Narrative:

We initially had a failure of the leading edge flaps to extend normally. Alternate extension of the leading edge flaps was accomplished. Then another problem became cognizant. The flap handle was positioned to '5 degrees' for the alternate leading edge flap extension procedure. It was indicating the outboard trailing edge flaps were at 0 degrees, while the inboard trailing edge flaps were indicating 5 degrees. The flap handle controls both leading edge flaps and trailing edge flaps, but they operate differently. The leading edge flaps are pneumatically operated, the trailing edge flaps are hydraulically operated. Inboard trailing edge flaps hydraulic system #1, outboard trailing edge flaps hydraulic system #4. Initially accomplished the split trailing edge flaps procedure down to the point of 'for landing extend operable trailing edge flaps to 25 degrees on flap speed schedule.' at this point we discontinued with the split trailing edge flaps procedure and commenced the 'alternate trailing edge flap operations procedure. This seemed to be incorrect to use the procedure due to the possibility of system protection features being compromised. The outboard trailing edge were eventually extended to 25 degrees, the inboard trailing edge flaps would only extend to approximately 8 degrees. Reverted back to split trailing edge flap checklist and completed that in its entirety. Declared an emergency and made an uneventful landing. Recommend for further use that the alternate trailing edge flap operation checklist contain in bold letter caution something to the effect 'if asymmetrical/split trailing edge flap occurs do not initiate the alternate trailing edge flap operation. Accomplish the asymmetrical/split trailing edge flaps procedure.' supplemental information from acn 473099: on approach for landing, the leading edge flaps did not extend by normal means. The leading edge flaps were then extended by the alternate procedure. When the flap handle was positioned to 5 degrees, it was discovered that the outboard trailing edge flaps were still at zero degree and inboard trailing edge flaps were at the correct 5 degree position. Since this was a split flap condition, the asymmetrical trailing edge split flap procedure was accomplished to the step where the checklist states 'for landing, extend operable trailing edge flaps to 25 degrees on flap schedule.' at this point the alternate trailing edge flap operation was completed, the outboard trailing edge flaps lowered to 25 degrees and an uneventful landing accomplished. After reporting the incident to our company we were informed that the correct procedure would have been to continue with the asymmetry/split trailing edge flap checklist and attempt to lower the operable flaps with normal hydraulic pressure. Then fly the approach at vref +25 with whatever flaps resulted from this procedure. We used the alternate method because of the ambiguous terminology in the checklist. The aforementioned step in the asymmetry/split trailing edge flaps procedure should read 'for landing, lower operable trailing edge flaps hydraulically to 25 degrees on schedule using the flap handle. Do not use the alternate trailing edge flap operation.' this revision to the aom and QRH should prevent any future confusion in the event of asymmetry/split trailing edge flaps situation.

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Original NASA ASRS Text

Title: B747 CREW HAD PROBS EXTENDING BOTH THE LEADING AND TRAILING EDGE FLAPS.

Narrative: WE INITIALLY HAD A FAILURE OF THE LEADING EDGE FLAPS TO EXTEND NORMALLY. ALTERNATE EXTENSION OF THE LEADING EDGE FLAPS WAS ACCOMPLISHED. THEN ANOTHER PROB BECAME COGNIZANT. THE FLAP HANDLE WAS POSITIONED TO '5 DEGS' FOR THE ALTERNATE LEADING EDGE FLAP EXTENSION PROC. IT WAS INDICATING THE OUTBOARD TRAILING EDGE FLAPS WERE AT 0 DEGS, WHILE THE INBOARD TRAILING EDGE FLAPS WERE INDICATING 5 DEGS. THE FLAP HANDLE CTLS BOTH LEADING EDGE FLAPS AND TRAILING EDGE FLAPS, BUT THEY OPERATE DIFFERENTLY. THE LEADING EDGE FLAPS ARE PNEUMATICALLY OPERATED, THE TRAILING EDGE FLAPS ARE HYDRAULICALLY OPERATED. INBOARD TRAILING EDGE FLAPS HYD SYS #1, OUTBOARD TRAILING EDGE FLAPS HYD SYS #4. INITIALLY ACCOMPLISHED THE SPLIT TRAILING EDGE FLAPS PROC DOWN TO THE POINT OF 'FOR LNDG EXTEND OPERABLE TRAILING EDGE FLAPS TO 25 DEGS ON FLAP SPD SCHEDULE.' AT THIS POINT WE DISCONTINUED WITH THE SPLIT TRAILING EDGE FLAPS PROC AND COMMENCED THE 'ALTERNATE TRAILING EDGE FLAP OPS PROC. THIS SEEMED TO BE INCORRECT TO USE THE PROC DUE TO THE POSSIBILITY OF SYS PROTECTION FEATURES BEING COMPROMISED. THE OUTBOARD TRAILING EDGE WERE EVENTUALLY EXTENDED TO 25 DEGS, THE INBOARD TRAILING EDGE FLAPS WOULD ONLY EXTEND TO APPROX 8 DEGS. REVERTED BACK TO SPLIT TRAILING EDGE FLAP CHKLIST AND COMPLETED THAT IN ITS ENTIRETY. DECLARED AN EMER AND MADE AN UNEVENTFUL LNDG. RECOMMEND FOR FURTHER USE THAT THE ALTERNATE TRAILING EDGE FLAP OP CHKLIST CONTAIN IN BOLD LETTER CAUTION SOMETHING TO THE EFFECT 'IF ASYMMETRICAL/SPLIT TRAILING EDGE FLAP OCCURS DO NOT INITIATE THE ALTERNATE TRAILING EDGE FLAP OP. ACCOMPLISH THE ASYMMETRICAL/SPLIT TRAILING EDGE FLAPS PROC.' SUPPLEMENTAL INFO FROM ACN 473099: ON APCH FOR LNDG, THE LEADING EDGE FLAPS DID NOT EXTEND BY NORMAL MEANS. THE LEADING EDGE FLAPS WERE THEN EXTENDED BY THE ALTERNATE PROC. WHEN THE FLAP HANDLE WAS POSITIONED TO 5 DEGS, IT WAS DISCOVERED THAT THE OUTBOARD TRAILING EDGE FLAPS WERE STILL AT ZERO DEG AND INBOARD TRAILING EDGE FLAPS WERE AT THE CORRECT 5 DEG POS. SINCE THIS WAS A SPLIT FLAP CONDITION, THE ASYMMETRICAL TRAILING EDGE SPLIT FLAP PROC WAS ACCOMPLISHED TO THE STEP WHERE THE CHKLIST STATES 'FOR LNDG, EXTEND OPERABLE TRAILING EDGE FLAPS TO 25 DEGS ON FLAP SCHEDULE.' AT THIS POINT THE ALTERNATE TRAILING EDGE FLAP OP WAS COMPLETED, THE OUTBOARD TRAILING EDGE FLAPS LOWERED TO 25 DEGS AND AN UNEVENTFUL LNDG ACCOMPLISHED. AFTER RPTING THE INCIDENT TO OUR COMPANY WE WERE INFORMED THAT THE CORRECT PROC WOULD HAVE BEEN TO CONTINUE WITH THE ASYMMETRY/SPLIT TRAILING EDGE FLAP CHKLIST AND ATTEMPT TO LOWER THE OPERABLE FLAPS WITH NORMAL HYD PRESSURE. THEN FLY THE APCH AT VREF +25 WITH WHATEVER FLAPS RESULTED FROM THIS PROC. WE USED THE ALTERNATE METHOD BECAUSE OF THE AMBIGUOUS TERMINOLOGY IN THE CHKLIST. THE AFOREMENTIONED STEP IN THE ASYMMETRY/SPLIT TRAILING EDGE FLAPS PROC SHOULD READ 'FOR LNDG, LOWER OPERABLE TRAILING EDGE FLAPS HYDRAULICALLY TO 25 DEGS ON SCHEDULE USING THE FLAP HANDLE. DO NOT USE THE ALTERNATE TRAILING EDGE FLAP OP.' THIS REVISION TO THE AOM AND QRH SHOULD PREVENT ANY FUTURE CONFUSION IN THE EVENT OF ASYMMETRY/SPLIT TRAILING EDGE FLAPS SIT.

Data retrieved from NASA's ASRS site as of July 2007 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.