JPI OAT Probe Location

[Schinderhannes]

I am planning the installation of a EDM830 in our 1970 M20C and was wondering what the best location for the OAT probe is.

 

Thank you,

Frank.

[Aerodon]

run it out to one of the inspection covers under the wing.  A lot of work, but then a lot of confidence in the accuracy - in the shade away from any engine heat.

 

Aerodon

[hypertech]

Without consulting me, the avionics shop stuck mine in the side of the fuselage in the NACA duct.  I'm considering options to have it moved and that hole repaired next time I have work done (at another shop).  The factory OAT probe in the ovation at least is under the right wing maybe 2/3 of the way out.  I assumed that when the gauges were replaced, the new probe would go where the old probe was but I guess I should have been more insistent and/or got that in writing.

[DXB]

My installer put it on the  underside of the left wing root a bit behind the leading edge.  I think that is a common mounting location.  The temp either agrees with the oat probe for my Aspen pfd (part of the RSM on the back of the plane), or runs 1 degree C hotter.  The marginally hotter reading might indeed reflect proximity to the engine. 

Edited April 18, 2019 by DXB

[ArtVandelay]

Without consulting me, the avionics shop stuck mine in the side of the fuselage in the NACA duct.  I'm considering options to have it moved and that hole repaired next time I have work done (at another shop). 

That’s where mine is, so it runs about 2-3° warmer if wind/temp forecasts are accurate. JPI allows you to adjust manifold pressure readings, too bad they don’t do that for temperature readings as well.
The problem is the temperature probe is rather large and not aerodynamic. I gave this some thought and other than a slight difference it causes in TAS calculation, it seems like it’s a very minor issue.


Tom

[hypertech]

I thought about it being much bigger than the OEM probe - not really sure why the OEM probe style can't be used with the JPI but that a separate issue.  And then I thought about the pitot tube that is much bigger an in the other wing.  So, if anything seems like it would even the drag out.  That should let me use less rudder and pick up at least 5 knots.

[kortopates]

I would have them move it out to either under the wing or back under the tail - the rear will work well. But the NACA cockpit air scoops are known poor places. In your defense you can point to JPI install instructions which had they been following would have had them placing it under the co-pilot wing. But many installers use the duct because it simplifies the install tremendously compared to pulling the wire through the wing or tail.


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[jaylw314]

1 hour ago, ArtVandelay said:

That’s where mine is, so it runs about 2-3° warmer if wind/temp forecasts are accurate. JPI allows you to adjust manifold pressure readings, too bad they don’t do that for temperature readings as well.
The problem is the temperature probe is rather large and not aerodynamic. I gave this some thought and other than a slight difference it causes in TAS calculation, it seems like it’s a very minor issue.


Tom

IIRC, the 730/830 does allow you to adjust the OAT reading from the sensor?

[ArtVandelay]

IIRC, the 730/830 does allow you to adjust the OAT reading from the sensor?

You’re right, I went through the 900 installation manual, it does have a calibration step, I’ll just make an adjustment.


Tom