hey guys and welcome today on atpl Theory after a long Hiatus we're going to be talking about Dutch roll your dampers and the effects they have on aircraft so first of all what is Dutch roll well a Dutch roll is an out of phase turn essentially as we know when we roll an aircraft it creates an opposite Y and when we you're an aircraft it creates an opposite role uh so this combination is what we call an outter phase turn and what can cause Dutch roll on some aircraft now some aircraft suffer from Dutch roll naturally it's also performed as an acrobatic maneuver Dutch roll is named after a pair of Dutch ice skaters you can search for videos online I don't think it looks anything like what a somebody compared their movement to the movement of a plane once I don't think it looks anything like it but that's just my opinion so going back to one of my other videos which I talked about stability which feel free to search for it in my videos and have a good look at it we can go talk about lateral stability and directional stability again and why one being weaker or stronger than the other causes Dutch roll so the best way to describe and to explain Dutch roll to you is to give you an example which is what I'm going to do below now in my example I'm going to talk about a slight sweat back wing with a dihedral that's the most common type of aircraft that suffer Dutch roll problems so let's say we start an uncoordinated roll to the right as we roll to the right our aircraft is actually going to S slip to the right also now what that means is that our air flow is going to now come from the right because we are side slipping down into into that air flow now on a slightly sweat back Wing that's going to mean that the air flow is going to be hitting the right wing more head on which is going to generate as we know more lift so now we're going to have slightly more lift on the right wing than we will on the left wing and that brings us on to the next phase of du roll so if we have more lift on the right wing this is actually going to cause that dihedral effect it's actually going to want to lift that right wing up and roll Wings level again that comes from the positive lateral stability there which talked about in another video more lift also equals more drag now if we have more drag on this part of the aircraft it's actually going to y or pull that nose to the right so we're going to Y right that brings us onto the next stage of Dutch roll so meanwhile in the tail part of the aircraft as the nose is now to the right the air flow is suddenly coming slightly from the left so it's hting that tail on the left side hence generating lift towards the right you can think of it as a wing essentially it has more angle of attack uh so the lift is in that direction which is going to pull the tail to the right now not the nose so it's going to yure the aircraft to the left so that your moment to the left is now going to bring us on to the next stage now this is where the problems arise you see the aircraft tries to stabilize itself as the right wing drops that dihedral effect creates a little bit of extra lift tries to correct it because on a big aircraft the wings are much more stable than the vertical stabilizer essentially the lateral stability is much stronger than the directional stability so while the tail is trying to line up the nose get it back to where it was that has caused an overbank to the left if we Bank left we get left side slip and you can see it's gone full circle so we started right side slip now we've ended up left side slip so you can now replicate all these three steps from the opposite side so that swinging motion that rolling motion that's what's called Dutch roll where it can't quite recover itself now most modern aircraft have what we call Y dampers and what a y damper does is move the rudder very quickly much more quickly and much more reactive than a human could even sense to correct that Dutch roll so that we don't get into that series of fluctuations so as we roll the aircraft the Y damper system automatically inputs the correct amount of Rudder to stop generating any Dutch roll now if the Y damper was inoperative for any reason the best technique would be to almost leave the aircraft alone and let it kind of settle as it is inherently positively stable and which if we go back to our stability video you'll see that it essentially will get back to its original position even if it might oscillate a little bit getting to that point some older aircraft could be negatively stable and would not recover most modern aircraft I say would recover if the Y dampo was in operative so I hope that's cleared up any doubts you might have had on Dutch roll and what your damper in an aircraft does please uh like share and subscribe more videos on the way all the best see you next time for