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APU Exhaust (Pic Of The Day)  
User currently offlineANITIX87 From United States of America, joined Mar 2005, 3309 posts, RR: 13
Posted (9 years 5 months 1 week 3 days 8 hours ago) and read 6404 times:
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In this photo, we are looking right into the exhaust system for the APU of the 742.


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Photo © Klaas Reinder Sluijs



I always thought the APU was electrically powered. What is there that needs to be released if that's the case? Or am I just completely wrong? Haha.

TIS


www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4
47 replies: All unread, showing first 25:
 
User currently offlineSATL382G From , joined Dec 1969, posts, RR:
Reply 1, posted (9 years 5 months 1 week 3 days 8 hours ago) and read 6399 times:

Quoting ANITIX87 (Thread starter):
I always thought the APU was electrically powered

Close. The APU provides electrical power amongst other things. It burns fuel to spin a turbine that then turns a generator.

Where did you think the electricity came from?


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 2, posted (9 years 5 months 1 week 3 days 8 hours ago) and read 6403 times:

The APU is powered by jet fuel. It is a little gas turbine engine.
It produces electricity.

Now if you could invent a unit that ran on electricity and produced jet fuel, and you need startup capital, well, talk to me.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1610 posts, RR: 52
Reply 3, posted (9 years 5 months 1 week 3 days 7 hours ago) and read 6369 times:
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Quoting SATL382G (Reply 1):
The APU provides electrical power amongst other things. It burns fuel to spin a turbine that then turns a generator.

The APU is also connected to a "load compressor", which provides compressed air to aircraft systems.


User currently offlineGearup From Canada, joined Dec 2000, 578 posts, RR: 1
Reply 4, posted (9 years 5 months 1 week 3 days 7 hours ago) and read 6358 times:

Looking at that photograph, I think the APU is missing. I can see the titanium enclosure forward of the APU but that's all there is plus the exhaust system as was mentioned above. Very interesting photo.

GU



I have no memory of this place.
User currently offlineSATL382G From , joined Dec 1969, posts, RR:
Reply 5, posted (9 years 5 months 1 week 3 days 6 hours ago) and read 6336 times:

Quoting Gearup (Reply 4):
Looking at that photograph, I think the APU is missing. I can see the titanium enclosure forward of the APU but that's all there is plus the exhaust system as was mentioned above. Very interesting photo

Aircraft is on static display at a museum. Also missing (last I checked) 2 engines, flaps, and the upper deck lav!!.


User currently offlineANITIX87 From United States of America, joined Mar 2005, 3309 posts, RR: 13
Reply 6, posted (9 years 5 months 1 week 3 days 5 hours ago) and read 6285 times:
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I thought it was the engine that provided electricity to the APU which powered the systems when they were needed. I thought the fuel turbine was on the engine and powered the APU...I just said the same thing two different ways, haha. Thanks for correcting me, and I'll contact you about the startup capital when I get my Ph.D. in Aeronautical Engineering in 8 years!

TIS



www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 7, posted (9 years 5 months 1 week 3 days 4 hours ago) and read 6237 times:

Hi guys.

Quoting SlamClick (Reply 2):
The APU is powered by jet fuel. It is a little gas turbine engine.
It produces electricity.



Quoting AeroWeanie (Reply 3):
The APU is also connected to a "load compressor", which provides compressed air to aircraft systems.

>> ANITIX87, have you ever been close enough to a parked airliner to see that it's jet engines are not running, however you can still hear the sound of a jet engine coming from the aircraft, & if you're downwind of it you may even smell the exhaust from a jet engine? If so, what you are hearing & smelling is the APU that's running in the airliner's tailcone. Big grin

Before the pilots start the airliner's jet engines, the APU's generator provides the needed electricity for the aircraft's systems (in the cockpit, the cabin, etc, etc) as mentioned by SlamClick. (Note: A ground cart/GPU {Ground Power Unit}, can also provide electricity instead of the APU).

When the pilots start the first jet engine, compressed air - as mentioned by AeroWeanie (also called Bleed Air) - is ducted from the APU in the tail forward to the starter motor on the jet engine. This compressed air spins a turbine inside the starter, which causes a series of gears in the starter's gearbox to turn. These gears are connected to the jet engine's main centre shaft and as as result ....... the jet engine's large intake fan & compressors start to turn, which begins the engine's starting sequence. (Note: compressed air for the starter can also be provided by a ground cart if needed).

Most modern jet airliners these days use pnuematic starter motors that require compressed air to turn them ..... unlike the starter motor in a car which uses electricity from a battery.

I hope this BASIC (very un-detailed) info about an APU gives you an idea of what they're used for.

>> Question ......

Is an APU also able to provide pressure for the airliner's hydraulic systems if needed?

Chris  Smile



"Just a minute while I re-invent myself"
User currently offlineJetset7E7 From United Kingdom, joined Jul 2004, 1090 posts, RR: 15
Reply 8, posted (9 years 5 months 1 week 3 days 4 hours ago) and read 6232 times:

We have alot of APU faults at MAN, with aircraft especially ZB A320's, they come on stand, set the parking brake, and cut one engine, until a GPU is connected.

When they are ready for departure an ASU (Air Start Unit) is required, along with Ground Power, this pumps air and helps start the engine, if need be it will do a cross-feed start on stand, where it powers up one engine to help start the other.

Correct me if I'm wrong, I just work on the ramp.

Mark



Retrofitted Blended Winglets - The Future Is On The Wing
User currently offlineDavid L From United Kingdom, joined May 1999, 9543 posts, RR: 42
Reply 9, posted (9 years 5 months 1 week 3 days 3 hours ago) and read 6214 times:

The caption on the photo says "Did you ever have a look in the a... of a Jumbo ? (APU exhaust)". I wonder how many wristwatches have been lost in there.

User currently offlineMatt72033 From United Kingdom, joined May 2005, 1617 posts, RR: 4
Reply 10, posted (9 years 5 months 1 week 3 days 2 hours ago) and read 6173 times:

Quoting Mr Spaceman (Reply 7):
>> Question ......

Is an APU also able to provide pressure for the airliner's hydraulic systems if needed?

from what i understand.......only through supplying Electrical power to electric motor hydraulic pumps.....but i would have thought this was more in the case of an emergency!

they dont have a hydraulic pump on them! (that ive ever heard of anyway!) please correct me if i'm wrong anybody

[Edited 2005-07-14 22:08:44]

User currently offlineEuclid From South Africa, joined Apr 2005, 373 posts, RR: 0
Reply 11, posted (9 years 5 months 1 week 3 days 2 hours ago) and read 6162 times:

If I may also ask a question, what is that little thingy sticking out of the panel right at the top?

User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 12, posted (9 years 5 months 1 week 3 days ago) and read 6116 times:

When we say that the APU provides pressure for the hydraulic systems, what we mean is that the APU bleed air is tapped into the top of the hydraulic reservoirs too provide a head of pressure on top of the fluid, this pressure is usually around 50 psi. All this does is provide a positive feed of fluid too the hydraulic pumps too prevent cavitation.
As has already been said, the APU is just a small gas turbine with a load compressor which delivers air too pneumatic systems and an A.C generator mounted on the APU gearbox which provides a.c power on the ground and as a standby in certain failure conditions. It runs on fuel from the aircrafts fuel tanks.
Regards a/c


User currently offlineKl671 From Canada, joined Jul 2005, 141 posts, RR: 0
Reply 13, posted (9 years 5 months 1 week 2 days 22 hours ago) and read 6078 times:

The APU on the 747-400 series is a P&WC 901A. Read all about it at

http://www.pwc.ca/en/3_0/3_0_2/3_0_2_5_1.asp


User currently offlineAloges From Germany, joined Jan 2006, 8764 posts, RR: 42
Reply 14, posted (9 years 5 months 1 week 2 days 22 hours ago) and read 6072 times:

Quoting Euclid (Reply 11):
If I may also ask a question, what is that little thingy sticking out of the panel right at the top?

Might be a strobe.



Walk together, talk together all ye peoples of the earth. Then, and only then, shall ye have peace.
User currently offlineAR1300 From Argentina, joined Feb 2005, 1740 posts, RR: 3
Reply 15, posted (9 years 5 months 1 week 2 days 22 hours ago) and read 6068 times:

Quoting SATL382G (Reply 1):
Where did you think the electricity came from?

There is a hamster on a wheel in the cargo bay.From there.

mike



They don't call us Continental for nothing.
User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 16, posted (9 years 5 months 1 week 2 days 21 hours ago) and read 6057 times:

Quoting Matt72033 (Reply 10):
Quoting Mr Spaceman (Reply 7):
>> Question ......

Is an APU also able to provide pressure for the airliner's hydraulic systems if needed?

from what i understand.......only through supplying Electrical power to electric motor hydraulic pumps.....but i would have thought this was more in the case of an emergency!

they dont have a hydraulic pump on them! (that ive ever heard of anyway!) please correct me if i'm wrong anybody

The APU on the C-160 Transall drives a generator and a hydraulic pump (red system) which can supply the majority of hydraulic systems.

View Large View Medium
Click here for bigger photo!

Photo © Achim Stemmer




This job sucks!!! I love this job!!!
User currently offlineCorey07850 From United States of America, joined Feb 2004, 2528 posts, RR: 5
Reply 17, posted (9 years 5 months 1 week 2 days 20 hours ago) and read 6036 times:

Quoting Mr Spaceman (Reply 7):
Before the pilots start the airliner's jet engines, the APU's generator provides the needed electricity for the aircraft's systems (in the cockpit, the cabin, etc, etc) as mentioned by SlamClick.

And these are the times when King Air pilots miss their wheels-up times because they can't monitor gate hold  Wink


User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 25
Reply 18, posted (9 years 5 months 1 week 2 days 20 hours ago) and read 6035 times:

On a B744, expect the APU to burn about 500kg/s of fuel per hour...


Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineIFIXCF6 From United States of America, joined Sep 2004, 108 posts, RR: 0
Reply 19, posted (9 years 5 months 1 week 2 days 18 hours ago) and read 5990 times:

Regarding the thread question:
The APU drives the electrics, not the other way around. The APU is also capable of pneumatic (compressed air) power in all airliners that I've worked.

Speaking of hydraulics...
In some A/C, only electric (i.e. "AUX") pumps are energized by the APU, in others you may have air-driven pumps (ADP's) as an option...or mandatory for that system. It gets complex when speaking of the many airliner designs, but an APU can power all of this. But, other than starting, an APU does not receive power. The hole is for jet turbine exhaust, it burns JET-A (usually).

Mike


User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 20, posted (9 years 5 months 1 week 2 days 17 hours ago) and read 5957 times:

Quoting Euclid (Reply 11):
If I may also ask a question, what is that little thingy sticking out of the panel right at the top



Quoting Aloges (Reply 14):
Quoting Euclid (Reply 11):
If I may also ask a question, what is that little thingy sticking out of the panel right at the top?

Might be a strobe.

It looks more like a Position Light.The Strobe is the Rectangular one located at the Bottom.
BTW the APU is missing.Whats visable is the Exhaust Duct.

APU or Auxiliary Power Unit is a Constant speed Centrifugal Gas Turbine Engine,located "mostly" at the Aft section of the Aircraft & used to supply Electric,Pneumatics for Air-Conditioning,Engine Start with the help of Generator mounted on the APU Gearbox & Thru a bleed valve to provide bleed thru the Pneumatic duct resp.

Also Why are the Inbd corners of the Elevator having that chipped off shape on both sides.


regds
MEL

[Edited 2005-07-15 07:19:51]


Think of the brighter side!
User currently offlineJimpop From , joined Dec 1969, posts, RR:
Reply 21, posted (9 years 5 months 1 week 2 days 17 hours ago) and read 5958 times:

Starting at the exhaust port and moving downwards, what are the shiny metal items? lights?

User currently offlineDanman From United Kingdom, joined Jul 2002, 39 posts, RR: 0
Reply 22, posted (9 years 5 months 1 week 2 days 13 hours ago) and read 5924 times:

Jimpop,
Two tail position lights (navigation lights) side by side, the rectangular unit below is the tail strobe light.


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2577 posts, RR: 25
Reply 23, posted (9 years 5 months 1 week 2 days 8 hours ago) and read 5835 times:

Quoting AeroWeanie (Reply 3):
The APU is also connected to a "load compressor", which provides compressed air to aircraft systems.

Older, single shaft APUs have an oversized compressor which provides excess air for the pnematic system.

Quoting HAWK21M (Reply 20):
Also Why are the Inbd corners of the Elevator having that chipped off shape on both sides.

May have been damaged in transit when the aircraft was moved to the museum?



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 24, posted (9 years 5 months 1 week 2 days 7 hours ago) and read 5793 times:

Quoting Jetlagged (Reply 23):
May have been damaged in transit when the aircraft was moved to the museum

Could it be Aerodynamic Damage painted over rather than Impact Damage.Because the Paint does not look peeled.seems its an old damage.
Any Pic of similiar Angle.
regds
MEL



Think of the brighter side!
25 Tod : The bleed air can also be used pressurize the potable water system such as on 747.
26 Bruce : Speaking of APU's, what is the purpose of the light as seen in the above photo....right below the exhaust? bruce
27 Post contains images Starlionblue : Talk to me first
28 MD11Engineer : Even if the APU was installed, you wouldn't see it in the picture. The exhaust duct is about 2-3 meters long and pitch dark on the inside. You'll need
29 Air2gxs : The upper pair of lights are the white navigation lights. The lower light is the stobe light.
30 Bruce : Ok, sorry if its a stupid question but what purpose does the nav light serve? Is it only so that other planes can see you:? bruce
31 Post contains images Oly720man : For those who've never seen an APU in the flesh, here are some photos of one we have at our lab. It used to be in a Trident, so it's rather old, and w
32 MD11Engineer : Looks like an old Garrett APU. What were they objecting to? The noise? You've got to build yourself a noise proof test cell with built in fire extingu
33 Post contains links and images Aviopic : Yes the APU is indeed missing, not that you can see it but as I spend many hours in the APU compartment I know it isn't there. Yup, The Dutch Aviatio
34 Oly720man : It's a University. They were objecting more to the thought of a large fuel tank, but the noise did come into it.
35 Matt72033 : didnt the tridents have thrusting APU's? apparently they thought of this for the 777 at one point! but decided against it! (only for take off mind)
36 Post contains links and images LorM : I found these somewhere awhile ago, probably last year, on the net, and just recently while searching through my backup external HD. 777 APU pictures.
37 David L : Good question. I know the Trident 3s had a small fourth engine for take-off but I never thought whether they had a separate APU or that was it.
38 Post contains links David L : This is the best info I can find. Erm... it's from a die-cast aircraft forum so it's not exactly technical confirmation: http://www.diecastaircraftfor
39 Starlionblue : Also, the 747 APU is more powerful than both the engines on a Twin Otter. Another fun fact: The BAe-146/Avro RJ is powered by a model of jet enginewh
40 Post contains images David L : More accurately, as a die-cast metal aircraft enthusiast says. Yes, but it was a bit more elegant than a RATO job! And it was quite cool to feel it s
41 Matt72033 : ahhh ok....fair enough!
42 Bio15 : I always thought that APU's pneumatic supply came from some compressor stage bleed. Is the load compressor another way of saying this, or it's a sepa
43 HAWK21M : The GTCP on the B737s do. regds MEL
44 Post contains images Starlionblue : It was shut down in flight. Consider us warned
45 David L : Much as I suspected - thanks. I think you're OK. (Un)fortunately, an even better 747-400 model has just been released. The Trident might not get a lo
46 Post contains images SlamClick : The same Avco-Lycoming engine core as on these aircraft: Which predate the 767 by a long time. Initial design of this engine was in 1954, before airl
47 David L : The same core in a turboprop, turboshaft and turbofan. Is that fairly common or is it unusual?
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