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OAT placement: Where?

We put ours on the right side duct. BAD PLACE! It's getting heat from somewhere and always reads high in flight.
 
You will get some heat anywhere just aft of the firewall (besides the fact that it is in the sun). I have mine just under the starboard horizontal stabilizer. Works great.
 
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Engine is hot

Ricky D said:
I'm thinking of putting the oat in the fresh air intake I'm open for opinions
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Agree bad idea. The further from the engine, aft or outboard or both the better. Mel's idea is good, may be in the aft access panel under the horz stab as he suggested.
 
I put mine under the VS. Click on attached picture.

My hope is that once I start moving enough fresh air will move through there so it will read correctly. If not, I will relocate it under the HS like Mel.

 
Just put it under the wing and KNOW that it will be accurate (once calibrated). Anywhere near the fuselage and you're just askin' for inaccuracy. What does "works great" mean exactly in this context? How can you really confirm that your OAT works at altitude, until you've flown in moisture in and out of the freezing level. My 2 cents, having inadvertently gotten into icing conditions in IMC -- the OAT's accuracy can make a huge difference in the safe conclusion of a flight. Why take a chance? Put it in one of the inspection panels on the underside of the wing (or next to one like I did if you don't want to have to remove it when the panel comes off), and you won't be sorry you did. Put it somewhere near the fuselage, and you might be sorry (might luck out, too!).
 
Wing Install

Dan,

In your OAT wing install, did you cut the line and supply a wing root connector?
 
smithhb said:
In your OAT wing install, did you cut the line and supply a wing root connector?
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Nope. I don't have a single wing root connection. Don't want to start that argument again again again.
 
Wing-Root Connections

Sorry, just curious. I looked for but couldn't find the section on your website about "Wing Root Connections". I would be interested (and I'm sure others would as well) in how you accomplished your terminations, i.e., pitot, lights/strobes, antennas, OAT, and avoided wing-root connectors. I like this concept but wonder if it is REALLY worth the trouble.
 
To be honest, I don't even want to reply about wing root connections. It will just turn this thread into an unrelated debate. I'm pretty certain this topic has been hashed and rehashed on VAF Forums already. Search for "wing root connections" or something like that. If you want my opinion off-list, email me at [email protected]. Trying to stay constructive here.
 
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dan said:
What does "works great" mean exactly in this context?

What I mean by "works great" is that it gives me the temperature that I expect, It agrees with several other aircraft (VFR & IFR, certified & amateur-built) at altitude. My airplane is day/night VFR. If you are planning to fly IFR and/or in icing conditions, then by all means, DON'T follow my lead. For my operations OAT is quite insignificant.
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N941WR said:
I put mine under the VS. Click on attached picture.
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Playing devil's advocate here... Plane sits out in the sun for an hour on a hot summer day. The "greenhouse" effect under the emp fairing will cause your OAT to read higher than the actual air temp. How long after takeoff will it equalize with actual OAT?

How sensitive to change will it be mounted there? I would bet it will lag noticeably...and how will you know it's lagging?

I think Mel hit the nail on the head. If you're VFR only, OAT isn't critical, so put your probe wherever you want to. But if you or any future owner of the plane has any intention of flying in the clouds, I wouldn't take any chances. Max accuracy and max sensitivity means:
- mount it away from any potential source of heat
- mount it where it will be IN THE AIR STREAM
- mount it where it will be in the shade

After all, it's not IAT (inside air temp) or OHAT (outside heated air temp), it's OAT!
 
Dan is right. It needs to be OUTSIDE. If you don't think that fiberglass gives a greenhouse effect, then you have never stood under a fiberglass patio cover. Another point; if you are running cabin heat, some of that air is likely to migrate back to the empennage fairing.
 
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Good points all, and I can add that even if you put the OAT probe on the bottom side of the tailcone...waaaaayyyy back there...it will still pick up heat from the engine. BTDT.

It needs to be up in free air uninfluenced by engine heat. I tried mine on a fairing--outside the tailcone--above the horizontal stab. It agrees with Dan's readout to 1 deg F at altitude; good enough for me.

--Marc
 
dan said:
Playing devil's advocate here... Plane sits out in the sun for an hour on a hot summer day. The "greenhouse" effect under the emp fairing will cause your OAT to read higher than the actual air temp. How long after takeoff will it equalize with actual OAT?
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After all, it's not IAT (inside air temp) or OHAT (outside heated air temp), it's OAT!
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I just knew I was going to hear about this when I made that post.

A little justification is in order.
1. I have exchanged emails with a few others who have placed it there, it seems to work for them.
2. My -9 will be a VFR ship and I don't really care about TAS
3. The Dynon OAT plugs into the remote compass, which is back in the tail so running the wire out to the wing would be a PITA.
4. This will be a tail dragger and my fear is that putting it under the HS might subject it to some damage.
5. It will be easy enough to move later as I left enough wire to do so, if needed.
6. I checked with Dynon, they thought it might work out fine there.

There are a lot of down sides to this installation, as pointed out. I figure it will read high when I first get in the plane but after some air starts moving through that area, it should cool right down. Once it is flying, I will come back and let you know how it works.
 
OAT probe for Dynon D-10A

http://www.n2prise.org/rv9a126.htm#May14

The link above shows my OAT probe under the horizontal stabilizer on the RIGHT side elevator control horn access plate. I use the Dynon true airspeed readout every time I get in cross-country cruise mode. A comparison of the TAS with the GPS ground speed tells me if the forecast winds aloft agree with the flight plan for fuel management on long runs, LIKE DENVER recently from Chattanooga, TN.

Jerry K. Thorne
East Ridge, TN
RV-9A N2PZ 189.6 Hobbs hours
 
pax naca vent

Drilled a hole in the passenger's NACA vent and glued it in with instrument-safe RTV. It is in the shade, away from the fuselage, and has a steady flow of air over it when the wheels are rolling.
 
Heated Vent Air

n468ac said:
We put ours on the right side duct. BAD PLACE! It's getting heat from somewhere and always reads high in flight.
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Same here. Not only does mine read high, the air coming in through the cabin eyeball vents on the RV-6A is hotter than ambient by 10-15 degrees! Apparently having the air scoops so close behind the cowl lets hot engine air travel along the fuselage and right into the inlet. Thinking about putting a couple of those clear plastic scoops in the canopy. Any better ideas to get cool air into the cabin? Thanks, Dick
 
Dick Chevalier said:
Same here. Not only does mine read high, the air coming in through the cabin eyeball vents on the RV-6A is hotter than ambient by 10-15 degrees! Apparently having the air scoops so close behind the cowl lets hot engine air travel along the fuselage and right into the inlet. Thinking about putting a couple of those clear plastic scoops in the canopy. Any better ideas to get cool air into the cabin? Thanks, Dick
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No, other than going higher.
 
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