Narrative:

Our airline utilizes computerized takeoff and landing weight calculations for their normal operation. They use manual calculations whenever the computer is down. The computer is capable of handling some MEL performance corrections. One afternoon I was reviewing the B757 mels. MEL xd autospd brake system performance penalty can be handled by the computer. The code for the correction is 'gsp.' I noticed MEL xb spoiler system, ground spoilers. I asked the company operations engineering if the 'gsp' code could be applied to MEL xb too. I was advised that it would be conservative but I could use 'gsp' for MEL xb. I advised the line dispatchers that evening. This morning, I had an additional question for operations engineering regarding MEL xa. I pointed out the differences between the takeoff and landing calculations for MEL xb ground spoilers and MEL xc flight spoilers. The engineer advised me that yesterday he didn't focus on the takeoff penalty. Based on his review MEL xb should not have computerized relief. The penalty should be calculated manually. Upon checking current mels I discovered that one aircraft had MEL xb applied this morning. It flew both legs of a flight with the 'gsp' coded into the computer. The takeoff weight should have been calculated manually. The computerized landing weight was conservative. I enclosed the computerized weights. If you subtract the 3200 pounds takeoff penalty from the computerized maximum takeoff weight, you'll see that the aircraft was well within its performance capability. I should have caught this error. Since operations engineering is responsible for company aircraft performance, I let them make the decision. I should have thought through the aircraft certification process myself and realized that automatic speed brake performance is not considered for takeoff. Some confusion was created by the code 'gsp.' this code will be changed in the upcoming rewrite of our company's computerized takeoff and landing program.

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Original NASA ASRS Text

Title: AN AIRLINE'S COMPUTERIZED SYS FOR B757 TKOF AND LNDG WT CALCULATIONS WAS NOT SET UP TO ATTACH A REQUIRED MEL PENALTY FOR OPS WITH SPOILER SYS-GND SPOILERS INOP. THE COMPANY'S DISPATCH TRAINER DISCOVERED THE PROB AFTER AN ACFT HAD ALREADY BEEN DISPATCHED FOR 2 FLTS. THE ACFT DID NOT EXCEED ANY LIMITATIONS, BUT THE CALCULATED MAX TKOF WT HAD NOT BEEN ADJUSTED AS REQUIRED FOR OPS UNDER THE MEL.

Narrative: OUR AIRLINE UTILIZES COMPUTERIZED TKOF AND LNDG WT CALCULATIONS FOR THEIR NORMAL OP. THEY USE MANUAL CALCULATIONS WHENEVER THE COMPUTER IS DOWN. THE COMPUTER IS CAPABLE OF HANDLING SOME MEL PERFORMANCE CORRECTIONS. ONE AFTERNOON I WAS REVIEWING THE B757 MELS. MEL XD AUTOSPD BRAKE SYS PERFORMANCE PENALTY CAN BE HANDLED BY THE COMPUTER. THE CODE FOR THE CORRECTION IS 'GSP.' I NOTICED MEL XB SPOILER SYS, GND SPOILERS. I ASKED THE COMPANY OPS ENGINEERING IF THE 'GSP' CODE COULD BE APPLIED TO MEL XB TOO. I WAS ADVISED THAT IT WOULD BE CONSERVATIVE BUT I COULD USE 'GSP' FOR MEL XB. I ADVISED THE LINE DISPATCHERS THAT EVENING. THIS MORNING, I HAD AN ADDITIONAL QUESTION FOR OPS ENGINEERING REGARDING MEL XA. I POINTED OUT THE DIFFERENCES BTWN THE TKOF AND LNDG CALCULATIONS FOR MEL XB GND SPOILERS AND MEL XC FLT SPOILERS. THE ENGINEER ADVISED ME THAT YESTERDAY HE DIDN'T FOCUS ON THE TKOF PENALTY. BASED ON HIS REVIEW MEL XB SHOULD NOT HAVE COMPUTERIZED RELIEF. THE PENALTY SHOULD BE CALCULATED MANUALLY. UPON CHKING CURRENT MELS I DISCOVERED THAT ONE ACFT HAD MEL XB APPLIED THIS MORNING. IT FLEW BOTH LEGS OF A FLT WITH THE 'GSP' CODED INTO THE COMPUTER. THE TKOF WT SHOULD HAVE BEEN CALCULATED MANUALLY. THE COMPUTERIZED LNDG WT WAS CONSERVATIVE. I ENCLOSED THE COMPUTERIZED WTS. IF YOU SUBTRACT THE 3200 LBS TKOF PENALTY FROM THE COMPUTERIZED MAX TKOF WT, YOU'LL SEE THAT THE ACFT WAS WELL WITHIN ITS PERFORMANCE CAPABILITY. I SHOULD HAVE CAUGHT THIS ERROR. SINCE OPS ENGINEERING IS RESPONSIBLE FOR COMPANY ACFT PERFORMANCE, I LET THEM MAKE THE DECISION. I SHOULD HAVE THOUGHT THROUGH THE ACFT CERTIFICATION PROCESS MYSELF AND REALIZED THAT AUTO SPD BRAKE PERFORMANCE IS NOT CONSIDERED FOR TKOF. SOME CONFUSION WAS CREATED BY THE CODE 'GSP.' THIS CODE WILL BE CHANGED IN THE UPCOMING REWRITE OF OUR COMPANY'S COMPUTERIZED TKOF AND LNDG PROGRAM.

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.