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Juan Vega Jr
Joined: 13 Jan 2009
Posts: 157
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 Posted: Thu Jul 09, 2009 11:50 am Post subject: New Chris Heinz Letter Today |
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Jay,
your behind the eight ball yet again. If your read the letter from Chris, he is Basically saying in a nice way, what I said, it looks more and more everyday, that it is ultimatley an Owner Issue.
The guys that are scared to hear that it is not an engineering issue, need to move on or create their own self prescribed fix, even though there is no possible need for one.
Build it right, fly it right maintain it right, 601s are a great plane to own and fly.
Juan
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daveaustin2(at)primus.ca
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| Posted: Thu Jul 09, 2009 4:41 pm Post subject: New Chris Heinz Letter Today |
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Woa, hold on a minute, Wade. You don't need to balance the whole weight of
the ailerons! Do the calcs, please.
Dave Austin 601HDS - 912
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stormyflight(at)yahoo.com
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| Posted: Thu Jul 09, 2009 7:41 pm Post subject: New Chris Heinz Letter Today |
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Hi Paul,
In a previous post you indicated that without exception, it is the opinion of all aerospace community that balanced ailerons are required without exception on all aircraft of this type. I take a bit of an issue to this statement. I am an aircraft designer and am responsible for the design of General Atomics series of UAV's. These aircraft range in weight and performance from the Predator aircraft (very LSA-like) with a dive speed of 150 KIAS to Reaper (10500 lb gross weight) with a dive speed of 400 KIAS to our latest Avenger turbofan aircraft (15500 lb gross weight) with a dive speed in excess of 500 KIAS. They are operated by multiple customers throughout the world. Currently General Atomics aircraft log more flight hours than the rest of the USAF fleet combined.
Of the 12 aircraft I have designed for General Atomics over the last 16 years not a single model has had balanced ailerons. You really can't grab on to a specific design issue and and determine it's impact without looking at the system as a whole. Our aircraft are very carefully designed with very accurate finite element models being built concurrently with the design process. Once a prototype is built it then undergoes a very complete GVT which updates and validates the FEA model. This model is then run through a complete flutter analysis which identifies the different flutter modes and the speed at which they could occur. Aileron flutter is always way outside the desired flight envelope and therefore any weight dedicated to balance would be wasted. Of course you have to take into account the stiffness of the system as designed as well as maintained throughout the life of the aircraft. By the way, fleet hours have just surpassed 700,000 flight
hours with no instances of flutter.
Am I convinced that the XL has not flutter problems? Not entirely but only because of the few reported instances of cable tension dropping significantly over a very short period of time. I am convinced that if the cable tension is within the specified range, that flutter will not occur. My guess as to real culprit is the stick force gradient. The wings are being unintentionally pulled off which in my mind is a pilot induced occurrence and frankly should be easily remedied with a trailing edge device on the elevator and also could be mitigated by good training and piloting techniques.
While not under the auspices of the FAA (yet) none of our airworthiness representatives from the USAF, US Army, US Navy, Customs and Border Patrol, RAF, Italian Air Force or the Turkish Air Force have ever questioned our choice not to balance the ailerons..
Just a lowly representative of the current aerospace community,
Jim Machin
601XL, 0-200 almost ready!
--- On Wed, 7/8/09, Paul Mulwitz <psm(at)att.net> wrote:
| Quote: | From: Paul Mulwitz <psm(at)att.net>
Subject: Re: New Chris Heinz Letter Today
To: zenith-list(at)matronics.com
Date: Wednesday, July 8, 2009, 11:31 PM
Hi Tony,
First let me say your qualifications to understand the
technical details
of this issue are a lot better than mine. I believe
you are
convinced that flutter is not an issue for the XL based on
the German
test report.
However, you are not the FAA.. I don't believe
they will determine
that the XL has adequate protection from flutter no matter
what any
engineering reports say. I learned when I discussed
this issue with
them at Sun n Fun that they already believe the XL needs
balanced
ailerons and that nothing will change their minds on that
point.
Indeed, I believe the NTSB has the same opinion (but I have
no personal
proof of that position).
By talking to lots of FAA and industry folks who have been
around for a
long time I learned there is a belief that balanced
ailerons are needed
by all planes of this sort. History has shown that to
be true in
many different designs, and these guys are convinced that
the XL is no
exception to this rule.
The other news from those discussions is that the FAA will
not take any
action to prevent E-AB owners from flying their
planes. They just
don't care about experimental planes in that sort of
way. They do
care about factory built planes, but even those are safe
from FAA rule
making for at least a year. It takes them that long
(and longer) to
issue an NPRM and get to the final rule. That is the
process they
will use to issue a mandatory AD if they choose to go in
that
direction.
It is my hope that the whole problem will go away without
actual rules
from the FAA. All it takes is a group of design
changes from
Zenith/Zenair with some sort of mandatory implementation
from AMD for
S-LSA XLs. Then the FAA won't need to take any
regulatory
action.
For E-AB it is all up to the owner to decide what to do
with their
plane.
Paul
XL grounded
At 09:59 PM 7/8/2009, you wrote:
"------ the
National Transportation Safety Board recommends that
the Federal
Aviation Aviation Administration:
Prohibit further flight on 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"
(underling and
bold mine)
The above in my opinion as a retired
aerospace engineer, and
my Phase I flight tests, and the Zenith Flight tests and
the results of
the Modal surveys (Ground Vibration Tests - GVT) is that
the
recommendation by the NTSB to determine that the XL has
adequate
protection from flutter has been, in my lowly opinion,
satisfied.
Of course this assumes that the aileron control cables are
not slack, for
the reported real flutter was a result of slack cables -
the flutter
stopped once the IAS was lowered and did not repeat with
proper cable
tension, which per the GVT tests should be at a minimum of
10 pounds -
much less than the Zenith spec value.
The XL does though, like most all light
aircraft, have a
wing removal device called a "stick". I
personally like
the light stick forces of the XL, but as Mr. Henitz in his
letter stated
"Remember that, as with any light aircraft, if
you encounter
unexpected turbulence while cruising, ride it out rather
than fight it -
and slow down!"
Tony
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Scotsman
Joined: 27 Aug 2007
Posts: 89
Location: Johannesburg, South Africa
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| Posted: Fri Jul 10, 2009 3:40 am Post subject: Re: New Chris Heinz Letter Today |
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Guys...probably time to drop this one. There is no point getting all heated about it as you are not realistically going to be able to change each others' opinions.
The letter provides for consideration of both sides of the argument and importantly takes our safety (whether pilot and/or design impaired) as a primary concern. Let's wait and see what comes of of this as half of the nonsense on this thread will not achieve/solve anything.
I look forward to hearing from Chris after the review is complete. Enjoy your building in the meantime.
James
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James
Joined: 26 May 2009
Posts: 2
Location: Burke, VA
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| Posted: Fri Jul 10, 2009 5:58 am Post subject: Re: New Chris Heinz Letter Today |
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I, for one, hope you folks don't stop the debate. I find it damn entertaining.
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