THE ARTIFICIAL HORIZON - Dgca question bank for pilots

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#1. Inside an artificial horizon:

the inner gimbal ring is tied to the vertical by a control system

the rotor axis is kept level by a calibrated spring attached to the outer gimbal ring and the instrument case

there is only one gimbal ring

the inner gimbal ring is pivoted laterally inside the outer gimbal ring and the outer gimbal ring is pivoted longitudinally inside the case

#2. The rotor axis of an electrical horizon is tied to the earth’s vertical by:

two mercury level switches and two torque motors

the low centre of gravity of the rotor housing

the roll cut out

four pendulous vanes

THE ELECTRIC ARTIFICIAL HORIZON

The main advantage of the electric artificial horizon over the air-driven horizon is its greater rigidity due to its faster spin rate. This greater rigidity results in increased accuracy due to reduced errors.
The basic principle of the instrument is the same as the air-driven horizon.
The vertical gyro is still tied by Earth’s gravity, but by mercury/levelling switches and torque motors rather than the pendulous vanes of the air-driven horizon

#3. False right wing low attitude shown on an air driven artificial horizon during an acceleration is caused by:

high rotor speed

the lag of the base of the rotor housing

the logitudinal pendulous vanes

the roll cut-out

Roll Error

Due to inertia, the weighted base of the rotor housing tries to lag during acceleration.
The roll error is due to the inertia of the bottom-heavy rotor housing.
Deceleration will cause a nose down, left wing low error, the opposite of the acceleration error indication. (Opposite)

#4. An electrically driven artificial horizon has less errors during the take-off run because:

the roll cut-out speed is activated

it is less aperiodic than the air driven types

it is less pendulous, has a higher rotor speed and a linear acceleration cut out

the mercury level switches are more sensitive than the pendulous vanes fitted to air driven types

THE ELECTRIC ARTIFICIAL HORIZON

The main advantage of the electric artificial horizon over the air-driven horizon is its greater rigidity due to its faster spin rate. This greater rigidity results in increased accuracy due to reduced errors.
The basic principle of the instrument is the same as the air-driven horizon.

#5. During the take-off run an air driven artificial horizon will usually indicate:

nose up and incorrect left bank.

a false descending turn to the right.

a false climbing turn to the left.

increased nose up attitude and right wing low.

ACCELERATION ERROR

False indication of a right bank and overall effect is Climbing Right Turn.
(Nose up, right wing down displayed.)

#6. An artificial horizon utilises (i)………… to show (ii)…….. in (iii)……. and (iv)………….

(i) an earth gyro (ii) attitude (iii) pitch (iv) roll

i) an earth gyro (ii) position (iii) latitude (iv) longitude

i) a space gyro (ii) attitude (iii) degrees (iv) minutes

(i) an earth gyro (ii) latitude (iii) pitch (iv) roll

TRICK TO REMEMBER

AVE-2

A: Artificial Horizon.
V: Vertical Axis Gyro.
E: Earth Gyro.
2: 2 Degrees of Freedom.

ARTIFICIAL HORIZON (A.H.)

Provides an indication of A/C attitude in PITCH and ROLL. It is a primary replacement for the natural horizon in poor visibility.
It uses EARTH GYRO – has freedom of movement about 3 planes.
Attitude indicators may be Pneumatically or electrically driven.
In pneumatically driven gyro, RPM is about 15000.
When A/C flying straight & level, Horizon bar & aircraft symbol will appear in mid-position.
The artificial horizon uses an Earth gyro in which the spin axis is maintained in, or tied to, the vertical by Earth’s gravity

#7. When an adjustable aircraft datum is fitted to an artificial horizon in light aircraft:

it should be checked at regular intervals

it should be rendered inoperative

it should be set to 15°

it should be set to the central position and left there

On some artificial horizons it is possible to raise or lower the position of the miniature
aircraft in the instrument window, so that it can be adjusted to lie along the horizon bar in level
flight. The danger is that, should the adjusting knob be inadvertently turned in flight, the instrument
will subsequently give erroneous indications of pitch attitude, and this could be confusing to the pilot
in actual IMC conditions.

It is recommended that in light aircraft the datum be set before flight and
thereafter left well alone. Such movable datums be removed or otherwise rendered inoperative on aircraft having a maximum all-up weight in excess of 6,000
pounds

#8. The indication at Figure shows:

a climbing turn to the right.

30° port bank, nose below horizon.

30° starboard bank, nose up.

nose-up and left wing down

#9. False nose-up attitude displayed on air driven artificial horizon during the take-off run is caused by:

the linear acceleration cut out

the lag of the lateral pendulous vanes

incorrect rotor speed

the high pendulosity of the rotor

In the first image, the aircraft is stationary, and no thrust has been applied, so the pendulously mounted gyro remains stable. In the second image, as the aircraft’s thrust is applied, the acceleration causes the gyro to behave as shown, with its orientation affected by the forces of acceleration. However, if lateral pendulous vanes were installed, this behavior would be mitigated, preventing the gyro from being influenced in this manner by acceleration.

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