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Do aircraft engineers get a pass? > the Bombardier CRJ aircraft used on some shorter routes have a maximum operating temperature of 118 degrees. https://www.n

Do aircraft engineers get a pass? > the Bombardier CRJ aircraft used on some shorter routes have a maximum operating temperature of 118 degrees. https://www.npr.org/sections/thetwo-way/2017/06/20/533662790/its-too-hot-for-some-planes-to-fly-in-phoenix https://www.npr.org/sections/thetwo-way/2017/06/20/533662790...

FartyMcFarter 5y ago
Is that plane temperature, or air temperature in the shade? Probably the latter? In the case of Starlink's dish, it's not clear which temperature they mean.
t0mas88 5y ago
You may think this is a smart example, but you're mostly illustrating that you know nothing about aviation engineering. The temperature limit for takeoff performance has nothing to do with the maximum temperature for electronics or other components. It's about air density decreasing which reduces the engine thrust as well as the maximum lift from the wings. So the warmer it gets the lower the maximum weight you can take off with and the higher the speed required before lift-off. At some point that's not safe anymore so the manufacturers only publish verified performance data up to a maximum temperature. You can't legally fly above that.
- matheweis 5y ago
  I think this particular issue might not be related to the safe flight envelope, although that was the hot take at the time... I should have added more context. About a year or so after the article I linked above was published, Bombardier obtained ISA+40C certification for the CRJ700 and CRJ900 from both the FAA and TC. For the flights in and out of Phoenix, AZ, this meant that those aircraft have since been able to legally fly in temps of up to 123.8F. I don’t know the details of the certification upgrade, but my understanding is that there were no changes to either the aircraft or weight restrictions. I don’t personally know anyone at Bombardier to know exactly why they didn’t certify the aircraft for ISA+40C to begin with, but given that there were apparently no changes to either the aircraft or the weight restrictions, this seemed very much a case of “your engineering team had to wait ... to realize an item that's going to be outdoors in the sun is going to get hot”.
  - t0mas88 5y ago
    No. ISA+40 isn't a static temperature, it would be lower in Denver than at sea level. So in no way is that a warm electronics kind of problem. We use ISA differences (the +40 you wrote) in flight performance calculations specifically. Not in any "aircraft too warm / cold" kind of limits, since those would be absolute numbers not relative to ISA.

FartyMcFarter 5y ago

Is that plane temperature, or air temperature in the shade? Probably the latter? In the case of Starlink's dish, it's not clear which temperature they mean.

t0mas88 5y ago

You may think this is a smart example, but you're mostly illustrating that you know nothing about aviation engineering. The temperature limit for takeoff performance has nothing to do with the maximum temperature for electronics or other components. It's about air density decreasing which reduces the engine thrust as well as the maximum lift from the wings. So the warmer it gets the lower the maximum weight you can take off with and the higher the speed required before lift-off. At some point that's not safe anymore so the manufacturers only publish verified performance data up to a maximum temperature. You can't legally fly above that.

matheweis 5y ago
I think this particular issue might not be related to the safe flight envelope, although that was the hot take at the time... I should have added more context. About a year or so after the article I linked above was published, Bombardier obtained ISA+40C certification for the CRJ700 and CRJ900 from both the FAA and TC. For the flights in and out of Phoenix, AZ, this meant that those aircraft have since been able to legally fly in temps of up to 123.8F. I don’t know the details of the certification upgrade, but my understanding is that there were no changes to either the aircraft or weight restrictions. I don’t personally know anyone at Bombardier to know exactly why they didn’t certify the aircraft for ISA+40C to begin with, but given that there were apparently no changes to either the aircraft or the weight restrictions, this seemed very much a case of “your engineering team had to wait ... to realize an item that's going to be outdoors in the sun is going to get hot”.
- t0mas88 5y ago
  No. ISA+40 isn't a static temperature, it would be lower in Denver than at sea level. So in no way is that a warm electronics kind of problem. We use ISA differences (the +40 you wrote) in flight performance calculations specifically. Not in any "aircraft too warm / cold" kind of limits, since those would be absolute numbers not relative to ISA.