Jabiru Engine First Run

We started the Jabiru 3300 for the first time yesterday. It started on about the second blade but ran very rich. Normal adjustments had little effect so we rolled it back inside for a closer look. We discovered a metal flake stuck in the needle and seat of the Rotec TBI fuel regulator. By the time we got it back together the rain had set in. Rain is predicted for the next few days so it might be a while before we get to run it again. Sure did sound sweet as it leaned out when we shut off the fuel.

Tail Wheel Progress

We shortened and de-arched the tail wheel spring. It was a little too soft in its original length. The spring is a Piper Cub unit 1-1/4" wide. It now feels good when fully loaded and has a good angle on the vertical pivot.

Tail Wheel

The tailwheel was mounted for the first time yesterday. This is the Home Builder's Special from Aircraft Spruce. The wheel is 6" diameter. Only one spring leaf is installed at the moment. At least one additional leaf will be required. There is still hope for a carbon fiber spring for additional weight reduction. Given the light weight of the Jabiru engine, I am trying to keep weight off the tail as much as possible.

Instrument panel Progress

Tom has almost completed the wiring for the instrument panel. The layout has evolved somewhat so that a few critical circuit breakers are located on the panel and a few non-critical breakers are located on a sub-panel hidden behind the AV80R GPS/Moving map. The AV80R has buttons located on its edges so it has to be surface mounted on the face of the panel. It snaps out easily for use in the "land mode".




"Eyeball" fittings are used for the signal wire penetrations through the firewall. Having the right tools really comes in handy for tasks like sizing the holes in the two-piece eyeball to the appropriate size for the wire bundle. Les set these up in his mill and sized the holes as required.

Fuel Piping FWF

We completed the firewall-forward part of the fuel piping today. A Facet fuel pump is employed as a back-up to the engine driven pump and as a boost pump for priming at start-up. 3/8" tubing and hose is used throughout. A fuel flow transducer will supply info to the EIS engine monitor yielding fuel used, fuel remaining and time remaining. Others who have used this system have reported that it is very accurate.

The system is somewhat complicated by the addition of check valves to create separate and parallel systems for the two fuel pumps. This is probably overkill as the engine will likely run okay with gravity flow under most conditions.

Oil Cooler

The Jabiru uses an oil cooler adapter which fits between the engine block and the oil filter at the front of the engine. The supply and return lines run to the oil cooler which is located back on the firewall. The adapter normally has 1/8"NPT ports but we enlarged them to 1/4"NPT feeding 3/8" hoses.



Cooling air will be supplied by a NACA scoop and flow downward through the cooler. The hot air leaving the cooler will be ducted down to the intake and used for carb heat when necessary.

Trim Tab

Nose Up Trim



Neutral Trim



Bottom View



I decided to utilize electric elevator trim. The RAC T4-5 trim servo is small enough to fit with-in the horizontal stabilizer making a clean installation. The tab and the tray for mounting the servo are made from carbon fiber.

The T4-5 servo has no trim position indicator but I can either set the trim tab position during the preflight walk around or just look over my shoulder during the pre-departure check list. In-flight trim adjustment is always made by trimming off any undesired stick forces.

Comm Antenna

I have been researching antennae suitable for fabric airplanes. It is difficult to find anything approaching the ideal location/orientation for the comm antenna. I first looked at the 1/2 wave dipole antennae from AAE. I then discovered the Miracle Air Whip antenna which is my choice of the moment. I plan to provide mounting points for 2 or 3 alternate antenna locations/orientations prior to fabric covering. Then I can easily experiment to find the best position.

www.miracleantenna.com/airwhip

Possible Paint Scheme

My good friend Gardy has a neat airport bicycle which is painted in an unusual gray and yellow paint scheme. I never would have thought of that combination but it actually looks good on the bicycle. Here's how it might look on the Skyote.

Hawkeye thinks it looks better with no stripes and big numbers. It does have that vintage look.


The last biplane I had was red all over. I don't recall seeing an all red Skyote. Not bad!

Head Rest

The fiberglass head rest is complete. We made it extra strong in case someone sits on it climbing in or out. Dale had suggested that we use it for storage. It's a good idea but if we keep adding details we will never finish!

New Strut Design - First Look

Got a chance to fit the the new design landing gear compression struts yesterday. All-in-all I was very pleased with the first look. We just used a kluged-up mixture of urethane bushings to see how they reacted. The amber bushings are of soft durometer and the blue are somewhat harder. You can see the bulge in the amber bushings yielding about 1/2" of compression. We did not use any pre-load of the bushings but some will be required. We won't be able to choose the proper durometer, number of urethane bushings, and preload until the weight of the complete airplane including pilot and fuel can be applied.

This strut design provides the following features:
1. Tunable "spring rate" and possible progressive spring rate.
2. Adjustable preload of strut.
3. Adjustable ride height.
4. Fail-safe relative to bungee breaking.
5. More compact than bungees.
6. Much simpler to build compared to the bungee strut.

As a matter of interest, the left strut in the photos is set up for maximum spring rate and zero travel as it has no bushings. Might be a little on the "hard" side!

Throttle Quadrant Refinements

The throttle/mixture quadrant has continued to undergo minor refinements. Specifically, all of the phenolic friction washers now have anti-rotation tabs. Also, the anti-rotation pin through the shoulder bolt has been replaced by a stainless steel tab welded to the head of the shoulder bolt. This makes assembly and disassembly much easier,

Rather than welding the assembly mount to the fuse diagonal, the assembly is now held in place by a two-piece clamp collar. This allows some adjustment of the position and makes removal for maintenance or modification more convenient.

Throttle/Mixture Quadrant Completed

Eventually you have to quit designing and cut some metal! I decided I had reached that point with the throttle/mixture quadrant so I machined up the latest version this weekend. I haven't drilled the attach holes for the throttle and mixture cables yet as I want to confirm the correct position with everything in the airplane. The paper pattern is still on the back side of the levers and shows the likely position of the attachment holes for the control cable ball ends. Also, black and red spherical knobs will be pressed into the ends of the handles when they arrive.

This design works on the same principle as Pete's design using bellville washers but has been modified to include the mixture control as well as forward stops for both throttle and mixture. I will likely add a small lever to the friction adjust knob when I can determine the correct location so that the lever will wind up in the correct position for easy adjustment.

The action is good and smooth with the friction adjustment being fairly linear through about 1/4 turn of the friction adjust knob. Each of the controls is isolated so that movement of one control does not affect the other control or the friction setting.

Cowling Progress

Dale has continued to pound metal and as a result the cowling is really taking shape. Forming the "eyebrow" cooling ducts has been quite a challenge but they are almost finished. We used a fiberglass cooling duct supplied by Jabiru as a model but the duct we used has been replaced by a later model which gives "better cooling". Hopefully this design will work okay for the Skyote.

Throttle Quadrant Re-Do

I built a model of the previously proposed "pony brake" style throttle quadrant which was less than satisfying in relation to the smoothness of the action. As a result I have gone back to a design much closer to Pete's original design. It uses a stack of Bellville washers to develop the friction when compressed by the knurled knob. A mock-up of this arrangement gave very smooth action so this will likely be the final design.


This part is made from 1/4" 4130 and welds to to the diagonal fuselage tube in the appropriate position. It provides the basic mount for the quadrant and provides the anti-rotational anchor for the shoulder bolt which serves as the pivot for the throttle and mixture levers. The shoulder bolt and the bellville washers came from www.mscdirect.com and the 1/8" phenolic for the friction washers came from Aircraft Spruce. The levers are fabricated from 0.070" titanium and the knobs from 6061-T6.

Nose Bowl--One More Try

The nose bowl is getting close. This shape seems to work better.

Engine Cowling/Nose Bowl

Here's the first stab at the cowling/nose bowl. We are now trying to reshape things to let the cowling and nose bowl flow together with out the bump at the junction. Cowling a "first time" engine is lots of fun. Looks like it will take about four attempts to get it right.

I had originally intended to use the same nose bowl/spinner as Pete Bartoe did on his airplane. Unfortunately, it just did not work out well with the Jab engine. Also the spinner combined with the 6 cylinder engine was starting to make the nose look a little long. A rounded nose bowl with a "skull cap" spinner will help keep the nose in proportion

Hanging the Engine

We hung the engine on the firewall Saturday afternoon. Now begins the process of finding a home for everything. Unfortunately, it looks like the Jabiru exhaust system is going to require significant modification.

The nose bowl ala Pete Bartoe also has some difficulties jiving with the Jab engine. We may revert to a round style nose bowl like Hawkeye/Dave Novak.