Elevator - Upgrade

This blog covers the work to install stiffeners for the elevator bell-crank and discovering a hidden error.

Overview
Flying Legend asked me too install two [2] angle stiffeners at the rear bell crank which are now incorporated into the current air-frame, after inquiring on method they advised the best way was to remove the elevator stab. 

Installation
The first task involved removing the fairings, rudder, fin post and to expose the deck plate. 

All pop rivets were then removed followed by both deck plates and finally the bell crank to allow installation off the new stiffeners plus installing bushes into the bell-crank. All the new brackets were alodined and a trial fit showed the rivets on the original brackets attaching the bulkhead and stringers would now foul, so new brackets were required.

These were fabricated from 0.040'' 2024-T3 to allow countersunk rivets to be used which solved all the interference issues, these were alodined, riveted into position and another trial fit undertaken.

Note: This was an upgrade and the current air frames are fitted with these components

With all problems now solved the bell-cranks were reinstalled and it was at that point the rear spar attachment came into clear focus - one mounting hole was a figure 8 and the other only slightly better.

How 
The cause was forgetting that the factories had pre-cut in the attachment point through the deck plates at the stab installation, so both deck plates were clecoed back into position until that day.  [see below]

Why

As delivered

Many months passed assembling the fin, rudder,stab and elevators then finally the time arrived to install the components.

With the deck plates in position and displaying blank flanges visually reinforced a decision to level the tail plane so holes were marked onto the flanges allowing the components to be matched drilled after levelling the stab .

Note: These plates were riveted in position before commencing the match drilling further compounding the error

Santos from Flying Legend's insistence on removing the deck broke that error chain - this issue was not detectable, as both external holes appeared perfect and no inspection at the end of this project would have picked it up.

Note: The factory manuals have been upgraded  since my purchase now supplying assembly instructions based on the factory's own manufacturing procedures, The rear attachment requires it to be reamed and bolted up. 

Extract of information from new manuals supplied with kits
these are very detailed and cover the correct sequence of assembly 
with notes, 3D images and photos where required.

PRM = "Please read manual"

Fix
The first task was to remove the the stiffeners attached to the bulkhead and they had been solid riveted. Without putting too fine a point on it, many hours were spent removing these six [6] rivets with the final method required the flared end to be ground back using a Dremel Motor Tool and drilling holes through the rivets until the reinforcing plates could be freed.

Note: On examination the rivets were fused to the bulkhead material at their junctions  - interesting

With both plates removed the front plate was salvaged to be used as a drilling template. New plates were cut using a scroll saw and finished using a combination of power sander and hand files. Finally all edges were then polished using 400 grit aluminium open cut paper. 

The factory they sent photos of the current installation for clarification and it showed the rivets were now five [5] off per side and all in a straight  line - done - scrap the first one. A quick referral to the new manual and drawings allowed a new profile to be developed.

New stiffeners - red stuff is blood - mine 

Stiffener finally in position
A packer [2 mm] was placed under the lower attachment point

Current factory installation

So more sawing, filing, sanding and alodine treatment  there was a new set of stiffeners. The  bolts were fitted with clecoes in the original holes, finally all the rivet holes were drilled to 5/32'' to ensure clean holes. Not having a riveter Steve from the hanger down the row stepped up and gave me a quick lesson on riveting solids.

Note: This was done twice as I was not 110% happy with the first brackets and decided to upgrade to match the current factory arrangement as it allowed better access for riveting than the original shorter plate.


All swaf was removed and the stiffeners reassembled and the rivets installed.

Steve - Rivet Gun for hire
Thanks

Comment
When this blog started it would cover the good and bad this had the potential to be bad.

The rear attachment was upgraded with the fin attachment stab plus the work described.  Thi simple error created 30 hours plus in rework, re-manufacture of plates, fitting and refitting - hand work combined with the fear of compounding the error is not a fast way to work.


Closing this chapter a line from Forrest Gump comes to mind "stupid is as stupid does" -  so God is forced to cover stupid -  this would have never been seen by any inspection - I mean never.

Stupidity is not a excuse