GPU+APU

JordanD

Honorary Member
Just something I've noticed working the ramp. Is there a point to having the GPU plugged in while the APU is running? I've seen quite a few planes come in and leave the number 2 engine running until we plug them up, but they'll leave the APU running afterward. I can see if they want to turn the APU off but it seems like most of them keep it running since the turns are scheduled to be pretty quick.
 
Just something I've noticed working the ramp. Is there a point to having the GPU plugged in while the APU is running? I've seen quite a few planes come in and leave the number 2 engine running until we plug them up, but they'll leave the APU running afterward. I can see if they want to turn the APU off but it seems like most of them keep it running since the turns are scheduled to be pretty quick.

Maybe the generator is deferred?

Maybe the APU has a cool down cycle, so it's switched off after they shut down #2 and then it'll shut itself down after getting temp stable.

Although, each load removed will lower fuel burn, so leaving the Gen off will have a lower burn than GEN + AIR.
 
Air conditioning?
I thought the APU took care of both electrical power and air conditioning? Again I dunno so that's kind of why I'm asking. We have to use a huge air conditioning cart to give them any AC from the ground. That thing's a pain. :mad:
Although, each load removed will lower fuel burn, so leaving the Gen off will have a lower burn than GEN + AIR.
Ah, wasn't really sure about that but meant to ask. I wasn't really sure if the APU worked just as hard regardless or not.
 
I thought the APU took care of both electrical power and air conditioning? Again I dunno so that's kind of why I'm asking. We have to use a huge air conditioning cart to give them any AC from the ground. That thing's a pain. :mad:
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Sorry, misunderstood your question. Too much maintenance, not enough flying lately.
 
I've noticed that a lot lately, too. Lots of hawkers seem to be plugged in with a GPU running. Is this something specific to hawkers?

...Saw a Citation X sit on the ramp toady for 93 minutes with the APU running before they shut the door. I only know it was 93 minutes because that's how long it was between the pax showing up and us getting released to the snooze room. That's not relevant, but I thought it was interesting.

-mini
 
My suggestion: Ask a crew member. I suspect they get a GPU for electrics and run the APU for AC. I also suspect they turn down (or don't ask for) the AC cart for a reason. Go to the mouth of the horse and you will find the answers you seek.
 
Nope...not much sense to have the GPU plugged in with the APU running.

That being said I like having the GPU plugged in and ready on the gate in case the APU decides to crap out.

The difference in fuel burn is minimal with the APU up and running between (Air Only) and (Air + Electric) off of the APU. Really it's the Air Conditioning that puts the higher load on the APU...On the ERJ at least the Electric may add 20-30lbs/hr on top.
 
I fly a hawker and have only used a GPU once, and that was when our APU wouldn't start.

The APU provides both an electrical source and environmental items, so there is no need to have a GPU.

As far as our planes go, the APU burns pretty much the same amount of fuel wether it is just running or it is carrying the electrical load and the air is on full blast.
 
On the Q I'll leave the GPU running while the APU is on in case the gen decides it doesn't want to put out power anymore. If that happens, the APU shuts itself down because the electrical system was designed somewhere in Poiland over a case of Vodka. If the GPU is still connected and on, the plane will still be powered. Plus, the APU will still provide air in addition to the ground air in EWR that cools about as much as me sucking on an ice cube and blowing on you from 5 feet away.
 
I thought the APU took care of both electrical power and air conditioning? Again I dunno so that's kind of why I'm asking. We have to use a huge air conditioning cart to give them any AC from the ground. That thing's a pain. :mad:

Ah, wasn't really sure about that but meant to ask. I wasn't really sure if the APU worked just as hard regardless or not.

The APU GEN can be turned off, but still use the APU for Air Conditioning.

Hook up external power, turn off APU GEN, don't shut down the APU, put all the packs to the APU, and keep the air conditioning going.

That way, you guys don't have to worry about pulling the external air cart out for us.

Our company saved a great deal of money last year by reducing our use of the APU for electrical and Air Conditioning.
 
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