APU Usage

[DO-82 driver]

I am researching how other Fractional outline the useage of the apu's on their aircraft.

What guidelines, if any, are being offered and are people adhering to them?

Thanks....

 

[NETFLIER]

its pilot by pilot.

here at netjets we burnt $14 million in apu fuel last year. so some of the guys need to cut down.

 

[old*art]

Short answer . yes and no. Some of our Falcons have more time on the apu than the engines. I will leave the obvious explanation to others, but it is about to become a hot item for saving money. I have never seen a Gwhiz with the door open without the apu running.

 

[CA1900]

At NJA it's pretty much common sense. Use it all you want to prep for the flight. Don't use it to eat dinner and watch a movie on a multi-hour sit.

That said, we were scheduled to sit for 4 hours in the Bahamas in the middle of summer last year, and the FBO didn't have air conditioning. I used my best judgment there.

But while the plane's occupied, if it's a hot day and we need the extra cold air from the APU, we'll absolutely keep it running until after takeoff. If it's a real nice day, we might not use it at all (on planes with electric start, obviously).

 

[HiSpeedFlyer]

Is an APU like TCAS???

 

[gutshotdraw]

In the G-IV, I loved ferry legs at the end of the day so we could use the "quiet shutdown" checklist and we could post-flight in peace and quiet. Alas, in the V/450/550, you have to run the APU after a flight in order to avoid corrosion issues from moisture accumulating in the APU compartment. Hence, the dorky headsets on the walk-around.

 

[skiandsurf]

Hence, the dorky headsets on the walk-around.

I was wondering about those dorky headsets. Will ear plugs work or are the dorky headsets a required item?

 

[gutshotdraw]

I was wondering about those dorky headsets. Will ear plugs work or are the dorky headsets a required item?

The aircraft is equipped with a David Clark or equivalent hearing protector. You can use whatever hearing protection you prefer or none at all....huh?....whats that you say!?? if you want to be deaf in a couple years. It gets pretty loud in the hellhole which is why I always liked the quiet shutdown.

 

[NJA Capt]

here at NetJets we burnt $14 million in apu fuel last year. so some of the guys need to cut down.

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.

 

[DO-82 driver]

its pilot by pilot.

here at netjets we burnt $14 million in apu fuel last year. so some of the guys need to cut down.

I will have to say the the estimated number is less then 10% of this figure. I was dervived buy adding up the total apu time off of each a/c hobbs meter then multiplying it by the average fuel burn per in for that type of a/c.

Not an exact science but it gives a pretty good guess. Our FOM does have an APU policy (FOM 6.8.3) but each a/c has their specific needds so time will vary accordingly.

Either way.....running the APU to watch a movie while sitting on the ramp in TEB is simply wrong.

 

[skiandsurf]

On the X, some guys go by the "Climb Checklist" that lets you turn it off then, at 18,000 feet. I think that is a little late.

I would rather turn it off during the "After Start Checklist", and not turn it on until the "After Landing Checklist".

But I also like the idea of a "Quiet Shutdown Checklist", for those easy flights with little to no cleanup needed.

 

[gutshotdraw]

Some real rough math just for the G-Wiz fleet:

APU burn approx 180 pph G-IV, approx 210 pph G-V/450/550. Lets say 190 pph avg since IV's outnumber the V fleet 3-1

Real rough guess of average 500 APU hours/year/airframe (it's actually probably higher)

Last number I heard for total fleet was 58 aircraft

Let's say $4.50 a gallon average (wouldn't you love to know what our real fuel price average is after all our fleet discounts with Signature et al?)

190 pph*500hrs*58= 5.51 million pounds / 6.67=826 THOUSAND gallons*$4.50=$3.17 MILLION in fuel for APU burn. Just for the G-Wiz fleet.

I was startled by the numbers myself. I'm actually guessing the number is higher. Of course, "actual mileage may vary."

 

[TCA]

Dang 'Gut" didn't know we could turn em off. I thought we just left them running and did a hot hand-off...

 

[Flex-ible]

At Flex, APU start is generally 30-45 minutes before scheduled departure. It might be up to an hour if it's really hot or cold. We leave it run if the turn is less than an hour or so. If the last leg is empty, normally the PNF will clean the cabin during the flight so we can shut down without powering the APU up and head straight to the hotel. The quiet is nice!

 

[Sparse]

General guideline at CS is to start it 30 minutes prior to an owner flight. We do not start the APU on taxi in unless it is a real quick turn. Of course good judgement make dictate another pattern, based on the circumstances.

 

[gutshotdraw]

Dang 'Gut" didn't know we could turn em off. I thought we just left them running and did a hot hand-off...

Wish that was every trip amigo! What really sucks is getting to level off and realizing you forgot to shut the bloody thing down (not that I've ever done that).

See you this week maybe....been working harder on vacation the past three weeks than I do on the job

 

[CA1900]

On the X, some guys go by the "Climb Checklist" that lets you turn it off then, at 18,000 feet. I think that is a little late.

I would rather turn it off during the "After Start Checklist"...

You must have a better ACM than the Excel! :laugh: On a hot day, we need the extra air to keep the thing to cool on the ground. Our normal checklists have us kill it at 10,000; if it's not a hot day, I'll often shut it down on the taxi out to cut down the noise on takeoff.

 

[DO-82 driver]

Thanks Flex and Sparse.

 

[bailey3083]

At Flex, APU start is generally 30-45 minutes before scheduled departure. It might be up to an hour if it's really hot or cold. We leave it run if the turn is less than an hour or so. If the last leg is empty, normally the PNF will clean the cabin during the flight so we can shut down without powering the APU up and head straight to the hotel. The quiet is nice!

That is the rule but I have seen plenty of people rub the APU for hours.

 

[CA1900]

That is the rule but I have seen plenty of people rub the APU for hours.

Uhhhhhh.... huh huh huh....