The KGUC website notes that they have a tether for helicopter testing. From what I can tell this testing has something to do with hot and high conditions, but I don't know what the purpose is of testing with a tether. Here is a video of testing being performed. What is tether testing for?
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$\begingroup$ Interesting question, I can see the load cell mounted on the tether, they may be measuring lift at various configurations. It would be interesting to know how they compensate the readings for being so close to the ground. Enstrom Helicopter has a manufacturing facility in my hometown but I haven't noticed any kind of test pad like this at their facility. $\endgroup$– Ron BeyerCommented Mar 3, 2017 at 4:58
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1$\begingroup$ @mins I didn't even think of reading the video description. [smacks forehead] $\endgroup$– TomMcWCommented Mar 3, 2017 at 14:16
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1 Answer
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The cable is attached to the helicopter with a tensionometer. This can be used to vary the effective weight of the helicopter by varying the tension applied to the cable.
The cable length can also be varied from 0 height, to hovering in ground effect and hovering out of ground effect.
This test enables data to be gathered quickly for the helicopter performance from minimum to maximum weight on the ground, IGE hover and OGE hover without the pilot having to control height (since the cable does this) and with quick and easy changes to the effective weight without having to add ballast to the helicopter for each weight.
This test is a simple and quick, albeit risky, way to gather data on hover and climb performance throughout the weight range.
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$\begingroup$ Is this something done for a specific airframe? $\endgroup$– TomMcWCommented Mar 3, 2017 at 14:11
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$\begingroup$ It's a general technique AFAIK. There might be some limitations such as is there a hard point on the underside of the aircraft (like a cargo hook) that can take the load? $\endgroup$– SimonCommented Mar 3, 2017 at 14:47