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Comment by Samuel McNair on July 13, 2015 at 2:46pm

Mike; I have some time on the plane now without the slats on. Please note that I don't have any covers on my lift struts so they remain a very high drag item. I have made a few 1 to 2 hour trips in conditions of 95'F ambient (heat index 105'F) days at 4000 to 4500' density altitude. With my doors on I am cruising at 75% power LOP burning right at 8.3 to 8.6 gph, with TAS between 88 and 90 KTAS. With the doors off it loses right at  8-10 knots depending on how well I keep the ball centered. Under those draggy conditions I am able to keep the hottest CHT between 390 and 400'F the rest of them stay at 365 to 385'F. Oddest thing is that the hottest CHT moves around from #2 to #3. So I have a bit more tweaking to do before I am satisfied, but it can wait until later. It is good flying weather.

 

I cross checked the TAS indication with my GPS flying up and downwind and the numbers are within 1 knot at cruise.

 

Power off stall speed (indicated) without the slats but with VGs appears to be ~3 knots higher. With the VGs on the tail I have so much elevator authority that it would be easy to smack the tail on the pavement during roll out and I can do the tricycle gear equivalent of wheel landings and hold the nose off even with real forward CG down to ~32 knots indicated. I don't go slower than that holding the nose up for fear of slamming the nose when the tail finally does stall.

 

Power on stalls with or without slats and with the flaps on are just too dangerous (without a chute) to find out what the stall speed really is. This is due to really extreme deck angles requiring a lot of rudder dancing to keep from falling off into something resembling a hammer head. I am much too busy holding the aircraft in the sky to watch and log the airspeed at POS conditions.

 

The stall without slats and with VGs is much more gentle and conventional. In fact at idle, stick back against the stops, it wavers between 40 and 43 Kts indicated and mushes only a little nose up, wings level at about 800 -1000 fpm sink rate.  

 

I cannot tell any difference in landing distance without the slats. I am sure that there is some but I am not precision enough yet with this plane to see the difference. Also I always land with no power. I reduce to idle, at the key point and it stays there until touchdown. I feel like I could really drag it in on the prop and get it much shorter, but I want to master this thing dead stick first and I can still land much shorter than I can take off.

 

When it was still cool (75-80'F) and a little breezy) with slats on I could take off in about 165 to 185' at best and routinely at about 225' -250' without flogging the plane. At 90-95'F with the slats off and no breeze it requires around 300 - 325 feet.  I don't have a single day with and without under stable wind conditions to get more accurate data. And it isn't worth the downgrade in performance to put them back on to find out.

 

I have the 170 HP O-360 and a mid range prop that limits me to 2450 RPM in the climb. But yesterday at 98'F OAT with 30 gallons fuel, 500 pounds of guys in the front, and another 20 lbs of junk in the plane we got off in around 100 yards and climbed out at 800 fpm.

 

I picked up about 150 to 200 fpm at about 7-8 knots faster climb speed. 

 

I lost 20 lbs with the slats. 

 

Verdict? I kept the slat brackets and wrapped up the slats for storage. I don't see myself ever putting them back on. They will just sit there until they get sold with the plane.

 

Comment by Mike Joslyn on April 30, 2015 at 8:16am

I hope you get that figured out. I have seen a lot of posts relative to cooling issues. We will likely be installing an IO-390 in the next month so I'm hoping we find some common setup solutions to avoid these issues. Have you tried flying without slats yet?

Comment by Samuel McNair on April 30, 2015 at 8:11am

Mike; I could not find your question on the comment wall.  The short answer is "kind of".  By running well lean of peak (slight roughness)  I was able to keep my hottest CHT to 405'F and most of them on the high 380 to mid 390 range.  Except on climb out (where I have no cooling issues at all) if running in the traditional ROP mode my #2 gets up to 420'F or so and #1 is not far behind. These are at 80"F OAT conditions which are pretty typical here. Based on conversations with Chris, I still have a few things to try.  I would give my right arm for some detailed photos of a stock cowl that cools properly.

 

Thanks for asking.