The Wing That Kept Leaking — Sealant Over a Broken Spar

The 58-year-old Grumman Turbo Mallard seaplane had been telling its operator about the right wing for months. In July 2005, three flight-log entries recorded fuel leaking at the right wing root; in September 2005, the company's own CASS meeting minutes recorded a fuel leak in the right wing dry bay three days running. The repair method, each time: remove and replace the fuel-tank sealant. The fuel was not the problem — it was the messenger, escaping through fatigue cracks in the wing structure. The wreckage showed the truth the paperwork never held: a long chordwise skin crack just outboard of right wing station 34 had at some point received a major repair — one external and three internal doublers — that appeared nowhere in the company's maintenance records, and fatigue had also broken through the rear Z-stringer and the rear spar lower cap. On 19 December 2005, seconds after takeoff from the Port of Miami, the right wing separated and the aircraft crashed into the ship channel. All 20 aboard died.

A recurring symptom in the same location is structure speaking; a maintenance program that treats each recurrence as a fresh, minor squawk — reseal, release, repeat — is a program that has stopped connecting evidence. The NTSB's probable cause named the maintenance program itself: it failed to identify and properly repair the fatigue cracks, and the FAA failed to detect the program's deficiencies. An undocumented major repair compounds it: whoever fitted those doublers hid the crack from every mechanic who came after.

1. Treat a recurring leak in a structural area as a structural investigation, not a sealant job — find why the fuel has a path.
2. Trend the discrepancies: the same defect, same location, multiple times, is a CASS red flag that mandates root-cause analysis.
3. Inspect beneath: skin cracks near highly loaded joints demand NDT of the spar, stringers and skin, not a surface fix.
4. Document every structural repair as a major repair with engineering approval — an off-the-books doubler blinds the entire future of the airframe.
5. When an aging airframe's inspections keep finding the same distress, escalate to the manufacturer or engineering authority for a structural integrity assessment.

Frequency of maintenance programs sealing over structural fatigue is not quantified in public sources; the report documents this one in detail — recurring leaks in the same areas met with repeated, ineffective sealant repairs while the cracks grew to failure.

The right wing separated in flight moments after takeoff; the aircraft crashed into the Government Cut channel off the Port of Miami. All 20 aboard — 2 flight crew and 18 passengers, many from the Bimini community the airline served — were killed; the airplane was destroyed by impact (NTSB AAR-07/04).