A mechanic reported that a british aerospace hs-125-800 had a fuel leak from the APU fuel control an...

Narrative:

The flight crew wrote up; repeat write up. Discovered a fuel leak and appears to be coming from rear bay. Aircraft was fueled about 45 minutes before leak was noted. No leak was seen prior to fueling. When I arrived at the aircraft fuel was on the ground aft of the right main landing gear. The tailcone had a strong fuel odor.I was unable to produce any leakage refueling. I ran the APU and at shut down a large amount of fuel drained into the tailcone from within the APU enclosure. I discovered the fuel line elbow leaking at the output of the APU fuel control unit (FCU). The fuel was spraying on to the starter generator; exciter and hot case of the APU. The APU containment box did not contain the fuel and it ran down all the hot bleed ducting and electrical panels below the APU.I discovered the elbow had been installed improperly with the o-ring on the threads and not on the recess of the elbow. The leak was very pronounced after the APU was shut down; the shut off valve downstream closes and the fuel pump continues to turn as the APU spools down. Spraying atomized fuel on the entire APU.the containment box has no gaskets by design and the fuel leaks all over the tailcone before it reaches the enclosure overboard drain. I can't explain why this aircraft did not catch fire.the enclosure did not trap the fuel and allowed it to leak into the tailcone. There are no gaskets or sealant on the panels to prevent the fuel from leaking out.

Original NASA ASRS Text

Title: A Mechanic reported that a British Aerospace HS-125-800 had a fuel leak from the APU Fuel Control and it was not contained in the in the APU Containment Box.

Narrative: The flight crew wrote up; repeat write up. Discovered a fuel leak and appears to be coming from rear bay. Aircraft was fueled about 45 minutes before leak was noted. No leak was seen prior to fueling. When I arrived at the aircraft fuel was on the ground aft of the right main landing gear. The tailcone had a strong fuel odor.I was unable to produce any leakage refueling. I ran the APU and at shut down a large amount of fuel drained into the tailcone from within the APU enclosure. I discovered the fuel line elbow leaking at the output of the APU Fuel Control Unit (FCU). The fuel was spraying on to the starter generator; exciter and hot case of the APU. The APU containment box did not contain the fuel and it ran down all the hot bleed ducting and electrical panels below the APU.I discovered the elbow had been installed improperly with the o-ring on the threads and not on the recess of the elbow. The leak was very pronounced after the APU was shut down; the shut off valve downstream closes and the fuel pump continues to turn as the APU spools down. Spraying atomized fuel on the entire APU.The containment box has no gaskets by design and the fuel leaks all over the tailcone before it reaches the enclosure overboard drain. I can't explain why this aircraft did not catch fire.The enclosure did not trap the fuel and allowed it to leak into the tailcone. There are no gaskets or sealant on the panels to prevent the fuel from leaking out.

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.

Attributes
ACN	1383504
Time
Date	201608
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	OH
Aircraft 1
Make Model Name	BAe 125 Series 800
Flight Phase	Parked
Component
Aircraft Component	Fuel Line Fittings & Connectors
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

A mechanic reported that a british aerospace hs-125-800 had a fuel leak from the APU fuel control and it was not contained in the in the APU containment box.