Part 27 surveillance
Part 27 certification-basis support for rotorcraft surveillance equipment
This support ties surveillance equipment on a normal-category rotorcraft to the Part 27 paragraphs and performance standards it has to meet. A certification or engineering lead runs it while preparing a submittal or answering a finding. It covers transponder and ADS-B performance, antenna placement and the pattern it produces on the airframe, and the installation substantiation that shows the surveillance function works as installed. You receive a paragraph-level standards map, a gap list keyed to the missing evidence, and a closure order that puts the antenna and performance findings first.
When this review is needed
- A transponder or ADS-B unit is entering a Part 27 submittal and its transmitted performance has to meet the surveillance standard.
- An authority finding questions antenna placement or the pattern the rotorcraft airframe produces.
- The ADS-B position source and its integrity have to be shown to meet the surveillance requirement.
- Installation substantiation is needed to show the surveillance function performs as fitted, not just on the bench.
The problem
Surveillance equipment stands or falls on what leaves the antenna, and the rotorcraft airframe, its rotor, and the mounting location all shape that pattern. The transponder or ADS-B unit is qualified as a box, the position source is specified separately, and the antenna placement is decided during installation, so the evidence that the surveillance function actually radiates and reports correctly as installed is the piece most often missing when a Part 27 finding arrives.
What gets reviewed
- Part 27 paragraphs and the applicable surveillance performance standard identified
- Transponder and ADS-B transmitted performance traced to evidence
- Antenna placement and the resulting pattern on the rotorcraft airframe
- ADS-B position source and integrity mapped to the surveillance requirement
- Installation substantiation showing the function performs as fitted
- Each surveillance paragraph recorded as met, partly met, or still open
What gets validated
- Transmitted performance is substantiated to the surveillance standard, not just to the unit specification
- Antenna placement is supported by pattern evidence that accounts for the rotorcraft structure
- The ADS-B position source meets the integrity the surveillance requirement calls for
- Installed performance is shown, rather than inferred from component qualification alone
- DO-178C level for the surveillance function matches its failure classification
Evidence normally required
- The certification basis and issue papers on surveillance performance
- The applicable surveillance performance standard and declared compliance
- Antenna placement drawings and any pattern analysis or ground-test data
- The ADS-B position-source specification and integrity data
- DO-160G and DO-178C data for the surveillance equipment
Common discrepancies
- Antenna placement chosen for convenience with no pattern evidence for the rotorcraft structure
- ADS-B position source whose integrity falls short of the surveillance requirement
- Transmitted performance shown at the unit but never substantiated as installed
- A surveillance software level below what the failure condition requires
What is at stake
A surveillance package without antenna-pattern and installed-performance substantiation draws findings that question whether the equipment reports correctly in flight. A position source that cannot show the required integrity limits the ADS-B capability the installation was meant to deliver, and rework on antenna placement late in the program can force a return to installation drawings and ground testing.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Name the standard
Identify the Part 27 paragraphs and surveillance performance standard for the function.
Reach the antenna
Trace transmitted performance and antenna placement to evidence for the rotorcraft structure.
Check the source
Confirm the ADS-B position source meets the integrity the requirement demands.
Order the closure
Sequence open findings so antenna and installed-performance items come first.
What the buyer receives
- A Part 27 standards map linking each paragraph and performance point to its evidence and status
- A gap list keyed to the missing antenna, position-source, or installed-performance evidence
- A closure sequence prioritizing the antenna and installed-performance findings
Who uses the output
- Certification leads answering Part 27 findings on surveillance performance
- Engineering leads scoping the antenna and installed-performance work still owed
- Compliance managers tracking the surveillance capability against open findings
How the work fits into the transaction or program
The mapping brings the surveillance equipment's component evidence together with the installation and antenna substantiation the airframe demands. It runs before the finding response so the transmitted-performance argument reaches the installed condition, where the rotorcraft structure actually shapes what the equipment reports.
Start with a single asset
Confirm requirements trace through verification.
Jurisdiction-specific considerations
FAA and EASA surveillance mandates for transponder and ADS-B performance overlap but differ in the specific parameters and integrity levels they require, so the map notes where a package built for one authority's surveillance requirement needs restated evidence for the other.
Regulatory limits
The mapping shows how the surveillance equipment's evidence meets the Part 27 basis and its performance standard, and where it does not. It does not issue a compliance finding, approve the installation, or make an airworthiness determination, which stay with the authority.
What this review does not cover
- Ground or flight testing of the installed surveillance function
- Running antenna-pattern measurements on the airframe
- Issuing any compliance finding or approval on the equipment
Specific to this review
- Surveillance performance is defined at the antenna, so component qualification alone never closes the installed-performance finding on a rotorcraft.
- Rotor and airframe structure distort antenna patterns in ways a fixed-wing installation does not, making placement evidence specific to the rotorcraft.
- ADS-B integrity is set by the position source, so a strong transponder cannot compensate for a source that falls short of the required level.
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 antenna placement treated as a certification issue rather than an installation detail?
Surveillance performance is measured by what the antenna radiates and receives, and the rotorcraft structure shapes that pattern. Placement is therefore part of the compliance argument, and the package needs pattern evidence for the actual installation rather than a component specification.
Relevant glossary terms
Related pages
Where this fits
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