Video #5: Primary Flight Controls

Video #5: Looking at how the aircraft controls itself in pitch, roll and yaw, using the effects described in the other videos.

Script (with weird spellings and lots of comma’s to make the helpful American gentleman narrator speak properly!)

Well Hello There! Can you believe it? I have actually done five episodes of the profpilot flight training video series! I am quite surprised at my own dedication!

Before you watch this video, I suggest you watch all the previous ones, as they are all building up to this in a crescendo of majestic aeronautical majesty. You can do this by visiting my you tube channel page, or the profpilot blog. Alternatively, you can try and brave this all by itself, cold, and alone, without the warm, guiding hand of episodes one to four.

An aircraft primarily controls itself using its primary flight controls. These are the ailerons on the wings, the elevator on the horizontal stabileiser, and the rudder on the vertical staibleiser. You can pretty much think of all of these controls as aerofoils like this, which you might remember from the last episode. This can be the aileron, or elevator, or rudder, and when it moves, it alters the angle of attack, and therefore lift, of the control surface, moving the aircraft in the desired direction.

Let me show you what I mean.

An aircraft controls itself in roll using it’s ailerons, and you control these using the yoke in the cockpit. To roll left, you would move the yoke, left, and this will cause the left aileron, to move upwards, and the right aileron, to move downwards. From the last video, you should remember that an aileron moving upwards, decreases the angle of attack, and this will reduce the lift generated by the left wing. On the right wing, the aileron moves down, which increases the angle of attack, increasing the lift on the right wing. This imbalance of lift will cause the aircraft to roll to the left. Rolling to the right, just reverses everything. Heave the yoke right, and the left aileron goes down, which increases angle of attack, and lift, on the left wing. The Right aileron goes up, which decreases the angle of attack, and lift, on the right wing. So the aircraft will roll to the right!

Next, we will look at the elevator. In this picture we are looking at the aircraft from the side. Here are the ailerons, and here is the elevator, and again, the yoke. To climb, you will pull the yoke backwards, which will move the elevator upwards. Looking at our friendly aerofoil, we can see that this has the effect of decreasing the angle of attack so much that it actually causes lift to act downwards. This will push the tail down, and move the nose up, causing the aircraft to climb.
To descend, you will push the yoke forwards, the elevator will move down, the angle of attack at the tail will increase, and this has the effect of increasing the lift at the tail. The tail will be lifted, which will push down the nose, and the aircraft will descend.

Finally the rudder. Looking at the aircraft from above, you can think of the combination of the vertical stabileiser and rudder like a vertical wing. You control the rudder using the rudder pedals, or ruddles, which you operate using your feet. These are usually found in the cockpit and not floating six feet to the right of the aircraft, as they are, in this picture. Push the right pedal, and the rudder will move right. This will cause lift to act on the horizontal stabileiser in this direction, which will pull the tail over here. This yaws the aircraft to the right. If you push the left rudder pedal, the rudder will move left. Lift then pulls the tail over this way, and the movement of the tail causes the aircraft to yaw in the desired direction.

You can also have different set ups with the primary flight controls where one surface can combine two of the above. A good example of this is Concorde, the finest aircraft ever constructed. Mainly Because it was British. You can see it has no horizontal stabileiser, so there is nowhere for an elevator. It controls itself in pitch and in roll, using these elevons, which combine the functions of the elevator, and the ailerons, into one set of flight controls. They work by moving up and down together, like an elevator, for pitch control, or in opposite directions, to control in roll.

Similarly, you can get a V-tail, like this beechcraft bonanza, which combines the elevator and the rudder.

That’s it for now. See you next time when we will cover the fascinating subject of secondary flight controls!

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