747-400 cabin heating/cooling question

[helimutt]

Having just flown to Florida and back on a XX 747-400 over the last couple days,can anyone explain, in simple terms, how the hell the back of the cabin was roasting hot, stuck on the ground at London before departure then even in the cruise it didn't cool that much. Same happened on return but stayed hot all the way back in the cruise too!. (didn't even need a blanket whilst trying to get shuteye). The forward cabin areas were much cooler. Complained to the steward and he said he'd go see if it could be adjusted. The stewards/esses were sweating.
Not impressed, I have to say, but is the system broken up into cabin areas? Why was the back so hot and not the next forward cabin section?

[wiggy]

It's a perennial problem with the BA 400's I'm afraid, don't know if other operators have the same problem but it's always seemed to be that on the ground the aircraft's own A/C set up on the 400 is particularly gutless and the ground conditioned air at Heathrow T5, if used instead of the aircraft packs isn't particularly great either.

Possibly it's all down to a general fore to aft flow of air through the aircraft plus the considerable amount of heat generated by the Inflight Entertainment System and lights, plus the heat generated by the passengers themselves as they move around during boarding. Certainly once the rear zones (compartments) get hot on the ground there's little we can do to cool them down until we get airborne. Once airborne in the cruise the temperatures in each zone can be controlled individually and should be easier to control. In extreme cases of zones being hot in the cruise we can increase the flow of air through the system temporarily to drive the Cabin temperature down to more comfortable levels...

[BelArgUSA]

I do not know the A/C differences between 747 Classics and 747-400s...
And yes, I know that bringing temperature to please everyone is not easy.
A few pointers, with my experience of 747 or other planes...
xxx
(1) A cold-soaked cabin is difficult (impossible) to bring back to acceptable (warmer) level.
(2) A 747 cabin can be cooled (to freezing) using 3 packs, but uses extra fuel.
(3) To save fuel, generally 2 packs only are used. Does not cool as well.
(4) To bring temperature down (daytime) close all window shades on sun side.
(5) To keep temperature up (night) close ALL shades, especially with few people aboard.
(6) Each human body produces the equivalent heat of a 100 watt light bulb.
(7) Cabin zone temperature (in the old 747) can be difficult to control.
(8) Cooling cabin of a plane parked long time in the sun is not easy. Close ALL shades.
xxx
In the old days, we were told to keep 68ºF (20ºC) in the cabin, later became 70ºF, then 72ºF, and now even to 75ºF, especially when passengers are asleep at night. This is obviously because of fuel economy.
xxx
There are passenger regional differences too. North American and North/West Europeans seem to prefer cooler temperatures, whereas South Americans, Africans or South Asians do not mind a couple of degrees higher. I am certain there may be differences of company policies depending where the airline is from.
xxx
A confidence...
With PanAm, we had a "cabin temperature adjustment" knob in the cabin for flight attendants to regulate the temperature + / - 2 degrees... I was told (later) that the knob was "NOT WIRED" to anything. It was a flight attendant "pacifier", so to avoid their frequent visits to the flight deck to ask the flight engineer to adjust cabin temperature. Makes me laugh. Keeps Suzy happy.
xxx
Wait until our cabin attendant friends read about that...!
:rolleyes:
Happy contrails

[gas path]

It's a perennial problem with the BA 400's I'm afraid,


Actually it's a general problem with the 744 no matter the operator. As previously pointed out the IFE system is the major contributor. Coupled to that a/c that are generally full of pax. generating their own heat can leave the system really struggling to get the temperature under control. This is especially so at the back of the cabin.

Even in the winter, plugging in external power, turning on the cabin lighting and 'firing' up the IFE can get the cabin to 30 deg C in a very short space of time.:8

[overstress]

It's often hotter on the flight deck than in E zone (the cheap seats at the back)

We normally run all 3 packs. Recently, advice has been given to start to cool the cabins a little more at about 40mins to landing, especially if the destination is a hot one. This helps to keep the cabin cooler during the turnround.

Helimutt, you would find the same problem on anyone's -400s, so perhaps you'd better go caravanning or boating at home next year ;)

[helimutt]

Title edited to protect the innocent.

As for caravanning or boating next year, I guess the company I work for wouldn't sign off my LPC/OPC in a caravan or in a boat. Difficult to practice holds, ILS's, NDB's and tail rotor failures etc etc in a caravan!! ;)

Anyway, thanks for the replies.:ok:

[RotaryPilotUK]

Helimutt, you would find the same problem on anyone's -400s, so perhaps you'd better go caravanning or boating at home next year

I haven't personally found that to be the case.

Why do you need air conditioning when the air is -35C outside? Isn't all the fresh air being filtered into the cabin being compressed and heated first? Surely it just needs to be heated less, not actively cooled.

I find one of the major contributors to the problem to be when an aircraft hasn't been configured with the over-seat air vents. The first thing I do when I get to my seat is reach up and open the air fully and adjust the direction. If I don't have that I find it gets intolerably hot and stuffy very quickly.

[wiggy]

Even on the 744 there shouldn't be a problem if the OAT is -35C.... but the original post was about the aircraft getting hot/being hot on the ground, where OAT's of 20 or above can cause the system to struggle.


Agree with your comments about the overhead vents - do any 744 operators have them or where they never a Boeing option?

[RotaryPilotUK]

Actually he said it didn't cool off much in the cruise, and was hot all the way back as well.

It's also my experience of said airline that their aircraft are often excessively hot.

[tom775257]

Rotary,

In fact in the cruise (at least on the aircraft I fly), the air comes straight out of the engines compressor section, through an ozone filter, then through heat exchanger(s) with a variable flow of cold ram air across it to cool the air, then onwards towards a central manifold; aiming for the lowest required temperature on the aircraft. Then the air to the different zones are warmed up to the required temp using some of the hot air (trim air) which is tapped off and hasn't gone through the heat exchangers to cool.

The air cycle machine (ACM) comes into play when nearer the ground / on the ground (the 'being compressed/heated then cooled' device I assume you are talking about), a device which cools the air (with the help of another heat exchanger and a fan to draw air across said heat exchanger). I am sure ACM operation will be covered on this forum somewhere. Somewhat tricky to get your head around to begin with.

Regards.

[NSEU]

It's also my experience of said airline that their aircraft are often excessively hot.

At the risk of repeating... It's not exclusive to BA.

Unfortunately, passengers are no longer content to read a book or watch a movie shown on a cabin wall. Now, everyone wants their own video screens and movie/game machine, so basically, a large electronic box has to be put under each group of 2~3 seats to control/process the video. These probably generate as much heat as an average laptop computer. Even the LCD screen generates heat because of the backlighting.

The overhead air vents can be a relief. The air source for these on the 747-400 is simply the air in the roof (above the cabin ceiling), which often can be quite hot on the ground. However, the air is moving, so cools the skin through evaporation. Yes, many Boeings do have vents (including 747-400's), but it is a customer option.

[Flight Detent]

I'll run thru this just one more time...

"744" is another way of saying "747 with no flight engineer", and these problems are only just another consequence of the fact that nobody on board really knows how things work!

Boy...will people ever understand.....

This is a consequence of the "modern" airplane, get used to it!

Cheers...FD...:ugh:

[Old Fella]

Have to agree with Flight Detent. One of the numerous "consequences" of not having a professional flight engineer up front is that passenger comfort can suffer. This aspect is not a "high priority item" with some pilots, and this is not a criticism of the pilots. No flight engineer could reasonably claim to be able to monitor systems closer than does a computer, but a computer only knows how to react to those situations for which it has been programmed. F/E's on the other hand are able to independently assess many situations and work through them in concert with the pilots. Just have a look at the MEL for a Classic as compared to a -400. Bring back the F/E!!!