Monday, February 05, 2007


Control System

The control system in the centre fuselage is almost complete. The points to note are:

1) Earlier on this blog - see Jan 12th '07 & July 8th '06 entry - I considered making the F-449 bracket so that it moved the stick further forward. In the end I have used the bracket as defined by the plans, but added a 1/8" shim between the bracket and the tie bar. This has moved the aileron pushrod tubes forward so they are almost central fore and aft, with respect to the pushrod tube hole in the sidewall. Making a firm decision regarding this, enabled me to match drill the 4 bolt holes for the rear mounting point of the stick assembly, in the centre of the picture.

2) I still have to increase the clearance of the push rod tube as it exits through the side skin. It is not blocking full movement as the rod gets to the limit of its travel but it is just touching. You can see this in the picture. With the stick fully over to the left the RH push rod tube just touches at the top of the exit hole. If I relieve this by 1/16th to 1/8th, that will cease. It is the same on the left side.

3) I have had to grind quite a bit away from the hole above the rear spar, to ensure it does not touch, as you move the stick from side to side. I have an extra heavy bracket here to permit a 5th point for the PAX harness. I may need to grind a bit more off yet, to be sure it does not touch.

The flap mechanism went together quite easily, though the stressful bit lies just ahead; cutting holes in the exterior skins for the flap push rods.

Here is another picture of the fuse centre section.

Postscript - 12 May 07

For completeness I have added a picture of the manual aileron trim unit.

The way it works (I think) is so.

The stick runs through the centre of the UHM block. The RHS long screw serves both to clamp the unit to the stick, as a pivot for the trim arm (green) and to provide some friction in the system. The LHS screw increases the friction in the trim arm. The springs attach to the lower part of the trim arm and the other ends to the sides of the compartment in which the stick is located. I presume some locking wire is used to adjust the length / tension.

So if you move the top of the trim arm to the left, the left spring tightens and the stick is offset left.

(If you click on the picture you can get a bigger one, which will enable you to see more detail.)

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