Radio TSO requirement

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It's fully up to you to check any information you find here with
standard aviation industry sources such as aircraft maintenance
manuals, flying instruction books and, above all, FAA regulations!

By Linda

Here's what I've learned from several reliable sources on non-TSO'd radios; nice that it's all starting to converge, finally.

I remain surprised that to date there doesn't seem to be an authoritative -- much less a comprehensive -- article addressing this subject.  I suggested such an article to Mary of the EAA magazine, and she said she will consider doing a published article, clarifying all this.  Ditto when I talked with Rodney, the A&P in AOPA's Aviation Dept., that AOPA will consider it, too.  

All of the next 6 points below are per Joe Norris at EAA: [NOTE WELL: ALL of the discussion below applies ONLY to radios; he said there are different rules for transponders, encoders & ELTs.  N.B. further:  it assumes you are flying only VFR; there are different rules for IFR aircraft.  Mix these up to your sorrow. I'm not addressing IFR below, it is beyond my needs to figure that one out. ]

   The pecking order to check whether your VFR aircraft needs a TSO'd radio is:
1) Check its certification basis.  For Ercoupes, this is CAR4a.  See whether it HAS ANY radio requirements. (For Ercoupes, probably not, ergo N/A ? Though I haven't looked yet...)
2) Check its Type Certificate. (For Ercoupes, probably ditto, though I haven't looked yet...)
[Ed, I think you said you'd read through one or both of these; perhaps you could insert a comment here?]
3) Check the general FAA & FCC Regs.  Joe Norris says NOTHING in FAA regs says a radio needs to be TSO'd, or even "meet requirements of TSO'd", so long as it is legal per FCC to operate as an aviation radio, then it's legal to install in any aircraft, even certificated aircraft.  Repeating:  there ARE NO requirements in the FARs for RADIOs for VFR use to be TSO'd.  Joe says he has read the regs thoroughly and says if someone tells you to the contrary, get them to state where in FARs it says so.  
4) Caveat:  some radio installation shops may THINK you need to have TSO'd radios because their own internal repair station manual may only allow the shop to put in TSO'd radios, so the shop folks assume it's because there's FAA regs requiring it, when it's only their own shop internal requirements.  [I did talk to a shop today that appears to recognize this, and says they have no problem installing non-TSO'd radios.]
5)*  You may not even need a 337.  Those forms address the installation process, NOT the radio itself, and are only needed at all IF the installation involves a "major structural change."  Putting the radio into an existing hole, or hanging it beneath the panel does NOT need a 337.  Similarly, if you're putting a new antenna into an existing antenna mount location, its not a "major structural change," therefore no 337 needed.  
6) If your installation does not involve a "major structural change," all you need is a logbook entry by the A&P who did it, plus (if necessary) a weight & balance adjustment & equipment list adjustment (if your plane has an equipment list).

I have also asked the AOPA legal services attorney who was so VERY knowledgeable and helpful to me last summer, with all the Qs I had surrounding acquisition of my 'Coupe.  He is currently swamped, but will look into the issue.  I did read him my report of Joe Norris's remarks, above, so he'll be on the same page we are whenever he gets back to me.  One caution he did have for us:  even though a 337 may not be legally necessary if all you're doing is putting a radio into an existing hole in the panel, or hanging it underneath, without making any major alterations, you may well run into people who THINK it is legally necessary, and so filing a 337 anyway, just as a precaution to have it in your files, may prevent a bump in the road later on (for example, when you sell and your buyer has a pre-purchase inspection).

*Bill B. disagrees with item 5) above - here's his response: