787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Instruments, Displays -
System Description
Copyright © The Boeing Company. See title page for details.
10.20.16 D615Z003-TBC
Attitude Heading Reference Units (AHRU)
The AHRUs are the primary source for attitude and heading information. (Refer
to Attitude and Heading Reference Unit (AHRU)
in Chapter 11, Section 20, for
additional information.)
Air Data Reference System (ADRS)
The ADRS provides primary, secondary, and standby air data. The major
components of the ADRS are:
• six air data modules
• six static ports
• three pitot probes
• two angle–of–attack vanes
• one total air temperature probe.
Air Data
Three static ports are located on the left side of the airplane and three static ports
are located on the right side of the airplane. Left and right static ports are paired
through pneumatic tubing to each of the left, center and right air data modules. The
air data modules convert static air pressure to a digital output for use by other
systems.
Two pitot probes (right and center) are mounted on the right forward section of the
airplane. One pitot probe (left) is mounted on the left forward section of the
airplane. An air data module is connected to each pitot probe. The air data modules
convert dynamic air pressure to a digital output for use by other systems.
Angle–of–Attack
There are two angle–of–attack vanes, one located on each side of the forward
fuselage. The vanes measure airplane angle–of–attack relative to the air mass.
Total Air Temperature
A total air temperature probe is mounted outside the airplane to sense air mass
temperature. The temperature sensed by the probe is used by the ADRS to
compute total air temperature. The ADRS also receives TAT measurements from
each of the EEC TAT sensors for a total of six inputs. These inputs are used to
derive a weighted average, trusted TAT.
When on the ground at less than 50 kts CAS, sensors in CAC inlets (two per inlet)
provide ADRS TAT. The ADRS selects the lower of the two CAC inlet
temperatures.
Static Air Temperature
Static air temperature, displayed on the CDU PROGRESS page, comes from the
ADRS, using total air temperature probe information.
February 15, 2010
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