Engine Upgrade

This blog covers status of the work to convert the Rotax 912 into a supercharged engine.

Overview
The factory has undertaken a period of testing that has validated the FlyGas Supercharger upgrade, this modification has proven safe but remains an experimental engine, so for those seeking more power with a proven record the factory is recommending the proven Rotax 914 or maybe a Rotax 915 when available.

The existing 912 mechanical fuel pump does not cope with the extra fuel flow demanded by the supercharger and requires the installation of two [2] electric fuel pumps. The 912 pump will cope once the power is reduced to below 100 hp so this does provide a mechanical backup in the event of a total electrical failure [i.e. regulator] but is messy requiring two pumps and their electrical demand with a limited alternator output.

A product known as a "Billet Pump"  was marketed in the US using a piston pump for engines up to 400 hp using carburettors or low-pressure fuel injection but appears to have been removed from sale by the supplier. Robert Borger's Europa has a conversation and had other pilots interested but the supplier would not respond but is happy with the performance of the pump. A single electric pump will be fitted and operate in a similar manner to any low wing aircraft.

Robert Borgers Billet pump installation

Robert has provided all the information on his pumps 
construction aiding the design of a new installation

After a lot of research starting with the patent number, it was discovered this was a modified automotive product so it was decided to replicate the original design intent and this will be covered in a later blog. This is a proven concept so its anticipated there will be no operational issues and once proven I will make available all the drawings and STP files for the machining as an educational package once I work out how to remove the existing adaptor. When done a 3D model will be developed to mount the pump on the Rotax and sent out for CNC machining. 

Another upgrade is the installation of a Silent Hektik regulator that allows an output of 20 amps from the existing alternator, additionally, a water-cooled oil cooler from the same company is to be incorporated to tidy through the air flow through the cowl.

Reference: DOG Aviations RV12 - interesting reading

Note:  I have found the VANS RV 8 / 12 an excellent source for information and validation.

To assist in creating a more directed air flow a top mounted cooling hood used on the VAN RV12 is to be installed, this was selected over the same item from Rotax, it's a 1/4 of the cost. It will be feed from a 2'' NACA duct located on the lower port side of the cowl.

RV12 Air Hood
It will be fitted to the rear to gain as much
clearance as practical but can be modified

Engine
The installation of the supercharger requires the installation of decompression rings lowering compression to 8: 1 preventing detonation at a boost of 6 psi. All this work is to be undertaken by Joe Newman an RAA L2 as I am time and skilled challenged in this area and Joe has an engine mount at his hangar at Rylstone, it is now hoped the work can begin in July. 

Joe will be keeping a photo log that will be published in this blog with any of his notes on assembly issues. The manual from FlyGas is very comprehensive as is the kit so these notes will fill the gaps.

Comment
Finally redesigned the intercooler and now has all its detail drawings prepared and will be sent out for manufacture locally. Once complete and installed it will be included in an update but it's smaller and a LOT lighter by mounting directly on the engine mount.

Other items - there a lot of jobs at various stages but there is a long wait for parts coming from mainly the USA creating increasing time between the posts, regrettably in Australia it's an industrial wasteland....!

Stab Nick

This blog covers the issues created by a nicking the elevator spar when installing the starboard fairing and how a simple task when bad.

Stuff ups do this

Overview
After completing drilling the port side fairing to secure the faring the next task was to repeat the work at the starboard side. All locations for the holes were transferred to the fairing with all holes then drilled with a 1.5 mm drill.  

It was late but it was decided to complete the task before stopping for the day. To secure the fairing tightly onto the fuselage side, it is necessary to use one hand to press it into position and using the other to drill holes. All went well until the hole nearest to the spar was drilled penetrating the skin striking something hard and causing the drill to slice forward. 

This is not good - high stress area
tension flange - a bad combination

Poking around with a length of brass wire a distinct click was felt and I then knew it was the spar that had been struck. 

To investigate fully what had happened the tail plane had to be removed which was achieved in under a hour - a quick removal of a few key rivets revealed a distinct gouge in the radius of the spar. 

With the skin de-riveted enough to allow access to the damage it was worse than expected with the side of the drill machining into the fillet of the spar.





After a lot of emails and a Skype call there were three alternatives available

• Repair damaged area - cheapest, untidy
• Replace damaged spar - complex, cost effective
• Replace stab - expensive, perfect

Comment

In the cold light there was about 2-3 mm difference all in the wrong direction and the damage was 60% depth. This was a result of believing all was correct, late night get there at all cost but there is no denying it was just dumb, stupid, blind decision - there are really no words to cover gross stupidity.  

If you make an error don't hide, investigate, speak to the factory or TC , they as interested in your safety as you are. The danger posed was not immediate structural failure but crack's developing creating an undetected, progressive failure over time. 

Doing it again mark all the locations and especially the position in the critical area of the spar for 25 mm either side of the rivet line and all the hole location line before installing the stab with the final position marked on that line in conjunction with the faring.

The critical area should be covered with 50 mm painters tape with a series of "DO NOT DRILL"  as all will be forgotten by the next week. 

The side fairing has a cut line marked by a groove in the faring - mark a new line that removes the minimum of material and sand it square. This should allow the installation of the rivet nuts OUTSIDE the line of the ribs and provide a flatter area to screw down as the curved area need a lot of pressure to get it tight and creates a awkward drilling scenario on the underside

Go to bed and drill all the holes next morning. 

Now that I have confessed, ordered a spar its time to return to the rock....!

Canopy Mod - Part 1

This blog covers locating the canopy in the fuselage and solving the problems created by the installation of the gas strut and is for record only.

Overview
With the latches installed  the movement to starboard of the canopy frame created by the gas cylinder had to be corrected.

It was found that if the the cylinder was removed all the gaps and alignment with the front cowl were correct, confirming that the cylinder was the cause of the alignment issues.

With the cylinder reinstalled and canopy closed it all moved to starboard but if the frame was pushed just past the front hinge a substantial correction occurred.  After a lot of thought it was realized that the cylinder now hinged the canopy frame at the rear with all the clearances appearing at the front hinge.

What was needed was a means to counter the 14 kg of side thrust. While lifting the canopy up and down and considering options it was realized that the inside face of the canopy was close to the roll cage - had a ridged mount.

Installation

Test wheel and longer locating pin

After marking out the location of the base of the frame just before the hook was engaged the location for a hole was marked and drilled through the roll cage frame. This process was difficult requiring the use of a small battery drill to penetrate the hard spot on the front face.

Note: The battery drill slow speed allowed the drill bits ends to survive the pressure required.

An old rubber caster wheel was wrapped in tape, fitted and the canopy lowered - joy of joy every thing was back in alignment on the port side and at the front and rear. There was still a issue at the front hinge but it was felt the installation of the locating pins would address that issue.

A new longer brass pin was installed at the center and with the nose of the hook dressed the canopy closed one handed but inspection at the front and rear showed that the gap between the front cowl had opened up and the rear closed. 

What caused this ?

Numerous adjustments and test showed that the canopy would open and close while picking up the center pin but the front and rear pins were out just slightly. At this point the center pin was removed and everything returned to normal, it was realized that the canopy was being push out of shape by the center pin.

The most likely cause was the new spreader / cylinder attachment with gussets added to control the torque created by the cylinder attachment. Where the original spreader had no ability to affect the frame shape the the new rigid spreader did and locked it in. When these were added no relationship to the locating pin was taken into account, this explained why all points were just out - a new shape had been created.

Spreader & Gussets

Button length determination
and rear button installed

It was decided to start by fixing the canopy's relationship to the fuselage fore and aft before reinstalling the pins. Two holes were tapped M3 in the front cowl frame and temporary Bakelite buttons fitted, next blue tack was fitted and covered with glad wrap and the canopy closed. 

The height was measured and a new buttons were machined and fitted, this process was repeated at the rear leaving about a total of 1.5 mm gap between the front and rear buttons.

The front buttons ensure that the frame squares up as its closed with the latches operation re-checked before moving onto the next task.

The final task was to refit the pins but to reuse the original locating holes required a new mounting point for the center pin. A piece of 25 x 3 aluminium is was fixed in location to the longeron using thin double sided tape then the location of the pin marked using the same technique used originally. 

Revised attachment

The aluminium was anodized then fixed using M4 x 12 hex head screws with the pin fixed using an M4 counter-sunk screw, refitted, tested with the same technique to be used at the front and rear.

Comment
Why all these issues  - probably an operator error - no excuses offered.

Next job is to install the correct wheel and guide cam but right now it works well in fact until the rear hinge was added it could be closed by just pressing down on the canopy with the front hook opening and closing the mechanism on the way down but with both hooks in it closes easily with a reassuring solid thunk after a firm push on the handle..!

Canopy in the 50% open position and balanced

Nearly there..!

Graphics

This blog cover the graphics.

Overview
In a previous blog the process for creating the labels for the panels was outlined.  

The interior graphics have a major advantage over the exterior one, that is you know the finished size and using the process outlined in the earlier blog work well for this builder.

The exterior graphics proved to be a whole new problem with no ideas about size so the builder had to scale the necessary graphics off a illustration for a decal set for a 1:48 plastic model.

Alley Cat Decal Sheet illustration captured off the web

With the graphic above open in Inkscape the measuring tool was used to find the distance from the spinner to the tail being of a 106 mm

The length for a Tucano is approx 34'  or 10360 mm 
Scaling factor 10360 / 106 =  98

Replica scale = 0.7

To calculate the size for any decal :

Measured dimension x Replica scale x Scaling factor = Decal dimension

All graphics were drawn in DrafSight a 2D Cad package and colour corrected in Paint.net if required and finally sized in Inkscape.

Note: All packages are shareware

After that you can have them printed on vinyl for installation when the aircraft is painted or as required in the cockpit. The satin black has by luck proved to be a near perfect match for the paint used on the panels.

Breaker Panel

Note: Cockpit graphics, these have 1 mm added to allow a final trim when fixed to the plate.

Comment
Two of the graphics had to be customised as on the prototype they both have warnings about things that can go bang or standing back and making things go bang, this could create a reluctance in a world full of OHS to professional help being available quickly.

With the Tucano having so many paint schemes and the replica being so close this technique will allow the development of graphics from any flat illustration. These are all out for printing so if it works as hoped it will be all good.

The text used is the same as on a CT4 RAF trainer seen
at the last Rylstone fly in

This was modified from graphics seen on the UK dealer Tucano
The black background was chosen over clear as it
will become very untidy over time. 

Construction is still proceeding but slow to finish at this time - lots of small issues and generally this builder shooting himself in the foot.