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OAT in Wing Root

Cth6

Well Known Member
For the people that placed there OAT inside of the wing root, does anyone have any pictures that they can share? Installing one this weekend in a 9 to the back of an AV-30.
 
I recommend you move it out to the first to the aileron bell crank area. Mounting in the wing root will have it read 3-4 degrees high.

Carl
 
Inside the wing root is a poor location for an OAT probe.

Here is what Davtron says:

"NOTES: THE TEMPERATURE SENSOR MOUNTING SHOULD BE IN A PLACE THAT IS FREE OF EXHAUST GASES OR COWL FLAPS AIRFLOW. THE IDEAL PLACE IS TWO FEET OUT FROM THE WING ROOT ON THE BOTTOM OF THE WING. SENSOR LEADS MAY BE LENGTHENED OR SHORTENED WITHOUT AFFECTING
CALIBRATION."​


Here is what the SkyView manual says on OAT location:

"Sensor Location

The SV-OAT-340 is an outside air temperature sensor. In order for it work properly, it must be able to measure air temperature accurately. Avoid exposing the sensor to sources of heat that would interfere with outside air temperature readings such as:

  • Direct sunlight
  • Engine heat and exhaust
  • Aircraft interior (back side of sensor)
  • Heated air from the cabin exiting from an open window or cabin air exhaust port
  • The installation area should have space for a nut and wires on the back side of the sensor. It is acceptable to extend or reduce the wire length if necessary. Reduce the wire length by cutting out the desired length from the middle of the wires and splicing together the remaining ends.
  • If there is a backup ADAHRS in the SkyView system, it is acceptable to install a backup OAT sensor a few inches away from the primary sensor. Consider running primary and backup OAT sensor wiring together. Tape sensor wire pairs together to avoid confusion later."


FWIW, my RV-8 (IO-360-M1B) has a Dynon OAT probe on the aft fuselage under the right stab. A friend retrofitted a Davtron OAT probe (for an AV 30) for his RV-8 on the second outboard inspection panel of the left wing. We have compared OAT readings on several occasions when flying close together and they differ by 1°F at the most. I have heard anecdotally that the 'aft fuselage under the right stab' location does not work as well for RV's with larger engines.

My RV-8:

i-bDjcKNz-M.jpg


My friend's RV-8:

i-QXRKfL7-M.jpg
 
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Wants/Needs will dictate accuracy requirement.

I recommend you move it out to the first to the aileron bell crank area. Mounting in the wing root will have it read 3-4 degrees high.

Carl

+1

And more. I had my OAT probe in the wing root and noticed it tracked EGT on a cold day. I moved it outside the prop arc. Lots of locations were tested with thermocouples before moving to the inspection plate on left wing.

I never figured out where/how the heat got to the probe, but data did not lie. On one cold day the OAT changed 10F from rich to lean. EGT went from 900F to 1300F. If it was always 3-4 F then maybe OK, but not knowing with a 10F span is pretty useless.

It all really depends on what accuracy you want/need. A friend built a lightweight 8 and just vented the static to the cabin. No external ports. So it depends on your wants/needs.

Sorry no photo, but mine was mounted through the fuse sidewall aft of the spar (-7) into the cavity. FWIW
 
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When I was putting in a new ADAHRS, I mounted the OAT probe on of the inspection panels on my left wing and ran the wires in the conduit with my pitot wires and AOA tubing. I didn’t want it on the centerline near the exhaust stream. A lot of builders use the fuselage under one of the horizontal stabs as a location but that’s kind of hard on a completed airplane.
 
I put mine in the outer portion of the NACA air vent. Not ideal for several reasons:
the sides of the cowl leak some and so it will read high by a bit, and it is exposed to sunlight which can also raise the temp.

I guess the prop action may also raise air temp a bit.

But, it is well away from the cowl bottom and exhaust.
And install / wiring was very easy.
 
I installed two, because I was curious what the difference would be. My GRT EIS and my GRT EFIS both have OAT inputs, so why not? :D

One in the cabin air vent NACA duct in the left side of the fuselage, and one out near the pitot, under the left wing.

I see about 2-3 degrees of difference in flight.
 
For folks like me who put a real pitot mast under the wing for a heated pitot or AOA sensor pitot, that leaves an abandoned hole in the wing at the location for the Vans-plan stainless steel tube pitot. That hole is in a perfect location to be filled by the OAT sensor, that's where mine lives.
 
For folks like me who put a real pitot mast under the wing for a heated pitot or AOA sensor pitot, that leaves an abandoned hole in the wing at the location for the Vans-plan stainless steel tube pitot. That hole is in a perfect location to be filled by the OAT sensor, that's where mine lives.

Same for me.
 
Far out!!

I have dual OAT's for stand alone screens. I mounted one on each wing just outside of the outer inspection plate. Very accessible if needed and in clean air. Wires are in the tube with the Position/Landing lights.
 
OAT inside of the wing root

Started with that, changed to wing location later.
The readings will be off, the problem being that not only is OAT directly affected, but also the related calculations as in TAS and winds aloft…
 
Close out

To close this one out, I ended up putting it in the inboard wing access panel. A bit of a PITA fishing it through the wing walk ribs, but it is installed. Thank you all for the perspectives.
 
OAT Probe location

Has anyone thought about putting the OAT probe up high on the vertical Stabilizer. Exposed on the outside just under where the rudder horn overlaps it. it is out of the slipstream yet still sensing air temp.

I am putting my ILS/NAV wiskers up there. Its a long wire run, but exposed to air and not in the slipstream or exhaust.

Regards.
 
Garmin says

Has anyone thought about putting the OAT probe up high on the vertical Stabilizer. Exposed on the outside just under where the rudder horn overlaps it. it is out of the slipstream yet still sensing air temp.

I am putting my ILS/NAV wiskers up there. Its a long wire run, but exposed to air and not in the slipstream or exhaust.

Regards.

Garmin says to install OAT probe in a shaded location. Not sure how that can be if on the vertical stabilizer.
 
Extra hole

For folks like me who put a real pitot mast under the wing for a heated pitot or AOA sensor pitot, that leaves an abandoned hole in the wing at the location for the Vans-plan stainless steel tube pitot. That hole is in a perfect location to be filled by the OAT sensor, that's where mine lives.

Been wondering what I was gonna do with that hole and what it was for. Thanks for the great idea. That’s what I love about reading this forum. So many ideas/opinions just have to filter them a little.

Dave
 
Has anyone thought about putting the OAT probe up high on the vertical Stabilizer. Exposed on the outside just under where the rudder horn overlaps it. it is out of the slipstream yet still sensing air temp.

I am putting my ILS/NAV wiskers up there. Its a long wire run, but exposed to air and not in the slipstream or exhaust.

Regards.

On the 10, I placed the OAT on an angle bracket that is bolted to the aft Hor Stab spar attach. Complete shade and the negative pressure of the fuselage is constantly pulling air into the fuse from that area. Seems to be quite accurate, but don't really know if any heated air from the engine area can make it to that area. I know that I am reading cold by a degree or two, as the G3X is reducing the reading by what it assumes is heat generated by the friction of air passing over the probe and my probe is not in the slipstream, seeing that heat. Upside is 0 drag.
 
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