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Old 04-16-2016, 01:15 AM
jwilbur jwilbur is offline
Join Date: Dec 2010
Location: Culpeper, VA
Posts: 696

Originally Posted by WrightsRV7 View Post
For what it is worth, on my RV7, I ran mine (Dynon set-up) back with the wires going to the tail and mounted in on the rear inspection panel under the HS. ... .
Thanks. I think I may give this position a try.
-Joe Wilbur
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Old 04-16-2016, 07:02 AM
Weasel's Avatar
Weasel Weasel is offline
Join Date: Dec 2012
Location: Brooksville, MS
Posts: 745

Just another data point. I put the OAT probe in the bulkhead under the rear tail fairing.

The tail area is an area of higher pressure and the small amount of air that leaks in around the elevator horn opening is migrating forward (past the temperature probe) in the fuselage towards the area of lower pressure (cockpit).

By testing multiple times I feel it is as accurate as I need it.

Flying a 3 way gps run with Kevin Horton's spreadsheet calculations shows my TAS within ~1 Knot of the calculated TAS on the efis which uses temperature.

Additionally when in the clouds and the OAT slowly drops to ~34-35 deg F I start picking up light ice on the wings and windshield which is what I would expect.
RV-4 715hr Sold
RV-10 "School Bus" - +1600hr counting
Fisher Classic Cassler Power VW sold
RV-10 N7631T 820hr Sold
RV-8 700+hrs
Carbon Cub 200 hr Sold
One-Off Super Cub 100 hr
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Old 04-16-2016, 07:19 AM
N427EF N427EF is offline
Join Date: Oct 2005
Posts: 1,523
Default Rear NACA

With a dual Dynon set up I have 1 each installed in the left and right rear NACA.
An additional one is located inside the wing root mounted through the
fuselage wall serving my EI engine monitor.
For comparison, I see very little difference between any of the 3 probes in flight. 2 or 3 degrees difference showing up when flying north and the afternoon sun hits the one side of the airplane more than the other.
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 700 plus hours
Running on E10 mogas
Don't believe everything you know.
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Old 01-31-2018, 05:11 PM
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sglynn sglynn is offline
Join Date: Mar 2008
Location: Anacortes, WA
Posts: 828
Default OAT Probe Location

Originally Posted by WrightsRV7 View Post
For what it is worth, on my RV7, I ran mine (Dynon set-up) back with the wires going to the tail and mounted in on the rear inspection panel under the HS. Seemed to give good numbers and not affected by exhaust (i.e. never saw change with power setting changes, attitude, etc..). Very small gage wire so weight etc is no factor. Always seemed to provide accurate true airspeeds as well, to me a very nice benefit of having an OAT hooked to a glass cockpit. Not sure if I could "spin the dial" and get a true airspeed anymore, clearly spoiled by Dynon. Plan on the same location for the 10 I'm building.
Hi, please just to clarify your OAT probe location. I'm mounting mine now for Dynon D10. Are you saying you mounted it out of any air stream and inside the area under the vertical fin? I like it. Seems like this is a perfect location. It would measure air temperature with no affects from any wind warm or cold. Right? Is it a good location?
Steve Lynn
Flying Phase I
Anacortes, WA
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Old 02-02-2018, 03:42 PM
mdaniell mdaniell is offline
Join Date: Oct 2009
Location: Albury, NSW, Australia
Posts: 19

I mounted mine on the right fuse just inside the leading edge wing root cover. There seems to be enough gap to get airflow, and on the right side so on the downswing side of the propeller. Easy routing, it's protected and in the shade when parked. Seems to be consistent with all other available temperature information such as TAFs, AWIS and ATIS.

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Old 02-02-2018, 11:47 PM
bhoppe2 bhoppe2 is offline
Join Date: Apr 2013
Location: nolensville, TN
Posts: 29

I had the same question during my build about where to mount the probe. By searching this forum, I learned that many people have found a variety of wrong places to place the OAT probe. For example, I learned that installing it in the NACA scoop may look cool, but reads hot. Garmin says put it on the underside of the wing. Get it away from the engine and air disturbed by the prop. It should be in the airstream. It is also in the shade on the bottom of the wing, unless you are upside down, which is not recommended in a RV10! Cut, then splice the cable after you have it mounted - not difficult. The Garmin manual says the cable can be extended up to 25 ft. I did not see any reason to reinvent the wheel, repeat mistakes made by others, or over-think it. However, they are experimental aircraft.
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Old 02-03-2018, 03:04 PM
larosta larosta is offline
Join Date: Dec 2010
Location: Redlands, CA
Posts: 180

With regards to mounting the temperature sensor in the NACA inlet. My first reaction is that by design the inlet has some compress-ability in the throat or slightly forward of that area. As we know the gas law tells us that increased pressure comes with increased temperature.

It would be interesting to block the outlet of the scoop and see what the temperature differential is compared to a wide open outlet. Low speed - small variance, high speed - probably increased temperature relative to the OAT.

Just a thought on other factors that may be causing the errors besides engine thermal sources.

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Old 02-03-2018, 05:28 PM
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N941WR N941WR is offline
Join Date: Jan 2005
Location: SC
Posts: 12,887

On my -9 I mounted both on the rear bulkhead, under the empanage fairing. It reads high o the ground but once air starts moving through that area, it is always within a degree, high or low, of people I fly with.

The reason I mounted it there was to keep me from hitting it when I wash the plane.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
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Old 03-26-2020, 05:53 PM
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Pilot135pd Pilot135pd is offline
Join Date: Jan 2019
Location: Vaca Moo Airport - TA37 in East TEXAS
Posts: 1,382

Originally Posted by Auburntsts View Post
Ok. I was in your situation and simply cut the harness, mounted the probe to the inboard most right wing access panel and spliced the harness back together--easy-peazy. No issues in a 100 hrs.
I called Dynon about cutting my OAT cable and splicing a piece into it because I mine is too short. They haven?t returned my call yet. Now that?s it?s been a few years since you did it, is it still a good idea to cut and splice it?
Sadly sold my RV-8 N52VM however I'm still trying to enjoy life by creating an airport with FREE campsites for pilots to come visit WHILE WAITING FOR THE HIGH WING RV15 !

Exempt by 3 out of the 10 ways but I still donated.
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Old 03-26-2020, 06:17 PM
bob888 bob888 is offline
Join Date: Jul 2012
Location: Fresno, CA
Posts: 289

Mine is on the inboard inspection panel of L wing. Installed after wing attach with no problem. Works great...
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