Narrative:

Aircraft had 'anti-skid' status message for normal and alternate system appear approximately 10 minutes prior to scheduled block time. When we received the original weight and balance the performance data sent was for a thrust setting assumed off of a D-2 power setting. The mechanic subsequently deferred the anti-skid/auto brake system which would then require a takeoff at max thrust. The captain called the dispatcher to keep her in the loop; to add the deferral to the release; and to have her send new performance data based on the new MEL. This aircraft has an older ACARS unit requiring 'free text' to make a new takeoff performance report. I entered the takeoff performance report for max thrust because the dispatcher said she was having trouble/unable to send the data to us with the new MEL applied. The performance data that was sent back from my free text takeoff performance report request for a maximum takeoff did not have the MEL for the anti-skid included. The captain discussed this with the dispatcher and dispatch took in excess of 20 minutes to gives us a 'live' calculation since they were somehow unable to send the new performance data over the ACARS with the associated MEL taken in to account and displayed on the performance data screen. The performance data given to us over the phone with the MEL applied from the dispatcher for the 'live' calculation was almost identical to the data sent via the ACARS that did not include the MEL. We blocked out almost an hour and a half late due to this issue and made an uneventful flight to ZZZ. Last night; the captain informed me that he had followed up on this issue and contacted dispatch to discuss the 'live' calculation given to us. The dispatcher told him that they had 'no idea' how to include the MEL in to a live calculation. This was very unsettling to me and made me realize why the performance data/V speeds were almost identical to the data without the MEL applied. With the autobrakes/antiskid deferred it would make sense to me that the V speeds/ flap settings should be different and more conservative (lower V1 and/or flaps 15) than without the MEL applied on a wet runway due to increased stopping distance in the event of a rejected takeoff. I feel we may have inadvertently used the wrong performance data for takeoff due to an incorrect 'live' calculation; thus the reason for this report. The landing data request prior to landing in minneapolis appeared to be correct and the MEL was displayed on the ACARS. The captain indicated to me last night after following up with dispatch that the dispatcher he spoke with (not our dispatcher for our flight) told him that they were able to apply the MEL to a landing data request; but not a 'live' calculation for takeoff. Dispatch needs to know how to send takeoff performance data via ACARS or given via 'live' calculation with performance limiting mels applied when the aircraft status changes from what is originally planned so crews can takeoff with the correct data/speeds.

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Original NASA ASRS Text

Title: B757 First Officer reported that an anti-skid MEL issue was not able to be included in a takeoff performance data calculation which caused the crew to takeoff with incorrect data.

Narrative: Aircraft had 'anti-skid' status message for normal and alternate system appear approximately 10 minutes prior to scheduled block time. When we received the original weight and balance the performance data sent was for a thrust setting assumed off of a D-2 power setting. The mechanic subsequently deferred the anti-skid/auto brake system which would then require a takeoff at Max Thrust. The Captain called the dispatcher to keep her in the loop; to add the deferral to the release; and to have her send new performance data based on the new MEL. This aircraft has an older ACARS unit requiring 'free text' to make a new takeoff performance report. I entered the takeoff performance report for max thrust because the dispatcher said she was having trouble/unable to send the data to us with the new MEL applied. The performance data that was sent back from my free text takeoff performance report request for a MAX takeoff did not have the MEL for the anti-skid included. The Captain discussed this with the dispatcher and dispatch took in excess of 20 minutes to gives us a 'live' calculation since they were somehow unable to send the new performance data over the ACARS with the associated MEL taken in to account and displayed on the performance data screen. The performance data given to us over the phone with the MEL applied from the dispatcher for the 'live' calculation was almost identical to the data sent via the ACARS that did not include the MEL. We blocked out almost an hour and a half late due to this issue and made an uneventful flight to ZZZ. Last night; the Captain informed me that he had followed up on this issue and contacted dispatch to discuss the 'live' calculation given to us. The dispatcher told him that they had 'no idea' how to include the MEL in to a live calculation. This was very unsettling to me and made me realize why the performance data/V speeds were almost identical to the data without the MEL applied. With the autobrakes/antiskid deferred it would make sense to me that the V speeds/ flap settings should be different and more conservative (lower V1 and/or Flaps 15) than without the MEL applied on a wet runway due to increased stopping distance in the event of a rejected takeoff. I feel we may have inadvertently used the wrong performance data for takeoff due to an incorrect 'live' calculation; thus the reason for this report. The landing data request prior to landing in Minneapolis appeared to be correct and the MEL was displayed on the ACARS. The Captain indicated to me last night after following up with dispatch that the dispatcher he spoke with (not our dispatcher for our flight) told him that they were able to apply the MEL to a landing data request; but not a 'live' calculation for takeoff. Dispatch needs to know how to send takeoff performance data via ACARS or given via 'live' calculation with performance limiting MELs applied when the aircraft status changes from what is originally planned so crews can takeoff with the correct data/speeds.

Data retrieved from NASA's ASRS site 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.