MD-11 Flight Crew Operations Manual
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Automatic Flight -
Description and Operation
Auto.10.23
The RETARD mode is a form of thrust control. The throttles are driven to the idle
stop when the AP goes into FLARE mode or when RA is less than 50 feet, flaps
are greater than 31.5 degrees and ATS is engaged. Exit from retard mode is by
setting throttles to reverse thrust or initiation of go-around mode.
ATS Speed Control
The ATS speed control is automatically limited by the following speeds:
• Vmin + 5 knots as determined by the FMS and normal flap/slat
configurations.
• Vmin + 5 knots as determined by the FMS and abnormal flap/slat
configuration.
• Vmin + 5 knots + Vgust when flaps exceed 31.5 degrees (landing flaps)
• Vmo/Mmo - 5 knots.
• Flap placard speed - 5 knots.
• Slat placard speed - 5 knots.
• Landing gear placard speed - 5 knots.
• FMS 1.2g buffet speed - 5 knots (standard) or FMS 1.3g buffet speed - 5
knots.
Vgust is a wind rate integration term calculated from CAS RATE (wind gust) and
can have a value between 0 and 5 knots depending on the gust amplitude. In gusty
wind conditions, the minimum ATS target speed will be in a range from Vmin +
5 knots to Vmin +10 knots, depending on gust amplitude. This Vgust term does
not affect the speed targets displayed on the PFD.
Pilot selection of the reference speeds is accomplished via the FCP. The FCP
provides for preselect of IAS and MACH.
A speed hold function allows the existing speed to be the target speed during
steady state flight. It will also allow a smooth capture target speed during aircraft
acceleration. Speed control targets are also provided by the FMS profile modes.
The ATS controls to speed targets during approach, altitude hold, vertical speed,
flight path angle, and profile modes of the AFS/FMS system.
Flight level change operation transfers the ATS to thrust control. Speed will then
be controlled by the pitch attitude. The speed and thrust control are annunciated
on the FMA.
The ATS provides for automatic speed reference transitions (IAS/Mach) during
climbs and descents as follows:
• If climbing and under IAS control, auto-transition occurs when the
existing MACH number equals the preselected Mach number (or 26,000
feet if Mach was not preselected).
• If descending and under control of Mach number, auto-transition occurs
when the existing IAS equals the preselected IAS (or 26,000 feet if IAS
was not preselected).
November 10 2008
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