NTSB Safety Alert CH 601

[Brian Whatcott]

Here's a model report on treating home-builders like grownups.
Highlights:
Mass balancing controls - tight control wires not enough

Reduced stick force per G at higher G made worse by aft CofG

Don't push the stick hard by mistake - it may be your last.

<http://www.ntsb.gov/recs/letters/2009/A09_30_37.pdf>

Brian W

[Bob Hoover]

On Apr 19, 5:49*am, Brian Whatcott > wrote:
> Here's a model report on treating home-builders like grownups.
> Highlights:
--------------------------------------------------------------------------

For anyone unfamiliar with bureaucratic formats, skipping to the last
page of the 12 page report, will give you a complete list of the
highlights. But the real message is more subtle than it appears. The
real message offers a polite Heads-Up to ALL American airmen, telling
us that if we can't keep our house in order there are plenty of
bureaucrats more than eager to jump in and take care of that little
matter for us. (Need I mention that bureaucrats don't come cheap?)

I STRONGLY suggest you read the whole report and be prepared to act on
it accordingly, when appropriate.

-R.S.Hoover

[Morgans[_2_]]

"Bob Hoover" > wrote

For anyone unfamiliar with bureaucratic formats, skipping to the last
page of the 12 page report, will give you a complete list of the
highlights. But the real message is more subtle than it appears. The
real message offers a polite Heads-Up to ALL American airmen, telling
us that if we can't keep our house in order there are plenty of
bureaucrats more than eager to jump in and take care of that little
matter for us. (Need I mention that bureaucrats don't come cheap?)

I STRONGLY suggest you read the whole report and be prepared to act on
it accordingly, when appropriate.

-R.S.Hoover

***********************************************8
Zactly. Even better, I can't imagine flying a plane that might come apart
in mid air (for no apparent reason) without fixing the problem causing it to
come apart. Perhaps people should consider that fact, too.

Does anyone know why there is no mass ballancing (as is common practice) on
the ailerons, in the first place?
--
Jim in NC

[Bob Kuykendall]

On Apr 19, 3:15*pm, "Morgans" > wrote:

> Does anyone know why there is no mass ballancing (as
> is common practice) on the ailerons, in the first place?

Mass balancing of ailerons may be common, but it is far from
universal. The majority of the Aeroncas and T-carts and high-wing
Pipers that are such a large part of the GA fleet do not have aileron
mass balancing.

Since mass balancing will often triple the mass of the surface to
which it is applied, it can have a serious effect on performance and
useful load.

Furthermore, even many fast (200 mph or so) airplanes that do have
mass-balanced ailerons are not 100% mass balanced. This category
includes Vans RV-series airplanes.

Thanks, Bob K.

[Jim Logajan]

Brian Whatcott > wrote:
> Here's a model report on treating home-builders like grownups.

I sure hope you're being facetious, since it asks that even experimental
aircraft be grounded, even though it contradictorily also states some
aircraft built from that design have already made design changes that make
the cited concerns mute.

The report also references material from the Matronics Zenith e-mail list
and uses it as supporting circumstantial evidence (the core argument is an
entirely circumstantial one of course.) Considering the total lack of
authentication of such e-mail material, it's a bit irresponsible to build
an already questionable circumstantial case on unauthenticated claims.
Also, I've browsed that list and the hysteria and infighting concerning
this issue in that e-mail list almost puts Usenet to shame.

There may indeed be a problem with the 601 design, though the report is
something of a shot-gun affair re causal factors. I guess if they put in
enough issues they can hope to later say "we told you so" no matter the
cause(s) found for the cited accidents.

[Brian Whatcott]

Bob Kuykendall wrote:
> On Apr 19, 3:15 pm, "Morgans" > wrote:
>
>> Does anyone know why there is no mass balancing (as
>> is common practice) on the ailerons, in the first place?
>
> Mass balancing of ailerons may be common, but it is far from
> universal. The majority of the Aeroncas and T-carts and high-wing
> Pipers that are such a large part of the GA fleet do not have aileron
> mass balancing.
>
> Since mass balancing will often triple the mass of the surface to
> which it is applied, it can have a serious effect on performance and
> useful load.
>
> Furthermore, even many fast (200 mph or so) airplanes that do have
> mass-balanced ailerons are not 100% mass balanced. This category
> includes Vans RV-series airplanes.
>
> Thanks, Bob K.
>

Fair comments.... some aircraft use fractional balancing - in the 1/2 to
2/3 region as a weight-saving measure. A hinge line aft of the aileron
leading edge is another tactic.

Brian W

[Brian Whatcott]

Brian Whatcott wrote:
> Here's a model report on treating home-builders like grownups.
> Highlights:
> Mass balancing controls - tight control wires not enough
>
> Reduced stick force per G at higher G made worse by aft CofG
>
> Don't push the stick hard by mistake - it may be your last.
>
> <http://www.ntsb.gov/recs/letters/2009/A09_30_37.pdf>
>
> Brian W


I forgot to mention a tactic used for improving pitch stick force per G.
Where an elevator rod or wire is connected by a pulley wheel or lever
- a mass on a fore and aft lever arm from the pivot provides a turning
moment which increases with increasing g, so as to increase the reaction
to elevator control force with g. This was the tactic used on the
Spitfire, if I remember....
There's another mass that is not structural like surface balances.

Brian W

[cavelamb[_2_]]

Brian Whatcott wrote:
> Bob Kuykendall wrote:
>> On Apr 19, 3:15 pm, "Morgans" > wrote:
>>
>>> Does anyone know why there is no mass balancing (as
>>> is common practice) on the ailerons, in the first place?
>>
>> Mass balancing of ailerons may be common, but it is far from
>> universal. The majority of the Aeroncas and T-carts and high-wing
>> Pipers that are such a large part of the GA fleet do not have aileron
>> mass balancing.
>>
>> Since mass balancing will often triple the mass of the surface to
>> which it is applied, it can have a serious effect on performance and
>> useful load.
>>
>> Furthermore, even many fast (200 mph or so) airplanes that do have
>> mass-balanced ailerons are not 100% mass balanced. This category
>> includes Vans RV-series airplanes.
>>
>> Thanks, Bob K.
>>
>
> Fair comments.... some aircraft use fractional balancing - in the 1/2 to
> 2/3 region as a weight-saving measure. A hinge line aft of the aileron
> leading edge is another tactic.
>
> Brian W

Below 120 knots or so, the excitation frequency from airflow is probably too low
to get too excited about (if you were an aileron, anyway).

Above that, things get closer to the fundamental excitation frequency of the
structure.


Richard

[[email protected]]

On Apr 19, 6:39 pm, Brian Whatcott > wrote:

> I forgot to mention a tactic used for improving pitch stick force per G.
> Where an elevator rod or wire is connected by a pulley wheel or lever
> - a mass on a fore and aft lever arm from the pivot provides a turning
> moment which increases with increasing g, so as to increase the reaction
> to elevator control force with g. This was the tactic used on the
> Spitfire, if I remember....
> There's another mass that is not structural like surface balances.

That's called a bobweight, and it's to give the pilot some sense of
the stress he's putting on the airframe. Many current aircraft use it.
Even the Cessna 185, IIRC, has it. See a service bulletin regarding
the bobweight on the Citation:
http://www.tc.gc.ca/CIVILaviation/certification/continuing/Alert/1999-05.htm

Dan

[Bob Hoover]

On Apr 19, 7:55*pm, wrote:
> See a service bulletin regarding
> the bobweight on the Citation:
> -------------------------------------------------------------------

Dear Dan,

On the Citation I believe you will find it is called the 'Robert
Mass'.

:-)

[jl]

Wanna see an airplane break up from flutter?

Watch the movie clip:

http://www.velozia.com/?p=1387

BTW, the Auguste Raspet Memorial Department of Aeronautical
Engineering at Mississippi State University does flutter testing on
airplanes, including experimentals. Bring your checkbook.

White Lightning designer and Citadel-educated engineer Nick Jones had
the White Lightning successfully tested there.

I have balanced a set of flight controls with lead embedded in the
leading edges--- rudder, elevator, ailerons --- for the White
Lightning; and no, they are not completely balanced, just enough to
avoid flutter up to about 350 kts. This is a 220 kt. cruise aircraft.

[Brian Whatcott]

jl wrote:
> Wanna see an airplane break up from flutter?
>
> Watch the movie clip:
>
> http://www.velozia.com/?p=1387
>
> BTW, the Auguste Raspet Memorial Department of Aeronautical
> Engineering at Mississippi State University does flutter testing on
> airplanes, including experimentals. Bring your checkbook.
>
> White Lightning designer and Citadel-educated engineer Nick Jones had
> the White Lightning successfully tested there.
>
> I have balanced a set of flight controls with lead embedded in the
> leading edges--- rudder, elevator, ailerons --- for the White
> Lightning; and no, they are not completely balanced, just enough to
> avoid flutter up to about 350 kts. This is a 220 kt. cruise aircraft.
>

Great post! That flying wing breakup looked kinda like a divergent
pitch oscillation to me. There is nothing like a first hand account
of a surface balancing - any idea what proportion of the control
surface weight was balanced? That would be an interesting value!

Regards

Brian W

[Jim Logajan]

jl > wrote:
> Wanna see an airplane break up from flutter?
>
> Watch the movie clip:
>
> http://www.velozia.com/?p=1387

Here's the proper way to handle flutter:

http://www.youtube.com/watch?v=a-qS7oN-3tA

Sorry - it's an experimental aircraft in the traditional sense, so probably
not topical for a "homebuilt" group. ;-)

[John Kimmel[_2_]]

Morgans wrote:
> "Bob Hoover" > wrote
>
> For anyone unfamiliar with bureaucratic formats, skipping to the last
> page of the 12 page report, will give you a complete list of the
> highlights. But the real message is more subtle than it appears. The
> real message offers a polite Heads-Up to ALL American airmen, telling
> us that if we can't keep our house in order there are plenty of
> bureaucrats more than eager to jump in and take care of that little
> matter for us. (Need I mention that bureaucrats don't come cheap?)
>
> I STRONGLY suggest you read the whole report and be prepared to act on
> it accordingly, when appropriate.
>
> -R.S.Hoover
>
> ***********************************************8
> Zactly. Even better, I can't imagine flying a plane that might come apart
> in mid air (for no apparent reason) without fixing the problem causing it to
> come apart. Perhaps people should consider that fact, too.
>
> Does anyone know why there is no mass ballancing (as is common practice) on
> the ailerons, in the first place?

The Zenair Zodiac uses wing warping. (They call it a "hingeless
aileron"). Looks pretty springy to me.
http://www.zenithair.com/kit-data/ht-aileron.html

John Kimmel

[Ron Wanttaja[_2_]]

John Kimmel wrote:

> The Zenair Zodiac uses wing warping. (They call it a "hingeless
> aileron").

Not all of them. Zenair has offered a piano-hinged aileron for quite a
while...the SLSA version of the CH601 uses 'em, and some kit builders
have opted for them. Two of the wing-failure accidents involved SLSA
Zenairs, which have the piano hinges. Haven't heard the type of
ailerons for the others.

Ron Wanttaja

[Gig 601Xl Builder]

Ron Wanttaja wrote:
> John Kimmel wrote:
>
>> The Zenair Zodiac uses wing warping. (They call it a "hingeless
>> aileron").
>
> Not all of them. Zenair has offered a piano-hinged aileron for quite a
> while...the SLSA version of the CH601 uses 'em, and some kit builders
> have opted for them. Two of the wing-failure accidents involved SLSA
> Zenairs, which have the piano hinges. Haven't heard the type of
> ailerons for the others.
>
> Ron Wanttaja
>
>

As best we can find out NONE of the accident aircraft had the hingeless
ailerons. This could explain why there has been no problems until the
last few years when the hinges started replacing the hingeless.

In fact the only commonality that I can find between the accident
aircraft is hinged ailerons and the sort of strange (for an plane that
the majority of the fleet is EXP-HB) fact that none of the aircraft were
flown by the builder.