I guess I was just surprised to hear that the air pressure from the air conditioning carts is enough to cool the plane without needing the fans on all of the time. I thought (like normal AC units in a house or car) that the air would need "pushed" through the plane somehow. I didn't know it could go straight into the manifold and find its way around. Very interesting indeed!
Some ground supplies are better than others to be sure M28. For us, humidity makes a huge difference on how effective PCA units are, either that or all the ones back east are knackered. When off stand, air at the pack inlets gets 'pushed' through the packs and beyond by some pretty big fans hanging off the wings.
I'm working for a Middle East operator. Ground conditioned air is hit and miss out here, despite the ridiculous summer temperatures, so we generally run from the APU unless we can get a really good ground unit. There's still only so much you can do when it's pushing 50C outside though
My hat's off to you Otto! An older friend used to fly that region in the 1970s and 1980s and he often remarked at the profound disparities between place to place. He also said on flights to places like Djibouti, livestock would sometimes be roaming the aisles in the back!