Video #6: Secondary Flight Controls

Been quiet on here recently, here’s why: video time again! Oh joyous day.

Video 6 looks at how pilots use secondary flight controls to make their lives easier, and less crashy when flying around.

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

[Beginning waffle here - sorry, deleted the text file].

Also, thanks very much for the kindly comments you have all been leaving on the other videos.

As usual I have verbal dire reared everywhere to start the video. Secondary Flight Controls are why you are watching, so I guess I’d better start talking about that.

Secondary Flight Controls are basically any flying control, which are not the ailerons, elevator or rudder, which were discussed lovingly in the last video.

The first secondary flight control we will look at is elevator trim. During different stages of one flight, there will be varying loads on the flying controls. For instance, say you are entering the circuit after cruising along merrily. There are many people around and you might be uncomfortably close to the aircraft in front. Why not go into slow flight to create some space?

In slow flight, you are going slow. Lift Formula Time Again! Your velocity is less, and in order to maintain lift, you must increase angle of attack to make up for this. You would achieve this by pulling back on the yoke, and as you will remember from episode 5, this will raise the nose, increasing the angle of attack at the wings, like we wanted. Now, let that slow, annoying bi-plane get away from you.

To maintain this new attitude, you will now need to maintain back pressure on the yoke, because If you didn’t, bad things would happen. But holding a yoke as it is straining to get out of your hands would get very annoying, fatiguing, and may send you insane, which would revoke your medical license. The function of the elevator trim is to take the pressure for you! Thanks, kindly elevator trim!

The elevator trim tab is attached to the trailing edge of the elevator. This smaller control surface is controlled in the cockpit, and it can move independently of the elevator. To trim the aircraft nose up, you would operate the trim control, and this would move the trim tab downwards on the elevator. What happens when a control surface is deflected downwards? It increases lift. The trim tab creating lift will then drag the elevator upwards, and we know what happens when the elevator moves upwards from episode 5. The nose will rise.

It is worth pointing out that the trim is not used to control the aircraft, merely to take your pressure from the yoke, once you have established the airspeed and attitude that you want. You can remember this as pitch, Power, Trim.

In addition to elevator trim, you can also get rudder trim, and aileron trim. These are usually found on larger aircraft though, so for the moment you probably don’t need to worry about that.
Another secondary flight control we can look at are the flaps. These are on the trailing edge of the wing, and can be extended or retracted using controls in the cockpit. They operate symmetrically on both wings, as opposed to the ailerons which operate in opposites. There are lots of different types of flap, but they all work in fundamentally in the same way. They increase the Coefficient of Lift, meaning that we can fly slower while maintaining the same amount of lift. Having big flappy things on the back of your wing also increases drag, helping us to slow down.

At first, lowering the flaps results in a large rise in lift, with a smaller rise in drag. Lots of lift and little drag is exactly what we want at take-off, which is why on some aircraft, a low flap setting is used for this. However, as the flaps are further lowered, drag will increase a lot more than lift, hence the reason that they are fully lowered at the landing stage of flight.

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One Response to “Video #6: Secondary Flight Controls”

  1. Stokie81 says:

    These videos are great!! Simple, funny and informative Finding these really useful when thinking about becoming a pilot. Thanks

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