A Hawker 800XP operator, who was experiencing a squawk on both #1 and #2 HF systems, recently contacted us for support. He was not able to receive transmissions on either system.
Since both systems were exhibiting the same symptoms, the obvious place to begin troubleshooting is by focusing on components that are common between the #1 and #2 HF systems. In this instance: the dual KHF-950 HF system with a shunt antenna. The common components are the KA 162 Dual External Capacitor (or KA 160 Dual Antenna Adapter, if it is a long wire antenna installation) and the HF antenna itself.
The function of the KA 162 Dual External Capacitor is to connect the antenna to the active antenna coupler. Since the HF antenna in this installation is essentially the vertical stabilizer leading edge, the one thing to check with the antenna is proper bonding. Good bonding of the antenna, KAC 952 Power Amplifier/Antenna Coupler and KA 161 External Capacitor or KA 162 Dual Antenna Capacitor is essential for proper operation of the HF system. I cannot count the number of HF squawks that have been remedied by Duncan Aviation avionics technicians simply by going through and cleaning corroded bonding connections at the antenna or antenna coupler.
Tuning faults are also a common squawk for HF systems that have corroded or poor bonding at the antenna or antenna coupler. Bonding at the antenna coupler is done with a bonding strap, and the resistance should not exceed .003 ohms.
So if your aircraft's HF system begins to show signs of intermittent faults, take a few minutes to first check for proper bonding at the antenna and antenna coupler. Many times, this can remedy the problem and save you time and money in the process.
In light of the recent changes in the industry for Hawker operators, I want to remind you that Duncan Aviation continues to provide comprehensive Hawker aircraft service and support at all Duncan Aviation locations around the world. We are an industry leader in Hawker maintenance, structural repair, landing gear/component overhauls, engine MPIs, avionics upgrades, paint and interior. Our experience and capabilities are second to none.
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