Hirobo Eagle III-WC

Background

On May, 2003 Mr. Manabu Hashimoto of Japan re-claim the World Champion title after winning the FAI F3C World Championships 2003 held in Noto, Japan. This is his third winning of the FAI-F3C World Championship title. Hashimoto used a prototype machine, code named "Eagle III" for this competition. Immediately many interest generated about the Eagle III as to its production and details. (More information about Hasimoto's prototype Eagle III available here.)

On October 2003 Tokyo Hobby Fair, Hirobo displayed the production model of Eagle 3-WC that helped Hashimoto took title of the 2003 World Championship and also the 2003 Japanese Championship just one week before the show.

The Eagle 3 WC have been a top secret item developed jointly the R&D team of Hirobo with co-operation by Hideyoshi Kurokawa of Black Hobby as outside consultant. The development began right after the World Championships of 2001, and many evolutions and testing have been committed to result with what Hashimoto is using in Noto, 2003.

The market version of the Eagle 3 WC is a "pod and boom" version, with most if the features of the prototype machine as displayed in Tokyo Show. Hirobo would first produce 100 pieces of Eagle 3 WC, at a list price of 398,000yen (Around US$3,685-).

My machine arrived in the morning of "Boxing Day", just in time! It is a first production model and Hirobo already noted that its designated only for several Hirobo pilots and the Japanese domestic market. Later machines that is meant for worldwide sales might have changes and updates incorporated from feedbacks of the first batch delivery models. Worldwide delivery of the Eagle 3 will be scheduled around March 2004. As a result, I RECOMMEND DO NOT HOP IMMEDIATELY TO GRAY MARKET SHOP FOR YOUR OWN EAGLE 3 WC YET. WAIT A WHILE FOR THE OFFICIAL EXPORT VERSION FROM YOUR LOCAL DEALER AND YOU MIGHT GET A BETTER MACHINE!

Eagle 3 WC kit as it arrived	Just in time for "Boxing Day"!
Box content after opening up cover	Cool "Carbon Look" print on boxes

Design highlights of the Eagle 3 WC

So the big question is: "What's been changed"? Well, to answer, simply after looking at my kit, is that except for the canopy, landing gear, main blades, drive train and the whole tail everything is different! Especially changed are the main frames and the rotor head.

Basically, the lower chassis of the Eagle 3 WC is the same as the Freya WC, but with the upper chassis a new design. The most interesting feature of Eagle 3 WC upper chassis is Hirobo's patented Variable Pitch-Up System (VPUS). A "floating cyclic control block" is incorporated as part of the control system. This block, which encased the elevator and aileron servo, would compensate on minor cyclic controls to enable a linear cyclic control. The control surface of the aileron and elevator are now on a straight line, providing a linear cyclic control feeling. A one piece bearing block that extends from the front to the main shaft of the upper chassis, that holds the floating cyclic control block and drive train is used to provide stiffness to the chassis. A sliding bearing block, in between the elevator control arms assembly, would provide pitch control for fixed swashplate collective pitch control. Hirobo staffs are kind enough to take the cover off both Eagle 3 WCs and let me play with the mechanics a bit. I feel the collective pitch control with my fingers and found that it is very very smooth operation, and at the extreme cyclic positions the floating block would slide 1-2mm just to compensate for the linearity of controls.

The rotor head on the Eagle 3 WC is a new design named SSR-VII, which is based on the same design of the prototype rotor head used by Hashimoto to win the 2003 World Championship and Japanese Championship. The flybar control system comes from the SSR-VI, which provides a near 1:1 Bell/Hiller mixing ratio. The yoke part of the rotor head is new design, which consists of both a central teeter hinge, two coning hinges, and uses separate sprindles. The central teeter hinge allows the entire rotor head to tilt left and right in order to allow the blades to flap, while the coning hinges allow each blade to have its own independent dampening, to move up and down independently of the other blade to allow a coning angle to form in the hover. According to Hirobo, the SSR-VII provides further hovering stability compared to the SSR-VI. A set of new carbon paddles are included. These paddles have a more aggressive airfoil and provides better control precision compared to the Freya paddles. Each of these paddles weight around 40 grams.

Assembly

Upon opening the box, I noticed that inside the package of the Eagle 3 WC consists of three boxes.  One box contained the canopy, another had long parts like main blades, tail boom and tail carbon drive and one had the SSR-VII rotor head with the rest of all other parts.   All parts are packed nicely into different bags, with each bag according to steps of instructions.  Bags are packaged in a way that when I arrived to a step of instruction I open one bag that is tagged with the step number in relation to the instruction and all the parts and screws required for that step of assembly would be included inside that bag.

Like a kid, I could not resist to rip some bags off to see the parts.....First box contains the canopy and some parts. The canopy is the same as the Freya WC, with carbon window. Same high quality FRP and carbon finish, but no excitement there. The decals included is a new pattern for the Eagle 3 WC specifically. Inside the canopy is a bag that holds some tail parts and the new fuel tank. The new fuel tank is a bigger one compared to the Freya/Eagle II (600cc vs. 540cc).

Then on, I open the pack that contains the main frame boards. The carbon boards are now made by titanium coated carbon boards which is said to have more rigidity. I compare the "Titanium carbon" with regular carbon, and found that titanium carbon has a finer cross weave pattern, but a much cooler "gold-ish" look on the surface. While I don't know if the more stiffer frame boards will offer any flight improvement at this moment, but the "titanium" look sure makes the helicopter looks better!

Next comes to the long box that houses the main blade and tail parts. Included with the Eagle 3 WC kit is a specially embroidered main blade holder. This main blade holder could hold 2 sets of blades, and looks very good.  While the main frame board are made with "Titanium carbon", the tail fins, which are the same ones as the Freya WC, are made in regular carbon boards. I wonder why Hirobo does not include fins made with "Titanium carbon" to enhance the look? Other parts like the tail boom and tail boom support is the same item as the Freya WC.

The box that holds the SSR-VII rotor head comes next. The flybar control system is the same as SSR-VI, which provides a near 1:1 Bell/Hiller mixing ratio. However, the yoke part of the rotor head is new design, which consists of both a central teeter hinge, two coning hinges, and uses separate sprindles. The central teeter hinge allows the entire rotor head to tilt left and right in order to allow the blades to flap, while the coning hinges allow each blade to have its own independent dampening, to move up and down independently of the other blade to allow a coning angle to form in the hover. A set of new design flybar paddles are included. These paddles, named Eagle 3 WC paddles, are made in carbon and have more aggressive airfoil and provides better control precision compared to the plastic Freya paddles. Each of these paddles weight around 40 grams.

Next comes various small bags. On special interest to me is the VPUS system parts. The VPUS machined bearing mount comes in one block that extends from the front to the main shaft of the upper chassis. It holds the floating cyclic control block and drive train. This design incorporates bearing holders from engine to main mast and provides improved precision and rigidity of the frame. This piece by itself, is a piece of machined art in my opinion! However, backlash adjustment of the gears are not available so change of gear ratio might be difficult.

At this moment, after preliminary looking at the parts, I could say the workmanship is up to Hirobo's usual high standard of production, with lots of parts neatly machined and anodized in blue color. I could not resists myself in appreciating the fine workmanship of the SSR-VII rotor head and the VPUS lower support frame! I could say what Hirobo sell on the market for the Eagle 3 WC, if you follow the instructions, will result with the same unit that Hashimoto flies.

Plain canopy	New, bigger fuel tank
"Titanium carbon" main frame boards	"Titanium Carbon" and regular carbon
Tail parts and main blade holder	Tail parts with carbon tail fins
SSR-VII rotor head components	Eagle 3 WC flybar carbon paddles
VPUS parts	Drive train parts
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Other parts	¡@

All parts are packed nicely into different bags, with each bag according to steps of instructions.  Bags are packaged in a way that when I arrived to a step of instruction I open one bag that is tagged with the step number in relation to the instruction and all the parts and screws required for that step of assembly would be included inside that bag. I read the instructions manual once before assembly, and find the steps follow a more logical way than other WC machines in the past. In addition, the instruction manual of the Eagle 3 WC is up to the high standards as seen in the their Sceadu Evolution manual - gone are the "Jap-ish" that is usually seen in other Japanese made helicopter manuals, and unlike other previous EX or WC helicopters' manual the manual of the Eagle 3 WC includes not only setup data for Futaba 9Z, but also JR 10X and Sanwa Stylus. According to my previous experience, if you follow straightly to the manual on the linkage and setup data you can duplicate exactly the settings of that of Hashimoto's machine, and with the inclusion of more setting for different radio brands to duplicate "the factory" setting becomes easy. As far as I know, there is still no other manufacturers that would go this great length to satisfy their customers. In fact, take a look at all the top F3C contest helicopters available in the market, Hirobo is the only manufacturer that sells what their factory pilots use in contests. Try to see if you can buy the exact machine that Curtis Youngblood, Minoru Kobayashi, Shinya Kunii, Katsuyuki Sensui, and Yukihiro Dobashi uses in contest, and I could say any efforts doing that would go to the drain because these people flies special machines that is not available for sell to the public. This, as a customer perspective, is no good marketing.

Before assembly, like all other helicopters with carbon stack frames, I would first prepare the frames before assembly. For a detailed description on how I assemble a carbon stack main frame, please refer to my page about "Tips on assembling a helicopter ". While I am preparing the carbon frame pieces, I noticed there are many holes drilled on the upper frame boards. While some on tail drive part I could comprehend that they are for a belt driven tail drive, others near the front of the frames are meant for something. These holes should be for something in the works because some of them are in different shapes and were meant to have something install in them. Might these holes for another version of Eagle 3 WC?

Preparing the carbon frame boards for assembly

First steps deals with assembly of the elevator arms assembly. The elevator arm assembly comes pre-assembled, so there was not much work for it other than to install two linkage balls and two ball links. I compared the elevator arm assembly of the Eagle 3 WC with the Freya EX, and find that gone are the individual little cones that encases the ball links, with the Eagle 3 WC these holder cones are machined onto the A-arms, so as to provide more precision. The whole assembly mainly consists of 2 A-arms, a main bracket on the middle to hold the A-arms in position, and a round shape bearing block inside the main bracket. Of special the bearing block that is in the middle of the elevator arms assembly. This bearing block is meant to slide up and down with the whole elevator assembly on collective pitch changes. What puzzles me is that this bearing block, in this configuration, is really redundant as the whole VPUS assembly would provide the linear precision on collective pitch changes, and while this bearing block does serve as an additional guide to withhold the linearity of collective pitch change the use of this bearing block serve little. In my opinion, Hirobo could completely does away with this bearing block and still linearity of collective pitch change is ensures, but Hirobo keep this bearing block in the Eagle 3 WC design. Like the holes in the front of the upper main frame boards, this bearing block should meant something more coming in the works.....

Eagle 3 WC elevator arm assembly

Next come assembly of the fuel tank. This fuel tank of the Eagle 3 WC is a completely new item. First of all, the size is up from 540cc of the old EX fuel tank to 600cc now. Aside from size, the Eagle 3 WC tank is  designed to be held into position by ten rubber grommets , instead of six as the EX fuel tank. Besides, the grommets to hold the Eagle 3 WC fuel tank is much bigger and stronger in size. I always have some problems of the little flimsy EX tank grommets, and glad to see this change. Assembly of the fuel tank is no brainer, but during assembly I used a file to take of minor flashes on the metal tubes so that they would not cut into the fuel tubes. Also, I changed the inner tube from the original one to a one made by IM because the original one would go kink in extreme bend, and in one case I even find the tube tied a knot by itself inside one of my Eagle. With the IM fuel tube these problems does not exist so far with me. While the manual says the inside tube should be 100-105mm in length, I find that 92mm is the best length to provide best fuel flow without the fuel tube tangling inside the tank. After the fuel tank is assembled, I submerge it in water to check for leaks, and find that there is no leak. This step is very important because if you use engine with pump system like YS and the new OS 91 SX-H C. Spec PS if the tank leaks fuel pressure will not be consistent. In the past with EX fuel tank according to my experience only 4 out of 10 tanks that does not leak, but this Eagle 3 WC fuel tank is good on the first try.

While writing this, a lot of people e-mailed me about interest in retrofitting this fuel tank into their Freyas, so I measured the mounting position of this fuel tank into the Freya frame. I find that to fit the Eagle 3 WC fuel tank into the Freya frame mounting holes have to be drilled for the new grommet, but it should fit no problem.

Eagle 3 WC fuel tank component	Fuel tank body
Left is original fuel tube, while right is IM	Leak test fuel tank
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Assembled fuel tank

The upper main frames housed the several main shaft bearing blocks, elevator arms assembly, VPUS collective block, and the tail transmission assembly.  The elevator arm assembly should be finished in previous steps and was sandwiched by the two carbon frames together with the collective pitch assembly support. The VPUS machined bearing block goes from the front portion of the upper main frame all the way to the main shaft area, and provides improved precision and rigidity of the frame. I cannot keep myself from appreciating the very nice machined work of the VPUS block. The whole VPUS block is machined by a single piece of alloy. It incorporated the VPUS lower support bracket, the clutch bell bearing block, and a main shaft bearing block. By this VPUS block, precision, strength and alignment of the main frame is ensured. It truly is a piece of artwork in my opinion! However, to my dismay, the main shaft and the tail drive bearing blocks once again came pre-installed with inferior Thailand bearings, so I changed them to better quality ones from SKF. (Please refer to my page about "Tips on assembling a helicopter " on how to change bearings) Two main shaft bearing blocks, inherited from the parts bin of Freya EX, is to go above and bottom of the VPUS block. Each of these separate main shaft bearing block has a 1mm offset so while fitting these bearing blocks onto the main frame be careful of their orientation. The tail transmission assembly consisted of two separate set of gears and bearing blocks that was set at 90 degree to transfer power from the engine to the tail via pipe, and were being mounted onto the upper main frame. I temporary secure all the required bearing blocks onto the upper main frame carbon boards to erect the upper frame.

VPUS bearing block	VPUS bearing block
Bearing blocks after changed bearings	Composition of bearing blocks on upper frame
Temporary assembled upper frame	Temporary assembled upper frame
Main shaft used for alignment of bearing blocks	Squared upper frame even on first try!

Since during the assembly of the upper frames, I would use the main shaft to align the bearing blocks, so I skip step and fetch for the main shaft and the DTDS main gear. At first sight, I thought both the main shaft and the DTDS main gear are from the Freya parts bin, am I wrong on that! The Eagle 3 WC main shaft is a completely new item that features a higher rotor head setting than the Freya. The DTDS main gear consists of a completely one-way assembly that features a much stronger one way bearing. In the past, Hirobo Eagle series uses the same one way bearing that they use for all their other helicopters. While this one-way bearing is barely strong enough for the 61 size engine in the past, with the use of much stronger 91 size engines now the old bearing is a little bit weak. The Eagle 3 WC bearing is a round shape one-way bearing, with 16 needle rollers running on the inside of the one way bearing. 4 little screws are used on the side of the autorotation housing to hold onto the one-way bearing. The autorotation housing is once again machined in aluminum, and is anodized in blue color. The operation of this new autorotation assembly is silky smooth. Both the Delrin main gear and the DTDS lower gear are inherited from the parts bin of the Freya EX. Even the main shaft collar is a new item, which is a clamp on style, rather than the old style which would dent on the main shaft.

Assembly of the upper main frame is a pleasant experience, cause the VPUS bearing block provides a very good base for the squareness of the upper main frame. In fact, during assembly of the upper main frame, I just finger tight all bearing blocks onto the upper main frame, and placed the whole upper main frame on marble to check for squareness, and even though the screws are not completely tightened the upper frame is squared!

Eagle 3 WC main shaft, DTDS gear, and collar	Upper and lower DTDS gear
Composition of the Eagle 3 WC DTDS main gear	Stronger one-way bearing
4 screws used to secure one-way bearing	Clamp-on style main shaft collar

Assembly of the engine comes next as it is to be fit inside the assembly of the lower frames which comes later. I use a Hirobo special YS91ST limited edition engine as power plant for my Eagle 3 WC. The engine is to be sat on the WC engine mount. A clutch hub is to be  mounted with a cooling fan secured by the prop nut, and on top of the clutch hub are the clutch and the clutch bell. While I am assembling the engine part, I noticed two new parts. First is the clutch hub, which I first thought is the WC clutch hub of the Eagle/Freya. I always praise the use of woodruff key of the WC clutch hub design that does away the taper collet. There is no alignment problem with a woodruff key design and there is absolutely no need to dial indicate the fan hub. However, I am quite surprised to find that the Eagle 3 WC fan hub now uses a taper collet instead of the well proven woodruff key approach.....

Another new part is the new clutch pinion gear. In the Eagle/Freya era, their 12T pinion have gears that looks like small blocks. Due to the design of the Freya EX there is no adjustment of gear mesh allowed, so for Hirobo to fit a 12T pinion on a 10T pinion circumference they "cheated" and used smaller size pinion teeth on the 12T pinion.  While Hirobo's way is workable, the small block shaped teeth of the 12T pinion would "bite" on the Delrin main gear very much and increase its wear, due to the fact that the corners of the small blocks would always touch on the flat surface of the teeth of the Delrin main gear. The Eagle 3 WC 12T pinion gear comes with "real", triangular shaped teeth, and should provide better operation smoothness than the old "block type" pinion gear.

The stock cooling fan is a plastic molded item, in fact the same item of the Eagle/Freya. However, I noticed that the Eagle 3 WC fan now uses the plastic material of the Sceadu Evolution which is stronger and provides more resistance from twisting and distortion. The clutch was to be secured onto the clutch hub, fastened by two 4mm screws.  The whole engine sat onto the blue T-shaped engine mount, secured by 4mm screws. A two piece fan shroud was to be installed to cover the engine's heatsink. The fan shroud is once again from the Eagle/Freya parts bin. Trimming on the fan shroud is required for it to fit, and Hirobo included a diagram in the manual showing what to cut and trim on the shroud. The whole engine assembly was to wait until later stages of assembly after fitting the fan shroud.

Composition of engine clutch parts	Hirobo Special YS 91 ST special edition engine
How everything goes together onto the engine	New fan hub that use a taper collet
Trimmed fan shroud ready for mounting	Completed engine assembly
Completed engine assembly	Note new pinion gear

Its time for assembling the lower main frames.  The completed engine assembly and fuel tank are to be sandwiched by two carbon lower frames, and temporary secured by hex screws on a flat piece of marble to ensure square ness of the frames. Before the frames are to be put together, the rubber fuel tank grommet have to be fit into the frames first. The new Eagle 3 WC fuel tank uses a 10 point mounting system to fix the tank in between the lower main frame. The new fuel tank mounting grommets consists of 6 grommets that are to hold the tank in place, while 4 grommets are used to prevent the tank from rubbing onto the surface of the frame boards. All grommets are to be fitted onto the frame boards before joining the lower frames, and I recommend to put some lubrication on the grommets before fixing them to the frame boards because they are just fit. In addition, make sure that the holes on the frame boards to hold the grommets have the sides of the holes sand smooth, or gradually they would cut into the grommets. Compared to the old Eagle/Freya tank, the Eagle 3 WC grommets are bigger in size and provides a more solid mounting. Several cross members are used to hold the lower main frame in place, and these cross members are constructed with regular cross members each with both ends installed with a spacer that provides a bigger mounting area. According to the manual, the landing gear mounting brackets are to be fixed at this stage, but I skip that for later because with these brackets installed they will be in the way of the angle rule during measurement.

New fuel tank holding grommet	New fuel tank grommet to prevent rubbing
Outside of the lower frame with grommets installed	Inside of the lower frame with grommets installed
New cross members	Temporary assembled lower frame
Temporary assembled lower frame	Lower frame checked for squareness

Joining of the upper with lower main frame comes next. While dry fitting the frames together, I noticed that the portion of the upper frame is pressing on the fuel tubes as they comes out of the fuel tank, so I used a Dremel to route an opening on the lower rear portion of the upper main frame to clear the fuel tubes. At this stage, another pair of helping hands would be best to help ensure the whole main frame was squared.  Once the frame was set squared, I would unscrew each screw again, put on loctite, and secured them again to lock on the frame. Joining the frames looked easy, but if you absolutely want your helicopter to have a right mechanical foundation, you have to use a lot of care and attention at this stage. As I am going about securing the screws on the main frame the first time, I noticed a minor problem. When I try to put together the lower frames onto the upper frames I noticed that the long bolt seems could not be fully sit squared onto the frames, while the same is nonexistent on shorter screws. As I am going around to figure out why, I noticed that the original washers has a too small inside holes so that the long bolts could not fully bolt onto the frames. Since the ID of the washer is about 2.92mm and the part of the long screws that has shank and right underneath the hex head is at a taper shape and have thickness about 3mm, the washer could not completely sit square under the head of the hex screw. I tried and if I use force to really screw the long screw with the original washer the washer would become warp, but still the head of the hex screw could not sit completely on the washer and would leave a little gap. I use washers with 3mm inner holes on the long screws and have no problems. This only happen to the long 3X28 screws that has shank (i.e. a part of the screw body is NOT threaded) only.  It took me hours to figure out why......

After erecting the whole main frame, I fit on the landing gear bracket that I skipped from previous step. I notice that this landing gear bracket is once again a new design item that features a much longer length. Both ends of the brackets now runs longer than the length of the lower main frame, and at both ends cross members are used to join the brackets together.

Erected upper main frame	Erected lower main frame
Upper and lower frame ready to be joined together	Part of upper main frame clamp on the fuel tubes
Modification done to clear the fuel tubes	Notice washer could not sit fully onto the screw
Carefully secure each screw	Checking main frame for squareness
Checking main frame for squareness	Checking main frame for squareness
Left side of the erected main frame	Right side of the erected main frame
New landing gear brackets	New landing gear brackets installed
New landing gear brackets extends over the front	New landing gear brackets extends over the back

Assembly of VPUS floating servo block and various mixers comes next. The VPUS is one of the gem designs of the Eagle 3 WC, in that it provides a linear cyclic and collective control. The aileron and elevator servos are sit inside a floating block, where it would slide fore and aft to compensate for linearity on collective pitch control. The whole VPUS collective pitch system is quite complicated, in that it consists of a servo control block, two bearinged supporter for the sliding movement, several mixers and carbon pitch arms to link up the servos to the elevator arms assembly then on to the swashplate. So what all these complex mechanics does that makes VPUS so special?

Take the Freya WC as an example, when collective pitch is input by moving its pitch control arm, since the servos and controls are placed at an angle which is not perpendicular to the swashplate, during the swashplate slide up and down for collective pitch changes, the swashplate would not be moved completely level due to the fact that servo and the collective pitch lever are moving not in a straight line, but rather in a circular motion. As a result, during collective pitch movement a little amount of cyclic is dialed into the swashplate, which leads to slight deviation on control, especially on hovering.

In the case of VPUS, the cyclic servos are placed inside the VPUS floating block, which sits perpendicular to the swashplate. When collective pitch is input, the VPUS servo block would compensate for the slight deviations due to the collective pitch lever fulcrum. As a result, swashplate control would stay level. So with the VPUS system hovering control would become more predictable and precise. In FAI F3C, since its hovering maneuvers that takes up twice the point factor than other maneuvers, having a machine with a good hovering characteristics would help win more scores.

Coming back to the mechanics of the Eagle 3 WC VPUS system. The center point of the VPUS system consists of a box constructed with carbon plates, cross members and machined aluminum ball bearings hinging points on both ends, and the whole VPUS servo block houses the aileron and elevator servos. The VPUS servo block is connected to two H-shape hinges that connects it to the upper main frame, so as to provide lateral sliding motion of the VPUS servo block. Three pieces of thick carbon plates that serves as collective pitch control arms provides control of collective pitch by raising and lowering the whole elevator A-arms assembly, which would raise and lower the swashplate. The collective pitch control arms also consists of two levers that links up the control of the elevator and aileron from the servo to the swashplate, connects and control the sliding motion of the VPUS servo block. Basically, the hinging point of the collective pitch arm is on the back hinging point of the VPUS servo block, and due to the whole VPUS servo block could slide freely it creates a hinging point for the whole collective control arms that changes position to diminish any bindings. As a result, any bindings and control differentials on collective pitch control would be compensated by the change of the collective pitch control arm's hinging point position. I check the sliding motion of the whole VPUS servo block and it actually slide less than 1mm, with the VPUS servo block at its furthest aft position at the lowest collective pitch, would slide foremost at the middle collective pitch, and finally back to furthest aft position at the highest collective pitch. During flight, especially hovering, the VPUS servo block would continuously sliding as collective pitch changes.

The construction of the whole VPUS system, even though its quite complicated, is made easy by the very clear diagrams in the instructions manual. However, care should be taken on putting together the whole system to ensure smooth operation, especially on the six screws that secure the collective pitch control arms. These screws have to be secured diagonally so as not to push the whole assembly to one side, that would lead to unsmooth operation. After putting together the VPUS system, I could not help myself from playing with the collective pitch control arm and see the VPUS servo block interact.

Some minor parts are to be fixed onto the constructed main frame. The plastic servo tray is from the Freya parts bin. Two tail boom clamps and a tail servo plate, although looks familiar, but in fact are new item that enable the placement of the tail servo on the main frame. Unlike the Eagle/Freya, the tail servo of the Eagle 3 WC is placed right underneath the overhang of rear upper frame. This arrangement is made strictly for the use of the Black Shark 3 fuselage as the old type Eagle/Freya style tail boom hanging tail servo could not be used on the Black Shark 3.

Eagle 3 main frame with the VPUS components	VPUS control components
Overview of the VPUS control	Notice the brawny pitch control arms
Movement of VPUS servo block - at lowest pitch	Movement of VPUS servo block - at middle pitch
Movement of VPUS servo block - at high pitch	Top view of the VPUS system
Closeup of the swashplate and elevator A-arms	Push-Pull collective pitch control arm
VPUS floating servo support block	VPUS carbon collective pitch control arms
Tail servo mount	VPUS servo block
Right side of the main frame	Left side of the main frame

At this moment, as usual I will go around checking and re-tightening all screws on the main frame. In past steps there are some screws and parts that are being temporary fixed, and after having most important mechanics are fixed and set I would come back to these screws. The fan shroud is one of these items that I will go back to fix. When I am trying to fix set the fan shroud clearance and fix it, I find that the piece of metal that is used to fix the fan shroud to the main frame (Hirobo part number 0404-713) is a little bit too short. It should be about 2-3mm longer than the original one. I tried and only by brute force stretching the plastic fan shroud to the metal holder for them to fit together. This is not desirable as vibration from the engine would break either the shroud or the metal holder this way. As a result, I take the metal holder part off, and elongate the 3mm screw hole by 2mm longer for the shroud to fit.

Note the plastic shroud could not reach the holder	Note the plastic shroud could not reach the holder
Elongated metal fan shroud holder piece	Modified fan shroud holder

The important phone call from Hirobo

I e-mailed Hirobo about the problems I encountered on the washers and the fan shroud. Hirobo staff called me and give me answers and further tips on assembly.

About the washers, Hirobo confirm to me that the original washers should be used for the long bolts as the fitness of the original washer would create a better precision. During the assembly of the long screws and washer I just have to turn the screws real tight so that the washers would press fit onto the screws. I later go back to follow this advice.

About the fan shroud metal piece, Hirobo acknowledged this problem, and express that there will be a new part to fix this problem, and the part will be included in the official export version Eagle 3 WC.

In addition, Hirobo staff also told me about another problem they found about the fuel tank that need to be fixed. The mounting of the fuel tank to the main frame is by 6 pieces of rubber grommets that goes from the main frame to dimples on the fuel tank. Hirobo later find that the dimples on the fuel tank are too deep, so that the rubber grommets could not hold the tank tight, and during flight the tank would be loose and vibrate, creating lots of bubbles inside the fuel tank. Hirobo acknowledge this problem, and in the official export version Eagle 3 WC the fuel tank would have this problem fixed. For the moment, Hirobo suggest to use some materials to decrease the depth of the dimples on the fuel tank so that the grommets could hold the tank firmly. Taking Hirobo's instructions, I disassembled the lower main frame and take out the fuel tank. I used a digital caliper and measure the depth of the dimples on the fuel tank, which is about 4.3mm, and I measured and found that the grommet only have about 3mm that would go into the dimples on the tank, so there is a 1mm gap between the grommet and the dimple. I fixed this problem by cutting little pieces of double sided tapes to put them into the dimples to minimize the depth. After doing this, the fuel tank now sit tight in between the lower main frame.

While minor problems like the fan holder and the fuel tank should not have happen to a prestige machine like the Eagle 3, but Hirobo is brave enough to acknowledge and correct the problems, which is good. Once again this proves that getting first hand machines from grey market might not be such a good idea as problems like the above would be amended on the official export version, and in case problem still happens on official export version at least they will be covered by the legitimate official local distributor.

Height of grommet into dimple: 3mm	Depth of dimple: 4.3mm
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Pieces of double-sided tape inside dimples	¡@

After fixing the problems, next according to the instructions is the installation of the rotor head, but I skipped to servo installation first so that I could continue work on the main frame. Before fixing the servos, I test fitted the servos onto the main frame, only to find that part of the frame may interfere with the servo wire "pigtail". If not taken care of, continue rubbing of the servo "pigtail" on the main frame will finally cut into the servo wires, and may cause disastrous results. As a result, I use a Dremel to ream out part of the main frame to make way for the servo wire. Specifically, the rear top part of the aileron and elevator servo on the VPUS servo block, and the left side of the collective pitch servo opening have to be reamed. After doing that, servo wire could clear the main frame. At this moment, I also fixed the front upper canopy mount, and the two gyro mount onto the main frame. Both the upper canopy mount and the rear gyro mount are machined aluminum part anodized in blue, which looks very nice.

I use JR PCM 10X radio with JR 8300 Super Servos cyclic, JR 8301 on throttle and remote needle, a GY601 gyro and a 9251 on tail. I made all pushrods according to the instructions. While making the ball links, I used a JR ball link sizer to prep the links. For the aileron and elevator servo discs, make sure that both balls are not in line, but set back a bit from the center to prevent binding on the extreme position. After all servos and pushrods were mounted, I set up the radio exactly according to the setup data provided in the instructions for the correct movements and ATV. After servos and pushrods are set, I cannot help myself to play with the collective pitch and see the VPUS servo block slide back and forth.....the cyclics works extremely smooth! One way to check is that I would take out the aileron links from the servo, hold them with my fingers, and give extreme collective pitch and elevator, just to feel with my fingers to see if any of these extreme movement on other cyclic servos would backfire and give pressure to the aileron servo links, and I find none of that. Each cyclic servo seems to operate independent and without affecting the others.

Modification done on the main frame	Modification done on the main frame
Servo "pigtail" now clear the frame after mod	Servo "pigtail" now clear the frame after mod
Right side of mainframe after installed servos	Left side of mainframe after installed servos
Push-pull collective pitch	Metal rear gyro mount

After servo installation, I proceed to installation of rotor head. Another gem of the Eagle 3 WC is the SSR-VII rotor head. As usual, I completely disassembled the rotor head, which originally come pre-assembled by the factory, to take a good look at the rotor head. Looking at the components of the production SSR-VII, I notice the hub and the whole flybar control system comes from the SSR-VI and the blade grips are from the SSZ-II rotor head. Only the yoke is a completely new part. Basically, the production SSR-VII rotor head yoke is similar design of that of SSR-V and SSR-VI rotor head yoke, but at a narrower width. The sprindles are being held inside the yoke static. The sprindle pins, like that of the SSR-V, and VI, are not hinging points for the sprindles, so the sprindles could not flap by themselves. The SSR-VII uses metal covers to keep the sprindle pins from coming loose. The cavity that holds the teetering dampers is now incorporated onto the yoke. In between the yoke and each blade grip there is an O-ring, and during hovering a coning angle is formed due to each blade grip pressing on the O-ring. The flybar control system comes from the SSR-VI, which provides a near 1:1 Bell/Hiller mixing ratio. The flybar is a new one at 425mm length, and couple with a set of new carbon paddles. These paddles have a more aggressive airfoil and provides better control precision compared to the Freya paddles. Each of these paddles weight around 40 grams.

On re-assembly of the rotor head, I noticed that while the bearings and thrust bearing have been applied ample grease, the dampers and O-ring are not. As a result, I applied grease liberally on the dampers and O-rings to ensure smooth operation. I also pay high attention into measuring the flybar and paddles to make them level and balance. Once the whole rotor head is assembled, I put it onto the main frame, and think about how this rotor head would perform compared to the SSR-VI.....

Components of SSR-VII rotor head	O-ring used on sprindle
Main blade grip the same as SSZ-II	New yoke
New carbon paddles	New 425mm length flybar
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Completed SSR-VII rotor head	¡@

After putting on the rotor head, I go about assembling the landing gears.  The landing gears is the same item that comes with the Freya EX WC that is the low profile metal type. The landing gear is mount onto the main frame via 4 rubber dampers. While fixing the landing gear onto the main frame I notice that the damper screws are too short to be secured by the locknuts provided, and since there is no way to change these screws I used instant glue on the nuts to prevent the dampers from coming loose during flight.

Next came to the assembly of the tail unit.  Tail gear box, which is the same as the Freya EX, comes pre-assembled.  Tail rotor, also same one as the Freya EX, have two bearings and a thrust bearing on each blade grip for smooth operation. The tail boom is carbon weaved octagonal shape.  The whole tail gear box is secured onto the tail boom through screws and the metal vertical fin mount that was equipped with dampers for vertical tail fin mounting. Power is transferred to the tail through a carbon pipe drive that operated inside of the carbon tail boom. Tail pitch change linkage was a piece of carbon wire with metal rod ends, and it goes through four wire guides on the boom. The whole tail assembly is to be mounted onto the main frame through the two metal clamps on the main frame.  To prevent the boom from slipping, I used tapes on the boom portion that is to be clamped on for better security.  Two carbon tail boom supports are installed from the lower main frame to a plastic mount to support the tail, and another tail fin mount is used to mount the horizontal fin. As to the tail fins, they are the same carbon board 3D type of the Freya EX-WC, but these are being made of regular black carbon. I guess it would look nicer if these fins are being made of "titanium" carbon like the main frame.

Main blades and tail blades are made of carbon, which the same ones being used by the Freya EX WC. After mounting on the main blades, I proceed to set up the helicopter. I follow strictly to the setup data in the instructions manual, and find that they are very accurate. I just have to make the linkage strictly according to the instructions manual, inputting the set up data listed in the instructions manual, and I could achieve the same collective pitch set up as suggested in the manual.

The canopy is the same item as the Freya EX, with a new decal. However, I do not bother to use the new canopy and opt to use the old one of my Freya WC as the mounting positions between them are the same. I plan to put the mechanics into a Black Shark 3 body later. Finally, I put on the Funtech muffler and route the servo wires to finish the whole assembly of my Eagle 3 WC.

Close-up of tail gear box	Tail fins
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Funtech muffler and landing gear	¡@

Test flight - First day

It is a very fine sunny day at the field with moderate winds but winds today blows from all sides and constantly changing direction. Before starting the engine, I made a mental note about the landing gear might come loose because the threads of the damper is just too short for a secure mount on the frame. Although I used instant glue on the nuts, I don't know if it will hold during flight. I leave the canopy out for the first flight. Start the engine for the first flight, I notice vibration from the engine that is affecting the fuel tank. Fuel in the tank looks like its "boiling", but without bubbles. This seems that its the engine fan is not sit true onto the engine. Anyway, I take it out to the field. Taking it off, I noticed minor vibration on the engine. Besides the vibration, I could feel that the controls of the Eagle 3, especially the collective pitch, is very responsive, but not sensitive. However, not finishing 1/4 tank, one of the landing gear damper screw comes loose with the landing gear dangling. I immediately landed the helicopter. In the past, the landing gear brackets have threads so that when the dampers are mounted they will first be held by the threads on the bracket, the locknuts are there just for reinforcements. With the Eagle 3 landing gear brackets, the threads are gone, so the locknuts are the only key to hold the landing gear dampers. At stock approach, due to the threads that goes through the bracket is only about 2mm, so locknuts could not hold the dampers securely. Even with instant glue on the damper screws in my case the landing gear get loose in less than 1/4 of a tank. For a lack of a better alternative that I can think of, I used locknuts with nylon inserts, and screw them topside down, hopefully it could take care of the problem at least for the day so that I could think of a better way to fix this problem back at home.

After fixing the landing gear, I once again take the Eagle 3 out and finished the whole day with 6 tanks hovering only to break in the engine. I must say, with basic settings from the manual, and right on the first day of flight I could feel that it¡¦s a much more predictable machine in hovering than the previous Freya EX WC with SSR-VI. Right out of the box the Eagle 3 hovering performance, even without much tweaking, handles very refine already. The Eagle 3 hovering feeling is that the cyclics are not sensitive, but responsive, especially the collective pitch control. The collective pitch control feeling is very refine, even at a minimal stick movement on the radio the Eagle 3 would response. The aileron and elevator are silky smooth, and all cyclic seems to feel "independent" of each other... The cyclic are so responsive that it seems there is no "overflow"...i.e. the cyclics would respond to the rate of my control input, not much, not less. Cyclic control feels very linear. In one flight, I dialed in a little bit of exponential in the elevator and aileron, and immediately I feel that the control response becomes a bit mushy, not to my liking, so I cancelled it out. The use of VPUS truly shines during vertical take off and descend, it's almost like straight up and down without the need of much correction. The rotor head tracks straight, and hovering is rock solid. Gone are the "jittery" feelings of that of the SSR-VI. I thought to myself that if not for the engine vibration problem and fear of landing gear getting loose during flight this Eagle 3 would be the best one of mine todate for me to take a new helicopter to the field....I would have to fix the engine vibration problem and the landing gear problem to prepare for next flight.

Temporary fix for landing gear problem	Eagle 3 hovering without canopy for check
Eagle 3 hovering without canopy for check	Eagle 3 hovering

Test flight - Second day

After the first day of flight, I changed the fixation of the landing gear damper rubbers. Instead of the way as suggested by the manual, I mount them upside down, so that the screw part of the dampers would mount on the landing gears with locknuts fully locked up to the plastic grommet part. This provides a better and more secure mounting. In addition, I dial indicate once again the fan hub.

The next day of flight also are only few tanks of hovering to break in the engine. That day, I had about 3 flights with the Eagle 3, rain stopped further flight. This time, engine vibration is almost gone, and although still there is a little vibration from the engine it looks to me that its due to the engine still running at a very rich needle setting that leads to the engine not running smooth, but much smoother now than last week. I changed a bit on the setting as provided by the manual to suit my fingers more. Once again I must say that the Eagle 3 in hovering it¡¦s the best feeling that I've yet to try of all helicopters! The cyclics, especially pitch, is very predictable, smooth and controllable, and the best is that there is no "noise" in the control, i.e. what I give in control is what I get, so there is not much of correction during hovering. Although I have yet to try aerobatics, but I have no reservation about Hirobo machines' good aerobatics capability. I am going to fly it more, cure the vibe problem, then try a day or two aerobatics then put the mechanics into a Blackshark 3.

Test flight - Third day

The next day of flight first started with a few tanks of hovering to break in the engine. Then at the last flight for the day I take it up to try flying above the deck. First its only a few straight forward flights with stall turns at the ends, and once again the true colors of the VPUS shines again. Gone are the "jittery" feelings as seen in the Freya/Eagle in the past. I mean, usually at the exit of stall turns, when I gradually give power and level the helicopter, with the Freya/Eagle they would have a tension to fade a bit and requires correction, much like a car from a stopping start on slippery roads. However, with the Eagle 3, it just tracks straight, like another car with traction control. Still the aerobatics settings are from the manual, and its already very good setting. I could say that the setting figures as provided with the manual are not figures that Hirobo "catch from the air", and they are very useable setting data. I tried some rolling stall turns, and not only the Eagle 3 shoots straight and high, but the aileron have such power that the Eagle 3 could do a full roll after its vertical, and still continue to shoot after the full roll. At this stage, its still a pod and boom setting, I wonder how it could do after the mechanics is fitted in the Black Shark 3.

Test flight - Fourth day

Once again after a few tanks of hovering then take it up the deck. During push over it is very easy to hold still the helicopter. Gone are the "jittery" feelings as seen in the Freya/Eagle in the past on the stopover. Exiting the pushover the machine looks like it want to "jump off the cliff", which shows that the cyclic is very responsive. The powerful cyclic and the smoothness of collective pitch really shines in rolls, where it would just get into the roll like a sharp pinch through the air. All through aerobatics the merits of the VPUS shows very much because with the Eagle 3 gone are the "jittery" feeling and cyclic controls now executes with very high precision. Even at pod and boom, the performance of the Eagle 3 now is already much better than my very well setup Freya WC with Black shark 3 body. I wonder what the Eagle 3 can do after putting it in a Blackshark 3.......In two weeks I will know, because a painted Blackshark 3 is ready for installation anytime at the moment of writing.

Conclusion

If you are looking for the best F3C machine available in the market, this is it! The Eagle 3 is a very refined machine with very good control feelings. Except for some minor rough edges the Eagle 3 is a perfect machine. Hirobo once again have a winner. However, at its steep price and limited production the performance of the Eagle 3 could only enjoyed by a few who could afford