Narrative:

This aircraft came in with a r-hand inboard flap outboard aft flap fairing off due to lightning strikes. It was found that during flap retraction from 40 units to 35 units during takeoff warning tests that a loud bang was heard. This happened twice during the test each time the flaps were moved from said position. It was also found that while watching the flap movement; the outboard flap inboard roller was extending past the area where the missing panel would normally be and would hang up on the edge of that area causing the bang and shake of the aircraft. This would not be a good thing in-flight if this was to hang up and cause flight handling issues. Callback conversation with reporter revealed the following information: reporter stated he heard the loud 'bang' noise while they were performing take-off warning tests and retracting the flaps from 40 units up to 35 units. This happened because the MEL procedure allowing the removal and deferral of the damaged inboard flap; aft flap outboard fairing; also required the removal of the outboard flap; inboard end guide roller (plunger). This part of the MEL procedure was not complied with. Reporter also stated the roller was still attached and 'catching' on the edge of the remaining exposed fairing during the flap retract cycle. This caused the inboard end of the outboard flap to preload itself; start to twist laterally and than suddenly break free; causing the loud 'bang' as that section attempted to 'catch-up' with the rest of the outboard flap during the retract cycle.

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Original NASA ASRS Text

Title: A B737-300 RT INBOARD FLAP; O/B AFT FLAP FAIRING WAS PREVIOUSLY REMOVED AND DEFERRED DUE TO LIGHTNING STRIKES. MEL PROCEDURE REQUIRING REMOVAL OF O/B FLAP; I/B END GUIDE ROLLER NOT ACCOMPLISHED.

Narrative: THIS ACFT CAME IN WITH A R-HAND INBOARD FLAP OUTBOARD AFT FLAP FAIRING OFF DUE TO LIGHTNING STRIKES. IT WAS FOUND THAT DURING FLAP RETRACTION FROM 40 UNITS TO 35 UNITS DURING TKOF WARNING TESTS THAT A LOUD BANG WAS HEARD. THIS HAPPENED TWICE DURING THE TEST EACH TIME THE FLAPS WERE MOVED FROM SAID POS. IT WAS ALSO FOUND THAT WHILE WATCHING THE FLAP MOVEMENT; THE OUTBOARD FLAP INBOARD ROLLER WAS EXTENDING PAST THE AREA WHERE THE MISSING PANEL WOULD NORMALLY BE AND WOULD HANG UP ON THE EDGE OF THAT AREA CAUSING THE BANG AND SHAKE OF THE ACFT. THIS WOULD NOT BE A GOOD THING INFLT IF THIS WAS TO HANG UP AND CAUSE FLT HANDLING ISSUES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HE HEARD THE LOUD 'BANG' NOISE WHILE THEY WERE PERFORMING TAKE-OFF WARNING TESTS AND RETRACTING THE FLAPS FROM 40 UNITS UP TO 35 UNITS. THIS HAPPENED BECAUSE THE MEL PROCEDURE ALLOWING THE REMOVAL AND DEFERRAL OF THE DAMAGED INBOARD FLAP; AFT FLAP OUTBOARD FAIRING; ALSO REQUIRED THE REMOVAL OF THE OUTBOARD FLAP; INBOARD END GUIDE ROLLER (PLUNGER). THIS PART OF THE MEL PROCEDURE WAS NOT COMPLIED WITH. REPORTER ALSO STATED THE ROLLER WAS STILL ATTACHED AND 'CATCHING' ON THE EDGE OF THE REMAINING EXPOSED FAIRING DURING THE FLAP RETRACT CYCLE. THIS CAUSED THE INBOARD END OF THE OUTBOARD FLAP TO PRELOAD ITSELF; START TO TWIST LATERALLY AND THAN SUDDENLY BREAK FREE; CAUSING THE LOUD 'BANG' AS THAT SECTION ATTEMPTED TO 'CATCH-UP' WITH THE REST OF THE OUTBOARD FLAP DURING THE RETRACT CYCLE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.