OAT value error

[Rvator]

i noticed on last flight the OAT was reading 103 F at 3000 Feet which was totally incorrect as airfield temp was only around 8 degrees centigrade.

Aircraft is a RV7 with a dual AFS 3000 installation not built by me. I have located the OAT sensor under the left wing root and it looks undamaged before I investigate further does anyone know the best way to test whether the sensor is faulty?

[Rob Hickman]

What is it reading on the ground?

What are your OAT calibration values?

Is this a new problem?

[Rvator]

Hi Rob

Checked out the following today, to be honest I am unsure whether this is a new issue in as much as it was cld outside when I last flew and a reading OAT value of 103 F at 3000 feet was clearly not right!

I powered up the EFIS which showed a OAT value of 57 F.

By the time I found a pen and paper and then opened up the instrument calibration mode and selected OAT settings it showed:-

Configuration OAT 19.5 deg C / 67.0 deg F

1. Instrument OFF/ON OFF
2. Units FAHRENHEIT
3. Shift Adjust 0.0
4. Num Cal Points 2

AD_VALUE : 10144

Display. (deg F) AD VALUE
32.0 9571
66.0 10202


What stood out was the instrument showed 'OFF'. I changed that to ON and units to Centigrade and pressed 'Save' and exited back to the main display however this still showed a value of 67 F so I repeated the changes and ensured save was selected however when back to the main EFIS display this still showed a Fahrenheit reading but now 57 degs

The EFIS displays are AF-3000 Series Software Version 7.3.7-MVIS

The temperature in the hanger taken from a aircraft type OAT gauge was 6 degs C which should show a value of at least 42.8 degs F

[Rob Hickman]

1. The F / C change is done from the EFIS > SETTINGS >OAT C/F main menu so you can switch it in flight.

2. Your calibration numbers look about right.

The software does a linear interpolation between the calibration points, using your numbers:


AD-VALUE : 10144
32.0 9571
66.0 10202

It should be showing 63F

Are you sure you are not getting heat from the engine on the probe when in flight?

Have you checked for loose OAT connections?

You might want to try replacing the probe.

[Rvator]

Thanks rob for your info.

I will checkout the C/F selection from the Settings > OAT menu.

The OAT sensor is mounted underneath in the left wing root area so ought to be out of the engine exhaust.

You say the Instrument Calibration points appear right and that 63 F should be showing on the EFIS display is that suggesting then that the AD-VALUE of 10144 is being read as an input from the sensor by the software? If so that would imply the sensor is faulty as the temp in the hanger was more like 42 F.

[Rob Hickman]

Adjust the second calibration point to the current temp and AD value and see what happens when you fly it.