B738 vs A332 hold temperature

[AvGus]

Hi All,

Longtime listener, sometime poster.. Can anyone tell me what differences (if any) there are in the way the hold is heated and cooled between a) the forward hold of the B738 and b) the aft bulk compartment of the A332. These being the two holds that AVIs are usually accommodated in on these two aircraft types. I am a veterinarian (and onetime PPL) and I see quite a few pets who travel by air so I'm just trying to extend my professional knowledge of what the climatic conditions are in the hold and the B738 and A332 are the main two types operated by our local airlines. As I understand it the holds are heated/cooled by 'second hand' air from the passenger cabin through use of various fans and valves but I haven't got further than that...

Thanks.

[Hinkler]

I think you have the gist of it. If you go through the systems in the aircraft flight manuals it gets kind of complicated as to when various valves open or fans operate and doesn't really add much to a practical knowledge of the systems. I have only flown larger Boeings and the A380 where cargo compartment temperatures are selected and monitored from the flight deck, I suspect it is similar for the 737 and A330 although it is possible that there may also be some manufacturer options taken up by different airlines.

PS - I'm also a veterinarian (turned airline pilot), so tend to take an interest in livestock when we carry it.

[AvGus]

Thanks Hinkler! Can I ask; is there a specified temperature that you are required to select for dog/cat AVIs in the hold? And if say it was a hot day and you saw that the dog/cat hold temperature after closing cargo doors was 'hotter than normal' would you knock the selected temperature down a few degrees to make it cool down quicker or would this not make any difference? And another one, do you get a read out of just temperature or is there a relative humidity indication as well?

I once intended to take your path but ultimately flew nothing more complex than a C172, how long were you in the vet world for?

Cheers.

[Hinkler]

I think you will find there is significant variation in procedures between airlines and operating environments.

On the ground we tend to see higher cargo compartment temperatures if it is hot outside, particularly if the APU is shutdown for a turn around. Ground air does not tend to be very effective for cooling the cabin let alone the cargo areas. Once the cargo doors are closed and engines (or at least APU) running, then temperatures become more manageable. Once at altitude, then warming becomes more of an issue. Crews will monitor temperature and adjust accordingly. Some aircraft have a humidifier for the flight deck, but I'm not aware of any with one fitted for cargo bays nor any humidity indicators.

Typical cargo temperature settings are around 18-21 deg C when livestock is carried.

. . . and still doing smallies locums between trips.

[AvGus]

Awesome, thanks for explaining! All makes good sense.

Cheers.

[Matey]

There is no specific temperature control for the forward cargo hold on the 737. Recirculated air from the passenger compartment is fed through the hold, and that air is at the temperature selected for the passenger cabin. In addition , warm air from the equipment cooling system is also fed to the forward cargo compartment which is where AVI are carried.

[AvGus]

Thanks for your reply here Matey! Is there a means of controlling the 'mix' of cabin air (cool) and the air from the avionics bay (warm)? Or do these these just each blow into the fwd hold at a constant rate?


Cheer!