Narrative:

Description: planned arrival fuel 9700 pounds; actual touchdown fuel 7400 pounds. MEL 24-00-01 (engine generator system). Takeoff minimum fuel required was 35524 pounds. Actual takeoff fuel was 36000 pounds. WX was cavu and flight profile was flown exactly as flight planned. APU was running for the entire flight in compliance with MEL. 1000 pounds fuel carried for MEL (200 pounds/hour as per MEL). Forecast winds were accurate. Comparing actual fuel burn to flight plan estimate showed a 1300 pounds discrepancy after 1 hour 22 mins of flight. The discrepancy continued to increase to 1900 pounds after 2 hours 25 mins; when a position report was sent via ACARS. Dispatch failed to note or comment on the increased fuel burn. The discrepancy grew to 2100 pounds after 2 hours 55 mins of flight when 'minimum fuel' was declared with ATC. WX and traffic allowed for an expedited visual approach. Fuel at touchdown was 7400 pounds (2300 pounds less than flight plan forecast). Cause: perhaps the actual fuel burn from the APU is greater than the advertised numbers in the MEL. If historical data from transcontinental flight plans shows similar discrepancies; flight planning with MVFR arrival fuel should be revisited. Dispatching aircraft with an inoperative generator through 2 maintenance bases may comply with the provisions of the MEL; but is not in keeping with a culture of safety that is mandated by the company mission statement. Obviously the best suggestion is to repair a faulty engine driven generator at the first available maintenance facility -- especially when the penalty for APU fuel burn is such a high cost item. Failing to do that; it may have been prudent for dispatch to allow for a greater amount of contingency fuel.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B757-200 PILOT COMMENTS THAT FLYING WITH AN MEL'ED ENG GEN ON A PRECISE PROFILE THE ACFT LANDED WITH 2300 LBS LESS FUEL THAN PLANNED.

Narrative: DESCRIPTION: PLANNED ARR FUEL 9700 LBS; ACTUAL TOUCHDOWN FUEL 7400 LBS. MEL 24-00-01 (ENG GENERATOR SYS). TKOF MINIMUM FUEL REQUIRED WAS 35524 LBS. ACTUAL TKOF FUEL WAS 36000 LBS. WX WAS CAVU AND FLT PROFILE WAS FLOWN EXACTLY AS FLT PLANNED. APU WAS RUNNING FOR THE ENTIRE FLT IN COMPLIANCE WITH MEL. 1000 LBS FUEL CARRIED FOR MEL (200 LBS/HR AS PER MEL). FORECAST WINDS WERE ACCURATE. COMPARING ACTUAL FUEL BURN TO FLT PLAN ESTIMATE SHOWED A 1300 LBS DISCREPANCY AFTER 1 HR 22 MINS OF FLT. THE DISCREPANCY CONTINUED TO INCREASE TO 1900 LBS AFTER 2 HRS 25 MINS; WHEN A POS RPT WAS SENT VIA ACARS. DISPATCH FAILED TO NOTE OR COMMENT ON THE INCREASED FUEL BURN. THE DISCREPANCY GREW TO 2100 LBS AFTER 2 HRS 55 MINS OF FLT WHEN 'MINIMUM FUEL' WAS DECLARED WITH ATC. WX AND TFC ALLOWED FOR AN EXPEDITED VISUAL APCH. FUEL AT TOUCHDOWN WAS 7400 LBS (2300 LBS LESS THAN FLT PLAN FORECAST). CAUSE: PERHAPS THE ACTUAL FUEL BURN FROM THE APU IS GREATER THAN THE ADVERTISED NUMBERS IN THE MEL. IF HISTORICAL DATA FROM TRANSCONTINENTAL FLT PLANS SHOWS SIMILAR DISCREPANCIES; FLT PLANNING WITH MVFR ARR FUEL SHOULD BE REVISITED. DISPATCHING ACFT WITH AN INOP GENERATOR THROUGH 2 MAINT BASES MAY COMPLY WITH THE PROVISIONS OF THE MEL; BUT IS NOT IN KEEPING WITH A CULTURE OF SAFETY THAT IS MANDATED BY THE COMPANY MISSION STATEMENT. OBVIOUSLY THE BEST SUGGESTION IS TO REPAIR A FAULTY ENG DRIVEN GENERATOR AT THE FIRST AVAILABLE MAINT FACILITY -- ESPECIALLY WHEN THE PENALTY FOR APU FUEL BURN IS SUCH A HIGH COST ITEM. FAILING TO DO THAT; IT MAY HAVE BEEN PRUDENT FOR DISPATCH TO ALLOW FOR A GREATER AMOUNT OF CONTINGENCY FUEL.

Data retrieved from NASA's ASRS site as of May 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.