH

This may be a silly question, but isn’t there only one way for it to be oriented correctly for the ports to line up properly?

No, the O-rings seal sections of the tube in the fin, the ports in the probe just empty into that section.