When you add floats to a tricycle gear (e.g. Beaver) do you need an STC to install the TSO'd floats? Or can this installation be approved with a Form 337 for a single aircraft?

  • $\begingroup$ I don't have all the references so this is not a complete answer. An STC is a modification that has been "pre-approved" by the FAA Administrator for a specific make, model, and sometimes serial number of aircraft. An STC meets - "minimum standards for the design, material, construction, quality of work, and performance". A Form 337 is an application for a modification that is not "approved" so the applicant must show it is airworthy and meets the necessary requirements for being added to an aircraft. faa.gov/documentLibrary/media/Advisory_Circular/AC_21-40A.pdf $\endgroup$ – jwzumwalt Dec 15 '17 at 0:06
  • $\begingroup$ It is possible that a logbook entry is all that is required. $\endgroup$ – acpilot Dec 15 '17 at 1:36
  • $\begingroup$ @acpilot I suppose you might be right, but switching to floats certainly seems to be a major alteration. Or perhaps you are considering an aircraft that is already certified for floats? $\endgroup$ – J Walters Dec 15 '17 at 13:30
  • $\begingroup$ Yes, already certified. $\endgroup$ – acpilot Dec 15 '17 at 13:54
  • $\begingroup$ I am assuming the airplane is not already certified for floats. Therefore I don't mean a plane that is already certified for both land and sea ratings with the option to switch back and forth between wheels and floats. Instead I am referring to a scenario where I buy a C-182 and want to place it on floats. I buy some TSO floats (e.g. whipline, edo etc), but however the "approval" to install those floats on the airplane is a? Would it be an STC or Form 337 or could it be either? $\endgroup$ – Greg Dec 15 '17 at 16:13

This sounds like a major mod, but I will have to see the design data to really able to come to a conclusion. If its a major mod, it has to be done via an STC.

  • $\begingroup$ Where would I find the documentation you are referring to that a "major modification" should be installed via STC? $\endgroup$ – Greg Dec 15 '17 at 16:16

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