Minimum OAT value?

[nigelspeedy]

Yesterday I flew my RV-8 up to 28000' and on the way I noticed that when the OAT fell below -32C the OAT value was no longer displayed on the PFD. When I downloaded the user data log there was no OAT value recorded. When I descended and it got warmer the OAT display reappeared. Is this normal behavior? Is there a minimum value for a hardware or software reason?
Cheers
Nigel

 

[swatson999]

Whoa! 28000 feet? If that's not a type, isn't that a record for an RV? If so, way to go, man!

 

[krw5927]

What happened to TAS when you lost OAT? Did it go away too?

 

[nigelspeedy]

Yes if you lose OAT, there is no way to calculate TAS and as a result the wind vector goes away as well.

 

[n456ts]

Whoa!  28000 feet?

Wow! 28,100 ft! Was this an experiment or mission related?

 

[nigelspeedy]

Testing my plane is the capstone project for a masters program I am doing. So the ceiling climb was part of the climb performance testing for that. Also just wanted to know how high just in case someone asks. Pretty sure others have been higher, I think I read a Kit Planes article about an RV-7 and he got to 30k and I am pretty sure a Rocket would get higher as well. It is more of an aeromedical challenge than a flying one. Everyone likely thinks about hypoxia but don't forget you run the risk of DCI and the cold is miserable so above 18,000' is possible but not really practical.
Cheers
Nigel

 

[Dynon]

I'm not sure whether the hard limit is it's in the sensor or the software characterization, but there is a lower limit is -30C, it looks like.

 

[nigelspeedy]

Is there an upper limit also? I would have though those in Alaska or Canada would have come across this before.

 

[dynonsupport]

We don't state the range of the SkyView OAT in our manuals (we'll fix that soon). The upper end of our probes themselves (not necessarily what SkyView's displayable limits are) is 150° F or ~66° C.

Is there an upper limit also? I would have though those in Alaska or Canada would have come across this before.

 

[swatson999]

The part is probably qualified -20C to +60C. Might work outside that range, but engineered/tested only to those limits.

That's my guess, anyway (pretty typical engineering qual limits).

 

[mmarien]

Is there an upper limit also? I would have though those in Alaska or Canada would have come across this before.

Never reached an upper limit, but OAT doesn't work between September and May here ;D ;D