Icon: First FAA Spin Resistance Certification

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Sven
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Icon: First FAA Spin Resistance Certification

Postby Sven » Fri Feb 17, 2012 3:26 am

Flying a Mooney M20D. One of only 3 fixed-gear Mooney aircraft still flying.

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Royski
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Re: Icon: First FAA Spin Resistance Certification

Postby Royski » Sat Feb 18, 2012 8:24 am

Very interesting. AvWeb has a few more details including a link to the regulation FAR 23.221(a)(2) for spin resistance
http://www.avweb.com/avwebflash/news/IconA5MeetsElusiveSpinResistantStandard_206196-1.html

Code: Select all

(i) During the stall maneuvers contained in Sec. 23.201, the pitch control must be pulled back and held against the stop. Then, using ailerons and rudders in the proper direction, it must be possible to maintain wings-level flight within 15 degrees of bank and to roll the airplane from a 30 degree bank in one direction to a 30 degree bank in the other direction;
(ii) Reduce the airplane speed using pitch control at a rate of approximately 1 knot per second until the pitch control reaches the stop; then, with the pitch control pulled back and held against the stop, apply full rudder control in a manner to promote spin entry for a period of 7 seconds or through a 360 degree heading change, whichever occurs first. If the 360 degree heading change is reached first, it must have taken no fewer than 4 seconds. This maneuver must be performed first with the ailerons in the neutral position, and then with the ailerons deflected opposite the direction of turn in the most adverse manner. Power and airplane configuration must be set in accordance with Sec. 23.201(e) without change during the maneuver. At the end of 7 seconds or a 360 degree heading change, the airplane must respond immediately and normally to primary flight controls applied to regain coordinated, unstalled flight without reversal of control effect and without exceeding the temporary control forces specified by Sec. 23.143(c)

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cozy171bh
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Re: Icon: First FAA Spin Resistance Certification

Postby cozy171bh » Thu Feb 23, 2012 3:51 am

My airplane meets these requirements. While flight testing, I was able to apply full cross controls with aft stick against the stop (either power on or off) and the worst I would get is a spiral descent at relatively slow speed (not a spiral dive or spin). Aileron control at full aft stick permits me good roll maneuverability, albeit not as crisp as at higher speeds. Only catch: I had to build it myself!

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Laminar
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Re: Icon: First FAA Spin Resistance Certification

Postby Laminar » Thu Feb 23, 2012 9:56 am

When I find myself holding the minority opinion in hangar-flying discussions, I usually keep my mouth shut. Usually.

But when this topic comes up, I can't resist getting on the soapbox. Preventing spins is impossible, and holding the belief that flying a spin-resistant aircraft will keep you safe is just plain wrong.

All airplanes spin. Note that no one advertises a "spin-proof" airplane. A spin-resistant airplane will spin, and when it does, it will be an unfamiliar experience for everyone aboard, including the flight instructor.

An airplane that meets the FAA requirements for spin-resistance cannot be put into a classical fully-developed spin by means of normal control inputs. Fine. But that doesn't mean that the airplane cannot get into that condition through extreme maneuvers, improper loading, encounters with turbulence, or some combination thereof.

Also, we should note that the FAA requirements (thanks for quoting them, Royski) describe aircraft behavior for "7 seconds or a 360 degree heading change." What happens in the 8th second? At least some of the airplanes that can pass that test are probably already spinning; the spin just hasn't developed fully yet.

I am an instructor. I do spins every day (not every flight!). In my organization, no one goes solo without a complete understanding of the difference between spiral dives and spins. Shortly after solo they must demonstrate competence in recognition and recovery from both. Students working on their Commercial ratings must be able to recover to a heading.

Spin-resistant aircraft are not a bad thing. They give you a gigantic warning that you are doing something wrong. This is laudable. But promoting them as a solution to a training problem is irresponsible. Students should be trained.

And selling spin-resistance as a means of keeping everyone safe is gross malpractice.

Getting off the soapbox now.

-Rick Sheppe

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cozy171bh
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Re: Icon: First FAA Spin Resistance Certification

Postby cozy171bh » Thu Feb 23, 2012 11:56 pm

The EZ design, properly built and rigged, will not permit the aft wing to exceed its critical angle of attack. Burt Rutan refers to this characteristic as angle of attack limiting. The C/L on the canard is carefully determined to ensure it reaches its limit well before the aft wing.

Nevertheless, even though the wing will not depart, one must still be careful in the pattern, as at full aft stick with power off, and depending upon the gross weight and CG, although not stalled the aircraft can enter into a high drag condition which if not responded to quickly and properly, could result in a touchdown at a high enough sink rate to damage or destroy the aircraft. It is interesting that the solution to the sink is similar to an impending stall: lower the AOA and add power. The canard will protect against the classic base-to-final turn scenario, but as with any airplane, there are other ways to get into trouble....

So as Rick suggests, proper training, including training in the specific characteristics of the airplane you fly, is imperative.


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