If one centers the gyro-copter in a thermal and then simulates a hover facing headwind; can the gyro-copter climb up like that ? Is it technically possible or is it advisable....
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$\begingroup$ An airplane isn't capable of hovering. Did u see the video ? A glider needs to circle to soar... + A gyro-copter has much less wing area... $\endgroup$– Ayan MullickApr 30, 2016 at 15:26
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$\begingroup$ The gyrocopter in the video was hovering in 15kts winds. And gyrocopters don't stall....as far as I know.. $\endgroup$– Ayan MullickApr 30, 2016 at 16:38
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2 Answers
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I need to work out the math for this, but an issue complicating the question is that the L/D of the gyrocopter would change in the updraft. So, like a helicopter in autorotation, a gyrocopter derives lift from flow passing upwards through the rotor as it flies forward on its propeller. However, if the aircraft is in a vertical updraft, the freestream is no longer directed horizontally, but more vertically, increasing the angle of attack on the rotor blades and directing your vehicle's drag force in the upward direction (magnitude and direction, naturally, depends on your flight speed, thermal strength, etc.).
Now, gyrocopters have at cyclic and collective pitch control (generally speaking), so you could vary the collective in order to maintain a lower angle of attack, gain stall margin, and maintain altitude...or you could take advantage of the updraft on your rotor to gain altitude for "free"! This also assumes that you have sufficient collective pitch travel to get your blades at a low enough angle of attack to stop producing upward-directed thrust.
You could try to pitch over too, thus redirecting the rotor thrust vector forward and spoiling a lot of the inflow, but this is starting to get into the downside of thermalling in helicopters: namely, that, if the updraft is sufficiently strong to stall your blades (no matter the pitch setting) but also strong enough that the vertical drag on the airframe can induce a climb...it's not going to be a good day. I'm thinking primarily of updrafts that occur in the presence of thunderstorms--they have been known to be strong enough to suck aircraft up into the clouds. Similarly, if you make your way out of the thermal, they are generally surrounded by regions of strong sink because of the recirculating air (http://www.drjack.info/INFO/DELMONTE/thermal.page.html), which not only is going to load the blades completely the opposite of how they were in the thermal (so your inertial loads spike, provided you don't have mast bumping problems...in which case you lose the aircraft right then), but, if the sink is strong enough, you might find yourself in vortex-ring-state or the like and lose control--if only temporarily. At least from my brief experience in an S-300Cbi and R22, helicopters don't like to fly, so even brief periods of control loss would be bad.
So yeah, I think it's technically feasible, and, in some cases, very dangerous. I wouldn't try to set an endurance record in a rotary winged aircraft doing this.
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$\begingroup$ The rotor has no way to know which way the surrounding air is going. If you're in an updraft you'll add the updraft to your vertical rate of ascent. $\endgroup$– rbpMay 2, 2016 at 12:55
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$\begingroup$ True, the updraft will be be identically the inflow to the rotor (less the gyrocopter's horizontal velocity vector), but, if you model the updraft as a sharp-edged vertical gust, won't it result in a local change in angle of attack at the rotor? That change will necessarily be "softened" by the aircraft vertical velocity (since the gust hits the fuselage first), but it seems odd to me that the aircraft would necessarily transition upward at the speed of the updraft. Shouldn't any motion should be proportional to the aircraft's vertical drag area and the square of the updraft speed? $\endgroup$– MariusMay 3, 2016 at 3:55
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Any aircraft, from a helicopter to a 747, can soar.
All it has to do is enter and maintain its position in rising air. How the pilot accomplishes that would be based on picking a strategy for staying in the rising air, and using his skill to do it.
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2$\begingroup$ Well, provided that the air is not just raising, but raising faster than the aircraft needs to descend to maintain flight. I am not sure what kind of L/D gyrocopters have. $\endgroup$ Apr 30, 2016 at 23:12
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$\begingroup$ you don't have to shut off or null the engine to glide. $\endgroup$– rbpApr 30, 2016 at 23:15
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$\begingroup$ @rdp A 747 can soar; in theory. I'm thinking about 'for all practical purposes'. Have you seed a gyrocopter soar or come across any such video? $\endgroup$ May 1, 2016 at 10:53
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2$\begingroup$ you asked "technically possible or advisable". maybe you want to edit the question $\endgroup$– rbpMay 1, 2016 at 15:14