AFDS Autoland Capabilities
Refer to the applicable AFM for a description of demonstrated autoland capabilities.
Initiation of an approach based on using autoland with any hydraulic system inoperative is not appropriate. However, for fail operational airplanes, if a hydraulic system becomes inoperative below alert height, the automatic approach may be continued through landing and rollout unless a NO AUTOLAND is displayed. The pilot should not intervene unless it is clearly evident that pilot action is required.
Note: For autoland use flaps 25 or 30.
Note: Autoland should not be attempted unless the final approach course path is
aligned with the runway centerline. If the localizer beam is offset from the
centerline the AFDS ROLLOUT mode may cause the airplane to depart
the runway.
ILS Performance
Most ILS installations are subject to signal interference by either surface vehicles or aircraft. To prevent this interference, ILS critical areas are established near each localizer and glide slope antenna. In the United States, these areas are restricted from all vehicle or aircraft operation any time the weather is reported less than 800 foot ceiling and/or visibility is less than 2 miles.
When the weather is less than 200 foot ceiling or the RVR is 2,000 or less, vehicle or aircraft operations in or over these critical areas are not authorized when an arriving aircraft is inside the Middle Marker (MM).
During Category III operations, the entire length of the preceding aircraft must be 250 feet clear of the runway centerline before an aircraft on an ILS approach reaches the Middle Marker or 200 feet AGL.
Flight inspections of ILS facilities do not necessarily include ILS beam performance inside the runway threshold or along the runway unless the ILS is used for Category II or III approaches. For this reason, the ILS beam quality may vary and autolands performed from a Category I approach at these facilities should be closely monitored.
Flight crews must remember that the ILS critical areas are usually not protected when the weather is above 800 foot ceiling and/or 2 mile visibility. As a result, ILS beam bends may occur because of vehicle or aircraft interference. Sudden and unexpected flight control movements may occur at a very low altitude or during the landing and rollout when the autopilot attempts to follow the beam bends. At ILS facilities where critical areas are not protected, flight crews should be alert for this possibility and guard the flight controls (control wheel, rudder pedals and thrust levers) throughout automatic approaches and landings. Be prepared to disengage the autopilot and manually land or go-around.
The AFDS includes a monitor to detect significant ILS signal interference. If
localizer or glide slope signal interference is detected by the monitor, the autopilot disregards erroneous ILS signals and remains engaged in an attitude stabilizing mode based on inertial data. Most ILS signal interferences last only a short period of time, in which case there is no annunciation to the flight crew other than erratic movement of the ILS raw data during the time the interference is present. No immediate crew action is required unless erratic or inappropriate autopilot activity is observed.
If the condition persists, it is annunciated on the attitude display. If the autopilot is engaged, annunciations alert the flight crew that the autopilot is operating in a degraded mode and the airplane may no longer be tracking the localizer or glide slope. When the condition is no longer detected, the annunciations clear and the autopilot resumes using the ILS for guidance.
Copyright . The Boeing Company. See title page for details.
October 31, 2003 FCT 757 (TM) 5.15
Autolands on Contaminated Runways
AFDS ROLLOUT mode performance cannot be assured when used on contaminated runways. The ROLLOUT mode relies on a combination of aerodynamic rudder control, nose wheel steering and main gear tracking to maintain the runway centerline using localizer signals for guidance. On a contaminated runway, nose wheel steering and main gear tracking effectiveness, and therefore airplane directional control capability, is reduced. To determine the maximum crosswind, use the most restrictive of the autoland crosswind limitation, or during low visibility approaches, the maximum crosswind authorized by the controlling regulatory agency. Consideration should also be given to the Landing Crosswind Guidelines published in chapter 6 of this manual or operator guidelines.
If an autoland is accomplished on a contaminated runway, the pilot must be prepared to disengage the autopilot and take over manually should ROLLOUT directional control become inadequate.
AFDS System Configuration
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