You may never get beyond admiring a Thunder Mustang from a distance. On the other hand, if you can deal with the energy of high performance, if you can appreciate the incredible level of engineering and exact scale detail, if you can cover the investment, you my be qualified to own and fly the most powerful, aesthetically dynamic kit aircraft in the world. ---


The original Papa-51 'Thunder Mustang' sales brochure.

--- The extraordinary Thunder Mustang offers its owner a unique blend of speed, maneuverability, and mystique. Given the power to weight ration, it outperforms a P-51 at a fraction of the cost. The Falconer V-12 engine delivers the torque and the sound that turn low passes into strafing runs. From the time you're pushed back in the seat by advancing the throttle for takeoff, until you chop the power for landing, every flight is a form of high adventure, a rush, a journey into the twilight zone, a flight through rainbows in a clear sky...

Thunder Mustang kits are complete, containing everything from the spinner, prop and engine to the tailwheel, less your choice of avionics, paint, and upholstery. Each piece of the aircraft reflects a professionalism in craftsmanship and technical achievement that sets a new standard for excellence. parts fit perfectly. Extensive prefabrication minimizes construction time and eliminates hassles. The complete us of carbon fiber in the structure produces incredible strength and light weight. ---


Here is a magnificent view of the front office. It fits like a glove, with everthing right at your fingertips.

--- If the challenge and excitement of owning the world's fastest and most powerful kitplane appeals to you, contact the Papa 51 Ltd. Co. for the complete story on the Thunder Mustang...

First Impressions

Papa 51 Ltd., Co. is proud to welcome Dale M. Clarke to its family. Dale's extensive background in business, marketing and sales will enhance Papa 51's ability to serve the Thunder Mustang enthusiasts. As an additional plus, Dale's background in aviation promotes him to demonstration pilot status in the Thunder Mustang.

Flying Warbirds has been Dale's passion and much of his general aviation history. Now he is flying a kit built replica that will outperform many of the classics that he has personal experience in. Dale has flown nearly 75 different types of aircraft, from the standard certified spam-cans, to experimental aircraft and numerous Warbirds. His list includes: the P-51D Mustang, F4U Corsair, Fiat G-59, T-28, T-6, T-34, Sea Fury (T-MK11 & T-MK20), Commonwealth Boomerang, SF-260 Sia Marchetti, Antanov AN-2 "Colt", Boeing Steerman, NA-50 and Yak-3.



He holds an unlimited LOA for any high performance, single engine, piston powered airplane and has raced Unlimited's at Reno. He flew his first Reno Air Race in 1984 in a Sea Fury. Dale has flown aerobatics in everything from a Luscombe to a Sea Fury. This experience will come in handy in demonstrating the Thunder Mustang in the coming years.
Dale comes to us from Washington state, where he had been Vice President of Sales and Marketing and demonstration pilot for Stoddard -Hamilton Aircraft Inc. As you will read below, Dale gives us his impressions and experiences with the Thunder Mustang. Way too much fun.



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Warbird pilot Dale Clarke gives his initial impressions of the Thunder Mustang

My first impression of the Thunder Mustang as it sits on the ramp, is that it looks like it is going 300 mph and nobody has even started the engine.

My flight begins with a walkaround inspection, noticing everything is like the P51D's that I'm used to, only just a little nicer somehow. Today, I feel just a little taller. Maybe I'm swollen with pride because I'm the new guy that gets to strap on this magnificent machine and roar off to beat the air into submission. Regardless, the preflight is straightforward and normal except I'm not looking for evidence of loose rivets.

With the walkaround complete, I ease down into the cockpit and grin. It feels like a reunion. It's all P-51. The instrument panel is right, the canopy jettison handle is where it should be, the throttle quadrant is positioned perfectly, except that it is missing the mixture control lever. That's nice, one less thing to worry about. Rudder pedals adjust like the North American brand and there is so much leg room I can't reach them. Even after moving them back towards me to get full travel, there is still lots of leg room. The cockpit is comfortable. I'm not going to flop around in it, but it's very comfortable. It feels larger than a Yak-3 and a little cozier than a Sea Fury.

The engine start makes a pilot look like he really knows what he's doing. Turn the key on, put the ECU (Electronic Control Unit) switches to "main" and "both", turn the boost pump on and press the start button. About three blades and those 12 short stacks all begin to sing in unison. No primer to worry about, no mixture to worry about, no stack fires, no popping or banging, just the rhythmic bark of the big V-12. The prop didn't even need to be pulled through. I like this.

Just like the original, push the stick forward to unlock the tail wheel and turn to taxi toward the runway. The visibility is outstanding, so good I'm tempted to ignore 'S' turning, but in the three point attitude, there is a blind spot over that long thin nose so I defer to safety and slowly weave right and left to clear the path in front of me.

The temperatures are up to normal. This takes a little while on a cool day because the gearbox has to be warm before a run-up. I go through the check list; brakes locked, hold the stick back, bring the engine up to 3000 rpm, cycle the prop, that's all normal. Now, I've been told about these ECU units and I know how to manipulate the switches, but I'm still a little baffled by this computer wizardry. Shut down ECU #1 and the RPM's drop to 2250 (it is amazing how the engine runs so smoothly on six cylinders) back to both and we're again at 3000 rpm. Shut down ECU #2 and again the engine is running smoothly at 2240/50 rpm. I'm told that in an emergency, the engine will get you home on six cylinders. As smooth as it is on run-up, I'm starting to believe it.

I can hardly wait to get cleared onto the runway, I want to get the Thunder Mustang into the air and go somewhere......fast. My right foot is ready as I push the throttle forward, straight to the stop. The mustang leaps like a sprinter out of the chalks but the hard left turn that I had anticipated is not there. Oh, you have to feed in a little right rudder, but that's all it takes to run straight down the center line. Just like an original, torque compresses the left strut so I apply right aileron. The tail comes up very quickly and the Thunder Mustang lifts off at about 100 mph.

Keeping the speed within limits while I retract the gear, the VSI reads well over 5,500 fpm and my climb angle is over 45 degrees. I love 'm, but no original P-51 ever did that. (On subsequent flights, I've used a shallower climb angle.) The Thunder Mustang rockets through 150 towards 200 mph and I'm still in the runway environment. This is more like a drag racer. I can't wait to find one of my old friends in a stock P-51.

Cruising along at 10,500 feet, 21 inches of mp and 3900 rpm, it's so smooth you would think you were behind a turbine. I almost don't believe my eyes, the GPS is reading nearly 300 kts, my fuel flow is 21/22 gph. Oh baby, you and I are going to go places. In level flight the visibility is spectacular. Still, I do some clearing turns so that I can start to play a little.

At 30 , 60 and 90 degree banks, the stick and rudder forces are light and will balanced. As the airplane G's up, it feels solid and more massive than its 23'8" wing span. It feels like a fighter. Stalls clean and dirty, power on and power off are all straight forward. There is very little pre-stall buffet, then a crisp break. Simply unload, the air reattaches and you fly away. There is no tendency for the airplane to try to jump over on its back. The airplane will actually do a series of stalls with no problem, unattach, reattach, unattach, reattach, and on and on.

Gentleman aerobatics, loops, rolls, Cuban 8's etc. are performed from level cruise flight. 4g loops result in arcs of thousands of feet. I'm amazed at the roll rate. It's better than 300 degrees per second. This Thunder Mustang is not only fast but it's a delight to throw around the sky.

Dan Denney was up in his Glasair III watching these antics. This is so much fun that I decide to go down and terrorize him a little. After warning him that I'm coming he firewalls it, but there is just not enough. The Thunder Mustang is on him in a flash. So fast that after I make a pass at him I do 360's around him, then a couple barrel rolls over him, followed by coming from below and doing five climbing aileron rolls up past his nose as I leave him behind. I tell Dan there are only two kinds of airplanes, fighters and targets. He tells me he doesn't like being a target. Whoops, I better treat the boss a little better if I want to keep my ride.

We head home as a flight of two, with Dan in the Glasair III and me in the Thunder Mustang. This gives us a chance to compare performance. Dan's airplane is quick, truing 235 to 240 kts, but not quick enough for my ride. As we cruise together Dan has the Glasair firewalled, he's burning 16 gph, I have to pull the Thunder Mustang way back. I'm showing 235 kts and 13 gph to keep from over running him. The mustang is so stable in formation I can take both hands from the controls and wiggle my fingers at Dan.

This thoroughbred wasn't meant to limp around at 235 kts. I roll off my station, bring the power up a little and let the nose point down hill. The Thunder Mustang is quickly approaching 400 kts, as I realize I've got one hand on the throttle quadrant and one hand on the stick. The control forces are still very nice, tighter, but very nice. If I were in an original P-51 the ailerons would be so stiff now I would be grabbing the stick with both hands.


As I near the airport I ask for the overhead approach. In the break I reduce the power and put out 10 degrees of flaps to help get rid of the speed. Gear down, put out the rest of the flaps, boost pump on, prop up and we're base to final at about 110 Kts. I never lose sight of the runway, the picture over the nose is terrific. It's 90 Kts over the fence and the speed bleeds off as I round out. The "spool up" of the large main wheels stakes me nicely to the runway. The Thunder Mustang tracks right down the center line and needs very little rudder correction as the tail comes down.

Taxi back to Papa 51, turn the ECU's off (remember, there is no mixture lever) and the music of the V-12 stops. Unwilling to climb out, I sit in the cockpit savoring this experience. The grin I started with when I left is still plastered across my face. My next opportunity to fly the Thunder Mustang can't get here soon enough.

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A look at what it takes to handle the Thunder Mustang
By Dale M. Clarke

One of the questions that we are often asked about the Thunder Mustang is "what do I need to do to prepare myself to fly this airplane?". It's a fair question and one I frequently answer almost without thinking, "it's very straight forward, you won't have any problem". This isn't a flippant response. Its just that, compared to the other Warbirds, the Thunder Mustang is a treat not only in flight but especially when it comes to ground handling in a high performance taildragger. It is here that I should adjust my perspective.

For most of us who have been flying Cessnas, Pipers, and Beechs, some preparation will be necessary. Anyone with reasonable motor skills, and the ability to follow instruction can be taught to fly a tailwheel airplane, or any airplane for that matter. After all, WWII saw the good ole' U.S. of A. teaching hundreds of thousands of 19 year old kids (my Dad was one of them) to fly the "big iron". Of course, it's a little different here, we're not 19 anymore and we've got a couple hundred thousand of our hard earned dollars invested in this beauty. So, how do we go about getting checked out?



If you don't have a tailwheel endorsement, this is the place to start. Any of the small taildraggers will provide an excellent base for acquiring tailwheel skills. A Champ, Citabria, or Luscombe would be some of the good choices. In truth, the fancy footwork needed to fly one of these is more than you'll need in the Thunder Mustang. After you've mastered the tailwheel airplane, and this really doesn't take long (3 to 5 hours to solo), you'll probably want to fly it for another 10 or 15 hours because its just so darn much fun.
Now it's time to mate your new found tailwheel skills to a higher wing loaded airplane. If you have a buddy with one of those old slow Lancairs or Glasairs (boy have I got some friends that are going to hate me for that!), they will approximate the wing loading of the Thunder Mustang.



The ideal transitional trainer is the venerable T-6. Like all great old warbirds, it's getting harder and harder to find someone that will throw you the keys or even rent you one. Some are available however, and if you can get in one it's worth a lot both in the experience you'll pick up and in the fun you'll have. Still, the Thunder Mustang is a walk in the park compared to the T-6.



Papa 51 Ltd. Co. is just as interested in getting you safely into the air as you are, and as such we've prepared a flight training syllabus that will help you reach that goal. If you have your tailwheel endorsement but haven't been lucky enough to fly the T-6 or any of the other big engine taildraggers, we can arrange transitional training in a Thunder Mustang.

The Thunder Mustang

There is no feeling like raw power. When I worked for Air Ambulance, I loved doing new pilot training in the Lear 20 series. There’s no other civilian plane that will give you that push back in the seat, 6,000 fpm, nose-to-the-sky feeling of a light Lear.
Well, now there is... and it’s called the Thunder Mustang. Mere numbers don’t describe the feeling you get when you push the power up on this plane. Truthfully, it kind of snuck up on me, too. During the first taxi tests and several early flights, the power was brought in slowly. On each subsequent flight, I brought it in a little faster until, finally, I was just letting off the brakes and firewalling it. But it wasn’t until I saw a video of the first public flight that I realized my take-off rolls were about seven seconds and initial climbs at about 40 degree angles.
Where did this plane come from and how did I get to be the lucky one to play with it?

I met Dan Denney several years ago and worked with him on the testing and subsequent redesign of the Kitfox IV Speedster. During this program he showed me a picture of an engine and told me of this next project. I must admit to being a bit skeptical as many had tried to capture the aura of a Mustang, but no one had really succeeded. Years ago I joined a club in California that had a Mustang and a T-6. It was truly a great adventure but the cost and logistics were just too much and I sold my share. Now I’m really lucky as my friend Jerry Gabe lets me fly is rare A-model Mustang.
My doubts about Dan’s plane increased when I got to fly the Stewart Mustang at Oshkosh two years ago. The S-51 was a blast to fly. It felt like a Mustang and even though the performance was not quite as inspiring as the full size airplane, I figured it should fill the needs of those wanting a scale P-51. Fortunately for all of us, Dan pushed on and has created a plane that has a mystique all its own. I’m constantly amazed at the enthusiasm this plane garners wherever it goes. At Oshkosh and Reno the Thunder was displayed next to the Legend, and even though the Legend was flying and the Thunder was just a static display, there was a sense of something special about the Thunder Mustang. Personally, I don’t think that anyone could look at that Falconer V-12 engine installation and not be awed. It just looks right – like an engine truly made to fly.
This is a theme that runs throughout the project: don’t just make it right, make it the best possible. For example, this is the only composite kit I know of that has no wet layups. Because of the use of carbon molds, the parts are so exact you just Hysol them together. Even though the cores are an aluminum honeycomb, which is really state-of-the-art, Dan is now incorporating a process to anodize the core so it could pass the Navy corrosion tests. Now, how much salt the core is going to see sandwiched between carbon skins, I don’t know.

As the date for the first flight approached, Dan and I decided to tow the airplane to Boise International Airport for the first flights. Because we were testing a new engine and a new airframe, we wanted all the advantages of Boise: a longer runway, no city at the end of the runway and advanced crash/fire rescue capabilities. We decided to do the first few flights in Boise with our engineering test personnel before our first pubic flight back at Nampa.
Before the first flight, I was treated to a new experience. Ryan Falconer, who designed the engine, came out to do the last minute tweaking on the installation. I sat in the cockpit while he sat at a table next to the plane with his laptop computer. He would ask me to run at such and such rpm, then he’d look at the timing, fuel flow, etc., and make small changes to the parameters and transmit the changes to the engine. The engine just kept getting smoother and smoother, yet not a wrench or screwdriver was anywhere near it. This engine even has the capability of telemetry where ground observers can see real time what’s happening as I fly by. Ryan says that the unit is also capable of receiving changes in the air from the ground, but because of the consequences of a bad keystroke, we have not tested this feature. We can, however, download the data and phone link it to Ryan and have him modem changes back to us to reload into the onboard computer.

So how does it really fly? Let’s go for a flight and I’ll point out some of the unique things about the Thunder Mustang.
First off, just starting the engine is different. There is no mixture control, no primer, no carb heat or alternate air; just turn on the master and ignition and hit the red button. The computer will determine if it’s a hot start or if you’re at a high altitude airport and akjust the timing and enrichment as required. This engine is really silky smooth. As you taxi out, a slight S-turn is required to clear the area directly in front of the nose. To maneuver in tight areas, just as in the full size Mustang you push the stick forward of neutral and the tail wheel unlocks for full swiveling. In the runup area, set coolant and oil doors, set trims to zero (there isn’t that much torque) and you’re accelerating so fast that the rudder is best just left at “0”), flaps up, bring the power up to 3,000 rpm, cycle the propeller a few times and then turn off the left engine. The Falconer V-12 is built and installed as if it were two six cylinder, inline engines, each with an independent computer for ignition and fuel injection, that just happen to share the same crankshaft. This is an area that makes no sense to me. How can you turn off six cylinders and have the engine still stay smooth as silk? Maybe Ryan can explain it. Anyway, the rpm will drop to 2,200; then return to “Both”; and then turn off the right six and see it also drop to 2,200. Now a final check around the cockpit and we’re ready to go.

Acceleration isn’t really the term to describe the launch of the Thunder Mustang. You fly off at about 90 mph, select gear up and keep pulling back to stay below 150 mph until the inner gear doors close, then stop pulling back and you’re at 175 mph, which is your best rate of climb speed. Several times I’ve pegged the VSI and it goes to 6,000 fpm. That’s 60 miles per hour vertical speed. One oddity of the climb is that you can’t get a steady manifold pressure reading because the Vision Micro Systems, a neat box with all the engine gages in an LCD display, reads to the tenth of an inch and you’re losing five inches every minute in climb and the tenths just keep scrolling by.
As you level off for cruise, usually within three minutes of take-off, the speed builds rapidly and at 65% power at 10,000 feet, the true airspeed is 308 mph burning just 25 gallons per hour. The plane is very stable solo and at full aft CG it is still positively stable but the stick force per G is very slight, so aerobatics with passengers will require a light touch. The other oddity of aft CG is on landing roll. A little more attention is required on the rudders as the directional stability is slightly degraded. Nothing like a Pitts or such, more like a Cessna 180.

The wing on the Thunder has a modified airfoil that allows the speed to build and not have the ailerons get really heavy. Rolls are easy with just one hand, unlike the full size Mustang which gets very heavy on roll above 250 mph. On the other end of the spectrum, slow flight is easy. With liquid cooling you can reduce power without fear of shock cooling and that big prop is a great air brake. Flap speed is 170 mph and the gear speed is 150. The Thunder is a rock and flies the pattern at 120 with great visibility and allows for a wheel landing at about 90. The stalls, both clean and dirty, are non-events and, again, as in the takeoff, you can add power and not worry about torque rolls and such. The one bad facet of this plane is related to that big prop. My first three attempts at a power-off 180 degree approach were unsuccessful and I had to add power to make the runway. Finally, by pretending I’m a helicopter and autorotating at 120, I found I could make a 180 approach from 1,200 feet abeam the numbers. Pulling the prop back to low rpm really helped, but in the event of loss of oil pressure that wouldn’t be an option. I think a couterweighted prop would be an asset as the loss of oil pressure makes the blades move toward high pitch, low rpm.


What do I think it takes to fly this plane and what would you fly to get ready for it? Anyone with some Glassair III or Lancair IV time would be fine. Some tailwheel time also is a must, but except for the T-6 there isn’t a tail wheel airplane that would simulate the handling very well. It’s a system plane and the pilot must monitor temps and adjust coolant and oil doors, etc., but the flying tasks are easy. Dan, who owns a Glasair III, is going to ride with me in a T-6 at Hollister when we bring the plane down for the ground vibration test prior to the high speed flutter tests. After an hour or so of landings, he’ll be the second Thunder Mustang pilot. (Editor’s note: That’s Dan in the rear seat in this months’ cover shot and in the photos accompanying this article. Shortly after this article was written the Thunder Mustang was flown to Camarillo, CA where ground vibration testing was administered by Sandy Friezner, a specialist in this highly esoteric field who is often called upon for his services by the major aerospace firms. Martin Hollmann did the flutter analysis and reported that is was the first instance in which he found no flutter speeds within the range of analysis, which in this case was 0 to 600 knots true airspeed.)


We’re so pleased with the way this plane gets up and goes that we have entered the Aeroshell 3D Speed Dash at Sun ‘n Fun ’97, and we also plan on racing at Reno in the Unlimited Category. I guarantee you’ll be able to pick out the sound of the Thunder from the other planes on the course.
Postscript: It’s been two years since Thunder Mustang closed its doors but there is light at the end of the tunnel. A new group bought the rights to the tooling and the plan is to start producing the kits again. Contact www.thundermustang.com for more information. Dan Denny started Precision Aircraft to assemble Thunder Mustangs for customers all over the world. Contact Dan at www.Precision-Aircraft.net

The Ryan Falconer V-12 Engine

Engine Type Aluminum 90 degree V-12, Ryan Falconer Industries (RFI)

Displacement 601 CID

Horsepower 640 HP @ 4500 RPM

Torque 700+ ft./lb. @ 4000 RPM

Compression Ratio 10.9:1

Bore 4.125 in.

Stroke 3.750 in.

Fuel 100 LL Avgas

Heads Cast aluminum with splayed valve design

Cylinders Steel sleeved

Main bearing size Same as 400 CID Chevrolet "small block"

Rod bearing size Same as 350 CID Chevrolet "small block"

Cam bearings Similar to Chevrolet "small block"

Rods Forged, Carrillo Industries

Pistons Forged aluminum, J.E.

Valve train Dual spring

Valves Stainless, 2.190 intake / 1.610 exhaust

Rocker assembly investment cast stainless steel, 17-4

Roller tappets AC Delco

Pushrods Smith Brothers

Manifold RFI, with end entry plenums and 70mm butterflies

Ignition Delco Direct Fire (no distributor) with dual MOTEC computers
Freeze plugs Threaded with o-ring

Port runners Pre-machined for better flow

Crankshaft Bryant

Timing gears RFI custom

Head gasket Special, Fel-Pro

Dry oil sump pump RFI custom

Damper Fluidampr

Length 55.5 in.

Width 24.25 in.

Weight 980 lb. (firewall forward, includes: accessories, batteries, gear reduction unit, hoses, propeller, etc.)




Gearbox

B.J Schramm headed the project to develop the gearbox for Papa 51. Final design and analysis was done by Mr. Oswald Webb of England (now retired), who worked on the original Merlin engine reduction and was Chief Design Engineer for GKN, the largest gear works in Europe. The unit is designed to endure up to 1500 HP, pulling 13.5 Gs doing 1 second snap rolls for more than 400 hours! We expect some owners to build more horsepower and go racing, and we wanted the gearbox to last. The reduction ratio is 2.8:1. It is a straight cut spur gear arrangement with a quill shaft between crankshaft and drive gear.

Propeller

The 8 foot diameter, constant-speed 4-blade prop is manufactured by MT Propellers. many hours of extensive engineering and consultation was involved in arriving at the optimum design of each component of this system. The gear box ratio of 2.8:1 turns the prop at 1607 RPM for the optimum ratio for the best prop efficiency and high speed with the V-12 turning 4500 RPM. The 100 lb. propeller is of composite construction utilizing a wood core, which is self-dampening and non-fatiguing. This saves weight compared to metal propellers and reduces the gyroscopic effect of the prop on takeoff.

Accessory Section

The accessory drive was developed by Papa 51 and designed so that each of the ribbed serpentine belts will drive the entire five pumps and prop governor should one belt fail. A third belt drives the alternator only. Ryan Falconer Industries is currently (2003) in the final design stage of a supercharger installation for high altitude or higher horsepower applications. It mounts just aft and below the rear of the engine.