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The Three Axes of an Airplane

Three axes of an airplaneAn airplane has three (3) axes about / around which it can move in flight.

In the image above, you are seeing all three of these axes:
Longitudinal axis: from the nose to the tail of the airplane
Lateral axis: from wingtip to wingtip
Vertical axis: from the bottom of the airplane to the top of the airplane

Each of these three axes meet at the center of gravity (CG) of the plane. The CG is the point at which the airplane would balance if you could lift it up by an imaginary string that attached at that exact point. You can think of the CG also as a kind of fulcrum (like on a teeter-totter) that the plane rolls and pitches around.

Anyway, back to the axes of the plane. Here's what you need to know about them and why they are important.

The Longitudinal axis (the one that runs the length of the plane from nose to tail) is the axis that stays fixed when the airplane "rolls" or "banks" - such as in a turn. In this case, the plane is rotating "about" or "around" the longitudinal axis. This is caused by the airplane's ailerons, which change the camber of the wing and increase its lift on one side,making the wing climb, and spoil the lift on the other side, making the wing drop.

The Lateral axis (the one that runs from wingtip to wingtip) stays fixed when the plane "pitches" - raising or lowering the nose (such as for a climb or a descent). The plane pitches about the lateral axis. This is done using the airplane's elevators. The elevators change the shape of the horizontal stabilizer, causing it to decrease lift (tail goes down, nose goes up) or increase lift (tail goes up, nose goes down). Some aircraft have "stabilators," where the entire horizontal surface moves instead of just the elevator, but the concept (and result) is still the same.

The last one is the Vertical axis, which runs vertically (up and down) through the fuselage. This one stays fixed when the airplane "yaws" - meaning the nose moves left or right. When the plane yaws, it is turning about the vertical axis. This is like turning a car (the car doesn't roll or pitch, it just turns, or "yaws"). This can be done by moving the rudder, which is the movable control surface on the vertical stabilizer (the upright portion of the tail). Moving the rudder right puts it into the airflow and pushes the tail to the left (and the nose to the right). Generally, the rudder is used in tandem with the ailerons to coordinate an airplane's turns, because when an airplane banks, there is a change in drag, making the nose want to move away from the turn initially. the rudder is used to "yaw" the nose the right way and keep the whole plane moving in the direction the pilot (you) want it to go.

It is possible to move an airplane about all three axes at one time, and rarely does an airplane move about just one at a time. You, as the pilot in command, will use all the control surfaces to move the plane about all of its axes and make it do what you want it to do.


Do you have any questions about the three axes of an airplane, or do you have any hints or tricks or stories to share that relate to them? Leave a comment and tell us all about it!

Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.

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Preflight – Step 2: Exterior (Wing)

Piper Cherokee

In the first part of this series, Preflight: Step 1 - The Cockpit Check, we talked about starting your preflight in the cockpit.

But the exterior check in step 2 actually starts even before step one.  Confused?  Let me explain:

Every preflight really should begin as you are walking out to the plane.  Or - if you're lucky, as you enter your hangar, before you even touch the plane at all.

Is the plane leaning to one side or the other?  Does it look very tail-low or tail-high? Are there puddles of fluid under the engine cowling or at the main gear?  Are there stains on the wings or anything new that you never noticed before? Do you always lock the plane, but the door was open when you first look?  If you don't own your plane, some of the above things may not apply, but even if you rent, there are probably processes and patterns where if something is different, you'll notice.  If you ever have a question, grab a flight instructor and ask!

After this first look, do your cockpit check, and when that is complete, move on to the exterior check!  Because the exterior check is the longest part of the preflight, we'll break it up into 3 sections - wing, tail, and engine.

NOTE: the specifics in this series apply to Cessna 172 aircraft, as that is what I instruct in most – in any case, always use the Pilot Operating Handbook (POH) for your aircraft to confirm that you have not missed anything on your preflight!

I tell my students to step forward and out, putting them in front of the plane, to the left of the engine cowling.  From here, they can start by checking the cowling itself for loose or missing screws, checking the static port to make sure it is not blocked or covered by anything. This is also a good vantage point to look at the wind screen - is it dirty? Does it have bugs splattered all over it? Clean it before you go!

Now look up - at the leading edge of the wing at the wing root.  There is probably a vent here - check to make sure it is not blocked. Now run your hand along the leading edge of the left wing, looking for big dents that might change the wing's ability to create lift.  As you move from the wing root toward the wing tip, you'll run past the pitot tube - check all the openings/vents to make sure they are not blocked by anything (including a pitot tube cover).  Keep going to reach the stall warning opening - check to make sure it is not blocked.  If you have a suction tool, you can test whether it is working or not as well.  Keep moving toward the wing tip and check to make sure that the fuel tank vent is also not blocked, and the fairing for the wing strut is secure and in relatively good shape.  While checking all of this and the leading edge, you should also be checking the bottom of the wing for loose rivets or loose or missing inspection covers, or anything else out of the ordinary.

Once at the wingtip, just check the plastic tip cover for any major cracks (you may find small cracks that have been stop drilled, but those are okay), and make sure it is secure.  Now on to the trailing edge.

You removed the control lock during the cockpit check, right? If not - go remove it now, because we're going to check the ailerons.  First, push the left aileron up, and look over to the one on the right wing to make sure it is down. Also, if you can see it, check that the yoke turns toward the left while the left aileron is up (the yokes should always turn toward the up aileron).  Now push the left aileron down, and check the other aileron (which should be up now), and the yokes (which should be turned to the right now - toward the up aileron).

Now, hold the aileron up with one hand, and duck under the wing and turn around so you can look between the wing and aileron at the following:

  1. There should be three counterweights on the outside of the aileron, securely attached
  2. Three hinges, all of which should have secure bolts and safety wires, and none of which should be cracked or broken in any way.
  3. A pushrod, which will rotate a little, but the bolt should be secure - it should not be loosened or turned by your fingers.

Make sure you hold the aileron up with one hand and do these checks with the other! Even if the aileron seems to stay up on its own, even a slight wind could push it down and pinch your fingers - consider this the voice of experience telling you that THIS HURTS. Avoid this by learning from my mistake and holding the aileron up with one hand anytime you have your fingers in the gap between the wing and aileron!

You may also see one or two wires coming out of the back of the aileron - these are called static wicks, and they help protect the airplane and its electronics from static electricity and/or lightning strikes.  Just make sure that if the plane has any, that they are all there, secure, and in good shape.

Now continue moving inboard to check the left flap.  Push on it - it will give a little - maybe an inch or so.  Too much is a cause for concern.  If you are in doubt, ask your instructor or a mechanic.  Check the tracks - there will be two (one on each side of the flap).  Look at the rollers for cracking, wear, or other issues (including being gone completely!).  The tracks should have a little grease on them - not necessarily sopping in grease, but enough to let the rollers move smoothly.  Check the pushrod on the flap just like you did with the aileron.

Now that we've completed the left wing, let's check the left main gear.  Is it fully inflated? Are there bald or flat spots or belts showing from excessive wear?  Now roll the plane forward or back to see under the tire, too.  What about the brakes? Is there fluid leaking? Check the rotor for wear, and both pads (each pad should be at least as thick as two quarters pressed together).  Check the brake line for security, and the "bolt" to make sure it is not loose.

Once you are done checking the main gear, it's time to move back toward the empennage (tail). We'll talk about the tail in the next post in the series!


Do you have anything to add to the preflight series so far? Add your tips to the checklist by leaving a comment below!

Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.

Preflight Series:
Preflight Step 1: The Cockpit Check
Preflight Step 2: Exterior (Wing)
Preflight Step 2: Exterior (Tail)
Preflight Step 2: Exterior (Engine)
Preflight Step 3: Fuel

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Learn to Fly: What it Looks Like – Aileron

Smart Flight Training's goal is to take the mystery out of aviation for those who want to learn to fly by discussing flight training terms and showing pictures and video where we can.

We hope that reading about, seeing, and watching aviation in action will help you learn to fly more efficiently - saving you money at your flight school and during all of your flight training!

This Wednesday, we will take a look at one of the "control surfaces" of you flight training aircraft, the aileron.

Ailerons

An aileron (French for "little wing") is a movable flap on the wing of an airplane used to control the plane's side-to-side movements. Ailerons cause one wing tip to move up and the other wing tip to move down, helping a plane turn. To bank to the left, a pilot must raise the left aileron and lower the right aileron. Ailerons are located on the back of the wing (known as the "trailing edge") and near the wing tips.

Aileron Image

All ailerons work the same way, whether you are a student learning to fly a light sport aircraft or an airline pilot flying a Boeing 747.

As you continue to learn to fly, you'll find out more than you ever thought you would want to know about ailerons, including their effect on the yaw of an aircraft in addition to the roll, and what you can do if you lose the ability to control the ailerons in flight.

But all of that is for a future flight training post! Until then, enjoy this YouTube video of ailerons at work... Notice that the ailerons do not have to move very much to do their job!


Learn to fly faster and smarter with Smart Flight Training: join our mailing list and get involved in the community by leaving a comment below!

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