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L4-J3 rear seat questions for the gurus

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Well-Known Member
May 25, 2013
Reaction score
Hallettsville TX (34R)
Howdy All.
I’ve maintained/rebuilt J3’s for 40+ years, but never an L4. I can’t ever even remember looking closely at one. My loss I think, anyway
I’ve got a J3 in the shop that fits the date of mfr/SN range of most of the L4s I’ve researched. Of course the early logbooks are missing. I’ve requested the FAA CD.
Here’s the rub…there’s something “odd” about the airplanes back seat. The upper curved crossbar is different… flatter, and the bottom bar is rigidly mounted, as are the lap belt mounts. Theres no sling, the cushion support comes from furniture type curved springs. Of course the FAA/CD might reveal more, but I can’t tell if it was a factory/common conversion for an L4, or just someone’s idea that may/may not be documented. Whoever did the modification did a nice job.
My post is probably premature, I’m hoping the CD clears this up, but was there Service Bulletin or procedure for converting an L4 to an J3 that I can research. My online searches have revealed nothing.
If it turns out it’s not an L4, any type of ideas/prior approvals or documentation for what I’ve described would sure help me as a basis for approving what’s been done. My fear is that it’s an original J3 and, like so many other times, it’s just been done and I’ll have to make it legal.
Thanks in advance. As always, advice, ideas, and suggestions welcomed.

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