CASTLEBERRY
Instruments & Avionics
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Document: 0052-1007-0002
Page 5 of 6
Revision A
1. The Parallax Adjustment Knob is an optional item. Some models may have a cover over this adjustment
where it has been preset by maintenance personnel. This adjustment is used to set the Parallax Indicator
(item 2) reference on the actual gyro horizon after settling as viewed by the pilot. Aircraft engines should
be on during this process to apply nominal operating voltage to gyro and to generate the required vibration
to overcome static friction to simulate a real operating environment. Normal operation would be to turn
gyro on and allow for gyro to spin up till flag (item 6) hides out of view, then perform a caging operation
(explained for item 8) and then allow gyro a few minutes to settle to level. The gyro is settled when both
pitch and roll indications remain constant. The Parallax may be set on ground when the aircraft is level as
it would be in a trimmed straight and level flight or set in air during straight and level trimmed flight with
wingtips and pitch reference on the earth’s horizon. At this time the Parallax Adjustment knob should be
set so that at the pilots viewing angle of the Parallax Indicator rests centered on the horizon line of the
Pitch Bar (item 3). Once the parallax is set it is generally not changed again unless the pilot’s seat has
moved or a different height pilot requires a different viewing angle.
2. This is the Parallax Indicator. Purpose and operation is described in paragraph 1 which is the adjustment
that sets the position of this item.
3. Item 3 is the Pitch Bar. The gyro pitch attitude angle is determined by reading the Pitch Bar position
against the Parallax Indicator (previously set in item 1).
Note:
The horizon line on the Pitch Bar may or may not be exactly aligned with the zero indices of the
Roll Dial (item 5) at true level. This can be due to the ± 1½ degree tolerance that is typical for attitude
gyros.
4. This is the Roll Indice. The roll attitude angle is read by the position of the Roll Dial (item 5) against this
indice.
5. Roll Dial. See Item 4.
6. The Gyro Flag is a monitor to determine integrity of gyro. It is controlled by internal circuitry that will
cause the Flag to come into view if input power or gyro RPM becomes too low. Since it is affected by
gyro RPM, the Flag does not go out of view immediately when power is applied. Typically it takes 1 to 3
minutes for the Flag to go out of view and up to 5 minutes if operating with low voltage.
7. This is the inclinometer. It is a required device when this gyro is installed as a replacement for the turn
indicator gyro per FAA advisory circular AC91-75.
