STCs and 337s

  • It seems that the Ercoupe airframe stalls around 45 knots at a gross weight of 1320 pounds. With this STC, you are getting the most as an LSA pilot.
  • Univair holds a STC for metal covering the wings.

Wing metalize STC

  • The conversion to a Skytec electric starter, discarding your DELCO pull cable starter.


  • ternplate header tank - replace with aluminum tank.
  • Shoulder harness installation
  • cleveland brakes STC SA 120 GL
  • cleveland brakes 337 for serial numbers lower than 817
  • INSTALLATION of MODEL - E ELEVATOR, Battery master, Nose bowls and more
  • Bill Coons Low tail height - Now alpha aviation
  • engine mounts - use inserts in O-200 to convert to C-series engine mounts.
  • Cessna Seats & Large Baggage Compartment
  • Side door installation
  • Autogas (Mogas) STC and Flight manual extension
  • Skyport big baggage compartment STC


  • Kenny wheel fairings STC and instructions


  • SBS J-16 FAA approved ODYSSEY Drycell small aircraft battery


Differences between a STC and a 337
337 is a form used to report a major repair or major modification. A 337 must be supported by approved data. An STC, a field approval, or a DER's work product are approved data.
To get a field approval, the AI (or A&P) puts together a packet of acceptable data and sends it off to the local certification office. If they deem it justified, they will issue a field approval and fill block 3 of the form 337. Static limits from similar airframes with the same engine and prop would constitute acceptable data, as would specific recommendations from the prop manufacturer.
Documented flight test data is also acceptable data, but you must have approval to conduct the testing, and put the aircraft temporarily into the restricted or experimental category

John Cooper