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Tuesday, July 23, 2013

The Sound Of Thunder

For those seeking a more economical alternative to the max performance of a P-51, the Thunder Mustang should satisfy your inner need for speed

First, despite the Thunder's superior acceleration and climb, torque isn't nearly as much of a problem. Sudden full-throttle application on the ground for takeoff or on short final during a go-around doesn't result in a loss of directional control or dramatic torque roll as it might in the P-51. The real Mustang is a much heavier airplane, 11,600 pounds versus the Thunder's 3,200 pounds. Similarly, a related problem arises when the Mustang's airspeed builds past about 250 knots. All that inertia makes for extremely heavy pitch response, demanding both hands on the stick.

In contrast, the Thunder retains comparatively light stick forces right up through 300 knots. Neither airplane is especially difficult to land, but the Thunder may have a slight advantage, again, because it's lighter and easier to correct.

Flying from the rear is more than a little challenging, as there are no instruments in back, and the only controls are throttle, prop, stick and rudders. The front seat folds forward to allow entrance/egress, so by definition, the rear seater must climb in first and exit last. Room in back isn't exactly spacious, but it's typically wide enough to accommodate most big men.

Engine start is a little different than in other aircraft. The dual FADEC ECUs take care of everything, timing, prime, mixture, so start is mostly a process of turning on the master, ignition and boost pump and hitting the start button. There's no primer or alternate air, and mixture control is adjustable but preset for start. Compression ratio is a high 10.9 to one, and when the engine comes to life, it does so with enthusiasm. It might be a stretch to compare it to a Merlin, but the Falconer's angry snarl as it catches and settles down to idle seems distinctly similar.

The Thunder's deck angle during taxi is significantly nose up, so S-turns are mandatory. As with the full-size Mustang, pushing the stick forward unlocks the tailwheel for maneuvering on the ground. Holding the pole full back locks the tailwheel in the trail position with only six degrees of travel.

Just as with other high-performance aircraft, things become a little busy in the cockpit during takeoff. Once the throttle hits the forward stop, the pilot immediately lifts the tail and then has only a few seconds before it's time to rotate at 80 knots. After that, he needs to retract the wheels quickly to avoid exceeding the gear door limit speed of 130 knots. With wheels in the wells, speed leaps to a best rate of 150 knots, and it takes at least 30 degrees nose up to hold that speed with full throttle.

One anomaly noted by test pilot Dave Morss on the prototype is that the Thunder Mustang climbs so fast, the digital manifold pressure gauge is dropping by roughly five inches a minute, so it's hard to get a firm reading of mp during climb.

Labels: Piston Singles


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