NTSB urges grounding of all Zodiac CH-601XL's

[[email protected]]

http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
Designed by Zenair.
Just saw it on CNN.
Karl

[Jim Logajan]

" > wrote:
> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
> Designed by Zenair.
> Just saw it on CNN.
> Karl

I'm assuming they are only talking about the handful of SLSA Zodiacs,
because I don't think the ones built as experimental aircraft can be
identified in any unambiguous way - and they don't have any common
manufacturer. I presume they'd have to try and hunt them all done manually
(somehow?) and presumably revoke or suspend each aircraft's airworthiness
certificates or otherwise change their operations limitations.

[Brian Whatcott]

wrote:
> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
> Designed by Zenair.
> Just saw it on CNN.
> Karl

Ouch! Control flutter and reduced sick force per G at high g

Well, this is homebuilders heaven - so I suppose we could use a
reminder that balancing control surfaces, specially tail feathers,
can help stop the onset of flutter, that loose control wires
and rods can encourage.....

Brian W

[150flivver]

On Apr 14, 8:36*pm, Brian Whatcott > wrote:
> wrote:
> >http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
> > Designed by Zenair.
> > Just saw it on CNN.
> > Karl
>
> Ouch! * Control flutter and reduced sick force per G at high g
>
> Well, this is homebuilders heaven - so I suppose we could use a
> reminder that balancing control surfaces, specially tail feathers,
> * can help stop the onset of flutter, that loose control wires
> * and rods can *encourage.....
>
> Brian W

How do you balance ailerons that aren't hinged?

[Gig 601Xl Builder]

150flivver wrote:
> On Apr 14, 8:36 pm, Brian Whatcott > wrote:
>> wrote:
>>> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
>>> Designed by Zenair.
>>> Just saw it on CNN.
>>> Karl
>> Ouch! Control flutter and reduced sick force per G at high g
>>
>> Well, this is homebuilders heaven - so I suppose we could use a
>> reminder that balancing control surfaces, specially tail feathers,
>> can help stop the onset of flutter, that loose control wires
>> and rods can encourage.....
>>
>> Brian W
>
> How do you balance ailerons that aren't hinged?


Well they are hinged just that the hinge is an extension of the upper
skin of the aileron. Interesting point though. It seems that most if not
all of the accident aircraft did use a more traditional piano hinge?

[Brian Whatcott]

150flivver wrote:
> On Apr 14, 8:36 pm, Brian Whatcott > wrote:
>> wrote:
>>> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
>>> Designed by Zenair.
>>> Just saw it on CNN.
>>> Karl
>> Ouch! Control flutter and reduced sick force per G at high g
>>
>> Well, this is homebuilders heaven - so I suppose we could use a
>> reminder that balancing control surfaces, specially tail feathers,
>> can help stop the onset of flutter, that loose control wires
>> and rods can encourage.....
>>
>> Brian W
>
> How do you balance ailerons that aren't hinged?


You've got me: how DO the ailerons work on a CH-601XL?

Brian W

[Gig 601Xl Builder]

Brian Whatcott wrote:
> 150flivver wrote:
>> On Apr 14, 8:36 pm, Brian Whatcott > wrote:
>>> wrote:
>>>> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
>>>> Designed by Zenair.
>>>> Just saw it on CNN.
>>>> Karl
>>> Ouch! Control flutter and reduced sick force per G at high g
>>>
>>> Well, this is homebuilders heaven - so I suppose we could use a
>>> reminder that balancing control surfaces, specially tail feathers,
>>> can help stop the onset of flutter, that loose control wires
>>> and rods can encourage.....
>>>
>>> Brian W
>>
>> How do you balance ailerons that aren't hinged?
>
>
> You've got me: how DO the ailerons work on a CH-601XL?
>
> Brian W

Go here and scroll about half way done the page.

But as I mentioned most if not all the accident aircraft had regular
hinges.

[Brian Whatcott]

Gig 601Xl Builder wrote:
> 150flivver wrote:
>> On Apr 14, 8:36 pm, Brian Whatcott > wrote:
>>> wrote:
>>>> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
>>>> Designed by Zenair.
>>>> Just saw it on CNN.
>>>> Karl
>>> Ouch! Control flutter and reduced sick force per G at high g
>>>
>>> Well, this is homebuilders heaven - so I suppose we could use a
>>> reminder that balancing control surfaces, specially tail feathers,
>>> can help stop the onset of flutter, that loose control wires
>>> and rods can encourage.....
>>>
>>> Brian W
>>
>> How do you balance ailerons that aren't hinged?
>
>
> Well they are hinged just that the hinge is an extension of the upper
> skin of the aileron. Interesting point though. It seems that most if not
> all of the accident aircraft did use a more traditional piano hinge?


Ah yes, a flex-hinge - a neat concept.
To balance a surface hinged with whatever, there are several choices.
1) (traditional) a leading horn outboard or inboard of the fixed
surface with a lead weight up front.
2) a lower aileron surface that comes further forward than the upper
surface, and that's leaded on its front seam. Like the Cessnas.
3) an aero and mass balanced extension - often seen on rudders:
a leading extension that balances the rudder mass, that reduces torque
along the rudder, and reduces pedal force. Some extensions are just for
aero effect.

Brian W

[cavelamb[_2_]]

Gig 601Xl Builder wrote:

>>
>> You've got me: how DO the ailerons work on a CH-601XL?
>>
>> Brian W
>
> Go here and scroll about half way done the page.
>
> But as I mentioned most if not all the accident aircraft had regular
> hinges.


I've flown a 701 with the hingless hinges.

The ailerons felt very stiff in flight.

I can well believe that set-up would prevent flutter -
or at least move the resonant response way up there.

[Ron Wanttaja[_2_]]

Jim Logajan wrote:
> " > wrote:
>> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
>> Designed by Zenair.
>> Just saw it on CNN.
>
> I'm assuming they are only talking about the handful of SLSA Zodiacs,
> because I don't think the ones built as experimental aircraft can be
> identified in any unambiguous way - and they don't have any common
> manufacturer. I presume they'd have to try and hunt them all done manually
> (somehow?) and presumably revoke or suspend each aircraft's airworthiness
> certificates or otherwise change their operations limitations.

You're right, I don't think they can formally take action against the
Experimental Amateur-Built Zenairs. And if they do, it wouldn't last
long.... the "manufacturer" of the aircraft can "correct the condition"
any way they see fit.

I count about 480 total Zenair 601s on my January 2009 edition of the
FAA registration database, of which about 360 actually have
airworthiness certificates (my assumption is that the rest are
homebuilts under construction). Of those, 54 are listed as SLSAs.

Ron Wanttaja

[Frank Stutzman[_3_]]

cavelamb > wrote:
>
>
> I've flown a 701 with the hingless hinges.
>
> The ailerons felt very stiff in flight.
>
> I can well believe that set-up would prevent flutter -
> or at least move the resonant response way up there.

A 701?

Hingless hinges can be done on the 6xx series planes, but the 701
(according to the plans) uses hinges. Not to say that someone couldn't
do it on a 701, but it would seem to be a diversion from the standard
designe that would be of dubious value.

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Boise, ID

[Jim Logajan]

Ron Wanttaja > wrote:
> You're right, I don't think they can formally take action against the
> Experimental Amateur-Built Zenairs. And if they do, it wouldn't last
> long.... the "manufacturer" of the aircraft can "correct the
> condition" any way they see fit.

Here's the notice online, which in turn contains links to safety letters to
the FAA and ATSM International:

http://www.ntsb.gov/Pressrel/2009/090414a.html

The very first item NTSB recommends in the FAA letter
(http://www.ntsb.gov/recs/letters/2009/A09_30_37.pdf)
to the FAA is:

"Prohibit further flight of the Zodiac CH-601XL, both special light sport
aircraft and experimental, until such time that the Federal Aviation
Administration determines that the CH-601XL has adequate protection from
flutter. (A-09-30) (Urgent)"

I don't think the authors of that NTSB safety letter quite understand
experimental certificates and their ramifications. For example, there is at
least one builder who pointed out on the Matronics Zenith mailing list that
he built his aircraft using push rods, not cables.

[cavelamb[_2_]]

Frank Stutzman wrote:
> cavelamb > wrote:
>>
>> I've flown a 701 with the hingless hinges.
>>
>> The ailerons felt very stiff in flight.
>>
>> I can well believe that set-up would prevent flutter -
>> or at least move the resonant response way up there.
>
> A 701?
>
> Hingless hinges can be done on the 6xx series planes, but the 701
> (according to the plans) uses hinges. Not to say that someone couldn't
> do it on a 701, but it would seem to be a diversion from the standard
> designe that would be of dubious value.
>
Sorry, bad typo Frank, it was a LOW wing 601HD.

[Bob Kuykendall]

On Apr 16, 9:46*am, Jim Logajan > wrote:

> I don't think the authors of that NTSB safety letter quite understand
> experimental certificates and their ramifications...

Yup. They also don't seem to understand that someone who builds an
aircraft from a kit or from plans is under no obligation to register
that aircraft as having the same type as the kit prototype aircraft.
For example, many of the Schreder HP-series kit sailplanes have types
such as "Drew Two" and "RS-1" and "MR-3" instead of "HP-18" or "HP-11"
or "HP-14." So there are no doubt several CH-601XL aircraft to which
the NTSB's narrowly-worded letter A-09-30 does not apply.

Overall, I think that the NTSB, while perhaps meaning well, is being
too heavy-handed in asking the FAA to take this action. I think that
it would be far more constructive to work with Zenith and with
builders groups to make them aware of the issues and possible
mitigations. I think that it would be well within the FAA's purview to
firmly decline the NTSB's demands.

If they ground every CH-601XL, what else could or might they have
taken action against? Adventurers with their horizontal stabilizer
attachment issues? BD-5As with their marginal takeoff characteristics
and flaky engines? Vari-Ezes (not Long-Ezes) with their somewhat
marginal wing carrythrough strength and attachment plate corrosion
issues? And that's just a few experimental airplanes, to say nothing
about gliders or rotorcraft. In all of these cases the carnage has
been kept to a dull roar by kit makers and builder communities who
(usually) worked together to raise awareness of the issues and to
mitigate them.

Thanks, Bob K.

[Morgans[_2_]]

"Bob Kuykendall" > wrote

Yup. They also don't seem to understand that someone who builds an
aircraft from a kit or from plans is under no obligation to register
that aircraft as having the same type as the kit prototype aircraft.
For example, many of the Schreder HP-series kit sailplanes have types
such as "Drew Two" and "RS-1" and "MR-3" instead of "HP-18" or "HP-11"
or "HP-14." So there are no doubt several CH-601XL aircraft to which
the NTSB's narrowly-worded letter A-09-30 does not apply.

Overall, I think that the NTSB, while perhaps meaning well, is being
too heavy-handed in asking the FAA to take this action. I think that
it would be far more constructive to work with Zenith and with
builders groups to make them aware of the issues and possible
mitigations. I think that it would be well within the FAA's purview to
firmly decline the NTSB's demands.
*************************
Jim wrote:
I see both sides of it, but think it is high time that the NTSB made a real
effort to get some changes made, and the top change is to make all of the
owners aware of the problems, as they see them.

As far as the flutter issue goes, the case was made that even planes that
had proper tension on controll cables have had cases of catestrophic
flutter. It should not be that hard to get a mass ballance engineered, such
as a "C" shaped ballance that penetrates the wing ahead of the hinge point,
and attaches to top and bottom of the aileron.
*****************************
If they ground every CH-601XL, what else could or might they have
taken action against? Adventurers with their horizontal stabilizer
attachment issues? BD-5As with their marginal takeoff characteristics
and flaky engines? Vari-Ezes (not Long-Ezes) with their somewhat
marginal wing carrythrough strength and attachment plate corrosion
issues? And that's just a few experimental airplanes, to say nothing
about gliders or rotorcraft. In all of these cases the carnage has
been kept to a dull roar by kit makers and builder communities who
(usually) worked together to raise awareness of the issues and to
mitigate them.
**********************
Jim wrote:
It could be said that the NTSB should have taken a more active stand in many
of the cases you mentioned, and many more might be alive. It would be a
fresh breeze to see action taken before more "blood rules" have to be
written.

If this is the case, it would be wrong to let more die, just because that is
the way it has been done in the past.
--
Jim in NC

[kfvorwerk]

On Apr 14, 2:26*pm, " > wrote:
> http://www.cnn.com/2009/US/04/14/ntsb.small.plane/index.html
> Designed by Zenair.
> Just saw it on CNN.
> Karl

http://www.theledger.com/article/20090423/NEWS/904235050/1410?Title=NTSB-Ground-Amateur-Built-Zodiac-Aircraft