13 — Aircraft power: qualify the complete input path

DO-160 Display Qualification | A-P02 — Draft / Not Released

Learning objective: Allocate Sections 16–18 to aircraft interfaces and internal display functions.

Trace power from connector to image

At the complete display boundary, the power connector, input protection, filter, converter, return paths, internal rails, processor, backlight and heater all affect the response. A regulated panel supply on a component bench does not exercise this chain. For a split display/controller architecture, identify each powered unit and the representative interconnections.

Section 16 addresses power input characteristics and disturbances for the selected supply/category. Section 17 addresses voltage spikes. Section 18 addresses audio-frequency conducted susceptibility on power inputs. These are different exposure families; passing one is not evidence for every disturbance on the aircraft bus.

Select exact voltage/frequency categories, waveforms, source conditions, durations and interface arrangements from the adopted standard and aircraft specification. Nominal 28 VDC is an architecture description, not a complete transient envelope. Do not substitute a familiar automotive load-dump waveform for an allocated aircraft test without a documented requirement comparison.

Mode selection

Maximum brightness may maximize load, but a dimming mode may produce a different current spectrum. Include startup, permitted heater/backlight combinations, graphics load, cooling and any redundant-power transfers. Define which failures require uninterrupted display function and where a specified recovery is permitted. Measure power at the relevant equipment terminals, accounting for test harness effects.

Observe function and state

Monitor dynamic imagery, validity indications, input processing, touch/control output, resets, configuration retention and required recovery time. Record input waveforms and output events on a common time base when necessary. A brief image blank followed by recovery must be evaluated against the actual requirement, not treated automatically as acceptable.

Worked investigation

The external input remains within its prescribed test waveform, but the internal 5 V rail dips and the display reboots. The cause may be the converter, protection thresholds, wiring impedance, load transient or power sequencing. Diagnose the complete path. If firmware changes the recovery behavior, assess the affected qualification and functional evidence before retesting.

Contract output

State the supply architecture and category, each applicable subtest, test point, load/mode, monitoring resolution, permitted interruption and recovery, protection behavior and retained data. Include how test-support equipment is isolated so its grounding does not unintentionally bypass the production return or filter.