Cox Extra 300 RTF

By Geoff Barber Micro-aerobat, enormous fun! Abridged review and flight video. Featured in the Fall 2014 Park Pilot.

Have you ever wondered how cool it would be to fly aerobatics in your local park? Have you ever thought about how cool it would be to own an RTF (Ready-to-Fly) aerobat for about a hundred bucks? That’s exactly what the Cox Extra 300 can do for you! With everything you need in one small package, you won’t be running to the store because you forgot to buy something. Interested? Read on! Before I even think of starting the assembly process, I read through the manual from cover to cover. It may not happen as often with a micro-size foam airplane, but it seems as though there is always that one step I miss—and discover right after I mix a batch of 5-minute epoxy! Thankfully, the Extra 300 required no epoxy! In fact, assembly could hardly be any easier. Assembly began by installing the four included AA batteries in the transmitter, and charging the 7.4-volt (2S) LiPo flight battery. The aileron servo wire was first connected to the receiver in the fuselage, followed by sliding the tab in place on the wing’s trailing edge. With the tab in place, the wing was seated to the fuselage, and a single screw holds the wing on the airplane. Take care when tightening the screw—it can be overtightened and damage the wing and fuselage. All that remained was sliding the wire landing gear into the plastic slot in the belly of the fuselage. With the landing gear in place, I waited for the flight battery to finish charging. Total assembly time was approximately 5 minutes! When the flight battery was charged, I turned on the transmitter, opened the hatch in front of the landing gear, and connected the battery. There was plenty of room inside the hatch for the battery, so it was easy to slide it in place and reattach the hatch. The Extra 300 was ready to go to the field in less than an hour, including charging time. With the transmitter on and the flight battery connected, the Extra 300 was ready. I set the little airplane on the runway and advanced the throttle. Within just a few feet, the Extra was off the ground and climbing! At a safe altitude, I released the sticks to see if any trim adjustments were needed. To my surprise, the Extra flew perfectly as it was assembled—no trim changes were required. I pushed the throttle to full and the Extra flew nicely. It was definitely not a racer, but it traversed the field length quickly. Gaining more altitude, I slowed it down to a crawl before it stalled. When it finally did stall, the nose dropped, along with a wingtip. Several stalls showed that the dropped wing was random, and it didn’t tip the same direction every time. Because the full-scale Extra 300 was built for aerobatics, it would be safe to assume that the model would do the same, and I was not disappointed. The direct-drive motor and two-cell LiPo had more than enough power for loops of nearly any size, and the roll rate was perfect—quick and precise without being too touchy to control. The rudder is effective for stall turns and snap rolls. Although there’s not enough power or control throws for 3-D maneuvers, the little Extra can perform all other sport aerobatics with ease! Around the 6-minute mark, I set up for landing. I kept a little power on until the Extra was a foot above the runway, and then pulled the throttle stick all the way back. The Extra 300 settled in nicely, but I noticed it was slightly “tippy” until it came to a full stop, probably because of the springy wire landing gear. If you plan to fly from an asphalt runway, it might be a good idea to add a small piece of clear tape to the underside of each wingtip to prevent excess “rash” when the wingtips touch the ground. On the second night I flew the Extra, the wind was blowing roughly 8 to10 mph. Surprisingly, the little airplane handled it quite well, and even hovered for a couple of minutes in the wind! Landing was more difficult, and I was happy to have the SafeProp system on the motor. The model was driven into the ground by the wind at the last second, but the propeller popped off and I found no other damage to the airplane! I’m very pleased with the Cox Extra 300. The FlightFlex foam construction adds a great deal of durability, and the SafeProp system keeps motors and propellers from getting broken. The Extra 300 went together in only a few minutes, looks good, and flies great. Well done, Cox!


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