I was looking at airplanes a while back and noticed that there is sometimes a wire running from about the CG near the wind to about halfway up the tail. I see this more on 737s but I have also seen it on C130s. What is this wire? To hold up the tail? I have seen: What is this wire going from mid-fuselage to the tail on this 737? but I am more interested in all of the other planes that have it too. Are there planes that actually use guy-wires for support or are all of the wires I see antennas?

  • $\begingroup$ I saw that but I was more interested in the other planes that have it too.. $\endgroup$ – dalearn Oct 17 '16 at 14:14

Sounds like an HF antenna. It absolutely isn't structural, as neither of those aircraft needs guy-wires for structural stability. (You'd also expect to see it on every example, not just some, if it were required that way.)

This article provides a lengthy discussion of HF antennae, for those interested in going deeper into the subject.

This thread has a related discussion of why not all HF antennae are of the long-wire type. Essentially, newer designs often replace the long wires.

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  • $\begingroup$ are there relatively modern planes that have guy wires? $\endgroup$ – dalearn Oct 17 '16 at 14:15
  • $\begingroup$ @dalearn Guy wires? No. Aircraft structural engineering has advanced enough that internal structure is strong enough without the guy wires. (There may be some isolated case where they're still used, but generally, no.) As for the longwire HF antenna, a buyer can probably outfit his aircraft with one if he chooses; I don't know if there is ever an economic case to do that or not thes days. $\endgroup$ – Ralph J Oct 17 '16 at 14:20
  • $\begingroup$ While this is a bit remote from the long wire use, there are still visible antennas on aircraft, most of the time for special use. Radar, magnetic loops, gamma sensors, or even usual VOR antennas. That's still the same reason they are external: better reception. $\endgroup$ – mins Oct 19 '16 at 16:35

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