Narrative:

During a recent paperwork audit; I discovered that a mathematical error had been made during the on aircraft flight control balance after paint application. Further investigation revealed the same error on 4 other aircraft. These errors occurred between dec/05 and may/06. Only the inscribed data was inaccurate on 3 of the aircraft; but the actual flight control balance was within limits on those planes. The other 2 aircraft had a total of 3 flight controls that were calculated outside of their limits. The customer has been notified. I did refer to our srm but missed the difference between the terms nose-heavy and tail-heavy; different flight controls on the same aircraft. I inadvertently calculated both the same. We have now initiated a procedure ensuring that 2 qualified flight control balance personnel will independently make calculations and confer before final data is inscribed. We are also creating a form with fill-in blanks clearly indicating the mathematical formulas/functions for each type of flight control. The form would be printed out and both personnel involved will fill in the blanks with the flight control arrival balance data; the square ft area of the flight control; the coats of paint applied; and the moment arm data. There will be separate forms for the nose heavy and the tail heavy flight controls clearly indicating the correct calculations.

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Original NASA ASRS Text

Title: A TOTAL OF 5 MD11 ACFT WERE RELEASED FROM HVY MAINT WITH FLT CTLS OUT OF BAL DUE TO MATHEMATICAL ERROR.

Narrative: DURING A RECENT PAPERWORK AUDIT; I DISCOVERED THAT A MATHEMATICAL ERROR HAD BEEN MADE DURING THE ON ACFT FLT CTL BAL AFTER PAINT APPLICATION. FURTHER INVESTIGATION REVEALED THE SAME ERROR ON 4 OTHER ACFT. THESE ERRORS OCCURRED BTWN DEC/05 AND MAY/06. ONLY THE INSCRIBED DATA WAS INACCURATE ON 3 OF THE ACFT; BUT THE ACTUAL FLT CTL BAL WAS WITHIN LIMITS ON THOSE PLANES. THE OTHER 2 ACFT HAD A TOTAL OF 3 FLT CTLS THAT WERE CALCULATED OUTSIDE OF THEIR LIMITS. THE CUSTOMER HAS BEEN NOTIFIED. I DID REFER TO OUR SRM BUT MISSED THE DIFFERENCE BTWN THE TERMS NOSE-HVY AND TAIL-HVY; DIFFERENT FLT CTLS ON THE SAME ACFT. I INADVERTENTLY CALCULATED BOTH THE SAME. WE HAVE NOW INITIATED A PROC ENSURING THAT 2 QUALIFIED FLT CTL BAL PERSONNEL WILL INDEPENDENTLY MAKE CALCULATIONS AND CONFER BEFORE FINAL DATA IS INSCRIBED. WE ARE ALSO CREATING A FORM WITH FILL-IN BLANKS CLRLY INDICATING THE MATHEMATICAL FORMULAS/FUNCTIONS FOR EACH TYPE OF FLT CTL. THE FORM WOULD BE PRINTED OUT AND BOTH PERSONNEL INVOLVED WILL FILL IN THE BLANKS WITH THE FLT CTL ARR BAL DATA; THE SQUARE FT AREA OF THE FLT CTL; THE COATS OF PAINT APPLIED; AND THE MOMENT ARM DATA. THERE WILL BE SEPARATE FORMS FOR THE NOSE HVY AND THE TAIL HVY FLT CTLS CLRLY INDICATING THE CORRECT CALCULATIONS.

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.