Fuel contamination nearly grounded a 737 at DFW yesterday

Pulled a sample from the #2 tank on a 737-800 at gate 14 and saw water beads sitting in the jar before I even added the test fluid. Turned out the sump drain valve was letting moisture seep past the o-ring after pressure washes. Anyone else seen this on the CFM56-7B fuel system lately?

2 comments

2 Comments

aaron_ellis421mo ago

Man that's a scary find. Water beads in the sample jar before test fluid is never a good sign, especially on a 737. Good catch on your part though, that could have turned into a real mess if it got past the filters or froze at altitude. I've seen similar issues with sump drain o-rings on the CFM56 line after a heavy pressure wash cycle, seems like the seals just don't always seat right after that kind of cleaning. Glad you caught it on the ground rather than in the air, that's the kind of thing that keeps everyone honest.

thomas1051mo ago

Notice the same pattern shows up everywhere, not just in aircraft. That tiny overlooked detail like a worn seal or loose drain is usually what starts the chain reaction toward a big failure lol. Pays to keep that paranoid eye on the small stuff, it always seems to save the day.