Kyosho Stearman PT-17 

 

 

The PT-17 is a Kyosho "SQS-series", high quality ARF. It is intended for a .46 glow motor or a bigger four-stroke. The specifications are: 

Span: 1256 mm 

Length: 987 mm 

Wing area: 46 sq dm 

Weight: 2900 gr (glow version 2500 gr) 

My PT-17 is equipped with an LRK 350/20-12.5 outrunner and a 10 cell Sanyo RC2400 pack. Controller is a Schulze Future 18.61 OPTO, using an 1100 mAh receiver pack.

The propeller is an APC 12x8 or an APC-E 13x6.5 (picture). I have not decided yet wich one is the best, both perform well.  

 

Even if it is an ARF, you have to do some building. For instance, the dummy engine is from two ABS plastic sheets. Glue, cut, sand and paint. Some aluminum tubing and wires are used for detailing. Overall, it is the well known high quality Kyosho standard. Maybe a bit "overdesigned", resulting in a high empty weight. But it feels like 'iron stove" crash resistance!

Most of my "building" was the modification of the firewall/motor mount, in order to fit the LRK electric motor. I just made a plywood (3 mm) box, open on the underside. 

 

The battery is just sticking out through the firewall and rests on an added balsa floor inside (in the normal fuel tank position). 

 

The receiver battery is located as far forward as possible. I did not need any ballast to get the CG in correct position!

The ESC is mounted on the ply box. Here is a Hacker, I later substituted a Schulze Future 18.61 (good for 60A) after I measured the current. The Hacker ESC was a size too "small". 

 

Apart from the ply box, the battery floor, a big hole in the firewall and some air venting holes in the forward cockpit floor, there were no additional modifications necessary.

Test flight 6 September 2003 

 

Since I had severe glitching problems, the first two attempts were aborted. I put in a new receiver, a Multiplex Mini DS IPD, with better interference rejection and a fail safe function. During a normal flight, the fail safe gets into action  about four times, mostly recognised by the motor throttling down for half a second. There is a glitching problem, but it is still possible to fly..

What about the flying qualities of my electrified PT-17? I can only say 'EXCELLENT'! There is more than enough power, it is a stable and very well behaving airplane with a smooth flight. Nothing difficult, not even landing the somewhat overweight plane. The aerobatics has to be made in a scale like manner. I. e. you must get some speed up before the manouever, you cannot rely on the motor to pull you through. The loops are big and round, and the rolls are.... well, not exactly axial... But this is the way I like it, an airplane shall fly on its wings, not on its motor! (Unless you have a 3D aerobatic machine...). The PT-17, glow or electric, is highly recommended. 

 

Today (13 September), the glitching problems are cured (I hope). I cut the power cables, and made them as short as possible. They are now slightly less than 20 cm. During my latest flights, there were no glitching problems! Let us hope it will continue this way, it is a beautiful airplane and it flies so well! 

 

Sunday 26 October 2003; two good flights today, no glitching or other intereference. This will be the end of my Stearman flying this season. Next take-off is planned for April 2004! The only change I will make until then is to try a 10 cell Sanyo 1950FAUP pack, that will save 200 gr flying weight. Today, I used a Ramoser propeller, set for 13x6.5 and this was a very good choice. With the help of a head wind, the take off run was only a couple of meters! Some other things I want to try next year, are coupled rudder to the ailerons for smoother turns and flaperons to make the landings at a somewhat lower speed than at present. 

 

April - July 2004: Many flights. Some "out landings" because of motor stops - maybe the ESC gets too hot? Bent landing gear, easy repair. Some flaperon during landing helps a bit, not much. If there is no head wind, the ground speed is a bit high when landing. But most often the wind is blowing, so landings are easy. It is still flying well, more than enough power when needed. Loops and rolls are no problems, stall turns OK. 

 

August 2004: Suddenly the receiver is "dead". It is as if there were no signal. I returned the receiver to the MPX Service Center. I got a brand new receiver back! Installed it in the PT-17 and now she flies better than ever. I also made sure there was cooling air over the ESC. Before this I have had some motor stops that I suspect was caused by a hot ESC. Receiver OK, no glitches, no sudden motor stops - perfect!