New gyro planned with jump takeoff?

Jean Claude;n1127899 said:
You make a mistake, Xavier
Remember that in hover, the airflow crosses the disc from the upper side which decreases the angle of attack of the blades. So, with the autorotative pitch setting, of about 3° more the lift 0, it would take 580 rpm just to gives a sufficient induced speed to lift the weight, out the ground effect, and over 650 rpm to climb to 600 ft/mn. The friction of the air on the blades now then absorb most of the power.

True... I was thinking that a moderate increase in RRPM over those necessary in s/l flight would be enough for a 'jump', but the autorotating blades work with a small pitch but a large AoA, due to the incoming wind...
 
Dick Degraw’s jumpers have a collective pitch lever just like a helicopter.

Lever on bottom, zero lift pitch for over-speeding the rotor; upper stop for jump pitch and a mid range detent for autorotation.

The A&S 18A automates that sequence by the use of pitch-cone coupling via delta-3 hinges. As the rotor slows, pitch-cone coupling automatically reduces pitch. The necessary amount of delta-3 coupling produces pitch-roll cross coupling and squirrelly behavior.
 
It would be nice to automate the process by using some tactic other than Delta-3. Flyweights, perhaps -- maybe ones that reduce pitch only once per flight, and then must be mechanically reset on the ground. Making such a gadget fool-resistant (never fool-PROOF!) can result in a process of chasing unintended consequences.
 
C. Beaty;n1127901 said:
The A&S 18A automates that sequence by the use of pitch-cone coupling via delta-3 hinges. As the rotor slows, pitch-cone coupling automatically reduces pitch. The necessary amount of delta-3 coupling produces pitch-roll cross coupling and squirrelly behavior.
The 18As I fly show adverse roll with yaw, thanks to the distribution of lateral surface area, but that's the only handling oddity I've noticed in many years of operation. I've never noticed any pitch-roll coupling or squirrelly behavior. I find them docile and forgiving.
 
Maverick said:
The new prerotator on the MTO sport 2017 is rated for 320RRPM.

I find it hard to believe that the new MTO pre-rotator can prespin the rotor to 320 rrpm. Without a variable pitch prop you would start skidding forward because of prop thrust and only partial load on the wheels long before reaching 320 rrpm. Also, the rotor is pitched at an autorotative AoA and not at zero lift. It may be "rated" for 320 rrpm, meaning that it can withstand loads at that rrpm but I doubt that one can reach 320 rrpm in normal prerotation.

Can someone with an MTO 2017 comment on this?

-- Chris.
 
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I think the A&S 18A managed jumps with fixed pitch props; the shape of the power curve of engines designed for direct drive of a prop ordinarily has a large excess of power at RPMs well below normal operating speed. Not so in the case of engines tuned for peak power at 5,000 rpm or so.

The problem of using a highly tuned engine in conjunction with a controllable pitch prop is the time required for going from flat pitch to flying pitch; things won’t wait while an electric motor drives a screw jack to crank in flying pitch. The prop needs to snap from zero thrust pitch to flying pitch.
 
A standard hydraulic variable pitch prop ought to do it, don't you think so? The electrically actuated Ivoprop won't cut it, I agree with you there.

-- Chris.
 
ckurz7000;n1127951 said:
I find it hard to believe that the new MTO pre-rotator can prespin the rotor to 320 rrpm. Without a variable pitch prop you would start skidding forward because of prop thrust and only partial load on the wheels long before reaching 320 rrpm. Also, the rotor is pitched at an autorotative AoA and not at zero lift. It may be "rated" for 320 rrpm, meaning that it can withstand loads at that rrpm but I doubt that one can reach 320 rrpm in normal prerotation.

Can someone with an MTO 2017 comment on this?

-- Chris.

They say that they can takeoff in 60 feet one up in no wind conditions. So may be it can happen?
 
ckurz7000;n1127960 said:
A standard hydraulic variable pitch prop ought to do it, don't you think so? The electrically actuated Ivoprop won't cut it, I agree with you there.

-- Chris.

I understand that hydraulic props operate from the engine’s oil pump and I think that requires passageways through the prop shaft. But yes, I think a hydraulic prop would do it.

OTH, I’m only guessing; I’ve never had occasion ot look into variable pitch props.

Cartercopter designed their own props with snap action pitch change.
 
I have a hydraulically actuated constant speed prop on my ArrowCopter. During runup you also check the pitch adjustment mechanism by working the prop lever a few times over its entire range. You can hear the prop adjusting from the noise it generates. The response is near instantaneous.

Greetings, -- Chris.
 
ckurz7000;n1127951 said:
Without a variable pitch prop you would start skidding forward because of prop thrust and only partial load on the wheels long before reaching 320 rrpm. Also, the rotor is pitched at an autorotative AoA and not at zero lift. It may be "rated" for 320 rrpm, meaning that it can withstand loads at that rrpm but I doubt that one can reach 320 rrpm in normal prerotation..

With pitched at an autorotative AoA and launched to 90 % of flying rrpm, a rotor only lifts about half the weight.
Cierva C30 could prerotate at 107% ( But without noticeable effect on the distance, as you know)
 
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C. Beaty;n1127952 said:
I think the A&S 18A managed jumps with fixed pitch props; the shape of the power curve of engines designed for direct drive of a prop ordinarily has a large excess of power at RPMs well below normal operating speed. Not so in the case of engines tuned for peak power at 5,000 rpm or so.

The problem of using a highly tuned engine in conjunction with a controllable pitch prop is the time required for going from flat pitch to flying pitch; things won’t wait while an electric motor drives a screw jack to crank in flying pitch. The prop needs to snap from zero thrust pitch to flying pitch.

No, the A&S 18A came only with a constant speed Hartzell prop. There are both two and three blade versions, but all are controllable. They are direct drive, but there is a transmission for the rotor head that determines the appropriate rpm ratio. The rotor does indeed snap from flat to flight pitch.

The adding of pitch is done by strong spring action, held in abeyance by hydraulics until the take-off button is pushed. When you push that button after a spin to 150% of flight rpm, there is a one-second delay built in between release (disengaging) of the clutch and the sudden adding of pitch, during which the engine surges to suitable take-off thrust for the prop.

For a non-jump take-off, the rotor drive clutch is released with a different button, the aircraft rolls to gather speed (for airspeed, not rotor rpm), and then the take-off button is selected.
 
WaspAir;n1127996 said:
No, the A&S 18A came only with a constant speed Hartzell prop. There are both two and three blade versions, but all are controllable. They are direct drive, but there is a transmission for the rotor head that determines the appropriate rpm ratio. The rotor does indeed snap from flat to flight pitch.

The adding of pitch is done by strong spring action, held in abeyance by hydraulics until the take-off button is pushed. When you push that button after a spin to 150% of flight rpm, there is a one-second delay built in between release (disengaging) of the clutch and the sudden adding of pitch, during which the engine surges to suitable take-off thrust for the prop.

For a non-jump take-off, the rotor drive clutch is released with a different button, the aircraft rolls to gather speed (for airspeed, not rotor rpm), and then the take-off button is selected.

Seems like a lot of work (and expensive), just to have the benefits of short take off, when the obvious alternative is a helicopter. Are there any advantages of a reltively complex short takeoff gyro like the A&S or Dick DeGraw's designs to a helicopter?
 
You might expect the maintenance costs and component lives of a jump-gyro would be more favorable than those of a helicopter. Jump takeoff requires a clutch, collective and swashplate, but the rotor drive is used only briefly during each flight. Therefore, the gyro's drive mechanism could be made a bit lighter, and/or could last longer. There's also no tail rotor or associated drive and control components in the gyro; just a dumb rudder or three. Again, a potential saving.

OTOH, the modest potential savings must be weighed against the reduced utility with the loss of the hover.
 
How about spring loaded, 3 position collective? Didn't Dennis Fetters make something like that? It was cocked before flight setting rotor pitch for prerotation followed by a trigger release for jump pitch which then returned to autorotative pitch?
 
loftus;n1128005 said:
Seems like a lot of work (and expensive), just to have the benefits of short take off, when the obvious alternative is a helicopter. Are there any advantages of a reltively complex short takeoff gyro like the A&S or Dick DeGraw's designs to a helicopter?

My first reaction is that this is a bit like asking, "why get a turbocharger on a Subaru when you could just buy the obvious alternative of a Ferrari?"
My next reaction is to suggest that a different way of looking at it, equally valid, is "why pay six figures more just to get the benefit of hovering when you don't need it?"
But to answer more directly, it's a huge benefit, and the cost differential (in purchase and maintenance/operation) is substantial.
It's also easier to fly than a helicopter and arguably safer.
In many ways, it's also easier to fly than a teetering rotor fixed collective gyro,too: there's no balancing on the mains, no rotor management to learn (you are never below 100% rpm), no problems with rough surfaces (jump over them), you never need to do a cross-wind take-off (just jump into the wind), it flies smoother, you get trimmable collective/rotor rpm, etc. etc.
 
If an A&S 18A is so marvelously functional, why was it such a dismal failure in the marketplace? Likewise, the McCulloch J-2 bankrupted the McCulloch corporation.

That’s an easy question to answer; it was ugly, although to some it may seem to be cute and cuddly.

Aesthetics is the primary determinant of success or failure of consumer products. Magni’s iteration of a Bensen with its Italian sports car styling ushered in a whole new era of gyroplane popularity.

Light airplanes are also essentially consumer products. The Cessna 150 was probably no better than its contemporaries such as Piper and Mooney but it looked racy with its swept tail and needle nosed prop spinner and consumers flocked to it, leaving the competitors in the dust.
 
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Quite true, Chuck. Also, a whole new crop of people who wanted to look slick, without the inconvenience of having to build it themselves. There seems to be a flurry of wanna-be pilots, in a hurry to get there. And they seem to be turning up in the flurry of accident participants.

But what is this perception all about? As a whole class of ugly on its own, dirt bikes are the definitive product. Yet people have been hot to jump on them for over 40 years. And it still seems to be true, beauty is truly in the eye of the beholder.

Form still follows function, and it might also be said that the functionality of the Gyrhino is a beautiful thing to behold.
 
eutrophicated1;n1128071 said:
Form still follows function, and it might also be said that the functionality of the Gyrhino is a beautiful thing to behold.

I've watched the videos of the Gyrhino 2.2 multiple times and would say you are right. And Chuck says Dick has more magic to reveal to us in the near future.
 
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