OAT sensor placement

[Rob Shepherd]

Where would be the best place to install an OAT sensor?

I'm assuming somewhere on the underside of the glider but out of the
airstream.

Constructive comments appreciated.

Cheers
Rob

[Charlie M. (UH & 002 owner/pilot)]

I know some just put them in the tubing for a front cockpit vent, this a constant outside airflow. This can be in the nose opening (if you have one) or the channel on the cockpit sides from NACA ducts on the fuselage under the wings.

I am sure you will get many more comments.

[Dan Marotta]

I've installed them in 3 gliders.Â* In the LS-6a and the LAK-17a, I
installed them in the nose vent.Â* My Stemme has a NACA vent on the under
side of the fuselage just about where the pilot's knees are. There's a
removable panel which grants access to the inner surface of the vent.Â* I
simply drilled the proper size hole, glued the temperature probe in the
hole, and ran the wires to the instrument panel.Â* Easy peasy!

On 5/14/2019 8:39 AM, Rob Shepherd wrote:
> Where would be the best place to install an OAT sensor?
>
> I'm assuming somewhere on the underside of the glider but out of the
> airstream.
>
> Constructive comments appreciated.
>
> Cheers
> Rob
>
>
>

--
Dan, 5J

[[email protected]]

What are the implications of not having the sensor directly in an outside airflow stream - other than getting an incorrect temperature reading. What calculations are dependent on the OAT and how will they be affected by having an incorrect temperature?

Robert

On Tuesday, May 14, 2019 at 1:12:22 PM UTC-5, Dan Marotta wrote:
> I've installed them in 3 gliders.Â* In the LS-6a and the LAK-17a, I
> installed them in the nose vent.Â* My Stemme has a NACA vent on the under
> side of the fuselage just about where the pilot's knees are. There's a
> removable panel which grants access to the inner surface of the vent.Â* I
> simply drilled the proper size hole, glued the temperature probe in the
> hole, and ran the wires to the instrument panel.Â* Easy peasy!
>
> On 5/14/2019 8:39 AM, Rob Shepherd wrote:
> > Where would be the best place to install an OAT sensor?
> >
> > I'm assuming somewhere on the underside of the glider but out of the
> > airstream.
> >
> > Constructive comments appreciated.
> >
> > Cheers
> > Rob
> >
> >
> >
>
> --
> Dan, 5J

[Dan Marotta]

True airspeed comes to mind...

On 5/14/2019 2:15 PM, wrote:
> What are the implications of not having the sensor directly in an outside airflow stream - other than getting an incorrect temperature reading. What calculations are dependent on the OAT and how will they be affected by having an incorrect temperature?
>
> Robert
>
> On Tuesday, May 14, 2019 at 1:12:22 PM UTC-5, Dan Marotta wrote:
>> I've installed them in 3 gliders.Â* In the LS-6a and the LAK-17a, I
>> installed them in the nose vent.Â* My Stemme has a NACA vent on the under
>> side of the fuselage just about where the pilot's knees are. There's a
>> removable panel which grants access to the inner surface of the vent.Â* I
>> simply drilled the proper size hole, glued the temperature probe in the
>> hole, and ran the wires to the instrument panel.Â* Easy peasy!
>>
>> On 5/14/2019 8:39 AM, Rob Shepherd wrote:
>>> Where would be the best place to install an OAT sensor?
>>>
>>> I'm assuming somewhere on the underside of the glider but out of the
>>> airstream.
>>>
>>> Constructive comments appreciated.
>>>
>>> Cheers
>>> Rob
>>>
>>>
>>>
>> --
>> Dan, 5J

--
Dan, 5J

[Dave Nadler]

On Tuesday, May 14, 2019 at 10:45:05 AM UTC-4, Rob Shepherd wrote:
> Where would be the best place to install an OAT sensor?

At the very beginning of the air vent intake is usually OK.
Absolutely not further back in the vent channel, as the
indicated temperature will be much higher than OAT when
the vent is closed.

OAT is needed for air density, in turn needed for true airspeed.
Without density corrections many calculations like STF and estimated times
will be wrong (as unfortunately in some popular open source software).
True airspeed must be accurate for good wind calculations.

Number one reason folks have poor wind indication on ILEC SN10
is poor OAT installation, usually because they placed the sensor
in vent duct way behind intake.

Hope that helps!
Best Regards, Dave

PS: If you want to better understand the density effects, it's included here:
https://edwilliams.org/avform.htm
Doesn't have glider polar calculations (left as an exercise for the reader ;-)

[[email protected]]

In the airstream is probably best, since it's hard to measure temperature with an electronic device.
The airstream helps to cool the heat your sensor produces. In the case of a sensor with digital readout, this is influenced by how often you take a measurement.