Installing the Elevator Halves and Rudder

Where the hinges slide forward over the horizontal stab spar, there are little “V”s welded to the rear of the spar. They are meant to support and reinforce the hinge straps. The same “V”s are welded on the vertical stabilizer spar in line with the rudder hinges. You may have to spring the hinge straps on the elevator and rudder apart just a little so they are parallel because the welding will have pulled them in.

Greasing the Tail Surface Hinges:
Don’t grease your hinges until after you are finished covering and painting the parts, but be sure to grease them before you fly. Grease is the preferred lubricant, though you’ll need to devise some way of forcing the grease into the hinge. One method is to use a grease needle. Another is to manually position a Zerk fitting over the hole. Oil is easier to apply, but will need to be regularly replaced, especially in outdoor conditions.

The way the elevators are joined in the middle is pretty obvious but, when bolting them together, leave the outside holes empty for the elevator cables.
Don’t do Anything Final
You’re going to have the tail on and off the airplane several times so there’s no reason to bolt anything tight or install cotter pins yet. It is a good idea to put at least the tail struts on it so the tail is more stable and less likely to be hurt by backing into it or having a visitor sit on it.

Installing the Tailwheel (Leaf Spring)

The Bearhawk 4-Place (pre-Model B) uses a 1.5” wide leaf spring for tailwheel suspension. The Model B kits come with the round tail spring like the Patrol & LSA. But the spring is thicker (1″ vs 7/8″) when compared to the Patrol or LSA.
When installing the tailwheel start with this spring. There is a large bolt in the front, and a “U” clamp (provided by Bearhawk Aircraft) in the back.
Preparing the Tail Spring
The tailwheel assembly is held to the aft end of the spring assembly with a single bolt. On this aft end, it is necessary that the holes in the springs have an oval shape, as to relieve any scissor action that may occur between the two leafs when the spring flexes. See the drawing to the right and verify that your spring has the correct shape hole. If yours was part of a very early kit, the easiest way to open up the holes is with a rotary tool or die grinder and a small grinding stone or carbide bit, although a large chain saw sharpening file works too. Look down through the two leaves and grind the holes into an oval that is about 1/8” bigger, fore and aft, than the hole was, with the original dimension side to side.
Installing the Spring Clamp
The “U” shaped spring clamp will nest around the spring, but just barely lacks touching the mount that’s welded to the tail post. That’s on purpose, so the AN4 bolts on each side can pull the spring up tight. The gap should be no more than .032” and bolt tension will take that up.
A Note About the Bolts
The bolts in this part of the plane are subject to serious loads in operation, so be sure to check them regularly for proper torque. The only way to visually check the bolt condition is to raise the weight off of the tail and give the assembly a wiggle. If you find that the bolts were loose, replace them, since they will likely have been worn by the movement of the parts. Keep a set of spares on hand. When the weight is on the tail, the bolts will appear to be tight whether they are or not.
Attaching the Tailwheel to the Spring
The “Bob” tailwheel body has thick side plates that are welded to the main attachment plate. Ensure that the tailwheel spring is seating fully on the main attachment plate, and not rubbing on a weld bead. This can be done by applying a radius to the top of the top tail spring. If the tail spring is resting on a weld bead and not making full contact with the main adjustment plate, in service the weld bead will wear down and the assembly will become loose. The steering springs to the rudder horn should have just enough tension that there is no slack in the chains.

Builder Bruce Case drew this nice diagram of Bob’s tailwheel design:
Bearhawk Tailwheel Exploded Diagram

Installing 4-Place Floorboards

In recent years, floor boards have been included with quick-build kits. If your kit did not include floorboards, we suggest asking fellow builders for a template. Making the floor boards is like installing linoleum: most of the work is in getting them cut to the right shape, so make them in poster board first.
The front floor boards will be built in sections of .032” 2024-T3 aluminum. The first nestles down between the rudder pedal assembly and the control stick torque tube. A small lip (3/8”-1/2”) is bent up on each end. There will be two floor boards under the pilot/copilot seat area, with a removable strip in the middle to allow for the elevator cable to pass through. Bend a ½” lip down on the inboard side of each of these, and cut clearance for the elevator bellcrank and cables. Another full-width floorboard will cover the area from station D to E, and a final full-width floorboard will cover from E to F.
Attaching the Floor Boards
The mounting tabs for mounting the floor boards run throughout the cabin area and provide plenty of places for attachment. Use either Tinnerman nuts and sheet metal screws, or 8/32 Monadnocks (ACS PN 04-00152) and machine screws. These are a Tinnerman type unit that uses a machine screw rather than a sheet metal screw.
Cable Covers
The rudder cables run above the floor boards, so some builders fabricate small covers that screw to the floor boards or bend a 45 degree edge in the floor boards to hide those from view. This is strictly a cosmetic feature and not a necessity.
Rear Bulkhead
The rear bulkhead is where your ingenuity and taste come into play as it has been done any number of ways. Some builders lace, snap, or Velcro a canvas cover in place, which is light and provides good rear access. Some have been made of aluminum, though there is a higher potential for noise. Some have incorporated a trapezoidal “ski tube” of .020 aluminum that goes some distance back in the fuselage (light articles only, for CG). Some hinge the bottom portion to provide foot room for when they are sleeping in the back. There are any number of ways it can be treated.
When doing the rear bulkhead, regardless of your approach, make sure you provide easy access to the flap cables that run right behind the bulkhead.

4-Place Rudder Pedal Assembly and Rigging

Install the rudder pedals directly to the tube structure. Layout the floor boards so that the pedal assembly doesn’t bolt through them, which makes it much easier to remove the floor boards.
Position the Assembly
Note that the fore/aft location of the rudder pedals is not a matter of builder preference. The geometry depicted on the plans is important to ensure that the rudder pedals are not able to reach an over-center condition with the brake pedals. Before drilling any holes, it is suggested that you collect all of the appropriate parts, including the master cylinders, and, if being used, the right side brake pedals and do a test assembly to see how everything goes together. You can “C” clamp the entire assembly in place before drilling the holes.
Installing the Rudder Pedal Assembly
Pay particular attention to the clearance between the master cylinders and the firewall.
The recommended brake cylinders are Gerdes A-110-4, and rebuilt cylinders are available from Bearhawk Aircraft. If you are planning to install brakes on the right side, contact Bearhawk Aircraft to purchase an additional set. Gerdes made “long shaft” cylinders (A-110-10), but since they are hard to find, most builders use a short shaft Gerdes with a custom clevis fork, provided by Bearhawk Aircraft. More info on master cylinders here.
The hydraulic cylinders are attached to the rear of the curved brake pedal with clevis pins and cotter pins or drilled bolts and castellated nuts, but not tightened down. Do the same where the cylinders attach to the fuselage tabs.
Attaching the Rudder Pedal Assembly
When attaching the curved brake pedals on top of the rudder pedals, use AN4 bolts and castellated nuts with cotter pins. Attach the rudder torque tube assembly to the fuselage tabs with AN3 bolts and AN365 elastic stop nuts.
Running the Rudder Cables
When attaching the rudder cables to the outboard sides of the rudder assembly, we recommend bolting flat 4130 steel (.050) extension straps (provided in later kits) to each pedal using an AN3 bolt that is drilled and secured with a castle nut and a cotter pin. It is left free to rotate. A 1/8” cable with a shackle and thimble (cable secured by Nicopress) is run through the other end of the strap.
Another approach that Bob Barrows uses on his own Bearhawks is to make the tabs in two pieces (.050”) and sandwich the 1/8” cable and thimble between them. A bolt or clevis pin is run through the sandwich and the cable thimble.
Rudder Pedal Return Springs
It’s necessary that return springs be connected to the rudder pedals to maintain tension on the cables and keep the pedals from folding backward toward the pilot. Use springs of 1 inch diameter. Most Ace Hardware stores have a selection of springs that work perfectly.

Unlike the photo above, we now recommend you attach the rudder spring to the front of the .050 steel rudder cable connection strap.
When you make the straps that bolt to the pedals and the rudder cables are attached to, just make them long enough that they extend forward and mount the rudder return springs. In other words, that .050 strap has three holes with the spring catching the front one, the middle one bolts to the rudder pedal and the rear most one has the Nicopressed rudder cable shackle going through it. Bob Barrows does not use turnbuckles on his rudder cables. There isn’t any need for the extra cost, weight, and possible failure point, because the rudder control system is not a closed loop.

Seat Installation in the Bearhawk 4-Place

Front Seat Adjustment Mechanism
As the seats come to you, there is paint inside the tracks that are part of the airframe, both the channels at the rear of the seat and the “ears” at the front. This paint should be sanded out to ensure smooth operation. Also, the “ears” may need a little tweaking to make sure there is sufficient clearance for the seat rails because they sometimes pull in while being welded.
Installing the seats is pretty obvious, but the locking pin mechanism requires a little study. There are two variations of the seat lock mechanism. Early airplanes have an ear welded to a sleeve that clamps to the tubing sticking down under the seat. The later version has the ear welded to the tube under the seat. The ear faces forward.

The T-shaped handle faces forward under the seat and pivots on the ear and presses down on a fender washer bolted to the bottom of the shaft. Put a hardware store spring in between to provide tension. There are two lengths of T-handles, the short one goes under the right seat, to clear the flap mechanism.

This is the way the seat latch looks from the front, when assembled. The short “T” handle goes under the right seat to clear to the flap handle. Drill holes in the track on 1” intervals.

There are several ways you can go about making up the cushion supports, but the way that we find most effective and lightweight is to use the same type of fabric you would use on the exterior of the fuselage. The human form is pretty blunt where it hits the seat, not a lot of sharp corners usually. Plus the cushion is between you and the support platform. For that reason, using Dacron and fabric glue, like PolyTac, is absolutely up to the task and it is the lightest way to suspend the flight crew. When it comes to cabin furnishings in general, beware, upholstery is dead weight and detracts from performance, so make it light. Also, don’t run upholstery over outside edge of seat as clearances are very tight.

Foam for Padding
Almost any type of foam can be used on the back but on the bottom. A memory foam such as
“Temperfoam” be used. It weighs a little more but has better shock absorbing capability. When building the seat cushions remember that this is where you fine tune the seating position to suit the leg length and sitting height of you and your passengers, so have the rudder pedals in place before doing the seat cushions. Regardless of the type of foam you use, a good tool for shaping is a kitchen electric carving knife like those intended for slicing a giant ham. Some foams can also be shaped with aggressive sandpaper in a power sander, but practice on some scraps first.

Installing the Back Seat
The back seat is secured to the floor by four special bolts supplied with the kit. Some kits have specially-made bolts with thick tabs welded to the top. Some use eye bolts. These thread into the four bushings welded in the floor. In early kits, these holes in the fuselage must be tapped (threaded) for the bolts. Later kits are already tapped. There are two different sizes of bolts used, 3/8 in the back, and 5/16 in the front. If you’ll be tapping the holes, run a drill bit of the proper size (Letter I and Letter Q) for the 5/16×24 and 3/8×24 taps. Approach the tapping operation carefully and with a lot of patience because getting in a hurry will result in a broken tap, which isn’t easy to remove. Keep in mind that you’ll never break a tap as long as the top of the tap and the bottom of the tap are rotating at the same speed. The bushing has been welded on, which causes it to be harder in some areas than others and where it is hard, it can be very hard, and will resist the tap. So proceed slowly. The key to success is lots of cutting oil and a tapping method where you turn the tap only 90 degrees at a time and back it up 45 degrees after each rotation. If you stick to this, you’re very unlikely to break a tap. Don’t yield to temptation and try to speed it up or force it.
The rear seats can be cross-bolted into position or, if you plan on removing them often, use “pit pins,” those are usually T-shaped pins with a push button in the middle that retracts two balls in the pin allowing it to be withdrawn. These pins are available from B&B in Kansas.
More pictures courtesy of Dave:

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.

4-Place Engine Selection Tips

Purchase your engine as late as you can. The longer you store the engine, the more susceptible it is to corrosion, damage, or obsolescence. You’ll need to have an engine to build the cowling, but if you are lucky enough to have access to a core, it will do just as well as an airworthy engine. There are some benefits to deciding on an engine plan early, such as being prepared for purchase if a good deal comes along, and planning the supporting systems accordingly.
Bob Barrows designed the Bearhawk around a 4-cylinder angle valve Lycoming O-360 that produced around 170 horsepower. His second prototype used the parallel valve Lycoming O-540 producing around 235 horsepower, in part just to see how it would do. The airplane is a great performer with the smaller engine. With the larger engine, it has been described as “barbaric.” There is a natural tendency to think that bigger is better when it comes to engines, but this is not always the case with airplanes. Don’t let your ego make the decision. Bigger engines are heavier, and often require additional system requirements that further compound the weight gain. Read more about this topic in the Bingelis books. Bob prefers to see the engine weight kept under 400 pounds. Continental 0-470/520 engines weigh a little more than that, so he has adjusted the design of the motor mounts for those engines.
To oversimplify, here are some rules of thumb: if you live in a place like the western United States where you’ll frequently be climbing to density altitudes above 10,000 feet, or if you’ll be regularly flying at weights above 2200 pounds, lean towards the larger engines. If you’ll not be regularly needing these kinds of performance demands, you can save around $10,000 in initial cost and 100 pounds of empty weight by using a smaller engine. Ongoing cost savings will include reduced fuel burn during takeoff and climb and reduced maintenance needs of the 4 vs 6 cylinders. Both configurations will burn essentially the same fuel in cruise at the same airspeed, but if you cruise both at a high power setting, the bigger engine will deliver around 15-20 extra knots for 3-5 more gallons per hour. Back at 65% power, the average fuel burn of a 540 is approximately 12.5 gph, versus 9 gph for the 0-360.
Drag increases noticeably with speeds above around 115 knots, and the resulting miles per gallon will reflect this.
Regardless of your choice, be prepared for a dizzying number of variants, some of which may seem like a bargain. They may indeed be a bargain, or they may be something totally unusable that will be expensive to reconfigure. The safest bet is to stay near the center of the envelope, so to speak. Here are some tips to help you narrow down the choices.
Consider what you’ll need for accessories, since this may narrow down the engine choice. Although not a requirement, a constant speed propeller is highly recommended, and will make it possible to better utilize both ends of the airplane’s speed envelope. If you plan to run a constant speed prop from the beginning, or if you think you might like to ever install one, consider this in your engine shopping, to ensure that you have the appropriate provisions for a prop governor and a hollow crank.
Many builders consider mounting an alternator on the vacuum pump drive pad. These alternators are available in a range of sizes and can serve as a backup to a front-mounted belt-driven alternator, or as the only alternator. Your choice here will determine whether you’ll need to have a vacuum pad and drive.
Most carbureted Bearhawks use gravity fuel systems. As designed, the system delivers adequate flow for engines in the recommended range, and will not require an engine-driven fuel pump. Builders choosing fuel injection will require an engine-driven fuel pump and the associated provisions in the accessory case, and likely other components aft of the firewall.
As far as ignition is concerned, there seems to be a consensus to avoid the varieties with a single magneto drive. Beyond that, builders have used traditional mags as well as the experimental electric options with good results.

Choosing a 4-Cylinder Lycoming
First, limit your search to those with Type I Dynafocal mounts, since these are the only ones that will fit the engine mounts provided by Bearhawk Aircraft. Bearhawk Aircraft does not support conical mount engines.
Some builders shop in the 0-320, 150/160 hp size, but those builders must pay particular attention to keeping the airplane light. Kept reasonably light, the overall performance will be better than a C-172 by a measurable amount.
The 180 hp 0-360 engine is probably the best choice for 90% of BH builders. It is available new from Lycoming (with special OEM pricing for kit builders), in various experimental engine kits from other suppliers, and is ubiquitous in its use in many applications. Some of the alternatives include Superior and Continental (which has recently bought ECI/Titan).
With 170-200 HP, the takeoff and climb performance will be on par with a Cessna 182, although cruise will be lower, around 110-115 knots. The wide deck and narrow deck options are both acceptable, but look to the angle-valve variants rather than the parallel valve. These engines would have been fuel injected in their original configuration, but with guidance from Bob many Bearhawks have flown with these cylinders and a carburetor. When Bob builds an engine like this for the 4-place Bearhawk, he uses a rear-intake sump and makes a special 90-degree adapter to move the carburetor aft. This puts the carburetor in about the same place as it would be for a 540, and makes the exterior intake much more streamlined. This is possible because the 4-cylinder engines leave cavernous space between the engine and the firewall, since the prop mounts at the same station regardless of the engine. Within the 360 variants, the final horsepower will be determined by the compression ratio. This will also determine the minimum fuel grade. A ratio in the 7:1 neighborhood will deliver around 170 hp with the ability to run 87 octane fuel, assuming you can find it without ethanol. Ratios near 8.5:1 will deliver around 180-190 hp with the ability to run ethanol-free 93 octane fuel. Higher ratios will require 100LL, but will deliver closer to 200 hp.
Adding fuel injection makes it an IO-360. This adds weight and complexity, and will provide a slight power increase.
There are a few 4-cylinder variants that increase displacement and horsepower. One is the IO-390, which produces in the neighborhood of 210 hp for a cost premium of $15,000-$20,000 over the angle-valve O-360. This variant has flown successfully in multiple Bearhawks. Another is the Titan IOX-409, which is rated for an astounding 230 hp, but at an equally astounding price. They also offer the 370 and 375 “Stroker” engines, which have parallel valve cylinders making 185 – 190 HP with a carb and 195-200 HP with fuel injection. With any engine choice, but especially with the less common choices, it may be beneficial to talk with a Bearhawk builder who has successfully implemented the design, which will help identify any required deviations from the basic configuration.

Choosing a Six-Cylinder Lycoming
The 0-540 series of engines are heavier, but provide an increase in overall performance that is hard to believe. However, nothing is free, as the useful load will go down at least 100 pounds. Experience shows that it may go down as much as 200 pounds if the larger engine inspires the builder to also install auxiliary fuel tanks (30 pounds), fuel pumps, etc. Choose a parallel-valve 0-540, not an angle-valve. The angle-valve engines weigh over 80 pounds more than the others. Whether it is a wide deck or narrow deck engine makes no difference. You’ll find variants producing 235 hp, 250, hp, 260 hp. 235 hp engines (“B” series) are lower compression engines capable of burning automotive fuel. They are cheaper and easier to acquire, and performance is still unbelievably good.
Hartzell constant speed props can only be used on O-540 A4XX, 0-540-B4XX, -J3XX engines. All other series of 540s, which are usually early engines, must be modified with heavier crank shaft counterweights or use a McCauley prop.
All 540 Lycomings can be easily modified with the heavier counter weights. They can be installed without disassembling the engine, by removing cylinder No. 6. The parts and instructions are available from: Johnston Aircraft Svc, Inc, P.O. Box 1457 Tulare Municipal Airport, Tulare CA 93274, 559-686-2161, www.johnstonaircraft.com.
There are two types of mount ears on 0-540s. The Type I has 1 3/8” holes the Type II has 2” holes. These determine which motor mount you’ll need from Bearhawk Aircraft, and which motor mount rubbers to buy. The mount lugs bolt to the engine case, so they are interchangeable, but expensive.

Continental 360/470
The six-cylinder Continental 0-470 engines represent good buys on the used market and are smooth running, well known engines. They are usually heavier than 0-540 Lycoming, and use McCauley props. The output will vary from 215-285 hp, depending on the output. The IO-470 is 260 hp, but there’s the probability of firewall interference with the longer fuel handling unit at the rear so it’s not recommended. The basic cowling design was for the Lycomings, so modifications will be required. These engines use an entirely different mounting strategy, and variants other than the O-470 will likely require custom mount fabrication. We say that the O-520, being heavier than the O-470, which is heavier than the O-540, is not a viable engine for the Bearhawk.

Automotive Engines
Bearhawk Aircraft does not provide any support services for automotive conversion, so you’ll be designing your own motor mount, cowling, etc. You are building your own airplane, and it is your experiment. It is your own choice to make, but consider the following. The automotive engines can seem seductive. What’s not to love about an initial price that is 1/10th that of a Lycoming? Traditional airplane engines were designed many decades ago, so surely there is the technology for making better engines now? Sometimes a builder starts down this path and feels like he has stumbled upon a secret alternative that nobody else knows about.
The big issue with auto engines is that we must not just consider the engine, but rather the overall task of powering the airplane. We often hear in hangar discussions that airplane engines are really simple. In some ways, they certainly are- but in many ways, they are not. Every aspect of their configuration has been carefully considered and engineered over decades of use. Design choices are not arbitrary- they are almost all based on making the most reliable overall powerplant possible, applying lessons learned from failures large and small. The same applies to engines designed for cars, perhaps even to a greater degree. The folks at Subaru have painstakingly engineered every detail of their engine, how it relates to every other aspect of the car, and how it is used in that application. But how does that application relate to the airplane environment? Airplane engines are designed to run near their maximum RPM for hours at a time. Car engines are designed to operate at maximum RPM for only a short time. When it comes to cooling, the airplane engines applicable to the 4-place Bearhawk are air-cooled. Most car engines are liquid-cooled, and are going to require a radiator. Where is that going to go? The airplane engines are direct-drive, turning the prop at the same RPM as the crank. Will the auto engine be able to deliver the performance you’d want in that configuration, or must it be geared down? How is fuel to be metered, and ignition to be delivered? How robust are those systems, and what is their failure mode? Do those devices give warning of failure before they completely quit? What kind of propeller choices are going to be available for the car engine? How hard is it going to be to service the airplane custom components when you are away from home and have a problem? What about insuring the plane when it is time to fly? What about resale value?
All of these questions get to the broader goal of providing a total powerplant solution. Mounting, cooling, fuel metering, intake, ignition, exhaust, and power transmission may sound like just a few little things to sort out, but experience shows that these are actually really big things to sort out. An auto conversion adds at least a year to the construction time, apples to apples. The majority of Bearhawk builders who have stuck it out and flown with auto engines have later switched to traditional airplane engines after their plane was flying. There are one or two notable exceptions, and for anyone still considering an auto engine, we strongly encourage you to get in touch with one of them.

Propeller Considerations
Most people use a constant speed propeller on the airplane, though it is not a necessity. A fixed pitch prop will save around thirty-five pounds and many thousands of dollars.
The downside to using a fixed pitch prop is that, of necessity, it will be a compromise in most parts of the flight regime. Because the Bearhawk has such a wide speed envelope, regardless of how you have a fixed pitch prop pitched, it will be slightly wrong at least part of the time. For example, one Bearhawk with a fixed pitch prop had a great takeoff roll and climb, but required a nearly immediate throttle reduction at level-off to prevent exceeding maximum RPM limits. With a constant speed prop, the throttle can wide open, or anywhere else, delivering much faster cruise speeds when desired. Special pricing is available on most props for kit builders when the props are purchased through Bearhawk Aircraft.