King Air 350 ADS-B Out compliance — STC options, cost, and what to install today
Six years past the mandate, the install options have consolidated. Here's what's actually flying.
Why this is still a live topic
ADS-B Out has been mandated for US Class A/B/C airspace since January 1, 2020. A non-trivial number of King Air 350s in fleet service still operate VFR-only or in airspace that doesn't require it — flight schools, ag operators, and some short-haul charters.
When those airframes get sold or move into 135 service, the new operator has to install ADS-B Out. The STC market is mature, the install is well-understood, and parts come off the shelf — but the upgrade path depends heavily on what's already in the panel.
The three active STC paths
Garmin GTX 3000 (1090ES) with existing GPS source. If the aircraft has a TSO-C145/146 GPS already (GNS 530W, GTN 650/750, or G1000), the GTX 3000 just bolts into the existing transponder bay. Cost: $8K-12K hardware + $10K labor.
L3 Lynx NGT-9000 (1090ES + UAT in/out). Combines transponder + ADS-B in/out. Higher-end install, includes weather/traffic display capability. Cost: $13K-18K hardware + $15K labor.
Full G1000 NXi retrofit. Garmin's STC for King Air 350 includes ADS-B as part of the bundle. Heavy install ($350K+) but compelling if other avionics are also due for refresh. Adds glass cockpit, WAAS LPV approaches, and a 1-for-1 replacement of the legacy steam gauge or Pro Line II panel.
What comes off — and what it's worth
Removed transponders and old GPS units have real residual value. A clean Garmin GNS 530W comes off the panel and sells for $4K-6K on the used-serviceable market with trace documents. Honeywell KT-76C transponders fetch $200-400. Plan the take-out parts into your install budget — many shops will trade-in against the new hardware to offset labor.
List your removed avionics on Haven Jet Parts. Used-serviceable LRUs with 8130-3 tags move quickly in the King Air aftermarket — especially to operators still flying Pro Line II who haven't upgraded yet.
Common gotchas on the install
Position source TSO compliance. ADS-B Out requires TSO-C145/146 GPS. Pre-WAAS GPS units (KLN 90B, GNS 430 non-W, etc.) don't qualify and need replacement before the transponder swap matters.
Antenna placement. Some King Air 350 airframes need a new bottom-mounted transponder antenna for adequate signal coverage at typical cruise altitudes. Budget a half-day extra labor if your shop hasn't done this airframe before.
Pro Line II integration. Some Pro Line II installations have weird PFD inputs that don't play nicely with newer transponders. Get a shop with Pro Line II + King Air time before committing.
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