What is the average & max temperature of an airplane cargo hold?

Question

I want to take some chocolates to offer in my luggage. Chocolates are a bit sensitive to heat, though. What is the average temperature inside a cargo hold? 'Average by' itself can be misleading. What is the max temperature there?

I don't know much about airplane mechanics but I assume they have some cooling systems like any other engine. Such systems, depending on where they are placed, might influence temperature in the cargo hold. I also fear temperatures in the ground while exterior temperatures are higher, and luggage is being put inside. What are max temperatures near the airplane in such situation?

Answer 1

The cargo hold of a modern jet aircraft is pressurised and air conditioned just like the passenger cabin to minimise internal stress. Air is sucked in by the APU (on the ground) or engines (during flight), bled off and cooled by the air conditioning units (PAKs) and pumped into the fuselage. A release valve usually located at the rear of the plane allows air to vent, thus fresh air is continuously pumped in and cooled, while old air escapes via the relief valve, creating a circulating atmosphere of breathable air conditioned air inside the aircraft.

Your chocolates will generally be fine while inside the cabin or cargo hold. Of course, you should take into consideration that while your luggage is on the tarmac or being transferred it may be subject to the elements and outside air temperature. A beg left sitting on a trolly in the sun on a hot day can warm up very quickly.

On a final note, some aircraft designs have the PAKs (air conditioning units) located next to or around the cargo holds. On a very hot day, if the aircraft is sitting around for a while, the PAKs themselves can get quite hot, and that heat can transfer into nearby areas such as the hold where your chocolates are sitting. However, there is no equivalent to a car's radiator in a passenger jet.

The safest bet is to take the chocolates (or anything that can melt) as on board luggage. Just don't eat them on the way!

Answer 2

Running a datalogger inside a checked suitcase between Paris and Sydney via Dubai showed the minimum temperature to be 13 degrees Celsius. That occurred in the last 3 hours of flight. A change of aircraft at Dubai showed the temperature rise to 28.5 degrees Celsius, when it changed aircraft, and then slowly drop as the Sydney bound aircraft proceeded on its flight. Temperature and humidity were logged every 15 seconds. The datalogger was a recorder and not a transmitter. Transmitter equipment aboard aircraft is illegal. I am yet to marry data from the recorder against actual flight data available online, but aircraft typically travel at around 38000 feet, with an outside temperature of around minus 44.6 degrees Celsius. The datalogger was placed against the side of the suitcase in a side pocket. The suitcases position within both cargo holds was unknown.

Answer 3

As indicated in the answer of this question - 'Will my checked luggage freeze in the airplane?', the luggage hold can get down to 7C. So while your chocolates may be chilled, they're unlikely to overheat.

Indeed, I've taken chocolate many times, as has the commenter and asker of that other question, and have had no problems.

MAXIMUM temperature, however, would depend on the ground temperature outside the plane. If it's super hot outside, and the cargo isn't as well insulated as the passenger deck, the temperature may increase, especially on cargo close to the outside.

Once in the air, or in a colder area, the rate at which it cools will be dictated by Newton's Law of Cooling.