How do gyroscopes work in planes

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Start Faster. Start Smarter. Sign up today Want the latest news, product updates and promotions? September 6, As a pilot, making good time is always great, but knowing where you are is more important. How Does a Directional Gyro Work?

Why Directional Gyros Fail Like all instruments, directional gyros can fail. It can be caused by any of the following factors: Normal wear due to time in service or not using the instrument for long periods of time. Adverse wear due to the instrument ingesting dirty air. This is caused by a missing or defective filter in a vacuum system.

Contamination by debris from a failed vacuum pump in a pressure system where the filter was inadequate, or the system was not purged correctly following pump failure. Impact damage due to a hard landing or rough handling of the gyro rotor and gimbal bearings. Directional Gyro Maintenance Tips To maintain directional gyro accuracy, the instruments require regular and delicate maintenance.

Here are eight key maintenance points for directional gyros: When you order a gyro, check it as soon as you receive it. The Russian Mir space station used 11 gyroscopes to keep its orientation to the sun , and the Hubble Space Telescope has a batch of navigational gyros as well.

Gyroscopic effects are also central to things like yo-yos and Frisbees! In this edition of HowStuffWorks , we will look at gyroscopes to understand why they are so useful in so many different places. You will also come to see the reason behind their very odd behavior!

If you have ever played with toy gyroscopes, you know that they can perform all sorts of interesting tricks. They can balance on string or a finger; they can resist motion about the spin axis in very odd ways; but the most interesting effect is called precession. This is the gravity-defying part of a gyroscope. The following video shows you the effects of precession using a bicycle wheel as a gyro:. The most amazing section of the video, and also the thing that is unbelievable about gyroscopes, is the part where the gyroscopic bicycle wheel is able to hang in the air like this:.

This mysterious effect is precession. In the general case, precession works like this: If you have a spinning gyroscope and you try to rotate its spin axis, the gyroscope will instead try to rotate about an axis at right angles to your force axis, like this:.

Why should a gyroscope display this behavior? It seems totally nonsensical that the bicycle wheel's axle can hang in the air like that. If you think about what is actually happening to the different sections of the gyroscope as it rotates, however, you can see that this behavior is completely normal! Let's look at two small sections of the gyroscope as it is rotating -- the top and the bottom, like this:.

When the force is applied to the axle, the section at the top of the gyroscope will try to move to the left, and the section at the bottom of the gyroscope will try to move to the right, as shown.

If the gyroscope is not spinning, then the wheel flops over, as shown in the video on the previous page. If the gyroscope is spinning, think about what happens to these two sections of the gyroscope: Newton's first law of motion states that a body in motion continues to move at a constant speed along a straight line unless acted upon by an unbalanced force. So the top point on the gyroscope is acted on by the force applied to the axle and begins to move toward the left.

It continues trying to move leftward because of Newton's first law of motion, but the gyro's spinning rotates it, like this:. This effect is the cause of precession. When the attitude indicator is in operation, gyroscopic rigidity maintains the horizon bar parallel to the natural horizon. When the pitch or bank attitude of the aircraft changes, the miniature aircraft, being fixed to the case, moves with it.

These movements of the instrument case with respect to the gyro are shown on the face of the instrument as pitch and bank attitude changes of the miniature aircraft with respect to the horizon bar. Air is sucked through the filter, then through passages in the rear pivot and inner gimbal ring, then into the housing, where it is directed against the rotor vanes through two openings on opposite sides of the rotor. The air then passes through four equally spaced ports in the lower part of the rotor housing and is sucked out into the vacuum pump or venturi tube.

The chamber containing the ports is the erecting device that returns the spin axis to its vertical alignment whenever a precessing force, such as friction, displaces the rotor from its horizontal plane. The four exhaust ports are each half-covered by a pendulous vane, which allows discharge of equal volumes of air through each port when the rotor is properly erected. Any tilting of the rotor disturbs the total balance of the pendulous vanes, tending to close one vane of an opposite pair while the opposite vane opens a corresponding amount.

The increase in air volume through the opening port exerts a precessing force on the rotor housing to erect the gyro, and the pendulous vanes return to a balanced condition. The limits of the instrument refer to the maximum rotation of the gimbals beyond which the gyro will tumble. As the rotor gimbal hits the stops, the rotor precesses abruptly, causing excessive friction and wear on the gimbals. The limits of more recently developed vacuum-driven attitude indicators exceed those given above.

Many gyros include a manual caging device, used to erect the rotor to its normal operating position prior to flight or after tumbling, and a flag to indicate that the gyro must be uncaged before use. Turning the caging knob prevents rotation of the gimbals and locks the rotor spin axis in its vertical position. Because the rotor is spinning as long as vacuum power is supplied, normal manoeuvring with the gyro caged wears the bearings unnecessarily.

Therefore, the instrument should be left uncaged in flight unless the limits are to be exceeded. In the caged position, the gyro is locked with the miniature aircraft showing level flight, regardless of aircraft attitude. When uncaged in flight, in any attitude other than level flight, the gyro will tend to remain in an unlevel plane of rotation with the erecting mechanism attempting to restore the rotor to a horizontal plane.

Therefore, should it be necessary to uncage the gyro in flight, the actual aircraft attitude must be identical to the caged attitude that is, straight and level , otherwise, the instrument will show false indications when first uncaged. Errors in the indications presented on the attitude indicator will result from any factor that prevents the vacuum system from operating within the design suction limits, or from any force that disturbs the free rotation of the gyro at design speed.

Some errors are attributable to manufacturing and maintenance. These include poorly balanced components, clogged filters, improperly adjusted valves, and pump malfunction. Such errors can be minimized by proper installation and inspection. Other errors, inherent in the construction of the instrument, are caused by friction and worn parts.

These errors, resulting in erratic precession and failure of the instrument to maintain accurate indications, increase with the life of the instrument.