Communication equipment installation evidence for an STC approval

When this review is needed

• A radio article authorized at the equipment level now has to be installed under an STC and the airframe evidence needs a read.
• The new antenna shares a mast or a ground plane with existing equipment and co-site interference has to be answered in the data.
• The article's load has to be fitted onto an electrical budget the type design already allocates.
• The radio STC is being rolled onto a further airframe variant and the co-site and load evidence has to be revalidated for it.

The problem

A radio that passed its bench qualification still has to coexist with everything else transmitting and drawing power on the aircraft. Antenna siting has to answer co-site interference and shadowing, bonding has to meet the installed lightning zone, and the article's draw has to fit an electrical load budget that other equipment already claims. Installation evidence is usually drafted after the equipment data is settled, so these airframe-level questions surface with the least schedule left to answer them.

What gets reviewed

• Antenna siting with its co-site and shadowing substantiation against the installed configuration
• Bonding and lightning provisions for the article checked against the type design the STC modifies
• Electrical-load allocation for the article fitted onto the aircraft's existing load budget
• Interface wiring and separation traced to the aircraft's electrical assumptions
• The certification basis and means of compliance confirmed for the installed communication function
• The evidence effectivity reconciled to each airframe variant the radio STC claims

What gets validated

• Antenna placement in the installation data is supported by a co-site and shadowing assessment, not a drawing alone
• Bonding and lightning provisions meet the zone the antenna and unit sit in on this airframe
• The article's electrical load fits inside the budget the type design allocates for the affected buses
• The bench qualification the article carries covers the environment its installed location actually sees
• The effectivity claimed in the evidence covers only the airframe variants named in the radio STC application

Evidence normally required

• The radio STC installation data package draft with the certification basis it declares
• Antenna siting drawings with any co-site or shadowing analysis
• Bonding and lightning substantiation for the installation zone
• The aircraft electrical load budget and the article's stated draw
• The radio's equipment-level qualification with its authorization reference

Common discrepancies

• A new antenna sited without a co-site assessment against the equipment already sharing the mast
• An electrical load added to a bus the type design's budget cannot absorb without reallocation
• A bonding provision that does not meet the lightning zone the antenna is installed in
• Installation evidence drafted for one airframe variant and claimed across an effectivity it never analyzed

What is at stake

Installation evidence that does not reach the certification basis leaves the STC exposed where the authority looks hardest. An unsubstantiated antenna location, a load the budget cannot absorb, or a bonding provision that misses the lightning zone can force a design change after drawings are frozen, and a co-site problem found on the aircraft is far more costly than one caught in the data.

How the work runs

What the buyer receives

• A product-specific gap list on the radio installation evidence, ranked by how hard each item is to close
• A trace map from the co-site, bonding, and load claims to the certification basis and means of compliance
• A closure sequence that orders the airframe-level radio evidence against the STC filing date

Who uses the output

• Certification engineers drafting the radio STC installation data package
• Installation design leads deciding whether antenna siting or load allocation has to change
• Program managers tracking which airframe-level gaps hold up the radio STC application

How the work fits into the transaction or program

The review bridges the radio's equipment authorization and its installation approval, testing whether the bench evidence survives the aircraft it now shares antennas and buses with. Its gap list drives the airframe-level substantiation the STC needs, and its trace map ties the installation claims back to the certification basis the equipment evidence was built on.

Jurisdiction-specific considerations

An STC accepted under one authority does not automatically hold under another, and the co-site and load substantiation an authority expects can differ even where the article's equipment authorization is shared. The review notes where installation evidence built for one register needs rework for the receiving system.

Regulatory limits

The review measures the installation evidence against the certification basis and marks where it holds or falls short. It grants no STC, approves no installation, and makes no airworthiness determination on the modified aircraft.

What this review does not cover

• Producing the missing co-site, load, or bonding substantiation
• Preparing or lodging the radio STC application and its installation data package
• Any airworthiness or return-to-service determination on the aircraft after the radio is installed

Specific to this review

• A communication antenna added to a crowded airframe is a co-site problem first and a drawing dimension second, because it has to coexist with everything already transmitting nearby.
• The article's electrical load is not free capacity; it has to be fitted into a budget the type design already allocates, and a bus that looks open on paper is often already claimed.
• Bench qualification proves the radio survives a defined environment; the installation has to prove its actual location falls inside that envelope, and the two documents come from different teams.

Sources

Frequently asked questions

Relevant glossary terms

Related pages

Where this fits