500 
Jul 15/70  27-51-0 
Page 105 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Flaps will not extend hydraulically or electrically in Flaps 25-40 range inflight (Cont.) Excessive force required to position flap control lever  14. Outboard foreflap track rollers 15. Transmission torque brake setting too low Excessive cable tension Rubbing cables, misaligned or defective pulleys Binding flap control valve Binding flap control quadrant  Dry ballscrew assemblies'  Inspect rollers for free rotation. Inspect tracks for evidence of skidding Disconnect transmissions and check torque brake settings in the following order: #2 and #7 (630 in-lbs. min) #3 and #6 (324 in-lbs. min) #4 and #5 (330 in-lbs. min) #1 and #8 (582 in-lbs. min) See Flap Transmission -(Ref. 21-51-281, I/C) Check cable tension per 27-51-0, Fig. 501 Check that pulleys align with cables within 2 degrees. Check cable runs for free running pulleys, and foreign objects Remove lower pan from flap control unit and disconnect trailing edge cam link from bell crank. Actuate bellcrank to check freedom of valve slide Disconnect WFA and WFB cables from flap control quadrant. Remove lower pan from flap control unit and disconnect trailing edge cam link from bellcrank. Manually rotate quadrant to check freedom of quadrant bearings Check ballscrews for proper lubrication  Replace roller if binding Replace transmission if torque brake settings not correct Adjust cable tension Repair or replace defective parts. Remove foreign objects Replace trailing edge flap control valve. (Ref. 27-51-211, R/I) Replace defective bearings. (Ref. 27-51-191, R/I)Lubricate ballscrew (Ref. 12-22-51) 

500 
27-51-0  Oct 20/90 
Page 106 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
During takeoff/approach, additional rudder or aileron trim is required to maintain level flight  Outboard T.E. flap carriage mid-flap spindle broken  Remove access panels from upper surface of midflap to gain access to the carriage. Remove inboard then outboard panel Check the tapered section of the carriage spindle for a fracture NOTE: If L or R aileron trim was required, inspect opposite side first for suspect carriage  Replace flap carriage (AMM 27-51-81/401) 

500 
Aug 01/96  27-51-0 
Page 106A 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

535 
Feb 20/85  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  27-51-0 Page 107 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Flaps operate hydraulically but alternate drive not electrically Slow flap operation Slow or fast flap operation  Defective flap alternate drive unit. Flap bypass valve in normal position, (Position 1) Defective flap limit switch No dc power at alternate flap switches No ac power Binding gearbox or transmission assembly Defective flow limiting valve  Check for power at flap alternate drive unit. If power is present, drive Check that FLAP VALVES circuit breaker is closed and that alternate flap master switch is at ARM. With switch at ARM, check for power at flap bypass valve. If power is present, valve is defective Check circuit continuity through flap limit switch Check circuit from alternate flaps switches through circuit breakers for continuity See Chapter 24, Electrical Power - Trouble Shooting Disconnect torque tubes on each side of gearbox or flap transmission and check for free rotation Check trailing edge flaps normal operating time (Ref. 27-51-171 A/T)  Replace flap alternate drive unit (Ref. 27-51-241 R/I) Replace bypass valve (Ref. 27-51-181 R/I) Replace flap limit switch. (Ref. 27-51-291 R/I) Repair wiring or replace defective switch or circuit breaker See flaps will not operate hydraulically o electrically (in this Trouble Shooting Chart) Replace flow limiting valve.(Ref. 27-51-171 R/I) 

500 
27-51-0  Feb 20/85 
Page 108 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Loose control cables Flap position indicator pointers stop between 15 and 25 units, when 25 units of flaps is selected; but continue toward 40 units when 40 units is selected Flaps do not retract automatically from 40-to 30-units when airspeed exceeds 152 to 162 knots  Low cable tension Broken control cable Flap position indicator system out of rig Faulty flap position indicator Faulty flap position transmitter Flap load limiter circuit breaker open Faulty airspeed switches  Check cable tension per 27-51-0, Fig. 501 Check cable run for broken cable Check that trailing edge flap position indicating system is in adjustment Both flap position indicator pointers do not indicate selected units One flap position indicator pointer does not indicate selected units of flap position Verify squat switch is operating. Press-to-test LOAD LIMITER TEST LIGHT. Check that test light illuminates  Adjust cable tension Replace broken cable Rerig flap position indicating system (Ref. 27-58-01, A/T) Replace flap position indicator (Ref. 27-58-41, R/I) Replace flap position transmitter (Ref. 27-58-12, R/I) Reset circuit breaker on panel P6 Replace squat switch 
　
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