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Mon, Apr 26, 2004

CarterCopter Advances Towards Mu>1.0 (Part 2)

An Update On The Amazing CarterCopter Program

By ANN Correspondent Kevin "Hognose" O'Brien

How're They Doing

After the rebuild and four months into the flight program, the CarterCopter has reached a speed of 142 mph and a Mu of .62. This is not close to the previous best (Mu = 0.87, speet 173 kt, Altitude 10,000) but the test program is going slowly. The machine has achieved a rate of climb of 750 fpm at 4,000 lb (as a standard for comparison, most gyroplanes weigh a few hundred pounds, with only such heavyweights as the RAF 2000 and AAI Sparrowhawk breaking 1,000). This rate of climb figure was with the gear down.

The attempt to break the Mu=1.0 barrier, announced last summer, will be rescheduled when the test program is far enough along. "I want six months of consistent flight before I schedule all that again," Anita told Aero-News. "All that" being the events at the Texas International Speedway that will accompany the Mu 1 attempt.

Another significant accomplishment of the demonstrator is achieving a rotor RPM of 115. "115 is what we've gotten. 60 is lowest theoretically conceivable - it would go unstable and divergent and lean. 100 is as low as we will recommend." Slowing the rotor down is a key to high-speed flight; in the CarterCopter the rotor is gradually unloaded and the little wings take more of the flight loads until they are supplying all of the lift and the rotor is almost completely unloaded. "We use the rotor as the ultimate high-lift device," Jay said. "We don't worry about loss of control, as with the rotor we can fly as slow as necessary." At the same time the wing need only be sized for high-speed flight; it need not have the compromises that jet wings have. "I'm confident that we can beat turboprop planes for speed, door to door."

"Slowing the rotor down is not new. They did tests on a Pitcairn with wings in 1934 - they couldn't control the flapping." So what has changed since 1934? We know a lot more about aerodynamics and about rigid structures; it is possible to make something that could only be conceptualized 70 years ago.

The tilting mast is another Carter innovation, and it's particularly useful on a winged gyro. The mast tilts forward for jump takeoff. There's a slight tilt back for autorotating cruise, and a greater tilt back for auto to landing. The rotor thrust vector is always aimed where it needs to be, the axis always runs through CG, and the aircraft always is level - that means that for the first time since wings have been invented, the wing is at best L/D over the machine's entire speed range! Once again Jay's explanation was needed. "It is automatic. As he goes faster he pushes forward on the stick. As we tilt this rotor - less driving force - lift drops off. The pilot doesn't realize this is happening. It's not 100% efficient -- we have a little trim on the control to keep SOME rotation at all times.

G-Force Landing Gear - Spectacularly Safe

The evolutionary ultralight Butterfly gyroplane that Larry Neal's The Butterfly, LLC, introduced at Oshkosh last August has grown into the revolutionary Monarch experimental with the addition of more power (Rotax 582 instead of 277) and a landing gear design by Neal using Carter's patented Smart Strut technology.

As installed on the gyro, the landing gear resulted from an unpleasant experience Larry had. He landed hard in a regular gyro and bent the axle. Most guys would have cursed and replaced the axles. Larry cursed, replaced the axle, and thought about how the bent axle absorbed some of the impact energy. What if you could deform an axle like that, or rather, have some way to absorb the energy - you could eliminate, Larry immediately saw, one of the largest contributing factors in gyro mishaps. He thought of the struts technology used in the Carter Copter Technology Demonstrator.

The landing gear in the CCTD has been proof-tested up to 1200 feet-per-minute descents to contact at 3000 lb gross weight. The landing gear in the Monarch has been flight-tested up to 800 feet-per-minute, which would result in substantial damage and personal injury in a conventional gyro. "It's like sitting down in a couch," Larry said.

The landing gear as now installed is a parallelogram swing arm system. It looks a bit like the gear in an Extra 400, or Lockheed F104, or Grumman F4F Wildcat - except with an eye-poking long stroke. This makes the gear dangle like a droopy moustache while the gyro is inflight, even though it is basically parallel to the ground when at rest on the ground. The parallelogram structure of the landing gear legs, almost like a Formula 1 racing suspension, holds the wheels vertical throughout the long travel of the landing gear (16 inches at the wheels). This design absorbs unprecedented amounts of energy. It neither allows the energy to damage the structure or generate a destructive bounce; even at the highest rates of descent, the gyro simply squats.

After the press conference, Jay took the time one-on-one to make sure that I understood how the Smart Strut worked. The key to safe deceleration is that the strut absorbs energy and decelerates the downward motion of the aircraft at a steady rate over the entire long stroke (16 inches) of the gear. At the extreme stroke of the strut, the valve closes, so there is no bounce-back. This accounts for the jaw-dropping way the Monarch can simply plunge to the ground, and stick there. Larry, Jay, and company have answered the age-old question, "How come we can put a man on the moon but we can't make a bounce-proof, energy-absorbing landing gear?"

The Smart Strut as used in the G-Force landing gear is the first example of a Carter technology that has been licensed by another company, The Butterfly, LLC. Carter Aviation Technologies is actively seeking more customers for this technology, which is adaptable to fixed-wing and rotary-wing aircraft.

NASA SATS/Personal Air Vehicle Contract

Everybody knows that Carter Aviation Technologies is a space-age company, but a few eyebrows went up when they were exhibiting in the NASA tent at S-n-F. But there was a good reason: Carter has received a Phase I research grant to develop a preliminary Personal Air Vehicle based on CarterCopter technology. Design goals are VTOL, 200 mph speeds, and a 1000-mile range.

Georgia Tech's Aerospace Systems Design Lab (GT/ASDL), which is also getting involved with other Carter projects, will be doing the data collection, analysis, and tool development. Georgia Tech states the question this way: Can the angular velocity of a lifting rotor in autorotation be significantly slowed to radically reduce drag in high advance-ratio flight while maintaining dynamic stability.

Or, in plain English, "Can the CarterCopter concept really lead to a revolution in S/VTOL, high-speed flight?"

The Georgia Tech investigators cautiously suggest that, "The slowed-rotor / compound appears to have the potential to exceed the performance of conventional rotorcraft while at the same time reducing the complexity and cost." In order for that to be known, a lot of data needs to be gathered and analyzed, and analysis tools for the job need to be validated - or even crafted from scratch. That's what this contract's all about.

While certification of a Personal Air Vehicle would be a long, drawn-out, and not least, expensive process, a kit might be more viable. Carter's estimate for the cost of a kit, less engine and instruments, is about $55,000 (less engine and avionics), if 1000 kits are made yearly. To put that in perspective, that number is five to ten times the number of kit gyros being completed and licensed every year, now. But a Carter PAV's appeal stretches out beyond the small, insular gyro community. Will it happen? Probably not after one study… but since when did a study ever reach any conclusion, but that another study is needed?

Army Contract

At the press conference, Jay remembered the December 2003 demo for Army officers with wry humor. "We demonstrated in front of six bigwigs from the Army, did a nice demo, and capped it off with wheels-up landing. Tore the aircraft up pretty bad." The Army apparently looked past the accident, a result of pilot error when the pilot's workload went severely nonlinear, and was able to see the promise of the underlying technology, because Carter has a new military contract with the Army. (Of course, the new automation helps the workload problem, too). The contract provides research on inflight technology (in other words, for test flights, not just paper studies) and is fiscal 2004 funding.

The contract can run up to $1,000,000 and may (or may not) lead to further contracts.

The Army wants the good and the bad news: not only whether CarterCopter technology can surpass the performance of helicopters (particularly in range and speed), but also what, if any, are the particular limitations of this technology. One thing they will be looking hard at is the efficiency of the rotor, wing, and propeller across the whole range of operations. Like the SATS/PAV contract for NASA, one by-product of this is likely to be better analysis tools and models for such unusual rotorcraft and the novel flight regimes they reach.

Some More Things…

…that didn't fit easily into the four major sections of this story.

  • Jay Carter Jr. has done an interview for EAA's "Timeless Voices of Aviation" oral history series (along with ANN E-I-C Jim Campbell).
  • Larry Neal doesn't just fly for a living, but he's on a personal crusade for gyro safety after a flying buddy tumbled to death in a kit gyroplane with known stability issues.
  • Design has begun on NxCC, the next generation Carter Copter. Objective: Take off from downtown LA, land downtown NYC without refueling.
  • The CarterCopter is featured on the BritishAirways inflight magazine in the month of May.
  • In the past, Jay Carter Jr. has always insisted that Carter Aviation Technologies is a technology company, which will profit by licensing technologies, not a products company that will build stuff based on that technology. He has always adamantly opposed a Carter-produced aircraft, for instance. But at this press conference he indicated that Carter Aviation Technologies might consider producing a personal CarterCopter in kit or flying form, in order to kick-start adoption of the technology.
To Cap and Recap

It's hard keeping up with Carter Aviation Technologies, even when you're a mere scribe and all you're trying to do is write down the ideas that come percolating out of Wichita Falls, TX. You don't have to have been bitten by the gyro bug to recognize that much of the most revolutionary thought in aviation is in and around this project. Will history say that Jay Carter Jr. and his team changed the course of aviation? Or will history record him as one of the might-have-beens whose headstones stand in the graveyard of VTOL concepts? I think and hope that the first of those questions is the one that gets a "yes". But regardless of how that comes out, what they are doing today is making history.

FMI: www.cartercopters.com

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