"Andrew Gideon" wrote in message online.com...


Ah, so a PMA is aircraft-specific?

No. PMA ce

I'm confused about the role of a 337. When is one required?

A 337 is required to report any major alterations whether the are supported by
an STC or just "other acceptable data." Some people sometimes use "approved
by 337" to mean field approval.

One example is what you've cited: a change for which neither PMA nor STC
exists. But is one required for a replacement with a PMAed "part"? Is one
required for an STCed alteration?

There are two principles he

1. Approval of the modification, that is authority to make this change to the aircraft.
2. Approval of the part itself (It's manufacture, quality control, etc..).

The first is accomplished by either being supported by the Type Certificate, or an STC,
or other approved data, or being so minor as being inconsequential.

The second, can be accomplished by a PMA, a TSOA, the type certificate itself (for the original
manufacturer), by recognition of certain non-FAA standards (like MilSpec's for things like fasteners),
or by the owner himself producing the part in accordance with FAA-approved data.