albravo wrote:Gunny,

I have a very similar config on my 63 182F. Sportsman, Wing-X with an MT spun by a PPonk. Same stall (or lack thereof) characteristics. She just sort of mushes down. I've never had the presence of mind to check the speed at the point of stall so I'm grateful for you posting your data. I'm coming over the fence at around 65mph just because I'm too new (and chicken) to try slower.

I'll be curious to hear how you like the handling after the VGs. When I was dropping my engine off at PPonk I looked at Steve Knopp's plane. Very similar to mine except his engine is bigger, a 550 if I recall correctly. His wing is the same as mine and he strongly advised me against attaching VGs. He says he's seen it several times and handling gets worse.

I don't want to re-open the VG debate, just stating I'm looking forward to your report.

I’ve seen a couple guys do a temporary install of VGs using double sided carpet tape. Easily removeable after a few flights if you don’t like the result. I wished I had done this on my 170. But if you like it, just do a permanent install. A little more work, but.....

MTV

Gunny wrote:CG has been right around 38.8 for the solo, light weight test flights (2100-2200 lb). I'm not really interested in exploring/validating the STC envelope. In a rough way I think establishing the baseline at these weights will predict performance at heavier weights. When I'm all done upgrading I'll redo it fully loaded so I know just what my performance is.

gunny

You apparently missed my point. Comparing your airplane to others performance is apples and oranges unless you more or less match weight and CG.

MTV

One thing I've wondered about STOL cuffs and VG's is whether or not installing them partial wing span would create a benefit? Or maybe downside? Hard to tell without testing.

I understand the goal of a complete wing alteration, but it seems on some commercially produced aircraft the drooped cuff is only added to the outer wing portion, or the VG's are offset in their chord wise spacing to create an intended span wise flight or stall behavior.

In my experience the Sportsman cuff by itself resulted in a benign mush and not sudden loss of lift at stall. Aileron effectiveness in slow flight was improved along with glide ratio (a small bit) and lower rate of descent power off (same minor improvement). The Micro VG's I installed full span and uniform chord wise spacing on non-Cessna aircraft do break/not mush, but at a higher AOA than the stock wing. Just some thoughts for discussion.

Gary

PA1195 wrote:One thing I've wondered about STOL cuffs and VG's is whether or not installing them partial wing span would create a benefit? Or maybe downside? Hard to tell without testing.

I understand the goal of a complete wing alteration, but it seems on some commercially produced aircraft the drooped cuff is only added to the outer wing portion, or the VG's are offset in their chord wise spacing to create an intended span wise flight or stall behavior.

In my experience the Sportsman cuff by itself resulted in a benign mush and not sudden loss of lift at stall. Aileron effectiveness in slow flight was improved along with glide ratio (a small bit) and lower rate of descent power off (same minor improvement). The Micro VG's I installed full span and uniform chord wise spacing on non-Cessna aircraft do break/not mush, but at a higher AOA than the stock wing. Just some thoughts for discussion.

Gary

The original developer of the Sportsman cuff noted that the critical piece of the cuff was the outboard section. That kit was based on NACA research, as is the “stepped “ leading edge on the Cirrus, and the Kodiak airplanes. Apparently, he thought the partial cuff didn’t look right, and the full cuff didn’t add any real negatives. At least that’s what I recall.

A big part of why the Sportsman kit improves aileron effectiveness is that the kit includes aileron gap seals. I’ve often thought that installing just those would be a cheap way to improve aileron effectiveness, even without the cuff.

MTV

Thanks Mike for the original info on the Quackenbush Sportsman cuff mod. I guess a partial span of that cuff or VG's (ether partial span or offset but full span like CC's) would help induce an initial inboard loss of lift and resulting mush rather than a complete break. It may also be with full span/same chord VG,s the tail simply gives up unless they or a fuselage strake are added back there. Note the inboard edge of the partial span cuff acts like a stall fence as it generates a turbulent wake over the upper wing surface.

So...does adding full span/same chord VG's to a cuff help or hurt the stall and lift behavior? I believe that's the gist of this progressive mod thread and some earlier posts cautioning their addition to the wing. The Cessna has what 2.5* wash primarily outboard of the flapped section, so that should remain flying versus the inboard flapped portion, especially with any flaps deployed (deployment = higher effective AOA of the flapped section).

But one caution with VG's is that their chord wise placement doesn't create a sudden loss of leading edge lift. They have to remain in laminar flow to be effective. Placed too far rearward on a stock wing or cuff and the lift bubble/pressure peak near the leading edge can suddenly burst over a few degrees of change in AOA. Tuft testing would show that behavior if it occurs if the pilot doesn't already notice it. Ideally the wing should gradually loose lift and the tail authority while the VG's are still functioning, and not stall abruptly because the VG's suddenly stop their function due to lack of flow over them.

Sealing the Cessna ailerons alone might be worth the effort as you note. Crosswinds did it with fabric with their Cessna kit and now others via metal. If the upper aileron surface is in turbulent pre-stall flow then any underside pressure that's better contained would help roll control (I assume). Gorilla tape to the rescue!

One more note. Testing of the Cessna L-19 by J.J. Cornish in the '50's revealed that a mid-wing lift discontinuity was generated by interference flow from the lift strut/lower wing intersection at about 15% chord. As the stagnation point of the relative air moved back under bottom of the leading edge and turned up and over the wing at high AOA, the lift strut intersection caused a portion of that flow's wake to go turbulent and separate from the upper surface. They were using suction flow to generate the high AOA and lift so maybe stock Cessna's are immune from that problem (tuft test?).

Gary

mtv wrote:

Gunny wrote:CG has been right around 38.8 for the solo, light weight test flights (2100-2200 lb). I'm not really interested in exploring/validating the STC envelope. In a rough way I think establishing the baseline at these weights will predict performance at heavier weights. When I'm all done upgrading I'll redo it fully loaded so I know just what my performance is.

gunny

You apparently missed my point. Comparing your airplane to others performance is apples and oranges unless you more or less match weight and CG.

MTV

MTV-

Maybe I did miss your point. Perhaps you missed mine, when I said earlier I'm only looking at my airplane and what these mods do to it. Doing anything else would require a much larger test program that I have zero interest in pursuing. For other airplanes my data is anecdotal. And for me it is mostly for fun, I'm not selling anything.

So far I haven't compared my airplane performance to anyone else's. I would be interested in anecdotal data for a stock wing airplane since I'm not going to rip anything off of mine to achieve those numbers.

gunny

Fine with me. I understood you’re not selling anything. Just trying to offer suggestions to improve the resulting data, and Compare apples to apples.

MTV

Gunny wrote: MTV- Maybe I did miss your point. Perhaps you missed mine, when I said earlier I'm only looking at my airplane and what these mods do to it. Doing anything else would require a much larger test program that I have zero interest in pursuing. For other airplanes my data is anecdotal. And for me it is mostly for fun, I'm not selling anything. So far I haven't compared my airplane performance to anyone else's. I would be interested in anecdotal data for a stock wing airplane since I'm not going to rip anything off of mine to achieve those numbers. gunny

I think you're right on the money.
When flight testing mods to see if they improve performance on YOUR airplane,
it's best to do it at your normal weight and CG levels, whether light or heavy.
Manipulating weight or CG to artificially match other airplanes would be counter-productive.
After all, the idea is to see if the mods improve your performance, not someone else's.

hotrod180 wrote:

Gunny wrote: MTV- Maybe I did miss your point. Perhaps you missed mine, when I said earlier I'm only looking at my airplane and what these mods do to it. Doing anything else would require a much larger test program that I have zero interest in pursuing. For other airplanes my data is anecdotal. And for me it is mostly for fun, I'm not selling anything. So far I haven't compared my airplane performance to anyone else's. I would be interested in anecdotal data for a stock wing airplane since I'm not going to rip anything off of mine to achieve those numbers. gunny

I think you're right on the money.
When flight testing mods to see if they improve performance on YOUR airplane,
it's best to do it at your normal weight and CG levels, whether light or heavy.
Manipulating weight or CG to artificially match other airplanes would be counter-productive.
After all, the idea is to see if the mods improve your performance, not someone else's.

You obviously missed my point as well. The point is: if you “Flight test” an airplane at X weight and Y center of gravity, then modify the airplane, and re-test at Z weight and or at A center of gravity, you have significantly biased your “results”.

And the same is true if you try to compare to other’s airplane performance without knowing at least what ball park THEIR “testing” was done in.

I agree that testing at “normal” loadings (whatever that is) does make sense. But if you conduct one test with near empty tanks and no load, then modify the airplane and “test” fly it with full tanks and some gear, you may have significantly biased your results.

Take a look at how flight test is done by a test pilot. There are ways to correct for loading and atmospheric conditions, but I doubt that most of us want to do that math. So I was simply suggesting that he control the variables by keeping the parameters as close as practical.

But, whatever winds your watch.

MTV

It might help across specs and planes to fly a GPS triangle or square while testing performance. Airspeed indicators, static sources, and stall warner adjustments can vary in their integrity. Stock setups are designed by the manufacturer for normal flight attitudes. In other words the stock indicated airspeed and stall can be subjective.

The test setups I've read about typically employ an extended boom for the pitot to get it away from the local air circulation near the wing and self point into the wind. We're not likely to do or need that for our test purposes.

The idea of a planned angled flight course is to reduce the effect of winds aloft...no big mystery. I guess averaging the data from that is good enough for most of us ordinary folks. Try to maintain level flight and play with the plane's configuration and speeds. Try some roll movements at the same time to note behavior.

I'm not sure how to qualify stall behavior. Good-bad-ugly come to mind but it's a quick event at best and maybe hard to recall later. Maybe set up a video looking out of the cockpit from behind the pilot or even on the panel. Then go back and review at leisure what it looked like from the camera's perspective and share? Hope this helps and comments welcome.

Gary

mtv wrote:You obviously missed my point as well. The point is: if you “Flight test” an airplane at X weight and Y center of gravity, then modify the airplane, and re-test at Z weight and or at A center of gravity, you have significantly biased your “results”.

And the same is true if you try to compare to other’s airplane performance without knowing at least what ball park THEIR “testing” was done in.

I agree that testing at “normal” loadings (whatever that is) does make sense. But if you conduct one test with near empty tanks and no load, then modify the airplane and “test” fly it with full tanks and some gear, you may have significantly biased your results.

Take a look at how flight test is done by a test pilot. There are ways to correct for loading and atmospheric conditions, but I doubt that most of us want to do that math. So I was simply suggesting that he control the variables by keeping the parameters as close as practical.

But, whatever winds your watch.

MTV

But MTV, that is exactly what I am doing controlling the variables for my airplane. From my perspective the performance of the airplane at stall, in takeoff and land mode is of prime interest at light weights. I've said I will check it at heavy weight, but that will be when I'm done. I actually don't think the results will be that much different light to heavy. We'll see.

I have slept at a Holiday Inn Express and I have been a test pilot. I did the certification testing for the M-26 Airwolf as well as the testing for a number of STCs that were done. It can be quite involved and while that was fun I don't want to commit the resources to an exercise like that for virtually no gain to me. I'm just reporting what I am seeing, your mileage may vary.

gunny

Ok, I've had a little time to fit in some T/O Land Tests and Stall series with the WingX and can post results. These are results for my airplane, not comparing it with anyone else, or the manufacturer. I am a little surprised by a few of the results. The Sportsman Cuff clean wing had a mush and all other flap settings had a slight break at stall, with Flaps 40 being a hard break. The WingX addition resulted in faster speeds, but only the clean wing had a slight break, most of the time it and all other flap settings developed a mush at the noted speeds and settled into a 300-500 fpm descent. Surprise: no stall break and slightly higher 'marginal performance speeds' from adding the WingX.

The real interesting thing were the T/O Land Distances and speeds. For one thing I was fairly consistent at speeds/times, which is good I guess. But the distance improved by about 23% and the speed was 17% lower. These are averages across a dozen 2B configs and twice that 2A configs. There are outliers short and long, due to inconsistent operator technique, and I left them in the database. I wasn't trying TOO hard to get good distances, just trying to be consistent.

Your mileage may vary. Vg's come next.

gunny

Interesting data there. It seems a little counter intuitive that the WingX actually raised your stall speed in a couple of configurations but the performance is still excellent.

Has the WingX changed anything about your cruise performance?

I noted earlier that is cost me 1-2 mph in cruise. Fairly insignificant.

The interesting thing is that the speeds for the WingX aren't really stall speeds, the wing never actually broke but one time in the clean configuration. They are datapoint where the airplane entered a pitch fungoid and a significant decent developed. I am equating that with stall.

The other interesting thing is how each flap setting doesn't change the 'speed' significantly.

gunny

What were the flap settings for T/O and landing tests? 50mph with 2A seems curiously high based on the stall speeds recorded, unless you were 0 flaps for all of it - but that wouldn't work for 2B and that speed.

I'm also wondering how you were gathering the data, mostly for my own curiosity. I'm constructing a little data collection system out of an R-Pi Zero board with a GPS, baro, 3-axis accelerometer, and some tiny LIDAR sensors I will attach to the gear legs and nose cowl. The intent is to play around with various configs, speeds, etc and determine exactly what gives me best T/O and landing performance once I get the P-Ponk and Sportsman installed, since it won't be even close to book value by then. I'm probably making it more complicated than I need to, but I have 3 of these LIDAR sensors in need of a project, so it kinda turned into this.

colopilot wrote:...I'm probably making it more complicated than I need to....

What makes you say that?

Good performance numbers for a 2300 lb plane. What density altitude are you seeing for your TO/LND numbers? Keep the info coming.

Gunny wrote:I noted earlier that is cost me 1-2 mph in cruise. Fairly insignificant.

The interesting thing is that the speeds for the WingX aren't really stall speeds, the wing never actually broke but one time in the clean configuration. They are datapoint where the airplane entered a pitch fungoid and a significant decent developed. I am equating that with stall.

The other interesting thing is how each flap setting doesn't change the 'speed' significantly.

gunny

Sounds like you’re stalling your elevator now. The pitching moment on the modified wing might be too high for the tail to have enough control effectiveness at low speeds to bring the wing to stall.

CamTom-

Now that is an interesting comment. The video I did of the tuft test sort of confirms what you said. I do see some boundary layer separation at the wing root and out to about half flap, but the progression doesn't go farther than 2/3d of the wing. Maybe Vg's are what is needed at this point, more to keep energy on the tail than the wing.

DA is around 3000'. The takeoff technique I use is to start with 10 flap, when the tail comes up I pop 30 flap.

gunny

Gunny wrote:

mtv wrote:You obviously missed my point as well. The point is: if you “Flight test” an airplane at X weight and Y center of gravity, then modify the airplane, and re-test at Z weight and or at A center of gravity, you have significantly biased your “results”.

And the same is true if you try to compare to other’s airplane performance without knowing at least what ball park THEIR “testing” was done in.

But MTV, that is exactly what I am doing controlling the variables for my airplane.

Gunny wrote:
I would like Stall series numbers from an early model stock wing 180/182 to add to the database for my Sportsman and the WingX.

It would be nice to have an actual flight tested performance database to go along with the anecdotal stuff that is out there. But I have no access to a plain stock wing.

Based on your original post, it would appear that you are seeking assistance to build a database of stall performance across the fleet that some may interpret as a means to draw comparative inferences. MTV may not have chimed in with his apples to oranges comparison otherwise. Well, maybe he would have