OAT Display in C or F

[Skates97]

Pretty simple question, do you have your display set for Celsius or Fahrenheit and why?

[carusoam]

There are two times you really want to know the actual OAT....

1) When calculating T/O performance while on the ground.... °F is mostly available around the airport...

2) When determining strategy for getting out of icing conditions.... °C is pretty easy to work with, memory wise...

3) I have an analog one still...

So.... can you flop between the two?

PP thoughts only, not an instrument or weather guru...

Best regards,

-a-

[Andy95W]

38 minutes ago, Skates97 said:

Pretty simple question, do you have your display set for Celsius or Fahrenheit and why?

Not really that simple for me because I needed another option:  Both.

I have OAT on my JPI that is set to °F.  When I installed my G5s, I also have OAT there.  I tried to get them to read the same temperature, but that just isn’t possible with 2 different probes in 2 different locations.

So I took the easy way out- JPI is in °F, G5 is in °C.  

My OCD feels satisfied that way.  

[carusoam]

Brilliant Andy!

Solving two problems with one stone.

-a-

[DCarlton]

Interesting timing.  During my last fight I looked over at my engine monitor and muttered that I needed to change my OAT from C to F.  I can relate to F more quickly during hot summer weather. 

Edited April 23, 2021 by DCarlton

[RLCarter]

1 hour ago, DCarlton said:

Interesting timing.  During my last fight I looked over at my engine monitor and muttered that I needed to change my OAT from C to F.  I can relate to F more quickly during hot summer weather. 

Here in S. TX I use Celsius in the summer, 40°c just sounds better than 104°f 

[Niko182]

C.

Icing = 0 C.

Its easier to think 0 or close to 0 when thinking of freezing temps at least in my mind.

[ArtVandelay]

I prefer metric in general.

It’s a better system.

[Hank]

32 minutes ago, ArtVandelay said:

I prefer metric in general.

It’s a better system.

Distances are impractical small. I have 30' long machines at work spec'ed in millimeters. Other units, often electrical, are too large--really large capacitors are often micro-Farads, ones in your computer are pico-Farad. Then there's the practice of naming unit combinations after people, i.e., force is measured in Newtons, which are kg x meters / seconds-squared, and when solving engineering and physics issues you need to know the basic units for each Famous Name to cancel out and see what's left over.

I worked with both sets all through high school and college, and still don't know if I would feel 10 N on my forehead or if it would kill me.

Kilometers are probably a decent unit of distance in those little European countries you can cross by normal train in an afternoon. But here? Nah . . . .  

[N201MKTurbo]

Celsius or centigrade for temperature. All I really care about is ice. 
 

As far as the metric system in general, we do everything at work in metric. I think in metric now.

Our military customers still want things in English units, that is a pain. 
 

 

[GeeBee]

Back when we used to have what was known as the "ARM", Airport Restrictions Manual, I asked a Performance Engineer why the temps were in F when the METAR was in C. He gave a very logical answer. F is a smaller unit of thermal activity so you could be more accurate in the performance calculation. Sort of like using a tape measure graduated to 1/16 increments rather than 1/4. In a "dough!" moment he also pointed out that the METAR contains a very accurate temp to the 1/10 C in the remarks and that is what they use for the automated performance. He went on to say one should convert the remarks section C to F if doing a manual performance out of the ARM to get the most accurate result.

That all said, I've got to the point where I can go back in forth in my head for key numbers, such a 0 and 32, 8 and 46 (enroute icing correction), 10 and 50 (engine anti-ice), 20 and 70 (68 actually, nice day). A quick wag is to double C. add three to the 10s, it gets you close.

 

[N201MKTurbo]

My old Scott OAT gauge had both C and F, you could look at any temperature and and instantly convert  it.

Edited April 23, 2021 by N201MKTurbo

[flyboy0681]

22 minutes ago, N201MKTurbo said:

My old Scott OAT gauge had both C and F, you could look at any temperature and and instantly convert  it.

I would say most mechanical gauges don't have a dual scale, which always puzzled me. How difficult would it have been to paint an additional scale? Wonders never cease.

As for English vs Metric, I've been to England many times and that country is clearly stuck between the two. Motorway distance signs are in miles yet you pull up to the petrol station and pay by the liter.

[201er]

Honestly this is a no-brainer as everything in US Aviation is based on temperature in Celsius from the POH to the AWOS. Fahrenheit OAT is useless information.

 

 

[Skates97]

10 hours ago, Andy95W said:

Not really that simple for me because I needed another option:  Both.

I have OAT on my JPI that is set to °F.  When I installed my G5s, I also have OAT there.  I tried to get them to read the same temperature, but that just isn’t possible with 2 different probes in 2 different locations.

So I took the easy way out- JPI is in °F, G5 is in °C.  

My OCD feels satisfied that way.  

I hadn't thought of this. My JPI and G5 read very close but don't quite agree. The G5 probe is in the wing and more accurate than the JPI that is in the left air intake and catches a little heat from the cowl area (still don't know why it is in the install manual to put it there). Putting the G5 in C° would give me a closer look for icing and the JPI gives me what my brain still thinks in.

7 minutes ago, 201er said:

Honestly this is a no-brainer as everything in US Aviation is based on temperature in Celsius from the POH to the AWOS. Fahrenheit OAT is useless information.

 

 

Not quite so fast. Everything in the C POH is in F°.

 

49 minutes ago, N201MKTurbo said:

My old Scott OAT gauge had both C and F, you could look at any temperature and and instantly convert  it.

I still have that one in the window right in front of the storm window.

[flyboy0681]

20 minutes ago, 201er said:

Honestly this is a no-brainer as everything in US Aviation is based on temperature in Celsius from the POH to the AWOS. Fahrenheit OAT is useless information.

 

 

Can't say the last time I saw CHT's in Celsius.

[Tim Jodice]

7 hours ago, Niko182 said:

C.

Icing = 0 C.

Its easier to think 0 or close to 0 when thinking of freezing temps at least in my mind.

I use Celsius. This is the only thing I care about 98% of the time I look at it is ice. It is rare I am looking for a max performance take off so I really don't care how it performs in the heat.

[kortopates]

Can't say the last time I saw CHT's in Celsius.

Interestingly, I actually see a number of foreign Mooney's engine analyzer data using C for CHT and EGT, as well as LPH for FF. Not easy for me to adjust.

Of course not from the factory that way, except you'll see a lot of fuel level gauges in pounds.

 

 

Sent from my iPhone using Tapatalk

[Hank]

In my C, OAT, CHT, EGT and Oil Temp are in °F, which matches the information in my Owners Manual (similar to Richard's above).

But my optional (I'm guessing aftermarket) Carb Temp gage is in °C . . . .

[Niko182]

3 hours ago, Skates97 said:

Not quite so fast. Everything in the C POH is in F°.

In the newer models they seem to have switched to Celsius, however, In my experience I've never grabbed the POH while I was in the airplane to check takeoff, or climb performance. If I needed to check that, I'm doing it based on a forecast anyway, before I'm anywhere near the aircraft.

I'd say the best bet is fly 30 days with it on Celsius, and 30 days with it on Fahrenheit. If the difference wasn't noticeable, then it doesn't matter anyway. If it was, use which ever one you preferred.

[gsxrpilot]

I chose C as that's my preferred. But I actually have both. The JPI is in F and the Aspen is in C.

[Rick Junkin]

I use C for OAT and F for everything else. 0 is a good reference for icing and performance, and all of my engine limits are in F. If you're an "everything's in the green" kind of pilot the OAT is probably the only temp that you need to know the actual value.

Cheers,
Rick

[kpaul]

I'm in the both category.   JPI is in F and G5s shows C.

[ZuluZulu]

Another vote for both, except I seem to be the only one so far to have the JPI display in C and the PFD (G5) show F.

But as I’ve posted elsewhere on this site, the G5 OAT is reading 20°F hotter than the JPI and driving me crazy. 

[EricJ]

It really oughta be in Kelvin.