[Wing] Inspection Questions was Cherry rivets

[Douglas G. Murray]

Rob,

Remember that 2024-T3  has a pure aluminum cover over the alloy. This is a
primary corrosion protection.While Cessna does some aircraft with no
additional corrossion protection and some builders go all the way with full
secondary corosion protection on all surfaces - including  rivets, there is
a requirement to show the MD-RA corrosion protection. In an metal aircraft
that uses 2024-T3 I would expect to see as a minimum - secondary corrosion
protection between all joined areas of the structure, complete coverage of
the interior of all contol tubes, and all steel fittings and complete
coverage of unprotected aluminum, such as  6061 -T6, and extrusons.
Additional information on this topic can be found in AC43 - 13 - 1B in
Section  10 - 14.

Complete primary corrosion protection is required on tube and fabric
aircraft and on all wood structures.

As to the Borescope question - Unfortunately the present requirements state
that no structure is to be closed without inspection by a qualified
inspector. While the Borescope does present an interesting alternative, it
hasn't at this time been approved. You might want to present the idea to the
MD-RA office in Ontario and see if it will fly.

There is a lot of material on the RV-List about various primers and paints
so I will not address that topic.

Hope this helps,

Doug Murray


----- Original Message -----
From: Rob Prior <Rob_Prior at CreoScitex.com>
To: <wing at vansairforce.org>
Sent: Monday, November 19, 2001 9:13 AM
Subject: RE: [Wing] Cherry Rivets


> Hi Doug,
>
> Perhaps you could answer a question, since you brought up the topic of
> corrosion protection.  What level of protection do you expect to see when
> you look inside an aluminum structure?  I'm just starting an RV-7, and
don't
> plan on priming anything I don't have to (weight saving), just the mating
> surfaces where two parts meet.
>
> Looking inside the wing of my father's Cessna (and other production metal
> aircraft) through an inspection cover, I can see that it's been common
> practise in the industry to not prime *anything* inside.  And I know
> RV-builders locally who are going to both extremes, one priming everything
> and one priming nothing, not even mating surfaces.
>
> So what's expected?
>
> Oh, and one other question, if I were to supply a borescope for my
> inspector, could I close all my surfaces before it was looked at?  I have
> access to such a scope that I could borrow for the purpose of an
> inspection...
>
> -Rob Prior
>  rv7 "at" b4.ca
>  www.b4.ca/rv7
>
> -----Original Message-----
> From: Douglas G. Murray [mailto:dgmurray at telusplanet.net]
> Sent: November 18, 2001 20:40
> To: wing at vansairforce.org
> Subject: Re: [Wing] Cherry Rivets
>
>
> Another area that the Inspector is looking for that a lot of
> builders may forget about is the internal workings of the parts - ie.
> bellcranks and related linkage, wiring and chafe protection, internal
> bracing and fastener integrity, and corrosion protection.
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