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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I'll echo John's last line, maybe if this was an F-18 hitting the deck at 150 mph I'd be concerned, but I can't imagine being able to mess it up so bad it would compromise my plane plopping down and tracking true. I'd guess that's what Zenith felt also. They can build the spars, but leave me the other stuff. 

Walt Snyder

Walt, I sent the outfit in Nevada an email about the trouble I was having finding anything out about the fly-in, but haven't heard back. "Three shells" seems to be a "Target" store, so I'll try again to try and find out just where it is and what's going on. We will probably drive up if we come at all, since it's not fair of me to ask my wife to drive the camper while I fly. If you have any more info to share, please post. Can it be reached by road?

We will make it a stop on our annual fall trip, probably going from there up through the Black Rock Desert, Steen's mountain, NE Oregon, Idaho, Montana, Wyoming, Western Colorado, Utah, Arizona, and home around the end of October or mid-November. I will, of course, want to visit as many back-country pilots and planes as I can. Maybe in the spring I'll be able to work something out where we can take a flying trip around the Intermountain West/Basin and Range area.

Wayne

Wayne

Why don't you check out this site... http://www.stolspeed.com/ - JG was the fellow, who was the first to remove the slats and also developed VG's for the 701 and Savannah along with several other mods that worked!

Ron,

Thanks for the helpful link. However, we've plowed that ground several times in several topics - here's one: Slats and VG's.

John

John,

My intention here was not to re-plow old ground, but to sow seeds of contentment in the whole area of getting the most out of this airplane. We are all grateful for your faithful moderation in all things, including stopping thread creep by drilling holes before the crack gets worse.

I get what you say about there not being "much [performance] difference" between slats and no slats with VGs. We don't need to re-plow that. However, there remain those who would not part with their slats, period. I remain curious about the size of the marginal difference--is it insignificant, crucial, or somewhere in-between. I also remain curious about, say, whether a 750 without slats with VGs could land as, or almost as steeply by slipping. I am also curious about takeoff and climb differences in the two configurations, and the significance of the difference. I beg your forgiveness if this has already been cleared up and I have missed it. If the margin is slim, one could sell off the slats or give them to someone in need. If the margin is significantly broad, then I wonder if I should be rushing in where angels (or devils) might be waiting, or just staying the hell out of such places anyway.

My intention was to create an "umbrella" thread for for 750 operations and limitations where the whole enchilada could be discussed for the benefit of us "newbies." One way of bringing old plowed ground to the attention of those of us who don't even know what we don't know would be for the old-timers to post links to other discussions as you have done, then participants would have one place where the old stuff is summarized with links and truly new stuff could be posted under a broader heading than, say "flaps" or "slips," etc.

Maybe this is not the way to do it, but I've just dived in and hoped for the best. I'll trust in The Moderator to keep me in line . . .

Best,

WT

Thanks, Ron. Here's a key quote from the site, which seems to contradict Chris' statement that both descent angle and climb angle with slats will be greater, not lower, than no slats with VGs. Who's right? (Italics mine.)

"The vast reduction in drag allows all these aircraft to fly considerably faster for the same power, climb better, glide better, and with the benefit of Vortex Generators, lift-off and touch-down just as short as with slats, but with more control."

Of course, this guy is selling VG's.

WT

It doesn't say anything in that statement about descent and climb angle! Climb "better" can mean angle or rate of climb. I agree that take-off and landing distances are about the same, but you cannot land as short over an obstruction without slats because of the steeper descent angle the slats provide. Without slats, they undoubtedly fly faster and glide better. The VG's seem to not affect speed at all - I couldn't detect any speed differences with slats removed and no VG's versus slats removed and VG's installed.

And just to clarify for the novice - we're talking about VG's on the main wings, not the VG's on the tail that is a Zenith option for more elevator authority  and installed by most builders.

John

Ah, HA! Good point, John! A crucial distinction we should all be on the alert for--for that matter with respect to everything. Removal of the slats gives up climb and descent angle for speed (8 mph, more or less?) and VGs affect stall speed (slower than without them), correct?

So now we have it clear that slats steepen the angle of climb/descent, but is it clear that one is not as likely to bang the nose down as hard upon landing with the slats removed as with them on? And is it clear that, the angle angle aside, that one can land just as slow/short and get off just as quickly in about the same distance (as at Valdez, where they approach pretty flat and depart level a few feet off the ground, in ground-effect to gain climb speed) as with slats, but just can't climb or descend as steeply? We know that there is a difference with the two configurations, but how good an idea do we have about how much flatter the glide and climb angles are without slats? Should we complicate this further by discussing leading edge cuffs a la the Robertson conversions for Cessnas?

Let's say we land onto a tight strip without slats by slipping (again, how much difference between slipping with no slats and not slipping with slats?), but we can't increase the angle of climb on departure. Would we (theoretically and in the real world) be able to have some slats flown in to get us out? We are still STOL without slats? More STOL with slats? Significantly more or undetectably more?

Wayne

Wayne, I'd say it's time to not fly your plane by the keyboard and take it up and find out. You can go back and forth with what if's, but you're going to miss a lot of the enjoyment and learning by not taking your particular aircraft up and wringing it out. You know your plane flies, I'd want to know now it's envelope, and none of us can tell you that, only you can, your aircraft is unique, though we would appreciate it if you share with us what you find out. 

All of our aircraft perform differently in some respect due to build, weight, engine, etc, so find out how your aircraft performs first as built, then deal with the slats, tires, slips issues, because you then have a base point. We'd like to hear what you find out about your experiences. 

Walt Snyder 

Roger, WILCO, as soon as it's capable. It's getting engine and rudder work, a new nose gear, and maybe some radio work. Maybe in another week or two, with any luck. If it weren't for bad luck . . . etc. This thing has been quite a soap opera, and it has sorely tried my patience.

So, my heartfelt apologies to all who have been inconvenienced by my babble here. Y'all are not the first long-timers and actual builders who have lost patience with my ignorance.

Best,

WT

PS: I still haven't had any luck with the backcountrypilot website; unable to log on or raise anybody by email, but I reckon I'll figure it out by October.

Nice, looking forward to you stopping by. Contact Zane on the website if you're having problems with it.

Walt Snyder

Wayne, with your background in thorough research and the right questions, how about applying it to the slats/no slats question? Fly and learn your plane without the slats like you're going to do, then learn it with the slats. Pick a morning with zero wind and set up a GoPro at the departure end of the runway, and leave it on and let it record your take off rolls and climbs, as well as your landings, with and without slats. Make a note of the date and DA and temps, and watch your fuel weight and wind to make sure it's apples to apples.

When you review the film, you can overlay your departure rolls, angle of descent, ascent, etc, and show it in different colors so you can see from an outside unbiased view provided by the GoPro what you find. 

Of course, if you start selling VGs or modified slats on the forum your results will be suspect, but it would be really interesting and beneficial in what you find. And, post it in the appropriate forum. You might end up being a hero for some builders.

Walt Snyder

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