Part 27 communication
Part 27 certification-basis support for rotorcraft communication equipment
This support aligns communication equipment on a normal-category rotorcraft to the Part 27 paragraphs that govern its installation. A certification or engineering lead runs it while preparing a submittal or answering a finding. It covers radio performance, the antenna installation and how it behaves on the airframe, the electrical load the equipment adds and whether the rotorcraft can carry it, and the DO-160G environmental qualification. You receive a standards map keyed paragraph by paragraph, a gap list tied to the missing evidence, and a closure order weighted toward the electrical-load and antenna findings.
When this review is needed
- A communication radio is entering a Part 27 submittal and its added electrical load has to be shown as carried by the rotorcraft.
- An authority finding questions antenna installation or interference with other equipment on the airframe.
- The radio's environmental qualification has to be checked against the rotorcraft vibration and temperature environment.
- A retrofit adds transmitters and the electrical-load analysis for the rotorcraft has to be updated to include them.
The problem
A communication radio looks simple until it is installed on a rotorcraft with a constrained electrical system and a crowded antenna farm. The radio meets its own performance specification, but the load it draws and the antenna it needs have to fit a rotorcraft that was not designed around them. The electrical-load analysis and the antenna-interference picture are usually the last pieces assembled, and they are exactly what a Part 27 installation finding tends to probe.
What gets reviewed
- Part 27 paragraphs applicable to the communication function and its installation
- Radio performance traced to the evidence that supports it
- Antenna installation, placement, and interference with other airframe equipment
- Electrical-load contribution assessed against the rotorcraft's generating and distribution capacity
- DO-160G environmental qualification mapped to the rotorcraft environment
- Each communication paragraph recorded as met, partly met, or still open
What gets validated
- The added electrical load is shown to be carried under the load conditions Part 27 requires
- Antenna placement is checked for interference with navigation and surveillance equipment already installed
- Radio performance is substantiated as installed, not only at the component
- DO-160G categories reflect the rotorcraft vibration and temperature environment
- Each Part 27 paragraph in the basis links to a named document rather than an assertion
Evidence normally required
- The certification basis and issue papers for the communication installation
- Radio performance specifications and any installed test data
- Antenna placement drawings and the airframe equipment layout
- The rotorcraft electrical-load analysis to be updated
- DO-160G qualification reports for the radio
Common discrepancies
- An electrical-load analysis never updated for the transmitters being added
- Antenna placement that interferes with equipment already installed on the airframe
- Radio performance shown at the bench but not substantiated in the installed condition
- Environmental qualification run to a category short of the rotorcraft environment
What is at stake
Adding a transmitter without an updated electrical-load analysis can leave the rotorcraft unable to prove it carries the load under the required conditions, which stalls the installation approval. Antenna placement that interferes with navigation or surveillance equipment already fitted forces relocation late, when the drawings and the ground testing have to be reopened.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Scope the basis
Identify the Part 27 paragraphs governing the communication function and its installation.
Assess the load
Check the added electrical load against the rotorcraft's generating and distribution capacity.
Place the antenna
Confirm antenna placement and interference against the existing airframe layout.
Sequence the work
Order the open findings so electrical-load and antenna items are cleared first.
What the buyer receives
- A Part 27 standards map tying each communication paragraph to its evidence and status
- A gap list keyed to the missing electrical-load, antenna, or installed-performance evidence
- A closure sequence prioritizing the electrical-load and antenna-interference findings
Who uses the output
- Certification leads answering Part 27 findings on the communication installation
- Engineering leads scoping the electrical-load and antenna work still owed
- Compliance managers tracking the installation findings against the submittal date
How the work fits into the transaction or program
The mapping brings the radio's component performance together with the rotorcraft-level installation constraints it has to satisfy. It runs before the finding response so the electrical-load and antenna arguments are settled against the actual airframe, where a constrained system and a crowded antenna layout decide whether the installation holds.
Start with a single asset
Confirm requirements trace through verification.
Jurisdiction-specific considerations
Part 27 and CS-27 treat communication installations along similar lines, but electrical-load and antenna substantiation can be documented differently, so the map flags where a package accepted under one authority needs restatement for the other.
Regulatory limits
The mapping shows how the communication equipment's evidence meets the Part 27 basis and where it falls short. It does not issue a compliance finding, approve the installation, or make an airworthiness determination, all of which rest with the authority.
What this review does not cover
- Performing the rotorcraft electrical-load analysis itself
- Ground or flight testing the installed communication function
- Issuing any compliance finding or approval on the equipment
Specific to this review
- On a rotorcraft with a constrained electrical system, the load a new transmitter adds is often the deciding factor in the installation approval, not the radio's own performance.
- Antenna interference with already-installed navigation or surveillance equipment is a recurring finding, because the communication antenna is added into a layout that was already full.
- A radio qualified to a benign DO-160G category can fail the rotorcraft environment, where vibration and temperature exposure run higher than a fixed-wing installation.
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
The radio is a standard TSO unit. Why does the Part 27 installation still need this?
TSO approval covers the unit against its own standard. Part 27 covers how it behaves once installed: the load it adds to the rotorcraft, the antenna it needs in a crowded layout, and its performance in the airframe environment. Those installation findings are where the compliance work concentrates.
Relevant glossary terms
Related pages
Where this fits
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