SERVICE BULLETIN SB 16-03-28 adventures [5.5 hours]

Carrying on from the previous post on this matter – here – I completed the replacement of the left wing aileron bracket, again with no dramas. I then did a trial fit of the left aileron, and immediately ran into problems. Big problems, in fact.

The new bracket is much “wider” on the base than the old bracket, adding 1/8″ each side of the main bracket structure, due to the use of 1/8″ angle for mounting to the rear wing spar. The AN470AD4 rivet manufactured heads, when added to this 1/8″, remove all clearance previously available for the aileron to swing freely, and so the aileron with the standard spacer/washer setup (per Figure 1 on page 21-10 of the construction drawings) now rubs across the top of these rivet heads – see the attached pictures.

I contacted Van’s, and they suggesting changing the washer/spacer arrangement to move the aileron outboard. I tried this, but with only 3/32″ between the outboard edge of the aileron and the manufactured heads of the rivets on the outboard bracket, there just isn’t enough room to solve the problem this way and still maintain reasonable spacing between the sides of the aileron nose and the rivet heads.

So, I contacted Van’s again, and asked them if it would be acceptable to replace two of the existing AN470AD4 rivets with AN426AD4 rivets. Van’s response was as follows:

Using the 426 rivets should be no problem if that is what works best for you there. The bracket is more than thick enough to be countersunk and the rivet strength is the same.

The only problem then is how to actually do it, since the brackets were already installed on the wings and these are very long rivets. I used a long 3/32″ drill to carefully drill out the rivets,  and a 3/32″ punch to drive them out. Countersinking was easy with a right angle drive bit. I didn’t actually have any AN426AD4 rivets that were long enough, I had some -9’s but these were too short. I went looking in the hardware of the slow build fuselage kit, and found a bag of ten AN426AD4-16 rivets, so I stole a couple of these and used a rivet cutter to trim them to the correct length. My guess is the right size would be either AN426AD4-10 or AN426AD4-11. The new rivets were easy to set with a pneumatic squeezer and 4 inch yoke.

The aileron now swings freely without any problems. The pictures show the standard spacer/washer arrangement. When it comes time to do the final rigging, I expect I’ll shift the aileron by one thin washer width, to even up the clearance gaps on the inboard and outboard sides.

Now I have to go back and do the same change to the right wing bracket. It would have been sooooo much easier to have installed AN426AD4 rivets in these positions in the first place.

August 11 update: I did the same with the right aileron bracket, no issues and quite a bit faster the second time around. I’ve added some pictures covering this change.

  • w54a
    Trial fit of left aileron, after replacement of aileron bracket
  • w54b
    Inside web of aileron rubs across rivets on the new bracket
  • w54c
    Aileron alignment is OK, gap is 0.17" - a bit lower than the nominal 0.25"
  • w54d
    Preparing to drill out AN470AD4 rivets. Damage on rivet heads is from aileron scraping
  • w54e
    Rivets punched out
  • w54f
    Old rivet shanks after drilling and driving out
  • w54g
    Set up for countersinking holes
  • w54h
    Holes countersunk
  • w54i
    Set up for squeezing AN426AD4 rivets
  • w54j
    AN426AD4 rivets in place
  • w54k
    Aileron now swings freely. Probably needs one more 416L washer spacing to balance up inboard/outboard gaps.
  • w54l
    Another view of replaced rivets
  • w54m
    Old bracket held in front, showing how the new bracket has 1/8" less clearance inboard of aileron
  • w54n
    Now I have to fix up the bracket on the right wing...
  • w54o
    Rivets drilled and driven out of right aileron bracket
  • w54p
    Rivets drilled and driven out of right aileron bracket
  • w54q
    One perfect drillout, one that impinged a bit on the hole but OK
  • w54r
    New rivets in place
  • w54s
    Rivets set
  • w54t
    Right wing aileron hung
  • w54u
    Same fit as left, needs to be shifted outboard slightly but OK for now.
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