UND 220 Jo Block 2- Gyroscopic System

Gyroscopic Instruments

Heading Indicator, Attitude Indicator, Turn Coordinator

Two properties of gyroscopes

Rigidity in Space and Precession

Describe rigidity in space

Has stability in its axis, in avit instruments 1 axis is fixed

Describe precession

delayed peak force (90 degrees), in avit instruments no axes fixed

2 design characteristics of an instrument gyro

weight for its size/high density, and rotation at high speed with low friction bearings

2 general types of mountings based on 3 planes

Freely/universally mounted or semi-rigidly mounted

Which property does freely/universally mountain type follow

Precession-all three planes are free to rotate in ANY Direction in relation to the base

Which property does semi-rigidly mounted type follow

Rigidity in Space- One of the planes is held fixed in relation to the base

Gimbal

Stabilizer

Describe gyroscopic rigidity in space

the gyroscope is mounted on a set of gimbal rings, gyro is able to rotate freely in any direction while remaining in the plane in which it was originally spinning (lateral, longitudinal, vertical)

Describe gyroscopic precession

Turning or tilting of gyro in response to a deflective force.

Does the reaction to a tilting or turning force on a gyro occur at the point at which the force was applied?

No, it occurs 90 degrees later in the direction of rotation

Skidding

Turning with too much rudder

Slipping

Turning with to much aileron

How does rigidity in space apply to flight instruments?

Gyro remains rigid in the case and the aircraft rotates about it

How does precession apply to flight instruments?

The gyro rolls proportionate to the rate at which the aircraft rotates about one or more of its axes

Rigidity in Space Instruments

Heading Indicator and Attitude Indicator

Precession/”rate” instruments

Turn coordinator (+turn and slip indicator)

Is there a magnet in the heading indicator?

No

How does the attitude indicator work?

A horizontal disk is attached to the gimbal, the mounted gyro remains fixed (rigid) and spun at a high speed. The vertical spin axis senses rotation about the horizontal axis. The aircraft pitches and rolls about the gyro.

Can older attitude indicators pitch or roll as much as they want?

No, they were generally limited to roughly 60 degrees of pitch and 100 degrees of roll

Can a gyro function properly if it is not vertically upright

No

How long does it take for the gyro to become vertically upright after engine start

2-3 mins

What happens to attitude indicator when you rapidly accelerate

Shows a slight nose up

What happens to attitude indicator when you rapidly decelerate

Shows a slight nose down

What happens to attitude indicator after a 180 degree turn

small bank or pitch error

How does the heading indicator work

Gyro is mounted on a double gimbal, spin axis is horizontal, and it senses rotation about the vertical axis

Is the heading indicator traditionally north-seeking?

No, must be manually adjusted by referring to a magnetic compass

How many degrees does Earth rotate per hour?

15

How many degrees does heading indicator drift per hour?

15

Lateral Axis

Pitch

Longitudinal Axis

Roll

Vertical Axis

Yaw

Standard Rate Turn

3 degrees/second

Inclinometer

Ball that indicates relationship between bank angle/rate of yaw, not amount of bank

Inclinometer ball rolls to the inside of the turn

Slipping (too steep bank angle), gravity is GREATER than inertia

Inclinometer ball rolls to the outside of the turn

Skidding (too much rudder), gravity is LESS THAN inertia

How does gyroscopic precession relate to the propellor?

Changes in pitch of the aircraft apply force to the top/bottom of the propellor, the effects of that force are not caused until 90 degrees later

What will happen to the aircraft when you pitch up?

Yaw left

What will happen to the aircraft when you pitch down?

Yaw right

3 types of power sources

Pneumatic, vacuum pump, electrical

Venturi Tube System

driven by jet of air, mounted outside the aircraft. uses bernoulli’s principle to speed up the air in the narrower part of the vacuum

wet-type vacuum

steel vane air pumps are used to evacuate the instrument cases, vanes are lubricated with oil

dry-type vacuum

similar to wet-type except the pumps do not need oil mixed with the air because the vanes are made of a special formulation of carbon. used in high altitudes where the air is less dense

Why do most aircraft have at least 2 power sources?

Redundancy

Attitude and Heading Reference System

replaces traditional gyroscopic flight instruments, magnetometer, capability for satellite signal receptionAd

Air Data Attitude and Heading Reference System

use of GPS, rate sensors, air data, magnetic variation

What does AHRS display?

slip/skid indicator with roll pointer, attitude indicator, magnetic heading indicator/HSI, rate of turn indicator

Are all gyroscopic parameters affected if AHRS fails?

yes. avoid imc.

Affected instruments for ADC failure

indicated airspeed, true airspeed, altimeter, vsi, outside air temp