I used to wonder. I thought maybe some system was doing a self-test upon engine startup, but I also wondered why it sometimes lasted longer on some flights than others, and why it would also “self-test” upon engine shutdown. Knowing what I know now, it just means my Airbus is happy and wagging its tail, figuratively and literally. I’d be extremely concerned if I was on an A320 that *didn’t* bark.
I’ve been wondering for years what that sound was. I asked the cabin crew once and they had no idea what I was talking about. And now finally, after years of waiting, it’s the PTU. Thanks man!
LOL, I think they were just tired of answering the same question over and over. “What noise? I don’t hear any noise. By the way, here’s a pillow, perhaps you can bury your ears in it.”
I always enjoy explaining this noise to fellow passengers. Countless times, people have actually thought there was a dog onboard. LOL Whenever I fly on Airbus planes, I always look forward to this.
Once again great content. Amazing the engineering involved in an aircraft. Thoroughly enjoy how you break it all down and explain how it all works. Cheers bud!!
Buddha! Nicknamed that because the initial delivery flight from Seattle to Charleston AFB would not have been possible without a cargo compartment full of Boeing engineers on laptops keeping it flying due to all the software glitches that had yet to be worked out to meet the delivery date. It didn’t fly again for about 2-3 months while Boeing worked all the bugs out. It was big, fat, sat on the ground and everyone worshipped it. Hence the nickname, Buddha.
1:20 I'm really curious as to what causes the actual "bark" noise of the pump...? Is that due to a check valve or something like that releasing? Or due to the pump itself cycling? (I've have a difficult time trying to understand how the pump physically works, there are diagrams, but I haven't been able to find a animation of it.)
I also wonder. I’d hypothesize that the whining comes in when fluid flow on the higher pressure side drives a shaft that pumps up the lower pressure side, and the barking must be the sound of the variable displacement doodad varying its displacement whenever the pressure differential is greater than 500 PSI. I’d guess it must vary displacement such that one side can’t go higher without the other side going lower, thereby self-regulating the mechanical advantage the high side has over the low side as required. I don’t know though, just guessing based on my theory about how it COULD work, not how it actually does work. Now I’m curious enough to try looking it up. I want to know whether I’m close to right, or just inventing crap in my head.
OK, I’m sort of right, sort of wrong, and it’s also more complicated than I first thought. One side (the green side, I believe) is fixed displacement, the other is variable (which I’d know if I first comprehended what Stig said). The green and yellow sides are hydraulically separate but are connected by a drive shaft. Both sides can function either as a motor or a pump. Whenever there’s a differential of 500 PSI, valves open and the higher-pressure side of the unit, whichever side that is, functions as a hydraulic motor. That spins the drive shaft so that the lower-pressure side of the unit can function as a pump. The PTU’s functionality can be boosted by an electric motor, providing additional pressure to the lower side while relieving some of load the from the engine driven pump on the higher side. I’d have to guess that the whine is from the electric motor. I’m not sure the purpose of variable displacement (to adjust mechanical advantage between the sides is still my best guess) or why it’s deemed necessary on one side but not the other. Most of all, I’m still not sure what makes it bark. So that’s where I’m at.
Informative video.except... On the 737 what he is pointing at, is not the PTU. That is the Flap Power Drive unit. If you want to see the PTU, it would be on the beam where that reservoir(standby reservoir in the video) is attached and go near the end of the beam on the other side.
You are absolutely correct. That was my fault because the video went out of sync when I did the voice over. The PTU is very small on the 737 and as you stated in the center keel beam.
It’s completely normal, sometimes the pumps need to compensate and this is why you hear the noise. Just because one of the engine driven pumps are not producing enough pressure. The power transfer unit will compensate.
Because Airbus has 3 independent systems and it acts as an extra redundancy system in case one engine driven pump fails. It can still provide hydraulic power to the failed system.
This was in reference about the Airbus pushbutton switches on the overhead panel when turning the PTU on and off. When pressed an "off" indication. Does that mean it's off or it needs to be pushed again to actually be off.
@@absters33 this is a great question, what you were referring to is actually the whole concept of dark flight deck, so what that means is, if the unit is off, the light will come on. This will illuminate and give notification and will be very visually apparent. Since we’re working off of a dark flight, deck concept, if all lights are Off that means everything is working properly. I hope that makes sense. But it is a very comical thing when your first encountering it. Turn off, push button off Legend comes on. 🤣🤣
@@StigAviation thank you for explaining it in great detail and what indication is to be expected in normal operations. Very knowledgeable and helpful thanks!
You just answered your own question tho. If all three systems are independent and the PTU is the cross connecting them. Even if you have the PTU fail you still have the independent systems working. You can even have 2 systems fail and still have control.
@@StigAviation I should have been clearer, if all 3 systems are connected to the PTU and it catastrophically fails (ruptures) could the pressure/fluid be lost in the aircraft or are there redundant valves that would close off.
To clarify a little, because I did some research after having the same question as you, there are two sides of the unit (green and yellow) that are hydraulically separate, but connected by a drive shaft. Each side of the PTU can be thought of as both a hydraulic motor and a hydraulic pump. If the green side has low pressure, the yellow side functions as a hydraulic motor, which spins the drive shaft, which drives the green side to function as a pump. If the yellow side has low pressure, it’s the same idea, mirrored; the green side functions as the motor, the yellow side as the pump.
ihere is that before when they star the right engine this song will cames up also i see all the light and tv will stop work and when the right engine start complite all the systerm get work
Bro kindly make a video on 737 hydraulic system & compare it with A320 it will be an comparison of both technologies. Like how 737 hydraulics get pressurized in case of one engine stop or start etc..
When you have a variable displacement pump, it’s constantly trying to keep up with the pressure so hence you hear the continuous noise with pitching up and down in tone and you get that bark sound.
@@StigAviation Yes, the answer is for aircraft mechanics, they don't need explanations in these matters. I mean you didn't answer for normal people. Mechanics don't need explanations in these matters, on YT this type of information is sought by normal people, passengers of aircraft, not mechanics :) I know now what it is from other video of other creator. Cheers
@@mariodario9033 cheers. Glad you found it. And that’s the foundation of my videos. To make you research and find more information. Thank you for your intellectual ability to understand.
@@cooluke29 I own this video because that me talking in it. Please share are the link of where you saw it and please report them if you could. Thank you
@@StigAviation unfortunately I don't believe I can report it as I'm not the owner of your video or anything and there's not a simple stolen video button to my knowledge
PTU is exactly why I cannot stand the Airbus a320 family. I have no problem with airplanes and their hydraulic noises but the A320 family's noises are extremely irritating. I love Airbus for its a350s and a380s but I try to avoid the a320s altogether (and yes, this includes the a321).
It’s not like the hydraulic system is constantly functioning, you’re not hearing that sound all the time, it’s only in the beginning and the end of the flight
Pff, flown last week in a 16 year old a320 and an 8 year old 737-800 - the Boeing was way louder on the inside Still like the 737 tho, but don’t be unfair
I don't care what ppl think! This is the best sound ever on Airbus! ❤
And it lives rent free in my head 24/7 😂
I guess it's enough for you! 😅
I used to wonder. I thought maybe some system was doing a self-test upon engine startup, but I also wondered why it sometimes lasted longer on some flights than others, and why it would also “self-test” upon engine shutdown. Knowing what I know now, it just means my Airbus is happy and wagging its tail, figuratively and literally. I’d be extremely concerned if I was on an A320 that *didn’t* bark.
I always favored the sound of the electric hydraulic pumps shutting off on the CRJ’s.
I’ve been wondering for years what that sound was. I asked the cabin crew once and they had no idea what I was talking about. And now finally, after years of waiting, it’s the PTU. Thanks man!
Glad to help
LOL, I think they were just tired of answering the same question over and over. “What noise? I don’t hear any noise. By the way, here’s a pillow, perhaps you can bury your ears in it.”
I always enjoy explaining this noise to fellow passengers. Countless times, people have actually thought there was a dog onboard. LOL Whenever I fly on Airbus planes, I always look forward to this.
I always get a kick out of the peoples expression when the barking dog kicks on 🤣
Brilliantly explained, thanks!
happy you enjoyed it
A dog on our flight barked back at it.
😂😅😂
PTUが作動する音が好きです😊
Always wondered what that sound is exactly. Thanks for sharing!
Thanks for watching!
Once again great content. Amazing the engineering involved in an aircraft. Thoroughly enjoy how you break it all down and explain how it all works. Cheers bud!!
Thank you very much and I’m very happy you enjoyed it 👍
BTW the best video in UA-cam on PTU congrats buddy fr creating such amazing content.
Thank you very much
Amazing, simply explained video. Thank you
I’m glad you enjoyed it!
thanks.
As someone who works on equipment, I assumed it was a hydraulic system- but i certainly appreciate the walk through!
Glad it was helpful! Thank you for being here, I appreciate you
I've wondered for so long what that was, thanks for the explanation
Glad I can help
Thanks for this great explanation & the precise view! 💪 Amazing Content
thank you very much
Was literally wondering wtf that noise was flying back from Texas. Thanks.
Never in my life did I think to liken this sound to a bark. I always imagined the fuselage beint sawn in half
Glad you enjoyed it. Thank you for watching
Awesome video! Thank you very much for sharing your knowledge!!
Thank you for being here. I appreciate you watching
To me it rather sounds like sawing a piece of wood
Yes!!
More like my neighbour at night
The C17 also has a PTU and it sounds just like the one on the A320.
I didn’t know that, thank you for the education
Buddha! Nicknamed that because the initial delivery flight from Seattle to Charleston AFB would not have been possible without a cargo compartment full of Boeing engineers on laptops keeping it flying due to all the software glitches that had yet to be worked out to meet the delivery date. It didn’t fly again for about 2-3 months while Boeing worked all the bugs out. It was big, fat, sat on the ground and everyone worshipped it. Hence the nickname, Buddha.
@@allenemiesforeignanddomest3320 The C-17 was built in Long Beach and initially by McDonnell-Douglas, though.
Thanks for telling me about this video in response to a comment I / question that I posted on another one of your videos.
Any time!
That explains why my A220 was barking all the way to the runway, taxiing on one engine!
A220s have the barking dog sound too?
Excellent upload. Above all no jarring music😂.
Glad you enjoyed it 👍
Now thats a quality content.. Great job buddy❤
thank you so much
Quando viajei pela primeira vez e ouvi esse barulho meu coração quase saiu pela boca 😂 da um medo absurdo !!
I’m glad you now know what it is. So there is no need to be scared anymore.
1:20 I'm really curious as to what causes the actual "bark" noise of the pump...? Is that due to a check valve or something like that releasing? Or due to the pump itself cycling? (I've have a difficult time trying to understand how the pump physically works, there are diagrams, but I haven't been able to find a animation of it.)
It’s due to the power transfer unit trying to keep up with the pressure on the system. Remember it’s a variable displacement pump
I also wonder. I’d hypothesize that the whining comes in when fluid flow on the higher pressure side drives a shaft that pumps up the lower pressure side, and the barking must be the sound of the variable displacement doodad varying its displacement whenever the pressure differential is greater than 500 PSI. I’d guess it must vary displacement such that one side can’t go higher without the other side going lower, thereby self-regulating the mechanical advantage the high side has over the low side as required.
I don’t know though, just guessing based on my theory about how it COULD work, not how it actually does work. Now I’m curious enough to try looking it up. I want to know whether I’m close to right, or just inventing crap in my head.
OK, I’m sort of right, sort of wrong, and it’s also more complicated than I first thought. One side (the green side, I believe) is fixed displacement, the other is variable (which I’d know if I first comprehended what Stig said). The green and yellow sides are hydraulically separate but are connected by a drive shaft. Both sides can function either as a motor or a pump. Whenever there’s a differential of 500 PSI, valves open and the higher-pressure side of the unit, whichever side that is, functions as a hydraulic motor. That spins the drive shaft so that the lower-pressure side of the unit can function as a pump. The PTU’s functionality can be boosted by an electric motor, providing additional pressure to the lower side while relieving some of load the from the engine driven pump on the higher side. I’d have to guess that the whine is from the electric motor. I’m not sure the purpose of variable displacement (to adjust mechanical advantage between the sides is still my best guess) or why it’s deemed necessary on one side but not the other. Most of all, I’m still not sure what makes it bark. So that’s where I’m at.
Informative video.except...
On the 737 what he is pointing at, is not the PTU. That is the Flap Power Drive unit. If you want to see the PTU, it would be on the beam where that reservoir(standby reservoir in the video) is attached and go near the end of the beam on the other side.
You are absolutely correct. That was my fault because the video went out of sync when I did the voice over. The PTU is very small on the 737 and as you stated in the center keel beam.
Thanks a lot! This video really helps. Also could you advice the source of the picture on 1:00? Would like to dig into it as FCOM is of no help.
that picture comes from the Maint manuals, its not available in the FCOM, but you can also find it online.
Thank you very much!
You're welcome! Thank you for watching.
Love hearing the PTU, and comments from those not in the know thinking it's a dog in the cargo hold🤣🤣🤣
very good man, thanks
Thank you
The Airbus A320 sounds like an Electric Pallet Jack
Wait till you hear the brake fans 😅
I love this sound
This sound lives rent free in my head 🤣
Sounds like it’s eating itself. Do all PTU’s make this sound or is it only Airbus?
I was on a airbus and this was running continuously for about 5mins during decent, does that mean the plane was broken? Love your work!
It’s completely normal, sometimes the pumps need to compensate and this is why you hear the noise. Just because one of the engine driven pumps are not producing enough pressure. The power transfer unit will compensate.
Thanks@@StigAviation! Love your content, looking forward to the next shift video
Nice, thanks!
Thanks, I already listen but never seen a real pump working. Just drowning Pics , nice meet you eeal pump... 😂
Congratulations for clever video 📹.
Thanks 👍
When I first heard this sound as a kid I got scared thinking there was something was wrong with the engine lol
Now you know. It’s just how it functions 👍
Very cool!
🤙
Why advantage does the PTU bring? Why did Airbus make it get used on the ground while Boeing didn't?
Because Airbus has 3 independent systems and it acts as an extra redundancy system in case one engine driven pump fails. It can still provide hydraulic power to the failed system.
Always wondered what the hell that was but concluded it must be normal as the cabin crew never turned a hair. 😀
It's a disrespectful little monster!
🤣🤣🤣
can you describe what the switch indication says when its off vs on. Im unsure how the airbus overhead push botton switches indicate on/off
Would you please be specific in what switch you are speaking about
This was in reference about the Airbus pushbutton switches on the overhead panel when turning the PTU on and off. When pressed an "off" indication. Does that mean it's off or it needs to be pushed again to actually be off.
@@absters33 this is a great question, what you were referring to is actually the whole concept of dark flight deck, so what that means is, if the unit is off, the light will come on. This will illuminate and give notification and will be very visually apparent. Since we’re working off of a dark flight, deck concept, if all lights are Off that means everything is working properly. I hope that makes sense. But it is a very comical thing when your first encountering it. Turn off, push button off Legend comes on. 🤣🤣
@@StigAviation thank you for explaining it in great detail and what indication is to be expected in normal operations. Very knowledgeable and helpful thanks!
If there are three independent systems but only one PTU, are they really independent? If PTU fails what happens?
You just answered your own question tho. If all three systems are independent and the PTU is the cross connecting them. Even if you have the PTU fail you still have the independent systems working. You can even have 2 systems fail and still have control.
@@StigAviation I should have been clearer, if all 3 systems are connected to the PTU and it catastrophically fails (ruptures) could the pressure/fluid be lost in the aircraft or are there redundant valves that would close off.
@@EliseW-s8q all 3 systems are not connected to the PTU. Only green and yellow. But they are still independent and don’t intermix.
u said that each fluids do not go over each other, but how is it possible to supply another hydraulic without transferring the fluid to one another?
Variable displacement pump. It just transfers the pressure not the fluid.
To clarify a little, because I did some research after having the same question as you, there are two sides of the unit (green and yellow) that are hydraulically separate, but connected by a drive shaft. Each side of the PTU can be thought of as both a hydraulic motor and a hydraulic pump. If the green side has low pressure, the yellow side functions as a hydraulic motor, which spins the drive shaft, which drives the green side to function as a pump. If the yellow side has low pressure, it’s the same idea, mirrored; the green side functions as the motor, the yellow side as the pump.
Who let the PTU´s out? :D
lol
So small, but SO LOUD!!
Especially when the gear doors are down. You can hear it from very far
The should put sound dampers around it.
Really no need for that. It’s only on for a brief moment.
@@StigAviation unless you are on Spirit and they turn off the engines on the ramp waiting for a gate. Roof roof roof
@@PrestonelmerAnd how do they reach the gate if they turn off both engines?
woof woof
😅
why they shut down everything such as had tv and air-conditions ,light when they start the right engine on the Airbus A319 A320
They need to shut down air-conditioning for a small moment because the air is required to start the engine.
Hi sir i am come india to kuwait PTU sound noise is come
It's funny lol
A variable displacement unit coupled to a fixed displaced unit.
*me, a genius:* ahhhhhhh, I see, I see 🧐
😅 you should have seen my face when I was first learning about this back 20 years ago. 🤪
what is the different between A319 A320 dis airplane
320 is a longer aircraft. Systems are the same tho
ihere is that before when they star the right engine this song will cames up also i see all the light and tv will stop work and when the right engine start complite all the systerm get work
It’s because the generators are coming online from the engine, so there is a slight power interrupt.
Bro kindly make a video on 737 hydraulic system & compare it with A320 it will be an comparison of both technologies.
Like how 737 hydraulics get pressurized in case of one engine stop or start etc..
I will definitely work on that video.
it makes all sense now but there is still fog for me about how PTU make this noise.
When you have a variable displacement pump, it’s constantly trying to keep up with the pressure so hence you hear the continuous noise with pitching up and down in tone and you get that bark sound.
what did power transform unit on 787 song
This is a 321. 787 have different systems.
But you still didn’t explain what it is PTU, you said everything how it works but not what it is and why ot is in the plane.
Yes I did. Listen carefully. It’s a variable displacement pump
@@StigAviation Yes, the answer is for aircraft mechanics, they don't need explanations in these matters. I mean you didn't answer for normal people. Mechanics don't need explanations in these matters, on YT this type of information is sought by normal people, passengers of aircraft, not mechanics :) I know now what it is from other video of other creator. Cheers
@@mariodario9033 cheers. Glad you found it. And that’s the foundation of my videos. To make you research and find more information. Thank you for your intellectual ability to understand.
Who owns this video and if you do then someone posted your video in a short without tagging you
ua-cam.com/users/shortsPSyPGLDIkRE?si=oGb2dbVwSbbF1Hc-
@@cooluke29 I own this video because that me talking in it. Please share are the link of where you saw it and please report them if you could. Thank you
@@StigAviation unfortunately I don't believe I can report it as I'm not the owner of your video or anything and there's not a simple stolen video button to my knowledge
Schinner Courts
@@DarrellOrth-w1o ?
Oppenheimer drums
What?😅
Lang Islands
?
27 .8.2023
86805 Koby Manor
@@SherwoodAldrich what does that mean?
PTU is exactly why I cannot stand the Airbus a320 family. I have no problem with airplanes and their hydraulic noises but the A320 family's noises are extremely irritating. I love Airbus for its a350s and a380s but I try to avoid the a320s altogether (and yes, this includes the a321).
It’s not like the hydraulic system is constantly functioning, you’re not hearing that sound all the time, it’s only in the beginning and the end of the flight
@StigAviation the sound is still irritating though.
Do you think that’s annoying, wait till you hear what the brake fan sound like 🤣🤣🤣
Carmelo Spurs
?
Silly noisy European plane.
737 Max: silly crashing American plane
@@JustRememberWhoYoureWorkingFor don't forget the GTF engines that only last 5000 hours on wing, not 100,000 hours.
Pff, flown last week in a 16 year old a320 and an 8 year old 737-800 - the Boeing was way louder on the inside
Still like the 737 tho, but don’t be unfair
@@Alteshaus21I would rather hear B737's interior than A320'S horrible barking PTU.