Installing an O-200
 in an LSA Ercoupe

(415-C or 415-CD)

Installing an O200 (or any other engine, for that matter) in a 415C [or 415-CD] does not in and of itself have any effect on the model designation or LSA eligibility.  It may, however, affect [legal] airworthiness.

The only STC for installing an O200 in any Ercoupe applies only to the 415-D. However, installing the engine and filling out the 337 referencing the STC still doesn't make the plane a D, even if the 337 references a conversion to model D.  It makes the 337 invalid. (Refer to the following paragraph).

The only way a 415-C or -CD can be converted to a D is by having an airworthiness certificate issued stating it is a D (among other things).  Registering it as a D is not sufficient, and is easily done, accidentally or intentionally, but, without the airworthiness certificate, is incorrect.  Incidentally, no 337 is required as the conversion is covered in the Aircraft specification. Any modification listed in the Aircraft Specification is, by definition, a minor modification.

The only way to legally install an O200 in a 415-C or -CD is by field approval.  Conversely, any installation that does not have a signature and stamp of approval in Block 3 of the 337 is not a legal installation. 

The most straight forward way to get an O200 installation approved for a 415-C or -CD from scratch is probably the following: 
1) Have your IA run this by the FAA first.  Get the stamp and signature in block 3.
2) Install the STC for the 1320 lb gross weight. This makes the plane aerodynamically identical to a D without affecting the model designation or the LSA eligibility.
3) Install the O200 in accordance with the data for the STC'd installation of an O200 in a 415-D.
4) File the 337 with the field approval.


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