11.5.2 Instruments- Gyroscopes Flashcards by Alex Hooker

What indicators use gyros?

Attitude indicator
Vertical Gyros
Directional Gyro
Rate gyro

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What does a universally mounted gyro consist of?

Rotor, inner and outer gimbals mounted in a frame

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What does gyro stability depend on?

Mass
Rotational speed
Distance between axis and COM

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What is the XX axis?

Spinning

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What is the YY axis?

Tilting

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What is the ZZ axis?

Veering

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What dictates the degrees of freedom?

Number of gimbals

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What happens if you apply a force to the direction of the gyro axis?

Will cause it to move in that direction, but will not change the direction of the gyro axis.

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What is an AI?

Attitude Indicator- position to horizon

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What is a VG?

Vertical Gyro- provides indication for Attitude Director Indicator

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What is a DG?

Directional Gyro- signal for Horizontal Situation Indicator and RMI

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What gyros do modern glass cockpit aircraft use?

Electronic gyros such as laser gyros.

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What speed must gyros rotate at to have stability?

22,000 RPM

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What three ways can a gyro be classified?

Degrees of freedom
Spin axis orientation
Type

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How is the degrees of freedom dictated?

Number of gimbals

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When is classification by spin axis orientation used?

If the gyro is mounted with its spin axis either horizontally or vertically.

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What is a free (space) gyro?

Has two degrees of freedom in three axis.

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What is a tied gyro?

Similar to a free gyro but an external restriction is applied which controls the orientation of the spin axis.

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Which indicator uses a tied gyro?

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What is an earth gyro?

The spin axis is constrained by the earths gravity, it has two degrees of freedom.

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What instrument uses an earth gyro?

Attitude Indicator

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What is an earth gyro a sub type of?

Tied Gyro

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What is a rate gyro?

One degree of freedom, constrained to measure the rate of rotation in one plane.

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What are rate gyros used for?

Turn coordination.

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What two properties of a rotor rely on its angular momentum?

Rigidity and Precession

What is a displacement gyro?

Three axis and two degrees of freedom, the rotor orbits the x axis.

What is rigidity?

A gyroscopes ability to maintain its axis while pointing in a fixed direction.

What does rigidity cause?

A gyros axis of rotation to maintain a fixed direction in space if no force is applied.

What three factors effect rigidity?

Mass of rotor Speed of rotation Distance at which mass acts from centre.

Why are electrically driven gyros designed to use AC?

To avoid commutators and brush gear that need constant servicing.

The further the mass of the rotor from the axis of spin the ......? rigidity will be for the given speed?

Greater

What does a dished rotor exhibit?

Greater rigidity than a uniform wheel of the same design.

What is precession?

Applying a force that tries to tilt the gyro axis causes the gyro to react by shifting 90 degrees.

When precession is considered, if a aircraft tail is lifted what happens to the nose?

It turns left.

Is precession inversely proportional to the rotor speed?

Yes

What is the rate of precession formula?

Torque divided by inertia x speed

What is gyro wander?

Any deviation from a fixed direction when force is applied to the spin axis.

What two types of wander are there?

Drift and topple

What is gyro drift?

Occurs when the spin axis moves in a horizontal plane.

What is gyro topple?

Occurs when the spin axis moves in a vertical plane.

What is the name for severe and, usually, rapid misalignment when a gimbal limit stop is reached?

Topple

What causes real wander?

Result of any force that causes the gyro to precess.

What is real wander?

Actual movement of the spin axis caused by engineering imperfections, such as friction and unbalance.

Real drift occurs in which axis?

Vertical

Real topple occurs in which axis?

Horizontal

What is the rate of apparent drift at the poles?

15 degrees an hour

What is the formula for apparent drift?

15 degrees x the sine of latitude divided by hour

What is the formula for apparent topple?

15 degrees x cosine of latitude divided by hour

What ensures the rate of apparent drift is accurate?

If the gyro is at a fixed location.

How is the total effect of topple eliminated?

Erection system

How does the erection system work?

Uses the Earth’s gravity as a reference signal; this is detected using a moving mass, e.g., a pendulum, or liquid level switches.

What two categories of gyro wander fall under real wander?

Real drift/topple.

The attitude indicator gyro indicates what around the longitudinal axis?

Degree of bank

The attitude indicator gyro indicates what around the lateral axis?

Pitch

How many degrees of bank is a standard rate turn?

What does the caging knob do?

To adjust the wings up or down to align with the horizon bar.

In small aircraft with pneumatic drive gyros what is the suction regulated too, to avoid gyro overspeed?

5 inHg

What does an electrical drive system consist of?

Three phase Squirrel cage induction motor

What is the actual gyro speed of an electrical gyro when taking into account the slip of 6%?

22,500 RPM

In an electric drive gyro where are the torque motors located in relation to another?

90 degrees to each other.

What is a torque motor?

Squirrel cage motor

What two windings does a torque motor rotor have?

Reference winding and control winding.

In electrical gyro's what erection rate is available when the gyro is switched on after a long power interruption?

20 degrees per minute

When an aircraft is holding why do they take on the racetrack pattern?

To allow the erection system enough time after each turn to correct the topple.

A laser gyro uses what to provide similar function to mechanical gyro's?

Sagnac Effect beams of light.

What does RLG (Ring laser gyro) installation form part of?

Inertial reference system.

How many RLG's are there and how are they installed?

3, at right angles to one another

What is meant by coherent when describing a laser?

Wavelengths are in phase in space and time.

Where is the source of a laser?

Cathode

What is one issue with an RGL?

Laser lock

What is laser lock?

When the two beams synchronise and give zero output.

When must a gyro not be moved?

When it is running at medium speed

How does a gyro get gimbal lock?

Removed while running and tilted more than 20 degrees.

What is the main problem with a DG?

No north seeking tendency

What does a vertical card DG, represent?

Dial gauge with a plane on it.

What is nutation?

Wobbling

How is nutation avoided in a DG?

Spin down brake system

How does the spin brake system work?

Holds the gimbal for 30 seconds after shut down.

How often must a directional gyro be set to agree with magnetic compass?

Checked every 15 mins

What is a slaved gyro system?

Takes input from a remotely located compass.

What is a flux valve?

Small segmented rings made of soft iron that readily accept line of magnetic flux.

After departure what three components compromise gyro drift?

Apparent wander Transport Wander Real wander

What causes transport wander?

Caused by meridian convergence as you fly east or west.

Where is the horizontal situation indicator?

Normally mounted below the attitude indicator.

What does the horizontal situation indicator combine?

Heading and VOR-ILS

What does VOR-ILS stand for?

Very High Frequency Omnidirectional Range Instrument Landing System

What does the nav warning flag mean?

No reliable signal is being received.

How would you know the compass isn't functioning properly?

HDG flag

What does a VERT warning flag mean?

Glide slop data is missing

What type of indicator does and turn and slip indicator have?

Needle

On a rate of turn indicator, what does the first mark represent?

180 degrees per minute

On a rate of turn indicator, what does the second mark represent?

360 degrees per minute

On a rate of turn indicator, what does the third mark represent?

540 degrees per minute

On a rate of turn indicator, what does the fourth mark represent?

720 degrees per minute

What type is a turn indicator?

Rate gyro with horizontal axis

Rate gyros have one gimbal which is limited in motion by a spring, how many degrees of freedom does it have?

1.5 degrees

How do you know it the aircraft is slipping or skidding?

Turn coordinator ball is off centre

What are the two typical errors of turn indicators?

Springs adjustment Rotor Speed

What happens if the turn indicator rotor speed is too high?

The indication is higher than it should be.