Well, AFAIK, the water system is able to be pressurised by the external air coming from the cart, excuse me if that is wrong, It's been a while since I've actually flown the 737 IRL so don't hold that to me but I'm 99.99999999999999999999999% sure, I'm sure Simon can correct me if I'm wrong. I see Simon that yee fly both the classics and NGs at your company, you wouldn't happen to have an electronic copy of the differences hand out you got during your training would you? I've been looking all around the internet for one but just can't lay my hands on it, it'd be really appreciated if you could e-mail one to me as I was going through the FCTM and FCOM for the NG and almost everything is the same or very close to the old classics, If I could just get the differences course it'd save me a load of time. If ya have it, could you drop me a PM and I'll give you my email address. Thanks in advanceRónán.

Hi Ronan (I can't do the inflections/things above your name, sorry!) 100% correct - a ground air source will pressurise the ducts necessary for providing water pressure. Practically speaking for us though, the only time we'll ever use an external air cart is if our APU is unserviceable and then only for starting the #1 engine and nothing else. It's a strange local habit. Ground air carts (generically called 'Copco's' for some reason here, probably due to some dominating company that made them) seem to sometimes be in short supply, so they tend to only be available for the few minutes you need to start one engine before being spirited away to the Ground Air Cart pasture or something. It is odd, although the ones we have here are incredibly noisy (are they all like that?) and they get placed almost right next to my window, so I don't really want them around anyway. Regarding the differences list....for our technical course on the -800, we actually did a full technical (a week in the classroom) with the engineer who presented the lectures highlighting differences during the presentation of each system. I've had a look for an electronic summarised differences list, but I think the only one we got was on paper (and wasn't really a plain differences list, more a systems 'summary' in any case), and I don't have the original file of that....I'll see what I can find but I'm not sure I can help here, sorry!

Ground air carts (generically called 'Copco's' for some reason here, probably due to some dominating company that made them) seem to sometimes be in short supply, so they tend to only be available for the few minutes you need to start one engine before being spirited away to the Ground Air Cart pasture or something.

I'd be willing to bet it's money driven. They have to have enough to go around, cover maintenance costs, find someone to get the cart out there & then there's the question of exactly which budget covers fuel costs on them. That's pure speculation but in my line of work (refineries & chemical plants) 99.9% of strange situations are due to the almighty dollar. (not so mighty lately, I know...)

He he he something's afoot...

and it's Not a Hand !!A contract for his autobiography !!!

Hi Ronan (I can't do the inflections/things above your name, sorry!) 100% correct - a ground air source will pressurise the ducts necessary for providing water pressure. Practically speaking for us though, the only time we'll ever use an external air cart is if our APU is unserviceable and then only for starting the #1 engine and nothing else. It's a strange local habit. Ground air carts (generically called 'Copco's' for some reason here, probably due to some dominating company that made them) seem to sometimes be in short supply, so they tend to only be available for the few minutes you need to start one engine before being spirited away to the Ground Air Cart pasture or something. It is odd, although the ones we have here are incredibly noisy (are they all like that?) and they get placed almost right next to my window, so I don't really want them around anyway.

Well, as a bit of a start cart expert (*harumph harumph*)...yes they are all quite noisy. Up here we call 'em "huffer carts" The one's I've played with are basically APU's on a cart - mores specifically GTCP 85's with a couple different variants depending on the cart (ie: some carts are AC PWR/Air combined...position of the tangental burner can...etc.) Nice thing about these is you can run standard diesel in em and typically run an AC pack or two = saving fuel/cycles on the APU They are basically identical to the Original 37's APU's and pretty similar to the GTCP 36's that equip some of the 3/4/5's so you can imagine how loud the thing is with very little sound insulation and exhaust piped right upward no doubt to your window! hehe Other's use a typical internal combustion engine which drives a compressor and stores pressure in a tank. They are noticeably quieter and if you're smart with em you can charge up the tank and shut the unit off just before you wheel em up to the aircraft for a start. A nice valve regulates flow and pressure and you should have enough stink in the tank to get one engine going. I don't know why there's a reluctance to use start carts/ground air sources...at least where I am anyways. I have a heck of a time convincing pilots and AME's alike that a APU on a cart fartin' and burping' and makin' a whole lot of noise is perfectly safe and efficient. The hoses and couplings for such things are pretty straight-forward and the use of em is equally simple with the right training...but there's a host of issues some ground handler's have playing around engines and such so I think they just rather let the pilots do it..hehe. Don't know if it's in you MEL but check out if a Start Valve is inop what is your procedures....The manual start valve handle looks like great fun for a rampie....

Just want to add my thanks for all this hard work Simon - really helpful, really well written, really fun to read.

Hi Simon, Just wanted to ask if you flew MN466 on the 27th of August?It was on ZWO. Best regards, Greg

Hi Ronan (I can't do the inflections/things above your name, sorry!) 100% correct - a ground air source will pressurise the ducts necessary for providing water pressure. Practically speaking for us though, the only time we'll ever use an external air cart is if our APU is unserviceable and then only for starting the #1 engine and nothing else. It's a strange local habit. Ground air carts (generically called 'Copco's' for some reason here, probably due to some dominating company that made them) seem to sometimes be in short supply, so they tend to only be available for the few minutes you need to start one engine before being spirited away to the Ground Air Cart pasture or something. It is odd, although the ones we have here are incredibly noisy (are they all like that?) and they get placed almost right next to my window, so I don't really want them around anyway. Regarding the differences list....for our technical course on the -800, we actually did a full technical (a week in the classroom) with the engineer who presented the lectures highlighting differences during the presentation of each system. I've had a look for an electronic summarised differences list, but I think the only one we got was on paper (and wasn't really a plain differences list, more a systems 'summary' in any case), and I don't have the original file of that....I'll see what I can find but I'm not sure I can help here, sorry!

Alright, no bother then. Ground carts can be noisy, especially the older ones, newer ones can be quiet[er] but you'd not get to sleep with one in room if ya catch my drift. We've got a neat new thing in our new terminal 2 at DUB, where the ground and air supplys are built into the ramp. No noise ! In my company though, unless there is no GPU available then we have a policy of only starting the APU 5 mins before expected push-back time. Most airports we operate into have strict fines for the use of the APU when it's not required due to the availability of GPU's.

Simon, thank you so much for your input in this thread.I love real world ops and I have a pad of paper and pen every time I visit this thread. I'm only through page 2 but wanted to post my "thank you." Back to page 2 and reading all this fantastic stuff!

I don't know why there's a reluctance to use start carts/ground air sources...at least where I am anyways. I have a heck of a time convincing pilots and AME's alike that a APU on a cart fartin' and burping' and makin' a whole lot of noise is perfectly safe and efficient.

In my company it's normal operating procedure not to start engines on stand, only during the push, It's only allowed on special occasions [when things don't work right] with reference to the company procedure manual, and in co-ordination with a ground engineer...

Hi Simon, Just wanted to ask if you flew MN466 on the 27th of August?It was on ZWO. Best regards, Greg

Not guilty I'm afraid!

Not guilty I'm afraid!

Probably a good thing. For me to note a particular flight it generally has to be an unusually rough landing

Not guilty I'm afraid!

No problem lol :) I was on-board & I thought you might have been upfront.I fly out of Lanseria regularly though & it really is a great place to fly to & from. & Thanks so much for all the info in this thread! Brilliant stuff! Cheers

I see Simon that yee fly both the classics and NGs at your company, you wouldn't happen to have an electronic copy of the differences hand out you got during your training would you? I've been looking all around the internet for one but just can't lay my hands on it, it'd be really appreciated if you could e-mail one to me as I was going through the FCTM and FCOM for the NG and almost everything is the same or very close to the old classics, If I could just get the differences course it'd save me a load of time. If ya have it, could you drop me a PM and I'll give you my email address. Thanks in advanceRónán.

Out of interest actually, is there another pilot here who operates both classics and NGs and has an electronic form of the differences document? Perhaps from Southwest or Air Berlin? Would really be appreciated. Rónán.

I may be totally out of my depth here, but I was under the impression (or maybe this is just a US thing) that ground air conditioning and air starters were two separate connections. During the summer here there are usually large diameter yellow hoses hooked up to aircraft at the gate coming from a unit on the jetway (I believe) to supply low pressure cold air for the exclusive purpose of cooling. I was under the impression that a start cart provided high pressure, unconditioned air to the bleed duct side of the system which could be used for the starters or running the packs, the latter providing the same function as preconditioned air. http://www.b737.org.uk/airconditioning.htm#Schematics The above schematic references two connections as I described, one for "ground air" and one for "ground pneumatic source." Now, the really burning question here: will the low pressure air from the jetway hose provide enough pressure to the potable water tanks to make coffee?

You're completely right Lee...there are two separate connections. The water is pressurized from the bleed pneumatic source... that is the pneumatic manifold that consists of bleed air from the APU, engines, and "Ground Pneumatic Source". The conditioned air connection is the big 9-12 inch yellow hose that connects directly to the cabin air mix manifold...that is ducted straight to all the cabin ducts...etc... The "Ground Pneumatic Source"/air start/"huffer cart" connections though can be used if the volume/pressure enough to operate an air conditioning pack or two...so you can pressurize your water/cool the cabin/whatever. However these carts are pretty rare as I mentioned above as most are a stored-charged type air start which are made for an air start only...not like the turbine units on a cart which can be used as any APU My toys :)