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Aircraft HF antenna vibration in Icing Conditions

Aircraft HF antenna vibration in Icing Conditions

Aircraft HF antenna vibration in Icing Conditions

Hello all
I'm new to the forum, I'm looking for information or anyone with experience with HF long wire installations. I am working with a new aircraft that HF will be installed on and they have chosen an HF "V" antenna installation. When were flying this aircraft in icing conditions and we accretion on the HF long wire we get severe vibration. I have run the tension as tight as we can and it actually exacerbates the problem. So I have to assume that vibration on the long wire is normal during ice accretion (once the ice is thrown off the vibration ceases)and that the increased tension on the cable is increases the vibration frequency and causing more vibration stress on the attach points. Does anyone have any insight on this issue.

RE: Aircraft HF antenna vibration in Icing Conditions

This is more of a mechanical design issue (resonance, mounting point stresses, etc.) than an antenna issue, per se. It sounds like you need to decrease icing on the antenna... can you run a strip heater along the radiator?

Dan - Owner

RE: Aircraft HF antenna vibration in Icing Conditions

You might want to contact an engineer at the OEM for the antenna components (mast, strain relief) and wire. An example is Dayton-Granger. To ensure that the antenna wire being used is suitable and optimum.

The fleet we're involved with has 'long wire' HF antennas, and I don't recall hearing about icing on the HF wires. The wires are coated in a very tough plastic.

RE: Aircraft HF antenna vibration in Icing Conditions

Sounds like the kind of issue that would have been investigated and solved in the 1930's and 1940's, and now buried in moldering library stacks and old articles.

Aircraft windshield and sensor (pitot tube, etc) heating is accomplished electrically by inverters that output a low frequency AC square wave (50, 60, or 400 Hz) or high voltage DC (30 to 200 Volts) typically with a capacity of around 5 watts/square inch of surface area for a windshield. I happen to design power inverters used for this.

You could try to heat the antenna by running a DC current through it to melt the ice. A large choke to feed the DC to the antenna that would block the HF from going into the inverter might work. You might have to increase the resistivity of the wire used for the antenna (go to a stainless wire ?) and this might have an effect on antenna efficiency, but generally short wire HF antennas are somewhat inefficient to begin with so the effect might not be noticeable.

Otherwise you may need to select a wire type that will flex enough that it will shatter the ice, but still stiff enough not to act like a vibrating spring.

RE: Aircraft HF antenna vibration in Icing Conditions

Most of the HF antennas I see in use on commercial aircraft slot antennas embedded in the leading edge skin of the vertical stab.

My posts reflect my personal views and are not in any way endorsed or approved by any organization I'm professionally affiliated with.

RE: Aircraft HF antenna vibration in Icing Conditions

Old aircraft used wire antennas. They must have had the problem.

Hydrophobic coatings keep water off surfaces. I wonder if that would prevent ice buildup.

On a car antenna, vertical thin posts type antennas, the wire wrapped around it prevents it from oscillating. I wonder if that would work with your antenna.

What frequency is it?

RE: Aircraft HF antenna vibration in Icing Conditions

HF frequency range is nominally 3-30 MHz, but in the context of aircraft comms is often 2 to 30 MHz. I believe that they include the "extra" 2-3 MHz range in case they want to talk to ships at sea (2182 kHz).

RE: Aircraft HF antenna vibration in Icing Conditions

You have the same issue with power lines, a combination of counter-resonant dampers at each end, and clamp on fittings that help alter the coherence of the windage forces have been used...

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