OAT reading high?

[swatson999]

I located my OAT probe, as many others have, under the empennage fairing, on the rear bulkhead of my RV-7A. I'm pretty convinced it's reading too high...WAY too high initially, then somewhat too high in flight (although, that's hard to calibrate).

Under ambient conditions in the hangar, it's right on with known outside air temperatures (and matches every other temp sensor on the system after everything has reached ambient...EGT, CHT, Oil Temp). But once outside, it shows quite a bit higher than the actual temperate on the field. I suspect I'm getting conducted heat from the unpainted fuselage skins heating up in the sun...

Has anyone tried putting some sort of isolation between the bulkhead and the sensor? Maybe a nylon washer or something like that?

TIA!

Steve

 

[cperry]

I had my OAT probe mounted under the tail cone on my RV9A, and was also reading high. I determined it was the exhaust gas causing it. I've temporarily moved it to inside the tail cone and seems to be reading nearly ok now (still some rise as the cabin heat/sun warms things up). I'll probably move it to the underside of the wing near the center inspection cover for a more permanent location.

 

[shenweas]

Mine is in the same location that you have and I would say it is dead on verified by ICE forming on the wings precisely when it drops to 33F in the clouds.

Are you sure its not correct?

Early in the winter mornings and sometimes throughout the days there is an inversion with freezing on the surface and I have seen as high as 45 deg up at 4000ft. It can mess with you if your already in doubt.

 

[swatson999]

I'll do some more checking, and take some sort of thermometer to verify the actual OAT near the hangar, etc., and compare it. Will also check with others in flight next time we're up together to see how they compare (but then, you have the problem of who is right and who is wrong ).

I'm just thinking that unpainted skin gets *hot* quickly in the sun, and some of that heat is finding its way to the bulkhead and thence to the sensor....