Cabin Temperatures

[williamjobeth]

Hi There,

I am a design engineer working on a product that is used in commercial airliners like the 747, 777, and 787. It is plastic and gets installed in the floors near the passenger seats.

My questions are:
1. What are the normal ambient temperatures / humidity levels inside the passenger cabin.

2. When an aiprlane is sitting on the tarmac for awhile or out of service for a few days, what are the temperatures / humidity levels inside the passenger cabin in these situations.

3. As you probabley are aware, the inside of an automobile can reach very high temperatures when parked at the mall on a summer day. I have been told that the temperature here can be 150 F in about 30 minutes. What about in a closed up passenger cabin of a 777?

Any information is appreaciated.

[NSEU]

This is a bit like asking how long is a piece of string. I'm not sure what the limits are for the cabin zone temperature indications, but 47C is not unheard of in an Australian summer on a 744 EICAS screen. It doesn't take long for the temperatures to rise with all the lights and video systems turned on and the packs off. The hottest place would either be in the crew rest above the toilets in the aft zone or in the cockpit (lots of glass and lots of lights), but there are no plastic floor strips there. In the cabin, the temps can go from high teens in flight to 40+ in 30 minutes to an hour if the packs are turned off straight away. Fortunately, the window area is generally small in the cabin (although I hear the 787 windows will be larger), so you won't get as much radiant heat as in a car. You also have an air gap between the outer glass and the inner window for insulation.

These plastic strips are a pet hate of mine. They are always coming out of the floor tracks (the cleaners routinely dislodge these with their vacuum cleaners). The plastic is almost impossible to cut to size with normal hand tools. The strips are difficult to insert into the floor tracks, especially if the insertion part has been dramatically cut to allow for wiring and chair leg tie downs. This leads to the eventual breakage of the insertion part.
Also, the strips are not always high enough to go above the carpet and some of the larger video harnesses (but I guess you have to weigh this against the pax tripping over them).
Not being able to see the insertion part when you're putting the tracks down makes it difficult to find the floor track. If you are having trouble getting a track down, you don't know whether to apply more pressure (with a size 12 boot) or keep fiddling around with them (trial and error), more gently, for long periods of time.

Humidity levels would only be high on the ground with lots of people on board (with the packs off). Or if the aircraft is parked in tropic regions with the doors open... Just check the weather charts for places like Singapore I assume the strips have to resist 100% humidity (in the form of spilled coffee, etc)

Hope this helps.
Rgds.
NSEU

[BelArgUSA]

Hola William -
xxx
I can pass along some information as to how it goes in airliners.
But no specific numbers...
I am retired as pilot, and started my career as a flight engineer.
Therefore, I had to twist the knobs to regulate the cabin environment.
xxx
When I started with PanAm, we were instructed to select 68ºF (20ºC) as cabin temperature.
Later, that temperature was increased to 70º-72ºF bracket, for fuel economy reasons.
After PanAm's bankruptcy, went to work in South America, until retirement.
Temperature selectors were kept higher.
It appears that South Americans do not like to "freeze" as Anglo-Saxons do for comfort.
The standard was 22-23ºC for daytime flights, and more like 24º for night flights.
xxx
One thing to remember - it is a hell of a job to warm-up a cold-soaked airplane cabin.
Same thing for the opposite. Cooling a cabin is a difficult task.
Each human body produces as much heat as a 100 watts lightbulb.
Flown 747s with 500 bodies to cool-off...
And in a 747, we have "cabin zones control"... does not work too well.
We generally mark the best settings with grease pencils.
xxx
I have flown airplanes in Saudi Arabian seasonal contracts. Outside temperature 120ºF.
No need to tell you that the cabin temperature was similar to an oven.
And taken airplanes parked overnight at Chicago O'Hare in winter... takes 1 hour to warm-up.
xxx
If I can also pass this information, is about cabin air circulation on ground.
For flight attendants in particular...
In a 747, they are keen to open all 10 main deck cabin doors.
It achieves only one thing. Aeration between lateral door pairs. Not the cabin.
To aerate cabins, the best is to open only 2 doors.
One door (say on the LEFT side in front, and one door (on the RIGHT side) in the back. (L-1/R-5)
That ONLY aerates the cabin from front to back.
Finally, to keep a cabin cold (or warm), close ALL window shades.
xxx
A last word about cabin temperature controls.
With PanAm, we had some airplanes with a "cabin temperature" knob in the cabin.
Flight attendants could select "WARMER" or "COLDER", at their stations.
In technical training, we were informed (secret) that knobs were connected to NOTHING.
Knobs were just there to keep flight attendants happy. Psychological cooling.
And they would not come to the cockpit every 5 minutes to complain...
Makes me laugh...
xxx

Happy contrails

P.S. - You ask about humidity...?
Cabin air conditioning systems (air cycle) make cabins extremely dry.
Each person should drink a lot of water/liquids while on long flights.
No wonder these old flight attendant's cheeks are wrinkled...
I am... with my 40 years of airline career.