What is a "Dutch Roll"?!

hi everybody welcome to mentor and yet 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 ducks roll how Dutch is it actually why does it happen can it be dangerous and what is your temper this video is brought to you in cooperation with brilliant dot-org now we're in the middle of the holiday season so why don't you gift the gift of knowledge of curiosity to someone if you use this link here below you'll get 20% off the annual fee of brilliant and by giving this you will not be giving something that is materialistic or that hurts the environment instead it will be something that someone can actually use so check it out [Music] right guys so we're gonna be talking about the Dutch role now doctor Elizaveta thing okay and in order to understand that you really do need to understand quite a lot about aerodynamics but don't worry I'm here to explain it in a way that you will actually understand it okay in order to understand that we need to start with some basic aerodynamics so the aircraft is moving around three different axis you might have heard of these before you have the pitch axis which pitches the aircraft's nose up and down you have the roll axis where we use the aileron and the spoilers to roll the aircraft like this and then you have the U axis that's where you use the rudder to move it around your axis in this motion like that now these three axes we are constantly combining to make sure that the aircraft is flown in a nice safe and comfortable way but there's also something called stability okay stability easily explained is the aircraft's ability to return after a disturbance so for example in the roll axis if the aircraft would suddenly be rolled to the right we need it what we wanted to be able to come back to its wings level state okay the same goes for all axis if there is a sudden disturbance if it is stable enough it will after a few oscillations get back to its natural kind of wings level straight ahead flight now when the aircraft manufacturers builds an aircraft they want the aircraft to have this stability along all of the axis but the stability cannot be too strong because if it's too stable but then the aircraft will not be able to turn or will struggle to turn right but it cannot be unstable either because then it's gonna be extremely hard to hand fly it an example of that is for example fighter jets they are built knowingly either unstable or new the stable in order to be able to do very quick maneuvers but in order to be able to fly those fighter jets especially the more modern ones you need to have super computers that's constantly calculating what to do and well how to interpret the inputs of the pilot to make sure that the aircraft doesn't lose control okay now air transport category aircraft they tend to be fairly stable platforms but the stability is not equal in all different role and yaw and pitch movements and that's why we can get ducks roll so doctor all tends to happen at higher altitudes and they happen because we have swept wings on the on the end for example a Boeing 737 I'll give you an example let's say that I am sitting I'm flying the aircraft manually for whatever reason and I move over to take something off the center panel and I accidentally hit the yoke alright so the aircraft start rolling towards the right now if no other inputs are made if the aircraft rolls over to the right it will automatically since the lift vector from the wings always goes straight up from the wings if you roll your lift vector will then move towards your right in that case which will give you a side words momentum as well so as the aircraft starts rolling it also introduces a slight yo because of that that side vector right now as the aircraft starts rolling to the right and now yoing to the right this means that the relative flow of air will now come from the right slightly and when you have swept wing aircraft the only part of the wing that is creating lift is the wing where the wind goes perpendicular over the cord of the wing okay so this means that as the aircraft is now rolling and yawing the wind will come more straight on to the right wing the downward wing then on the left side and since the angle is now on the right wing then on the left wing the right wing will be creating more lift and that will counteract the roll so it's stable it's that's the stability coming in it's being disturbed to the right because it's now you're owing like that it is now coming back into its original state so it's roll stable but there is an issue here if you know you're a dynamic you know that any time that we take out more lifts from one wing it will also create more drag and that's what's going to happen so as the aircraft is now rolling to the right and the right wing is starting to make more lift in order to get back up again it's creating more drag and the drag will force the aircraft to you're even more ok so the aircraft is now rolling going more and as it's rowing more that a relative wind that was talking about because of the yaw is now creating an angle of attack on the fin as well now the fin works just like a wing so if you get an angle of attack onto the fin it will also create lift so that is the your stability coming in okay so now it's rolling it's going the lift is being created on the right hand side of the fin which is counteracting the yo and the role is being counteracted so this is how stability is working right the problem here of course is that the Royall stability is much more powerful than your stability wings are bigger the forces are bigger so that initial increase of lift tends to go over so it doesn't just go back to level flight it over rolls it a little bit and the your that comes from the from the fin is a little bit too little a little bit too late so it always comes in a bit later which means that the aircraft will now be rolling over to the left instead the same thing will happen it will your it will create lift on the fin it will roll back again and each one of these oscillation we become smaller and smaller but the oscillation itself is quite uncomfortable because as you can imagine the aircraft is rolling rolling rolling going like that as its oscillating back and that movement that is the Dutch roll okay you mid mid so far good so why would a movement like that be called a duct roll well actually this is fascinating it goes back to the beginning of the 20th century where where we started to use swept wing aircraft larger transport category aircraft and they the aerodynamics and the people who were working with the aerodynamics quite quickly understood that this would happen and they needed a word to to kind of explain this phenomenon this movement and the easiest way when we humans talk to each other is to explain something new with something that we know something that we understand and the moosh motion was very similar to what you see from a skater someone who's skating of course the most famous skaters come came from Holland Dutch so they said well it looks like a Dutch skater doesn't it coming rolling from side to side like this hence the word doctor all came about and that's where it came from so what can we do about this then well this is where the your damper comes in right the gyro damper is basically a computer called the stall management your damper computer that sits and it feels the aircraft movement it feels the roll feels the your and it inputs that information to the rudder and automatically moves the rudder to counteract this motion so if the store management you're donk but computer feels a movement disturbance and roll well then it will automatically and quickly move the rudder in order to stabilize the aircraft ok so instead of having the rudder or the effect of the fin coming in too little too late the rudder is now coming in doing exactly what it should which brings the aircraft back into stable flight immediately it works with tiny little inputs all the time as we were flying along our route right we on the older aircraft we actually had a little your damper indicator that showed how much the rudder was movement but to be honest you could sit in you can stare at a thing and you would only see some small small small variations because if you input rather early enough when you have a disturbance it's basically nothing you as a passenger will never notice it we the pilot never noticed it the secondary thing that the yaw damper Dov's e'en in the 737 is it coordinates the terms so on smaller aircraft when you are flying along and you're turning the pilots need to input rudder manually if you don't once again if you just roll you are not going to get a nice clean turn you're going to get a roll and the yaw that comes often it's gonna feel nasty if you're a passenger you will feel like you're being pushed out to watch the side of the aircraft or if you're using too much rather it will feel like you're being pushed inwards toward the aircraft but if you do the perfectly coordinated turn you put enough aileron in and enough rudder in it'll be a beautiful turn and if you're sitting holding a cup of Coca Cola or coffee or whatever you will not feel a thing if you just feel like you're sitting with 1g straight down looking out as the aircraft is banking maybe 30 degrees this is what the Euro damper does for us right in a in a Boeing we never need to put another in a so turning we're only turning yoke and the yaw damper feels so much returning and it's putting in the perfect amount of rudder to get a perfectly coordinated turn it also does something called gust damping which is similar so it's feeling if we're flying along and we get a gust disturbance for whatever reason it imposes much rather needed in order to make sure that the aircraft stays stabilized and flying the way it should so the gyro dumper is a very handy little thing to have but it's not crucial okay it is handled by one of the hydraulic systems if it fails if the hydraulic systems fail for example the yaw damper will fail as well but the aircraft is perfectly able to fly without the yaw damper just feel a little bit more uncomfortable we do have a secondary standby your damper that comes in if we would use all hydraulics and that is because if we would lose all hydraulics then it will be really hard to control the aircraft and we do need the standby hydraulic system to come in and help us do the turning and maneuvering of the aircraft okay so is the duct roll dangerous the answer to that is no that roll in itself is not dangerous okay it is a perfectly normal movement if the aircraft is well constructed than it should oscillate itself out and if you just leave it alone the aircraft will after a few oscillations return to stable flight again but there has been incidents involving ducks roll and the reason to that tends to be that the pilots are making improper inputs of the rudder in order to counteract the perceived nut roll the balance system that we have that humans have is not sensitive enough to feel when this doctor all is starting and this means that we not unlike the fin itself is going to put in the impact input too late and if you do that you're just going to make the Ducks all worse now our very famous example of that was a delivery flight that happened back in 1959 where a Boeing 707 was being ferried to the customer from from Boeing and the delivery crew was scheduled to do a flight test or delivery test that they always do part of that test was turning off the yaw damper now when they turned off the gyro damper the the aircraft was in the controls of a fairly inexperienced pilot and the doctor all started the pilot started counteracting but like I said was too late and too much inputs so the doctor old got worse and worse and apps that movement got worse the pilot inputted more and more opposite rudder and F at a certain point there was so much rudder inputs that the g-forces ripped three out of the four engines off the wings of the aircraft the aircraft had to make an emergency landing on a riverbed and four out of the eight people on board lost their lives so that was a very tragic incident but once again that was not due today the duct roll in itself it was because of the improper handling of the duct roll now we're a more recent event happened back in 2005 to an Air Transat flight 961 I think it was where they suffered a rudder failure at altitude and because the rudder was not working now when the doctrine started there was no way to counteract it and the doctor'll created so much movement that one of the cabin crew got injured as part of it but the aircraft managed to get down and landed safely at the destination anyway so there has been some incident involving dr. all but generally in itself the Dutch roll is just a phenomenon that is based on the aerodynamics of the aircraft the fundamentals of the aircraft and as you can see understanding the physics behind that understanding how and why an aircraft is stable in the rolled axis or in your axis and how those forces interact with each other is crucial for you in order to understand your ATPL theory that you will be tested on as part of your flight training ok and this is why I am so happy and so proud to be sponsored by brilliant or because this is exactly the kind of things that you will understand if you go through their courses they have a lot of interactive courses in for example how to do problem solving in a fun and interactive way they will show you how to solve it in case you can't solve it by yourself and there's also a mathematics kind of course which brings you from very fundamental mathematics throughout all the way up to very advanced mathematics so if you need to brush up on that maybe it's been a while like in my case since you were actually studying it in school well then using brilliant is a brilliant way of doing exactly that and like I was saying in the beginning of the video if you're struggling to come up with a good gift to someone maybe your uncle or aunt or someone who's always you know solving Sudoku puzzles or things like that well in that case go down here use the link below the link below it is brilliant old org slash mentor pilot will give you 20% off the annual fee of brilliant and I'm sure that this is something that they will appreciate rather than something must really stick have an absolutely fantastic day wherever you are guys and like always go into the mentor aviation app there's also links down here to the app it's absolutely free to download it it's a great way to keeping up with aviation news we're pushing up news there will be news constantly coming up and obviously you can talk to me or other real pilots in there as well as aviation enthusiasts have an absolutely fantastic day 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 radiation content but then check this out I hope that you have subscribed to the channel and that you've highlights little notification valve see you inside of the mentor aviation up and have an absolutely fantastic day bye-bye [Music]

Channel: Mentour Pilot

Views: 213,615

Keywords: mentour pilot, mentour pilot 737 max, mentour pilot turbulence, dutch roll explained, dutch rolls flying, dutch roll airplane, dutch roll tendency, dutch roll maneuver, dutch roll video, dutch roll and yaw damper, yaw damper, yaw damper explained, yaw damper function, yaw damper failure, yaw damper switch 737, yaw damper system in aircraft, aviation fun facts, aviation fact, nervous flyer tips, nervous flyer help, boeing 737 max, boeing 737-800, aerodynamics, pilot, avgeek

Id: z2J_LUDWioA

Length: 17min 41sec (1061 seconds)

Published: Fri Dec 13 2019