PA Extra 260 Review

HamRadioBug R/C Reviews: Precision Aerobatics Extra 260

Photo: one of the author's PA Extra 260 outfitted with
optional wing tip CF Vortex Generators, and Vox 13x5 prop.

Constructed of a strategic combination of carbon fiber (CF), balsa and ply via PA's FiberFusion® technique, the Extra 260 sports very light wing loading for superb slow and low 3D freestyle flight performance. Designed around PA's custom manufactured 905kv Brushless Outrunner electric motor (Thrust 30) the Extra 260 has more than enough power for even the most demanding aerobatic maneuvers.

PA Extra 260 Specifications:

Wingspan: 1219mm / 48"
Length: 1094mm / 43"
Wing area: 490 sq. in.
Flight weight: approx 955gr / 33.7oz.
Wing loading: approx 9.9oz / sq. ft.

Precision Aerobatics Extra 260 web page: http://www.extra260.com/index.html

Long time r/c airplane enthusiast looking to make the transition from glow/nitro over into the exciting and performance packed arena of electric flight will feel right at home flying the Extra 260. With the control surfaces set up for conservative or precision throws, even beginning pilots that have soloed and safely landed the traditional 4 channel trainer, having mastered orientation, can easily handle the Extra 260. With it's light flying weight and generous wing area, the Extra 260 slips through the air with the smoothness and the feel of a much larger model. Properly balanced and in calm weather, the model's low speed flat glide characteristics are such that it can literally land itself by the pilot simply lining it up with the runway and letting go of the sticks (remembering to cut the throttle once the plane settles on the runway of course).

While the Extra 260 excels at close in slow-N-low 3D performance, it is also a good precision-flying practice platform as well. The owner's manual gives complete setup information for both 3D and precision. Being of compact size and fitted with removable plug-in main wing halves the Extra 260 is easily transportable for those impromptu practice sessions. The airframe fits with room to spare in the backseat of most any compact automobile.

Set up notes

Servos:

Servos in 3D aerobatic models tend to get a good workout. Best to choose a good quality dependable servo, one with a proven track record. The author's choice for this model is the Hitec HS-65 series. The HS-65MG is the metal gear version and the HS-65HB is the Karbonite gear version. The HS-65MG servos can be installed all the way round. Or, to save a few grams in weight, the "HB" version can be used for ailerons while keeping the metal gear "MG" servos on the rudder and elevator.

Props:

*APC 13x4E nylon; Tons of thrust but with low flight speed due to low "4" pitch. OK for slow 3D flying.

*APC 12x6E nylon; Good general purpose prop for sport and basic 3D. Nice top end speed for precision flying.

*Vox 12x7 wood; Similar performance to the APC 12x6E but with better efficiency, and my choice for precision flying.

*Vox 13x5 wood; Very good balance between top end speed and thrust for 3D. Good flight duration. My favorite prop.

*Vox 13x6.5 wood; Excellent top end speed for tumbles and excellent thrust for 3D, but with lower flight duration due to higher drive system power used. Strict throttle management along with directed cooling air to the motor and ESC being a must. Motor cooling air-scoops are provided in the Extra 260 kit, and the ESC mounting is covered in the assembly-owners manual.

3S LiPo packs

*3D freestyle aerobatics; Lightweight is the axiom here and best to go with a pack weighing no more than 165 grams. Author's choice is Hyperion's CX G3 2100 mAH, a 25C rated pack.

*Precision / F3A practice; A heavier 180 ~ 190 gram pack may used as an aid to increasing airframe wind penetration characteristics. Packs used in the author's model are the Hyperion VX G3 2200 mAH, a 35C rated pack.

Flight duration tests

Battery packs used extensively in flight tests include both of the above mentioned Hyperion LiPo packs. Throttle management, especially on downlines, was and continues to be practiced as an aid to conserving battery charge. After gathering data from several flights it was clear that the transmitter's flight timer could be conservatively set to 7 minutes. At a flight's end, once the timer sounds and landing is accomplished, the total flight time measured in the range of 7:30 to 8:00 minutes. On average the CellPro 10S DC charger indicated putting 1200 ~ 1300 mAH back into the battery packs.

These flight duration tests were conducted in calm weather conditions, 20° ~ 30° C. ambiet air temperature, and using both the Vox 12x7 and Vox 13x5 props, and executing a mix of precision aerobatic and 3D maneuvers. The Thrust 30 Brushless Outrunner motor was checked at the end of each flight and found to be only just barely warm to the touch, a tribute to Thrust motor's unique RotorKool™ technology.

To date [02/27/2012] over 300 flights have been logged on the author's Extra 260. Keep in mind that the use of quality LiPo battery packs is required to achieve the best results in performance and flight duration. Your mileage may vary. Depending on a pilots throttle managing skill and flying style, flight times will obviously vary from pilot to pilot. Each must personally determine the optimum setting for their flight timer. If in doubt select a lower setting than mentioned here.

Airframe Construction

The overall build quality of the Extra 260 is very good. The nicely designed balsa and lite-ply airframe is heavily reinforced with multiple CF rod and CF plate components making for a very light and strong airframe. The removable main wing halves connect to the fuselage via a common CF wing-tube to facilitate transportation and storage. PA went to great lengths to reduce weight throughout the airframe's design, topped off with carefully chosen hardware including CF control horns, CF push-rods, CF main gear, and extra light wheels. The airframe is covered and trimmed with iron-on film, and sports extra light fiberglass cowling and wheel pants. Long time balsa model builders who have mastered iron-on covering techniques will often comment "nice build" when looking closely at the Extra 260. PA models are hand built and do tend to appear to be home made; a characteristic of the wooden airframe's finish sanding prior to covering, and the manor in which the covering is ironed into the wood's surface for maximum added structural strength.

PA Extra 260 Assembly Notes

* CF control horns: Variations in manufacturing can result in somewhat over-sized pivot hole, resulting in unwanted play between the push-rod's Z-bend piano wire and control horn. In both of the author's kits, the push-rod's Z-bend piano wires measure .039~.040" dia., yet the control horn pivot hole was found to be approximately .050" dia. Unwanted linkage play can be removed by several techniques. One method is to slightly flare the CF control horn pivot hole opening (via hand twisting a small drill bit) to increase surface adhesion area, then filling the flared area and hole with 30 minute epoxy. Once the epoxy has set, re-drill the pivot hole to the correct size. It is a good idea to roughen the surface area around the hole with sandpaper to increase the adhesion of epoxy glue.

* Motor Mount: As per assembly manual, inspect the plywood motor mount glue joints reinforcing them with glue where needed. Personal adhesive favorites for this job include medium CA (Cyanoacrylate) and 30 minute epoxy.

* When using other than PA's iPA servos, the servo bay mounting slots may require resizing. I.e. for Hitec HS-65MG servos the mounting slots must be lengthened a bit. Before enlarging the mounting slots it is a good idea to reinforce the servo mounting screw wood doubler blocks with CA, or epoxy. Otherwise the doubler blocks may pop loose while drilling the servo mounting screw holes.

* Main gear axles: Assembled as shown in the manual, the left main gear wheel can spin the lock nut off the axle during takeoffs and landings. To prevent this an alternate axle assembly method is recommended as follows. Run the machine screw axle through the wheel first, then fit the locknut, then the jam nut, and mount it to the CF landing gear strut with the remaining nut - placing the washers as per assembly manual instructions. Non-permanent thread lock may be used on the lock nuts as added insurance against loosening over time.

* Carbon Fiber Landing gear struts: Variations in manufacturing the struts can increase the material thickness at the outer mounting hole area, placing the mounting hole in the angled portion of the strut. This may result in the supplied screws seating well up on the angled portion of the strut (photo). You may wish to use "non-soldered washer" screws at these locations to achieve a better fit.

*Balancing / CG when using other than PA's recommended Li-Polymer battery pack maximum weight specification of 165g. Many generic 3S 25C packs used by the author weigh in at between 180g and 190g. To obtain the recommended 98mm 3D CG required shoving these slightly heavier battery packs far aft right onto the pull-pull rudder servo. It was necessary to remove the pull-pull rudder control system, and move the rudder servo to the tail end of the fuselage. The fuselage has a rudder servo mounting positions already built into the tail area, and a push rod similar to that used on the elevator was fashioned for it. Once the rudder servo was relocated the model balanced properly with the battery pack positioned in the center of the battery tray.

Control Throws: Full control surface throws are used in the author's set up, and with the recommended 70% "expos" programmed into the r/c transmitter. This is very close to optimum, and the amount of expo can then be reduce as per individual preferences to obtain the desired feel and responsiveness.

3D "Noob" Corner: Landing The Extra 260

Beginners may find landing the Extra 260 (along with other 3D aerobatic models) a bit tricky when the plane is balanced at the factory recommended 3D performance CG setting. Balanced at 98mm the Extra 260 can be flown down to a very low airspeed that will be below the horizontal stabilizer's stall speed while the main wing continues flying. The effect observed on making an excessively slow landing approach is that as the plane slows the tail will drop, and then the plane will balloon skyward. While this effect can be corrected for with a more forward "sport flying" CG setting, the danger then is that the plane can be flown down to the stall speed of the main wing too, at which point the whole aircraft is in danger of stalling and "hammering" the runway.

When learning the flight characteristics of the Extra 260 on the factory recommended 98mm 3D CG setting, and since airframes make poor hammers:) it is best to make the landing approach at a speed above the horizontal stabilizer's stall speed. On a clam day one can simply fly straight down the center of the runway, just a couple of feet high, using about 25% throttle. Once lined up proper just cut the throttle, let go of the sticks, and the plane will land itself -- a common experience among Extra 260 owners. The pilot would do well to practice these stabilized low speed landing approaches, and flying straight down the runway at just a few feet high, until proficient. It is also helpful to use "low rates" on elevator and ailerons for landing as an aid to keeping them as smooth as possible. On windy days adding in a few "clicks" of down elevator trim just prior to making the landing approach can be helpful.

Byron Campbell
rcgroups.com: wa4geg
contact: wa4geg @ netscape.net

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