Spin testing

Does anyone know if Cirrus has spin tested the SR20 or SR22 as part of certification, or was that waived because of the 'chute?

Mike

The use of the chute for spin recovery was judged by the FAA as providing an equivalent level of safety, so the Cirrus did not have to demonstrate that it met the spin requirements of FAR23. The JAA are apparently baulking at providing the same dispensation, so it is likely to be necessary for Cirrus to complete the spin testing in order to get European certification.

I have been told that the spins done by Cirrus’ test pilots showed recovery from spins to be conventional, but that doesn’t mean it fully meets the FAA certification requirements at this time.

It is my understanding that, during CAPS testing, the CAPS was deployed during a spin. I recall that the deployment was initiated after a complete rotation.

Thanks for the info. I was told that it wasn’t tested, but didn’t believe it. Guess I was wrong.
Mike

Mike: To confirm and supplement what Clyde said; indeed individuals who work or have worked for Cirrus have unofficially told me that the aircraft were indeed spin (spun) in flight testing, BUT not to the extent required to complete the “full FAA spin series.” Indications from the company seem to imply that they will complete the Spin Series to satisfy European certification requirements.

They also added that the airplane is difficult to get into a spin and conventionally to recover. However, in later conversations they indicated that recovery may not be easy. (This seemed like a contradiction to me, but I am just reporting the conversations. I purport to be neither an aeronautical engineer or test pilot.) The comments about spin recovery or at least the aircraft’s attributes, were attributed to the stall resistant features built into the wing. While delaying a stall and keeping ailerons effective, they may have negative side affects once in a spin. I did not infer from these comments that the aircraft was either unable to meet the current spin series requirements (CAR 23-e?) or the older FAA certification requirements which apply to airplanes such as the Cessna 170/180/200/210, Piper indian and Beech Bonanza series.

As always, everything I have ever read tells me that if a plane isn’t stalled it won’t spin and as long as it is coordinated, even if it is in a stall, it won’t spin.

Marty

In reply to:


As always, everything I have ever read tells me that if a plane isn’t stalled it won’t spin and as long as it is coordinated, even if it is in a stall, it won’t spin.


Marty,

The first statement is correct. The second statement is only correct in controlled circumstances. What is the reason for the stall? Ice? Turbulence? Instrument failure in IMC? Disorientation? Little green men? [;)]

Whatever the case, except for the little green men thing, many stall-spin scenarios may be out of our “control” per se. Doesn’t mean that you can’t recover, but you may get into a spin even though you are trying your best to avoid it.

But, yes, maintaining a coordinated stall is key to avoiding a spin scenario.

Actually, it might be better to think about how spins begin. In an incipient spin the airplane is not actually stalled. The high wing has a lower angle of attack than the low wing and, therefore, generates more lift than the low wing. The difference in lift increases until the airplane is in a stable spin around its center of gravity. Spin entry can be coordinated or uncoodinated.

When I was in Duluth 3 weeks ago, test pilots had just flown in to conduct spin testing starting the first week of October

I had know yesterday about Cirrus:
Re: spin test: “…Because Cirrus had aileron and rudder command crossed, put it in inadverted spin is more difficult; as so as for same reason exit from an spin will result more difficult for the Cirrus”.

I didn’t know that Cirrus had crossed aileron rudder command.

What do you know about it?

I’m not sure I agree that you can enter a spin in a coordinated state (whether you call it flight or a stall). For the plane to spin, one wing must have more lift than the other, and it’s hard to see how this can occur except in an uncoordinated condition.

Other matters: Can someone explain to me why the FAA spin testing is so time-consuming and expensive to complete? It seems to me a good test pilot ought to be able to demonstrate every type of spin a dozen times in a couple of afternoons??? Why is this such a tough certification issue?

David

Sounds like they were referring to the rudder-aileron interconnect. You will notice (e.g. when taxying) that if you put in full rudder, then you also get some aileron deflection to the same side. This could be a problem in a spin recovery, since for spin recovery you want to leave the ailerons neutral while stopping the rotation with rudder.

Michael,

Did you hear anything about the plans for the spin testing?

Thanks,
Roger

In reply to:


It is my understanding that, during CAPS testing, the CAPS was deployed during a spin. I recall that the deployment was initiated after a complete rotation.


That’s true – I have the video footage of that test.

  • Mike.

In reply to:


It is my understanding that, during CAPS testing, the CAPS was deployed during a spin. I recall that the deployment was initiated after a complete rotation.


If you are a COPA member, you can find both .avi and .mov movie files of CAPS deployment in both level flight and in a spin at http://www.cirruspilots.org/members/docs/index.html. One of the benefits of membership. [:)]

no. Only that test pilots had arrived and would be conducting more extensive spin testing over the next few weeks.

It has to be done at a multitude of weights, CG locations, flap settings, and power settings. If you multiply out the number of combinations, you get an idea of why it is a burdensome requirement.

Dave,
A sudden gust or turbulance can easily cause unequal lift even during a coordinated turn.
Bill

It has to be done at a multitude of weights, CG locations, flap settings, and power settings. If you multiply out the number of combinations, you get an idea of why it is a burdensome requirement.<<

Well, that makes sense. But now it makes me curious about a couple of more questions: If Cirrus was not required to go through spin certification based on the ballistic chute, why wouldn’t the FAA require proving the chute’s performance under the same number of weight, CG, settings etc combinations? (I assume this wasn’t done, since it would clearly take longer than traditional spin testing…imagine the number of times you’d have to repack the chute!). Thus, if all the parameters have not been tested, how does the FAA know the chute will deploy properly in all cases? Eg, what if the Cirrus entered some sort of weird tumble, or inverted spin, based on engine settings or extreme aft CG? Logically, it seems odd to me that the chute could substitute for spin testing, if the chute is not proven to work in all the same spin configurations that spin testing includes.

And isn’t this a similar issue with Lancair. I seem to recall that they avoided spin test requirements by virtue of their “rudder limiter” that kicks in at slow air speeds?

Maybe the chute and the rudder limiters are just a tacit admission by FAA that they go overboard with spin testing.

And isn’t this a similar issue with Lancair. I seem to recall that they avoided spin test requirements by virtue of their “rudder limiter” that kicks in at slow air speeds?

Maybe the chute and the rudder limiters are just a tacit admission by FAA that they go overboard with spin testing.

FAA has a policy of equivalent levels of safety. The manufacturers have the option of demonstrating either spin recovery (Diamond), spin resistance (Lancair), or alternate means of recovery (Cirrus). I think a case could be made that since most spins occur at too low an altitude for recovery (either traditional or parachute) that Lancair spin resistance is the only real world spin solution.

In reply to:


if the Cirrus entered some sort of weird tumble, or inverted spin, based on engine settings or extreme aft CG


FAR 23 doesn’t require demonstration of recovery from inverted spins in any case. I don’t know the specifics of the FAA’s determination of ELOS (Equivalent Level Of Safety) in the case of the Cirrus, since this is in a memo referred to in the Type Certificate Data Sheet, but so far as I am aware, that memo is not publicly available (maybe an FOI request would get it).

In reply to:


And isn’t this a similar issue with Lancair. I seem to recall that they avoided spin test requirements by virtue of their “rudder limiter” that kicks in at slow air speeds?


It appears to be. The Lancair TCDS also has a reference to ELOS in meeting stall/spin requirements. My understanding is that with the aid of the low-airspeed rudder limiter, the Columbia was able to be shown to be “spin-resistant” as per FAR 23.221(a)(2) - which basically requires that you have the stick fully back and can bank and turn the plane through 360 degrees using full aileron and rudder authority without it entering a spin. Apparently the Columbia couldn’t quite meet that without restricting the rudder travel (in one direction only) at low airspeeds.