Automatic Flight - Operations

Amendment: Autolands Allowed with Engine Inoperative Prior to Landing Flaps.

Takeoff and Climb Profile

On some installations CLB thrust is automatically set when another pitch or A/T mode is selected.

Takeoff is a flight director only function and can only be engaged on the ground. The autopilot is not used during the takeoff roll but may be engaged after lift-off.

During pre-flight:

• With the autopilot disengaged and both F/D switches OFF, activation of TO roll and pitch mode occurs when the first F/D switch is positioned ON
• ADI displays FD as AFDS status and TO as the pitch and roll flight mode annunciations
• Command steering bars come into view.

On takeoff, prior to 80 knots IAS:

• Pitch command is set to a fixed attitude of approximately eight degrees up.
• Roll commands wings level.
• Autothrottle is engaged in N1 by pushing N1 switch.
• Thrust levers advance until the first engine reaches the selected takeoff N1.
• FMAs display N1 for Autothrottle and TO for both pitch and roll modes.

During takeoff, prior to lift-off:

• At 80 knots, Autothrottle annunciation changes to THR HOLD.

At lift-off:

• Pitch command greater of V2 + 15 kt or liftoff speed + 15 kt.
  When the radio altimeter is more than 5.0 feet for 2.0 seconds, an INAIR signal adjusts the 8.0° command to the attitude command necessary to keep the takeoff speed.
• If engine failure occurs on the ground, the pitch command target speed at lift-off is V2 or airspeed at liftoff, whichever is the greater, up to a maximum is V2 + 15 kt.
• Roll commands bank to maintain ground track.

After lift-off:

• FD TO modes are terminated by engaging an A/P in CMD, or by selecting any other pitch or roll mode.

On some installations:

• A/T remains in THR HOLD mode at takeoff thrust until a pitch mode, A/T mode, or Thrust Reference Mode Switch is pushed. The A/T then sets the selected reference thrust.
• Fast/Slow pointer appears on ADIs following selection of a thrust mode other than TO and a FD mode other than TO.

Note: Autopilot elevator authority during a single autopilot operation is limited to reduce the effects of an autopilot malfunction. During altitude capture, there may be insufficient elevator authority and stabiliser trim rate to counteract pitch down, caused by the combination of thrust reduction, flap retraction and aft cg.

Note: An altitude capture from a climb that includes a significant airspeed increase or thrust reduction may result in the autopilot descending away from the selected altitude in an attempt to increase the airspeed.

Cruise

The autopilot and/or flight director can be used after takeoff to fly a lateral navigation track (LNAV) and a vertical navigation track (VNAV) provided by the FMC. Using LNAV and VNAV ensures the most economical operation.

Approach and Landing

The AFDS provides guidance for multiple autopilot precision approaches to ILS CAT I, II, IIIA and IIIB weather minimums, or non-precision approaches: R NAV (via L NAV and V NAV mode) or LOC. Pushing the APP switch arms localiser in the roll mode and glideslope in the pitch mode. With an autopilot engaged, selection of APP automatically arms the other two autopilots for a multiple autopilot approach.

Either localiser or glideslope can be captured first.

Pushing the LOC switch arms the AFDS for localiser tracking. Descent on the localiser can be accomplished using VNAV, FLCH or V/S pitch modes. The localiser mode cannot capture if the intercept angle exceeds 120 degrees. All other non-precision approaches can be flown using LNAV and VNAV modes, or HDG SEL or V/S modes.

Pushing the B/CRS switch in conjunction with the LOC switch will enable localiser back course tracking.

Runway Alignment and Asymmetric Thrust Compensation

AFDS controls the rudder during multiple autopilot ILS approaches to compensate for engine-out asymmetric thrust conditions during an ILS approach.

The runway align sub-mode is operative during multiple autopilot ILS approach. It reduces the crab angle established during crosswind conditions prior to automatic landing. The submode operates as follows:

• Actuated at 500 feet Radio Altitude with [AUTO]LAND 3 or [AUTO]LAND 2 annunciated.
• Activation not displayed.
• Autopilot systems initiate a slip with a maximum bank angle of two degrees when the crab angle exceeds five degrees.
• Wing levelling from the slip is initiated when the ROLLOUT mode is engaged.

If the autopilots are disengaged, manually or automatically, in an asymmetric thrust condition with rudder control active, the rudder moves to the trimmed position. The pilot may need to exert rudder pedal force to maintain a smooth transition to manual flying.

Autolands Allowed with Engine Inoperative Prior to Landing Flaps

Flare

The flare manoeuvre brings the airplane to a smooth automatic landing touchdown. The flare sub-mode is a multiple autopilot mode, and is not intended for single autopilot or flight director only operation.

• Flare arms when (AUTO)LAND 3 or (AUTO)LAND 2 annunciates.
• At approximately 50 feet Radio Altitude, the autopilots start the flare manoeuvre.
• FLARE replaces the G/S pitch flight mode annunciation on the EADIs.

During flare:

• At 15 feet Radio Altitude the Autothrottle retards thrust levers to idle.
• IDLE replaces the SPD Autothrottle flight mode annunciation.
• If slip exists due to runway align sub-mode, wings levelled when ROLLOUT mode engaged.
• Autopilots start lowering nose smoothly to the runway at 5 ft RA plus 2 seconds with pitch attitude less than 2 degrees.
• At touchdown, the FLARE annunciation no longer displays, and the nose lowers to the runway.

Rollout

Rollout is a multiple-A/P approach sub-mode and provides runway centreline rollout guidance.

• ROLLOUT arms when [AUTO]LAND 3 or [AUTO]LAND 2 annunciates.
• At approximately 5 ft Radio Altitude, rollout activates. ROLLOUT replaces the LOC roll flight mode annunciation.
• The autopilot controls the rudder and nose wheel steering to keep the airplane on the localiser centreline.
• Roll command bar provides directional steering.
• Rollout guidance continues until a full stop or until the autopilots are disengaged.

During rollout, Autothrottle IDLE mode remains active until the Autothrottle disconnects with thrust levers in reverse (A/T DISC light remains extinguished) or Autothrottle manually disconnected.

Go-Around

Pushing either GA switch activates a go-around using multiple autopilot, single autopilot or flight director only.

When the F/D switches are not on, pushing either GA switch displays the flight director bars.

Go-around arms and the reference thrust limit changes to GA when:

• The Flaps are out of UP
• Glideslope is captured.

Arming is not annunciated. GA remains armed until two seconds after five feet Radio Altitude. Pushing either GA switch during this period of the approach engages the GA mode. The mode remains active even if the airplane touches down while executing the go-around.

• If the airplane is floating within five feet Radio Altitude for more than two seconds when the GA switch is pushed, the autopilot pitch mode will remain in FLARE and the Autothrottle go-around mode will engage - the aircraft will need to be rotated manually.

• If the airplane is on the ground but has been below five feet Radio Altitude for less than two seconds when the GA switch is pushed, the autopilot go-around pitch mode will engage but the Autothrottle mode will remain IDLE - the thrust levers will need to be advanced manually.

The GA switches are interlocked with the thrust reversers to prevent go-around mode engagement during Reverse Thrust operation.

Pushing either GA switch:

• Autothrottle, Roll and pitch activate in GA on EADI.
• Autothrottle increases thrust (to a maximum of GA thrust) to establish a climb rate of at least 2000 fpm.
• Roll commands bank to maintain ground track.
• AFDS increases pitch to hold existing speed or the selected MCP speed, whichever is higher, as thrust increases.
• If flap setting is 20 or less, a thrust mode other than go-around can be selected using the TMSP.

Note: Autopilot elevator authority during a single autopilot approach is limited to reduce the effects of an autopilot malfunction. If a go-around is initiated during a single autopilot approach, there may be insufficient elevator authority and stabiliser trim rate to counteract pitch up, caused by a rapid application of full go-around thrust. There is sufficient elevator authority to counteract pitch up when the go-around is flown using multiple autopilots, or manually (no autopilot), or when the Autothrottle go-around mode is used to set a 2000 fpm climb rate.

GA level-off:

• At the selected altitude, the AFDS pitch flight mode annunciation changes to ALT CAP, then to ALT HOLD, and Autothrottle mode changes to SPD. Thrust decreases to maintain selected speed.
• GA remains the active roll mode until another mode is selected.
• Landing Gear and Flaps must be operated manually.

GA Mode Termination:

Below 400 feet Radio Altitude:

• If flap setting is 25 or 30, Autothrottle remains in GA mode unless disengaged.
• Disengage autopilot and turn off both Flight Directors to disengage AFDS GA mode.

Above 400 feet Radio Altitude:

• Select a different roll or pitch mode using the MCP; when the new pitch or roll mode engages all autopilots, except first in CMD disengage.
• Autothrottle SPD mode can be selected.

Note: If the autopilot systems are compensating for an asymmetric thrust condition when they revert to a single autopilot in CMD configuration, the rudder will return to the trimmed position unless the pilot exerts the rudder pedal force required to maintain the rudder position.

Note: On detection of a failure in the first in CMD A/P, the fail sequence logic selects a different channel to be first in CMD. In the case of the R A/P being the first in CMD and failing, the Centre A/P will remain engaged at the first pitch or roll mode change following GA.

Windshear Recovery

As installed
The AFDS provides windshear recovery guidance by means of the normal go-around pitch and roll modes. With go-around armed, pushing a GA switch commands a pitch-up of 15 degrees or slightly below the Pitch limit Indicator, whichever is lower.

If the autopilot is not engaged at the time go-around is initiated, the pilot must fly the windshear recovery following flight director commands. If the Autothrottle is not armed or engaged, the thrust levers must be advanced manually.

Limit Modes