Overview
This Tucano requires the builder to drill and ream the spar straps to a 1/4'' after setting the angle of incidence and washout.
In attendance at this time was Franco and Alexandreio Rummolino from Flying Legend in Italy to aid and train this builder ensuring the correct procedures were used on this project and to aid other builder in the future. This is without question a 2 - 3 man operation and under no circumstances try this one up so you will need beer and steaks.
The design of the Tucano wing connections have changed significantly with the upgrade to +6/-3 with the straps being replaced with 2 pins reducing the assembly time to a quarter of that required for the straps but the setting of the angle of attack and twist remain the same.
Mounting Frame
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| Gorilla Work Platforms |
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| Craftright Saw Horse |
A sheet of builders foam was used to pack the deck and to provide a suitable mount for the fuselage onto the stands.
Installation
All spar straps, packers and plates were assembled on a bench to be fixed to the wing with M6 screws using the factory drilled holes and procedures.
The aircraft was leveled using a digital level place across the longeron in front of the instrument panel and then using a length of aluminium channel placed along the top row of rivets on the fuselage side to confirm it was also level
Note: This instrument as a tolerance of +/- 0.1 degrees which is suitable for this application
Google: Digital LCD Protractor Angle Finder Level Inclinometer.
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| Level along the side |
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| Level across Fuselage |
The main spar caps on the Tucano were manufactured using a series of laminated sheet aluminium angles, so before any work can be commenced they had to be cleaned using a combination of brushes and vacuum cleaner to remove all swarf that could included itself between the laminate when the factory bolts were released.
The front rib was removed to provide access for drilling.
Note: All spars now have aluminum extrusions manufactured to replace the laminates but the rules are the same
At this point the factory bolts were replaced with 5/32'' [4 mm] screw clecos to close the spar laminates at two [2] locations then two other holes were enlarged to accept 6 mm bolts. Additionally the internal connector plate was fitted to the wing spar using 1/8'' clecos and then a C clamp to tie it to the rear spar to allow adjustment of the washout at the next step
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| Washout at root has been sent and the holes on the fuselage side match drilled |
Before any work was undertaken clecos are installed to ensure the wing's shape is locked back into the profile from when drilled in the factory jigs, these were placed on about 150 centers along the full length of the spar and the skins to the ribs.
Note: Remove only the first skin to provide access to the spar connection points and do not remove the temporary rivets or other skins at this stage
The wing was inserted into the main spar then secured with two [2] - M6 x 60 high tensile hex head bolts per side usings the factory drilled holes while supported at the tip by the saw horse.
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| Wing Attachment Described superseded buy new design below |
With the wings fitted and the dihedral was checked using the digital protractor and a 1200 mm length of aluminium channel to average out the difference created by a overlapping skin at the same location on both sides. Once the angles matched the pairs of M6 bolts were tightened to retain the setting. The saw horse was relocated then packed as required to ensure the wing could not slip at the connections.
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| Setting dihedral |
Washout
The twist was set using the rear spar straps and two [2] clamps per side in conjunction with jigs manufactured in 6 mm perspex.
Note: There are six [6] x 11'' C-Clamps required for this and other tasks on the wing - these were purchased on EBay and were of a excellent standard for the money
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Setting Dihedral |
Both angles were rechecked to confirm no change from the tightening of the bolts
Note: When checking and setting the angles specified the most important number is the two that match with reference to the tolerance of the protractor. If found to be floating between two values adjust to achieve a steady value
Setting Washout
The next task was to set the washout using jigs manufactured here from factory DXF files and 6 mm perspex that worked extremely well on the day.
There are two jigs, one for the root and one at the tip. Zero the protractor of the fuselage datum and then rest one jig on the rib profile and with the two notches aligned with the front and rear spars.
Note: The procedure and location must be the same at both sides - the most important outcome is not the angle but that they are both the same.
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| Setting washout |
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| Setting washout at root |
With the jig on the the angle is checked and adjustments were achieved with a firm but technically correct hand thump on the top of the spar at the fuselage intersection.
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| Mission accomplished |
Aligning Wing to Fuselage
The final task is to check the alignment of the wing tips, This was done with a tape measure, three [3] people, two [2] to hold the tape plus one [1] person to support the tape in the middle.
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| Alexandreio, Joe [translator] and Franco checking the diagonals |
Final Check
After all the adjustment recheck all the previous settings then one final check to confirm the numbers then drilling could commence.
Drilling
The next task was to remove the temporary 6 mm bolts one at a time - 6.1 / 6.2 / 6.3 mm and then ream to 6.35 [1/4'']. Two holes were prepared in the outer wing panels and bolts inserted using a with a soft hammer, next this task is repeated on the fuselage connection and bolts fitted.
Note: Only one bolt is removed at any point and no additional work is undertaken until it is replaced and the bolt hand tightened
As each hole was drilled a AN174 bolt, MS21042 nut and washer was installed and lightly tightened by hand. Normally bolts are placed fore to aft but in the case of the spar straps the rear bolts are to be install with the nuts visible in the wheel whell for inspection.
After coffee the diagonal was checked again as was the dihedral. Once reconfirmed all the holes in the outer panel were drilled. At this point the comment can be made that the material used for the straps is as tough as anything that I have ever encountered using hand tools.
The bolts on the fuselage still have four [4] bolts to complete and this is done when the wings are to be installed for the final time after painting.
Both wings were now placed on a pair of saw horses and the twist checked with the jigs. The work here will be covered in a separate blog.
Note: All bolts are lightly nipped and will at installation be torqued to specification using a calibrated torque wrench - Never guess the torque as the required amount is a light nip and unless you have a lot of experience use a torque wrench - professionals do not guess.
Comment
Firstly the Ozito battery drills clutches were not man enough and this required a quick trip to the local hardware to purchase a new electric and battery drill. This was further complicated when a drill broke in one of the inner fuselage holes required a couple of hours tapping, spraying and sweating to remove by an experienced team from the factory - Oh Joy..!
In fact the last six [6] bolts on the port wing were done in about the same amount of time with the all the tasks taking about
Why point this out well the new aircraft do NOT use straps just four [4] pins and the image below shows how much fun you will miss out on.
I have tried to document this a closely as could be done after the event but the manual rules and should be read as the only source of all procedures - OK..!
I have tried to document this a closely as could be done after the event but the manual rules and should be read as the only source of all procedures - OK..!
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| New Wing Attachment |
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