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The Pipistrel Sinus has detachable wingtips and wing extensions.

enter image description here

However, they designed the plane with a wing core span at 39'11", just barely larger than a standard "40' door" (which is actually closer to 39', since the hangar structure itself eats into the 40' width).

As can be seen in the below video, it's just barely possible to fit it into a standard 40' hangar. But I don't think anyone would say it's practical, it's just that it's possible.

This wingspan has greatly limited the airplane's appeal in the US market, and this leaves me thinking that there is some crucially important physical or regulatory reason why Pipistrel didn't make the tips sections slightly longer so the core section could have been slightly smaller.

In contrast, the Phoenix LSA has designed their wings so that the core section is 35' wide, even though the full wingspan is only inches shorter than the Pipistrel Sinus:

enter image description here

What was worth trading off readily fitting in the vast majority of US hangars for an extra couple inches of core wing? Maybe Pipistrel doesn't consider the US as a likely motorglider market to begin with, and so they unapologetically optimized for their home market?

Update:

@StephenS points out that the official tip-less wingspan is 39'11", so technically 1" under the 40'. I stand corrected and have adjusted the question.

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  • $\begingroup$ Pure speculation, so I will only add this as a comment. Probably the wingspan just ended up being impractically long to meet performance goals. $\endgroup$
    – Jpe61
    Commented Nov 2, 2022 at 16:58
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    $\begingroup$ In SI-units: 41' = 12.5 m $\endgroup$
    – Gypaets
    Commented Nov 2, 2022 at 17:51
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    $\begingroup$ 41 ft x 0.3048 m/ft= 12.4968 m. Could it be that Pipistrel, a European manufacturer from Slovenia, designed it to be 12.5m for the European market? $\endgroup$
    – DeltaLima ♦
    Commented Nov 2, 2022 at 18:46
  • $\begingroup$ @DeltaLima Absolutely, except they still would have known that there's a huge potential market in the US which they could go after, and by making it 12.5m instead of 12m large they +- shut themselves out of it. Since they went through a certification process, there's no fixing this in post, either. They've locked themselves into a potentially 40 year design choice, so you can bet they thought it through before committing. $\endgroup$
    – Kenn Sebesta
    Commented Nov 2, 2022 at 19:11
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    $\begingroup$ "...you can bet they thought it through before committing." Plenty of bets have been lost being overconfident about a company's market research! ;) $\endgroup$
    – Michael Hall
    Commented Nov 2, 2022 at 19:39

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Per the Pipistrel USA Sinus FLEX web site, the wingspan without tips is 39’11” to fit in standard 40’ US hangars. After pulling it out of the hangar, you would likely attach the long tips, which aren’t intended to fit in any hangar.

Yes, it probably would have been better to make it fit in a 40’ hangar with short tips installed, but I suspect those were designed for ramp tiedown. Or maybe it fits in slightly larger foreign hangars but by the time they realized the problem with US hangars, it was too late to change the wing design.

Unless there’s someone here on the Pipistrel design team, it’s unlikely you’ll get an authoritative answer:

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  • $\begingroup$ That's a great data point, I had read somewhere it was 41' without tips but clearly that was wrong. As an aide, keep in mind that many-- perhaps most-- 40' T-hangars do not have 40' doors. The hangars repeat every 40', which means that some small part of that, typically 4" on a side, is not available as it is used for the building structure. The upshot is that a 40' hangar is actually 39' and change. I have update my question to reflect this. $\endgroup$
    – Kenn Sebesta
    Commented Nov 2, 2022 at 19:22

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