The twin ducted fan jet on the right is designed by Super Flying Model and sold in the U.S. by Hobby Lobby International. It is made from molded-bead foam construction, has a 47" wingspan, and meant to fly at around 47 oz. or 3lbs. The model resembles a Learjet 45XR with the lower dart fins on the tail. The larger engine pods are typical on an EDF powered R/C model.

Although the retracts worked fine, I did not feel that they would work on grass take-offs and landings. I was proven wrong right on the first flight. Not only did it take off from grass very well, it flew very well with no modifications other than the upgraded power system.

On foam planes like the Exec Jet, coating the nose tip, leading edges, and areas where there are no decals, with finishing epoxy, helps protect the model from bumps and rash with only a minimal increase in weight.

My Executive Jet looped with ease and performed very well even in some wind.

My power system was upgraded from the stock 3-blade rotors to the well balanced Wemotec 504 rotors while still using the stock pre-mounted fan units. Ductedfans.com sells a nice Dual Rotor Upgrade Kit (WE504ex2) for this purpose. The Wemotec rotors and adapters allowed me to use the 3.2mm shaft AMMO 28-35-3900 Brushless Inrunner motors to double my power level over the stock 2.3mm shaft SFM Outrunner motors. I used the recommended Thunder Power (TP21003SPL2) 3 Cell 11.1V 2100mAh Lipo Packs for proper balance and long flights approaching 10 minutes with mixed aerobatics.

The SFM Exec Jet flight testing went very well and the video below shows just how easy it can take off and land on grass. Although I did not try it, I expect that it can also be hand-launched without difficulty. Overall, the SFM Executive Jet exceeded my expectations and proved to be a great start to the 2010 flying season!

In the last AMP'D column, we left off with the "Version 2" Hero 100 Twin EDF Executive Jet from Nitro Planes ready to fly but without the retracts working. This is how we tested it on the maiden flight. I figured that if all went well, I would complete the air line connections and add the valve servo.

Not only did the Hero 100 take off with authority, it stayed on step the entire flight! We tested slow flight, flaps, and stalls.

When the plane landed, we were all impressed with the flight performance. It was time to make the retracts work.

In the video below, test pilot, Lynn Bowerman, takes the Hero 100 up for its maiden flight without retracts. The flaps worked well without any pitching, the struts kept the plane from bouncing on landing, and the navigation lights could still be seen in the bright sunlight. It was fun to finally see the PH-LAB airborne.

The retract valve and servo were conveniently mounted on the bottom hatch. Be careful to clear the wing support rods as shown. I used a pre-enjoyed micro servo that I had for many years. The regular tiny white "T" connectors and retract air valve are supplied in the Spring Air 301 retract kit.

The following parts were used for an easy hook-up and disconnect. Note that I simply secured the air intake mechanism with a few nylon cable ties up front. The stock tiny Spring Air tank was replaced with a larger Robart tank. When using the newer Spring Air valves, the air intake is on the center fitting side. When using the other side that it off center, weird things happen.

• Robart #169 Pressure Tubing
• Robart #172 Small Pressure Tank
• Robart #226 Quick Tees
• Robart #189 Air Line Restrictors
  

The Cessna Citation II (Hero 100) continued to exceed expectations. On the second flight, the retracts worked great and the passengers got a real thrill ride!

It was quite windy out but the Citation had plenty of weight and power to handle the conditions. On the very low pass, you can see the plane wobble a bit from the ground turbulence. The Spring Air retracts and Robart main struts performed very well using the Robart restrictors. The articulated knee nose gear from Golden Skies R/C does a great job at channeling the bumps up front. Although I probably didn't need the larger Robart (small air tank), I prefer having the reserve of multiple retract cycles available.

A few more flights on the Cessna Citation II went very well. After some quick prep work, the plane took off with plenty of authority and flew very stable. The retracts and struts continued to work very well on landings. Flight times were about 5 minutes with mixed flying and some safety reserve for landing.

I was at a local R/C show in upstate NY where Team Futaba's Dan Landis and his dad, Richard, were giving noontime demos on his giant scale aerobatic planes. When Dan spotted the PH-LAB Executive Jet, he was already nodding his approval before I finished asking if he wanted to fly it.

During the demo flight, full-scale Gulfstream pilot, Greg Kessel, performed the commentary as if being on-board with his new co-pilot that just received his license...in the mail!

The Aeronaut F9F Panther fiberglass EDF model was designed after the Grumman F9F-5 Panther. The Aeronaut model has a 52" wingspan and weighs about 7-8lbs when flying. It is an all fiberglass ARF with German-engineered quality which is the best I have seen to date. It sells with and without retract bays for about $700 at Icare RC and Ductedfans.com in the U.S. and at WeMoTec overseas.

In order to finish my Aeronaut Panther properly, I solicited the help of my friend, Paul Weigand. Paul applied the decals with expert precision and created some wing tabs so I could easily secure them for flight without gluing them permanently in place. A small screw on the bottom side of the wing not only secured it for flight but also marked the proper CG.

The original release of the Aeronaut Panther in 2003, which is what I have, did not have landing gear bays or cutouts in the fuselage. It took off from grass using only 700 watts on 16-20 NiCd cells. It could cruise around on only 200 watts in low wind conditions or speed up to over 100mph. The second release around 2007 had gear bays, cutouts, covers, and a battery bay.

Paul also created a long battery box using aircraft grade light plywood. The box allowed me to place the two 4s 4000mAh Blue LiPo packs end-to-end so that the weight was distributed along the fuselage and I could easily connect them in series for a 8s total.

Since we were taking the Panther off grass on its belly, we applied a wide strip of 3M Scotchgard Paint Protection Film on the bottom of the fuselage and tip tanks. This protection film is transparent and nearly invisible to the eye. It helps protect against stone chips, bug damage, abrasion, and weathering. The 3M Scotchgard Paint Protection Film is available in any size and length at Empire Clear Shield.

My power system for the Aeronaut Panther used newer technology components along with the proven high-quality WemoTec Midi Pro 90mm ducted fan with its dynamically-balanced rotor. The ARC 36-75-1 inrunner motor delivers about 2700 watts on an 8-cell LiPo pack in the Midi Pro 90mm fan.

Since the original power system for the Aeronaut Panther in 2003 was only around 1000 watts. My 2700 watt power system required some additional work to keep the intake ducts from imploding. Further, my "new" model had already been stored for 6 or 7 years in the box so the intake seams may have weakened. The intake duct lips were sanded and resealed along the opening rim with a fiberglass cloth coated with V-poxy. This was also done along the seam that goes lengthwise down to the DF unit. The V-poxy dries as hard as a rock so my intake ducting seemed much stronger after this effort.

Team JRs, Devin McGrath, tested the Panther on it first few flights. The flight performance was incredible and the glide performance almost unbelievable! Without any retract openings on the bottom, the super-clean fuselage seemed to glide forever, making the Panther difficult to land without proper setup.

After the first few flights, we decided that the tail flex of the horizontal stabilizer was causing pitch changes when the Panther banked too sharply at high speeds. When banked softer, at high speeds, it seemed ok. The tail was easily removed with the single screw and I glued some thin hardwood sticks along the sides and a third thicker one across the center where it meets the fuselage. This made the tail much stiffer with minimal weight gain.

The next set of test flights are scheduled for later this summer.

The RC Lander PC-Coated Panther uses a revolutionary new PolyCarbonate (PC) process that provides a hard 0.3mm shell finish over foam. It won't dent, break, or shatter. The PC is a lightweight coating that is lighter than fiberglass and adds durability to foam never seen before. The smooth glossy finish can be painted without surface preparation with a result that resembles a fiberglass model but has a lower cost.

At the time of writing this column, we were still experimenting with the RC Lander Panther. Although it did not have the power to take off from grass, it could be hand-launched when lightened by removing the landing gear and using the 4s power system. We expect that the 6s power system and retracts would work fine off pavement.

Tim Wan has introduced an upgrade power system for the PC Panther that utilizes their 76mm EDF. The thrust ratio is now close to 1:1 and the AUW is only 175g more than before when using the same 6s 3300mAh batteries. Flight times are still around 3 minutes with full throttle flying.