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EspañolTURN INDICATOR
(Redirected from Slip indicator)
A 'Turn Indicator' is an aircraft flight instrument that shows the rate of turn. It is used by the pilot to maintain control when flying under Instrument flight rules.
Attitude and heading indicators function on the principle of
rigidity, but rate instruments such as the turn-and-slip indicator
operate on gyroscopic precession. Precession is the characteristic
of a gyroscope that causes an applied force to produce a
movement, not at the point of application, but at a point 90°
from the point of application in the direction of rotation.
Main articles: Turn and bank indicator
The first gyroscopic aircraft instrument was the turn indicator
in the needle and ball, or turn-and-bank indicator, which
has more recently been called a turn-and-slip indicator.
The inclinometer in the instrument is a black glass ball sealed
inside a curved glass tube that is partially filled with a liquid,
much like compass fluid. This ball measures the relative
strength of the force of gravity and the force of inertia caused
by a turn. When the aircraft is flying straight-and-level, there
is no inertia acting on the ball, and it remains in the center of
the tube between two wires. In a turn made with a bank angle
that is too steep, the force of gravity is greater than the inertia
and the ball rolls down to the inside of the turn. If the turn is
made with too shallow a bank angle, the inertia is greater than
gravity and the ball rolls upward to the outside of the turn.
The inclinometer does not indicate the amount of bank, neither
is it limited to an indication of slip; it only indicates the
relationship between the angle of bank and the rate of yaw.
The turn indicator is a small gyroscope spun either by air or by
an electric motor. The gyro is mounted in a single gimbal
with its spin axis parallel to the lateral axis of the aircraft
and the axis of the gimbal parallel with the longitudinal axis.
When the aircraft yaws, or rotates about its vertical axis, it
produces a force in the horizontal plane that, due to precession,
causes the gyro and its gimbal to rotate about the
gimbal axis. It is restrained in this rotation plane by a
calibration spring; it rolls over just enough to cause the
pointer to deflect until it aligns with one of the doghouse shaped
marks on the dial, when the aircraft is making a
standard-rate turn.
The dial of these instruments is marked “2 MIN TURN.”
Some turn-and-slip indicators used in faster aircraft like the Concorde are
marked “4 MIN TURN.” In gliders, the calibration spring is usually set for a one minute standard rate turn. A standard-rate
turn is being made whenever the needle aligns with a
doghouse.
Main articles: Turn coordinator
The major limitation of the older turn-and-slip indicator is
that it senses rotation only about the vertical axis of the
aircraft. It tells nothing of the rotation around the longitudinal
axis, which in normal flight occurs before the aircraft begins
to turn.
A turn coordinator operates on precession, the same as the
turn indicator, but its gimbal frame is angled upward about
30° from the longitudinal axis of the aircraft. This allows it
to sense both roll and yaw. Some turn coordinator gyros are
dual-powered and can be driven by either air or electricity.
Rather than using a needle as an indicator, the gimbal moves
a dial on which is the rear view of a symbolic aircraft. The
bezel of the instrument is marked to show wings-level flight
and bank angles for a standard-rate turn.
The inclinometer, similar to the one in a turn-and-slip
indicator, is called a coordination ball, which shows the
relationship between the bank angle and the rate of yaw. The
turn is coordinated when the ball is in the center, between the
marks. The aircraft is skidding when the ball rolls toward the
outside of the turn and is slipping when it moves toward the
inside of the turn.
A turn coordinator does not sense pitch. This is indicated on
some instruments by placing the words “NO PITCH
INFORMATION” on the dial.
★ Advisory Circular AC 61-23C, ''Pilot's Handbook of Aeronautical Knowledge'', U.S. Federal Aviation Administration, Revised 1997.
★ FAA-H-8083-15 ''Instrument Flying Handbook'', U.S. Federal Aviation Administration (IFH), (Update 25 Nov 05)
Illustration of the face of a turn-and-slip indicator
A 'Turn Indicator' is an aircraft flight instrument that shows the rate of turn. It is used by the pilot to maintain control when flying under Instrument flight rules.
Attitude and heading indicators function on the principle of
rigidity, but rate instruments such as the turn-and-slip indicator
operate on gyroscopic precession. Precession is the characteristic
of a gyroscope that causes an applied force to produce a
movement, not at the point of application, but at a point 90°
from the point of application in the direction of rotation.
| Contents |
| Turn-and-Slip Indicator |
| Turn Coordinator |
| Sources |
Turn-and-Slip Indicator
The rate gyro in a turn-and-slip indicator and turn coordinator.
Main articles: Turn and bank indicator
The first gyroscopic aircraft instrument was the turn indicator
in the needle and ball, or turn-and-bank indicator, which
has more recently been called a turn-and-slip indicator.
The inclinometer in the instrument is a black glass ball sealed
inside a curved glass tube that is partially filled with a liquid,
much like compass fluid. This ball measures the relative
strength of the force of gravity and the force of inertia caused
by a turn. When the aircraft is flying straight-and-level, there
is no inertia acting on the ball, and it remains in the center of
the tube between two wires. In a turn made with a bank angle
that is too steep, the force of gravity is greater than the inertia
and the ball rolls down to the inside of the turn. If the turn is
made with too shallow a bank angle, the inertia is greater than
gravity and the ball rolls upward to the outside of the turn.
The inclinometer does not indicate the amount of bank, neither
is it limited to an indication of slip; it only indicates the
relationship between the angle of bank and the rate of yaw.
The turn indicator is a small gyroscope spun either by air or by
an electric motor. The gyro is mounted in a single gimbal
with its spin axis parallel to the lateral axis of the aircraft
and the axis of the gimbal parallel with the longitudinal axis.
When the aircraft yaws, or rotates about its vertical axis, it
produces a force in the horizontal plane that, due to precession,
causes the gyro and its gimbal to rotate about the
gimbal axis. It is restrained in this rotation plane by a
calibration spring; it rolls over just enough to cause the
pointer to deflect until it aligns with one of the doghouse shaped
marks on the dial, when the aircraft is making a
standard-rate turn.
The dial of these instruments is marked “2 MIN TURN.”
Some turn-and-slip indicators used in faster aircraft like the Concorde are
marked “4 MIN TURN.” In gliders, the calibration spring is usually set for a one minute standard rate turn. A standard-rate
turn is being made whenever the needle aligns with a
doghouse.
Precession causes a force applied to a spinning wheel to be felt 90° from the point of application in the direction of rotation.
Turn Coordinator
Main articles: Turn coordinator
The major limitation of the older turn-and-slip indicator is
that it senses rotation only about the vertical axis of the
aircraft. It tells nothing of the rotation around the longitudinal
axis, which in normal flight occurs before the aircraft begins
to turn.
A turn coordinator operates on precession, the same as the
turn indicator, but its gimbal frame is angled upward about
30° from the longitudinal axis of the aircraft. This allows it
to sense both roll and yaw. Some turn coordinator gyros are
dual-powered and can be driven by either air or electricity.
Rather than using a needle as an indicator, the gimbal moves
a dial on which is the rear view of a symbolic aircraft. The
bezel of the instrument is marked to show wings-level flight
and bank angles for a standard-rate turn.
The inclinometer, similar to the one in a turn-and-slip
indicator, is called a coordination ball, which shows the
relationship between the bank angle and the rate of yaw. The
turn is coordinated when the ball is in the center, between the
marks. The aircraft is skidding when the ball rolls toward the
outside of the turn and is slipping when it moves toward the
inside of the turn.
A turn coordinator does not sense pitch. This is indicated on
some instruments by placing the words “NO PITCH
INFORMATION” on the dial.
The inclinometer of the turn coordinator indicates the coordination of aileron and rudder. The ball indicates whether the airplane is in coordinated flight or is in a slip or skid.
Sources
★ Advisory Circular AC 61-23C, ''Pilot's Handbook of Aeronautical Knowledge'', U.S. Federal Aviation Administration, Revised 1997.
★ FAA-H-8083-15 ''Instrument Flying Handbook'', U.S. Federal Aviation Administration (IFH), (Update 25 Nov 05)
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