Fuselage Firewall Part 1

Australian Experimental Category Overview
The factory aircraft has a aluminium firewall and wheel well. Certified aircraft must be protected by a suitable fire proof barrier but there are no standards for an experimental aircraft. Lack of fire protection to any recognized standard may result in a limitation's begin placed on the aircraft by the Authorized Person certifying the aircraft in Australia.

"It is up to the Authorized Person (AP) inspecting the aircraft as to what limitations they will place on the aircraft based on their assessment of the aircraft. The AP is required to issue a C of A but has to take into account possible effect the lack of a firewall could have on other aircraft and third parties on the ground. 

The AP would possibly place a requirement in the Certificate of Airworthiness Annex for all persons being carried in the aircraft to be made aware of the lack of a stainless fire-wall or other more stringent conditions on its operation"

In a meeting with my AP I was advised that the builder is free to do what they want BUT if there was no firewall he would have to look at what threat this would impose on third parties on the ground in the event of a fire.

It was decided by this builder that a firewall would be a good idea from an operational point of view

Firewall
Steel is the most common selection with stainless the preferred choice having a minimum thickness of 0.015'' [FAR 23.1191]. The material chosen was 304 Half Hard supplied by Master Cut Technologies, Melbourne. The correct size material is available but it was felt the it would have not have been stiff enough.

The disadvantage is that the replaced items are 3 times the original weight in of the aluminium components.

No.!

Wheel Well
The wheel well was originally to be lined with Firewall 2000 Ceramic Blanket purchased from Aircraft Spruce. The weight on their site stated as 0.9 oz per square foot but when it arrive it felt like a lead vest. A check on the manufacturers data sheet revealed that the correct weight is 1.85 lbs per square foot creating a heavy and expensive ouch..!

It was now decided to replace the wheel well wrapper with stainless steel fabricated from 0.020'' 304 half hard stainless steel. 

Sealing
A firewall also has another job, that is to keep as far as practical fumes from  entering  the cockpit. All the seams will be sealed using Permatex High-Temperate Silicone Gasket Maker  [ -50C to 340C range]  before installation of the new firewall.

Fuselage Floor Plates Part 2

Co-Pilot Floor Plate
Drill the floor plate at 60 mm centers using the factory supplied jig. Fit it to the top of the longeron and match drill two holes, fit clecos and finish the balance. Remove floor plate then de-burr holes.

Refer notes: Fuselage Floor Plates Part 2

The seat brackets sit on top of this plate so all holes are countersunk except the last two at Station #3.

Entry Bracket
The bracket required to mount the foot entry was not picked up on the initial reading of the plans and at installation it was noted that the mounting holes will require riveting to the top flange of the support angle. This places the removable floor plate on the top side of the bracket, so it will have to be joggled to fit this installation. The piece marked on the photo to be trimmed will be cut from the bracket to allow a straight joggle.

Position the bracket and mark it's location onto the top side of the port removable plate. The floor plate will have to be trimmed and drilled to these reference marks to fit inside the bracket profile. Cutting off the existing return and drilling a clearance hole for the circular mount allows the plate to fit the bracket.

Locate bracket with floor plate fixed in position on the longeron, drill two hole's into bulkhead at Station #3 locate the bracket.

Remove the floor plate, drill a hole through the flange of the angle to allow the step to be inserted into the bracket. 

Match drill holes into the angle faces from the bracket, countersink and rivet. 

Match drill all the holes into the bulkheads and pop rivet. 

Check the floor plates and adjust to fit inside the perimeter of the bracket then joggle to fit.

Insert the mounting shaft into the mount from the top side and mark its location onto the flange of Station #3, then trim to clear. This hole will have to be replicated through the skin before its final installation.

Trial fit of bracket

Note: An alternative would be to reduce the overall length of the angles allowing the bracket to be installed matching the top-side of the angle. 





 Joggles in Aluminium

About Blog

As the current Australian Agent for Flying Legend and the builder of the first of type this blog is a part how to manual and record off construction. This should explain some of the strange mix of tenses trying to separate the two necessary styles of writing. This that will be no comfort to those versed in the fine art of the written language so please bear with the writer as I am more Engineer / Technician than author. 

All posts are re-edited once posted until they make some sense - so it you read a early post go back later it may make sense later. At times a few personal touches will appear in the moment with a touch of humor but with a lot of truth.

So please read the information and draw your own personal decisions and it's hoped some of the information will be of value.

Have fun

Gary

Refer Disclaimer

Joystick Lock Wiring - Part 3

After ensuring that the joystick assembly is operating smoothly the last task is to lock-wire the collars fixing bolts. As noted this builder had problems drilling the supplied stainless steel screws successfully so steel Unbrako M5 x 10 screws replacements were sourced.

Drilling screw heads

The screws were fitted to a machine vice and a pilot drill was used to create a start for the 1.5 mm drill. File a small flat to help the pilot locate itself on the head - locate the hole close to the base of the key in the head. Select a medium speed on the drill press to drill holes for the lock-wire. 

Note: Apply oil to the job as the bolts are high tensile and the drill tip must be kept cool and lubricated. This builder broke a number of drills during the process when hard spots were encountered. If this happens heat the head at the hole until  red hot then place aside to cool naturally. 

Use good quality drill as this may have been the original issue with the stainless steel screw's but stainless steel is very hard to machine.

Lock-wire Bolts

The bolts are secured with stainless steel lock-wire in pairs across the collars. This method was selected as it secured the wire around the head and prevented slippage. Cross drilling the head at 90 degrees would provide the builder with more options and should be considered.

Rob Carpenter video on lock wiring is an excellent place to start.

Comment: See article on pump installation before fitting lock wires

Fitting lock-wire correctly is a true skill that requires practice to get right - Got a long way to go

Fitting Lock-wire

Fuselage Floor Plates - Part 1

There are 6 floor plates to be installed into the Tucano for the Pilot and Co-Pilot. Some are removable and others are fixed - refer manual for details. Each plate should be clearly marked as removable or fixed.

Pilots Fixed Rudder Floor Plates
The plates were marked out to place the mounting holes on the center line of the longeron with all holes drilled 1/8'' [3.2 mm] at 60 mm centers using the factory supplied drilling jig. 

Position plate by aligning with the end of the wheel well at Station 2 - match mark two holes onto the longeron centerline - drill and cleco. Match drill all the holes on both sides, remove the plates and de-burr. A 12'' long #30 drill makes this task possible with a large battery drill and are available from Yard Store in the USA  -  get a range they are well worth it.

Hint: The aluminium used for the floor plates produces pronounced burrs but a small painters stainless steel scraper with the corners rounded and just a hint of rake on one side is "truly  excellent"  at removing them quickly.

Cleco both plates back into their location and mark the center line from the cutout in the wheel well. Remove and locate the reinforcing plates equi-spaced about this center and match drill. These are machine punched and will drill correctly from either side. 

Place on the underside of the floor, pop rivet with the taper to the fuselage side.

Temporally re-install with clecos.





Pilots Removable Floor
The holes for the two removable plate's located between Station 2 - 3 can be marked out and drilled at 60 mm using the factory jig but decide were to place the last odd hole - all holes are drilled 1/8'' [3.2 mm]

Hint: Tape all open edges between mating services and anywhere a crevice is created to prevent ingress of swaf. A large amount of swaf was trapped on this install between the wheel well and the longeron with removing the rivets the only way to release the swaf.

Floor Supports Angles
There are a number of angles required to support the removable panels at Station 2 - 3 and are fabricated using the 30 x 30 x 1 mm angle supplied with the kit. 

A level was used to establish the height on Station 2 at the fuselage side using the top side of the longeron as the reference. The mounting holes in the angles were drilled at 30 mm centers using the drilling jig then the station former's match drilled.

The bulkhead Station 3 require's support angles at both sides for the pilots and co-pilots floor plates. 

There is a 15 mm height difference between the pilot floor and the co-pilots floor and on this install a deeper angle was installed at the co-pilot side to allow fixing to the bulkhead. Even lowering the rivets by the required amount the stems just cleared the underside of the flange on the pilots side. [See image below]

Note: If doing it again install the co-pilot angle with the pop rivets say 7.5 mm from the top of the angle. Install the pilot angle drilling through pre-drilled holes to ensure that both are held tightly onto the bulkhead. On this install Teck screws have to be installed to achieve the same result. 

Install the middle plate and position the removable plate, match drill from the outer removable plates to provide the two holes in the longeron, cleco then match drill the plate and longeron with the factory jigs. 

Enlarge holes to 3.5 mm to allow easier re-installation.

Trim panels as required to achieve an acceptable fit

Note: To undertake this work the temporary rivets for the lower skins have to be removed to gains access.  Do NOT  match drill floor plates to the bulkhead or angles at Station 2 - 3 as this locate's the bulkheads without reference to the mounting holes for the skin. 

Fitting Riv-Nuts
Install M3 riv-nuts for the removable plates into the longerons, all the holes have to be enlarged to suit, fit factory supplied supplied nuts then reassemble using with a few M3 x 10 screw's, check the fit and adjust as required.

View Starboard Side Station #2 - 3
Note: 1/2 x 1/2 angle stiffener and double row off rivets to mount angle supports for pilots and co-pilots floor supports. The holes in this installation are at 30 mm when drilled in error - 60 mm is correct

Adjust the pilots fixed panels folded edge to align with the skin - this can be done with a straight edge held on the bulkheads - packers may be required when these are riveted to the side skins - the key here is to get the angle right. This can be achieved using a block of hardwood with a slot cut into it by bending the edge along its length [it works] - refer video link below.

The bulkhead flange on Station 2 supports one side of the pilots floor plate. On this installation it was found that a couple of aluminium washers were required to align with the removable plates. These were super glued onto the under side of the plate and holes drilled to suit 5 mm aluminium pop rivets. 

Note: To use smaller rivets custom washers would have required  washers machined to suit.

Modifications
The removable floor plates were reinforced with two [2] 1/2 x 1/2 x 1/16 - 2024-T3 aluminium angles running  fore to aft as the factory floor plates seem a bit flexible to take my full weight on entry. It should be noted that the fixing screws and skins were not fitted at the time.

Footnote: The only problem was this tool using the drill forgetting to stop at the pilots fixed plates as they were not marked "fixed" anywhere. With a long day and the before mentioned tool now running in Derrr mode, all the pilot fixed holes were enlarged only to be discovered when the drilling stopped.

Refer opening note on marking plates. The panel were fixed using 5 mm pop rivets but that was more good luck that anything else...!

Pilots Floor Plate Station #1 - 2 Port Side

Pilots Removable Floor Plate - Station #2 - 3 Port Side

Removable Floor Plate
Holes were pitched at 30 mm, every second hole opened to clear the heads of screws in the lower plate allowing the middle plate to be removed independently of the others. The factory hydraulic hand pump is located under port removable panel.

Flange Bender Make your Own