Location of OAT Probe

[istrumit]

I have noticed that my OAT, which is located in the fresh air scoop on the copilot side, never reads what the weather service forecasts. It always reads higher by several degrees.

I believe, but I am not sure, that the front air vents also seem let in warmer air than I expect based on my altitude. I will measure this to confirm.

But, I suspect my OAT is reading high because, unlike most RV-10s, I have two sets of cowling vents. I have the standard bottom ones, but also side ones on the bottom cowling, about 3 inches below where the top and bottom cowlings meet (9.5:1 pistons, so I am guessing the builder was trying to enhance cooling).

I think hot air from the cowling exit is mixing with outside air and entering the fresh air vents.

First - Does this seem like a reasonable suspicion ?
And Two - where to relocate the probe if needed ?

Thanks,

Scott

[Auburntsts]

If you do opt to relocate, I put mine on the bottom of the right wing just aft of the inboard access cover. Works fine in that location.

[ChiefPilot]

That's a known issue and your suspicions are correct. Underneath the wing or horizontal tail is where most seem to find the most accurate indication.

Originally Posted by istrumit

I have noticed that my OAT, which is located in the fresh air scoop on the copilot side, never reads what the weather service forecasts. It always reads higher by several degrees.

I believe, but I am not sure, that the front air vents also seem let in warmer air than I expect based on my altitude. I will measure this to confirm.

But, I suspect my OAT is reading high because, unlike most RV-10s, I have two sets of cowling vents. I have the standard bottom ones, but also side ones on the bottom cowling, about 3 inches below where the top and bottom cowlings meet (9.5:1 pistons, so I am guessing the builder was trying to enhance cooling).

I think hot air from the cowling exit is mixing with outside air and entering the fresh air vents.

First - Does this seem like a reasonable suspicion ?
And Two - where to relocate the probe if needed ?

Thanks,

Scott

[n82rb]

I was at snf two years ago and was going to install my skyview system starting the day after SNF. I was looking at an RV-8 that had 2 OAT probes under the tail and another one up front. the owner was there and i asked him about it. come to find out, it was a test bed for dynon. he said that the best place in his option was under the horizontal on the fuse. so that is where mine is and reads almost exactly what the OAT is.

bob burns

[istrumit]

I suppose I will relocate mine to the underside of the wing, sufficiently away from the fuselage.

Is special thermo-couple wiring required ?

What kind ? And where to source ?

[Auburntsts]

Originally Posted by istrumit

I suppose I will relocate mine to the underside of the wing, sufficiently away from the fuselage.

Is special thermo-couple wiring required ?

What kind ? And where to source ?

No it's regular shielded tefzel. I don't remember off hand how many conductors but seem to recall it's 3.

[Toobuilder]

I tried under the stab, above the stab and halfway up the vertical, living in the hinge cove on the Rocket and never could get accurate free air temp. The 540 puts out too many BTU's. I bit the bullet and mounted it in the wing right in the wake of the pitot mast to keep the impact error out of it. Works great now.

[Jesse]

I always get the best results under the HS, and usually on the right side. This location works great for systems that have the OAT probe plug into an ADAHRS or magnetometer that lives in the tail.

[lr172]

Originally Posted by Jesse

I always get the best results under the HS, and usually on the right side. This location works great for systems that have the OAT probe plug into an ADAHRS or magnetometer that lives in the tail.

Jesse,

Have you ever tried it on the Left side? I have mine under the HS on the left side. It was only after I installed it that I thought about the slip stream hitting the left side and bringing engine heat with it. I have a feeling I am reading a bit high, but don't have a way to prove it.

Larry

[glenn654]

I put my OAT in the wing root and have had good accuracy and no extra drag.

Glenn Wilkinson