Use of APU

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flyinhigh
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Use of APU

Post by flyinhigh » Fri Jul 19, 2019 10:56 am

Ok I gotta ask.

I’ve flown porter quite abit the past couple months and they NEVER use the APU. Even with this heat wave, we are sitting in an overheating aircraft and it’s not on.

What gives? Did the company pull them from the planes or what?
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GoinVertical
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Re: Use of APU

Post by GoinVertical » Fri Jul 19, 2019 11:53 am

I know a skipper that used to work there.

He said they had to send an email every time they started the APU and explain why it was required. And if they were sitting on the ground for less than a certain amount of time it wasn't acceptable to turn on the APU for bleed air.

Could be lies, could be old info, but that's what I've heard.
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lownslow
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Re: Use of APU

Post by lownslow » Fri Jul 19, 2019 1:00 pm

Some airports don’t permit whatever they decide is ‘excessive use’ of anyone’s APU, often with fines. There are other options to cool a parked airplane but many airports choose not to purchase them for airports that aren’t expected to go above some threshold temperature more than a given number of days per year.
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Grey_Wolf
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Re: Use of APU

Post by Grey_Wolf » Fri Jul 19, 2019 1:01 pm

NEVER might be an emotional response.

I know for sure that there are Captains that do use the APU.

In the past, Captains were told, every time you hit the start button it's 400$, so use it sparingly. There was also a tracking program that monitored APU usage. It used to be tracked on the blackberry; then morphed into an email; it's now tracked in the weight and balance program. It's simple and user friendly. There are newer captains that also reluctant to start it for whatever reason. Some prefer to use the Ground Air/PCA.

The fleet is getting older, and some APU's show their age, while others have been repaired and work nicely, and then there are some that are MEL'd. We get a daily list of inoperative APU during heatwaves, forwarded to outstations so that they can plan to accommodate planes that don't have an APU with a Ground Air Cart or Pressurized Conditioned Air (PCA) attached to the jet bridge. Some of the PCA's aren't all that great; they are controlled by the airport authority.

The guidance that we are given is that it's acceptable, as per Aviation Health and Safety to have a cabin between 18-25'C. Regulations state: "If reasonably practicable, the air temperature on board an aircraft shall be maintained at a level of not less than 18°C and not more than 29°C. It's left up the the Captain to deem what is 'comfortable'. Factors, like turnaround time, outside air temp, sunny vs. overcast day, parking location (direct sunlight into cabin vs shaded area) may affect the Captain's decision.

If we do turn on the APU for cooling, we are to let the APU stabilize for a minimum of 2 minutes before putting the bleed on, as per our 'best practices / summer operations memo'. In the air, we are told to run the fans at max/norm until the temperature is comfortable; then select 'min'. We are also to consider running two engines on the ground, with bleeds selected for passenger comfort. If taxiing on one engine, it's at 'max'.

Porter also goes to the point of having the cabin crew play an announcement over the DPAS, that to help cool the cabin down, for passengers to open their air vents, and if desired to point it away from them if they don't want the cold air blowing on them. Some Captains also reiterate that message during the passenger "welcome aboard" PA. That said, when we groom, the crew normally finds the passenger vents closed. Can't help if the passenger is warm, when we're supplying the cold air, but people are electing to close the vents.

I'm a big fan of starting the APU, and blowing cold air; so cold that penguins come out of the floor board! I also believe it's cheaper to start the APU and keep the cabin cool, and being proactive about keeping it cold; then to divert for a medical (overheated passenger). 400$ versus $7000 (100$/night for a hotel + food vouchers for a full 74 passenger flight).

Hope that helps shed some light!
(And to cooler/colder cabins, next time you fly)
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PT6onH20
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Re: Use of APU

Post by PT6onH20 » Fri Jul 19, 2019 6:00 pm

GoinVertical wrote:
Fri Jul 19, 2019 11:53 am
I know a skipper that used to work there.

He said they had to send an email every time they started the APU and explain why it was required. And if they were sitting on the ground for less than a certain amount of time it wasn't acceptable to turn on the APU for bleed air.

Could be lies, could be old info, but that's what I've heard.
I remember taking great pleasure in firing that APU up. So did most of the guys and gals as I recall. If It not on in the summer, I hope it's an MEL and not someone trying to save the company some cash at the expense of the comfort of fare paying passengers.
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fliter
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Re: Use of APU

Post by fliter » Tue Jul 30, 2019 8:40 pm

PT6onH20 wrote:
Fri Jul 19, 2019 6:00 pm
I remember taking great pleasure in firing that APU up. So did most of the guys and gals as I recall. If It not on in the summer, I hope it's an MEL and not someone trying to save the company some cash at the expense of the comfort of fare paying passengers.
It's never the latter. I am not sure how things have been in the past, but in my relatively short time at Porter I found that the management reiterates the same thing over and over again: use the APU, use max bleeds, use whatever you need to keep the passengers comfortable. To my knowledge, no one has ever been "in trouble" for overusing the APU, there is no "minimum time on the ground" guideline for using it, and the overwhelming majority of Captains will start it when appropriate. If the company tried to limit its use before, they must've realized that it wasn't wise and have since changed their stance. That said, there are a few reasons why it's not used:

* MELs. There aren't a lot of tails that have the APU MEL'ed, and the company tries to send those tails to places that are cooler or that have good ground air carts. However, in the middle of a heatwaves, a few of these planes inevitably end up in warmer locations.

* Q400 APUs are finicky. If they fail to start twice, maintenance action is required on them. It tends to happen more often in the winter that an APU would fail on start, but I've seen it in the summer too. If you try to fire it up twice and it fails... well, it's now considered inoperative.

* Sometimes an air cart would be hooked up to the airplane, and we'll discover that it's not doing much to cool the cabin. Air carts vary drastically in how well they can cool the cabin. However, it's not always easy to locate ramp staff to request for it to be disconnected. Technically, you could still start the APU and a valve is supposed to prioritize its output over that of the ground cart, but apparently that valve is a bit of a weak point, or so I've been told, and so some crews avoid firing up the APU in that situation. Or, if fuelling had already begun, the APU can't be started until it's complete.
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Warden
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Re: Use of APU

Post by Warden » Fri Aug 02, 2019 4:46 pm

fliter wrote:
Tue Jul 30, 2019 8:40 pm
* Q400 APUs are finicky. If they fail to start twice, maintenance action is required on them. It tends to happen more often in the winter that an APU would fail on start, but I've seen it in the summer too. If you try to fire it up twice and it fails... well, it's now considered inoperative.
Q400 APUs really don't like starting in the cold. They get hung up fail when the computer tries injecting fuel after the starter motors the turbine.

Protip for Q400 pilots. If your APU 'FAILED" on start and it's really cold out and you don't know the last time it might have been started, before you try the second time do the following.

1) select the APU ON
2) before pressing the STARTER button press and hold the APU fire test button
3) watch the APU control panel do it's self test (with the lights rolling through the panel)
5) count to 5
6) don't, deselect the APU ON button.. go right to the START but HOLD the START button down for about 5 seconds and you hear it wind up

%99 APU starts every time.

By running the FIRE TEST with the APU panel selected on, it resets the computer and 9/10 you will get a healthy start.

I learned this from maintenance when I snagged an APU one day after two failed starts. He came on board and did this trick and it started no problem. Told me in the future do the same instead of snagging it as 9/10 times this will solve the issue and avoid a snag.

Since learning that trick I never snagged another APU and always got them started even in -30* weather.
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Warden
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Re: Use of APU

Post by Warden » Fri Aug 02, 2019 4:49 pm

Also if you open one of the rear doors and the flight deck overhead emergency evac panel it creates a nice breeze through the cabin, if for some reason your APU is INOP and there is no aircart.

Old classic trick from the non APU'd Jazz planes :wink:
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AuxBatOn
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Re: Use of APU

Post by AuxBatOn » Fri Aug 02, 2019 9:07 pm

I also heard if the PM taps his head and rubs his belly while tapping the outboard foot on the floor, it helps start the APU.
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Warden
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Re: Use of APU

Post by Warden » Sat Aug 03, 2019 12:16 pm

AuxBatOn wrote:
Fri Aug 02, 2019 9:07 pm
I also heard if the PM taps his head and rubs his belly while tapping the outboard foot on the floor, it helps start the APU.
Hilarious.

Jokes aside, the procedure I posted works.

Next time you have a finicky APU (if you fly a Q) try it and you'll see. Enjoy that conditioned air.
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AuxBatOn
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Re: Use of APU

Post by AuxBatOn » Sat Aug 03, 2019 12:55 pm

Warden wrote:
Sat Aug 03, 2019 12:16 pm
AuxBatOn wrote:
Fri Aug 02, 2019 9:07 pm
I also heard if the PM taps his head and rubs his belly while tapping the outboard foot on the floor, it helps start the APU.
Hilarious.

Jokes aside, the procedure I posted works.

Next time you have a finicky APU (if you fly a Q) try it and you'll see. Enjoy that conditioned air.
Is that procedure written anywhere in the AFM?
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sstaurus
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Re: Use of APU

Post by sstaurus » Sat Aug 03, 2019 1:36 pm

Fire-test trick doesn't always work either, but it helps. Leaving the power switch on for as long as possible before starting helps too. In the summer the APUs are generally fine, it's the winter when they get clogged up with deice fluid that causes most issues.
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Warden
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Re: Use of APU

Post by Warden » Sat Aug 03, 2019 7:18 pm

AuxBatOn wrote:
Sat Aug 03, 2019 12:55 pm
Warden wrote:
Sat Aug 03, 2019 12:16 pm
AuxBatOn wrote:
Fri Aug 02, 2019 9:07 pm
I also heard if the PM taps his head and rubs his belly while tapping the outboard foot on the floor, it helps start the APU.
Hilarious.

Jokes aside, the procedure I posted works.

Next time you have a finicky APU (if you fly a Q) try it and you'll see. Enjoy that conditioned air.
Is that procedure written anywhere in the AFM?
It's a little thing called "technical knowledge."

You might be surprised but not everything ever known about an aircraft is written in an AOM/AFM.
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Warden
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Re: Use of APU

Post by Warden » Sat Aug 03, 2019 7:19 pm

sstaurus wrote:
Sat Aug 03, 2019 1:36 pm
Fire-test trick doesn't always work either, but it helps. Leaving the power switch on for as long as possible before starting helps too. In the summer the APUs are generally fine, it's the winter when they get clogged up with deice fluid that causes most issues.
Yeah it doesn't work every time but I've had much better luck getting them fired up in cold weather operations by doing it.

Considering one day I snagged it after two fails, and all the Mx engineer did was the fire test... started it and cleared the snag that's enough for me to know it's one method that can work.
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totalflyer
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Re: Use of APU

Post by totalflyer » Thu Aug 29, 2019 12:15 pm

Warden wrote:
Fri Aug 02, 2019 4:49 pm
Also if you open one of the rear doors and the flight deck overhead emergency evac panel it creates a nice breeze through the cabin, if for some reason your APU is INOP and there is no aircart.

Old classic trick from the non APU'd Jazz planes :wink:
For us the hatch in the flight deck is not to be opened unless of emergency situation... I think it has to do with potential damage to seals or not proper securing...
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