Kelly-D

The Kelly-D is an American homebuilt aircraft that was designed by Dudley R. Kelly of Versailles, Kentucky, in 1981.  The aircraft supplied in the form of plans for amateur construction.

The Kelly-D is a development of the Hatz CB-1, but with more wingspan and fuselage length, and with more cockpit space for larger pilots. It features a strut-braced biplane layout, two seats in separate tandem open cockpits with individual windshields, fixed conventional landing gear and a single engine in tractor configuration.

The aircraft is made from a combination of 4130 steel tubing and wood, with all surfaces covered in doped aircraft fabric. Its 26.30 ft (8.0 m) span wing is made with a spruce structure and has a wing area of 230.00 sq ft (21.368 m²). The wings are detachable for ground transportation and storage. The standard engine used is the 115 hp (86 kW) Lycoming O-235 four stroke powerplant.

The Kelly-D has a typical empty weight of 925 lb (420 kg) and a gross weight of 1,500 lb (680 kg), giving a useful load of 575 lb (261 kg). With full fuel of 24 U.S. gallons (91 L; 20 imp gal) the payload for pilot, passenger and baggage is 431 lb (195 kg).

The designer estimated the construction time from the supplied kit as 4000 hours.

In January 2014, 13 examples were registered in the United States with the Federal Aviation Administration, although a total of 16 had been registered at one time. Also in 2014 there was one registered with Transport Canada.

• Crew: one
• Capacity: one passenger
• Length: 19 ft 3 in (5.87 m)
• Wingspan: 26 ft 4 in (8.03 m)
• Wing area: 230.0 sq ft (21.37 m²)
• Empty weight: 925 lb (420 kg)
• Gross weight: 1,500 lb (680 kg)
• Fuel capacity: 24 U.S. gallons (91 L; 20 imp gal)
• Powerplant: 1 × Lycoming O-235 four cylinder, air-cooled, four stroke aircraft engine, 115 hp (86 kW)
• Propellers: 2-bladed fixed pitch
• Maximum speed: 100 mph (160 km/h, 87 kn)
• Cruise speed: 90 mph (140 km/h, 78 kn)
• Stall speed: 40 mph (64 km/h, 35 kn)
• Range: 275 mi (443 km, 239 nmi)
• Rate of climb: 825 ft/min (4.19 m/s)
• Wing loading: 6.5 lb/sq ft (32 kg/m²)

Aloft in the Kelly “D”
By Bob Livingston
One of the many rewards that have come to me in my flying career has been the special privilege of counting Dudley Kelly as a personal friend. Here is a unique man, in my opinion, to whom some attention should be given by a writer more skilled then I am, for surely in his life there must lie treasures of experience untold and the aviation world should know them. I have known him and some of his handiwork for more than twenty years now and still feel I have only glimpsed the measure of his skills at design and creative thought. With the utmost pleasure I was privileged to watch his latest product evolve from a stack of raw metal and assorted materials to finished flying machine. And it was my extra reward to assist in the flight tests of this new design, exploring the unknowns of performance. The purpose of this writing is to share those experiences as best I can.
The master craftsman, Jim Foster, who built the Kelly “D” was the first to fly the plane, properly so. And after making some adjustments to the engine and riggings of the wings, he placed the plane in my hands for extensive testing. With the deepest appreciation for his trust in my abilities I set to work.
I flew the Kelly “D” a number of times during June and July of 1982, operating from first a 2,200 foot grass runway, then a 1,600 foot packed dirt runway. All flights were full stop, with intent to bring the airplane to a halt as quickly as possible without skidding the tires or causing the tail to get light. My theme was to deliberately look for bad characteristics of flight behavior and any other condition that would cause alarm to a new pilot. Once I was accustomed to the feel of the plane, I deliberately mismanaged the controls often to uncover any hidden traits. To sum up, I did just about everything I could do to discover flaws.
In relating what I found I will deal in certain categories:
Physical Comfort
I am 6’3” in height and weigh 240 and I was frankly surprised at how comfortable I could be in this plane. Granted, everyone who builds this plane will tailor it to his own dimensions, but I can assure those larger people who might be interested in this bird that they can indeed find happiness in the rear cockpit of the plane. However, that would not be true for the front hole, so beware.
Now, the reader should not be misled. Certainly, I could not have stretched out and read the morning newspaper whilst flying. I was definitely snug, but I was not uncomfortable and felt sure I’d have been able to endure a long stretch at the controls and still have been able to walk a straight line unassisted. My shoulders lightly touched both sides of the cockpit rim and my knees were in close proximity to the bottom edge of the instrument panel, but I could still move the controls throughout their full range without banging my body in the process. While my legs have to remain flexed in order to fit all of me in, I could still activate the rudders and brakes without a problem. An average-sized pilot (whatever average is) will find himself very comfortable indeed, I’m sure.
The deep fuselage cutouts and brief windscreen would seem to create airflow problems, but I did not find it to be unhandy at all. One would probably have to do wind tunnel/smoke stream studies to demonstrate any deficiencies. I find no noticeable problems, even in low speed work, stalls of all kinds and aerobatics. Life in this cockpit will be the same as in any other open cockpit plane.
Ground Handling
As I watched the plane being constructed, I saw that the nose would be long and that the spinner would be a long way from the landing gear, two features that have produced handling problems in other aircraft designs. In conversations with Dudley and Jim, they assured independently that they felt it would be all right. Not only was it not a problem, but it proved to enhance stability somehow. The longitudinal balance was a part of the plane’s overall niceness, for the ample length of the fuselage assisted in dealing with crosswinds on taxiing.
Of course the long nose called for “S” turns while moving about on the ground, but just a slight drift of the nose let me actually look under the nose, as well as around. I considered that unique. Never was more than just a tap on the rudder pedal required to get the plane back on taxi centerline.
The plane will ground loop, make no mistake about that. I didn’t explore that, because there were no evident tendencies to do surface 360s any more than any other taildragger biplane. However, here again I think the long-legged design carries the lower wing panels higher than other similar two-wingers and this would tend to keep the wingtips from dragging the ground as she whirls around, which would amount to a very good feature indeed.
Low and high speed taxi runs were accomplished with no hidden nasty traits that one would not find in any other plane.
Climb Out
After takeoff, airspeeds reaching from 55 MPH to 75 MPH were flown, seeking a comfortable speed/nose angle combination. At the lower speeds the nose blocked out the whole world straight ahead and I settled on 65 as the airspeed I liked best for climb. To me, it seemed that produced just about the same nose up angle as the plane had sitting on the ground in the three-point configuration.
Otherwise, climb out control input needs and pilot axioms would be identical to other biplane types.
Cruise
Obviously, cruise speeds will vary according to powerplant the builder chooses. The Lycoming O-290 of the prototype propelled us along at a handy 97 MPH at a reasonable thrust setting.
The design certainly seems to promote facile trim adjustments and by the time Jim let me play with his new toy, he had worked out all the wrinkles. So I found I could zoom along in almost a no-hands condition while tooling about in cruise.
Stalls
As I further watched the plane aborning, I wondered about the rudder. Would it be enough to handle the yawing forces? What would be its effectiveness in a spin entry/recovery? There was no question it was in graceful proportion to the rest of the fuselage shape and flow, but would it do its job completely? The answer is: It did exactly what it was designed to do. In an aggravated slow-flight configuration, where all controls were “stirred” at the nibbling edge of a power-on stall, just normal foot pressures on the rudder pedals kept the wings level and stopped incipient wing drops to spin entry. In one series of stalls I approximated the old “falling leaf” maneuver wherein the rudder goes rapidly from stop-to-stop as the plane flutters downward in a near stall configuration. The rudder did its job.
A complete series of stalls power on/off, straight ahead and turning, acceleration, over-the-top and tucking under were done. I had a ball doing them all. And by golly, I think the plane did too.
Spins
It will to the left. It won’t to the right.
Usual power off spins were done to the left, bringing the nose up to about three-point attitude and holding it there until the stall break, then applying full left rudder with stick centered, but full aft. When the spin was established, release of back pressure to neutral setting with just a touch of opposite rudder brought in a quarter turn recovery.
To the right it would only “wrap-up” in a spiral with a quick loss of altitude and resulting buildup of adverse forces. So don’t try to spin to the right!
Otherwise it spins like any other airplane, by and large.
Aerobatics
First, I want to stress this: The Kelly “D” is not a plane that is specifically meant to do aerobatics, per se. However, it will do a pleasing variety of maneuvers that will make your heart beat fast. And, it should comfort the person laboring to construct his own Kelly “D” to know that if he gets a little ham-handed as he gets used to flying it, it will not fly apart if he pulls a G or two.
I am a firm proponent of low-stress aerobatics when flying in a non-competing capacity. I believe that nearly all airplanes are able to do loops and rolls when speeds and loads are kept within proper flight envelopes, as established by the manufacturer. I’m persuaded many pilots and their passengers have suffered because of a lack of understanding and experience in aerobatics. I wish that basic flight training would demand exposure to at least loops and rolls, so that effective recoveries could be made from unusual attitudes following vortex encounters and other un-stabilizing flight conditions. And it was low-stress aerobatics that I employed in flying the Kelly “D”.
In performing the loops and rolls, I flew those maneuvers so that smooth contours were pursued; with accompanying stick loads of the lowest magnitude possible. In other words, there were no “slam-bang” control forces applied and no rapid reversals of G loads as the maneuvers were flown. At all times I pursued my longstanding rule of; if I feel good, so does the plane!
Loop
From level flight at cruise power setting, I lowered the nose to 20% above cruise speed (to about 120 MPH) and smoothly brought the nose up into the loop entry. Smooth but increasing back pressure was applied in a manner so that at the top, when the bird was exactly on her back, the stick would be almost full aft. Across the top, a glance at the airspeed usually showed about 65 to 70 MPH. Stick position was maintained. At this point I found that a touch of right rudder was called for to maintain a straight line in relation to the center of the “box” in which I was doing the maneuver. As the plane descended on the last half of the loop I then began to move the stick forward in recovery. Now I got interested in the reading on the G meter and began looking to pull a steady plus 2 G as I rounded out the bottom of the loop. Power was cut as necessary to help reduce the load and prevent over speeding of the engine. Recovery was then made to level flight.
The Kelly “D” will do a beautiful round loop when done like this.
Rolls
Aileron rolls were begun from a shallow dive to about 130 MPH, at which point the nose would be brought smoothly up to 30 degrees above the horizon, where the stick would be neutralized for a second, then applied fully to the left.
NOTE: I recommend neutralizing the ailerons and stick here so that as the roll is done, there are no positive or negative forces inadvertently applied during the maneuver, which requires none of that.
The plane will roll on around with no additional control inputs, except for a very small dash of rudder, as required, to control yaw.
If all has gone well you should be back to about 95 MPH or so. In fact, on several occasions I just went on ahead and did a second one because it still felt good. But go carefully there my friend.
Aileron rolls both left and right went very well.
Hesitation Rolls
Point rolls were done with an entry speed of 140, then up to the same 30 degrees above horizon procedure, and then standard control applications followed to accomplish the maneuver. Only four-point rolls were done to the left (I’m a lousy roller to the right!).
Snap Rolls
If someone feels they really must snap their plane (I would first energetically urge them to forget the notion), then at least I would not want to bear the responsibility of not having told them at least something about the maneuver. So, if you must snap it, then please do so at the lowest speed possible. Say, no more than 65 at the most! That way there is very little chance of overstress of the airframe. The plane will whip around nicely at that speed. You will find the recovery to be a little sloppy, but with the capabilities.
I suggest all snap rolls be done power-off.
Stability
I found the airplane to be quite stable around all three axes, at all airspeeds flown throughout the testing phases. If the nose was raised to 45 degrees angle from straight cruise flight and the stick released, the plane would stabilize itself after four oscillations, generally.
Flutter
Standard procedures were used in attempts to include control surface flutter but, as was suspected early on, there was never a hint of surface tremble in the attempts made.
High Speed Dives
The airplane was taken to 160 MPH on four occasions, with pullouts at 4 Gs and rapid return to the altitude from which the maneuver was begun. During the pullouts I watched the wings for signs of fabric ripple and the flying wires for excessive vibration and there was none evident.
There was some initial concern about the strength of the windscreens mounting but there was no adverse bending at high speeds.
Comparisons
The feel of the controls in flight are very much like those of a Stearman. Light, balanced and pleasantly responsive.
On the ground the plane feels like a Cub. The landing gear is mostly stiff-legged but has resiliency when needed. The plane has a very firm, no-nonsense feel as you taxi around.
The thin, flat-sided fuselage afforded a measure of visibility not usually found in homebuilt biplanes. I enjoyed that very much.
Transitioning
Pilots with prior open cockpit biplane experience will be able to get in, fly away to their heart’s content and smile all day.
Pilots with average experience, but no biplane or open cockpit time should get some of that kind of dual prior to flying the plane. After seven or eight takeoffs and landings and some stall practice under the guidance of a qualified instructor, switching to the Kelly “D” solo should be uneventful.
Miscellaneous
The reader should be cautioned that I flew the plane solo at less than gross weight. It will be a different plane at gross weight.
The front seat passenger might appreciate some protection from the wind. Perhaps some fold down doors might be considered. Then too, that might facilitate closing off of the front hole when flying solo.
Cold weather builders should be able to easily dope out canopies. Maybe Dudley could be persuaded to design a modification for that.
Safety
The Kelly “D” is an easy plane to build and to fly. But don’t be beguiled by the “at-home” feel you will experience. You’ll still be very much subject to all the hazards inherent to flight. Take care.
I hope many people will have as much fun with the Kelly “D” as I did. It is a superb design.