Yak 18T Flight Operations Manual
Page 73 of 82
Disclaimer: This manual is to be used as a reference only, it is based on translated Yak 18T Flight Operations
Manuals and has not been approved by the Yakovlev Design Bureau or any other authority.
indications that must be compared with those of the electric turn indicator and to the
position nose-over and canopy front portions relative to the natural horizon.
NOTE
It is advisable to use the caging button at pitch angles more than +4°, as after caging the
gyro erection can be switched off. Setting the circuit breaker on the switchboard to the off
position turns off the gyro-horizon.
6.
In case of gyro-horizon failure in flight, determine the spatial attitude of the aircraft by
the natural horizon and by the indicator and indications of the variometer.
Electric Turn Indicator
The electric turn indicator is designed to indicate the correct 45-degree banked turning of the
aircraft in flight about a vertical axis. It combines a turn indicator and a slip indicator in one
unit. The aircraft turn is shown by the pointer and slipping by a ball. The indication accuracy
error at normal conditions of the flight with 15, 30, 45 degree banks and angular velocities
1.1°C, 2.3°C and 4°C respectively is ±1.5°.
Radio Altimeter
General Information
The radio altimeter is intended to be used for measuring absolute flight altitude in the range
of 0-750m and warning that the aircraft has reached the assigned altitude, which value is
preset on the indicator. The instrument placed on the instrument panel is employed as the
altitude indicator. The instrument flange accommodates an altitude setting control with a
built-in yellow warning light and a button (CHECKING) with built-in red warning light. By
rotating the ALTITUDE SET control, warning setting of the desired altitude is provided, its
value is determined by a yellow triangular marker moving over the indicator scale. When the
aircraft has achieved the command altitude, the yellow light is illuminated and simultaneously
a 400-Hz audio signal is applied to the pilot's telephones during 3-9 seconds. When the
CHECKING push-button is pressed, a 15±1.5m test altitude is set on the proper radio
altimeter's indicator, if no button is used, the radio altimeter shows the flight absolute altitude
(or H=0 on the ground). The radio altimeter switching as well as protection of the supply
circuits are provided by the altimeter circuit breaker located on the switchboard.
Radio altimeter usage in flight
1.
Prior to take-off
Switch the radio altimeter power on using the circuit breaker. In this case a red light should
go on and the altitude indicator point will be displaced towards a digit 750m and go beyond
the scale black sector. After radio altimeter warm-up the red light should extinguish and the
indicator pointer should be set to 0±0.8 m scale division. Using the ALTITUDE SET control,
place the marker of the desired altitude warning unit against a 10m division of the scale.
Press and hold the CHECKING push button in this position. The indicator pointer in this case
will show the test altitude value of 15±1.5 m. Release a button CHECKING, when this is
done the indicator pointer will be displaced towards a zero value on the scale. When it passes
a 10m division, the warning light on the altitude indicator will light up and an audio signal will
be fed to the pilot's telephones. The radio altimeter is disconnected by the switch on the
switchboard.
2.
In flight
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