(You turn them on from the FMC). Obviously one of them is a power generator. Another one has a big flexible tube, so I would guess that it is used to empty the lavatories. So what is the third one for? henri

You can read that in FMC...Air conditioning unit, ground power and air start unit Lj. Prodanovic

one thing you have missing is your last name

One is the Ground Power Unit, which provides the 115 VAC 400Hz...Looks like a Hobart to me. One is the Air Conditioning Unit, which provides conditioned air directly to the aircraft manifolds. One is the Air Start unit, which provides 150-200 ppm of air at around 30-50 psi. Used to pressurize the bleed air system and utilize it for starting the aircraft's engine w/o the use on an APU. No Lav cart unfortunately. Both the Air Start and Conditioned Air units look to me like Coldbusters...which typically aren't used for air starts or as air conditioners (they only provide heated air) http://www.spencer-manufacturing.com/products-coldbuster-mark4.html...which is sorta disappointing.

I believe one of their videos had people loading the plane. I cant find that though, is it a separate add-on? Also, I work the ramp at KPIA and all our air start carts (work on our ERJ-145s all the way up the good ole MD-80) air air bottles full of compressed air. Is the air starter shown in this video just like a giant air compressor? Would be nice to have if so, those air bottles are heavy!

This is one airstart i fixed up last summer. Call 'em "Huffer Carts". Don't have to play around with tanks/bottles with these babies. Give me a shout! I got a convince the boss to put a couple for sale! I 'think' the airstart shown in the sim isn't actually an actual airstart unit at all, but like a mentioned above...actually a Coldbuster. It uses engine coolant and some of the newer ones exhaust as well and ducts air into a giant fan coupled to an engine with a centrifugal clutch...it moves a lot of air but doesn't provide enough to start an engine.