DO-160 Section 10 is one of the environmental qualification tests in RTCA DO-160, and most galley equipment lives within arm’s reach of liquid water, every flight, by design. That makes Section 10 one of the few DO-160 sections where the galley use case is harder than the avionics use case it was largely written around, not easier.

What DO-160 Section 10 Covers, and Why It Exists

Section 10 determines whether equipment withstands liquid water, sprayed, falling, or from condensation. Four categories matter. Category Y covers condensing water. Category W covers falling or drip water, generally from condensation. Category R covers driving rain or water sprayed from any angle. Category S covers heavy fluid streams such as those in de-icing, washing, or cleaning operations. Passing Category R is considered to satisfy Category W without a separate test. Hermetically sealed equipment, permanently and airtight, may be considered to meet all waterproofness requirements without further testing.

A Real Example: The Boeing 787 Water-Intrusion AD

In May 2025, the FAA issued AD 2025-09-12, effective June 18, 2025, covering certain Boeing 787-8, -9, and -10 airplanes. It was prompted by reports of water leaking from the potable-water system, the same plumbing that feeds galleys and lavatories, due to improperly installed waterline couplings. That water reached electronics-equipment (EE) bays from above the main-cabin floor, creating risk of electrical shorts and potential loss of systems essential for safe flight. The AD requires inspecting seat tracks above the EE bays for missing, damaged, or deteriorated sealant and moisture-barrier tape, and applying corrective sealant or tape where deficiencies are found. Tellingly, this AD supersedes an earlier 2016 AD addressing the same basic failure path, the water-intrusion route had already been identified once and resurfaced on production airplanes.

The Engineering Judgment Behind It

Two design judgments sit underneath this section, and the 787 case puts pressure on both.

The first is honest category selection driven by how the equipment is actually used, not just where it sits. A galley unit that’s routinely hand-washed or wiped down with liquid cleaners is seeing Category S conditions, heavy stream and cleaning fluid, even though a quick read of the installation might suggest only condensation or drip exposure. Picking Category R or W because the nominal environment looks mild, when crew handling actually delivers Category S exposure, is how a unit passes qualification and still has water problems in service. The category should reflect the worst routine handling, not the calm drawing.

The second is recognizing that waterproofness is rarely a single barrier, it’s defense-in-depth, and the consequence of failure usually lands downstream of the leak. The 787 AD is a defense-in-depth failure: sealant, barrier tape, and drip provisions that were supposed to keep galley-and-lavatory water out of an equipment bay were missing, deteriorated, or never correctly installed, and the damage showed up in a bay nobody was watching, not at the leak source. For galley equipment, that means the design question isn’t only “is this unit sealed,” it’s “where does water go if a seal fails, and what’s underneath it.” Hermetic sealing, where achievable, is the cleanest answer because it removes the test burden entirely, but where it isn’t, the protecting barriers have to be treated as inspectable, maintainable items with a defined life, not one-time installation steps.

How to Mitigate This

• Select the category from the worst routine handling the equipment sees, if it’s hand-washed or cleaned with liquid, evaluate Category S, not just R or W
• Map where water goes if a seal or barrier fails, and what equipment sits in that path, the consequence usually lands downstream of the leak
• Treat sealant, barrier tape, and drip provisions protecting adjacent bays as inspectable, maintainable items with a defined life, not permanent install steps
• Pursue hermetic sealing where the design allows it, since it can remove the separate waterproofness test burden entirely

Further reading: FAA Airworthiness Directive 2025-09-12 (Federal Register).

How Eminent Helps: Choosing a defensible waterproofness category for equipment that’s washed and handled with liquid, and designing the leak-path and barrier strategy so a seal failure doesn’t reach something critical, is exactly the kind of galley-specific judgment we work through with clients. See how we support galley insert programs, or talk it through with us.