YC411, YC413

Copyright . The Boeing Company. See title page for details.
9.20.24  June 1, 2005

Flight Controls -System Description 737 Flight Crew Operations Manual
Asymmetry and Skew Detection, Protection and Indication
The FSEU monitors the TE flaps for asymmetry and skew conditions. It also monitors the LE devices for improper position and skew conditions on slats 2 through 7. If a flap on one wing does not align with the symmetrical flap on the other wing, there is a flap asymmetry condition. A skew condition occurs when a TE flap or LE slat panel does not operate at the same rate causing the panel to twist during extension or retraction.
Trailing Edge Flap Asymmetry and Skew
When the FSEU detects a trailing edge asymmetry or skew condition the FSEU:
.
closes the TE flap bypass valve

.
displays a needle split on the flap position indicator.

Leading Edge Device Improper Position or Skew
When the FSEU detects a LE device in an improper position or a LE slat skew condition, the LE FLAPS TRANSIT light remains illuminated and one of the following indications is displayed on the LE DEVICES annunciator panel:
.
amber TRANSIT light illuminated

.
incorrect green EXT or FULL EXT light illuminated

.
no light illuminated.

There is no skew detection of the outboard slats, 1 and 8, or for the LE flaps. Slat skew detection is inhibited during autoslat operations.
Uncommanded Motion Detection, Protection and Indication
The FSEU provides protection from uncommanded motion by the LE devices or TE flaps.
Leading Edge Uncommanded Motion
Uncommanded motion is detected when no TE flap position or autoslat command is present and:
.
two LE flaps move on one wing, or

.
two or more slats move on one wing.

The FSEU shuts down the LE control and illuminates the amber LE FLAPS TRANSIT light. In addition, to prevent uncommanded motion from occurring on the LE devices
during cruise, the FSEU maintains pressure on the retract lines and depressurizes the extend and full extend lines.
Copyright . The Boeing Company. See title page for details.
Flight Controls -System Description 737 Flight Crew Operations Manual

Trailing Edge Uncommanded Motion
Uncommanded motion is detected when no FLAP lever or flap load relief command is present and the TE flaps:
.
move away from the commanded position

.
continue to move after reaching a commanded position, or

.
move in a direction opposite to that commanded. The FSEU shuts down the TE drive unit by closing the TE flap bypass valve. The TE flap shutdown cannot be reset by the flight crew and they must use the alternate

flap system to control TE flaps. The shutdown is indicated by the flap position indicator disagreeing with the FLAP lever position. There is no flap needle split.
Copyright . The Boeing Company. See title page for details.
9.20.26  June 1, 2005

737 Flight Crew Operations Manual

PFD/ND – Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.1
PFD/ND Display System – Overview . . . . . . . . . . . . . . . . . . . .  10.11.1 Captain Outboard Display . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.2 Captain Inboard Display . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.4 First Officer Inboard Display  . . . . . . . . . . . . . . . . . . . . . . . .  10.11.6
 First Officer Outboard Display . . . . . . . . . . . . . . . . . . . . . .  10.11.8 Primary Flight Display (PFD)– PFD Airspeed Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.10
PFD Airspeed Indications – General . . . . . . . . . . . . . . . . .  10.11.10 PFD Airspeed Indications – Takeoff and Approach . . . . . .  10.11.13 PFD – Attitude Indications  . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.17
Attitude Indications – General  . . . . . . . . . . . . . . . . . . . . . .  10.11.17 PFD Navigation Performance Scales (NPS) Indications  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.20 PFD Instrument Landing System Indications . . . . . . . . . . .  10.11.22 Expanded Localizer Indications . . . . . . . . . . . . . . . . . . . . .  10.11.25 PFD Radio Altitude Indications . . . . . . . . . . . . . . . . . . . . .  10.11.25 Traffic Alert and Collision Avoidance Indications . . . . . . .  10.11.27 GPWS Annunciations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.28 PFD – Altitude Indications  . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.29 Altitude Indications– General . . . . . . . . . . . . . . . . . . . . . . .  10.11.29 PFD Barometric Indications . . . . . . . . . . . . . . . . . . . . . . . .  10.11.30 Landing Altitude/Minimums Indications . . . . . . . . . . . . . .  10.11.32 PFD – Vertical Speed Indications  . . . . . . . . . . . . . . . . . . . . . .  10.11.35 Vertical Speed Indications – General  . . . . . . . . . . . . . . . . .  10.11.35 PFD - Heading and Track Indications  . . . . . . . . . . . . . . . . . . .  10.11.37 Heading and Track Indications– General . . . . . . . . . . . . . .  10.11.37 PFD Failure Flags  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10.11.38 Additional Annunciations and Alerts. . . . . . . . . . . . . . . . . . . .  10.11.42 Displays Control Panel Annunciation  . . . . . . . . . . . . . . . .  10.11.42
　
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