Part 23 surveillance
Part 23 certification basis support for surveillance equipment
This support aligns the evidence for a surveillance installation with the Part 23 certification basis of the normal-category aircraft carrying it. It is aimed at suppliers and modifiers installing transponders, ADS-B transmitters, and their antennas, where the box meets its performance standard but the installed function still has to answer the aircraft basis. The work examines transmitter performance, position-source integrity for the broadcast, antenna placement and pattern, and the installation substantiation, then ties each to the basis paragraph it addresses. You receive a surveillance basis map, a list of items the evidence leaves open, and an ordered plan to close them ahead of submittal or a finding.
When this review is needed
- A transponder or ADS-B installation on a normal-category aircraft needs its evidence tied to the aircraft's Part 23 basis.
- The position source feeding the broadcast has to be shown adequate for the integrity the surveillance function demands.
- Antenna placement was set by the airframe and the resulting pattern has to be substantiated rather than assumed.
- A finding asks how the installed surveillance function meets a named basis paragraph rather than how the box performs on the bench.
The problem
Surveillance equipment carries a strong box-level performance case, but most of the certification risk lives in the installation. The position source feeding an ADS-B broadcast may not carry the integrity the transmission is supposed to advertise, antenna placement is constrained by the airframe rather than chosen freely, and the interaction between the transponder and the rest of the aircraft is exactly what the box-level test did not cover. The basis paragraphs that govern the installed function rarely map cleanly to the equipment specification.
What gets reviewed
- The Part 23 basis paragraphs the surveillance function answers at the aircraft's amendment level
- Transponder and ADS-B transmitter performance in the installed configuration
- Integrity of the position source feeding the broadcast and its match to the advertised quality
- Antenna placement, pattern, and the airframe constraints that set them
- Installation substantiation covering interference, power, and interaction with other systems
- The separation between demonstrated installed performance and box-level performance assumed to carry over
What gets validated
- Each surveillance basis paragraph has installed-configuration evidence assigned rather than box-level test data alone
- The position source integrity matches the quality the ADS-B broadcast advertises
- Antenna pattern is substantiated for the placement the airframe imposed rather than an ideal location
- Interference and electromagnetic compatibility with adjacent systems is addressed for the actual install
- Transmitter performance is confirmed at the installed antenna and cable configuration, not at the box connector
Evidence normally required
- The certification basis for the normal-category aircraft and its amendment level
- The transponder and ADS-B equipment performance and qualification reports
- The position-source description and its integrity characteristics
- Antenna placement drawings, cable runs, and any pattern analysis or test
- Installation substantiation data for power, bonding, and system interaction
Common discrepancies
- A position source whose integrity falls short of the quality the broadcast advertises
- Antenna pattern assumed from an ideal location rather than the constrained placement used
- Transmitter performance shown at the box connector but not at the installed antenna
- Electromagnetic interference with an adjacent system left unaddressed in the install substantiation
What is at stake
A surveillance package that maps well to the box standard but not to the installation basis leaves the highest-risk items unexamined until a finding forces them open. A position source that turns out short on integrity, or an antenna pattern degraded by placement, can mean re-substantiation or a hardware change after the airframe work is done, which is where the schedule and cost damage concentrates.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Set the installed basis
Establish the Part 23 basis paragraphs the surveillance function answers for this aircraft and its amendment level.
Trace to the installation
Point transmitter, position-source, and antenna evidence at the paragraphs and mark where only box-level data exists.
Substantiate placement and integrity
Check antenna pattern and position-source integrity against the constrained, installed configuration.
Prioritize the gaps
Order the open items by the airframe rework each would force and deliver a basis map for the matrix.
What the buyer receives
- A basis map linking each relevant Part 23 paragraph to the surveillance installation evidence
- A gap list of open items, with emphasis on the position-source and antenna substantiation
- A closure sequence ordering the gaps by cost and by the airframe rework each would force
Who uses the output
- Certification leads assembling the surveillance compliance argument for a normal-category modification
- Engineering teams substantiating the position source and antenna installation
- Compliance managers answering a finding on the installed surveillance function
How the work fits into the transaction or program
The mapping connects the box performance file to the installation basis for the normal-category aircraft, where the surveillance risk actually sits. Its gap list drives the antenna and position-source substantiation, and the basis map feeds the compliance matrix the applicant takes into review.
Start with a single asset
Confirm requirements trace through verification.
Aircraft-specific considerations
On normal-category airframes the antenna location is often forced by structure and skin material, so the surveillance pattern depends on the specific aircraft rather than the equipment alone. The position source available also varies by aircraft equipage, which changes whether the broadcast integrity can be met without additional substantiation, so the mapping is scoped to the actual installed configuration.
Jurisdiction-specific considerations
FAA and EASA surveillance mandates and their accepted position-source integrity requirements differ in detail and in phase-in dates, so a surveillance installation compliant for one basis can leave items open for the other. The mapping notes where the integrity requirement and its evidence change between authorities.
Regulatory limits
The work maps surveillance evidence to the basis and identifies gaps. It makes no compliance finding, grants no surveillance authorization or approval, and does not determine that the installation is airworthy. The authority decides and the applicant owns the claim.
What this review does not cover
- Granting any surveillance authorization, operational approval, or design approval
- Performing the antenna pattern test or the installed EMC campaign itself
- Any airworthiness determination on the installed surveillance equipment
Specific to this review
- The certification risk in a surveillance install is mostly in the installation, not the box: the position source and antenna placement are where basis items go unanswered.
- ADS-B broadcast integrity can only be as good as the position source feeding it, so a source that undershoots the advertised quality is a common and consequential finding.
- Antenna placement on a normal-category airframe is usually constrained by structure, so the pattern has to be substantiated as installed rather than assumed from an ideal location.
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
Our transponder is already approved. Why review the installation against Part 23?
Equipment approval covers the box. The Part 23 basis asks how the installed surveillance function performs on this aircraft, where antenna placement and the position source are set by the airframe. The mapping shows where box approval still leaves installation basis items open.
Relevant glossary terms
Related pages
Where this fits
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