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Rotorcraft

November 27, 2004




Building a RotorWay 162F, Part 4

 KITPLANES Magazine, June 1997

Building a RotorWay
Part 4 of 8: Installing Controls

At this point in our building process--with a fully assembled and painted airframe, a temporarily installed main shaft, and the body trimmed to fit and temporarily installed--I'd say we're about 30% finished with our RotorWay 162F. The construction time clock is at 150-200 hours so far, and it's either about right now or sometime pretty soon in the endeavor that many guys will stand back, look at what they've done, count up all the hours they've spent building and get really depressed!

Now Take It Apart   
   Currently we have just a shell of a helicopter, but it really looks like a whole helicopter! What makes it sad is that now we have to remove the entire fiberglass body to continue construction. Now you're left with only a skeleton of a helicopter! It looks as though just about the only things you have to show for all your effort so far are lots of hours in the construction logbook and a jungle-gym of painted metal!  
   The first time I built one of these mechanical beasts, I had to keep reminding myself that at some point, this machine really was going to pick up off the ground in a hover with me at the controls. I have great respect for guys who build kit airplanes, taking sometimes even thousands of hours to complete their projects. That's great dedication and commitment. Ours will need only a few hundred hours to complete, but after using microwave ovens and every other kind of modern-day instant gratification appliance, I've found myself wanting to hurry up and get this thing in the air! It's a funny dichotomy that the actual construction of a homebuilt aircraft is an enjoyable hobby, but at the same time, you still can't wait to hurry up and finish! 
   I mentioned in the last issue that it is a good idea to take pictures and document your kit's construction along the way. You should do this, not just for your own historical archives, but also because many FAA inspectors will want proof that you actually did the work. Make sure there are pictures of you doing the construction. 
   I also mentioned that it is a good idea to build the body and the controls somewhat simultaneously because these areas of construction are closely knit together both in proximity as well as in function. Last time we built the body. In this issue we'll build the controls and install them.     Then we'll complete the ritual that all builders must fulfill when constructing a homebuilt aircraft: You find a way to sit in the half-built cockpit, grab the controls, and make airplane noises. I think it's actually some kind of FAA requirement. And if you don't do it, you're a pansy. After that, we'll install most of the drive train.
   I hate to keep referring to the old days at RotorWay, but control construction is an area that has been so simplified in the last two kit versions that it would be a huge oversight not to do so.

Control Systems   
   There are four basic flight controls in helicopters: the cyclic; the collective; the throttle; and the directional, or pedal control. In the 162F, each of these controls is installed and functions via its own pivoting tube situated horizontally within the airframe and mounted via nylon plugs and aluminum bushings. All accompanying bracketry, control parts and cables are attached to these tubes and operate the appropriate control surfaces.
 There are no hydraulics, bellcranks or pulleys in the 162F; it's a very simple Point A to Point B setup. 
   For better understanding and to enlighten those new to rotorcraft, let's start with a quick description of each control's function. 
   First, the cyclic control in a helicopter does the all-important balancing act. It's the center stick that's held with the pilot's right hand and controls the "tilt" of the entire machine. It moves the swashplate on the main shaft that in turn tilts the rotor disk forward, backward, left or right, and the helicopter body then follows the movement. 
So, for example, when you push forward on the cyclic stick, the rotor disk tilts forward, pulling the rest of the helicopter forward with it. It will continue this movement, traveling faster and faster until the pilot pulls back on the cyclic stick. In hover mode, pulling back on the cyclic makes the ship slow down and will eventually bring her to a stop and then will start a backward hover if the stick isn't centered after the forward movement ceases. 
   Moving left or right in a hover is accomplished the same way. In faster forward flight, these same stick movements do basically the same thing, but pulling back or pushing forward on the stick will cause a slowdown or increase in forward speed as well as cause a climb or dive. As you can see, we're controlling the rotor disk; the helicopter body is just pulled along for the ride. 
   The purpose of a tail rotor in helicopters is to counteract the torque of the engine and thus maintain a constant heading. If it weren't for a tail rotor (or tail thruster in the case of the Hughes MD500 NOTAR), the body of a helicopter would spin the opposite direction of the main blades because the engine is mounted within that body. So to "turn" a helicopter in a hover, the pilot uses the foot pedals that change the pitch on the tail rotor.
   With the clockwise rotation of the 162F main rotors, a left pedal push results in a lessening of pitch in the tail rotor, allowing torque to yaw the nose of the aircraft to the left. A hover turn (yaw) to the right requires more tail rotor pitch than for the steady-heading hover. 
   In forward flight, the pitch of the tail rotor is virtually neutral and is varied slightly simply to maintain a straight forward heading. All turning in forward flight is accomplished by tilting the main rotor with the cyclic. In theory, the tailboom in forward flight above approximately 20 mph functions like a windcock and thus tail rotor pitch isn't needed to keep the ship straight. The large disc resulting from the rotating tail rotor along with the vertical stabilizer also aids in this windcock effect. 
   The collective control is held with the pilot's left hand and adjusts pitch in the main rotor blades, directly controlling the lift and therefore the altitude of the helicopter. In forward flight, it also works with the cyclic to maintain forward airspeed.
 

  On the end of the collective control stick is the twisting throttle grip that controls engine power. The engine turns the main blades, and power control is used to maintain a constant rotor rpm. In helicopters, a constant rotor rpm is maintained with speed and altitude of the machine governed by the amount of pitch in the blades and the amount of tilt in the main rotor disk. In the 162F, 100% main rotor speed is 520 rpm.  
   All four of these functions work together in flying a helicopter, and an adjustment in any one of them usually requires another compensating adjustment in the other controls. You can see why you hear people referring to flying a helicopter as a real balancing act. Flying one is about like rubbing your stomach, patting your head, and blowing bubbles all at the same time.  
   Arms and both legs work together simultaneously, and unless you have a very sophisticated machine with autopilot functions, there's not much time to let go of a heli's controls. There's no such thing as being in cruise or autopilot with your nose in a chart! 
   Sure, if you have a collective friction control and a throttle that will stay where it's left and not slowly roll off, you can let go to change transponder or radio frequencies and such. Also, other more expensive rotorcraft have a governor on the throttle that will maintain a constant rotor rpm by adjusting the throttle automatically when main rotor blade pitch is increased or decreased.
   In the 162F, however, a good governor setup would cost just about as much as our entire helicopter kit, so we don't have one! Built into our system, however, is a throttle correlation setup that will mechanically increase throttle when the collective is raised and vice versa. Depending on how the builder sets it up, however, you still have to watch both your rotor and engine tachs and compensate with throttle.
   If this all sounds pretty complicated, it is! But just like when learning to ride a bike for the first time, or any other hand-eye coordination skill, once you get it, you've got it! After a few hours of hovering, your basic helicopter hovering and flying skills become instinct and it's not so difficult.

The Learning Curve    
   So how do you know if you can handle being a chopper pilot? You'd probably pick it up more easily if you were a girl. After doing a little research both in conversations with instructors and trying it myself, I've found that women can usually learn to fly helicopters more easily than men. Why? I think it's because flying the cyclic takes a delicate conservative touch, and most men tend to over compensate and fight it, whereas women generally tend to be a little more gentle and will let the helicopter fly. Neither my wife nor my 64-year-old mother had ever been at the controls of any aircraft, but when I gave each of them a mini lesson in the Exec 90 using the dual controls, within a few minutes both of them could keep the machine level and in a pretty good hover! Within less than 10 minutes in her "lesson," my wife even added the collective and pedals!
 

  It's tough to say what is the most critical piece of hardware on a helicopter, but I think the controls are pretty high on the chart. It always used to make me a little nervous knowing that when I made up the control weldments for one of the helicopters, each little bracket I cut out, bent and welded onto the control assembly could mean death if it broke off in flight. I could weld pretty well and never had any trouble or scares, but it still bugged me.
    So there was great appreciation on my part when RotorWay started supplying all new kits with completed control weldments with nothing left to do but trim cutting or filing, painting and then the adding of the rest of the hardware.

Let's Build   
   You can see easily in the pictures the simplicity of some of the control setups. With the cyclic, as with the pedal and collective weldments, the assemblies must be carefully trimmed on one or both ends of the pipe to fit within the existing bracketry on the airframe. When trimming, don't forget to allow for the white nylon end plugs and the aluminum bushings. The assembly must fit down between the airframe's brackets, and quarter-inch bolts are then coated with Loc-Tite and inserted through these brackets and screwed into the aluminum bushings.
   The bolt is safety wired to the airframe bracket, and the aluminum plugs are pop-riveted there as well. Simply safety wiring the bolt is not enough! The aluminum bushings must be riveted to the frame because of the potential problem of a ratchet effect taking place between the nylon and the steel pipe. If for some reason the nylon plug and the aluminum bushing had too much friction and froze together, turning simultaneously, the two could rotate together within the steel crosstube weldment and ratchet the bolt, pushing it right out of the bracket hole with the safety wire having no effect! With enough ratchet turns, the entire assembly would disengage from its mounted position on the airframe, leaving the pilot with little or no authority over that particular control surface. Not good! Riveting the aluminum bushing to the frame totally eliminates this possibility. The pictures will clarify how things are assembled to avoid this boo-boo.
   The solution is to build the controls according to the instructions. But you also want very smooth movements in your controls, and with a little extra effort on assembly, you can achieve this too. Once you have the correct length of each weldment trimmed to fit with the plugs and bushings in place, when you tighten both end bolts, the pipe won't want to rotate smoothly. Why? 
   It's because the two mounting brackets prewelded onto the frame by the factory are close to being square to each other, but the pairs are rarely lined up exactly; cooling of the heated metal after welding is enough to throw them slightly out of alignment. You won't find this tip in the building plans, but the best way I've found to line up the brackets is to put only one nylon bushing and aluminum plug in at a time. Mount the aluminum bushing to the frame with its bolt, then insert the pipe over the bushing with the nylon plug inserted as well. Rotate the weldment back and forth while lining it up with the opposite mounting hole. 
   You'll notice that there's a "sweet spot" where the nylon plug rotates more freely on the aluminum. But it usually won't be where the hole on the opposite side lines up. If this is true, simply use the pipe as a lever with the plug and bushing still together, slightly bending the bracket toward the direction that the pipe needs to go to line the sweet spot up with the opposite side's hole. Keep checking and pulling until it lines up. Initially, a perfect line-up should only be a fraction of an inch away. If it's more, contact the factory!}
   The next step is to take the aluminum bushing out and do the same thing on the opposite side. When you assemble the pipe into the frame, be sure to grease all mating surfaces, then torque down both mounting bolts, and the weldment should rotate very freely. You'll initially want your controls as loose as possible, with friction coming only from the cables and other hardware.

Dual Controls   
   The 162F kit comes with dual controls, and the plans assume that's how you want your machine set up. If you don't want a set of controls on the passenger side (the right seat), the passenger collective and cyclic sticks can be removed easily during the preflight. Unless you're already a proficient rotorwing pilot, I recommend building the dual controls. Even if you don't receive instruction in your own helicopter, it's always nice to have someone who already knows how to fly a RotorWay sitting with you on the first run-ups to help with the setup and to tweak the new rotor system. It's also a lot safer to have a more proficient hand on the cyclic in your first few hover attempts! (The guy in the other seat should be a licensed rotorwing instructor current in type. 
  Also, once you're qualified and rated, but there's nothing more fun than getting some cocky son-of-a-youknowwhat who thinks he can fly anything, putting him in the passenger seat, and letting him try to hover a helicopter for the first time. You'll have to grab it back every 2 seconds, but it sure is nice to humble those so and so's! But don't try this unless you really know what you're doing! A dynamic rollover can happen within a second or two of bad maneuvering!

Back to Building   
   As for the cyclic control construction, two cast aluminum cyclic clevises are mounted in nylon bushings onto the cyclic weldment cross shaft and are mated with a cross member aluminum tube and rod ends to actuate matching lateral control movements. Lateral cyclic travel is set and adjusted with bolts that are mounted on the sides of each clevis, and fore and aft limit is regulated by bolts mounted to the weldment that contacts brackets on the pilot side of the airframe. Look at the pictures!  
   The actual cyclic sticks come from the factory prebent but as raw steel. They need to be cut to personal-preference length, and you must drill a 3/16-inch hole in the cyclic clevis. On the pilot's cyclic, you'll also have to cut an oblong hole for the starter wires to run through. Make the hole longer if you plan on putting other control buttons or switches in the cyclic.
   You can either paint the cyclic sticks or have them chromed. The stick grips are later glued on after all electrical wiring is completed. You also have to cut out a small aluminum cover backplate for the handle that is glued on with a cyanoacrolate adhesive or epoxy or rubber cement. (You might want to remove the plate later.) Rubber boots are attached to the fiberglass cyclic access panels later in assembly, with the cyclic sticks pushed down through them. 
   Bolted to the cyclic weldment are the two lateral cyclic cables that are actuated by the pilot's cyclic. Fore and aft cables are mounted to airframe bracketry and attach to the weldment on the passenger side. Both sets of cables attach via aluminum push/pull control cable Tees and rod ends that run up and behind the seatback and directly to the swashplate. As two pairs of cyclic cables, they are somewhat redundant and act as a very efficient and safe direct hookup of the cyclic controls.
   As mentioned before, the switch for the engine start button is mounted in the pilot's cyclic handle. You have to drill and counterbore a hole in the handle and mount the button. RotorWay now supplies a flip-up safety cover for the start button to discourage accidental starter engagement, but I don't like the cover because it could cost a second or two if I need a quick engine start during a power-off autorotation. To each builder his own on this one.

Wiring the Cyclic   
   All cyclic handle wiring runs from the airframe into the cyclic stick and up through and into the handle. If you'll notice on the picture of mine, there two extra switches and one extra button. The small button is the Engine Start, and the big red button is Push to Talk. The blue toggles are momentary-on switches used for the radio.
   I'll get more into the radio and electronics stuff in a later article, but I highly recommend getting a radio that will hold frequencies in memory that can be scanned via a remote toggle switch, and make sure you can flip-flop between standby and active frequencies with a remote toggle as well.
   Why? Let's say you're sitting at an airport in a hover ready to depart and you have to switch frequencies from Ground Control to Tower or you want to check ATIS quickly. Or you're on approach and you have to change frequencies. Do you really want to let go of the controls and fiddle with a radio while looking out for traffic and fighting wandering controls? I'd rather have the radio memorize the frequencies I'll need and not let go of the controls.

Collective Comments   
   Just like the cyclic control, the collective weldment is mounted to the airframe with aluminum bushings and nylon plugs. The throttle assembly functions inside the collective weldment and is best understood by looking at the pictures. Collective/throttle correlation is mechanical, and if set up correctly can make your flying a lot easier. 
   As the collective handle is raised and main blade pitch increases to maintain a constant rotor rpm, more throttle must be added. Engine and rotor tachs are in one gauge but have separate needles to monitor both. With a governor, this correlation is accomplished automatically. With our setup, however, within the collective and throttle setup we add power mechanically. It's not exact, but it's much easier than having to roll on or roll off the exact amount of throttle each time you adjust pitch. So set up the correlation as close as possible to what the RotorWay manual calls for, and your piloting tasks will be greatly alleviated. A new throttle cable has been implemented in the kit and should improve setup. 

   The passenger collective is easily and quickly removable, being held in place by only one bolt and nut. You'll notice in the pictures that upon removal, all that's left is a stub from the collective weldment. On both the pilot's and passenger's collective, over the throttle handle is slid a motorcycle-type grip. I used an airhose to blow pressure into the rubber grip to expand it like a balloon to slip over the handle more easily. It's next to impossible to slip it over the handle without the air!  
   The collective weldment comes with an aluminum casting already mounted to its tube, but it must be adjusted to exact angles and location and then bolted in place. Bolted to this casting is one end of an aluminum tube, referred to as the collective rod. This tube has aluminum end plugs with rod ends, and it runs from the casting on the collective weldment up to the collective actuator arm on the rotor hub. A large spring is mounted at this same connection point on the rotor hub and then to the airframe, helping ease collective pressure. 

Footwork   

   Next comes the pedal or directional control assembly. It too is a horizontally mounted tube, but it supports four aluminum pedal  castings: two pinned to the moving shaft, with the others simply slipping onto the shaft in an opposite direction. Each pair of pedals is connected to its mate via scissor beam aluminum cutouts mounted in aluminum pivot plugs and nylon pivot bushings.
  On the pilot side, the pedals move one end of the scissor beam, while the opposite end is connected to the very long directional control cable. The cable is mounted to its own bracket on the airframe and runs the length of the ship: across the bottom of the tub, up along the airframe, and all the way down the inside of the tailboom to the tailrotor pitch actuating arm. We'll get to the tail rotor in an issue or two.  
   Take extra time on the construction and assembly of the pedal control. It takes patience to get it to operate smoothly and easily, but the more buttery it is, the more smoothly you'll be able to control your ship. Grease is a good thing, but we'll try to make it smooth before adding the grease.
   How loose should the pedals be? Before you attach the control cable or put the floor pan on top, the pedals should almost fall with a clunk when you nudge them to their extremes. Plenty of friction and resistance will occur when you hook up the control cable and the tail rotor itself.

Who's Driving?   
   Now we come to the drive train. The engine on our ship powers only one item on the entire aircraft: the secondary unit. The secondary is a mystical device assembled by RotorWay, and few mortals have seen the inside of one. It's the all-encompassing unit that drives literally everything on the 162F. It is mounted mid-height in the airframe, behind the center of gravity, turns clockwise as seen from the top, and is driven by four double V belts that come off the engine's smaller main drive pulley.
   On the very top of the secondary is a trilevel sprocket that turns the main drive chain. This chain turns within a sealed fiberglass oil bath and drives the large aluminum main drive sprocket that is bolted to the base of the main rotor shaft. This shaft is part of the main rotor hub to which the main blades are attached. (Shouldn't there be a song explaining how all this stuff is hooked together?)  
   The secondary unit is simply a large, one-way (sprag) clutch driven by the engine that allows the main blades, chain and secondary sprocket to free-wheel when not powered by the engine.
   Also powered by the secondary via more pulleys and V belts are the upper and lower fan drives, the water pump, the alternator, and the tail rotor drive. At this point in construction, the builder mounts the secondary unit per the instructions, blue prints and video tape. 
   You should look at all instructions regarding this installation as it's a really critical step. The secondary must be mounted exactly per specs to achieve all correct angles and dimensions. Done wrong, the life of the drive train could be significantly shortened. Or worse, the secondary or accompanying components could be catastrophically damaged during operation.    
    During final installation of the secondary unit, I made sure to include the main drive belts and upper fan drive belt, as you can't put them on afterward! The secondary sprocket is now temporarily mounted on its shaft with plenty of anti-seize compound. 

Another Biggie   
   Now comes another critical installation: the main drive sprocket. It is a large aluminum casting and is another one of those aircraft parts manufactured in house by RotorWay that could double as a piece of museum-quality aviation art. Pictures don't do it justice. I think I might order one to hang in my living room.
   The builder must mate it to the sprocket hub, and this is done by drilling four D-size holes in appropriate places through the sprocket and the hub. These are just about the most critical holes drilled by the builder in this entire kit, and I wish RotorWay would start doing this step in-house. Each of these holes must be drilled exactly 90” to the surface and must be exactly straight and D size only, not 1/4 inch! Use a big, accurate drill press!  
   The four 1/4-inch bolts have to tap into place as a snug fit: no looseness here! These bolts are placed strategically and engineered as shear bolts in the unlikely event the secondary unit or chain freezes up. If a freeze-up did happen, the main blades should have enough inertia to shear the four bolts at once, allowing continued rotation, and enabling the pilot to land the aircraft in an autorotation. If the four holes are incorrectly drilled either at an angle or in the wrong place, the bolts could shear prematurely. There are centerpunch marks already in the main drive sprocket, so you'll easily see where to drill. Just make sure you go through the material straight!  
   The building plans are now easily understood regarding how to adjust the main shaft and secondary for placement, angles and chain tension. Spend extra time and get all this stuff exact. The heights of the sprockets in relation to the square drive tubes as well as to each other are really critical, as is chain tension.

Chain Challenge   
   And how do you adjust chain tension? You might have to get creative. Shims are placed between the secondary's upper and lower bearing housings and the frame to adjust the tension. RotorWay supplies a few thicknesses of shim material, but even five thousandths of an inch can make a difference. You say you don't have any shim material that's 0.005 inch thick? Yes you do. Use an aluminum Coke can. And if you adjust the chain tension to exactly what it's supposed to be now, you'll have a lot less messy maintenance to do later.
 

   Within a few hours the chain will loosen slightly, and a 0.010-inch shim placed behind the lower main shaft bearing housing will be enough to tension it back out to specs and keep it correct for the rest of its life.     I used care not to overtension the chain. This can prematurely wear out bearings and, according to RotorWay, it can also cause major stress on the secondary shaft, resulting in bad things that could really ruin your afternoon.
   After getting all the angles and placements correct when installing the secondary, the main shaft, and the main drive chain, you can now install the secondary unit permanently by bolting the cast aluminum upper secondary mount to the airframe's rear square drive mount tubes, as well as using the lock ring and some Loc-Tite on the secondary's lower bearing that is bolted to the lower square drive tubes within its mounting flange. Be sure to lock all lock rings on the ship with clockwise rotation, and (one more time) don't forget to include the V belts!    

   Next issue we'll install the engine, the idler pulley, the drive peripherals coming off the secondary plus the oil bath, fan shroud and oil system.

FOR MORE INFORMATION on the RotorWay International kit helicopter, contact the company at 4140 W. Mercury Way, Chandler, AZ 85226; call 602/961-1001; fax 602/961-1514; www.rotorway.com.


 

 

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