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Stalls & spins - any test pilot pireps out there?

 
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davidjoyce(at)doctors.org
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PostPosted: Sat Jan 22, 2022 3:15 am    Post subject: Stalls & spins - any test pilot pireps out there? Reply with quote

On my biennial renewal flight I was deliberately stalled in a mono gear up steep turn (possibly 60 degrees). The plane went very abruptly into a nose down rapidly rotating spin. No problem correcting with standard recovery. A friend did something similar in his trigear and found himself abruptly in an inverted spin. He let go of everything whilst trying to think what to do and the spin corrected itself. The moral for me is think carefully before trying these moves and certainly give yourself lots of height. Regards, David Joyce, GXSDJ


On 2022-01-21 23:37, Peter pender wrote:
Quote:
--> Europa-List message posted by: "Peter pender" <ppen(at)live.com.au (ppen(at)live.com.au)>Hi Pete,Will have a go at crossed control stalls one day and report back, but as an aside I was quite surprised at the difference in accelerated stalls gear up and down(mono). In mine anyway if others are similar I can see why some have come to grief turning onto final.Cheers PeterRead this topic online here:http://forums.matronics.com/viewtopic.php?p= --> http://www.matronics.com/; https://matronics.c===================


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budyerly@msn.com



Joined: 05 Oct 2019
Posts: 205
Location: Florida USA

PostPosted: Sun Jan 23, 2022 5:03 pm    Post subject: Stalls & spins - any test pilot pireps out there? Reply with quote

Ron,
I have never noticed droopy ailerons. A laminar flow airfoil needs no reflexed up or down for reduced drag. The Europa is not a Cessna or Piper flat bottom airfoil.
Let me be clear, there are aircraft that have interesting aileron rig. To name a few:
Ailerons that have slop at the center position and the ailerons actually float.
Ailerons that are not balanced and under G load droop because of poor geometry of the aileron quick disconnect.
Poor QD geometry leading to interesting slippage and ailerons that have as much as 1/4 inch play up, OK at the center, and tight at the bottom. That is a build error or sloppy construction.

Try this: Lock your aileron in the wing rack (since you are not flying this winter) and try to move your belcrank with your hand. If you can flex the mechanism look for loose screws.

Build the plane like the book then test fly please. You are not going to do better than ELSA or the prototypes.

Best Regards,
Bud Yerly

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budyerly@msn.com



Joined: 05 Oct 2019
Posts: 205
Location: Florida USA

PostPosted: Sun Jan 23, 2022 6:14 pm    Post subject: Re: Stalls & spins - any test pilot pireps out there? Reply with quote

David,
I am perplexed. It is true that most of the used "deal of the century" aircraft that came through my shop for evaluation or repair took on an average of 350 man hours to bring them up to Annex E and flight standards.

I have never had an aircraft from my shop display any charachteristic you describe. Even 139AB which had the right wing incidence at 3.1 degrees and the left at 2.6 degrees never rolled over and into a spin. Simply relaxation of back pressure broke the stall. Yes, the wing drop was entertaining, but only through complete disregard for normal flight stall techniques (i.e. adding aileron and leaving ones feet flat on the floor) and nearly full aft stick would the plane break into a severe un-commanded roll. (Fixing 139AB is a long story but 450 hours later and $20,000 it is a fine flying airplane.) If you know of another aircraft with such characteristics, I suggest you advise the owner to fix the darned thing.

For everyone else, I don't intend to upset anyone. I've done a paper on my thoughts on stalls on the Europa expanding my techniques articles. I've omitted the glider wing stall spin as I found it benign and not worth talking about. In any case, spin entry had to be done with full aft stick and full rudder to gain entry. Proper spin recovery controls quickly broke the stall and rotation. The mass of the glider winged aircraft meant more rudder was used to quicken the stop of the rotation than on the short wing. I only did one turn in the glider as I didn't have a chute and the required safety gear to do spin testing here in the States for a full three turns.

Attached is my synopsis of stalls in the Europa XS/Classic. I've also included a second hand buying paper

Bottom line, if you find your Europa will stall straight ahead fine using my techniques for yaw control and it behaves differently in an accelerated stall, there is a control not operating properly which should have been identified on inspection.

I have found that most scary Europa stall characteristics are build rig errors that have gone ignored and missed by inspectors, and most are pilot proficiency and training issues.

Best Regards,
Bud Yerly


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rparigoris



Joined: 24 Nov 2009
Posts: 709

PostPosted: Mon Jan 24, 2022 7:51 am    Post subject: Re: Stalls & spins - any test pilot pireps out there? Reply with quote

Hi Bud Thank you for great information on Stalls and Spins! I paid careful attention to making sure the pivot for aileron was precisely aligned on fuse and wings. No slop. No change in free play.

That said if I pick up on the tip of each wing by about 300 lbs using my pump jacks, the wing deflects upward as expected and the ailerons droop some (wash in).

Did you ever fly with 1/8" reflex which would probably become no reflex when pulling 2 Gs in an accelerated stall compared to no reflex at 1g which will probably become 1/8" wash in when pulling 2 Gs and seeing if the spin behavior is more benign?

I'm pretty certain Don Dykens incorporated just the right amount to keep the tips flying when stalling. Did he count on wash in occurring when pulling Gs? No question that ailerons set even work, but for a newbie Europa Flyier flying an unproven aircraft, does 1/8" reflex taint things in favor of a more docile spinner? I have an XS, not Classic. Thx. Ron P.


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budyerly@msn.com



Joined: 05 Oct 2019
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Location: Florida USA

PostPosted: Mon Jan 24, 2022 11:50 am    Post subject: Stalls & spins - any test pilot pireps out there? Reply with quote

Ron,
No offense but picking the wing tip up verses a distributed wing load achieves different bending loads on the wing. I reject your wingtip test as definitive. The outboard wing is nearly 40 square foot, and at 13 pounds roughly per square foot the tips can load up to about 520 pounds distributed between the two wings with most of the load forward of the main spar at an angle of about 10-15 degrees off vertical and forward. So simply lifting the tip doesn't hack it for a deflection. I do agree that the ailerons may droop a bit at maximum G. However, ask yourself, are you pulling 3.8 Gs normally at the stall. No most do stalls at or near one G and accelerated stalls normally no higher than 2-3 Gs so if there is any bending down of the ailerons it would be consistent between wings. This is nothing more than an academic exercise and doesn't really apply to building and flying in my opinion.

I never modify/fly a plane by adding reflex or modifying the wing without flight testing and in consort with the designer, I again reject the idea of pre-modifying based on non definitive flight tests. If you choose to experiment, please note that if you have flight difficulty remember to warn readers of your non standard modification first.

The wing at zero sweep and washout designed is excellent. You may need to read between the lines on my stall synopsis a bit. The root stall tends to move slowly to the tip unless the wing is warped or damaged and repaired out of rig. Most tapered wings have between 2-4 degrees of twist to make this happen. Again, if one does not maintain coordinated flight at the stall you will be surprised in any airplane when a wing drops. I'll add more on this in another reply on aileron use and rolling off of the Europa in accelerated stalls.

Sorry I don't experiment on a perfectly good wing.

Best Regards,
Bud Yerly

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dmac7



Joined: 05 Apr 2019
Posts: 8
Location: Canada

PostPosted: Tue Jan 25, 2022 1:45 pm    Post subject: Re: Stalls & spins - any test pilot pireps out there? Reply with quote

David Joyce thank you for sharing your experience much appreciated. Though it doesn't really shock me. Maybe a little yaw in the stall? Accelerated stalls come with more drama than unaccelerated stalls, good you had height to spare. and forward CG.

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budyerly@msn.com



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PostPosted: Tue Jan 25, 2022 5:17 pm    Post subject: Re: Stalls & spins - any test pilot pireps out there? Reply with quote

Guys,
I found typos and added drawings on my Europa Stall Spin Paper.

See pdf attached.

Best Regards
Bud Yerly


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Fred Klein



Joined: 26 Mar 2012
Posts: 492

PostPosted: Wed Jan 26, 2022 12:52 pm    Post subject: Stalls & spins - any test pilot pireps out there? Reply with quote

Bud…thanks, with profound appreciation…Fred

Quote:
On Jan 25, 2022, at 5:17 PM, budyerly(at)msn.com wrote:



Guys,
I found typos and added drawings on my Europa Stall Spin Paper.

See pdf attached.

Best Regards
Bud Yerly



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