APU utilisation versus flight hours
 

Anyone know what the average utilisation (hours) of the APU is on a 777 versus flight hours? IE 14 hrs/day flight utilisation versus 'x' hours on the APU?

Cheers
Carl

Are you looking for the specific utilization per flight hour (not including time used by engineers, groomers, positioning ...etc etc) or an average complete use of the APU divided up by flight hour.

I know it sounds high, but on a 22,000 hour airplane for example, our APU time is around 16,000 hours (On Condition woohoo!). This is in Chilly Canada though where we sometimes just let it run all night.

APU hours verus Airframe hours is going to be different for a B747 utilized by AirNZ to one used domestically by JAL for example. Where the aircraft is used on predominately long haul the APU hours v Airframe hours will be very low. In the JAL case where the B747 can be a domestic "air taxi", it may be almost equal. It is like asking how long is a piece of string, unless you specify in what type of operation the aircraft is used.

You will have to compare its clock reading with the actual Flying Hours.
That would be the most accurate method. :ok:

10 mins after landing whilst waiting for ext pwr, 10 mins before departure, depending on cabin temps, that's our SOP.

I think the JAL 747 APU use is going to be REALLY low :}

JAL 747
 

Thanks Pontius. Of course JAL B747 APU use would be "really low" NOW, since they no longer operate the type. I used the JAL domestic versus ANZ analogy simply to make the point that APU on longhaul operators, regardless of type, will be significantly less than the same type used on short haul domestic or regional flights.

That is in the ballpark for most operations, unless stops occur at airports of a more rustic nature. In temperate climates, we don't use the APU after landing and grab power and air once at a gate.

That would be of no use. APU's are changed many times during the a/c's life. For example, this week I had a check on an aircraft with about 30000 hours, the APU had 5000 hours and 6000 cycles (approximated); another airraft with same hour life had an APU with 600 cycles and 280 hours.
I would say on an average flight the APU is used 10 minutes before and 10 minutes after engine running. Maintenance most of the time also add a fair amount of APU use.

Twenty or (more likely thirty) more years ago, APUs were frequently rum from shortly after touch down to after engine start. Today it may not even be started after touch down, leave one engine at idle till external is connected. If cooling or heating is needed a ground unit will be attached.


Certain airports have rules on APU usage, usually for noise. APU started just prior to engine start and shut down shortly after the last engine is started.


On certain aircraft the APU may be left running to provide heating, cooling if a pac's off performance is needed.


For long haul operations say two sections in 24 hours, maybe 30 minutes of APU. Short haul without external start carts, maybe something less than 90 minutes.


A lot of early 727-100 came from Boeing (United) without an APU. Cannot think of one after that, that did not have an APU.

Piper19
 

I agree in principle of what you say, but l was talking about Airframe hours accumulated while the APU was installed.
You take a APU clock reading when you install or replace the APU, which is recoded along with aircraft Flight Hours & Cycles.
Any technical Records department will be able to supply this to you.
My company regularly records the APU clock readings, this is for financial reasons as the finance department requires them for their monthly figures. :ok: