APU Usage

[blueridge71]

Is there a way to hook up a GPU to these aircraft? That way the equipment is up and running and no need to burn money.

The only airplane I ever flew that had an APU was the CRJ. It had external hookups for power.

IF a GPU is available at the FBO, is in working order, and is not being used by another aircraft.

Busy FBOs tend to not like having their GPUs hooked up to an idle aircraft for 3-4 hours.

 

[WabiSabi]

May we ask how you arrived at that number? There is no possible way to accurately estimate APU fuel used. Each aircraft has different guidelines for APU usage and there is not a separate fuel supply.

APU's have Hobbs meters and I'm sure a fairly accurate estimate can be made just by multiplying the fuel burn by the hours on the meter.

 

[CA1900]

Just as another data point, the APU in the Excel burns a little over half as much fuel if you don't use the bleed air (66 pph versus 112). If it's a cool, comfortable day, I'll often just use the generator unless it starts to get stuffy in the plane.

The Hobbs meter also turns at the same speed in either mode, which might throw those fuel burn estimates off a little.

 

[Diesel]

"HOPE AND PRAY"

Now those are words I have heard on numerous occations to describe your flights.

Forward CG is what describes your flights.

 

[DO-82 driver]

At least I don't need 2 sandbags to achieve that condition!!!!!!

 

[realityman]

Another consideration is that FBO's don't usually provide GPU's for free. If it's about saving money, it's a very modest savings at best.

I typically will start the APU 45 minutes before departure time on the Citation X. We need the APU for engine start anyway. Also, we are supposed to be ready for departure at least 30 minutes prior to actual scheduled departure time per our FOM. The IRS's in most of our X's need at least 6 minutes to align, and ATIS's, clearances, and programming can take over 10 minutes sometimes. And after everything's programmed, it still has to be cross-checked by the other crewmember per our FOM. Then throw in the fact that pax oftentimes will show early, it becomes clear that sometimes starting the APU 45 minutes before departure isn't enough time.

On a different line of thinking, if you have the APU, it SHOULD be used (but not for napping, watching movies, eating dinner, etc....). Mr. Moneybags didn't buy an aircraft with an APU just for bragging rights. He expects to show up to a climate-controlled aircraft on the ground. Keep cutting service to our clients and we WILL be nothing more than another airline before you know it.

And as others have mentioned, clients showing up late really mess with APU run times. It's just part of the game.

As for shutdown after departure, I don't like to do it until we're through 10K feet. The APU is an excellent backup resource, but only if it's running. Most of the time, by the time you reach cruise, if everything is running fine, it'll continue to do so. It's during the takeoff and approach phases that failures can be critical. For example, if during approach or takeoff you have a dual gen failure, you may have much less time to deal with it than at cruise. Or at the very least, things will be busier. With the APU already running during these phases, a dual gen failure almost becomes a non-event.

At any rate, it'll be interesting to see what APU policies NJA comes up with. I hope it doesn't impact customer service.

 

[G200_PILOT]

May we ask how you arrived at that number? There is no possible way to accurately estimate APU fuel used. Each aircraft has different guidelines for APU usage and there is not a separate fuel supply.

Every airplane we have that has an APU, also has an APU Hobbs meter on it. If you're a PIC, then you should have noticed that there will be entries made in the MX sheets that state "RECORDED APU TIMES."

It's actually VERY easy for the company to track APU usage and how much it's costing them. All they have to do is come up with an average dollar-per-gallon number and there you have it. I have flown the Hwkers and the G200 here and they both burn 200 pounds an hour. 200 pounds equals 30 gallons. At $4.50 per gallon, they're paying $135.00 an hour when we run that APU.

They'll take an APU hobbs meter reading just about once a month. With all the airplanes we have here that has an APU and as much as we run them... at $135 an hour, the tab runs up really fast.

$14 million? If that number were to be true, that means ($4.50/gal) we would have put 103,703 hours on our APUs last year. I'm not sure how many airplanes we have that have APUs but if we have 300 jets here that have APUs, then that means we averaged 346 hours per year, per airplane. Now that $14 million looks doable.

When I think of my average day with 3 or 4 legs, I think I may be running that APU for up to 4 hours a day.

 

[Diesel]

14 million, no offense but big deal in the overall picture of operating these planes and the company.

It is what keeps the owners happy because everything is set to go for them. Ever been on an RJ during the summer when they don't start the apu except for engine start. Ugh a real sweatbox.

Sure 14 million sounds like a lot to us but in realities its pennies. There are other bigger cost savings issues.

One ferry from lax to teb and you've just wiped out any cost savings on the apu.

 

[G200_PILOT]

14 million, no offense but big deal in the overall picture of operating these planes and the company.

It is what keeps the owners happy because everything is set to go for them. Ever been on an RJ during the summer when they don't start the apu except for engine start. Ugh a real sweatbox.

Sure 14 million sounds like a lot to us but in realities its pennies. There are other bigger cost savings issues.

One ferry from lax to teb and you've just wiped out any cost savings on the apu.

Well put my friend. That's what I was trying to get at. My numbers were very conservative and the math came out to each APU equipped airplane to using the APU for 346 hours per year. That's less than one hour per day!!!!