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OAT probe location

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Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Mon Jun 18, 2007 6:41 pm Post subject: OAT probe location

I need to determine the location for the Outside Air Temp probe (OAT). I 

heard from one builder that placed it on the bottom of the wing on an 

inspection panel. Are there other god / alternative locations that 

others have used?



Deems Davis # 406

 Engine Stuff & Probes/Sensors

http://deemsrv10.com/

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ScooterF15

Joined: 19 Jun 2006
Posts: 136

Posted: Tue Jun 19, 2007 2:13 am Post subject: OAT probe location

Each of my 2 EFIS units and my engine monitor came with a OAT probe. I  placed one on the most inboard right inspection panel under the wing and one in  each NACA vent. I've seen a lot of posts saying the NACA vents are a bad  location for various reasons, but in practice I've never seen the temperature be  different more than 1 degree between any of the probes when flying. (On the  ground, the sunny side NACA vent probe is typically higher.)

  

 -Jim

 40134

  

 In a message dated 6/18/2007 10:43:21 P.M. Eastern Daylight Time,  deemsdavis(at)cox.net writes:

  	  Quote: 	
		  -->    RV10-List message posted by: Deems Davis <deemsdavis(at)cox.net>



I    need to determine the location for the Outside Air Temp probe (OAT). I    

heard from one builder that placed it on the bottom of the wing on an    

inspection panel. Are there other god / alternative locations that    

others have used?



Deems Davis # 406

Engine Stuff &    Probes/Sensors

http://deemsrv10.com/ 	


 



  

 Jim "Scooter"  McGrew

http://www.mit.edu/~jsmcgrew  



See what's free at AOL.com. 

  [quote][b]

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rnewman(at)lutron.com
Guest

Posted: Tue Jun 19, 2007 5:09 am Post subject: OAT probe location

Here's my experience with OAT in Naca scoop.   (This is in my Glastar)  

I had a definite problem with indicated temps running from 7-10 degrees

high in stabilized cruise.(during the winter).   The OAT probe was

mounted in the naca scoop but quite far back towards the scat tube.   

The root issue was as the amount of air requested by adjusting the

eye-ball vent at the end of the scat tube as controlled by me the

airflow thru the naca scoop would change.   This changed the ballance

between cold outside air flow over the oat probe and the amount of

heating of the naca scoop from inside the airplane.   I could literally

adjust the eyeball vent and see a change in the indicated OAT

temperature.     I'm quite sure that if the OAT probe were moved to near

the front of the scoop it would not have had such a dramatic effect.    

Ultimately I removed the probe from the scoop and mounted at the bottom

of the gear leg fairing,  just poking out into the slipstream.



-Bob



 	  Quote: 	
		  >> JSMcGrew(at)aol.com 6/19/2007 6:11 AM >>>

 
	


 

Each of my 2 EFIS units and my engine monitor came with a OAT probe. I 



placed one on the most inboard right inspection panel under the wing

and one in  

each NACA vent. I've seen a lot of posts saying the NACA vents are a

bad  

location for various reasons, but in practice I've never seen the

temperature be  

different more than 1 degree between any of the probes when flying. (On

the  

ground, the sunny side NACA vent probe is typically higher.)

 

-Jim

40134

 

In a message dated 6/18/2007 10:43:21 P.M. Eastern Daylight Time,  

deemsdavis(at)cox.net writes:






I  need to determine the location for the Outside Air Temp probe (OAT).

I  

heard from one builder that placed it on the bottom of the wing on an 



inspection panel. Are there other god / alternative locations that  

others have used?



Deems Davis # 406

Engine Stuff &  Probes/Sensors

http://deemsrv10.com/ 



 

Jim "Scooter"  McGrew

_http://www.mit.edu/~jsmcgrew_ (http://www.mit.edu/~jsmcgrew)  



************************************** See what's free at

http://www.aol.com.

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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ScooterF15

Joined: 19 Jun 2006
Posts: 136

Posted: Tue Jun 19, 2007 5:30 am Post subject: OAT probe location

That makes sense. It sounds like I placed mine a bit further forward than  you.

  

 -Jim

 40134

  

  

  

 In a message dated 6/19/2007 9:11:49 A.M. Eastern Daylight Time,  rnewman(at)lutron.com writes:

  	  Quote: 	
		  -->    RV10-List message posted by: "Bob Newman"    <rnewman(at)lutron.com>



Here's my experience with OAT in Naca    scoop.   (This is in my Glastar)  

I had a definite problem    with indicated temps running from 7-10 degrees

high in stabilized    cruise.(during the winter).   The OAT probe was

mounted in the    naca scoop but quite far back towards the scat tube.   

The root    issue was as the amount of air requested by adjusting the

eye-ball vent at    the end of the scat tube as controlled by me the

airflow thru the naca    scoop would change.   This changed the ballance

between cold    outside air flow over the oat probe and the amount of

heating of the naca    scoop from inside the airplane.   I could literally

adjust the    eyeball vent and see a change in the indicated OAT

temperature.        I'm quite sure that if the OAT probe were moved to near

the    front of the scoop it would not have had such a dramatic effect.       

Ultimately I removed the probe from the scoop and mounted at the    bottom

of the gear leg fairing,  just poking out into the    slipstream.



-Bob



 	  Quote: 	
		  >> JSMcGrew(at)aol.com 6/19/2007 6:11 AM    >>>


	




Each of my 2 EFIS units and my engine monitor came    with a OAT probe. I 



placed one on the most inboard right inspection    panel under the wing

and one in  

each NACA vent. I've seen a lot    of posts saying the NACA vents are a

bad  

location for various    reasons, but in practice I've never seen the

temperature be     

different more than 1 degree between any of the probes when flying.    (On

the  

ground, the sunny side NACA vent probe is typically    higher.)



-Jim

40134



In a message dated 6/18/2007 10:43:21    P.M. Eastern Daylight Time,  

deemsdavis(at)cox.net    writes:



-->  RV10-List message posted by: Deems Davis    <deemsdavis(at)cox.net>



I  need to determine the location for    the Outside Air Temp probe (OAT).

I  

heard from one builder that    placed it on the bottom of the wing on an 



inspection panel. Are there    other god / alternative locations that  

others have    used?



Deems Davis # 406

Engine Stuff &     Probes/Sensors

http://deemsrv10.com/ 

	


 



  

 Jim "Scooter"  McGrew

http://www.mit.edu/~jsmcgrew



See what's free at AOL.com.

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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Tim Olson

Joined: 25 Jan 2007
Posts: 2872

Posted: Tue Jun 19, 2007 5:32 am Post subject: OAT probe location

I'm just wondering.... knowing that factors such as the sun,

and engine heat, propwash, exhaust, vent opening/closing,

and things like that can affect OAT reading, why do people

even consider such poor mounting locations as the NACA inlet,

wing root fairing, and places like that.....other than because

it's an easy/lazy way to get yourself an OAT reading?  Wouldn't

it be better just to take 20 extra minutes and run the wires

needed to give an accurate indication?  On my system it's

treated as critical enough that you even have a calibration

procedure to adjust for compression effects of flying at

170kts and the slight rise in temp that you get from

airspeed changes.  It's just disconcerting to see that people

just don't really seem to care about some things.

(This is not directed at you Bob, so please take no offense)



To continue the rant a little, I think i'll start a new post...

(I'm just in one of those moods today I guess)



Tim Olson - RV-10 N104CD - Flying



Bob Newman wrote:

 	  Quote: 	
		   

 

 Here's my experience with OAT in Naca scoop.   (This is in my Glastar)  

 I had a definite problem with indicated temps running from 7-10 degrees

 high in stabilized cruise.(during the winter).   The OAT probe was

 mounted in the naca scoop but quite far back towards the scat tube.   

 The root issue was as the amount of air requested by adjusting the

 eye-ball vent at the end of the scat tube as controlled by me the

 airflow thru the naca scoop would change.   This changed the ballance

 between cold outside air flow over the oat probe and the amount of

 heating of the naca scoop from inside the airplane.   I could literally

 adjust the eyeball vent and see a change in the indicated OAT

 temperature.     I'm quite sure that if the OAT probe were moved to near

 the front of the scoop it would not have had such a dramatic effect.    

 Ultimately I removed the probe from the scoop and mounted at the bottom

 of the gear leg fairing,  just poking out into the slipstream.

 

 -Bob

 

>>> JSMcGrew(at)aol.com 6/19/2007 6:11 AM >>>

  

  

 Each of my 2 EFIS units and my engine monitor came with a OAT probe. I 

 

 placed one on the most inboard right inspection panel under the wing

 and one in  

 each NACA vent. I've seen a lot of posts saying the NACA vents are a

 bad  

 location for various reasons, but in practice I've never seen the

 temperature be  

 different more than 1 degree between any of the probes when flying. (On

 the  

 ground, the sunny side NACA vent probe is typically higher.)

  

 -Jim

 40134

  

 In a message dated 6/18/2007 10:43:21 P.M. Eastern Daylight Time,  

 deemsdavis(at)cox.net writes:

 

 

 

 I  need to determine the location for the Outside Air Temp probe (OAT).

 I  

 heard from one builder that placed it on the bottom of the wing on an 

 

 inspection panel. Are there other god / alternative locations that  

 others have used?

 

 Deems Davis # 406

 Engine Stuff &  Probes/Sensors

 http://deemsrv10.com/ 

 

 

 

  

 Jim "Scooter"  McGrew

 _http://www.mit.edu/~jsmcgrew_ (http://www.mit.edu/~jsmcgrew)

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

rnewman(at)lutron.com
Guest

Posted: Tue Jun 19, 2007 7:09 am Post subject: OAT probe location

Jim,   Yours are definetly in a better position than mine were.    When

we installed them we were going for stealth.    But we outsmarted

ourselves!

 	  Quote: 	
		  >> JSMcGrew(at)aol.com 6/19/2007 9:27 AM >>>

That makes sense. It sounds like I placed mine a bit further forward

than  

you.

-Jim

40134

In a message dated 6/19/2007 9:11:49 A.M. Eastern Daylight Time,  

rnewman(at)lutron.com writes:

Here's my experience with OAT in Naca  scoop.   (This is in my Glastar)

I had a definite problem  with indicated temps running from 7-10

degrees

high in stabilized  cruise.(during the winter).   The OAT probe was

mounted in the  naca scoop but quite far back towards the scat tube.  

The root  issue was as the amount of air requested by adjusting the

eye-ball vent at  the end of the scat tube as controlled by me the

airflow thru the naca  scoop would change.   This changed the ballance

between cold  outside air flow over the oat probe and the amount of

heating of the naca  scoop from inside the airplane.   I could

literally

adjust the  eyeball vent and see a change in the indicated OAT

temperature.   I'm quite sure that if the OAT probe were moved to near

the  front of the scoop it would not have had such a dramatic effect.  

Ultimately I removed the probe from the scoop and mounted at the 

bottom

of the gear leg fairing,  just poking out into the  slipstream.

-Bob

 	  Quote: 	
		  >> JSMcGrew(at)aol.com 6/19/2007 6:11 AM  >>>

Each of my 2 EFIS units and my engine monitor came  with a OAT probe. I

placed one on the most inboard right inspection  panel under the wing

and one in  

each NACA vent. I've seen a lot  of posts saying the NACA vents are a

bad  

location for various  reasons, but in practice I've never seen the

temperature be   

different more than 1 degree between any of the probes when flying. 

(On

the  

ground, the sunny side NACA vent probe is typically  higher.)

-Jim

40134

In a message dated 6/18/2007 10:43:21  P.M. Eastern Daylight Time,  

deemsdavis(at)cox.net  writes:

I  need to determine the location for  the Outside Air Temp probe

(OAT).

I  

heard from one builder that  placed it on the bottom of the wing on an

inspection panel. Are there  other god / alternative locations that  

others have  used?

Deems Davis # 406

Engine Stuff &   Probes/Sensors

http://deemsrv10.com/ 

Jim "Scooter"  McGrew

_http://www.mit.edu/~jsmcgrew_ (http://www.mit.edu/~jsmcgrew) 

************************************** See what's free at

http://www.aol.com.

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

rnewman(at)lutron.com
Guest

Posted: Tue Jun 19, 2007 7:18 am Post subject: OAT probe location

No offense taken.   We were adding OAT to an already built plane, 

before we fully appreciated the effects or criticality of its position. 

   Pulling new wires to a new location in a plane with a very full and

complete interior is quite a project.   However,  given 20/10 hindsight

it would have been way less work to do it right the first time !!   That

mistake I will not make again...(oh yeah, one other thing, when we

originally did this,  we were VFR only and   OAT was just nice to have, 

now that I have IFR capabilty, the attention to these types of detail

moved up by orders of magnitude)

-Bob

 	  Quote: 	
		  >> Tim(at)MyRV10.com 6/19/2007 9:32 AM >>>

I'm just wondering.... knowing that factors such as the sun,

and engine heat, propwash, exhaust, vent opening/closing,

and things like that can affect OAT reading, why do people

even consider such poor mounting locations as the NACA inlet,

wing root fairing, and places like that.....other than because

it's an easy/lazy way to get yourself an OAT reading?  Wouldn't

it be better just to take 20 extra minutes and run the wires

needed to give an accurate indication?  On my system it's

treated as critical enough that you even have a calibration

procedure to adjust for compression effects of flying at

170kts and the slight rise in temp that you get from

airspeed changes.  It's just disconcerting to see that people

just don't really seem to care about some things.

(This is not directed at you Bob, so please take no offense)

To continue the rant a little, I think i'll start a new post...

(I'm just in one of those moods today I guess)

Tim Olson - RV-10 N104CD - Flying

Bob Newman wrote:

 	  Quote: 	

 Here's my experience with OAT in Naca scoop.   (This is in my

Glastar)  

 	  Quote: 	
		   I had a definite problem with indicated temps running from 7-10

degrees

 	  Quote: 	
		   high in stabilized cruise.(during the winter).   The OAT probe was

 mounted in the naca scoop but quite far back towards the scat tube.  

 	  Quote: 	
		   The root issue was as the amount of air requested by adjusting the

 eye-ball vent at the end of the scat tube as controlled by me the

 airflow thru the naca scoop would change.   This changed the

ballance

 	  Quote: 	
		   between cold outside air flow over the oat probe and the amount of

 heating of the naca scoop from inside the airplane.   I could

literally

 	  Quote: 	
		   adjust the eyeball vent and see a change in the indicated OAT

 temperature.     I'm quite sure that if the OAT probe were moved to

near

 	  Quote: 	
		   the front of the scoop it would not have had such a dramatic effect. 

 	  Quote: 	
		   Ultimately I removed the probe from the scoop and mounted at the

bottom

 	  Quote: 	
		   of the gear leg fairing,  just poking out into the slipstream.

 -Bob

>>> JSMcGrew(at)aol.com 6/19/2007 6:11 AM >>>

 Each of my 2 EFIS units and my engine monitor came with a OAT probe.

I 

 	  Quote: 	

 placed one on the most inboard right inspection panel under the wing

 and one in  

 each NACA vent. I've seen a lot of posts saying the NACA vents are a

 bad  

 location for various reasons, but in practice I've never seen the

 temperature be  

 different more than 1 degree between any of the probes when flying.

(On

 	  Quote: 	
		   the  

 ground, the sunny side NACA vent probe is typically higher.)

 -Jim

 40134

 In a message dated 6/18/2007 10:43:21 P.M. Eastern Daylight Time,  

 deemsdavis(at)cox.net writes:

 I  need to determine the location for the Outside Air Temp probe

(OAT).

 	  Quote: 	
		   I  

 heard from one builder that placed it on the bottom of the wing on an

 	  Quote: 	

 inspection panel. Are there other god / alternative locations that  

 others have used?

 Deems Davis # 406

 Engine Stuff &  Probes/Sensors

 http://deemsrv10.com/ 

 Jim "Scooter"  McGrew

 _http://www.mit.edu/~jsmcgrew_ (http://www.mit.edu/~jsmcgrew)

- The Matronics RV10-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

ddddsp1(at)juno.com
Guest

Posted: Tue Jun 19, 2007 8:38 am Post subject: OAT probe location

Tim, 

Starting a fight online?    lol..............Did you get some bad mist off the Niagara that put you in this mood?      

INJEST> 

Dean    805HL 



_____________________________________________________________

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