Seat Belt - Part 2

This blog covers the installation of the front seat belts

Overview
Covering the ongoing work to install the seat belts.

Installation

Rear Packer

With the seat belt frame manufactured the next task was to fit the seat. After trial assemblies it was determined that a 6 mm packer was needed at the rear support to create a near perfect alignment. 

Packers were manufactured from 2024-T3 bar, alodined and fixed to the underside of the seat using 3M trim tape and for ease of assembly then M8 studs were installed after treatment with thread locker.

Pilots seat adaptor
Crutch strap attachment is now located 
at the rear adaptor

Shoulder Harness installation

The leather seat belt openings were finally cut to allow the shoulder harness to be inserted through the back of the seat with the shoulder harness split into two separate runs then attached to the main spar. With the belt entry location set the top head cushion was marked to be taken back to the motor trimmer to have openings cut allowing the belts through to the seats.

Note: This was not done at time of manufacture as there was no idea how this would be executed, that's why the holes were cut in the seat but not in the leather so any error could be hidden - lucked out

Dogs fitted to seat bracket

The seat frame was secured to the roll bar using 19 mm electrical saddle clamps secured with M6 bolts using holes drilled through the seat verticals on both verticials..

To restrain the seat at the top the bolts retaining the saddle clamps were to be used but once it was determined that these would cut the stitching another method was needed. 

Dog clamps were fabricated using 50 x 50 x 1/8'' x 6061-T6 aluminum angle cut 25 mm wide with two [2] conduit clamps installed around the roll bar spreader and fixed to the seat frame using M6 screws.

Placing a short leg on the inside face of the seat with the other fixed to the seat frame with M5 rivet nuts then secured with M5 x 20 screws.

Note: Legs of the dog clamps were shortened to 25 mm to reduce leverage at the attachment point

Factory seat attachment - use of a seat frame
prevented this arrangement being used

Comment 
Final task will be install the belts and headrest on their return with the shoulder straps sent interstate to have the buckles stitched to extend the straps as close as practical to the main spar.

Mirrors

This blog covers the installation of the two mirror to mimic the prototype

Overview
All Tucanos feature two rear view mirrors mounted on the dash panel and to mimic these a couple of cheap aftermarket mirrors were located on EBay and purchased on a maybe.

Manufacture
Both mirror's featured fake chrome on plastic and that had to go, so the glass was masked and the body's rubbed back with 320 aluminium open cut. After cleaning, a light coat of plastic primer was applied along with two [2] coats of satin black. 

Tucano Cockpit

Brackets were fabricated from 50 x 50 x 3 aluminum angle x 20 mm wide, the brackets were located on the top of the panel, clearances to the canopy checked, location verified  and marked. 

Finally the mounting holes were drilled and the brackets fixed to the panel shroud. With the mirrors mounted onto the brackets and adjusted giving a clear view of the rear end - kinda of strange feeling sitting in the front seat.

Comment
Indeed they did fit

Tail Skid

Blog cover the installation of the tail skid

Overview
The current Tucano kits are supplied with a tail/skid tiedown that was not available at the time of purchase and the factory has shipped this and a couple of other upgrades for my aircraft at no charge.

Installation
The nylon skid was assembled using AN3 bolts and mounting brackets supplied with a pair of AN3 half washers as temporary spacers. These were removed after riveting and provide a small clearance to facilitate removal if required in the future. 

The assembly was aligned on the underside of the fuselage then 3/32'' holes drilled through pre-drilled holes in the brackets into the fuselage and clecoed as required. All holes were drilled through #80 drilled and fixed using 3.2 x 8 mm rivets after removing swaf.

Fairing was outlined in previous blog
providing a more finished look

Comment
Done

Leg Assembly

This blog cover items related to the undercarriage installation with some covered in the blog Main Leg Lubrication

Painting
One feature of the Shorts Tucano it's all white undercarriage. This required the removal of the unpainted small components, priming and painting with Wattyl Appliance White then a final coat of gloss clear.

White legs good excuse for a Tucano photo

Fixings
The leg attachment bolt beared on thread at one side - this was replaced by a M6 x 90 S/S Unbrako purchased for this task. These bolts were purchased from Fastener Kits Online in Australia who have full information on the shank lengths for the bolts they sell.

Sizing new pivot bolt
original bolt on bottom

Note: All bolts had the thread length trimmed to match the closest AN bolt. These bolts cannot be threaded with hand tools so time was taken to select a shank length to suit the application.

The bolt securing the leg arm has about 10 mm of shank engagement into the arm which would be OK but it was decided to replace these with M8 x 70mm S/S bolts with a full shank engaged into the arm.

New full shank M8 bolts

Comment
Should have published this first

Another step

Bits & Pieces - No 7

This blog covers detail tasks associated with main gear accessories

Brake Hydraulic Connections

Connection to brake caliper

The hose used is 3/16'' NSR tubing and SAE brass fittings designed to be used with this hose. In the exposed area near the wheel, the hose is covered with 10 mm loom tube for increased protection and appearance. 

The bare nylon tube was run along the face of the main spar secured with aluminium P clamp and pop rivets located in available factory holes in the spar web.

Electrical
The six wires from the two [2] limit switched combine at a 6-way plug located in the wheel well. Selected plugs are Seal All connectors having an integrated mounting slot in the back to accept a fixed mount. 

The mounting was fabricated from 2024-T3 x 0.040'' sheet, alodined, fixed to the wheel well using three [3] 3.2 mm pop rivets. The wires were prepared to the plug manufacturers specification, installed in the plug and fitted. The opposite side plug had six [6] length of wire run for later termination installed into 10 mm od wire loom and fixed to the spar using nylon clamps with pop rivets using available factory holes located in the spar web.

All exposed wire of the limit switches was installed into a nylon braided cover for appearance and protection in service with ends sealed with silicone or heat shrink as required.

All limit switches were fitted at the factory supplied mounting points using two [2] M3 x 30 cap head screws with M3 flanged rivet nuts installed in the lower mount to make removal of that switch more practical in service.

Main Pivot Bolt
The main pivot bolt was a threaded screw and this not personalty acceptable but hunt as hard as Google lets one, no alternative was available. At this point, the exotics were examined and a Titanium bolt  Grade 5, 6AL/4V was located and looked like it meet specification, after a lot of research a single M10 x 1.0 pitch x  40 mm was ordered just to suck and see.

At arrival, a trial fit proved it was correct and careful external examination showed it was manufactured to a high standard with the plain shank just a little short of requirement.

At this point the excess thread was removed with a hacksaw and a 2 mm thick washer machined. The bolt was inserted into the rod end and retained using thread locker applied at installation

Note: The head has an integrated washer but its was a tad small and the factory washer consumed too much of the plain shank. WD40 was sprayed to keep the bolt cool when cutting with the blade feeling blunt but it did cut cleanly


Comment
The connection bolt will be monitored for its performance in service but Titanium appears to have a suitable specification for this task but if a high tensile bolt is found it would be used.

Note: Titanium bolts are no substitute for bolts above 8.8 strength - recognizable through stampings of 10.9 or 12.9 on the screw head. If in doubt you have to assume that titanium bolts are NOT suited for the application to ensure your own safety.

Baggage Compartment - Pt 3

Note: The final location for the pump is at the revised access hatch shown in part 4 - it improved cog and access - See comments at end of this article

This blog covers the installation of the hydraulic pump into the baggage compartment.

Overview
The decision to relocate the hydraulic pump with the battery was a direct result of the factory supplying a spreadsheet for the weight and balance for the Tucano showing that the Tucano Rs having a particular problem created by the 7 kg of the additional weight of the supercharger.

This led to the factory supplying an engine mount shorter than a standard 912 engine mount to suit the supercharged model.

Estimated C.O.G.

What does this show this builder - A Tucano is very sensitive to weight on the nose wheel, so great effort must be expended firewall forward on weight control or balance it by moving items that the aircraft requires to the most advantageous location.

The factory currently installs its 5 kg battery behind the baggage compart wall but this option was not taken as the amount of re-work required was not acceptable and in the end a 30% loss of area in the baggage compartment was considered acceptable for the style of operation contemplated for this aircraft by the builder

A battery and pump have a 5 kg combined weight matching the factory battery weight. Remember this aircraft uses LiFeO4 battery pack [1 kg] with this combination 3 kg lighter overall.

Installation
The first task was to install the battery, and this was covered in an earlier blog.

Next, the pump was removed from the factory location, the base was removed and two more feet were fabricated from 0.040'' 2024-T3 and installed. The location of the feet was marked onto the floor, M5 rivet nuts were fitted then 25 mm studs were installed into the rivet nuts with thread locker.

New mounting feet

Two 50 x 6 foam isolators were installed over the studs to provide some noise isolation, but this may have to be upgraded at some time after the noise is evaluated. 

Local wildstock
Grommets and isolator pads

Four [4] x 1/4'' id rubber grommets were fitted in the deck, providing an exit for the four lines to be run back to the original location under the co-pilot seat. 

To support the four [4] lines, these are mounted using AN3 (1/4") aluminium hose separator modified to allow a M3 x 35 S/S unbrako securing the assembly to the aircraft with a M3 rivet nut. 

A series of these were used to hold the lines clear the seat belt running under the passenger seat mounted on a 0.020'' x 2024-T3 folded bridge under the seat.

Hydraulic pump with protective cover

Propellor controller is located in the pump's old location

Lines from pump loose on rhs
Hydraulic lines and supports will be covered
in a separate blog

Comment
Not the preferred option, but it was practical at this time mainly due to access to the skins secured in this area and will meet a goal. Doing it again, the pump would be mounted behind the baggage compartment, especially if using lightweight batteries again.

The actual hose runs came out better than they should have, as it was all done on the fly.

PS:  Most of the blogs are prewritten to provide a plan of attack, and the seat belts were very difficult, especially the shoulder straps and have been redesigned numerous times, so text from previous thoughts [plans] were still left behind - fixed.

Hydraulic hoses

This blog covers the technique and material used to assembly the hydraulic lines and fittings supplied with the kit. 

Installing Hose Ends

The lines are fabricated from a teflon line covered in a S/S webbing. Cutting this material was is difficult without the factory tool. 

The area to be cut was wrapped tightly in two ]2] layers of masking tape, placed on an aluminium bar then cut with a 25 mm wood chisel and 12 oz hammer. The end is crushed by this operation and is rounded using a pair of flat nose pliers. 

At this point it is critical that the nut be fitted over the hose if the mesh flares just slightly it proved impossible. The nut was rotated over the tape and once fitted the tape was removed. The end was flared using a sharp pick and the nylon dressed square and finally the ferrel was fitted, tapped on using a soft hammer until flush with the end of the tube.

The nut is moved forward then checked that it will rotate freely in its maximum forward position without being fitted.

Brass Ferrule fitted

There is no slippage once the nut is tightened so connecting fittings straight to straight proved impossible.

Straight fittings are fitted first by tightening the nut onto the fitting while allowing the hose to rotate freely, next at the elbow end a dry fitting is conducted. The fitting was wound in by hand until it bottoms, if it did not align with the mounting position the nut was rotated until this was achieved. 

The fitting is now removed with the nut wound back about 270 degrees and the tread coated with a light wipe of liquid teflon from Permintax. The fitting is now install and wound up tight by hand then finally tightened with a 12 mm hydraulic spanner until the fitting aligned with mounting point. 

If it it did not align the fitting was removed and the nut adjusted again and the operation repeated.

Note: The liquid tape was used to prevent galling and assist sealing

The banjo nut was installed and thread coated with liquid teflon, then torqued using a 13 mm spanner until the fitting will not rotate.

Battery Cables

This blog cover the installation of the battery cables

Overview
The biggest issue in installing a battery in the rear is the cable run .

Installation

Waytech connector

The first issue was to decide on a route, here the current factory routing was copied with the two cables run thru the bulkheads and spars. 

Two [2] firewall penetration studs were installed at selected firewall locations, sealed with high temperature silicone applied to the mounting faces.

Note: the studs were selected for their compact proportions

In the baggage compartment both cables were threaded thru IP65 glands installed into the holes drilled previously in the baggage compartment floor. With both cables in place the lugs were installed, insulated and ready to be bolted to the aluminium buses. 

Note: Lugs were treated with di-electric grease at assembly for increased reliability 

Stock conduit
fitting

Both cables were run through PVC bushes manufactured from screwed conduit adaptors, excess flange was machined off, then installed at the rear spar penetration and forward bulkheads. Exits from the main spar were installed as supplied and used to capture the ends of the split conduit. 

Additional supports were manufactured using 20 mm snap-in bushes fitted into 0.040 2024-T3 aluminium brackets with particular attention paid to the active [+] where it runs under the rudder floor plates. 

The active cable was covered with fire sleeve as it runs parallel to the fuel lines with the earth supported in a similar manner on the starboard side but without fire sleeve

Termination at firewall

At the firewall 10 gauge cables were installed on the inside from the studs to terminal strips that provide active and earth for the the cockpit area. Main connections points are equipped with colour coded insulated boots.

Rear spar penetration

Active

Cable Lugs
Lugs were crimped and soldered at the end to ensure reliability.

Comment
The cable installed was two [2] gauge supplied in error, Flying Legend recommend a minimum of 16 mm squared [ 4 gauge]. 

The run is about 10 feet with the blue line showing a maximum current of about 160 amps allowable over 20 feet = acceptable. The Rotax starter is a 1 Kw motor so 1000 / 12 = 84 amp and as a general rule an acceptable design load is twice [2] its load current for a few seconds so a design allowance is 160 amps, so two [2] gauge is gross overkill but was installed as aluminium construction makes it about the same weight as copper 4 gauge and it was on hand.

Why - I was not loosing weeks fixing an error.

Snoopy happy.

Seat Belt - Part 1

This blog will cover installation of the seats belts

Overview 
The seat belts used are Christian 2'' aerobatic 5 point harness out of the the storage box.

Spinal Compression
This is a touch pad for the aviation governing bodies in Australia especially loads that result in spinal compression by the shoulder harness that must be transferred into the aircraft structure.

Got it wrong
Lucky boy...!

Note: The FAA requires a minimum 9 g design load with a 60/40 split is applied the lap and shoulder straps to estimate loads. A design load of 10g with a 1.5 safety factor was used in the basic calculations. 

Revised factory roll bar and lightweight seats

The current aircraft features new seats and roll bar design that address the issue. I chose not to address this issue before installing the roll bar as a lot of work was being done by the factory will be duplicated but the shoulders harness are now a unique issue to this project.

The supplied with this kit were manufactured from vacuum formed shells with a filler sandwiched between the two halves, well that my guess as when cutting through the white filler its smelt like an automotive filler, this method is used to create vanity and baths and appeared familiar to me. What this meant that the seat belt did not have a definable load carrying characteristics and if quizzed I needed a plausible defence.

Seat Belt Attachments

Welding a new spreader bar into the existing roll bar was examined but as it cannot be removed easily and a TIG welder in a country town is a hard to find, especially if they have to come a remote airfield for two small welds.

A shoulder support was developed consisting of two [2]  1'' x 1'' x 0.625'' 2024-T3 RHS riveted to an 0.080'' plate fixed to the existing seat bracket. A folded 20 x 65 x 0.080'' 2024-T3 angle was riveted to the top side to carry the belt loads into the RHS. The RHS frame was stabilized using the roll bar spreader and a commercial 20 mm saddle clamp. 

Finally the seat was bolted at four [4] places to the RHS using M6 rivet nuts installed into the RHS and fixed with Unbrako dome head screws using 1/8" x  30 - 2024T-T3 aluminum washers.

Shoulder support for pilots seat

The shoulder harness frame was attached to the main spar using two brackets fabricated from 0.08'' 2024-T3 aluminium sheet riveted to the existing frame with five [5] 5 mm od pop rivets.

Note: Building a seat frame was not the original intent but that is where it landed

Both lap belts were attached to the face of the main spar using existing mount holes at a rib attachment. Lap attachments were fabricated from 50 x 50 x 3 6061-T6 aluminum angle. Next three [3] of the 4 mm rivets were removed from the rib attachment. The centers were marked onto the angle and drilled, fitted to the spar then each hole was reamed using a tapered reamer and battery frill secured with AN3 bolts.

Pilots lap belt attachment to main spar

Finally the crotch strap was fitted using a tapped hole now located in the rear seat spreader with the belt feed through a slot provided in the seat. 

Note: The rear attachment was required as there was not enough length when attached at the front as previously decided.

Rear Seat
A slot was cut thru the bulkhead to allow a 22 x 3 mm 2024-T3 bar to be installed. This was fixed at the rear using 7 x 4 mm rivets pitched at 20 mm.  A 0.020'' 2024-T2 doubler plate was installed to tie the attachment to the rear baggage compartment bulkhead.

Shoulder harness stiffers baggage compartment.
Stiffeners fabricated from 0.020'' 2024-T3 sheet

and the channel is factory longitudinal member

The front bulkhead was reinforced using a fabricated 60 x 12 angle from 0.032'' 2024-T3 sheet. This was then profiled and riveted to the top side of the existing bulkhead with a 0.040 2024-T3 doubler located at the front to increase the bearing area and reinforce the exit point.  

A 6 mm stainless steel bow shackle is installed to allow attachment of the seat belt harness. A quick release attachment was fitted to allow removal of the seat with the shoulder harness.

Rear seat attachment lap belt

Both lap belt attachments were fabricated from 0.080  - 2024 T3 sheet profiled to the drawing and with a suitable offset. The completed brackets were fixed to the stringers using 3.2 mm pop rivets. This attachment is similar to the current factory attachment method.

After installing the baggage compartment cover the harness attachment were inserted then bolted together using spacers at the belt attachment. 

Harness attachment
A major problem designing any connections is eccentricity but in any mechanical structure we use thicker plates with aircraft it needs to be light as practical.

To allow the misalignment to be accommodated, forged 6mm bow shackles were fitted with a weight penalty of about 12 grams each.

Happy days !

Always look at the bigger picture before setting off
Spot the deliberate error!

To tidy up this mess it was decided to remove and create a new skin with the gain being it allowed access to finish the mounting of the battery and pump. Originally it was intended to mount the shoulder strap in a completely different manner but this change allowed the relocation of the hydraulic pump - more later

Comment
Rear seat will be removed when the aircraft fly's to provide access for adjustments to the propeller controller as is now located in the place of the hydraulic pump.

Its done - Its done - Its done
 have mountings......!