Strange Airplane NOISES! Boeing vs Airbus

hi everybody when I go to mentor and you're not a video podcast as always I hope you're doing absolutely fantastic today on the video guys we're going to be talking about the difference in sound between the Boeing 737 and the Airbus 320 what is that howling whining sound that you can hear from the Airbus 320s it's flying above you on approach and also that barking sound would you sometimes can hear as you're taxing out or taxiing in on the Airbus 320 this video is brought to you in cooperation with Nord VPN and as you can see I spend a lot of time travelling which means that I'm using a lot of public Wi-Fi and this is the reason why I let no DPN sponsor some of my videos because I know how it important is for me and for you to protect your data your identity geolocation on the Internet today right the way that know what VPN works is that they have several server scattered all over the globe and when you're using internet basically what anyone who intercepted your data will see is not 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I have the silences in this video because I'm getting so many questions about different noises okay and I fully understand that if you're a nervous flier and you're sitting there kind of you know listening to every single little sound and you hear something that's very very weird from the previous aircraft that you want you would want some kind of explanation to it so that's what we're gonna try to do today I'm going to give you three different sounds that we're going to be talking about with where there are some significant differences between these two aircraft types so make sure that you stay tuned to the end because I think that at least one of these is going to surprise you right so the first thing that we are going to talk about is the barking sound that you sometimes can hear on the Airbus 320 specifically when you are pushing back or when you're taxiing in about the park at the gate now I'm gonna give you a very quick overview of this but if you want a fantastic technical explanation of this well then I highly recommend you to check out captain joe's video about this specific subject but in order to understand it we're just gonna talk a little bit about the hydraulic systems okay what you need to understand is that on an aircraft we always have redundant systems this means that if a system is critical there's always another system that can jump in and take over the jobs of the other system if that would fail that is particularly important when it comes to the hydraulic systems and the reason for that is because the hydraulic systems do things like control our flight controls make sure that we can do normally steering when we're taxing on the ground make sure that we can retract and extend the landing gear and the flaps and the leading edge devices so these are some really really critical things that the aircraft need to have in order to fly safely so this means that if there is a problem with one of these systems well then the other system have to either take over the jobs or help restore that previous system and it's one we're talking about restoring the system that the PTU the power transfer unit comes into play on the Airbus 320 you basically have three hydraulic systems you have the green the yellow and the blue okay but what we're going to be talking about is the green and the yellow which is connected to the green is on the left hand side the number one engine and the yellow is on the number two engine these have very similar jobs okay so they operate generally when both engines are running at about 3,000 psi if one of the systems would drop down with about 500 psi so let's say it goes down to 2,500 psi well then the PTU will jump in and it is basically a hydraulic pump that is connected in between both systems and uses the system pressure from the steel operating system to start to help the system where the pressure is dropping okay so the fluids never mix with each other they just used in order to increase the pressure with me so far great this of course happens for example when the engines are being started so as you're pushing back and you start one engine you're gonna have a pressure building up on one side but not the other and in this case I'm not type rating on the 320 by the way I've understood that it's that it does a self-test and when it does that that's when you'll hear the pump starting stopping starting and stopping a few times and it sounds exactly like dog barking and the way that it's situated it's in the main wheel well babe it's the same on the 737 most of the hydraulic components are down there means that if you're sitting on the wings it just sounds like you have an angry dog barking just below you okay the same thing will happen on taxi even if the aircraft shuts down one engine and then at the gate shuts down the hydraulic pump to that engine as well then for a moment you will have the same thing happening where the PTU jumps in to try to restore pressure to the system where the pressure has dropped now what about the Boeing 737 done does that have a PTU in fact we do have a PTU on a 737 but the system design of the hydraulics is different so on the 737 system a and system B which we use they have different main jobs basically and they also have shared main jobs which means that when it comes to the flight controls we can actually easily kind of control the aircraft even if we lose one hydraulic system completely so there's no need for just flight controls to have a PT you however we might need a PT you when we have something that requires a lot of hydraulic fluid and an example of that is the driving of the outer slats and the leading edge devices so if we would take off and the hydraulic system B which is the one that is used to drive the outer slats and the leading F devices would suddenly drop in pressure well then our PT you would jump in and it would use hydraulic system a pressure to provide extra volume of pressure to hydraulic system B to drive these systems okay so this means that on the 737 you will never hear that barking sound because it's not the same design it will only jump in while we're airborne and when the flaps are between zero and well when the flaps are not up I should say and the system B drops below a limit value so that's why you will never hear it on the 707 but you will hear it on the Airbus 320 now the next thing that I want to talk about is the engine noise now this has something that I've gotten a lot of questions about and that why does the Airbus 320 have that high-pitched whining sound during takeoff [Music] and the Boeing 77 has a much kind of deeper growling sound when the engines are essentially the same and this is a fascinating thing actually because it is true the Airbus 320 and the Boeing 737 have essentially in most cases the same engine there are some air buses that uses the voice Royce engine as well but in most cases they use the cfm56 engine so Boeing 77 has the boy has the cfm56 - seven engines and the Airbus 320 family has the cfm56 - five either alpha or Bravo engine all right even though these are the same engines there are some fundamental differences the Airbus 320 has a very nice and long high landing gear so this means that CFM when they were creating the cfm56 5 Bravo engine they could make the engine as big as they wanted right they had no problems with ground clearance so the cfm56 - 5 Bravo is made the way its CFM wanted to make the engine but on the 737 they had a problem and this is something that we've talked about many many times in this channel and that is the fact that the 77 have a very low landing gear so when they created this new cfm56 - 7 engine for the next generation Angi they first of all had a problem with the ground clearance this is why you will see the the engine being flat at the bottom I did a special video about that you can check it out if you haven't seen it already and but also it meant that the fan diameter could not be the same on the on the Airbus 320 the fan diameter is about sixty eight point three inches and on the 737 it's about 61 inches so it's less fan diameter and of course you need to have the same efficiency on the engines the same kind of fuel burn things like that and because you don't have as much fan diameter on this seven that fan actually needs to spin about 10% quicker than on the Airbus 320 I mean the other thing that the 77 is different is that they have fewer families so on the cell on the cfm56 7 there's less fan blades and the families are wider now all of this creates together the same efficiency between the two engines but the sound will be different because when we set maximum takeoff trust and it's only really then that you will hear this massive difference in sound the tips of the of the fan blades will spin at supersonic speeds all right and since there are more fan blades on the Airbus than on the 737 that will spin at supersonic speeds there are more of that winding sound even though the speed on the fan blades are actually higher on the 737 since they're wider and shorter the difference in sound is there so this is essentially what you're hearing when we set maximum takeoff trust when the speed of the fan blades gets the highest possible well then you will also hear the difference in pitch in the sound you won't hear that as much when we can reduce the trust back to normal climb truss and when we're up at cruise because the speed of the fan blades are not as high and then the biggest amount of noise that you get from the engines is actually the exhaust gases that's what's causing most of the noise but when you can hear the tips that's also when you can hear the difference okay right so number three and this is truly fascinating when we're operating the 77 and the Airbus 320 we're sucking fuel out of the tanks alright easy enough when we're doing so we are creating a pressure difference inside of the fuel tanks and we also get that as for climbing and as we're descending and we don't really want a significant difference in in pressure as an air pressure inside of the tanks because you know that might cause either cavitation on the pumps us in the pumps can't suck in the the fuel or an overpressure which we don't want either and in order so of that we have overpressure protection systems that basically are holes to equalize the pressure inside of the tanks simply explaining the way that these holes look if you look at the Boeing 737 it kind of looks like a little triangular shaped Inlet form very similar to what you'll see on for example the ram air inlet or the exhausts sorry or the APU inlets and then you will have a little rectangular hole but on the Airbus 320 you have round holes four of them in the wings all right now this is where it becomes interesting because I'm sure that you've heard when as an Airbus 320 flies over you on approach as they're turning onto final for example that you can hear this high-pitched whining sound coming from it's very very particular and it comes only on the Airbus 320 family [Music] and it has to do with these fuel ones on the Airbus 320 it's called the fuel overpressure protection cavity or flop since they're round basically they are like the top of a bottle right if you imagine the top of a bottle and you know if you take a bottle and you put your mouth to it and you blow on it at a specific angle at some point you'll get that high-pitched sound coming out of the bottle well this is what you're getting from the from these foot valves on the Airbus 320 as well as the aircraft comes in at around 160 to 170 knots and approach the angle becomes perfect for the air to attack those holes and those holes basically become like four of these bottlenecks that is producing at high pitch sound and the sound is between 500 and 600 Hertz which is exactly where the human ear as is the most responsive the most sensitive so this is why you can hear it so clearly it's exactly the kind of noise that human ear is programmed to hear okay and it happens at exactly these speeds which is when pretty much we turn final to start to reduce the the speed down to taking the gear down the flaps 15 and so on all right now there are airlines out there who have noticed this and there is a fix for it so for example Lufthansa was among the first one to put little vortex generator just in front of the hole and by doing so the angle would never be correct and the hole would never appear so this is why you don't hear it as often anymore now this fix cost about $5,000 per aircraft and it doesn't really save any money it just the environmental kind of noise impact on the area around the airport so some airlines have decided to opt for this retrofit and some airlines have not okay so you are still able to hear this pitch to the next that you hear that high winding pitch and you look up you know which aircraft it is that's flying above you okay now if you have more questions about this maybe you're a nervous flier and you want other things to explain like why does it sound like that why does it look like that please send me a message all right you can either put in your comments here in the description of the video but if you really want to reach me then go into the free mentor of iation app all right I have the links in the description here below and just going to submit feedback and send me a message there that sends me an email directly okay if you want to talk to me directly just tag at mentor in the chat or any of the forums and you can even you know put up a suggestion for a new forum maybe strange aircraft noises or something like that and then we can have a specific discussion about what it is that you want to talk about but you should definitely get the app right if you want aviation news we push them out all the time when something happens and it's just a really really great group of people people are nervous people who love aviation professional pilots like myself and everyone is welcome alright so go and download the app now and just tag me let me know that you're there I hope that you've also subscribed to the channel now you know if you like videos like this or any type of videos about aviation subscribe and remember to highlight the little notification bell because if you don't then if I'm doing a spontaneous livestream from inside one of the simulators or in the cockpit when we have a long slot or something you'll miss that so make sure you both subscribe and highlight that button have an absolutely fantastic day wherever you are and I'll see you next time bye bye right guys I really hope that you like that if you want more content like that more aviation content well then check this out I hope that you have subscribed to the channel and that you've highlighted this is notification valve see you inside of the mentor aviation app and have an absolutely fantastic day bye-bye [Music] [Applause] [Music]

Channel: Mentour Pilot

Views: 172,916

Keywords: air travel, fear of flying, Airplane noises, Airplane barking, barking noise on aircraft, whining engine sound, aircraft whining, Airbus A320, Boeing 737, Boeing 737NG, Boeing 737MAX, Aviation facts, Aviation news, Nord VPN, Mentour pilot, Mentour, mentour pilot 737 max, mentour pilot take off, How to become a pilot, PTU, Aircraft approach, fear of flying help, nervous flyer tips, nervous flyers how to relax, nervous flyer help, traveling by plane tips, mentour pilot

Id: vuuBx9bzIqA

Length: 18min 35sec (1115 seconds)

Published: Fri Mar 06 2020