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Permalink Reply by John Austin on October 30, 2021 at 7:49am

I've never heard of a factory test plane having an issue without slats, but here's what Chris Heintz, designer of the 701, said on the topic: Leading Edge Slats vs Vortex Generators.

My STOL 750 flew perfectly well with no slats or VG's.  With VG's, STOL performance is only slightly degraded - the biggest difference is is that you can't fly the ascent and descent angles nearly as steeply as with slats.  On the other hand, deleting the slats and installing Stolspeed VG's added 14 lbs. to my useful load and boosted the cruise speed about 6-8 knots.  I flew the 750 in that configuration for 100's of hours and just recently re-installed my slats and bigger tires so as to play around with the STOL performance again - and am having a ball!

John

N750A

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Permalink Reply by Bob Simmons on November 1, 2021 at 7:22pm

I'm planning to do pretty much what John did. The slats will be on initially to maintain conformity and allow me to build time and familiarity with the aircraft, but will come off and be replaced with VG's eventually. I'll maintain the 'blades' on the leading edge so I can remount the slats at some point in the future, should I decide to do so.

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Permalink Reply by John Austin on November 6, 2021 at 8:17am

The slats will be on initially to maintain conformity and allow me to build time and familiarity with the aircraft ...

If you get transition training, that sounds like a good plan.  Prior to my first flight, I was able to get a little time in a CH750 both with and without slats, but when I got my AW certificate, my slats were still in the paint shop and the DAR recommended we just go ahead and do the certification without them and that I could add the slats later during Phase 1 testing.

I found the 750 much easier to land without slats - you don't have nearly the drag so it penetrates better and if you start to stall a little too high above the deck, just releasing back pressure gets you flying again.  Sebastien actually stated in a Cruzer promotional video that the Cruzer was "easier to land since it didn't have slats."

The point of all this is that if one doesn't get transition training, or initially feels uncomfortable with the slats during approach to landing, removing the slats makes the plane fly more conventionally and a bit easier to land and allows one to concentrate more on other aspects of the testing and gain general familiarity.  BTW, the DAR's advice was great as I put my slats on after a number of hours in Phase 1, developed the numbers, and also made W&B sheets for with and without slats.  After all that, it was just a simple logbook entry any time I wanted to install or remove the slats and give reference to the proper W&B.

I eventually left my slats off for 100's of hours, so I "shaved" my slat brackets back to 20 mm height - looked better and sufficient metal left for adequate hole distance for mounting bolts.  I made some "intermediate brackets" to bridge the distance between the "shaved" brackets and the slats and left them bolted to the slats so it's still just 8 bolts on each slat to install or remove them.

John

N750A

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