MD-11 Flight Crew Operations Manual
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Warning and Alerting -
Description and Operation
Warn.10.13
The audio signals generated in the CAWS controller feed into the Digitally
Controlled Audio System (DCAS) audio management units 1 and 2. These units
then send the signal to the appropriate speakers and headphones.
The aural warnings are tones such as horns, chimes and bells accompanied with
voice warnings from selected warnings and alerts. The voice warning and its
associated tone warning is cycled, a one-second tone followed by a one-second
voice warning for the duration of the warning period.
The CAWS can automatically sequence each aural warning when two or more
warnings occur at the same time. The latest warning will interrupt the warning in
progress. Sequential operation will continue with the latest warning included in
the sequence.
Some warnings are inhibited during certain phases of flight.
Landing Gear Warning
The CAWS will provide an aural warning tone for an unsafe landing
configuration. An unsafe configuration is defined by either of the following
conditions:
1. Any gears not down and locked and flaps in landing configuration.
2. Any gears not down and locked, any throttle(s) retarded to idle, airspeed less
than 210 knots, flaps not in landing configuration (less than 31.5 degrees)
and RA at 1,200 feet or below.
For condition 1 above, if the wing flaps exceed 31.5 degrees, the only way that the
aural warning can be silenced is by extension of the landing gear to the down and
locked position.
The aural warning for condition 2 can be silenced manually with the GEAR
HORN OFF button on the forward pedestal if the flap angle does not exceed 31
degrees. The landing gear warning function will activate whenever the throttles
are retarded to idle.
There is a delay of 16 seconds in the gear horn actuation when the gear is in transit
(being raised) and flaps are in landing range. This allows time for the flaps to
retract without sounding the horn during a missed approach.
Engine Fire Warning
The CAWS will provide an aural warning tone when a fire is detected by the
engine fire detection system. Refer to the Fire Protection chapter for a description
of the engine fire detection system.
October 02, 2006
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