SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 2, posted (7 years 11 months 1 week 5 days 6 hours ago) and read 5390 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.
AeroWeanie From United States of America, joined Dec 2004, 1601 posts, RR: 52 Reply 3, posted (7 years 11 months 1 week 5 days 5 hours ago) and read 5356 times:
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.
Gearup From Canada, joined Dec 2000, 578 posts, RR: 1 Reply 4, posted (7 years 11 months 1 week 5 days 5 hours ago) and read 5345 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.
SATL382G From , joined Dec 1969, posts, RR: Reply 5, posted (7 years 11 months 1 week 5 days 4 hours ago) and read 5323 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!!.
ANITIX87 From United States of America, joined Mar 2005, 3244 posts, RR: 14 Reply 6, posted (7 years 11 months 1 week 5 days 3 hours ago) and read 5272 times:
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
Mr Spaceman From Canada, joined Mar 2001, 2782 posts, RR: 15 Reply 7, posted (7 years 11 months 1 week 5 days 2 hours ago) and read 5224 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.
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?
Jetset7E7 From United Kingdom, joined Jul 2004, 1083 posts, RR: 17 Reply 8, posted (7 years 11 months 1 week 5 days 1 hour ago) and read 5219 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
David L From United Kingdom, joined May 1999, 9248 posts, RR: 42 Reply 9, posted (7 years 11 months 1 week 5 days 1 hour ago) and read 5201 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.
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
A/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4 Reply 12, posted (7 years 11 months 1 week 4 days 22 hours ago) and read 5103 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
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.
Corey07850 From United States of America, joined Feb 2004, 2522 posts, RR: 5 Reply 17, posted (7 years 11 months 1 week 4 days 18 hours ago) and read 5023 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
Kaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 28 Reply 18, posted (7 years 11 months 1 week 4 days 18 hours ago) and read 5022 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
IFIXCF6 From United States of America, joined Sep 2004, 108 posts, RR: 0 Reply 19, posted (7 years 11 months 1 week 4 days 16 hours ago) and read 4977 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).
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 20, posted (7 years 11 months 1 week 4 days 15 hours ago) and read 4944 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.
HAWK21M From India, joined Jan 2001, 31228 posts, RR: 58 Reply 24, posted (7 years 11 months 1 week 4 days 4 hours ago) and read 4780 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
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 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 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 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 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 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
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
44 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 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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