Wing Portion of the Aileron Actuation System

The Concept of the Aileron System
The aileron control system has no push rods in it other than a short one that transfers motion from the bellcrank in the wings to the aileron itself. Otherwise everything happens as part of a “closed loop” cable system. By closed loop we mean there is a gigantic loop of cable that essentially goes from one wing to the other with the control stick spliced into one leg of it and imparting motion. The cables, which are all 1/8” (7 x 19 galvanized MIL-DTL-83420) attach to the end of the control stick push rods, run up inside the lift strut into the wing, around a pulley at the top of the strut that routes the cable outboard parallel to the wing span, then around the last pulley and back to the aileron bellcrank. The loop continues inboard toward the fuselage where it continues all the way across the inside top of the cabin and into the other wing where it makes a similar “U” turn. The cables are joined in the top of the fuselage by a turnbuckle that allows adjustment of the tension.
Fine tuning of the aileron neutral position is accomplished by adjusting the push rod that connects the bell crank to the aileron. It’s an extremely simple system and easy to install and maintain.
If you haven’t already, familiarize yourself with the general cable section of the manual.
Install the Bellcrank
The aileron bellcrank pivots on a bolt that goes through the fore-and-aft steel support tube that’s bolted between the two spars. This bolt goes through two KP bearings, one inserted into the top of the bellcrank and one that goes into the bottom. These bearings are included with the latest kits. At one time they were part of the Wicks hardware kit. They are meant to be inserted into the pivot tube of the bellcrank where they rest against the lip formed by a short piece of tubing that’s inside the pivot tube. You may have to sand a little paint out of the inside of the tube to get them to slip in. They should have a snug fit, as they aren’t supposed to turn in the bellcrank.
The bellcrank pivots in such a way that one of its arms goes through a hole in the rib next to it.
In a few early kits there was a little interference there so you may have to open up the odd-shaped hole right there. If you do trim it, take as little away as possible and make sure the edges are filed and sanded smooth. At the same time, make absolutely certain there is plenty of clearance: the last thing you need is the aileron bellcrank hanging up. The pivot bolts for the bellcrank and those attaching the cables to it, are drilled bolts using castellated nuts and cotter pins.
Routing the Cables
When routing the aileron cables through the wing you always have to be aware of any clearance issues with structure or components. Where the cable comes off the front pulley and goes down inside the lift strut, it’s possible you might have to file a little off of the edge of the strut to get clearance. This isn’t critical other than making sure the bottom of any notch you cut is well rounded and smooth. Sand it with 320 grit paper and slightly round the edges to remove stress risers. Most builders glue a thin plastic rub block on the upper end of the strut where the cable passes over, since the relatively low cable tension in the aileron system isn’t always sufficient to prevent rubbing in this area. The hole in the wing skin is approximately two inches aft of the rear steel strap strut attach and 5/8’ outboard of the main strut/wing attach bolt. Again, smooth the edges. When passing through ribs, plastic snap bushings can provide an extra layer of protection, just be sure that the cable doesn’t change direction as it passes through the bushing, making it a rubbing point.
Watch for Cable Clearance
Where the cables come off the bellcrank and go down the wing and toward the fuselage early kits have a number of places where ribs need clearance notches cut or holes elongated. Specifically, on ribs #7 and 8 the holes may need to be ovaled out. You want the cable to pass 1/4” to 3/8” above the flap mechanism support tube that runs between the two spars. Any enlargement of the holes should leave at least 1/4” between the hole and the large lightening hole. If it is closer than that, make the hole a “slot” off the big lightening hole. Again, make it a smooth notch that’s shaped like a finger tip.
Consult the aileron cables section for more detail about cable routing.

This image shows the bellcrank. Note that the pushrod end pivot bolt uses a wide AN970 washer to ensure captivity even if the bearing fails.

A view from the other direction:

This image shows how the cable exits the skin near the top end of the strut.


Cable Guard Detail

The Wing Portion of the Flap System

Understand the Concept
Before doing anything on the flaps system pull out drawings No. 12 and No. 14. They will give you a good familiarity of how the different parts relate to one another and how they work. Also, study the photos in this section. They will clarify any questions. The flap system is quite simple in that it is nothing but a torque tube coming in from the root with an actuating arm at each end. At the root it is attached to a cable and at the other end a push rod is attached to the middle flap hinge and pushes the flap out. The flaps are held in the up position by the long springs included in the later kits or available from Bearhawk Aircraft for the older kits.
The procedures we’ll use to install the system include:
1. Install torque tube
2. Temporarily slide actuating arms into position on the torque tube
3. Position and drill outboard flap arm.
4. Install inboard flap lever, but don’t drill.
5. Install springs
Install Torque Tube
The torque tube slides through the steel stand-off bushing at the root and through a similar bearing stand-off at the mid-wing cross member. Before sliding the outboard end into the bearing, note that one of the outboard arms has to be slid in place first (see photo).
Because both the torque tube and the bearings have been painted, it’s a good idea to remove the paint from both the inside of the bearings and the area on the torque tube where the bearings will
ride. This not only makes it much easier to slide the tube into position but greasing the metal-to-metal contact makes for much smoother operation.
Drilling the Outboard Actuating Arms
Each torque tube has three actuating arms: one at the root (called the “lever”), and two outboard arms that work together to clamp the pushrod between them (see pictures). A hole needs to be drilled through the base of the arms and through the torque tube to accept AN3 (3/16” bolt) to stop the arms from rotating on the torque tube. Latest kits have the inboard arm welded in place. If this is the case on your kit, the sequence will be slightly different: don’t drill the outboard arms until the wings are in final position and you are able to verify the critical positioning of the inboard arm.
Many planes are flying with holes that were drilled to 3/16, though to give these bolts the tightest fit, you could instead drill with an 11/64” and ream to size to eliminate any possibility of slop in the holes.
For Kits without welded inboard arms:
On the outboard arms, first bolt the short flap push rod between them to hold them in alignment. Then clamp the top end of the push rod where it bolts to the arms down to the crossmember tube to keep it from moving while drilling it. With the outboard actuating arms still clamped against the fore and aft tubing crossmember, position the inboard arm as per Drawing No. 14. The root/inboard actuating levers have to be mounted at a specific angle on the torque tube to give the flap cables the most efficient angle for pulling, as depicted on the plans.
Because there is limited room between the fuselage and the wing root, it is essential that the inboard lever be centered in that gap. For that reason, don’t drill the hole through the inboard lever and torque tube until after the wings are on the airplane to ensure no interference occurs. Plans page 14 depicts the inboard lever in the “flaps up” position.
For all Kits:
When it is time to drill the arms through the tubes, center punch where you’ll drill the hole in the arms. Then drill one arm with a fresh 3/16” bit (make it fresh, so it cuts cleanly and easily). Then put a bolt in place to keep it lined up. Drill one outboard arm first, then install the pushrod bolt and tighten the nut. This will hold the other arm in place to ensure that it doesn’t become misaligned while drilling. If you want, you can install the flap springs now, which will help hold everything under tension and keep the arms and pushrod from moving. After drilling, disassemble and debur the holes. before final reassembly.
The Flap Actuating Cable
Later, after you put the wings back on the airplane semi-permanently and position the actuating arms and drill the mount bolt, you’re ready to attach the actuating cable. The flap arm was delivered with a 3/16” hole (AN3) hole, however you use a 1/4” shackle (AN115-32) rather than a 3/16” shackle (AN115-21) to give a longer distance at the arm, which increases cable clearance from the structure.
A 3/16” (AN3) bolt will be sloppy in the shackle so bush it down with short pieces of 1/4 x .028” tubing. If you can’t find that size tubing, contact Bearhawk Aircraft. Later kits include the bushings, some earlier kits have six inches of the tubing supplied, and you can cut your own bushings from that supply.

This photo shows the outer arms, along with the aileron cable passing by spanwise. Paint must be removed from inside the arms and off the torque tube to ease getting the actuating arms on the tube. Note how the pushrod is sandwiched between two actuating arms. Ensure that the aileron cable is routed above (toward the top of the airplane) the flap pushrod, which is not clear in this picture.

These two photos show the inboard end of the flap torque tube, along with the aileron cable.

Creating the Aileron Cables

Now is a good time to revisit the General Nicopress Section.
The aileron cables pose a small challenge when it comes to the sequence of things. You’ll want to do enough of this step to ensure that you have good clearance before you rivet the wing skin. But you won’t be able to make the final runs until the wings are on the fuselage. If you have not yet mounted your wings, it would be wise to make temporary runs with control cable or other 1/8″ diameter material to ensure that there is not any interference, especially on the aft cable route.
The first cable to create will run from the aileron bellcrank in the wing to the control stick. It doesn’t matter which side of the airplane you start with first, they are the same. When connecting the aileron cables to the stick assembly, first don’t forget to use four little 1/4” x 3/16″ bushings as shown in the plans. These are included with later kits. If you are building from an earlier kit, make these from the short piece of tubing provided.
Start by fixing the stick in a vertical position so it can’t move, and fix the ailerons in a neutral position. Crimp the outboard end of a piece of 1/8″ galvanized cable onto a turnbuckle cable eye (AN170) with a thimble (AN100-4), and install it in the aileron bellcrank turnbuckle body. This turnbuckle assembly is the AN130-32S. Attach the other end of that turnbuckle to the aileron bellcrank with an AN161 Fork. We will eventually tension the aileron cables to around 20-25 pounds, which is not much. This will not require very large adjustments of the turnbuckle. The initial setup should be that no more than three threads on the cable end are to be exposed when you start to tension the turnbuckle. Final tension on the cable should be achieved when no more than the four end threads of the barrel are exposed.
Route the other end of that cable from the aileron bellcrank turnbuckle through the pulley in the front of that bay, then through the pulley just outboard of the wing strut. Continue routing down the wing strut, through the pulley on the fuselage, and to the control stick. Install a nicopress sleeve, then a thimble, then route the cable back through the sleeve. Attach the thimble end to the control stick using an AN115-21 cable shackle, AN3 bolt, and the small steel bushing. This bushing allows us to tighten the bolt fully, which means an elastic stop nut is suitable. It is also acceptable to omit the shackle such that the cable thimble will pivot on the outside of the fixed bushing. Pull the cable reasonably snug and use a temporary clamp like a split nut (as describe din the general section) to hold the cable in place while you go back and visually verify that the the cable is routed correctly. Ensure that it does not have any kinks or snags, and that it has not slipped out of the groove of the pulley. Also, take note of where the cable passes the flap pushrod. When the flaps are lowered, the pushrod moves up vertically, and you’ll want to ensure clearance in both extremes. If all is well, remove the bolt from the control stick and crimp the nicopress.
Repeat this process for the other side, ensuring that the starting point for the turnbuckles is the same for both sides.
Connection in the Cabin Roof
The third aileron cable runs from one bellcrank to another, passing across the top of the cabin, just in front of the rear spar. This will actually be two cables, connected by a turnbuckle inside the cabin (but not in the middle). In the 4-Place, notice that the aileron cable will pass very close to the elevator trim cable passing perpendicularly. Plan to place the turnbuckle offset to provide extra clearance. If it looks like the cables might rub, you can install a short length of nylaflow tubing on the aileron cable, something easier to do now rather than once the cable is already made. Having the turnbuckle in the middle further reduces clearance and precludes using the nylaflow bushing.
Crimp a thimble onto the outer end and attach it to the bellcrank with a shackle and AN3 hardware. Route the cable inboard to the fairlead at the wing root. Apply enough tension to the cable to verify that it clears all of the ribs along the way. It may be necessary to make a little extra room for the cable with a round file. Be aware of stress risers and if you’ll need to remove very much material, it would be wise to consult Bearhawk Aircraft to make sure everything is set up correctly before cutting.
Before you crimp the inboard end on the first cable, install the terminating hardware and a temporary clamp at the turnbuckle (AN140-22S). Create the second cable, remembering to offset the turnbuckle if elevator trim cable interference is a problem. At this point everything should be crimped except for the inner two ends of the cable. Make one last visual inspection of the whole loop to ensure that everything is correct, then crimp those two ends.

Aileron Counterbalance Tube


This can be done at any time after the ailerons are hinged to the wings. To balance the ailerons we’re going to pop rivet an aluminum tube weighted with lead. In the early days of the Bearhawk 4-Place, the plans called for a 3/4” O.D. thin wall aluminum tube. This tube diameter was later changed to 1” to improve the flight characteristics of the ailerons. If your ailerons were built to accommodate a ¾” tube, realize that you’ll really need to pack the entire tube full of lead in order to achieve the correct balance. If you are building with ailerons intended for the 1” tube, you will have plenty of air left in the tube at the balance point. Look at the nose ribs of the ailerons to see the hole where the tube goes. It will be positioned spanwise between the two hinges, but there are holes in the rest of the ribs so that you can slide the tube in. Most hardware stores will carry a 6061 aluminum tube with the right dimensions. You’ll want to put 5 pounds, 4 ounces of lead in that tube. You can add a little extra with plans to drill it out before covering, if you prefer.
Although you can go through an entire balancing process in which you suspend the aileron by thread and estimate the fabric and paint weight and then determine how much lead you’ll need (see Russ Erb’s CD), the range will always be between five pounds and five pounds, four ounces. Since overbalancing is better than under balancing, use five pounds four ounces as the target.
Pouring Lead (small tube only)
If you are building with a ¾” tube, the best method is probably to pour molten lead to fill the tube. The lead will cool as it is poured into the tube, which will introduce voids. Mitigate this by having a helper preheat the aluminum tube with a propane torch. This process is much more dangerous than it seems! Use a face shield and respirator, do it out doors, wear welding gloves and make sure no moisture is present as it will turn to steam and blow molten lead all around. Stand the tube up and either make a wood plug for the end or stick it slightly into the ground to seal it. Support the tube with some sort of structure up high, because once you start adding lead it will want to fall over and that will likely set the place on fire. Make sure the can or ladle you’re using has a narrow spout or make a funnel from aluminum flashing.

Because the tube is so long and you want the lead to keep flowing, rather than cool on the way down, carefully warm up the tube with your torch. Remember, it’s aluminum and easy to melt, so don’t get it too hot. Because there is no airspace in poured lead, there will be too much in the tube, so be prepared to drill some out. When the tube is full, slide it in place and pop rivet it with stainless rivets.
Using Lead Birdshot (preferred method for the larger tube)
If your plane uses the larger tube, you won’t want to mess with hot lead and the corresponding safety concerns. Instead, fill the tube with bird shot. Go down to your local gun store that sells reloading supplies and get the smallest lead shot they have. You want nothing bigger than 8 1/2 (the bigger the number the smaller the shot) and finer is better as there will be less air space in it. If you can find number 12 shot, great! make sure it is lead because some places sell steel shot, which isn’t heavy enough.
Although some builders have made up a paste of lead and epoxy, that is difficult to get down the tube and the epoxy takes up space. Instead, we’ll only use the paste on the ends, since the shot itself pours in like sand. First, rough up the inside of both ends of the tube with coarse abrasive, 60 grit or so, to give an epoxy plug something to hang on to later. Tape one end closed. Fill the tube with the lead shot up to about 3/4” from the end. Make sure to lightly pound the tube against the ground, so the shot settles into place. Then, make up a slurry of epoxy (JB Weld is good) and shot that is mostly lead shot (for weight) and fill the remaining space with it as a plug.
Before plugging up the other end, weigh the tube. It should be at least 5.0 pounds and a little heavier is better. Turn the tube over and remove a little shot to give enough room to form another epoxy/shot plug in place and you’re finished with this process Now, slide it in place.


Lead Wool
Yet another way of getting weight in there is stuffing the tube full of lead wool. This looks like steel wool, but it is lead and is available from McMaster-Carr. The method of installation involves nothing more than forming plugs that look like cocktail wienies out of the wool, dropping them in and compacting them with a steel rod. Then an epoxy plug is poured in the end the same as with the lead shot.
Lead wool “wienies” are formed really easily and tamped down are nearly solid.

Installing the Flap system


Understanding the System
The flap control system uses a handle to pull on a cable, which, in turn, pulls the flaps down. Springs in the wings hold the flaps up, when sitting on the ground. The primary flight controls are pull-pull systems, the flaps are pull only. The flap setting is held by notches in a quadrant on the cabin floor.
Assembling the Flap Handle
Study the assembly shown on plans page 28. Note that a spring inside the handle pushes a pin into notches in the notched quadrant. The spring is a type commonly available at hardware stores. Buy one that is quite a bit too long because you can fine tune the button’s resistance by cutting coils off the spring.
The Quadrant
The half-moon shaped bracket with the notches in it is attached at the top and the bottom with bolts. It slides through a slot cut in the handle. Be sure to install the spring before assembling these two parts.
Routing the Cable
The cable that activates the flap runs aft through the far right (looking forward) pulley of the three pulleys underneath the fuselage, on the Bearhawk 4-place (on the Bearhawk Five, the cable runs in the far left pulley). The cable continues to the back of the baggage compartment where it turns upward through the pulley located there. As it turns up parallel to the back of the baggage compartment, it attaches to the bottom point of a triangular piece of 1/8” steel (supplied). A turnbuckle is attached to each of the upper corners with a cable going to pulleys located in the upper, rear corners of the baggage compartment. Make sure you are using forked turnbuckles that go on each side of that triangular plate. The vertical position of this triangle plate is not trivial, and moving the plate may lead to undesirable flap rigging. This is an area where it’s especially important to stick to the plans. When the flaps are fully down, the 1/8″ steel triangle should be as close as possible to the floor-level pulley.
If you are working on these parts without the wings attached to the fuselage, you can run your cables through the upper pulleys, but can proceed no further until installing the wings. Leave the cables long enough that you can trim them and install thimbles when hooking up to the flap actuation arms. Run them forward to the rear spar, add twelve inches, trim and then coil them up and tape them out of the way until you’re ready to work with them.
When it comes time to set up and adjust the flaps, start by installing the return springs in the wings. The return springs are an important part of that assembly because they provide the tension necessary to pull the cable system tight so you can see if everything is adjusted properly.
Connecting the Cable at the Wing
Once the wings are on, and the flaps are on, it is time to drill the inboard arms of the flap torque tubes. At this end of the cable farthest from the flap handle, the geometry of the lever on the inboard side of the flap torque tube is significant. The drawing on the plans shows the angle of the flap lever when the flap is all the way up. You can measure the angle of the lever shown in the drawing in relation to the bottom wing skin. In this area the main thing to watch out for is interference of the flap cable or lever with the wing rear spar plates. It is a tight fit. This is the place to use larger (1/4”) cable shackles. Sometimes this alone will solve the problem and eliminate any interference. The long flap torque tube can also be moved inboard or outboard a little (before drilling the flap arms), but the cable alignment in the closest pulley must also be taken into consideration.
A few builders have used two little strips of .062 steel to connect the cable to the flap lever when interference was a problem. Two little strips of 4130 of 3/8” – 1/2” wide x 1.5”-2” long. The cable fit into this closest pulley is worth a comment. When the flaps are all the way up – normally the cable will be on one side of the pulley. As the flaps are lowered, the cable centers in the pulley. Then when the flaps are all the way down – the cable is on the OTHER side of the pulley compared to when the flaps are up. This is how Bob designed it and has worked well.

Crimped Control Cables (Nicopress) – General Considerations

Bob specifies control cables for several systems in his designs. The cables are easy to make with the right tools and a little practice. First, be sure to source the right materials. When ordering cable, choose the galvanized variety over stainless, unless you are building a full-time saltwater floatplane. The galvanized cable is stronger, cheaper, and more wear resistant than stainless. If you are using galvanized cable, use either the bare copper sleeves or the zinc-plated sleeves.
Control cable mock-upHere’s a tip to make life easier: stop by your local hardware store and obtain a few bolt-on cable clamps, as shown in the picture to the right. As you are mocking up your cables for final size, use these clamps temporarily to allow for adjustment, since Nicopress crimps are permanent. Obviously, you’d never want to put such an arrangement into service- use the clamps only during construction. They will hold the cable just where it needs to be until you make the first crimp. Some builders have also used locking pliers like Vice Grips for this purpose.
Consult AC 43.13-1B chapter 7 for details about making a cable that will deliver the intended strength. Follow the general Nicopress crimping instructions from any number of sources (Bingelis, Beartracks, EAA Hints for Homebuilders), or even better, stop by the workshop area at Airventure or Sun-N-Fun for some hands-on training. Keep in mind that the Nicopress supplies from the hardware store may not be up to the standards of the aircraft grade sources. This applies to both consumables and crimping tools. Always check each crimp with a no-go gauge (or measure based on the 43.13 table), and for a cleaner finished product, install a short piece of heat shrink tubing over the cut end so that it doesn’t poke your finger later.
One point we will mention: measure the diameter of your cables to make sure they are what you think they are. On rare occasions, cables have come from a major supplier with the wrong label. They were supposed to be 1/8” and were actually 3/32”. It’s easy to miss that seemingly minor mistake, but in that situation, besides the cable being under strength, Nicopresses look and gauge right, but they will slip almost immediately under load. So, verify your wire diameter and make sure it matches the Nicopress sleeves and vice versa.
Turnbuckles
Turnbuckles are made up of a central body, and threaded ends that are either made with forks for bolting onto something like a bellcrank, or made for cable ends:

Ends are either left hand or right hand threaded. Be careful not to use the wrong one, meaning don’t run a cable through a fork end or a bolt through a cable end.

Pulley Guards
All cables, should have cable guards on the pulleys to ensure that the cable is unable to unseat itself from the pulley, even with a loss of cable tension.
It’s not unheard of for a control or flap cable in an airplane, any airplane, to run off the pulley. For that reason, every pulley in the control/flap system should have a cable guard on it unless, as with the three in the belly of the Bearhawk, the structure stops a cable from walking over the edge of the pulley.
These guards are available from a number of sources including Bearhawk Aircraft.
Cable guards aren’t supposed to turn with the pulley. They are supposed to be fixed. Since they are attached to the pulley by the pivot bolt, they want to pivot too. For that reason, they must be fixed to something that doesn’t move or at least have a tab that contacts structure and stops rotation.

Patrol Flap Inboard Detail

After you have your wings installed on your fuselage with the flaps lowering and installed completely – lower them to the maximum deployed position – 40 degrees. Then use a piece of cardboard material to make a pattern. You want to start on the top forward position of the flap and wrap the cardboard all the way around the trailing edge forward on the flap to more or less the flap spar area.

What you are looking for is 1/8″ to 3/16″ gap between the trailing edge tip of this “extension” and the plexiglass of the side window. At flap full deflection the trailing edge of the flap will be the closest to the plexiglass. So make your cardboard pattern with flaps full down. Make the actual part of .032 2024T3. You attach this .032 aluminum sheet that is wrapped around the trailing edge to the flap with pop rivets. Stainless steel pops would probably be best but aluminum pops would probably be OK also.

Some builders use a flap rib for the inboard edge of this part. You can probably see the rivets. But it is not required. Bob did his Patrol with just the .032 wrapped and no rib on the inboard side. That is also adequate.

Bent Flap Handle

Source: 2016 Q4 Beartracks, Pat Fagan

I was on base leg for landing the other day with 3 notches of flap on when the flaps retracted on their own and the handle banged loudly to the floor. I have had that happen a few other times before with 3 notches if I don’t get the pin fully seated in the flap quadrant. It’s annoying, but no big deal. This time however when I tried to use the flaps the button stuck in the tube rendering the lock pin useless. I went to fix it today and discovered the problem was the flap handle a bent slightly immediately aft of the slot for the quadrant. The bent handle is what caused the inner tube to bind when I pushed the button in. What I find very surprising though is that the handle bent downward, not up like you might expect. After all, any bending moment is applied against the air loads when deploying the flaps so it seems logical that if the tube where to bend (not very likely with that wall thickness over such a short distance) it would bend upward. Perhaps it was a cumulative load from having happened before but still, there isn’t anything for the handle to bang against on the way down and there certainly isn’t any mass at the end of the handle. I straightened the tube (and it took a heck a lot of beating with a plastic mallet) and tapped out the buckle then sleeved the handle to stiffen it.
The handle is the original design, 3/4″ .049 tube. (Builders may note that there was an optional design change to the flap handle, published here in January 2006.) The doublers end just aft of the slot. I sleeved it with a 7/8″ tube that was notched to fit around the doublers which made it a snug enough fit that I could try it out on the plane before welding it on. Now I think I’ll just leave it as is, unwelded.

Note the Different Thicknesses of the Aileron and Flap Gussets

Source: 2000 Beartracks, Bob Barrows

Many builders are fabricating parts and not assembling the component for several months for one reason or another (for example: wanting to prime the piece before assemble or not wanting the component to take up space). This can lead to some confusion if individual pieces look similar like the aileron hinge gussets on drawing #10.

Note that two are .032 thick and two are .025 thick. The .032 parts must be placed in the proper location as that is the location of the aileron control horn. The flaps are similar in construction.

Be aware of this when storing parts for later assembly.