Apply low-tack tape to the fuselage extending past the cowl mount blocks (at left). Mark the blocks’ positions on the tape. Position the cowl and hold in place with the tapes. Then drill the 1⁄16-inch holes through the cowl and into the blocks. The Pitt’s “boiler room” (above) has lots of space for just about any battery and hardware mix. Installing equipment is a simple bolt-in process.
optimization. At 70mm back, the airplane will assume the torque roll position almost automatically. But at this c.g., the airplane is extremely snappy during regular flight. For example, the difference between re- maining in a smooth turn and rolling out of it is increasing elevator movement from 6 degrees “up” to 9 degrees. Unless you are an expert 3-D aficionado, I strongly suggest starting with a c.g. located 60mm back from the top wing’s leading edge (6-ounce nose weight) or, better yet, a larg- er, 2800 mAh battery for longer flight times. Elevator movement is far less critical and aerobatic maneuvers become smoother and easier to fly. Set up the high rate at 30 degrees move-
ment for all surfaces, all directions. Use 35% exponential on elevator and ailerons and 50% for rudder. Elevator low rates should be at 60% with 30% exponential; ailerons at 80% and 30% and rudder 75% and 30% ex- ponential. Adjust to your flying after the first few flights. When ready to conquer 3-D, move the c.g.
back to 70mm. But reduce elevator low rate to 50% while leaving the other control sur- faces as is. Adjust after you feel confident. This is an extremely responsive, maneuver- able and capable aircraft. Go slowly and you will really come to appreciate this airplane’s performance. Set the ESC’s brake at “none”. Despite be-
ing a biplane, Curtis designed a streamlined aircraft that almost refuses to slow down on approach. You will appreciate the braking effect produced by the wind-milling pro- peller during every landing approach.
Flying Now for the fun part, almost. But first
come the numbers. Using the 10–5E APC propeller, the motor produced 370W of en- ergy while drawing 37.4A @ 10.4V. Maxi- mum rpm was 10,600. Adding the 6.2-ounce Thunder Power eXtreme V2 45C, 2200 mAh Li-Po battery produced an all-up flying weight of 46.4 ounces. The power loading is 128 Watts per pound, more than sufficient for 3-D and basic aerobatic work. Takeoff run on grass requires about 75
feet; 30 feet on pavement. Apply only light elevator, use low rates, and allow the air- plane to lift off on its own. The Pitts 12 EP can hold a 45-degree climb straight from liftoff. The airplane quickly gains airspeed on the return downwind. This is a much faster airplane than might be expected. The low-rate roll speed is about three rolls
per five seconds. The rolls are very axial for a bipe. That is great roll performance. Loops can be smoothly flown up to ~125 feet in di- ameter. At the 70mm c.g., some “up” eleva- tor must be held while going over the top or the airplane drops its tail as it attempts to assume the torque roll position even while inverted. 60mm c.g. loops are normally flown. At either c.g. setting, snap rolls on low
rate are surprisingly gentle and easy to stop on point. Spins are equally slow with mini- mal altitude loss. However, carefully man- age elevator input during spin recovery to avoid any potential problems. Stall turns are pretty, with no roll coupling when the rudder is input exactly before the airplane stops.
There is some roll coupling at speed, enough that you will want to trim it out. In knife edge, the airplane pulls to the belly, as
do all biplanes, but not that much and can easily be trimmed mixing elevator to rudder. With a 70mm c.g., this is a natural 3-D aircraft. A 10-inch propeller does not pro- duce a lot of torque to counter roll a hover- ing airplane. But, even though the ailerons are located outside the slipstream, using them (I know-cheating) does start a torque roll. I am not much of a 3-D pilot but I can fly the basic Blenders, Falls and Wall. The Pitts 12 EP can do them all far better than can I. About 20% differential eliminates ad- verse yaw at slow 3-D airspeeds. On the landing approach, try to keep the
nose level or a few degrees positive. This air- plane seems to accelerate whenever the nose drops below the horizon. Once in ground ef- fect, the airplane stabilizes and flairs beau- tifully. Even with the ESC brake off, your first few landings will be long; so plan for that.
The approach speed is a little faster than
usual but managing the touchdown is a non- event and three-point landings with this air- plane are really nice. For only $100, BP Hob- bies has produced a real 3-D winner whose performance belies its “scale aircraft” looks.
Some final words For less than $200, including all equip-
ment, the BP Hobbies Pitts 12 EP is a su- per performer at a great price. Newer 3-D pilots can learn how it’s done without risk- ing a fortune and have a good-looking air- plane in the bargain. Practiced 3-D Masters can have a scale aircraft that does it all without looking like a fun-fly “something”. Its convenient size allows it to be easily transported and flown just about anywhere. BP has a neat model for just about every In- termediate or above R/C pilot.
At the suggested c.g Frank found the plane (at left) slightly sensitive. For better aerobatic flight set the c.g. at 60 mm instead of 70. While the wheel pants look great, they won’t work on even the shortest grass runways. Remove them (above) and use 2-inch wheels for best performance on grass.
FLYING MODELS 33
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