Part 25 certification basis
Part 25 certification-basis support for equipment on transport-category airplanes
Part 25 certification-basis support helps a supplier whose equipment installs on a transport-category airplane establish and trace the prescriptive basis its installation approval rests on. It is used by avionics and equipment teams whose article goes into airplanes certified under 14 CFR Part 25. The work fixes the applicable amendment and any special conditions, ties the equipment's failure-condition classifications to the compliance argument, and traces installation evidence to each applicable section. You receive a basis map and a gap assessment ready for review.
When this review is needed
- Equipment is being installed on a transport-category airplane and the applicable Part 25 amendment plus any special conditions have to be fixed.
- A function is novel enough that special conditions or equivalent level of safety findings apply and have to be tracked.
- The equipment's failure-condition classifications drive the compliance argument and have to be tied to the safety assessment.
- A supplier wants the Part 25 basis and the safety-driven compliance read independently before submittal.
The problem
Part 25 is prescriptive and the basis frequently carries special conditions, equivalent level of safety findings, and exemptions on top of the amendment, so the applicable requirement set is rarely just the published rule. Suppliers treat the published part as the whole basis and miss the special conditions, assign failure-condition classifications without anchoring them in the safety assessment, and leave the airplane-level effects of an equipment failure unexamined. An installation whose basis omits the special conditions or whose classifications float free draws findings that reach back into the safety work.
What gets reviewed
- The applicable Part 25 amendment for the airplane and the installation
- Special conditions, equivalent level of safety findings, and exemptions in the basis
- Failure-condition classifications for the equipment and their safety substantiation
- How each applicable section is shown to be met for the installation
- Airplane-level effects of equipment failure feeding the compliance argument
- Software and development assurance data consistent with the assigned classifications
What gets validated
- The applicable Part 25 amendment is fixed for the airplane and installation
- The basis captures any special conditions, equivalent level of safety findings, and exemptions
- Each failure-condition classification is anchored in the safety assessment
- Installation evidence maps to each applicable section and supports the claim
- Airplane-level effects of equipment failure are examined and traced
- Development assurance and software data match the assigned classifications
- Derived safety requirements are fed back into the assessment
Evidence normally required
- The airplane type data and the Part 25 amendment plus any special conditions
- The equipment specification and its intended installation
- The safety assessment and failure-condition classifications proposed
- Software and development assurance evidence for the equipment
- Prior authority correspondence if the program is in progress
Common discrepancies
- Special conditions or equivalent level of safety findings absent from the working basis
- Failure-condition classifications assigned without anchoring in the safety assessment
- Airplane-level effects of an equipment failure left unexamined
- Installation evidence that does not trace to an applicable section
- Development assurance data inconsistent with the assigned classification
- Derived safety requirements never fed back into the assessment
What is at stake
When the basis is incomplete or the failure classifications are not substantiated, the installation approval stalls while the safety argument is rebuilt. On a transport-category program that delay is expensive, and it consumes the engineering depth the next derivative was counting on.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Fix the full basis
Confirm the Part 25 amendment and capture any special conditions, equivalent level of safety findings, and exemptions.
Anchor the classifications
Tie each failure-condition classification to the safety assessment and the airplane-level effect.
Map section to evidence
Show how each applicable section is met for the installation and find the gaps.
Package for submittal
Produce a basis map, a classification record, and a prioritized closure list.
What the buyer receives
- A Part 25 certification-basis map including special conditions and findings
- A failure-condition classification record tied to the safety assessment
- A section-to-evidence trace for the installation
- A prioritized list of the basis and safety gaps to close
Who uses the output
- Certification leads preparing the installation approval data
- Safety and engineering teams closing the classification and evidence gaps
- Program management sequencing the remaining compliance work
How the work fits into the transaction or program
The work supports the supplier's own Part 25 installation program. It captures the full basis, special conditions included, and anchors the failure classifications before submittal so the safety argument holds together when a reviewer pulls on it.
Start with a single asset
Confirm requirements trace through verification.
Aircraft-specific considerations
Transport-category airplanes evaluate an equipment failure for its effect at the airplane level inside a system safety framework. The applicable basis for an equipment item depends on the airplane type data and its special conditions, so the work is anchored to the specific airplane and its safety architecture rather than to the equipment alone.
Regulatory limits
Endeavor Elements supports the applicant's certification basis and compliance evidence. It does not establish the basis or issue special conditions on the authority's behalf, classify failure conditions for the authority, or guarantee approval. The authority sets the basis and makes the findings.
What this review does not cover
- Establishing the basis or issuing special conditions on the authority's behalf
- Issuing any approval or making official compliance findings
- Performing the safety testing or qualification itself
Specific to this review
- Because the rule is prescriptive, the certification basis for a transport-category airplane commonly includes special conditions, equivalent level of safety findings, and exemptions beyond the published rule.
- Failure-condition classification drives the development assurance and safety substantiation a Part 25 equipment function needs, so a classification that is not anchored in the safety assessment undermines the whole argument.
- The airplane-level effect of an equipment failure, not just the equipment-level effect, is what the classification has to reflect, which is a step suppliers focused on their own box often skip.
- Transport-category installations sit inside a system safety framework, so derived safety requirements must be fed back into the assessment rather than closed at the equipment boundary.
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.
SAE International. Safety assessment methods (FHA, PSSA, SSA, FTA, FMEA) supporting development assurance level assignment.
Frequently asked questions
Why are special conditions part of the basis work?
On transport-category airplanes the published part is often not the whole basis. Special conditions, equivalent level of safety findings, and exemptions are added, and treating the published rule as complete is a common finding.
Do you classify the failure conditions for us?
The work anchors the classifications in the safety assessment and the airplane-level effects so they hold up in review. The authority makes the compliance findings; Endeavor Elements does not classify on its behalf.
Relevant glossary terms
Related pages
Where this fits
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