Part 25 sensor systems
Part 25 certification-basis support for a transport sensor system
This support ties a transport-category sensor system to the Part 25 paragraphs that govern it and checks that the package can carry each one. An engineering or certification lead runs it while preparing a submittal or responding to an authority finding. It reaches across the requirements trace from sensed parameter to output, the calibration evidence that fixes accuracy, the DO-160G qualification, and the installation effects that change how the sensor performs on the airframe. You receive a standards map paragraph by paragraph, a gap list tied to the specific evidence that is missing, and a closure order that starts with the findings carrying the most exposure.
When this review is needed
- A sensor is entering a submittal and its accuracy and integrity claims have to be pinned to specific Part 25 paragraphs.
- An authority questions how installation effects on the sensor were accounted for and the answer is not assembled.
- Calibration data exists but has never been traced from the sensed parameter through to the output the aircraft uses.
- A development-assurance argument under ARP4754B needs to reach the Part 25 findings it was built to satisfy.
The problem
A sensor performs against a bench specification, but Part 25 cares about the parameter as the aircraft receives it after installation, routing, and environmental exposure. The calibration reports, the requirements trace, and the qualification results usually live apart from the installation analysis, so the number the sensor produces on a test stand is not obviously the number the certification finding is about. Closing that distance late, under a finding, is where the package tends to break.
What gets reviewed
- Part 25 paragraphs applicable to the sensed parameter and the functions that consume it
- Requirements trace from the sensed quantity through processing to the delivered output
- Calibration and accuracy evidence checked against the tolerance the finding requires
- DO-160G environmental qualification mapped to the sensor's installed conditions
- Installation effects on accuracy, response, and integrity accounted for in the evidence
- Each mapped finding marked supported, partially supported, or open
What gets validated
- The requirements trace connects the sensed parameter to the aircraft-level output without an unexplained break
- Calibration evidence supports the accuracy the Part 25 finding actually requires, not a looser bench tolerance
- Installation effects such as routing, position error, and thermal exposure are addressed in the substantiation
- DO-160G categories reflect the environment the sensor experiences where it is installed
- The development-assurance level under ARP4754B matches the integrity the sensed function demands
Evidence normally required
- The certification basis and any issue papers touching the sensor
- Requirements and the trace matrix from sensed parameter to output
- Calibration procedures and accuracy test results
- DO-160G qualification reports for the sensor hardware
- Installation drawings and the position-error or routing analysis
Common discrepancies
- Calibration proven at the component that never accounts for installation position error
- A requirements trace that stops at the sensor output and never reaches the consuming function
- Qualification run to a category that understates the sensor's installed thermal or vibration environment
- An integrity claim with no development-assurance evidence to support the level asserted
What is at stake
When installation effects are not shown, an authority can treat the sensor's accuracy claim as unsubstantiated at the aircraft level even though the component data is sound. That reopens the requirements trace and the qualification basis together, and a sensor feeding a display or a protection function drags those downstream systems back into question with it.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Scope the basis
Identify the Part 25 paragraphs governing the sensed parameter and the functions that use it.
Follow the trace
Check the requirements trace from sensed quantity to delivered output for breaks.
Test the evidence
Confirm calibration, qualification, and installation effects support the finding's real tolerance.
Order the closure
Sequence open findings so accuracy and integrity items are resolved first.
What the buyer receives
- A Part 25 standards map linking each paragraph to its supporting evidence and status
- A gap list keyed to the missing calibration, trace, or installation evidence
- A closure sequence that clears the accuracy and integrity findings ahead of lower-risk items
Who uses the output
- Certification leads answering authority findings on sensor accuracy and integrity
- Engineering leads scoping the installation and trace work still owed
- Compliance managers tracking the sensor's open findings against the submittal date
How the work fits into the transaction or program
The mapping sits after the sensor's component evidence is produced and before the aircraft-level substantiation is finalized. It closes the distance between bench performance and installed performance, so the requirements trace, the calibration, and the qualification arrive at the Part 25 findings as one connected argument rather than three separate ones.
Start with a single asset
Confirm requirements trace through verification.
Jurisdiction-specific considerations
FAA Part 25 and EASA CS-25 treat sensor accuracy and integrity along similar lines, but the acceptable ways of showing installation effects can differ, so the map flags where an installation argument accepted under one authority may need to be restated for the other.
Regulatory limits
The mapping shows how the sensor's evidence meets the Part 25 basis and where it does not. It does not issue a compliance finding, approve the sensor or its installation, or make any airworthiness determination, which remain with the authority.
What this review does not cover
- Running new calibration or environmental qualification tests
- Performing the installation position-error or routing analysis itself
- Issuing any compliance finding or approval on the sensor
Specific to this review
- A sensor's certification argument lives at the installed parameter, so component calibration that ignores position error leaves the real finding unsupported.
- Because sensors feed downstream functions, an unresolved sensor gap propagates into the certification of every system that consumes its output.
- Development assurance under ARP4754B sets the integrity floor for the sensed function, and a mismatch there cannot be patched by more calibration data.
Sources
U.S. Government (eCFR). Type certificates, STCs (Subpart E), TSO authorizations (Subpart O), PMA (Subpart K), and export airworthiness approvals (Subpart L).
Federal Aviation Administration. FAA type certification process, certification basis establishment, and compliance findings.
SAE International. Development assurance process at aircraft and system level, including requirements capture and validation.
Frequently asked questions
Why is installation effect the recurring problem on sensor packages?
The sensor is qualified and calibrated as a component, but Part 25 is concerned with the parameter as the aircraft uses it. Position error, routing, and thermal exposure change that value, and the substantiation has to carry the accuracy claim to the installed condition rather than the bench.
Relevant glossary terms
Related pages
Where this fits
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