Aileron Trim Part I

This blog covers the design and installation of the aileron trim. 

Refer disclaimer

Overview
Obtaining of the approval to use the original quick build kit from Flying Legend was a difficult one and took this builder about 3 months work to understand and then learn to apply the rules.

Put simply the chart of tasks contained in AC29.xx allows points to be granted to the builder or the manufacturer and the balance must be that the builder has 51% of the work as outline in the document.

Chose to fabricate a complete set of wings from scratch and assemble them you would be granted one [1] point for each or a total of two [2] points - simple eh..!

Now chose to fabricate a trim for the aileron on the wing that you just built you are granted one [1] point for each task or a total of two [2] points - confused, join the club.

At this point Martin Ongley of the SAAA came to my rescue to explain the underlying rules because at this point the 51% just kept creeping away. So if a builder does some fabrication and assembly on a factory quick build he can take a point also, its called tap - tap. This is not to have you fabricate or build a wing, the rule makers just need you to understand the process by your input.

FAA kit listing of the Tucano as 
complying with the 51% rule
Gold plated complience 

The real intent of the apparent discrepancy of work allocation between building a aileron trim and a wing including the aileron is for you to display your ability to fabricate and assemble a small piece of an airplane yourself then make possible to purchase a quick build wing while meeting 51% of the constructions tasks - make sense!

Back to today, as this was the submission that  opened my account and with the initial resistance to use of a quick build kit on display at my original approach to the governing body's in Australia, it would be best that this builder sticks to the guideline agreed on and checked by CASA.

Note: CASA AC29 is a direct copy of the FAA guidelines. The factory now has a 51% FAA listed kit so there are no issues to new builders - just follow the plans and factory notes and you are there.

Design
The first task was to layout a suitable mechanism and after many hours of drawing the design outline  was fixed. It places the trim drive at or near the hinge line driving a 2 mm carbon fibre tab fixed to the trailing edge of the aileron with extruded piano hinge. The push rod is a length of 2024-T3 tube fitted with 4 mm od aluminium rod ends to accommodate the misalignment created by the geometry of the mechanism.

Final Layout

The next task was to determine how much force could be developed by this arrangement. 

To estimate of the force exerted by the tab and to keep it simple it will be treated a plate in a stream of air with the formula used shown below.

F_d = c_d 1/2 ρ v² A   -   all information extracted from the Engineering Toolbox

Where Cd = 1.98  v = 84 / 70 m/sec  
A = 0.008 m/sq  projected @ 30 degrees

84 m/ sec = 300 kph
70 m/sec = 250 kph

Using the numbers at max a force of 67 N [big arrow] creates a rod thrust of 27N [max] with the tab having a available force of 33 N and reduced by 83% at cruise

The actuator selected is a Actuonix L12 12V 210:1 Miniature Linear Actuator providing a peak trust of 80 N and operating peak of 62N @ 3 mm / sec with a mass of 40 grams with a total travel of 30 mm or 15 mm on each axis.

This package will fit in the D nose of the aerlion and should provide adequate thrust based on the calculated and manufacturer specification. The bell crank will be machined from a solid bar to avoid welding and will be pivoted in sintered bushes off 5 & 6 mm diameter mounted into a 2 mm aluminium bracket riveted to the face of the aileron spar which will also will reinforced the opening for the push rod.

A rough comparison using the same techniques shows the torque exerted by a aileron at 30 degrees deflection compared to the tab showed it to be about 3 - 5% of that of the aileron assuming tab was neutral, so it can be assumed this is a safe starting point. The tab could be widened if required once the the results in the real world testing are confirmed.

Comment

In detail if the numbers are right extreme care still has to be exercised as this is only a basic mechanical analysis using simple assumption but dose provides a guideline and is better than a wild guess.

Next task order part, manufacture and install - Part II

Wings Walkways

This blog cover the installation of the wing walks in the port wing

Overview
Aluminium top hat sections are installed at the port wing root allowing the pilot and co-pilot to enter and exit the aircraft.

Installation
The plans for my model show four top hats on either side of the main spar and it was decided to begin at the wheel well.

The factory top hats were trimmed to overlap the flanges of the ribs. This creates a 0.020'' [0.5 mm] gap so a spacer was folded from 0.5 mm commercial grade aluminium to prevent buckling of the skin when riveted.

First hole

With the hat fitted it was positioned into the well and the first hole marked using a felt tip pen by moving the flange across the pen - with the vertical position marked it was removed and the horizontal position marked along the flange. Finally a 1/8'' hole is drilled and the hat refitted with a cleco, leveled and then the other three [3] marked and drilled.


Note: A single piece was used for ease of alignment and the flared hole because I have the tools

Spacer - Packer

The other top hats were now positioned and drilled using the same method.

Wheel well port side with stiffeners
The plan called for four [4] but this builder was unable to fit the last one as it
would lay under the gear prevent full retraction.
This will have to be stiffened and will be revisited

Rivet line for top hats pitched at 60 mm using FL drilling jig [seen lower photo]
Holes were not pre-drilled and had to be done by the builder

The supports located along the front of the wing were done in the same way except the the first two from the spar down. To fit the top hats around the fuel sender and to allow removal  this builder could not acheive this without some additional work.

One stiffener had to have the flange cut and infilled around the access hole drilled in the blog on the fuel tanks.  An angle was folded and riveted to the inside web to allow the rivet line to follow around the opening.

No 2 stiffener modifications
Note line above to mark center to modifyed top hat
Lost the plot here and pitched the rivets at 30 mm should have 
put a note on the skin - this works

The first stiffener [closest to the spar] was trimmed to create a channel fitting the available  space and then drilled for a single row of rivets along its centre-line.

Comment
Overall just time with the mods beign the best idea I had on the day but not the best idea.  I have noted on the drawings that the stiffener arrangement has been refined for the new aerobatic wing.

The stiffeners will be riveted after the tank is installed allowing the spar bolts to be installed - next year.

Fuel Tanks

This blog cover the tank installation

Overview
This kit was originally supplied with the Explode Safe tanks but on Franco last visit the issue of weight came up. After a bit of discussion it was decided to exchange these tanks for a pair of the new factory aluminium tanks - saved another 3 kg.

Installation
The factory now supplies detailed drawings / parts list and instructions so this will not be covered with the tanks installed factory assembled.

The first task was to cover all the rib flanges with cork or foam tape. As the builder has access to 5mm foam sheet it was decided to install this product. It was split into 25mm wide strips using a box cutter with the flanges having 30 mm wide carpet tape applied. 

With the tape trimmed to match the flanges, the backing tape was removed and the foam applied with the result begin neater than adhesive.

Note: Selected foam is the same type of material used for concrete expansion joints, this product is manufactured by J&M Hobbies in Australia for hobby track underlay.

Next rib #6 was completely in-filled with foam to a thickness of 10 - 12 mm, a cardboard template was made then traced onto the foam sheet and two [2] profiles cut and fixed using the carpet tape.

Nose rubbers

The final task was to install rubber channel onto the nose area as a safety measure. Due to the tight radius the rubber channel had to be cut to allow it to be glued to the radius. This was achieved using a Xuron Rail Nipper #2175B. What is different from just side cutters is these are a flush cut shear on one face and are sharp, ideal for these tasks.

With these tasks complete a tank was slid into the wing and the skins clecoed back into position

Note: this task is part of the final assembly of the wing and finishing with the final drilling of all rib mountings holes from 2.5 to 3.2 mm then dimpling to allow use of countersunk rivets.

Fuel tank trial installation

With the ribs aligned the tank was positioned [chocked] using foam wedges. Next the position of the fuel cap inlet was measured after installing the neck with two [2] temporary bolts. This was checked and rechecked then the skin cleoced back onto the wings and the position marked.

Note: before the skin was installed a cardboard cover was fitted to the neck inlet with rivet lines used as datum's for all measurements

Measurements

A 3.2 mm hole was drilled on the marked center and through the cardboard cover, next the skin was opened to check the position on the cardboard. With the hole confirmed on center the skin was re-cleoced and hole saw used to cut a opening to suit the filler.

There is an amount of adjustment [movement] so it was decided to use the fuel cap as a locating jig for the over dress cover.

Checking hole center from trial drilling of the skin
Care had to be exhibited to avoid damaging the filler neck
under the cardboard

Hole cut for filler and cap - skin removed and all burrs
dressed and polished out

Filler opening backing plates

The caps outer ring was screwed to the filler neck and the cap fitted, then the outer cover A was fitted over the rim of the cap and aligned, finally the holes [2.5 mm ] were transferred to the skin. 

With the holes drilled part A & B were riveted together with counter sunk rivets and placed to one side for final assembly to the underside of the skin

Finally the cap was removed revealing the tank neck and opening into the tank.

Drilling holes for outer cover using the cap 
backing plate plate that is mounted under the skin

Finished assembly after cap removed

The next task was to install the fuel senders, drill an access hole and again the same procedure was used. Next the fuel sender as assembled and its position in the tank assessed as the factory now includes a thick spacer to be used if required - it was not required for this aircraft.

Fuel sender

An access hole for the fuel drain was drilled again using a trial hole - if measured carefully any small error can be removed when the access hole is cut.

Fuel drain

The factory sump was fitted with a 1/8'' NPT drain valve and plug at the tapped side port. All these are sealed using Aviation Gasket Cement #2 which is a semi-permanent sealant.

Note: cover any incorrect hole with tape - there are no second chances with a hole saw.

The final task will be to install covers and rivet nuts and this will be done at the final assembly of the skins.

Comment
One small error was cleaned up with the hole saw but it just take time and care especially with the access holes - there is no easy fix for a error

EPanel

E-Panel schematic

E-Panel ready to close
Black & Yellow wires are for the USB panel to be located below
Aluminium cover was manufactured creating a few more mm 
of clearance for the switches

Assembled Panel

Comments
A co-pilot panel was added to the rear of the aircraft to allow an instructor to land the aircraft safely in the event of pilot begin incapacitated.

The master switch is guarded to prevent unauthorized operation with an interlock relay preventing accidental operation of the propeller.

Merry Christmas 2017

Well another year gone and it's not finished - next year will be a big one, I promise. There are about 15 blog pages at various stages and I hope to publish a few over the holidays.

May I wish all, a Happy and Holy Christmas and a even better New Year.

Merry Christmas to all......!!

The blogger @ Rylstone

Merry Christmas

Undercarriage Installation

This blog covers various details on the assembly details of the undercarriage.

Overview
The factory now has a comprehensive manual for the installation of the undercarriage so these details will not be covered but a series of detailed photos showing the undercarriage as installed in this aircraft noting some small modifications when installed by this builder.

Installation
Covered in a series of photos and comments below.

Limit switch trip and fixing - these also locate the undercarriage - tapped hole in 
mount is for a M5 grease nipple yet to be fitted. When greased - all these points 
took 2 pulls from a hand grease pump
Details covered in earlier blog - click here for more detail

Tapping M4 hole to attach clamps for wire looms from each limit switch
This Bosch drill is a life saver - head can be removed and relocated in 45 degree
increments, also comes with a straight offset gearbox with same features.
A must have.

Chasing holes to mount limit switch trigger -required at each M4 hole due to builders choice to paint, all were tapped at the factory

Factory bolt A was replaced with a M10 titanium bolt [B] to provide a plain shank in the loaded area of the rod end eye.  

This is the only bolt that could be sound offering a plan shank with a the M10 ISO fine thread.  Titanium should only be used to replace bolts with a 8.8 rating. 

Titanium is prefered by serious racer today because of its high strength but where as steel bold bends when fully loaded this will material snaps.

But as stated previously in this blog  threaded bolts are are only suitable clamped connections.

Waterproof plug for limit switches - P clamps and elbow are part of the brake circuits - manufactured using 3/16' high pressure nylon hose

Bolt replaced with suitable length to maximise to the shank in holes - M6 spring washers were fitted to fix the bolt shank relative to the outer ling with all rotation occurring at the inner - now considering upgrading to Nord Lock washers for this tasks

Gear installed in port wheel well  
A - loom clamps installed into tapped holes
B - Bolt with modified head and grease nipple - metal tab is to prevent rotation as the head was machined to 6 mm o/a to create clearance required to scissor link
C - Aluminium P clamps to retain brake lines - covered on inside face with Mylar tape
to protect the nylon line while improve clamping force

Aluminium P Clamp securing brake line - fixed using a M4 blind tapped hole
Both internal faces of clamp were covered with mylar tape at installation

Limit switch mounting bracket has fitted with M3 rivet nuts
to allow removal of the switch from the bracket in service

Comment

The undercarriage for all its apparent complexity is well engineered and fits together easily once all the detail issues like wiring/plugs/hoses/etc are selected, positioned at installation. 

Most of the work is in the details not the undercarriage - not to be feared.

What more is there to say..!!