PSTOL flaps on FX-3?

[hawgdrvr]

Anyone modified their FX-3 to use PSTOL flaps? Looks like an interesting design. Oddly the FX-3 stall speed is higher flaps down vs. no flap.

https://www.airframesalaska.com/Perf...STOL_a/268.htm

And no, I'm not doing this, just curious as it looks like the design is better.

[Andy]

Oddly the FX-3 stall speed is higher flaps down vs. no flap.

The AFM gives max gross stall speed for no flap and full flap. I have not seen published data for stall speeds at the intermediate flap settings. My experience with my FX-3 indicates that partial flap lowers the stall speed.

I'm not surprised that 46 deg flap gives a higher stall speed than clean. The contribution to drag is big and the contribution to lift is likely much smaller in proportion.

[Narwhal747]

Anyone modified their FX-3 to use PSTOL flaps? Looks like an interesting design. Oddly the FX-3 stall speed is higher flaps down vs. no flap.

https://www.airframesalaska.com/Perf...STOL_a/268.htm

And no, I'm not doing this, just curious as it looks like the design is better.

carboncub.jpeg

This was allegedly a carbon cub modified to take P-STOL's but there isn't much information about it. I found it on this thread over at SC.org https://www.supercub.org/forum/showt...131#post804131
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I've flown P-STOL kitted PA-18's vs Non P-STOL kitted PA-18's back to back and couldn't really tell a huge difference. Maybe someone with thousands of hours in the type could. I kind of preferred the stock flaps and bungess to the P-STOL and AOSS equipped PA-18's I flew. Granted, the fact that they were on 35's probably negated any suspension differences.
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I couldn't really get the FX3 I flew for 15 hours (same one you trained in I think, hawgdrvr) to do a real power off stall. Some nose heavy cessnas (182's) behave the same way. At the published stall speed, with power off, the elevator loses authority and the nose just drops down to a roughly level pitch attitude even when you hold full aft stick with a lot of nose up trim, whether flaps or up or down. I don't really feel like you really achieve the critical AOA of the wing when you demonstrate a power off stall in the carbon cub.

Kris mentioned that the number in the AFM was based on a power-off stall. I think the higher flaps down power-off stall speed number in the AFM can be attributed to this behavior (elevator stops working at a higher airspeed when power off with flaps down vs power-off with up) plus maybe a little bit of indicated airspeed error vs calibrated airspeed that is more prevalent at the higher AOA with flaps up. Perhaps the flaps block some airflow to the tail when power off but prop blast with power on negates that effect? Just speculating.

With power on, it doesn't seem to stall until less than 20 MPH IAS, with full flaps, and that's at max gross weight....but when it does stall with power, it can be pretty abrupt, and drops a wing quick if you aren't well coordinated. Then again, that's with me flying, and I'm very average, at best, behind a cub.
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At the factory, it was mentioned that some people are ordering FX's with carbon cub SS flaps, because apparently the SS flaps deflect to a higher angle. I don't know the differences otherwise.

In regard to the P-STOL's, there is some more info about them in the linked thread in terms of what Backcountry and Mackey are doing, etc.

I don't see P-STOL's on Toby Ashley's sarge or Butch Kingston's EX. They are running slats of course for the pure STOL contests, though (but interestingly not the STOL drags). With that said, I'm sure there are so many mods going on with those that they're no more a stock carbon cub than Toyota's NASCAR team's car is a stock Camry.

[hawgdrvr]

First and foremost - I'm no expert on this! I'm new to the FX-3 approaching 100 hrs in type.

My flight this past Sunday I could feel the tail buffet on final, guessing it's turbulent airflow from full flaps, this was around 65 mph. I think people might be choosing SS flaps because the G series flaps have a gap between the flap and wing and this may be causing the less effective flap setup where it's causing a more turbulent wake aft, don't know. I think the fowler flap design is ideal as you don't get the gap and you get the airfoil design and better airflow for reduced stall speeds, less turbulence aft, etc. This is what caught my attention in the P-STOL flap design, looks like a great design. I think if CC could simply attach a thin sheet metal design that blocks the gap in the flap it may be more effective as a flap vs. a speed brake. Again, just guessing.

Interesting discussion on flap position vs. stall speed. I think I'm going to do some stall tests, power off most likely, no flap and each stall position and see what I can determine. As mentioned, it's hard to really tell the stall vs. loss of elevator control.

I agree with the power on speed differences, it seems the airflow of 1500 RPM makes a big difference. I've watched some videos from TSquared in his FX-3 showing the same. In my recent stall testing with 1500 RPM it was like I couldn't get it to stall, it was just a controlled sink rate.

In the end, it's a great flying plane, love the FX-3. I'm just curious on options to further slow the speeds for landings and also curious of the turbulent airflow over the tail you can feel in the right conditions.

[hawgdrvr]

Several YouTube videos on the P-STOL flaps:

https://www.youtube.com/results?sear...nce+stol+flaps

[Andy]

My flight this past Sunday I could feel the tail buffet on final, guessing it's turbulent airflow from full flaps, this was around 65 mph.

Why full flap at 65 mph? I think I'm usually below 55 mph IAS before I select full flap but I often approach at about 50 mph with flaps 2. Your FX-3 is quite a bit heavier than mine though.

[hawgdrvr]

Why full flap at 65 mph? I think I'm usually below 55 mph IAS before I select full flap but I often approach at about 50 mph with flaps 2. Your FX-3 is quite a bit heavier than mine though.

I'm usually configured full flaps prior to turning base or while on base. It's just the speed I choose at that phase and work towards 55 on final but Sunday I remained at 65 until short final then started slowing. I just have no need to be slower with a very long runway and touch-down around 2K ft down the runway to be closer to the turn off closer to where I go to the hangars otherwise I'm taxiing opposite direction traffic coming out or holding up the runway for the slew of SR22's at my field. So yeah, I know I can fly slower, just no need to, and work speeds down to stall (steady tone) at touchdown which from my GoPro videos I use for training it looks like touchdown is around 40'ish.

With that said, my focus (training) right now is getting more comfortable at slower speeds. My A-10 past was near full throttle low altitude. A habit hard to break, i.e. comfort with knots. My flights ahead will be about keeping it slow and gaining more comfort with that.

I'll add that we all love watching the taildragger (STOL) videos on YouTube, or at least I do. But realizing what they make look easy is not necessarily easy and you have to train to that level. I've been out of the cockpit for 20 years so I'm regaining proficiency in every aspect. Taking my time and working on structured training as well. There was a recent YouTube video TSquared informed me of, a guy was talking about how it took him a while to become one with his plane and feel comfortable with the low and slow which I can fully relate. For those coming behind me and also have little experience with taildraggers, etc. take your time! This is just me, others are different, it's taking me time to regain proficiency and get back to the comfort level I was in my Air Force days.

[hawgdrvr]

Off topic (again) but here is my YouTube where I'm sharing some of my training videos. I have no intent to be a YouTuber but just sharing some flying videos and training. I have GoPro's I use for debrief and share with some other FX-3 drivers to discuss the lessons learned. I use one GoPro on the G3X to review speeds, AOA, etc. Another out front and another strut mounted (or on tail lift bar).

https://youtu.be/maFKj0sOUT0?t=406 (time started later when base turn is upcoming)

Info share among fellow pilots such as FX-3 owners is invaluable. I've learned a ton from TSquared and Turbopilot. I highly encourage FX-3 owners to talk to other FX-3 owners, etc. as it really helps. I may break down some videos as even learning lean assist took some discussion, Jeremy at TacAero keyed me in on that one that you had to be level/stabilized when doing lean assist and not start it while climbing out. I never leaned out, it wasn't discussed in my TacAero week training so I learned this later. While it seems simple to most things like this are not simple to newbies to this like me that haven't experienced this before. YouTube is a great learning resource as is fellow pilots of the same type. Thanks all here for sharing, Andy has been great as well!

[Dan L]

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At the factory, it was mentioned that some people are ordering FX's with carbon cub SS flaps, because apparently the SS flaps deflect to a higher angle. I don't know the differences otherwise.

That is an interesting comment. I have the original flaps and when the FX2 came out I demo flew an FX2 with the new flaps. When I made the trip to Yakima I had it in my mind that if I could get the FX2 to fly slower than my EX that I'd buy a new kit. The short of it is I couldn't get it any slower. Here's a link to what I wrote about it back then.

https://forum.cubcrafters.com/showth...ht=flew+Yakima

I remember seeing Stid's EX a few years ago with the P-Stol flaps. If he sees this maybe he'll comment on the flaps.

[Andy]

Everyone will have their own preferences but I like to fly every approach as though I'm landing on a 500 ft strip. That's where technique will really matter and, if that's not the way you usually fly, it's not likely you'll get it right when you need to.

The controllers at my base airport have become used to me and my FX-3. They know where I want to turn off and that I'll want to turn base before reaching the approach end and land 2/3 of the way down the runway. When traffic does not allow that, and forces me to extend downwind, I stay high until I intercept the same steep glide path.

For straight in approaches the other direction I stay clean and fast until about 1/4 mile final then slow, flaps out, again intercepting the desired steep approach to the aim point.

I'm amazed, and a bit shocked, that TAC Aero didn't teach leaning technique for the FX-3.