Hi people,I'm interested in any tidbits of info RL 737 pilots are able to offer me (in fact, any large jet drivers) with respect to APU use. I recently saw something somewhere (I can't remember whether it was read or seen) in which Southwest Airlines were advising pilots not to run the APU before start to run the power, packs and pressurisation system, and it had saved them around $15 million a year in fuel (I think - this figure may be unreliable - I'm not priviy to RW figures, I just seem to remember this one)Obviously, prior to this, some different kind of standard procedure was in effect? I'm interested in the use of APU and ground cart for before-start bus power/bleed use.If you are not able/allowed to use the APU, do you always use ground power? Do you take an extra bit of fuel and try to fire up the engines early for bleed and get pre-flight checks done quickly? Would you use ground A/C packs for pax comfort at boarding in this instance?If you were using APU for a while, do you have to account for this in your fuel calcs? Ditto if not using APU i.e Do you have to take more fuel in order to use the engines for longer to provide ground power? Would you ever use the engines over APU before flight for this purpose? (I'm guessing not here due to various emission and NA SOP's)Do you use ground power a lot? Do all airports have it? (is that a really stupid question?) Is it always a cart or do some airports yet have jetway ground power hookups or similar?Whilst I'm always interested to hear from other simmers (who aren't also ATP certified) I'm really looking for any RW info if anyone has time to jot something down I'd be really grateful :smile:Many thanksbestjake

At Independence Air, they tried to limit APU power on the outbound to no more than 15 min (they closed up 6 years ago, so my memory is rusty on the details: 15 min-ish) prior to boarding. Robert may correct me on this, but basically, they wanted it on the minimum amount of time possible to cool/heat the plane prior to putting people on it. Granted, we're talking about a CRJ200 here, and they didn't have the A Gates at Dulles equipped with pre-conditioned air (PCA) to cool the plane during the turn. The Airbuses on the B Gates had PCA off of the jet bridges, but I didn't work with the 'buses.On the inbound, the responsibility was placed on the rampies to park it, chock it, and hit it with ground power as soon as humanly possible. Basically, this amounted to the crews coming in on one engine (if possible), with the APU turning. As soon as they stopped, it was engine off, beacon off, chocked, powered, and APU off (within 5 min was the goal, if I remember correctly).Keep in mind that IDE was a low cost carrier (LCC), just like Southwest, so what I wrote here is more indicative of that line. Other carriers may have had looser goals for aircraft conditioning purposes, but in the end I'd argue it's situational. Ground power being available is the biggest consideration. The rest could be the cabin temps related to the external air temperature, or a captain could think that the flicker of the light on the source switch looks bad, so he'll fire it up prior to boarding (even though it'll probably do it again on the APU -> EDG switch); or a captain wanted to be nice to the rampies and hit them with some cool air in the conditioned bins while they hump bags, so he'll fire it up a little early. Who knows...I'd be interested in hearing what other people know about other airline SOPs though.EDIT: I didn't fully read your questions, so here are the answers to the rest:If you are not able/allowed to use the APU, do you always use ground power?-Yes. Either with a diesel generator, or through a device that draws electrical from the airport's source.Do you take an extra bit of fuel and try to fire up the engines early for bleed and get pre-flight checks done quickly? Would you use ground A/C packs for pax comfort at boarding in this instance?-Above. It's situational, sometimes down to the crew.If you were using APU for a while, do you have to account for this in your fuel calcs?-Yes. Definitely. Dispatch will throw extra on there if they expect (or know) that the airport doesn't have reliable ground power, or none at all.Would you ever use the engines over APU before flight for this purpose?-You generally do not use the engines for GEN power, unless in really specific instances. You only really see engines turning for GEN power on smaller aircraft without APUs at all.Do you use ground power a lot? Do all airports have it? (is that a really stupid question?) Is it always a cart or do some airports yet have jetway ground power hookups or similar?-Most places you'd fly a 737 into are equipped to handle them, to include ground power. At least in the States, it's the exception to the rule to not have some sort of GPU anywhere you have actual gates (most places you'd send a 737 into). Furthermore, I'd argue most gates (jet bridges) have some sort of ground power and air hook up on them, but I know someone out there may know otherwise.EDIT2: Credentials:Ramp work at BCB, IAD, PHX, DVT - so, no I haven't flown for the majors, but I did all the ground work surrounding what you're talking about.

Edited February 21, 201214 yr by scandinavian13

90% of the time, we'll leave the APU off until about 10min prior to push/start. At some remote stations (eg. Deadhorse) we'll run it the whole time on the ground. We usually leave the APU off for taxi in, unless we're going to need it for heating, again excepting remote stations.

I am not a RW pilot but I fly a lot with SAS 737NG and they always start the APU just before the boarding is completed.On many airports it is forbidden to start the APU more than x min before, Example: http://fly-sea.com/charts/EKCH.pdf on page 3 it says quite clearly what the rules are. On other airports the rules might be different but they should be written on the charts.Manfred

Meh in Canada we just run 'em all the time. Burn baby burn. Yee haw oilsands *bang bang*.Kidding aside...I think a lot of it has to do with the location. Big city airports have ground power at the gate the majority of the time. In Canada, pre-conditioned air is starting to become more common at gates (YYZ I think has it basically equipped everywhere). I don't know the specifics for a 737 operator but in the smaller stuff equipped with APU's they may not even mention APU use in the SOPs. Heck we've had the APU running all night in some places (CYCB) for maintenance and to keep the plane from deep-freezing. Sucks though as someone basically has to sleep in the airplane all night :).Mind you with WestJet and other prevalent 737 operators flying into smaller (colder) places like Grande Prairie, Yellowknife, Whitehorse (soon)....the economics of running a diesel powered conditioned air cart/truck vs. just running the APU basically make it more feasable just to burn the APU. Although most places have a GPU at a minimum for these type of operations.Europe is a whole other ball-game. Most airports have very strict rules on APU use (10 minutes before departure...etc..etc).EDIT: If any prospective airport operators are interested in some Turbine or Diesel powered (Detriot 6V-71's) conditioned air trucks i've got a source for plenty ;P Ha ha ha

Edited February 22, 201214 yr by Houghton11

United saved a lot of money by limiting apu use fleet wide. So did American by removing some of the magazines from the seat backs on the MD80 fleet. It's amazing the things airlines can do to lean out fuel costs. On the other hand, I have never been limited on APU use. When I was flying DC-10s, the APU ran for at least 1.5 hours prior to takeoff and 2 to 4 hours after landing before putting the plane to bed(Mx post flight and fueling). On average the DC-10 APU burned 425 pounds per hour(63 gallons per hour). Unfortunately we didn't have company gates, so we parked on the ramp and used air stairs. We were at the mercy of airport services for pneumatic and power cart rentals, so we just ran the APU. The G5/550 APU burns about 265 pounds per hour(40 gallons per hour). During corporate/executive ops, you find that ground support at airports can be pricey. Also with these operations, time is important. You have be ready to go when your principal arrives at the aircraft. As soon as my primary hits the first step, my right engine starts spinning. You don't have time to pull power carts and disconnect air. The principal may show early or may be late. Either way you have to be ready to jet out. I actually had to use a power cart once due to quiet hours. To my surprise the power cart was shady and started surging causing power flux within my aircraft. Before i could turn off the power it died. After walking out to the power cart, I noticed that the principal was arriving. Me and my copilot ran as fast as we could to get the APU up and the engines spinning. Now days I don't risk it with power carts unless I'm at a gulfstream service center. Airlines are a little different. I personally feel that airlines, in the U.S., run on the verge of bankruptcy.

Edited February 22, 201214 yr by G550flyer

It is not 737 related but when the An-124 visited my home airport it kept it's APU on for the entire loading/unloading procedure which took about 6 hours + starting procedure which was 2 hours. Although it might have been because of the power connection not fitting or being the wrong kind... Anyways it was quite interesting since the APU is at eye level and you can actually see into it.

All great info, guys. Kyle, your credentials are just fine LOL. I think you have spent enough time in and around (ATC and dispatch) that you know your stuff. I didn't realise how much input dispatch actually have in all of this stuff.Matt, when you leave off for taxi-in, do you fire it up at the gate? (location depending obv) Would there ever be an occasion where you might go fo APU start before landing?Patrick and Rick, thanks for this info. I was wondering about the relative costs of Jet A and volts! Over here in the UK I reckon you could run power/bleed from the main engines cheaper than a ground cart!Great info guys, thanks again!

http://www.youtube.com/watch?v=3zmuM3lTUYAguys and girls, this is the video(: LOL..

Ahh! That's it..Nice one, Daniiel..It;s the same, really interesting vid with the chief SWA pilot in..what a nice man :)

Matt, when you leave off for taxi-in, do you fire it up at the gate? (location depending obv) Would there ever be an occasion where you might go fo APU start before landing?

When send our IN RANGE report on ACARS, the message tells us the gate assignment and whether we've got good power/air conditioning. If we don't have electrics or air if we want it, we'll start the APU on taxi in. Some Captains did start the APU on final, but I haven't seen that done in a while. The Classic has some electrical differences that make it advantageous to have the APU on at night, and I think that's why some Captains did that.

More great info guys,Many thanks Matt for that extra snippet..I'm leaving APU off until 10 mins prior now..bestjakeACARS isn't a planned upgrade for NGX, is it? (I know this has been discussed - possibly to death, in other threads - sorry!)

Thanks for this thread, I had pretty the same question. Another thing with the APU keeps me thinking: I think i´ve heared somewhere that you should not connect the engine air bleed just seconds after angine startup but let it run by the APU for some time and connect them just before takeoff. Is that correct or a myth?

Myth. You're setting yourself up for a rubber jungle. We leave the packs and engine bleeds off for one minute after deicing. That's the only delay I can think off. Maybe you're thinking about configuring for a bleeds off TO. That's where you might delay until bearing the runway before configuring.

Myth. You're setting yourself up for a rubber jungle.We leave the packs and engine bleeds off for one minute after deicing. That's the only delay I can think off. Maybe you're thinking about configuring for a bleeds off TO. That's where you might delay until bearing the runway before configuring.

All right. Thanks a lot. :(