What is a APU? Explained by "CAPTAIN" Joe
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- Опубликовано: 8 июн 2024
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Dear friends and followers, today´s question is another absolute classic, „Joe could you explain, what is the APU?“
The APU is a very important topic, so let´s get started !
I´m pretty sure many of you have seen and heard the APU before. Okay let´s imagine you´re in an bus driving you towards your airplane which is parked at an outside position.
As you get off the bus and onto one of the mobile stairs you can hear this sound? (APU sound) That my dear friends is the sound of an running APU.
APU stands for Auxiliary Power Unit. On most commercial jets the APU is placed at the far end of the fuselage and it´s main purpose on ground is to make the plane self sustainable providing it with electrical power and bleed air pressure for the air-conditioning system and especially for engine start.
Most APU`s are a single spool turbine which power an electrical generator and air compressor. The APU has it´s own electronic control box which monitors the start sequence, the turbine speed and exhaust temperature, oil and fuel supply and the bleed air outlet and in case of a failure it controls an automatic shutdown to prevent any further damage. It even has it´s own fire protection system which automatically activates an internal fire extinguisher reducing the risk of a fire. 
Наука
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Captain Joe, bringing aviation knowledge to the fans of flying.
Thank you!
gyazo.com/8daf25da097b1a99e96f19878c64bf45
Ben Kelly lmfao
+Ben Kelly you are sick very sick go to a hospital
TruthSeeker porn....
The APU played probably the most important role in the Hudson River Miracle - its early deployment was a masterstroke, despite not being on a checklist
On a military aircraft like the C-130 Hercules, we didn't start the APU until just before engine start, we had external ground electrical power to power the electronics and hydraulics, after starting engines 3 & 4, the APU was usually shut down as hthere was enough air from the two started engines to start the third engine and then air from the 3 started engines could start the 4th engine. On an older airliner like the Boeing 707-342C used by the RCAF up until the got their Airbus aircraft, the APU was in a start cart attached to the aircraft and used to start all 4 engines, then shut down, the external ground power stayed connected until all 4 generators were brought online. then both were hauled away by a mule as the final checks were being done.
Couple of questions. If the jet engine requires compressed air to run where does it get it when it’s at such a high altitude? Second question. Is it possible to start a jet engine by diving and using wind speed kind of like they do with prop planes or push starting a car?
Your first question can be explained by the presence of a compressor at the front of the engine. low pressure air is pressurised by a system of blades.once the air comes out of the compressor it is compressed and ready to be ignited. What powers the compressor? The compressor is powered by the work performed by the part of the engine that thrusts the plain forward.
To elaborate on his answer, a turbine engine (turbofan/turbojet) is generally divided into 4 sections ,compressor/diffuser, combustion, turbine and exhuast sections
High velocity air enters the compressor section and goes through a series rotating and stationary blades (axial type) as the air flows through velocity decreases while pressure increases, the diffuser located aft of the compressor blades also works to increase pressure before the air enters the combustion section.
Highly compressed air at around 800 degrees F is mixed with fuel (usually kerosene) and ignited via a VERY high energy spark deliverd from an ignitor plug. The burning mixture increases the velocity of the gases as it flows through the turbine section - witch also contains rotating and stationary blades(stators and rotors) and is directly coupled to the compressor section via shaft, so as the heated gases flow through the turbine section it powers the compressor which in turn drives the entire engine as long as you have fuel and air being burned. The exhuast section imparts an increase in velocity in order to maximize thrust. Air must be exiting the engine faster than it is being taken in order to produce thrust.
I wrote this more or less to test my own knowledge of turbine engines for my A&P test but hopefully someone finds this useful
You can start an engine by diving it by setting the ignition to crank, but it isn't practical
@@Ham-wh6py when you say 'by the presence of a compressor at the front of the engine' is the compressor mechanically coupled to the APU or does it run on electricity generated by the APU?
@@yubear420 Neither. Compressor is part of the engine. "powered by the work performed by the part of the engine that thrusts the plain forward" is referring to turbine, the part compressor is connected to. More details: ruclips.net/video/5kE9wxsxdfc/видео.html
Please don't forget make a video about the engine start sequence
Cpt. Joe! A video on the air conditioning system especially the bleed air and packs would be really helpful.
I know all of this stuff is essentially hardwired in your brain at this time, but I have never personally heard of an APU and always used to think the noise was just somehow the main engines making noise. I had never even thought about how power could be supplied to the cabin during docking, even though I had seen the APU exhaust port on many planes.
Thank you for your super insightful video and I look forward to learning about the main engine start sequence :)
Very helpful for a non-mechanical senior citizen!! Many thanks!
Watch this 1.25x speed Thank me later : )
Watching it at ×2 and he is still slow talking
Lol.. I always use 2x no matter what
“Getting off the bus onto the mobile stairs”
American airports: am i a joke to you?
In Hawaii you get off using mobile stairs. At least in Kona you do.
Thank you very much Joe for explaining how the APU works!
Man!! I always wanted to know about the exhaust port at the tail section and now got someone giving a simple and effective explanation about just what it does. Thanks a lot for this.
You are THE CAPTAIN ! Thank you for all your videos !!!!
I am the copilot, but thank you very much ;)
thank you sir for making my requested video.this was very helpful.
Plz make a video on RNAV, NAV, NAV* , LOC, LOC* etc. and there buttons
Good video! Here in YEG (Edmonton) when its cold out (-15C or colder) a few airlines wants APU fuel to run the APU overnight the keep the plane from freezing.
My friend who flies for AA says he also uses the APU to assist during take off from high temp / high altitude airports, especially while flying the 321. The APU runs the a/c and he has max thrust available for takeoff. He said that he's only over temped the engines 3 times, all at Phoenix Arizona. Love your video's CJ :-)
Another fantastic video Joe. BTW have a nice christmas
Thanks Patrick, you too :)
hey man, how long time without vídeos from you, then. you've Back!!
it's Great😎😂
Captain Joe you are such an inspiration to me you show high levels of professionalism, mannerism and respect. Your videos help me a lot with me studies. And we both know the cost of learning how to fly is not that cheap. I look forward to learn more from your channel and that you continue to progress along with your channel so that you are encouraged to make more videos.👍✈✈❤ One love .
Hi Captain Joe, just want to say how much I enjoy your videos, very interesting and you tell it in terms I can understand. Many thanks!
Yay I missed you/your videos! I am glad you're back! Thanks for another very informative and interesting one. APU makes such a beautiful sound lol * don't judge me * >:
Super erklärt Joe! Mach weiter so! Spotter-Grüße vom Flughafen München ;)
I love your vids, Joe. You make them interesting, and easy for everyone to understand. Thank you.
Thanks Joe, as always it was very informative.Keep up the good work. We look forward to more cool videos from u.
Great video. Loved the detail had no idea that was why air con stops at engine start. What does the apu actually look like inside?
Thanks Francis! I´ll upload a more detailed video about the APU soon! Greetings Joe
I remember working the rear lavs for the DC-10 while I was stationed at KDTW and those APU's were loud and constantly dripped turbine oil on my head.
I found the Channel today, and never felt so lucky 😃😃👍🏼👍🏼Watched nearly every video!
A good video as usual. When you do an extended one, you could talk about what you do when the APU is inop, such as using an ASU for engine start-up.
Why do you always start up the right engine (engine 2) first?
Video in progress!
Enrico Di'Cesare It is actually not compulsory to start engine 2 first. It is just Standard Operating Procedure mainly because Engine 2 supplies power to the yellow hydraulic
Enrico Di'Cesare that's where most of your power comes from, if I'm not mistaken.
Enrico Di'Cesare because triangles
I think they start engines further from the main exit.
500 likes and no dislikes, good job captain
Great video..Was aware of the need for the APU, and it's usage..But your video has added a lot more context..Great going..and keep making more such awesome vids.. It's the closest aviation buffs like myself can get to a real cockpit!
Finally, I now know what the planehole does. Thank you.
The title :D ""CAPTAIN""" Joe
Great video :)
its "Captain" Joe because he is a co-pilot. 3 stripes on your black shoulder pads = co-pilot
4 stripes on your black shoulder pads = pilot
Nice joe
Again a great detailed video. Thanks !
Congrats! Captain Joe... thanks for your videos!!!
Capt, The plane you used to demonstrate this video is it Air Berlin? I see the back of the fuselage as red and something tells me that you might be a pilot of Air Berlin. That is my guess. Thanks Capt.
How do turboprop planes use reverse thrust without the reverser doors? eg.ATR72 ATR42 and the DASH8
I think that the Propellers turn into the opposite direction
Aero Channel I don't think so because I do not see the propellers stopping to turn the other direction
Muhammad Furqan Naquib I don't think that they do, but if they did, it might be th at the pitch of the blades are inverted, so they create thrust in the opposite direction
Finean Chetham you gave the answer ! Each blade is rotating on it's axis during flight to get most of the efficiency. During engine failure, this blades also need to by rotate, up to a certain position to reduce drag (it's called the "flag" position in french). So, for reverses on a turboprop engine, you just need to rotate the blades even farther than the "Flag" position.
Ok, so the "Flag" position in french, stands for feathering in english, and the angle of a blade is the pitch ;)
Please make a video of starting the engine sequence.
This is a great video! I've been trying to find a good and a short explanation for the APU for a long time!
Very interesting for a train driver who had his first flight at the age of 56 ...... Thank you very much for all this information on the plane piloting
When you're an airline pilot, do you fly with the same captain and cabin Crew evertime?
No they change on a daily basis :)
Captain Joe does it happen that you meet the same person twice? right after the first time, i mean? If not, then yeah it happens from time to time doesnt it?
sir can you explain what is trim in an airplane and how does it work
Anant Mahajan
Trim is the position of the elevator, if it's 10 degrees up, the elevator it's self will point up 10 degrees. So if when you pull up your elevator with just the yolk and it can go 15 degrees up, you will have your elevator go up 25 degrees in total. Sorry if some of this info is weong
Excellent explanations captain.
Big love from Morocco.
Have a happy new year captain joe
What is the difference between the ECAM and EICAS? I hope u can answer quickly
Muhammad Furqan Naquib If you want a quick answer, you should google it! :)
Pilot738 but in more detail
Pilot738 because I am confused
ECAM is used by airbus, EICAS is used by boeing and embraer.
ECAM is a camera used for taxing and pushback. EICAS is a navigation system.
Hey Captain Joe, what does it mean to bleed air?
+KappaJohns Bleed air produced by gas turbine engines is compressed air that is taken from the compressor stage of those engines.
When the blood runs out and only the air is left.
KappaJohns so basically, engines (I'm taking about turbofans) have many different parts, including 3 types of compressors (I think; I'm not an expert). However, there are 2 ways turbofan engines produce thrust:-
• the air that is sucked in by propellers/ fans go through the process of combustion to create thrust
• the excess air, called the bypass air goes through the bypass section of a turbofan, exits through the end of the engine and creates thrust (Newton's third law of motion; action = -reaction)
So the air in the second category is called as bleed air.
Thanks a lot for this video, I finally learned what the APU is.
As always, amazing video, thank you for this information, I like to learn more from you
What happens if you go overspeed too fast?
MAS_ pilot high speed stall
a d if he is a “dumbass” then you explain it, because I believe he is right
@@NeilDjents As far as I'm aware, as long as you don't surpass Vne to maximum g-load for specified aircraft mass. It should be fine.
Stalling, only occurs because of an angle of attack too high for the wing to maintain lift. Because then, the separation point has moved so far forwards on the wing, you have virtually no lift being created. You can look up this principle alongside "center of pressure movements."
The speed at which you enter the stall governs the type of stall you go into. Because, a stall can happen at any airspeed, and is governed solely on the angle of attack, aka the angle of the chord line to relative airflow. The chord line being an invisible line drawn from the very leading-edge to the very trailing-edge of the wing (this includes flaps).
The reasons aircraft has a "stall speed", is because of the amount of lift they need to remain in LEVEL flight. You can look up something called the "Lift Formula", and it goes along the lines of:
Lift=CL1/2pV2S
Aka lift is equal to coefficient of lift times 1/2 rho (air density) times velocity squared times surface area (wing area). The coefficient of lift is broken down into two parts. Wing Camber and Angle of Attack.
If you increase any of the above factors, you increase lift AND drag inherently.
So, if you're going slow ("stall speed/ Vso"), you need more lift, because your velocity has decreased reducing lift. So what do you do? You can lower flaps, this will increase your angle of attack over that part of the wing, increasing lift. Or a multitude of other things. However, if you don't use flaps, etc. You pitch up and increase your AoA. But, once past a certain AoA (usually around 16 degrees depending on the plane), you stall.
However, as you go faster you encounter more problems, such as an effect called "Coffin's Corner". To my understanding, as the mach number is increased the wing will be more likely to stall at lower angles of attack, to an extent that at some point the stall speed, expressed in EAS/Equivalent Airspeed, will start to increase. If I'm correct, this is called a "Mach stall" or a "high speed stall" terms used to differentiate them from the more common low speed version.
en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)
Please, just note. I am note ATPL or air force trained, nor hold any certification to such a degree. That is all information I've found by reading, have a great day.
:)
Joe can u do a video about your personal experiences like being in a emergency that are INTERESTING. THANKS
I´ll see what I can do!
Thank you so much for your effort ! and happy to see more about this topic :)
Another great video! Can you do a future video, post take off and pre landing, detailing the specific points in flight when flaps are extended/retracted?
Hi sir Captain Joe, is it true that the APU cannot be started in the air and that this is the reason that some aircraft are fitted with a R.A.T. (Ram Air Turbine)?
APU can be started mid air. but in case of fuel outage wherein you don't have fuel to supply to APU RAT will come to help.
Thanks Jignesh!
If the APU can start the jets why not run the jets on compressed air for the whole voyage!
sunsetlights100
You actually think blowing out air with a BATTERY is going to get an A380 flying?
@@sunsetlights100 because the apu is only needed for start up and it uses a lot of fuel
What is Wing Vortex ?
Great video :)
Video in progress!
Great im exited :D
Thanx for your kind explanation. from south Korea.
Thanks very much Captain Joe for explain, APU
Very interesting.
Does the APU get turned off right after the engines are started? I assume yes.
I dont think so
done some googling. It is used for air conditioning and ventilation, so i dont think they shut it down i think it goes into a lower power mode
No, APU is turned off in normal flight. AC etc are run from main engine(s) using bleed air from them instead of from APU.
Yes obviously
Yes it does
Hey Captain Joe, are you already a pilot or still a co-pilot? (I saw the video about you as a co pilot but not sure if you have been promoted)
Yes I´m a copilot, not a captain ! Greetings Joe
oh ok good to know! thank you for responding
Sean keep an eye on his shoulders or wrists if the jacket is on. you should notice a change when Joe makes captain
A co-pilot is technically still a pilot...
I prefer to call you first officer ;)
Hi Captain Joe , I'm quite interested in knowing about planes and it's mechanism and functioning..your videos are so much informative and interesting that I make it a point to watch them whenever I get time and feel so happy..keep up the great work !!! Looking forward to more such videos ☺
Now I get it! Entering the airplane I always thought the engines were running. Then I would hear them turning on and asking myself what was that noise in the first place. Thank you Joe for all this awesome videos :) !!
Here catch the like
Haha thanks :)
What is n1
It's the shaft that connects the high pressure compressor with the high pressure turbine of the jet engine. N2 is for the low pressure side. The names refer to different rotation speeds.
Maple Syrup like on a 737 you a n1 limit I don't really get it
What do you mean with an N1 limit?
Maple Syrup yes like when you get derates
Okay. I don't know, but it's maybe because the high pressure compressor is the second (after the low pressure one), and if the N1 would spin too fast, the low pressure compressor couldn't feed in enough air for the second compressor, and it would try to suck a vacuum.
Great video, CJ. I'm looking forward to the follow-up to this one. Greetings from Los Angeles! :)
okay it works, thanks! now gotta get your video on how to start up the big motors.
CAPTAIN JOE, Is APU is on during flight??????
No, it's used to start engines
No, only in case of an ermergeny
ALISH Awasthi check out SAS Flight 751, has an episode in Mayday
Captain Joe
sure
Men fly Boeing
Bois fly Airbus
Masters fly Antonov
Gods fly wright. They just don't go very far.
Great videos, Joe ! another good idea for a video would be explaining the Ram Air Turbine, i think many people don't know anything about it.
Preparing for my pilot interview, thank you Capt. Joe!
@@uni8894 its benn 6 months so lets hope he got the job
Thank you so much Mr Joe you really lecture. Like the way you break down the information for everyone to understand where it starts and ends as well.and used of example .....I am working at Airport ...as a Technician assistance
Thks for subtitles in Spanish, you are a good teacher & very good performance. Congatulations!!!
Wunderbares Video! Vielen Dank!!!
I just like this sound!! and Thanks for explanation at the end (5:40)
I was very surprised after I saw KOR sub!! Thank you for sharing your knowledge.
Excellent video, i learned so much.
Hi Capt Joe, as a student pilot that doing A320 jet transition, I couldnt thank you more for the brief explanation. I really love it when you show the APU video cause then only I have idea how it works. I think it would have been better if you could use the white board behind you to draw a diagram on how the air bleed flow and valve open during start sequence. Keep on making great video, you just got another subscriber 👍🏼
Thanks for making such great stuffs videos. I love Aviation and its Working and everything.
Interessantes Video, das habe ich mich auch schon mal gefragt😊 danke Captain Joe für deine sehr Lehrreiche Videos!!
Freut mich das es Dir gefällt :) Grüsse Joe
Love your videos Captain Joe.
Very clear informative videos!..
Captain Joe, You are my Hero, you provided the best information on hidden aspects of Airplane techs. I always thought what is the hole behind the jet and now I came to know that's APU.
Thanks Joe. Very informative
I used to come here to pick up random bits of knowledge about planes, but now I come here because you explain important concepts better than my module does. I'm an aspiring Aircraft Mechanic :3
Of all of the aviation videos on RUclips, yours are some of the most fascinating and 'Genuine', Thank you for sharing some fascinating insight into your profession, I wish you great success in your career.
Hey Joe
Das ist wahrscheinlich der beste Kanal auf RUclips! Mach weiter so! ☺
Liebe Grüsse
thank you captain for detail explanation about APU
Amazing! Well done!
Great video, thanks!
Excellent as usual.
You are awesome Joe.
Captain Joe, I enjoyed watching your videos.
Thank you, Captain Joe!!!!!
EXCELLENT VERY INTERESTING CAPTAIN !
Dear.Captain Joe.I am not related to this feild but you explain so sweet that I listen your vedios.
Excellent video!
another great video!
Thanks captain! I’m in Costa Rica.
Hi Joe, amazing and clear video as usual! Question, after landing when do you start the APU? Thx =)
At the ILA I had the opportunity to listen to a Transall APU starting up. It's so crazy loud. I would say that it is louder than the Transall's turboprops
I was on a flight where we couldn't start up main engines, due to APU problem. I had no idea what that was, eventually pilots had to reset everything and all was good so thank you very much for clearing everything up :)
Very interesting! We flew on an Airbus 321 last week from PHL to SAN , from coast to coast here in the USA and I would associate all the avaiation facts you taught me from your podcast to our 5 hr. Flight! It was great! I 💙 flying. I had a window seat and I took lots of great pics. It was raining when we took off from Philly and it was cloudy for the first 2 hrs., but then the skies cleared up & I got some pretty pics of the farmlands in the middle of the country and then the Rocky Mountains, and then the deserts of the SW and Mohave in California! I had a ball!