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Friday, August 3, 2012

Freewing Su-35 Super Flanker-E - Build and Flight Review

INTRO                                                                                                                               
Sometimes called the "Super Flanker", the Su-35 is a formidable 1v1 dogfighter by anybody's definition; maybe the best in the world.
Too bad the days of one-versus-one dogfighting have been gone for nearly 50 years. But by WWII-era aerial performance standards, the romantic ideal most of the world's aeronautical engineers remain fixated upon to this day, the Su-35 rocks!

In today's day and age the Super Flanker has no hope of seeing an air-to-air merge, this sitting duck will most likely be disposed of, en mass, before it takes off. We (the good guys) had better hope we don't lose our 5-6th generation advantage in a future conflict, lest the air war deteriorates into pick-up basketball and we could lose big to bullies like the Flanker-E.
The Su's advanced aerodynamic maneuverability, thrust vectoring, and high T:W make it a perfect RC model.  Here it comes...

SPECS
- Wingspan: 42.5 inches
- Length: 64.2 inchess
- Flying Weight: 106 oz (6.7 lbs)
- Drive System: 2x 2200KV Outrunner Brushless Motors
- EDFs: 2x 70mm
- Servo: 9X 9g micro servos & 2X 17g servos
- ESC: 2x 50A Brushless speed controller w/ 5A BEC

FEATURES
- Construction: EPS
- 2-axis (360 degree) Thrust Vectoring
- Full Metal Servoless retract system

REQUIRES
- Radio:  6-9 channel 
- Battery: 22.2V 4000-5000mAh 25C+ LiPo

PAID
- $275.90
- Less 20% (Model Airplane News Reader Discount Code "MANR6731")
= $220.72

PLANNED UPGRADES
- Z83X
- High Amp ESCs
- 10 blade EDF fans

ON THE GROUND                                                                   

UNBOXING

Apparently there are two versions of the Su-35 model

Impressive level of completion right from the start

Very nice set of specs!  There are 105.82 oz of thrust and not one gram less.  Freewing was kind enough to include 3 tons of 5 min Epoxy, quite a value!

The model is technically larger in both dimensions then the LX Models F-22, but the overall scale seems more like 10%-15% smaller, maybe due to the pointy nature of the Super Flanker

Not EPO, but the wings are reinforced with Aluminum bars, unlike the LX models F-22.  The full motion horizontal stabilators sport much higer quality pivot hardware and metal gear servos

The servo wires and extensions are easy to access for every flight control. Freewing has even included aerodynamic covers for the open wire channels, shown above.

The motors run smooth because the 6-bladed fans are well balanced

APPEARANCE / FIT N FINISH

Freewing has done an excellent job with the Flanker-E.  The model falls together very quickly and intuitively enough to make instructions optional.  The paint looks fantastic and there are interesting  decals everywhere--most don't seem to appear on the real plane, but I'll take Freewing's word for it that the patterns exist somewhere.

All the pieces fit perfectly and the end result is, in a word, bada$$.

BUILD QUALITY/SETUP

All of the servos are installed and ready to go with plastic covers in place to avoid scuffs from the inevitable bumpy or gear-up landings.
The hardware and base design is better all around than my similar LX Models jet.  The key servos are metal gear, the wings are removable with aluminum spars and plenty of servo lead wire to let the wing go.

The landing gear struts are all metal, but the super cool, scale nose gear with twin tires, mud deflector, and sliding trunnion and sequenced gear doors could be tough to repair--I can't fault Freewing for the awesome scale details.

The tip of the nose has a plastic cone which is a more durable approach to the first thing to arrive in  strange new territory. 
All of the interior wiring is clearly labeled and there is plenty of wire to maneuver.   The ailerons are wired as a Y, but the wire-channel from wing root to receiver bay is accessible (by inserting a thin wire poker to hook it and pull it out) for those who want to run independent aileron servos.

All of the linkages and  screws come in a bag of bags.  Each individual bag has a parts inventory sticker--a nice touch and a clear statement of attention to detail.   Ask yourself this question:  when is the last time you could identify which control horn goes to which surface based on the matching paint color combination of the control horn and the horn's back plate?  All the clevises come pre-wrapped with surgical tubing to prevent inadvertent disconnects in the air.  The hardware pack is decent quality stuff.  A nice screw driver with replaceable drives is also included.

The flight controls and the thrust vectoring system is setup servo by servo (after each flight control set is Y'd together), which I love but some might not like because it requires 8 channels and some decent radio mixing power to play the thrust vector game; 9 channels if you want to differentiate the ailerons so you can use them as flaperons.

Channels 6, 7, and 8 need to be mixed to the appropriate flight control axis.  The nozzles work together as elevons which can also pivot in yaw.  This "pure" setup allows lots of control over the thrust vectoring type and amount.  Neat!

This model represents a new level of attention to detail, pre-assembly, and general design quality.  Everything worked perfectly out of the box.  Freewing, you have sold me on the notion that you are trying a little harder to get things right.  This is one of the nicer Made in China products I've seen.  Better still, the price is right.  Bravo!

GROUND ISSUES

  • The nose gear has some fore/aft play in the servoless retract mechanism.  It remains to be seen if this is a ground handling or strut strength issue.  The strut itself is solid metal with excellent nosewheel steering precision.
  • The picture of the CG point, and the verbal description stating it is 145-155mm back from the Leading Edge at the side of the fuselage, don't quite match up.  The graphic CG depiction, based on the panel lines both on the plane and in the CG diagram, measures about 165mm back from the LE.  At any rate, it is evident that the 6S 5000 mAh 40C battery I'm matching to this plane is not going to fly tail heavy.  Even with the 5000 in the aft-most battery bay position, the plane balances around the 140mm point.
  • The non-EPO foam requires pre-assembly crash proofing for best durability and looks.
  • Funky aircraft battery connector matches nothing much and will need to be replaced--I change most connectors to my own standard--but this one requires heavy gauge soldering pretty close to lightweight foam body panels.  It's the one set of wires without much extra length.  Figures.  Soldering requires extra care.  Thankfully, Freewing included an extra set of bare battery-side connectors, so making a plug-in battery adapter is easy.  I like to limit the amount of cable and connectors between the battery and the ESCs in high-amp applications.
  • Overall, the above are hardly even issues unique to the plane; this jet was amazingly issue free during assembly!

IN THE AIR                                                                              

Cool

BLUF

A very well executed model that flies beautifully; let down only by heavy battery weight or shorter than expected flight times--take your pick.

START/TAXI/TAKEOFF

The landing gear configuration gives the flanker good manners and maneuverability on the ground.  There is significant slop in the servoless retracts but it doesn't impact controlability much when taxiing.  In general, the retractable landing gear are a weak point in an otherwise well made design.  Including undersized servoless retract units seems to be a trend with all the stuff coming out of China today.

GENERAL CONTROL

The Su's basic design is very stable in flight, but with a strong ability to pitch up hard.  Extreme pitch-ups stay beautifully controlled around the lateral axis; the long, blended strakes energize votices over the fattest part of the wing to deliver consistent nose-up tracking or turning that keeps on giving down into very low speed regimes.  Strong nose tracking at almost any airspeed is a Flanker strength.

Roll authority is less impressive from the inboard aileron config.  The plane is least stable on the longitudinal axis due to the wing sweep, so it's not the worst thing to have a tad muted ailerons to keep from over-correcting.  Spirited rolls result from the application of full rates; but there is nothing special to see here, so move along. 

Yaw authority is inherently high with the double rudder, and you'll probably need every ounce of that authority with the wide motor spread anytime an engine coughs or quits.  Add thrust vectoring and yaw axis control is so strong it's almost too touchy.

This jet would be a great candidate for Z83X gyro system, and that just might happen sooner rather than later.  One drawback is the number of servos on the flight control grid.  Depending on the gyro system implementation, you might need quite a few of them to cover both the flight controls and the thrust controls.

The brightly painted scheme is easy to see and orient.

The high output fans have a great "whoosh" to them in the air.

BALANCE & AEROBATICS

Airborne CG feel revealed that the verbal CG dipiction is the correct one, 145-155mm back for the leading edge.  I thought the5000 mAh Lipo was likely to fly nose heavy, so I scooted it back a couple of inches in the battery bay, leaning more toward the pictorial CG depiction.  Surprisingly, the jet flew slightly tail heavy, wanting to inch the nose higher and higher in power-off glides.

Other than not wanting to come down with the power off, the Flanker handled the aft CG with ease, making it very agile in pitch, but without feeling too pitchy during steady tracking maneuvers.  Nice. 

The Flanker-E has no problem executing any aerobatic maneuver you can throw at it, from inverted spins to Knife Edge flight, the jet has more than enough power and control authority to go through the paces.  Obviously the plane was not designed for precision aerobatics.

On more than one occasion the airplane slowly fell off of high Alpha flight into a nose low attitude and tried to inadvertently spin.  The aft CG could have contributed to the tendency for auto-rotation .  There is plenty of yaw control, almost too much at times, to slap the jet out of any spin but you have to be careful not to snap into a spin in the opposite direction in graveyard fashion.  It eats some altitude to re-establish a steady platform.  That's a little disconcerting as one gets more proficient and wants to bring the altitude down.   I suspect the behavior is true to the airframe, and it might be better behaved with less battery weight or with the CG pushed farther forward.

The plane would benefit from a yaw gyro, since it is clearly set up by the OEM for computer-aided stability/agility.

All that said, I can't help but compare the Su to the LX Models F-22 that floats in and out of high Alpha without vice.  But the big F-22 wing with max slats and flaps can dig a drag hole that needs a fresh battery to power straight up and out, unless you sacrifice some altitude for airspeed.  So the two RC Fighters have different personalities when air flow gets scarce, but both can bite you.  Still, auto-rotation is not a nuisance with the F-22 setup, which is more refined and well behaved all around.

POWER SYSTEM
Thrust
Amps/Watts
Speed
Flight Time- About 5:30 from a 6S 5000 mAh with mixed aerobatics.

ADVANCED HANDLING CHARACTERISTICS

The basic design of the Flanker-E holds the RC model back, and probably makes the full scale plane somewhat sub-standard in similar ways.  The fundamental problem is a set of design goals that includes high speed intercept.  The high speed target forces a small slippery wing which really make the plane struggle in lower speed realms where fighting actually occurs (granted - assuming you can get the jet to the flight in timely fashion).  Because of the Sukhoi's basic shortage of wing area, wing loading is not on par with the smaller spec F-22 with similar on-board RC components, and slow speed maneuverability suffers.

The motors are strong, and the model takes the same approach as the 1:1 scale jet trying to makup for weak aerodynamic authority using thrust aimed in different directions.  But in the end, gravity is the Su-35's most competent, persistent, and relentless airborne opponent.  All the technology packed into the Flanker-E tends to lose the epic battle with mother Earth more often than it wins.

All that said, wild thrust vectored tumbles, flips, and general out of control flailing are the Flankers forte.  Sometimes there is more vector than there is control.  In fairness to Freewing, there is a Full House of flight control tools built-in and mixed with the computer, so this is a model that begs for tweaking and refining.  I'm sure that my setup is not optimized.

The Flanker's AHC capabilities are not lacking, that's for sure.  If anything the model is a bit too wild once the air starts squirting.  Without thrust vectoring, the plane is stable and dart-like.
Here is some First Person Video of an early flight - the first 2 minutes is trim adjustments:

The Flanker is fast and loud with great agility:

IN-FLIGHT ISSUES
- Flies more on thrust and speed than wing area.  Lack of efficient EDF technology is a ball and chain due to required battery weight to make the numbers work.
- T:W is generally inverse to available flying time.  Again, battery weight takes it's toll.  My hefty 6S 5000 40C could not quite deliver a 1:1 T:W and lasted 6 minutes with quite a bit of cruise. 
- Fast, hot landings (same issue: high wing loading).  Needs strong, high drag flaps.    Lowing full flaperons reduces controllability on final and the inherently fast touchdowns float even longer.
- Touchdown AOA is capped by the Su-35's long stinger, so spoileron use is limited during landing.
- A medium-hard landing revealed that the main gear struts were probably not fully tightened inside the retract housing.   As a minimum, no thread-lock was used since the hex-screws backed out a little and allowed the main wheel struts to rotate and drag a main gear upon touchdown.  Inspection revealed that both main gear struts were loose.  Each strut has flat spots machined into the metal to accept the set screws which makes the whole assembly fairly strong when tight.  The main gear servoless retract housings were easy to remove and maintain.  No damage resulted. 

APPROACH & LANDING

Setting up on final is easy enough, but don't get slow.   The model loves to fly a little tail heavy, so coaxing the nose down onto glide path is a little tricky, it wants to inch higher with less speed.  The slippery airframe doesn't want to shed knots.

I tried landing with flaperons but there is still high speed float once in ground effect.  I need to try spoilerons to see if increasing the AOA will create enough drag to shorten landing rolls.  Scraping the long stinger could be an issue.

Easy to land.  Not easy to stop in your home state.

OVERALL

I can't help but compare the Su-35 to my F-22.  Both have issues.  In a nut shell, the Su-35 is an well executed model of an aerodynamically needy airframe.  The F-22 is a cheaper-built model of a very refined airframe.  Take your pick, both are fun to own; I don't regret buying either one. 

Overall, the Freewing Flanker-E is a cheap, fast, sexy Russian bitch that freaks out once in a while.  You get exactly what you pay for. 

GRADES                                                                           

Appearance: A+
Hanging nose looks unmistakably Russian in the air--impressive presence.  Good color scheme for vis.  Luv it.

Aerodynamics: B-
Incredibly agile in pitch.  Slow speed behavior tricky in yaw axis.  Needs more wing area.  No flaps; long landing rolls need a dry lake bed.

Power System: B-
Powerful.  Needy.  6S 40C 5000mAh gets pretty hot.  Very fast fly-bys.  Nice T vectoring system. 

Build Quality/Durability: B-

Nice metal, carbon, and plastic reinforcements.  Cheap foam = hangar rash.  Internal landing gear set screws were all loose.  Two MG servos.  Thin foam inlets are a weak spot, but underside servos are well protected.

Value:  B+
@ $220 it's a lot of EDF for the money.  High battery cost.  Fundamentals are there, the weak areas are pretty easy fixes.

Overall Grade: B+
Heavy, fast, powerful, agile but aerodynamically rough around the edges = authentically Russian.  Fun!

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