Narrative:

Maintenance control added cdl 32-12 for one landing gear door missing. The aircraft was late out of the hangar which caused a 30 minute departure delay. Because the aircraft was out of service; the release had not been sent yet. Once the aircraft was signed off; local operations and the crew were requesting a fuel truck. Because the cdl had a 250 knot airspeed restriction; I had to recalculate the flight plan with the restriction. The destination airport needed an alternate at the time so I had two options for the alternate. I recalculated the release with a 250 knot restriction. The computer returned with an error and would not calculate the flight plan with the 250 knot restriction. I tried it 3 or 4 times and the results were the same. Then; I switched the performance to landing gear down. When I ran this; it worked and came back with a flight plan and fuel burn. I quickly finalized how much fuel I wanted and told operations the fuel load. When the captain received the paperwork; he questioned why the flight was filed at FL230. I told him that was the best altitude the computer calculated for the conditions of this flight. The flight departed and started heading down to it destination. A short time later; I got an ACARS saying that their FMS burn was 1000 pounds less than the release. I checked the release and did a what if scenario to calculate the burn again. I did not change any information in the what if; so it came back with the same burn as on the release. Then; I checked the performance criteria I used to calculate the 250 knot restriction. At that point; I realized that I calculated it with the landing gear down performance. I sent an ACARS back to the crew to let them know that they probably need to have the gear down to get the burn that was on the release. I had not put a remark on the release when I initially sent it that I planned the fuel burn with the landing gear down performance. The crew said they would take care of it and make it work. There was over 1000 pounds of gas they had to burn off to get under landing weight. The crew did a great job to burn off the gas before it landed. I told the dispatcher that was going to be working with the aircraft what happened when I tried to run the performance for 250 knots. Later that morning; the dispatcher said the 250 knot restriction would not calculate because the alternate was too close to the destination. Apparently; my air carrier does not have 250 knot performance numbers for this situation when an alternate is within 100 nm of the destination.

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Original NASA ASRS Text

Title: A Dispatcher reported that his Air Carrier does not have a program to calculate a flight plan for an aircraft restricted to 250 kts unless it uses gear down as a criteria. In that instance; excess fuel is uploaded and may make the aircraft overweight at its destination.

Narrative: Maintenance Control added CDL 32-12 for one landing gear door missing. The aircraft was late out of the hangar which caused a 30 minute departure delay. Because the aircraft was out of service; the release had not been sent yet. Once the aircraft was signed off; local operations and the crew were requesting a fuel truck. Because the CDL had a 250 knot airspeed restriction; I had to recalculate the flight plan with the restriction. The destination airport needed an alternate at the time so I had two options for the alternate. I recalculated the release with a 250 knot restriction. The computer returned with an error and would not calculate the flight plan with the 250 knot restriction. I tried it 3 or 4 times and the results were the same. Then; I switched the performance to landing gear down. When I ran this; it worked and came back with a flight plan and fuel burn. I quickly finalized how much fuel I wanted and told operations the fuel load. When the Captain received the paperwork; he questioned why the flight was filed at FL230. I told him that was the best altitude the computer calculated for the conditions of this flight. The flight departed and started heading down to it destination. A short time later; I got an ACARS saying that their FMS burn was 1000 pounds less than the release. I checked the release and did a what if scenario to calculate the burn again. I did not change any information in the what if; so it came back with the same burn as on the release. Then; I checked the performance criteria I used to calculate the 250 knot restriction. At that point; I realized that I calculated it with the landing gear down performance. I sent an ACARS back to the crew to let them know that they probably need to have the gear down to get the burn that was on the release. I had not put a remark on the release when I initially sent it that I planned the fuel burn with the landing gear down performance. The crew said they would take care of it and make it work. There was over 1000 pounds of gas they had to burn off to get under landing weight. The crew did a great job to burn off the gas before it landed. I told the Dispatcher that was going to be working with the aircraft what happened when I tried to run the performance for 250 knots. Later that morning; the Dispatcher said the 250 knot restriction would not calculate because the alternate was too close to the destination. Apparently; my Air Carrier does not have 250 knot performance numbers for this situation when an alternate is within 100 nm of the destination.

Data retrieved from NASA's ASRS site as of April 2012 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.