4 ms·

Hrm. Wonder if the high temps were because the plane was only running its APU (auxiliary power unit - a small, non-thrust-producing turbine) (to conserve fuel,

Hrm. Wonder if the high temps were because the plane was only running its APU (auxiliary power unit - a small, non-thrust-producing turbine) (to conserve fuel, presumably), and so was unable to provide HVAC to the main cabin. FlightAware says Delta 555 is usually served by a B757-200, not sure how the HVAC is laid out there, but given the power draw of HVAC systems, seems unlikely that just an APU can provide enough power to deal with 111°F (and likely higher, since the plane was on a nice hot tarmac, with heat reflection not helping matters any). It would be interesting to know if the pilots were aware of the conditions, requested guidance from the company, and were told to conserve fuel. (This os pure speculation on my part).

hotpotamus 3y ago
My assumption has been that planes mostly don't have air conditioning. I was stuck on the ground due to technical issues once and so they brought in an air conditioning truck to keep things comfortable (this was in South Texas). I thought they brought in bleed air from somewhere in the engine which would be pretty cool at altitude. I'm sure someone who actually knows about airplanes could chime in and correct me.
myself248 3y ago
I'm no pilot, but my understanding is that airplane HVAC is driven by pressurized air from compressor bleed (running through a device that manipulates pressure and thus temperature, through various heat exchangers, to produce heat or cooling as needed), and doesn't run at all from the APU. Cool air on the ground is from a duct under the jetway. Once they push back, they're basically unconditioned until the main engines are at power.
nocoiner 3y ago
I don’t know if my bias is affected by the last half dozen or so flights I’ve been on during this unseasonably hot last few months, but it seems to me like temperature regulation on planes on the ground is way more unpleasant than it used to be. My recollection is that, occasionally, there’d be a problem keeping the plane cool, and they’d ask you to power the shades and open the A/C vent (and this was generally in places like Phoenix or Vegas, so, understandable). Now I feel like this is the case on every hot weather flight, regardless of airline, even in fairly temperate climates. I don’t know if this is a cost cutting thing, a function of modern aircraft design, or something I’ve hallucinated, but my strong impression is that the airlines have somehow managed to make sitting on the ground in a plane even more unpleasant than it used to be.

hotpotamus 3y ago

My assumption has been that planes mostly don't have air conditioning. I was stuck on the ground due to technical issues once and so they brought in an air conditioning truck to keep things comfortable (this was in South Texas). I thought they brought in bleed air from somewhere in the engine which would be pretty cool at altitude. I'm sure someone who actually knows about airplanes could chime in and correct me.

myself248 3y ago

I'm no pilot, but my understanding is that airplane HVAC is driven by pressurized air from compressor bleed (running through a device that manipulates pressure and thus temperature, through various heat exchangers, to produce heat or cooling as needed), and doesn't run at all from the APU. Cool air on the ground is from a duct under the jetway. Once they push back, they're basically unconditioned until the main engines are at power.

nocoiner 3y ago

I don’t know if my bias is affected by the last half dozen or so flights I’ve been on during this unseasonably hot last few months, but it seems to me like temperature regulation on planes on the ground is way more unpleasant than it used to be. My recollection is that, occasionally, there’d be a problem keeping the plane cool, and they’d ask you to power the shades and open the A/C vent (and this was generally in places like Phoenix or Vegas, so, understandable). Now I feel like this is the case on every hot weather flight, regardless of airline, even in fairly temperate climates. I don’t know if this is a cost cutting thing, a function of modern aircraft design, or something I’ve hallucinated, but my strong impression is that the airlines have somehow managed to make sitting on the ground in a plane even more unpleasant than it used to be.