How high is the temperature in the cabin without air conditioning?

At high altitude, the environment outside the plane is low temperature and low pressure, about MINUS 50 degrees and 0.25 atmospheric pressure. If nothing is done, then the people on the plane are in a coma due to lack of oxygen and frozen into popsicles. Therefore, the cabin of the passenger plane needs to be pressurized to compress the air to the pressure that people can live. Modern aircraft jet engines have huge air compressors, so if high-pressure air is needed in the cabin, the most convenient way is to take it directly from the aircraft engine. Actually, that's what I did. The engine has a multi-stage compressor, which gradually compresses the inhaled air to high temperature and high pressure. If the engine room needs air, just take it directly from a compressor. However, due to the compressed air, the temperature of these compressed air is relatively high, so it needs to be cooled. Refrigeration on the plane does not use freon like household air conditioners, but depends directly on air. First, the high-pressure air from the engine can be cooled once by the surrounding cold air. After being cooled by external low-temperature air, the compressed air from the engine is compressed once by ACM. This process will raise the temperature to 250 degrees Celsius, and then be cooled by the cold air outside. The cooled air is used to drive the turbine, which will reduce the air pressure and cool the air at the same time. After doing this for a period of time, the temperature of the air can drop to MINUS 20 or 30 degrees. Cold air from ACM is mixed with hot air from the engine and ordinary air sucked from the cabin, so that the required temperature can be adjusted and the cabin can be kept cool. Back to the original question, if the plane is not pressurized at high altitude, then the passengers are deprived of oxygen+freeze to death; If you don't turn on the "air conditioner" (understood here as not using ACM), then everyone will think that the hot air from the engine will be cooked. However, it seems that this ACM can't be turned off. There are still several ACM sets on the plane, so don't worry.