February 2013 Issue
Titan 51 Revisited
If a real P-51 Mustang experience is out of reach, this updated replica fighter may satisfy some of that longing.
Ask 100 pilots this question: “If you could fly any airplane, which one would it be?” and the most common answer would almost certainly be the P-51 Mustang. The P-51 is an iconic aircraft with legendary handling, arguably the finest piston fighter of WW-II, and maybe of all time.
John Williams, president of Titan Aircraft, had the same answer to that question. He surmised that he would never be able to buy or fly a real one, so he designed, built and flew a replica to Oshkosh in 2002. Titan started selling kits at that show, and says that 183 kits have been sold and some 67 are flying.
KITPLANESŪ published a flight review in the June 2006 issue that compared it to the real Mustang. We went so far as to photograph both airplanes in formation. This was a task that challenged the cruise speed capabilities of the T-51 and the low-speed handling of the P-51. That photo mission highlighted one of the shortcomings of an airplane that was supposed to have the look and feel of a fighter. It needed more power.
Williams came to the same conclusion, and since then two more engine choices have been developed. With the new engine choices, we decided to take another look at this replica fighter.
Titan Aircraft was started inside Williams’ industrial temperature control business when he started producing the ultralight CGS Hawk as a contract manufacturer in 1987. The ultralight business was struggling, and Williams had a vision to design and build an airplane, so he abandoned the fabric wings of the Hawk and designed a metal airplane he called the Tornado.
The T-51 definitely captures the profile of the P-51.
While he was designing and building the Tornado, there was a P-51 Mustang based at his home airport of Geauga County Airport (7G8). Williams took measurements and photos as he formulated a plan to build a replica. Life and business intervened, and it wasn’t until the Tornado business slowed down in early 2000 that he had time to commit to the project.
Titan did not try to build its new airplane like a Mustang. The mission was to build an airplane that looked like one. To keep the costs down, the company employed many of the same construction techniques used in the Tornado. Most notable of these is the aluminum-wrapped, solid-foam cores that shape the wings. This forms a composite of aluminum and foam that is incredibly strong, very light and inexpensive to build. From the outset the idea was to put more power on the airplane than the original Rotax, but Williams was not satisfied with the propeller-speed reduction units (PSRUs) available at that time.
The Rotax engine fit in the cowling and was dependable, but even the turbocharged 914 lacked the power to provide the feel of performance expected in a fighter. Williams was “adamantly opposed to auto conversions” and worked hard to dissuade customers from installing them, but some did. One customer installed a six-cylinder Suzuki engine and designed his own belt reduction drive to fit the engine. The customer ultimately convinced Williams to fly the airplane. As William tells it, “I went to fly the airplane so I could tell customers with authority that it was a poor choice. It blew me away!
“The Suzuki 180-horsepower 2.5 L V-6 engine doubled the climb rate, solved the CG issues and only slightly increased the stall speed. I had to backtrack,” said Williams. He went so far as to buy the rights to the belt reduction unit the customer had designed and installed one on one of his own airplanes.
The Mustang “smile.”
Another Mustang smile (the pilot version).
Testing of the belt drive revealed some problems and Williams continued searching for a better solution. A T-51 customer had a relationship with Autoflight in New Zealand, which was building the Subaru PSRU. Introductions were made, and Autoflight agreed to design a three-gear unit for the Suzuki that would rotate the correct direction and, unlike the belt-drive units, accommodate a hydraulic propeller.
The Autoflight PSRU has a 2.26:1 reduction and an independent system that lubricates the gearbox and controls the propeller. The engine and gearbox weigh 315 pounds, 150 more than the Rotax. This moves the CG forward, which improves handling and allows more rear-seat passenger weight. Williams reported the Suzuki engine coupled with the Autoflight PSRU has proved very successful and is flying in more than 20 T-51s, some with over 400 hours in service.
If some is good, then more is better, and that led to the development of the Honda 245-horsepower V-6 engine. Autoflight modified the Suzuki PSRU to fit the larger Honda engine. This combination adds another 100 pounds and is probably the forward CG limit for the T-51, but more about that later. Williams reports 15 Hondas now flying, with the highest-time installation nearing the 350-hour mark, and it is proving to be reliable.
The Titan Aircraft team preflights the T-51 for its next “mission.”
The T-51 flown for this article was Honda powered and additionally was fitted with a GM belt-driven supercharger optimized for high-altitude performance. The pop-off valve was set for a maximum boost of 34 inches of manifold pressure. That is a pretty low boost pressure, and the purpose of the installation is really to normalize the engine rather than boost it, providing sea-level power to higher altitudes. The word supercharger implies performance, and while that is true, there are caveats.
The T-51’s colorful livery adds authenticity to the fighter look of the airplane.
A supercharger is an engine-driven pump that pushes air into the cylinders when the intake valves open. Because it is positively driven, it produces compressed air whether it is needed or not. The supercharger must be tuned to a specific altitude that allows the engine to use all the air it is compressing. Otherwise it actually takes power away from the propeller. As expected, Titan reports that the naturally aspirated engine outperforms the supercharged engine at altitudes below 5000 to 6000 feet and is 30 pounds lighter. For rat racing and all-around fun flying, it is doubtful the supercharger option would be warranted, especially in the lower altitudes.
The Honda V-6 engine utilizes only half of the 12 exhaust stacks, but they look cool.
All the T-51 variants have one commonality, Whirl Wind propellers. The whole point of the T-51 was that it would look like a Mustang, and that means a four-blade prop. None were available, so Williams approached Jim Rust of Whirl Wind Propellers to build one. Rust was busy but agreed to take on the project. After waiting a year for a prop, Williams offered to help out with production. Williams created Whirl Wind Aviation to assist in manufacturing Whirl Wind props, and now they work together to build, sell and maintain the products in several applications and industries.
The Whirl Wind on the T-51 is a four-blade, constant-speed hydraulic propeller with hollow composite blades. Unlike some of the earlier T-51s with smaller, narrow-chord blades, the new propeller really adds to making the airplane look like a P-51.
Rudder trim is a bigger issue on the 1490-horsepower P-51, but it is a nice feature on the Titan Mustang.
Aside from the bigger, meatier blades on the prop, little has changed outwardly since we flew the airplane in 2006. A couple of design philosophies are apparent when looking at a T-51. It has its roots in the very light Tornado, and several design features are carried forward. Ease of construction was important.
Because I had flown an earlier version of the T-51, I had some idea of what to expect, and little of the apprehension that sometimes comes with a first flight in a new type. But automotive-engine-powered aircraft often have system idiosyncrasies that warrant careful consideration. A lengthy cockpit briefing was in order and pointed out some ingenious engineering.
As on the real Mustang, the T-51 has that long nose.
One of the limitations of most auto-engine installations is single ignition. Titan circumvented this issue by installing independently powered, redundant engine computers that control fuel and ignition. The computers fire an independent coil for each cylinder. This means if a computer fails, you have a complete backup. If a coil fails, you lose only one cylinder.
The airplane might run a bit rough on five cylinders, but it will fly to an airport. This system adds the performance of electronic engine controls with reliability as good as or better than a traditional dual-mag, single-carburetor/injection system. Very impressive.
The rear seat actually has adequate room for a passenger.
In the cockpit, the location of the various controls mimics the real P-51 wherever possible, right down to the canopy crank. One of the nicest ergonomic features in the P-51 is a hand crank located at the lower right corner of the windscreen. Squeezing the crank and rotating aft causes the canopy to roll back smoothly. This is a feature that should be mandatory on every sliding canopy airplane. Titan captured that feature accurately.
The gear is hydraulically actuated by an electric power pack, and two valves in the cockpit allow it to fall out if that system fails. The flaps are electric and of a Fowler type to reduce stall speeds and provide for good short-field performance. This is very unlike the real Mustang, which is not a good short-field airplane.
Also unlike the real Mustang, the Honda engine starts easily. Turn on the fuel pump and the computer and hit the switch, and the engine is purring smoothly. Starting the real Mustang is an acquired skill that comes with time and occasionally results in a stack fire that can be of massive proportions.
The Titan T-51 cockpit has the utilitarian look and feel of a WW-II fighter aircraft, and it seems entirely appropriate.
The steerable tailwheel provides good control for taxi, and like the real Mustang, the nose rises high enough to require diligent S-turning during taxi. The runup is no different from any other complex high-performance aircraft, and with that complete, all that remains to do is fly.
An infinity stick grip adds to that fighter feel.
The Honda accelerates smoothly, the PSRU amplifies the torque, and the big 84-inch four-blade prop bites into the air quickly. The combination of these factors and the weight of the big engine in the nose bring the tail up instantly, and the ground roll is short. The airplane climbs and accelerates quickly.
Soon the power was back and we joined on the Cherokee, where Richard VanderMeulen and his camera were waiting to take the photos that grace these pages. The airplane was comfortable in formation with the exception of a small amount of slop in the roll axis where the control stick attached to the torque tube. Tightening the tolerance of the attachment would be an easy fix to an unnecessary annoyance from what was otherwise a very comfortable airplane to fly.
The power response of the engine, coupled to the big, slow-turning propeller on the light airframe, gave the airplane a feel of being very snappy. Pushing the power lever forward was rewarded with a positive push from the seatback. After a short formation photo session, we broke off for some air work and to explore the airplane.
The T-51 copies the massive counterweights featured on P-51 elevators.
Even with the forward CG of the supercharged Honda, the elevator forces are very light without being sensitive. Little trim change was required with speed or configuration changes. The engine instrument readings were rock solid. The airplane has an adjustable coolant door, but unlike the real Mustang, moving it has little impact on speed or trim. The engine thermostat maintained the coolant temp in the middle of the green arc, and it never moved.
I slowed the airplane to a stall in both clean and dirty configurations, and the buffet warning was significant with plenty of margin. The airspeed indicator showed numbers in the 70s, indicating the static system was breached, unreliable and reading the reduced static pressure in the cabin. This made all the airspeed data I collected meaningless, so we will have to go with the company numbers in the specifications.
Generous aileron travel provides an adequate roll rate.
The additional weight of the engine changed the personality of the airplane from the much lighter Rotax-powered airplane. The larger engine gave the airplane a more masculine and pleasant feeling. To be clear, it doesn’t capture the feeling of the P-51, but it moves the personality of the airplane much further from its ultralight Tornado heritage.
Finally the fun was over and it was time to land. We entered the pattern, slowed on the downwind and dropped the gear plus some flaps. The remainder of the flaps came down on base, and the airplane settled comfortably into a groove. I had little confidence in the airspeed indicator, but it was unimportant; the airplane is intuitive and communicated clearly that it was at a comfortable speed. The final was effortless. Crossing the threshold, I closed the throttle and brought the stick full aft.
The airplane reached a nose-high attitude but stopped increasing in pitch just before the mains touched. With the combination of the supercharged Honda, full flaps and ground effect, the airplane lacked the up elevator authority to make the full-stall, three-point attitude. It didn’t matter, because the mains rolled on smoothly and the tail set down soon after. Again the tailwheel steering was effective without being squirrelly. Moments later, with only a slight touch of the brakes, we were clearing the runway.
Nearly all aircraft designs get heavier as they mature. The Piper Comanche started life with a lowly 180-hp four-banger, and the final version sported a 400-hp eight-cylinder mill that was much faster. But the light 180-hp airplane is much more pleasant to fly.
The T-51 is an exception. Whether the wing loading was too low or the incidence was wrong for its weight is unknown, but Williams was correct when he reported that he was blown away when he first flew the Suzuki-powered airplane. Clearly the airframe was optimized for more power and more weight than the little Rotax could deliver.
Delivering the look and feel of an iconic WW-II fighter in an airplane whose heritage is found in an ultralight is a daunting task. It is remarkable how Titan has captured the look of the Mustang in the T-51, and the additional power and weight give the airplane a more substantial personality. There are about 2 million ($) reasons why most will never get to fly the airplane that is at the top of most pilots’ wish lists. But you can taxi up, spin around and crank the canopy back in either one.
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