Thunder Mustang               

    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

    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

    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 for more information. Dan
    Denny started Precision Aircraft to assemble Thunder Mustangs for
    customers all over the world.

    Contact Dan at
Thunder Mustang