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Wed, Apr 05, 2006

Bensen Days: LFINO Leaps Into Public View

Innovative Jump Gyro Points Way To One Possible Future

by Aero-News Senior Correspondent Kevin R.C. "Hognose" O'Brien

Figuring out why Dick DeGraw designs unusual rotorcraft is easy, if you talk to him. "Technology demonstrator? Yeah, you could call it that." Dick builds because he loves solving engineering problems. Each one he solves creates even more unexpected problems, and he likes solving them, too.

When he's successful, he's built something that never existed before. "So you are really the classic case addressed by the FARs," we suggested, "which allow amateur-built aircraft to be built for education and recreation?" DeGraw considered that for a moment, and broad grin spread over his face as he did. "Education and recreation! Yes, that's it exactly." When describing things he's designed, built, or helped build, he lights up in innocent glee; you're infected by his grin and nearly as glad as he is that he's built this thing.

So what has he built? LFINO.

LFINO (pronounced "'ell if I know," and parsed out as a backronym for "Leap Flight In Normal Operation"), is a unique gyroplane that incorporates technology that DeGraw has long promoted, including full- time partially-powered rotors, a fully articulated rotor system of his own design, and a collective that can be used for jump takeoffs and for gentle, no-roll landings.

But Dick DeGraw, who has built a number of fascinating rotorcraft over the years, is only half of the partnership that built LFINO. The other half is Ernie Boyette, the proprietor of Rotor Flight Dynamics (RFD), makers of Dragon Wings rotors and of Dominator gyroplanes.

DeGraw was responsible for the rotor system design, controls and powertrain; he also designed the tail, which is blind-riveted aluminum on an aluminum tube structure. Boyette designed the energy- absorbing landing gear, the aluminum frame, and the unstressed composite 2-seat cabin. "I don't really know how to work with fiberglass like that, that's all Ernie's work," DeGraw says, pointing out the tight fit of the parts.

The cabin was a first for RFD, as Dominator gyros normally have no more than a little pod.  Boyette and DeGraw had the cabin analyzed using Computational Fluid Dynamics, and discovered that it required only 15 HP at 100 mph. The slick cabin includes large transparencies up front and comes to a perfectly aligned prop spinner in the back. The stub wings that hold the main landing gear have an open slot in the trailing edge, which is used to exhaust cooling air from the engine compartment.

Working together at Boyette's Florida shop for a period of over two years, they completed the unique gyro. It was static-displayed at Bensen Days last year, but in the last two months they have flown it, and jumped it, at Boyette's airstrip. DeGraw flew the first, and has flown most, of the jump takeoffs, but Boyette has also made jump takeoffs.

They trailered the machine to Wauchula and Bensen Days, looking forward for the opportunity to fly it from a long, paved runway in a level, rural area, for its first flights without the safety of an airstrip underneath. Before Bensen Days, LIFINO had not only never flown in public, it had never flown a traffic pattern. If the new machine was unable to complete a circuit at Wauchula, there were no hazards to an emergency landing.

Takeoff procedure, DeGraw says, is fairly straightforward. With collective set on zero degrees, the rotor is rotated to 150% of flight RPM -- meaning, to about 450 RPM. With climb throttle set, the collective is popped to jump setting, which is higher than fight setting. The aircraft then, as advertised, leaps into flight from a standing start; the collective is then gradually milked down to the normal flight setting, where it stays in all normal flight operations.

Unlike a helicopter, there's no need to manage the collective in normal flight, and no need to correct for the torque of a powered rotor -- LFINO has some trim tabs on the center of three rudders, which will be bent appropriately once more flight experience is gained. (DeGraw made a first tentative adjustment before the flight described here).

The collective comes in handy for landing, too. It can be used to cushion a landing, preventing the dreaded gyroplane stop-n-drop syndrome where one runs out of lift a foot or more before one runs out of altitude, resulting in an abrupt, unpleasant arrival. (Some gyros, like Dominators and the Monarch Butterfly, have suspension technology that permits this kind of landing).

LFINO is powered, like so many 2-seat gyroplanes these days, by a water-cooled 2.5 liter 4-cylinder Subaru boxer motor. Cooling air enters two "nostrils" over the nosewheel and is ducted under the cockpit floor to the radiator and oil cooler that are located in the rear of the fuselage. (We'll be coming back to this in a moment).

Like any new technology, LFINO has some quirks, and its builders and operators. DeGraw and Boyette are bedeviled by some teething problems. Most frustrating right now is cooling: the boundary layer attaches to the nose of the craft and creates a sort of surface tension, preventing cool air from entering the cooling ducts -- at least, that seems to hold up as a theoretical construct, explaining why the craft can't fly more than a couple of traffic patterns without having to land and shut down to prevent overtemps.

They can't go willy-nilly moving the radiators around, because LFINO already is CG-sensitive. A 35-lb. block of lead is screwed to the frame forward of the rudder pedals, when DeGraw or Boyette flies the plane solo. DeGraw knows that they could get the cooling air they need by simply constructing a protruding air scoop, but such a crude approach offends both his aesthetic sense and his engineer's preference for the elegant, understated solution. So LFINO will probably undergo some more alterations before it achieves its designers' hopes of 120-knot speeds.

Why do so much work on a gyroplane that it's practically a helicopter? DeGraw admits that the rotor system and controls have everything necessary to be a helicopter main rotor system. But there's no need for an anti-torque system (typically, on helicopters, a tail rotor or counterrotating second main rotor) because the rotor system is primarily powered by autorotation. LFINO may be complicated and heavy for a gyroplane, but gyroplanes are a simple sort of aircraft, and it's much simpler and lighter (1050 lb empty) than a typical light helicopter. A jump-capable, true VTOL gyro has the potential to do helicopter missions that don't require hovering or external load capability. And a gyroplane has the potential to be much more efficient for cross-country flight than a helicopter.

Today we have a chance to see it do its thing one last time here, before Dick and Ernie break it down and prepare to trailer it back to the workshop at RFD.

"Are you going to fly it again?" Boyette asks.  He's decided it's time to break down the display, pack up, and go, and having made the plan he's antsy to set it in operation.

"I just preflighted it," DeGraw says by way of reply, stroking his chin and looking at the machine. Boyette nods agreement. Soon DeGraw is strapped in. So far, it's nothing special. "Clear!" The engine starts up, and all around, people start to perk up... those who haven't seen the ship jump head for the flight line. Those who have, run to their cars or tents to get their cameras. In no time at all DeGraw was the machine on the numbers for Runway 18. Boyette is close alongside on a motorscooter, airband radio in hand.

The engine winds up, and the rotor spins faster... and faster... and faster. Then, so quickly that you'd miss it if you glanced away or blinked momentarily, the gyro sprang some twenty-five or so feet into the air and flew forward. DeGraw made a circuit with a low pass in lieu of landing, and then came around the pattern again... this time he set it down in a near-vertical touchdown, using collective helicopter-style to cushion his landing.

LFINO has flown in public; it has been doing so all week, but still, when gyroplane-savvy onlookers see it, they feel like applauding. Some of them do. DeGraw taxis in and shuts down, conferring with Boyette about the cooling problem.

The first goal for LFINO -- demonstrating jump takeoff and vertical landing -- is met.

What's next?

"Oh, who knows?" says DeGraw, with that gradual grin. He'll think of something. Or Boyette will. And if they don't individually, the two of them together definitely will.

What will they think of next time? Whatever you say to that, it won't be LFINO. They already thought of that.

FMI: www.rotorflightdynamicsinc.com/lfino.html

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