Today I was waiting to do a forum, had a few minutes so I sat in on the last part of the one presented in the next tent.

It was about design features that can be use to help a plane resist stalls and spins.
Now, I only got the last few minutes, and I don't have the listing in the paper givng the exact title or the presneters name, don't fly into defensive mode over the mention of Cirrus. The seems to be an aerodynamic expert, and she spoke very well and matter of fact, seems to know what she is talking about, and I don't think she is trying to sell anthing or any brand.

She mentioned a cuff on the wing as a helpful design. She also mentioned slotted ailerons as being good, which surprised me since I though sealed ailerons were oneof the advances of the P-51.
She mentioned Cirrus and said they did some spin testing at first, but only one turn spins and at forward cg. I know the FAA considers the first two turns as only the entry or "incipient phase" of a spin and things can deteriorate after 2 turns. She didn't say what, if any problems Cirrus found, or why they didn't continue the tests. She mentioned the standard of ALOS? which means as safe, and that Cirrus got certification under this due to the chute.
She also mentinone the testing of Colombia 300 and 400. I am not sure of the details, but I think she said the 300 had zero stall spin fatalities.

It was interesting enough that, even though I don't have these planes, I'd like to go back and hear her whole presentation. Others might find it worthwhile also.
She also has written a book, and again this was a spur of the moment thing and I didn't even have a pen to write anything down. I will try to find more out and update this topic.
It is High Alpha and Stalls, Sonja Englert.

She's got a very interesting biography:
http://www.caro-engineering.com/

I'd love to hear one of her presentations. She's got several interesting books it seems too.

It is an ELOS (Equivalent Level of Safety). If you can make the case that some design feature compensates, you don't have to comply with a design rule to the letter. In the case of the Cirrus, the normal category requirement to be recoverable after a one turn spin is waived.
Here is a link to the Cirrus ELOS...

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgELOS.nsf/0/5c8c6ff47e9416148625762c00434aea/$FILE/ACE-96-5.pdf

You can search them up here...

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgELOS.nsf/MainFrame?OpenFrameSet

Once you get the ELOS--- there is no business case to spend the money to do a full spin matrix. A full spin matrix is time consuming and expensive- and at least two "recent" prototypes have been lost to spin testing (the GA-8 and one of the Lancair 400)

Sonja is a great resource... I hired her for a cooling consult on my turbo Cardinal... Still working through her three pages of suggestions, and have completed one of the three flight tests she recommended.

I was also in her session yesterday... She's on a 8:30 tomorrow on engine cooling.

Paul

Slotted ailerons would act in a similar way to the slotted flaps you find on lots of aircraft (Cessnas to 747s).

For the flaps: While initially counter-intuitive, allowing the air to flow up from under the control surface will effectively "energize" the boundary layer on the top, aft section. This will help keep the boundary layer attached to the airfoil. When attached, you don't have to contend with (as much) drag, and more importantly, the airflow behaves as intended for that surface.

In the aileron case: Similar concept... We're actually concerned about air separating on the top of the low-wing aileron. If we could keep this attached (via a slotted system) then we could keep the flow attached well enough to affect a wings-level roll via aileron (as opposed to just rudder). Additionally, flow separation generates large quantities of drag, exacerbating the problem/spin.

For the P51: I don't know much on this design. I would assume the engineers placed a great importance on speed & maneuverability, so the sealed aileron was implemented to reduce drag and meet those goals. In a GA airplane, we're not dog-fighting and can afford some drag if it helps prevent avoid spins. The designs have different compromises the engineers were willing to accept, based on the intended mission/performance.

Sounds like she's a great speaker... wish I could have been there!

I was really impressed with her even only hearing about 15 min,
Her name didn't seem familiar, I had no idea she was so active and so widespread as a writer.
It impressed me that she wasn't trying to sell anything, except her book, and unlike so many speakers, she didn't have a product or pet theory.
I wish she was doing this forum again, but the next one is on cooling.

The slotted ailerons are called Frise-type ailerons and the primary advantage is to minimize adverse yaw.

For an airplane to turn, it must be banked so the total lift is divided into a vertical component that supports the weight of the airplane, and a horizontal component that causes the turn.

To make a left turn, the aileron control is moved left. The right aileron moves down, increasing the camber and lift of the right wing, thus causing it to rise. The left aileron moves up, decreasing the camber and lift of the left wing. The adverse yaw problem arises because lift and drag are directly proportional. With the increased lift of the right wing comes increased drag, and the decreased left on the left wing causes a decrease in drag.

These combine to cause the nose to yaw to the right. This momentary yaw (to the right in a left turn, to the left in a right turn) is adverse yaw.

When the aileron control of Frise-type ailerons is moved, an offset hinge causes the forward part of the upward deflected aileron to be exposed below the wing (creating extra drag). Through this design adverse yaw is minimized.

Mike

Joe, I am not a Cirrus owner nor prospective Cirrus customer, nor am I selling another brand.
And I don't want to make this into a topic about Cirrus.
But once upon a time, they were a new design, and other than the chute they had a lot of interest and a lot of promotion about new features and stall/spin resistance.
And they certainly have a lot of promotion around them now.
If we go back to the start, even to that pusher prototype, the chute was not a big thing to most people, I never thought it would work as well as it did. I don't think it was the selling factor then as now.
I sure wouldn't pay extra to put a side controller and fixed gear on my Bonanza, probably not plastic body, but I would strongly consider the addition of a chute if it was available.

But if one comes out with a new design in almost anything, it would be great if it was an entire step up. With Cirrus, not counting the chute, it is more of a step sideways. It would be as if Samsung came out with a new cell phone which was voice activated , hands off, but which could no longer be used with your fingers.
I didn't put it in the first post, but Sonja did say that, except for the chute their safety record was no better than average, maybe a little worse. I don' know if those or her figures or the ones from the AV Con report a few years back.

What, to me would be ideal, would be if Cirrus had come out with a new plane, better in every way, and INCLUDING spin recovery, and THEN ADDED the chute. Now you'd really have something.
Maybe that is a high bar to set,and would be more expensive.

Sonja didn't say, but I think there was a design or aerodynamic reason why they could not or did not meet the spin test standards. It is very unlikely that it was just " a business decision". My guess is that as cg moved aft the problem would worsen. I was talking to an Loockheed engineer about hi Lancair Legacy and he said it should never be spun as the tail was too small, too little rudder to recover well.
So a lot of promo about stall resistant and new design and safety, turns out to be, not better than what was before, EXCEPT for the chute as a last resort. And we must remember that landing under the chute is still an accident, not what one would set out to do on any flight. It is not like flying a sailplane and landing without an engine.

I would like to have her talk about this approach as per other common planes. She was including Col 300 and 400, but I can't recall all she said. She did she one was good on spin recovery.

Spin recovery is no cinch, when Beech went to the C model they had problems, think lost one despite all the A and B models and all the spins they can and have done.

My understanding is that Cirrus did complete the full set of spin testing to comply with EASA certification in Europe. So it seems it was not just "a business decision" but simply a matter of completing certification more efficiently after the ELOS was issued.

Perhaps Cirrus should get together with Red Bull and put together an aerobatic demonstration so this spin issue can finally be put to rest!

Cirrus, or at least Patti Wagstaff has already done that. She was hired by Cirrrus to do an acro show for a couple of years. It seemed to fly well enough, but no spins in that show. I have not seen Patti this year, I'd like to ask her is she ever spun one.

I think her shows may have given Cirrus some more marketing pull with performance oriented pilots, but then Patti is a long way from other pilots.