DO-160 Section 21 is one of the environmental qualification tests defined in RTCA DO-160.
What DO-160 Section 21 Covers, and Why It Exists
Section 21 verifies that equipment doesn’t emit RF noise beyond specified limits, both conducted onto power and signal lines and radiated directly. Categories are defined by location and separation distance from aircraft radio antennas: Category B covers equipment where interference just needs to be controlled to tolerable levels, while Category L applies to equipment and wiring located far from apertures like windows and far from receiver antennas, an electronic-bay installation being typical. Higher categories apply as antenna proximity increases. Notches in the radiated-emission limits specifically protect aircraft RF-sensor operating frequencies.
A Real Example: Boeing’s Emission Measurements
Boeing’s own AERO Magazine documented laboratory emission testing during a 747 navigation-anomaly investigation. One tested device’s emissions exceeded Boeing’s installed-equipment emission limits by up to 37 dB in the 150 to 700 kHz range, and tested cell phones produced emissions as much as 60 dB over the equipment limits within ADF, HF, VOR, and VHF communication bands. Boeing was measuring passenger devices against the same limits Section 21 sets for installed equipment, and was candid that it couldn’t always confirm a specific in-flight anomaly traced to a specific device. But the measured levels demonstrate concretely how much margin those emission limits are designed to protect.
Why This Increasingly Matters for Galley Equipment
Older mechanical galley equipment was largely an RF non-issue. Modern equipment with switching power supplies, motor controllers, and digital displays is a different story, those are exactly the components that generate conducted and radiated RF noise if not designed and shielded carefully. As galley equipment gets more electronics-heavy, treating Section 21 as an afterthought is a riskier bet than it used to be.
How to Mitigate This
- If the equipment includes switching power supplies or motor controllers, plan RF emissions control into the design early, not as a late fix
- Confirm the actual installation’s proximity to antennas and apertures before assuming the least restrictive category applies
Further reading: NTSB accident report archive.
How Eminent Helps: Switching supplies and motor controllers in modern galley equipment can put it over emission limits if shielding isn’t designed in early. Building RF emissions control into the design from the start, rather than chasing it at test, is the kind of thing we help teams plan. See how we support galley insert programs.
