Well, during the past two years, I have done much pondering regarding designing a homebuilt PBY. The original idea I had for the PBY was to have two versions, an 58% and a 49% scale. The plan was and still is to build a refined composite version of a PBY-6A on a homebuilders scale. That still holds true, but I've definitely narrowed down the scale of the aircraft (roughly 50%). I have decided to officially name the plane the "PBY-7A Super Catalina" (or "Super Cat"). I named it PBY because it will most definitely resemble the classic Consolidated model 28. The -7A represents an evolution of the design from the earlier versions (in this case a dramatic evolution, in technology, materials, and scale). The name "Super Catalina" came from when Catalinas had 1200hp Pratt & Whitney R-1830-92 engines replaced with 1700hp Wright R-2600 engines from a B-25, the turret nose replaced with a sleeker "yacht" nose, and the rounded rudder replaced with a larger, angular rudder with an aerodynamic balance. With these improvements, you no longer had an average "Cat", but a "Super Cat".

---

My original intro paragraph was:

        I originally wanted to use radial engines and preferred a diesel, with the Zoche diesel radial being the proverbial best of both worlds. Time has shown the Zoche powerplant is not likely to be in any homebuilt aircraft even outside the near future. The M-14P radial was considered because it was around the right size and a radial. But for the prototype design, it has shown itself not to be practical for the average homebuilder (2 x 20gph...). Worse yet, a pair of P&W R-985's (2 x 28gph... ouch).

---

        I am working on a "Conceptual Design", basically getting the details of what I want (and why), how it's going to look, and how am I going to get there. After this stage will be the "Preliminary Design" where real numbers are crunched, sizing of parts, calculating stresses, aerodynamic issues, stability, etc. Basically analyzing and optimizing. After that stage is done, a "Detailed Design" is specified with all the parameters for the prototype. Then a "Manufacturing Plan" is made for how to build it. Last is a "Testing Plan" for testing the prototype on the ground and eventually, in the air. Hopefully I can begin on a preliminary design in the next couple years. I'd like to start building within the next 15-20 years, and fly before the 100th anniversary of the first flight of the Consolidated Model 28 (First flight of the XP3Y-1, 28 March 1935).

---

        Other high performance amphibious aircraft have high fuel burn, high cost, and a design which is not inherently utilitarian (Seawind, Seastar). Existing certified amphibious are either small (lake amphibs), too few and too old (Widgeons, Gooses, SeaBees, etc). Others are float equipped landplanes, which generally are slower and have less useful load because of the weight of the floats. The PBY has always been a workhorse, and this scale version will continue to be one. The Super Cat is intended for a wide range of uses, and a wide range of owners/operators.

Item	Ultimate Goal	Minimum Goal
Useful Load, LBS	2200	2000
Stall w/Flaps, KTS	40	49
Cruise @ 75%, KTS	174	145
Climb Rate, FPM	1750	1400
Takeoff, Land, Ft	500	750
Takeoff, Water, Ft	625	950
Range, Nautical Miles	2000	1500

        Where does the Super Cat pilot want to fly? Well, they want to be able to operate from paved runways and from water. Considering the utility of the aircraft the Super Cat pilot might want to fly from short, rough fields, necessitating rugged landing gear and STOL performance. They fly in mountainous terrain with high altitude capability to clear mountains and weather. They might even want provisions for skis to be installed on the gear. It’s the perfect bush plane. It’s also the perfect recreational aircraft for flying to the middle of nowhere to fish or hunt with your buddies and a load of stuff. Or perhaps you have a jimmy buffet CD, and are lounging in the Southern Pacific or the Caribbean. In that case you want saltwater capability, long range, and a plane that is an air yacht, something you can eat and sleep in. The Super Cat pilot might be running a business and needs to operate in IFR conditions. Everybody likes low operating costs, the cheaper to operate the more people the Super Cat will appeal to...

        What does the Super Cat pilot want to carry? If you’re a bush pilot you need to load/unload in the field, carry 55 gal drums of liquid, supplies, hunting/fishing gear, lumber, 4x8 sheets of plywood, or just about anything. The recreational pilot might want to carry 3 people at long range, flying to the south pacific, or 5 people plus a bunch of stuff on a 500 mile hop, or maybe you are taking 6 friends on a ride to the lake.

        Where will the Super Cat pilot store their plane? Well, it could be tied to a dock, or a tree… It could be tied down at the airport, or in a large standard T-hangar that a king air might fit in.

        Where will the Super Cat be assembled? It could be in a large hangar with a 59’ wide door. It could be your garage for the first stages. It could be in a temporary structure on the side of your house.

        How often will the Super Cat be used? Most homebuilts are used less than 50 hours per year. The Super Cat ideally is for anyone slightly more active than average, in the 50 to 100 hour per year range. The Super Cat owner might put many hours on during a handful of long trips. Or the owner might be using it as a bush plane, putting on 365+ hours per year.

---

        Size : There are a lot of homebuilt single engine amphibs out there around 80-200hp, so I'm not going to design something that basically already exists. For what I want, these aircraft are not big enough to do. I am looking to build something where there is nothing very similar to it. It would be similar size to a Grumman Widgeon. But, how many of those do you see around? Very few. There are few twin engine homebuilts. There are some twin engine certified of similar size, and fewer with the utility of a half scale PBY.

    Operating costs : I'd like to see a C185 on floats or Beaver on floats owner consider buying a Super Cat with a pair of 200 hp Deltahawk diesels. In comparison to a Cessna 185, the fuel burn would be similar but you would have about 800-900lbs more useful load. In comparison to a Beaver, you would have slightly more useful load, but the fuel burn would be 60% of that big Pratt radial.

    Power : Power loading at the bottom end, 2 x 180hp , would be similar to a Cessna 210N or a Piper Malibu (~12.9 lb/hp). Go up to 2 x 200 hp, and you have power loading similar to an Grumman Widgeon, Piper Seneca, Express 2000FT or Cessna 185  (~11.6 lb/hp). And if you have a need for speed, 2 x 230 hp will get you power loading similar to a Lancair IV, Beech Baron, or Cessna 310 (~10.1 lb/hp).

    Performance : Despite the lower power loading compared to most twins, the PBY should do well under single engine operation because: 1) There is plenty of wing area, resulting in a low stall speed. 2) using laminar surfaces, the plane will be lower drag. 3) With the engines close together, you can power the remaining engine to 100% power. 4) Using 3-blade constant speed props that feather, the engine out will not drag the plane down, and the remaining engine can produce the low speed thrust that it needs to continue a climb out.
   
I'm shooting for an end product that is easy to build (although considering the size, not necessarily quick to build), and provides good performance and utility. Likely it will start out plansbuilt then have some parts available, leaving no one hanging if the worst happened (bankruptcy). If demand goes crazy, a kit might materialize.

---

Fuselage Geometry

            The PBY is not the sleekest airframe. The wing struts are a necessary evil. The whole fuse can be shaped using laminar profiles. The hull should be primarily designed to reduce air drag while improving water performance and rough sea capability. The rear blisters can be made to protrude less and shaped to be lower drag (longer). The front turret I’m sure is draggy and I wonder how much speed is gained on the aircraft with the yacht front end (no turret).

Hull Design

            Creelman did a wonderful job designing the float hulls for the Aerocat. He uses "blended-step/fluted-vee" catamaran hulls. A similar hull design could be incorporated on the Super Cat.

Landing Gear Configuration

        The main gear would be similar to the original. The nose gear would be a new design that eliminates the gear doors low on the nose of the hull.

Propulsion Configuration and Selection

        The original PBY was powered by a pratt and whitney R-1830 two-row 14 cylinder radial engine (44.125” dia) producing 1200 hp in later versions. These are mounted on the wing above the fuse in a tractor configuration. However, some aircraft had been retrofitted with Wright R-2600 (54.26” diameter) two-row 14 cylinder radial with 1700 hp radial engines like those from a B-25 Mitchell.

        I would hope that the plane could remain radial engine powered, but the choice of radials is limited. The sound of a radial engine plane is beautiful. I would only want it piston powered, preferably a diesel so it can run on Jet A and be more efficient. I’m sure some moron would want to put a turbine engine on it. Ick. Jets are for kids… A version using the Russian M-14P radial would be an interesting prospect since they are cheap and reliable (think of some guys in the middle of Siberia wrenching on these). But, a PBY that is sized to use two 365hp radials is about 60% scale grossing 8000 + lbs. That size of plane will have two engines sucking down 18+ gph at cruise each, 36+ gph total. Definitely not cheap…

        By far the most numerous HP range as far as engine options is the 180hp to 230hp range. Most kitplanes are based on using either a Lycoming O-360 or IO-360 (180 or 200 hp). Larger faster kitplanes use 300 or 350 hp versions of the Continental O-520 or O-550 or Lycoming O-540. These larger kitplanes have 75% cruise fuel burn in the 15-20 gph range. These are planes like the Seawind, Lancair IV and Glasair III. Kitplanes that use 200hp O-360’s have cruse fuel burn in the 10 gph range.

        The powerplant showing the greatest potential for an efficient Super Cat is the Deltahawk Diesel. It is sized like and weighs about the same as an IO-360 Lycoming. The fuel consumption is lower, it uses Jet-A or diesel (usually cheaper than 100LL), and retains near 100% output at 10,000 ft altitude. It is also cheaper to buy, rebuild, and maintain than a new IO-360. A pair of 200 hp Deltahawk Diesels would use about 16 gph at 75%, similar to a single 300 hp IO-540. In that respect, the Super Cat would cost no more to operate than a 300hp single engine airplane.

Wing Configuration and airfoil

            For the wing, the original planform shape will be mimicked and the attachment to the fuselage and the retractable wing tip floats. That’s it. Something near or slightly higher than the original aspect ratio will be maintained (about 7.7). At that AR, there is a good balance of efficiency and weight. If I can reduce wing area without going above my stall speed goal, I may reduce the wing area. The old Naca 21 airfoil, increased in thickness 20% at the root and reduced 20% at the tip (9.61 to 14.35% thick, avg 12.01%) is a somewhat draggy airfoil that produces a good CL (1.6).

            The airfoil that I will compare other airfoil choices to is the NACA 65-415. This is a laminar flow airfoil of 15% thickness, The CL is 1.55-1.6 w/o flaps and with 20% split flaps, CL 2.5.  So, considering some of the wing will not have flaps, we should be able to get achieve an average CL of 2.6 with 30% chord fowler flaps. The main reason for selecting the 65-415 airfoil is the broad drag bucket. The drag bucket gets down to .004 and spans from 0 to 0.8 CL. Polar plots seem to show a standard stall, nothing too sharp. The broad drag bucket allows the aircraft to fly efficiently at a wide range of speeds and payloads. Despite the fact that this airfoil is 15% thick, it has a broader drag bucket than many airfoils. Some airfoils have slightly lower drag buckets, but the buckets are narrower. Data comes from wind tunnel data from Univ. of Tenn.

The wing, and the plane, is sized to fit in a standard 48’ wide hangar with a 47.5' door. Basically if a light twin with tip tanks, or Beaver can fit in, the Super Cat can fit…

Other airfoils under consideration: 747A315, 66-415, GA37-315

Tail Configuration

A similar setup to the PBY-6A and PBN will be mimicked. The H-stab might be fully cantilever. It will be sized to provide control authority minimum 5% below stall speed.

Anticipated Design Specs

Scale	Span	Length	Gross	Useful	Engines	Pow Load	75% Fuel Burn	Fuel Cap	Wing Area	Wing Load
%	Ft	Ft	Lbs	Lbs	HP	lbs/hp	GPH, Jet-A  (Lyc equiv., O-320, O-360, IO-360, O-540)	Gal	Sq. Ft	Lbs/Sq. Ft
100%	104	64.8	35,000-38,000	14500	1200-1700	10.5-15	a lot, R-2600's use over 150 gph	1750	1400	26-27
44%	46	31	4650	~2000	180	12.9	~14.5 (20.8)	160 std, 245 opt	240-260	18-19.9
44%	46	31	4650	~2000	200	11.625	~16.1 (23.1)	160 std, 245 opt	240-260	18-19.9
44%	46	31	4650	~2000	230	10.1	Renaut-SMA 230hp, ~18.6gph, (26.5 gph)	160 std, 245 opt	240-260	18-19.9