This article will attempt to explain some of the basic
MD-11 systems methodology in terms of how similar features work on the
Boeing 7x7 series aircraft you're likely more familiar with. If you're
familiar with Airbus systems logic, some of that general knowledge will
apply here, though be aware that many things on the MD-11 aren't exactly
like the Airbus either.
MCP
The glareshield MCP (mode control panel) used to command the
autopilot on a Boeing is called the FCP (flight control panel) on the
MD-11.
Flight Mode Annunciator
The MD-11's FMA (located at the top of the PFD display) works
slightly differently than you may be used to. Essentially you can see
one of three colors present in each of the three FMA fields representing
speed, roll and pitch. These colors have different meanings:
- Magenta = the mode is following FMS generated commands.
- White = the mode is following manual commands coming from the
FCP.
- Green = the mode is following commands associated with
performing an autoland.
Keeping this color coding system in mind will quickly allow you to
ascertain where the autopilot is getting its command information from at
any time.
Autothrottle
& autopilot relationship
The autothrottle and autopilot systems on the MD-11 are NOT
independent of each other in the way that they are on Boeing aircraft.
Before takeoff, pressing the AUTOFLIGHT button on the FCP arms both the
autothrottle and the autopilot takeoff modes. Advancing the throttles
manually past around 60% N1 will cause the autothrottle system to
actually engage and begin controlling thrust. There is an audible click
sound from the panel when this happens. After takeoff, press
Autoflight again to do the equivalent of pressing one of the autopilot
CMD buttons on a Boeing. This will actually give control of the pitch
and roll modes over to the AP. From this point on, the two systems are
completely unified and essentially operate as a combined system until
disengagement at landing.
Disconnecting
the autopilot & autothrottle
The MD-11 does NOT have "hard" switches on the FCP for disconnecting
the AP and AT the way Boeing airplanes do. The only way to do
disconnect them are via the soft disconnect switches located on the yoke
and throttle in the real aircraft. There are key commands assignable
in the PMDG menu for simulating these buttons. Upon pressing the AP
disconnect, you will hear a disconnect warning, simply press the AP
disconnect again to cancel this warning.
To reconnect the system, simply press AUTOFLIGHT on the FCP.
This will reconnect BOTH the AP and AT.
The two AFS OVRD OFF switches on the FCP below the AUTOFLIGHT
button are NOT regular autopilot disconnect switches like you may be
used to on a Boeing! These switches completely disable the MD-11's
automatics and you will lose other AFS functions that are normally
available even with the AP disengaged such as ATS speed protection.
Flaps
The MD-11 is equipped with a unique variable flap lever position
called Dial-A-Flap. It allows for any takeoff flap setting between 10
and 25 degrees to be set on the pedestal. 15 degrees is standard though
it may be more optimal to use a different value depending on the
situation. DAF is only used during takeoff, for approach it must be set
to 15 degrees.
RTE, LEGS, & DEP/ARR
The MD-11's MCDU does not have dedicated pages for these functions
the way a Boeing's CDU does. They are all handled through a single page
associated with each waypoint called the Lateral Revision (LAT REV)
page. Pressing the MCDU LSK to the left of a waypoint on the F-PLAN page
brings you to the LAT REV page for that waypoint. This page allows you
to do a number of things including inserting waypoints and airways,
SIDs, STARs, and approaches.
It is very important to note that LAT REV should always be called
up FROM the last waypoint prior to what you want. So if you want to
add a STAR for instance, you need to bring up the LAT REV page for the
last enroute waypoint before you want the STAR to start and add it from
there.
The rough 1:1 comparisons between a Boeing FMC's pages are as
follows:
- RTE - Origin and destination airports are entered on the
F-PLAN INIT page. The familar VIA and TO columns for airway entries are
located by pressing the AIRWAYS page, accessed through a waypoint's LAT
REV page.
- LEGS - The F-PLAN page is roughly equivalent, though
many modifications to the flight plan happen through a waypoint's LAT
REV page and not directly on the F-PLAN page and scratchpad the way
you'd do with a Boeing. The flight plan between your destination and
your alternate appears at the bottom of the waypoint list, after the
main origin to destination plan. The Boeing convention of making
modifications to the route by line selecting waypoints from further
downrange up into a new position does not apply here, you must use the
LAT REV page's NEXT WPT prompt.
- DEP/ARR - You insert SIDs, STARs, and approaches by
using the SID and STAR pages, accessed through the LAT REV page. You
should add a SID from origin airport's LAT REV page and a STAR from the
last enroute waypoint's LAT REV page.
Direct To
Going direct to a waypoint in the MD-11 is a dedicated function on
the MDCU, accessed by pressing the DIR INTC key. You can NOT go direct
by line selecting a waypoint to the top of the F-PLAN page the way you
would do on a Boeing CDU. Simply press DIR INTC, then line select the
waypoint into the box at the top or type it into the scratchpad. Confirm
it and off you go.
HDG HOLD & HDG SEL
The MD-11's version of these modes are accessed by either pushing the
heading knob to hold current heading, or pulling the knob to fly the
selected heading in the box.
ALT HOLD & LVL
CHG/FLCH
The MD-11 has modes roughly equivalent to both Boeing modes that can
be engaged by pushing the altitude knob to hold the current altitude or
pulling it to engage a pitch-for-speed mode similar to Boeing's LVL CHG
or FLCH modes. It will climb or descend and capture the altitude in the
window.
LNAV
This is simply called NAV on the MD-11's FCP and the button is
located below the heading knob.
VNAV
The MD-11's version of VNAV is called PROF, short for "profile" and
can be activated with the PROF button below the altitude knob.
Speed modes
Pushing the speed knob will hold the current airspeed, pulling it
will fly the selected speed in the window, and pressing the FMS button
will blank the window and allow the FMS to command speed.
FMS speed targets
The MD-11 is unique in a couple of respects with regard to FMS speed
targets and restrictions. All speed targets are treated as AT OR BELOW,
which means that you could end up crossing at a lower speed than what
you'd entered in for a particular waypoint if the FMS deems it
necessary. The FMS is smart and if you tell it to descend steeply and
decelerate at the same time, the deceleration will get moved backwards
along the route to account for the decent that's required later on.
Don't be alarmed if you see this propagation of lower speeds up into
waypoints you didn't set restrictions for, it's just the airplane
helping you manage your energy.
Speed control during
approach
Boeing pilots will be used to exercising manual control over the
aircraft's speed during approach by using the MCP speed window. This is
NOT how the MD-11 is designed. It is completely normal for the MD-11
to land with the speed window closed and under full FMS control.
The FMS calculates approach speed on the basis of a few rules
during the approach sequence, each distance listed is the point during
the approach where these speed reductions must occur by, but they can
occur earlier if calculations demand it.
- 15 to 11 miles - Slats +20.
- 7 miles - Dial-a-flap +20
- 6 miles - Flaps 28 +5
- 5 miles - landing flaps +5
The aircraft will automatically decelerate to these speeds provided
you have the aircraft configured correctly as far as flap settings. You
will see a hollow magenta circle on the speed tape indicating that it's
time to deploy the next flap setting.
Autoland
Performing an autoland in the MD-11 is as simple as pressing the
APPR/LAND button located on the FCP above the AUTOFLIGHT button.
Provided you are tuned to an ILS frequency that contains both a
localizer and glideslope, (which is done automatically by the FMS) the
plane will execute an autoland unless you take over manually.
The type of autoland is determined when you descend below 1,500
ft AGL as follows:
- If all your systems are opering normally you will see a green
DUAL LAND annunciation on the PFD FMA indicating a full CAT III
autoland.
- If you have failures that are not critical for the autoland
(for example, one of the two autopilots inoperative or one HYD system
failed) a white SINGLE LAND will be annunciated and a CAT II autoland
will apply.
- If you have critical system failures, or excessive deviation
from LOC or GS a white APPR ONLY will be annunciated and the autoland
function will not be available. The aircrtaft will continue to track LOC
and GS, but autopilot will disconnect at 100 ft AGL.
IMPORTANT
In an autoland the AP remains engaged after touch
down to keep the aircraft aligned to the runway. At the end of the
rollout you should manually disengage the autopilot, otherwise you will
not be able to taxi, since the AP will still try to keep you on runway
track.