My instructor made me do an exercise that consists of banking the sailplane left and right around 30 degrees without moving from the axis. I need to aim for a specific point, and start with the exercise. This is a coordination exercise but does it have a name? It's like a dutch roll but I need to stay in the roll axis without moving.
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$\begingroup$ I know it's an old question, and you'd have to look at other answers and see if they might invalidated by a change, but could you clarify either as a comment or an edit, whether you were supposed to keep the yaw string centered, or whether you were supposed to make rudder inputs to help hold the nose on the point even if they made yaw string go off center? Thanks. $\endgroup$– quiet flyerCommented Jul 28, 2019 at 17:08
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$\begingroup$ The string, if you do it perfectly, should be centered because you are perfectly coordinated, but as a student, I needed to add some rudder inputs in order to keep it kind of centered. You should move the stick and rudder all to one side, and when is banked enough, all the way the other side in one continuous movement. And so on, the string shouldn't move $\endgroup$– Santiago FloresCommented Apr 2, 2020 at 19:14
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7 Answers
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In the aerobatic community we would call that the beginning of an Aileron Roll.
It's harder than it looks.
answered Mar 5, 2018 at 15:13
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4$\begingroup$ But "Do a barrel roll" sounds more fun than "Do an aileron roll" $\endgroup$ Commented Mar 6, 2018 at 9:24
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5$\begingroup$ @workoverflow True, but a barrel roll is a different maneuver with significant change in pitch and altitude. $\endgroup$ Commented Mar 6, 2018 at 11:56
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2$\begingroup$ @workoverflow I get it. :P I saw the title and I was like "Wait a second, I know this... thanks, Game Theory!" $\endgroup$ Commented Mar 6, 2018 at 17:06
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$\begingroup$ While this is indeed how you start a roll in an aerobatic plane, doing this for rolling a glider will end up in a dive. It takes a little more to do a proper aileron roll in a glider! $\endgroup$ Commented Mar 6, 2018 at 20:17
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You do a roll change maneuver. In German it is a "Rollwechsel", and the time it takes to do this from -45° bank to 45° bank is an important measure for the agility of a glider. The maneuver is meant to teach you how to quickly change the direction of circling, and for most gliders it limits the minimum size of their vertical tail surface.
The European certification regulations for gliders demand in section CS 22.147:
Using an appropriate combination of controls it must be possible to reverse the direction of a turn with a 45° bank in the opposite direction within b/3 seconds (b is the span in metres) when the turns are made at a speed of 1·4 V$_{S1}$ with wing-flaps in the most positive en-route position, air brakes and, where applicable, landing gear retracted and without significant slip or skid.
Note the speed (v$_{S1}$ is the stall speed): The faster you fly, the easier it is. Since induced drag is highest at low speed, the adverse yaw resulting from the aileron deflection is impossible to overcome if you fly slowly. Glider designers try to make the tail just big enough so CS 22.147 can be fulfilled (the condition "without significant slip or skid" is crucial here!).
If you want to start an aileron roll this way: Please don't! It takes a little more to roll a glider properly.
answered Mar 5, 2018 at 19:01
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Here at the University we call it a "Perfect Roll", it is commonly used to assess the turning characteristics of an aircraft.
answered Mar 5, 2018 at 15:38
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In Argentina we used to call it "coordinación" (coordination).
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$\begingroup$ Hi Martin, that's exactly how my instructor call it, i'm training in Club de Planeadores La Plata. I haven't fly solo yet, but I fly without the intervention of the instructor, but I couldn't do the coordination excercise right. I'm tryining that skill with Condor Soaring Simulator so I can get it right next saturday. Any tip or sugestion? Thank you! $\endgroup$ Commented Mar 6, 2018 at 14:26
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$\begingroup$ Please remember that comments should be in English. $\endgroup$– FedericoCommented Mar 7, 2018 at 9:04
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It sounds like the process of doing a slow roll, though the pilot usually does the role until they are at the 180 mark, that is inverted.
answered Mar 5, 2018 at 17:46
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In addition to being (mistakenly) called a Dutch roll, I hear that maneuver called "rolling on a point" or "rolling on a heading." This is probably the most unambiguous description, as you are rolling the plane while using coordinated inputs to keep the heading constant.
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I've heard this maneuver called a "Dutch roll", but that phrase has other meanings too. It's arguable whether or not this maneuver is even truly possible, or is based on somewhat of an illusion. If the plane is banked, and you haven't "unloaded" the wing to zero G's, why would the flight path not start to curve to the side, pulling the nose off the point? To really do this perfectly it looks like you would have to use the rudder in a way that caused significant sideslip, but that was probably not your instructor's intention. (If it was, disregard all but the first sentence of this answer.)
answered Jul 27, 2019 at 21:38
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1$\begingroup$ The term Dutch roll is usually reserved for the swaying motion response to a step input in yaw or aileron. What OP describes sounds more like a coordinated turn. $\endgroup$– KoyovisCommented Jul 28, 2019 at 8:34