CH 750/701 STOL Operations, Techniques, Comparison of Configurations and Tricks-of-the-Trade?

How to get the most or almost the most out of the airplane? Maybe there's a website or discussion that has already hashed this out--please post workable links if that's the case.

Several discussions have wandered off into this area, so I thought I'd start a specific thread . . .

There's been much talk on several threads about operation of the 750  and 701 with and without slats. Chris Heintz's piece on the Zenith website makes it clear that if one takes off the slats, angle-of-climb and -descent will suffer, but isn't clear about how much. Slips without slats aren't discussed much either. And, of course, there's the ongoing flap about flap use, from "don't use any flaps until you have 80+ hours [what's going on here?], flaps are only for drag, not for lift, use 1/4 flaps for takeoff, then ease them off, etc.

I know there's a wide range of skill levels out there, and I aspire to better-than-average one of these days, so I'll be interested in and grateful for any insights from anybody, regardless of skill level. (I hope all the most skillful take a look at this between flights.)

WT

PS: I've noticed that the Valdez STOL contest concentrates on takeoff and landing distance, which is fine, but I wonder if there are any demonstrations of angle-of-climb and descent, especially with 750's and 701's with and without slats and with and without VGs? I notice that the Valdez contestants tend to stay in ground effect quite a while . . .

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Wayne, there's a lot that comes into play with the Valdez contestants, including specialized throttle triggers, Hall wind speed indicators where they watch for just the right gusts for takeoff, etc. so the floating is intentional at their extremely controllable slow speed so they can dump it on the ground where they want. 

Yes, the slats impact cruise, they are drag, but at the same side, drag is your friend when you're trying to set it someplace tight. Slipping is a great way to produce instant drag, slats or no slats, and some can become very proficient in using this technique in all conditions, tough crosswinds included. It all comes down to how do you want to fly, and what  do you want to do with your plane, there's no better way or right way to set up you plane or fly it, except for the way you choose for you. I think it would be interesting if you did the slats/no slats test on your plane and posted it on the forum for the rest of us to see. 

What's interesting is when you look at the Oshkosh STOL winners below, Frank Knapp 1st place, and Steve Henry, 3rd place, their takeoff distance and landing distance  were pretty much the same. The others had landing distances that were considerably longer than their take off roll. Both Frank Knapp and Steve Henry's aircraft have leading edge slats, so you wonder how much better control they had at slower speeds, hence the shorter distance in landing. Power can influence take off role, not so much landing role. Hard to say, but it's worth thinking about. 

July 31, 2014 - Frank Knapp took top honors at the first STOL competition at EAA AirVenture Oshkosh 2014, with a winning distance of 134 feet.

Each finalist of the short takeoff and landing competition was allowed two runs, with the lowest total giving them their final score.

Knapp and his airplane, Lil’ Cub (N85CX), took off in 72 feet, and then landed at 62 feet, giving him a winning total of 134 feet.

Taking second place was Bobby Breeden, with a total of 197 feet (72 feet at takeoff and 125 feet at landing), while third place went to Steve Henry at 206 feet. Both of his runs totaled 206 feet—98-foot takeoff and 108-foot landing, and 102-foot takeoff and 104-foot landing.

Scot Warren took fourth with a takeoff of 115 feet and a landing of 151 feet, for a total of 266 feet; Pops Dory took fifth place with a takeoff of 98 feet and a landing at 190 feet, for a total of 288 feet; and Dennis Wittenberg took sixth at 315 feet, including a takeoff of 152 feet and a landing of 163 feet.

Walt Snyder

Walt, your point about the first, second, and third-place winners being very close together points up the issue I'm trying to get at with the slats/no slats but VGs question. What are the marginal differences with the two configurations? In the real world, of varying altitudes, temperatures, pilots skill variations between and among pilots, one should throw an envelope over it all at both extremes and assume the worst case in real-world situations. In the experience I related some time ago where my "captain" got this exactly backwards and I got into the airplane with him anyway, I came as close to buying the farm as I ever want to come.

I plan to practice, practice, practice on a long runway until I can nail it consistently within an envelope, then move on to rougher strips to see how much difference landing surfaces make, and will need to calculate equivalencies based on density altitude, wind, etc, but most of all need to develop that sixth-sense of "muscle memory" to go along with the numbers. "Feel" may be in the realm of subconscious calculation, but it can also be misleading, as, for example, in instrument flying.

Then I think I may put the slats back on and find out for myself what the marginal differences are once I'm satisfied with my ability to handle the slatless version, flaps, slips, and all. In the meantime, I'm interested in what others have found, particularly in the realm of angle-of-climb. John Austin is the only one I know of who has actually done this, and he seems to think the margin is small, maybe even undetectable. However, he flies in a much different environment than we do.

I found these videos yesterday; y'all have probably seen them, but I thought they were quite good. The last one is an article. This outfit seems to know what they're talking about and have produced excellent videos. Comments?

https://www.youtube.com/watch?v=dfXT38YIO6g

 

https://www.youtube.com/watch?v=CrPJac80W9Y

 

https://www.youtube.com/watch?v=J4NnmbbSizQ

 

https://www.backcountrypilot.org/the-approach/the-approach-landing

Wayne, good call on your decision to practice, practice, practice, know your plane, and then put the slats back on and judge for yourself. Then you'll know the impact of the slats for your type of flying.

Look at the pictures below and ask yourself if you want to get this aggressive and take full advantage of your STOL. You see Deane Phillips (New Zealand STOL winner) modified tail skid? You see the poof of dust where the other aircraft's tail hit the dirt? If your tail tie down ring still has paint on it, slats may not be a big deal in your departures. I would message both of these pilots on the forum and get their input on the impact of slats for the type of departures they do, if you see yourself departing like this. 

Re BackCountry videos, they're the best, and you may want to join us Oct 10,11,12th for the Backcountry Sierra Pilots gathering near Tahoe. Big John and Little John are flying up, and if I don't have my time flown off I'll hitch a ride with them. There will be 70 bush planes at this event, and there will be side excursions into areas that they will talk about until next year. If you want answers to questions from experienced bush pilots, this is the place. 

Walt Snyder

750MV has a short skid, but I'd be interested in more detail on the longer skid on JUG.

I just got my new curved fork and strut from the factory, but I was a bit surprised to get it in two pieces. The curved plate has bolt holes in it, but the aluminum is not pre-drilled. Was I wrong to expect it to come fully assembled? This seems like an extremely precise operation that should be done in the factory on a jig or something. Can anyone help enlighten me on this? 

WT

That's the way they come, Wayne. You have to determine the center-line of the top of the fork and accurately center the curved plate laterally, clamp it, and drill the holes. "Measure twice and drill once!"

If your curved plate has a slot in it for a tow bar, you'll want to position it fore-and-aft so the "tongue" with the slot in it clears the front of the fork so the tow bar's hook will pass through. (Did I see somewhere that Zenith has dropped this method and now uses a bolt with bushings in the actual nosegear leg to serve as attach points for a conventional tow bar?)

Here's a little tip: When your nosegear is finished, put a strip of clear urethane leading-edge tape up the forward-facing portion of the nosegear leg - bugs will wipe right off!

I think best practice is usually to insert bolts with the nuts down so if one comes off, the bolt doesn't immediately fall out of the hole, but if you have the 800 tires, you'll likely need to insert the fork bolts from below ("heads down") for better clearance with the tire.

I still marvel at the scratch builders - those predrilled kit parts really spoil us!  ;>)

John

N750A

Thanks, John. Did your kit come with the curved fork? I presume that you drilled yours (after measuring twice), but I'm concerned about drilling the holes at the proper angles. I would rather pay more and have it done at the factory. Rather than send my flat-bottomed strut to the factory for cutting and welding, I bought a new strut to go with the fork. I reckon I am spoiled, and maybe I'm paranoid, but I don't want to screw up this most important part, particularly given the stresses it must endure. I read and took to heart the recent series of articles in Sport Aviation on drilling holes properly, and will read them again and again before I attempt this. I suspect that putting this together just a little bit crooked could be disastrous.

I still don't understand WHY the factory doesn't want to drill the holes.

Thanks for all the tips.

Wayne

I had an edition 1 kit upgraded to an edition 2. The new fork came out after the edition 2 release, so I sent my nosegear leg back to Zenith, had the curved plate welded-on by Zenith, and bought the new fork.

I know you didn't build your aircraft, but I was so far into construction when this happened that it didn't seem all that difficult to position and drill - it's definitely a much better design than the original! It's truly a critical assembly, but I'd guess there are thousands of lbs of shear strength in those 4 bolts - you'd peel the gear off the plane before those bolts come loose!

John

Ok, did you eyeball the (compound) angles and drill it by hand, or build a jig or something? I'm not so much worried about the bolts coming loose or shearing, but more about setting up a cracking scenario in the fork because of a "sloppy" drilling job.

How did you determine the center precisely so the fork didn't bolt on crooked?

Wayne

As I recall, once the curved plate was clamped into position and the alignment re-checked fore-and-aft and laterally, I indeed eyeballed the drill position to ensure it was perpendicular in both planes. I used a bit that fit snugly in the holes in the curved plate and just "kissed it" to the fork at all four holes to mark the center of the hole (there are centering punches made for this purpose but this method works OK). I then removed the plate/nosegear leg, and step-drilled up to final size. I honestly don't remember if I used a ream on the final size or not. Used an oversize bit to lightly chamfer and debur the hole edges and bolted it together. Seems like I recall drilling a drain hole in the center of the assembly - but, consult the drawing!

John

John,

Thanks for the follow-up. You did not drill through the holes on the attachment plate to help with alignment, right?

I may let the A&P do this. Yeah, I'm chicken.

Now I gotta order my plastic VGs, including some extras in case I spill fuel.

Wayne

PS: Did you paint or otherwise protect the drill hole in the strut? Did you drill in in the center or at the low end?

Even my A&P is spooked about drilling that fork. He had the same question I have (but Zenith has yet to answer my email--probably backed up from Oshkosh--"Why doesn't the factory want to drill the holes in the fork?"

Wayne

I primed and painted the bottom of the curved plate and the drain hole before assembly. I also liberally sprayed through the drain hole the interior of the gear leg with Boeshield T-9 before assembly. I "think" the hole was centered - but refer to the drawing to be sure - I did!

I'm sure many different methods/techniques have been used to drill those holes and I haven't seen a single post about any failures - maybe someone messed up a fork, but they haven't admitted it on the forum! 

As we say ad nauseum, "You aren't building a F16!"

... and as Nike says, "JUST DO IT!" 

... and get a new A&P!!!   ;>)   

John

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