air temp questions at certain altitudes.

midcap

midcap

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midcap
I have only been on GA planes that had air conditioning installed. I was curious as to what temps you can expect in the cockpit at different altitudes when the ground temps are in the 90's.

Keep in mind, I am not talking about 30,000 feet ASL, more like 2000 - 10,000 ft asl
 
Its 3.5 degrees F for every 1000 feet. So if it is 100F on the ground in Phoenix it is 65F at 10,000'.

Airconditioning in an airplane "fly higher". Although when taxiing on the ground in 100 degrees Im sure its nice to have.
 
But if you believe the International Standard Atmosphere, it's 59 deg F at the north pole in the middle of winter.

It is what it is. I find the lapse rates are usually a lot less than ISA on a good-weather day.
 
I've seen ground temps in low-to-mid 90s, fall to 58-65° at 9000-10,000 msl. Feels great! If you're hot, climb . . .
 
Also depending on the aircraft, cockpit temp could be significantly higher than OAT. Even with vents, aircraft with big windows or canopies can make it like a greenhouse.

Yesterday is was just below freezing at altitude and inside the cabin it was around 65 degrees with the heat off.
 
Velocity173 said:
Also depending on the aircraft, cockpit temp could be significantly higher than OAT. Even with vents, aircraft with big windows or canopies can make it like a greenhouse.

Yesterday is was just below freezing at altitude and inside the cabin it was around 65 degrees with the heat off.
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I see, as long as it isn't in the 80's that should be ok. I would imagine in somthing like a Cherokee Six, you could add it to the plane down the road.
 
Velocity173 said:
Also depending on the aircraft, cockpit temp could be significantly higher than OAT. Even with vents, aircraft with big windows or canopies can make it like a greenhouse.
Yesterday is was just below freezing at altitude and inside the cabin it was around 65 degrees with the heat off.
Click to expand...
True, the sun (especially at altitude) can screw with your cabin temperature easily.
At 10,000' last time, it was 0C and I was baking. I had to put a sweater over my legs because the sun was burning my jeans up.

Also, to answer the altitude temperature question: yes, climb for cooler air. In southern states, the lapse rate is often MUCH higher than 3.5F per 1,000' due to the hotter sun and worse daytime heating. So I can take off in 110F at 600' MSL and see 10C at 9,500'.
A great tool for seeing how cool the air will be at what altitudes is the winds aloft forecast which includes the temperature in the forecast as well. Use your FF, ADDS webpage or whatever tool you prefer.
 
coloradobluesky said:
Its 3.5 degrees F for every 1000 feet. So if it is 100F on the ground in Phoenix it is 65F at 10,000'.

Airconditioning in an airplane "fly higher". Although when taxiing on the ground in 100 degrees Im sure its nice to have.
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No problems here at 100* plus ... but then, I just open the canopy and let the prop wash keep things cool :cool:
 
BigBadLou said:
True, the sun (especially at altitude) can screw with your cabin temperature easily.
At 10,000' last time, it was 0C and I was baking. I had to put a sweater over my legs because the sun was burning my jeans up.

Also, to answer the altitude temperature question: yes, climb for cooler air. In southern states, the lapse rate is often MUCH higher than 3.5F per 1,000' due to the hotter sun and worse daytime heating. So I can take off in 110F at 600' MSL and see 10C at 9,500'.
A great tool for seeing how cool the air will be at what altitudes is the winds aloft forecast which includes the temperature in the forecast as well. Use your FF, ADDS webpage or whatever tool you prefer.
Click to expand...

very cool, thanks for the info. I did not realize how much cooler it is up there than down on the ground.
 
midcap said:
very cool, thanks for the info. I did not realize how much cooler it is up there than down on the ground.
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There is a term that meteorologists use for the warm "cushion" of air by the ground, I forget it. I've stumbled upon it while studying Skew-T charts so if I see those articles again somewhere, I'll make sure to memorize the word and post it here.
 
BigBadLou said:
There is a term that meteorologists use for the warm "cushion" of air by the ground, I forget it. I've stumbled upon it while studying Skew-T charts so if I see those articles again somewhere, I'll make sure to memorize the word and post it here.
Click to expand...
Planetary Boundary Layer? (PBL)
 
Standard lapse rates are theory. The difference between theory and practice is that, in theory, they are the same.

I once descended 3,000 feet out of sunshine and 32degF air, hit the cloud tops and the temp was 32degF. This after recently getting my instrument rating, and telling my wife confidently that we didn't have to worry about ice because the air would warm up on the descent. Fortunately Approach got me though the freezing layer fairly quickly.
 
Velocity173 said:
Also depending on the aircraft, cockpit temp could be significantly higher than OAT. Even with vents, aircraft with big windows or canopies can make it like a greenhouse.

Yesterday is was just below freezing at altitude and inside the cabin it was around 65 degrees with the heat off.
Click to expand...

Wish my Luscombe retained heat like that, this time of year lol
 
One hot summer afternoon crossing into Tennessee, I told ATC I wanted to climb to get some cooler temperatures. I was authorized a climb to 70 degrees and to let him know what altitude that ended up being.
 
If it is in the 90s or even 100s on the ground there very often is a greater-than-normal lapse rate near surface, meaning temps fall off faster as you climb. The caveat is that the greater the lapse rate the more unstable the air is and the more likely there is to be building cumulus/t-storms around.

Foreflight's winds aloft page highlights altitudes with greater-than-normal lapse rates as a sort of warning about unstable air.
 
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