Filtered Air Box Maintenance and Repair
Over the past 3+ years that I've been flying there haven't been
too many maintenance issues with the plane at all, but recently some
people started to talk about one possible one. Thanks to David
McNeill, I took the time to recheck my air box and found I had a
problem. The problems are these:
For the issue of the filter rubbing through the air box, all I
can see as a good fix is either line the bottom of the airbox with a
thin aluminum sheet riveted and epoxied in, or make the air box fit the
filter snug enough so that it doesn't rub. Mine was pretty snug.
When you stuff the filter under the metal plate, it is pushed in pretty
good. I did have a very slight ring in a couple places where you
could tell a tiny bit of wear occured , but not enough to warrant doing
anything about it at this time. I'm nearing 500 hours, and if it
keeps on at the same rate, I'll be able to change it at TBO or
something. If I need to do something sooner, I'll bond in some
- For some builders, the air filter is rubbing through the
bottom of the air box fiberglass.
- I would be that for MOST builders, the rivets that are put
through the fiberglass alone won't hold up.
The issue that caused me my problems was that the alternate air door
that rivets to the bottom of the airbox wasn't installed with any
internal doubler. This is a definite oversight in the design, as
you really can't expect those rivets to hold long-term in
fiberglass. The fix is simple though...just cut a ring of
aluminum...I used .050 aluminum, and make a doubler that you can then
rivet to the inside. I added a couple of extra rivets, as well,
for more security, and I used standard AN4 countersunk rivets. It
wasn't a hard job, but if you're still building, just do it right from
the get-go and you'll be happy you did.