Service difficulty report · Frame · Boeing 7472D7B

Difficulty date
July 19, 2011
Submitted
August 10, 2011
Operation
Air carrier
Aircraft
N524MC
Make and model
Boeing 7472D7B
Aircraft serial
21784
Aircraft time
105,635 hours, 21,872 cycles
Part
Frame
Part number
65B1709524
Condition
Cracked
Location
Bs 320
Stage of operation
IN
How discovered
V
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

DURING C4/A6 CHECK, INSP DETECTED 2 EACH CRACKS ON THE RT SIDE , BS 320 FRAME AT S-15R CUTOUT. THE FIRST CRACK IS FOUND ON THE WEB LAYER ONLY AND IS APPROX 2 IN LONG RUNNING INBD AND DOWNWARD. THE SECOND CRACK IS ALSO ON THE WEB LAYER ONLY AND IS APPROX 0.50 INCH LONG RUNNING OTBD AND UPWARDS TO ADJACENT FASTENER HOLE. WHILE PERFORMING OPEN HOLE INSP ON THE REPAIR AREA, ADDITIONAL 4 EA CRACKS WERE DETECTED ON BS 320 FRAME. 3 CRACKS ARE LOCATED ON THE INBD FLANGE OF THE FRAME ORIGINATING FROM FASTENER HOLES AND RUNNING OTBD AND 1 EA CRACK (APPROX 0.375INCH) RUNNING INBD. REFER TO FIG 1 FOR A SKETCH OF CRACK LOCATIONS. STOP DRILLED CRACKS WITH 0.250 DIA. HOLES; PERFORMED INSPECTION OF REPAIRED AREA TO ENSURE DEFECT FREE CONDITION AND FABRICATE REPAIR ANGLES; HEAT TREAT TO T6 AFTER FORMED AND INSTALLED REPAIR ANGLES.

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