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psm(at)att.net
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 Posted: Sun May 26, 2013 2:39 am Post subject: FAA Special Review Team final report.... Have questions... |
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Hi Chad,
I feel your pain. I will try to address all of the issues you raised,
but I'm sure I will forget some (rather than avoid them). Please feel
free to ask any questions again.
First, let me say I too have issues with my Zodiac XL with mods. The
good news is I had much greater ones and feel a lot better now than I
did when the upgrade was first announced. In general, I feel confident
in the structure now and believe it is possible to safely fly this
plane. There are limitations from my point of view, but the structural
issues seem to have been solved.
The biggest limitation for me is the light wing loading when combined
with unstable air. You get thrown around the sky compared to planes
with heavier wing loading. A C-150 would have similar problems but not
quite as bad. A C-182 will provide much more reliable and comfortable
transportation in most conditions, but you will pay for this comfort and
convenience.
I was not convinced the design was really fixed after reading the big
report from the FAA. I am not an aeronautical engineer and apparently I
didn't interpret the jargon correctly. I had a lucky meeting with the
guy whose name appears on the bottom of that report, Wes Ryan, at an
ASTM F37 meeting about a year after the report was issued. We discussed
the Zodiac issue for around 20 minutes. He convinced me that my
interpretation of the document was incorrect. They really did find
design problems with the Zodiac XL, and they really were fixed with the
upgrade package. History has supported this idea. There have not been
any more structural failures after installing the upgrade.
By the way, I have not changed the designation of my plane by adding the
"B" to its name. This is very difficult to do after the plane is
registered and I saw no reason to go through all that. Calling it
"Upgraded" is just as informative as adding the "B". It is different
for Zenith who sells kits long before they are registered.
There are a number of good reasons why you get different numbers from
different builders. All Zodiac XLs are not identical. Indeed, each one
is unique. There is no version control at Zenith, and changes are made
willy nilly whenever they feel like it. I doubt there is any reliable
way to track the changes that might appear in any given instance of the
XL. This is not really a problem, but it does mean you will get
differences from one plane to another. Of course it matters a great
deal what engine you mount after finishing building the kit. My point
is you shouldn't lose sleep over the different V speeds reported by
different builders. These planes are all built by amateurs and mostly
by people building their first plane. The rigging is less than optimum
on many of them. While there are problems with the design this is true
of all planes. The big problem - in flight structural failures - is
fixed now. The little problems are easy to live with if you operate the
plane in a conservative fashion and under weather conditions that are
reasonably benign.
I agree there is a problem in the rudder hinge area. I added bushings
to mine after seeing wear in the first few hours of flight. The
original design (at least the design as it appeared in my prints) had
steel rubbing against nylon each time the rudder was moved. This isn't
a good thing. Adding bushings so the steel is rubbing against a hard
and lubricated bushing seems to work a lot better.
I have nylon stops on the upward movement of the flaps. They are easy
to see from the top of the wing. Each flap has a couple of pieces of
nylon (1/8" sheet?) stuffed between the skin layers and riveted in
place. The nylon sticks out perhaps 1/4 inch from the top skin and the
flap presses against the stops. It is part of my normal preflight
inspection to try to wiggle the flaps. If they move at all I check to
make sure they are fully up. If they still move (they haven't yet in my
case) I would not fly the plane.
I do not know if the plane has been fully tested for flutter and other
bad juju since the mod was installed. This is a question for Zenith. I
am comfortable with the fact that history has shown the mod to be
effective. All the other possible tests only hope to predict the good
outcome we actually see now.
For what its worth I consider my XL to be as safe as you might expect
from any home built airplane. It has limitations, but they are not
particularly bad ones. I only fly in nice weather, and consider the XL
to be a fair weather plane. I would prefer to have a heavier and more
powerful plane but my lack of a medical certificate currently limits me
to light-sport designs. The XL is a reasonable example of the high end
of these planes. If the rules for medical certificates change in the
USA it is likely I will trade up to something bigger, heavier, and more
expensive to operate. Depending on the change I will probable go to the
upper limit of planes I can legally fly. For other people who treasure
inexpensive flying with reasonable cross country capability in good
weather I am comfortable recommending the XL as a possible choice.
Good luck,
Paul
Camas, WA
USA
On 5/25/2013 9:07 PM, SIDESLIP wrote:
| Quote: |
So I read all 40 pages thoroughly, and much of it does make sense. It appears to be a series of compounding issues that simply escalated an already borderline wing design.
My question is this... Does anyone know if the COMPLETE Bravo mods were tested for flutter, strength etc? The FAA reccomended that they (Zenith) run through further testing for structure and flutter.
Here's where I stand....
I own a 601XL-B that climbs like a rocket, and cruises 100-110kts happily, and the aircraft seems to perform great. HOWEVER, this IS my first Homebuilt, and I didn't buy it. I am highly mechanically enclined, so I know mechanics and the the basic engineering behind it all.
My searches turned up very little, both on the net, and on here. For example, my V-Speeds are as follows...
Vso- 44kts
Vs - 51kts
Va- 85kts
Vno- 113kts
VNE - 140kts
VX - 58kts
VY - 60kts
I've found many MANY different versions of the numbers, and that concerns me. After reading the FAA report, Va should be 80-82kts, Vno 103kts or lower. The VNE seemed to be the most consistent at 140kts (16mph)
The rudder upper bolts seem to wear and get play In them, there is flap stops, which I have never seen on a single zodiac yet, and haven't any idea what they look like. There are just so many variables.....
Is there anything that anyone can say to help ease my mind? What does the general concensus say about this airplane, both before and after the Bravo Mod? How sloppy do the cables need to get to become a hazard? My bottom line is that I am DEEPLY in love with flying the airplane, it's performance and slickness! It's a sexy looking airplane, and I get stopped for photo ops everywhere I go. It's amazing. The performance is unreal!
BUT, and a BIG BIG BUT here.....
How safe is this airplane? I have a G-Meter so I can monitor so that I'm not stressing the airframe. I don't jerk the controls, I'm smooth with them. I don't push the airplane or "hot dog" it. I just fly it like I would a 152. I can see how one would get in trouble quick though, because it IS so much fun to fly!
But at the end of the day, can I feel safe? Will it truthfully try to kill me? I've got three little ones that rely on me. Two 4 year old daughters and a 7 week old baby boy.
I see tons of videos from Europe with guys flying these 601's XL's and HD's with the same power plant as me, same set up, and they seem just fine. They have a blast it seems!
Chad..... Fighting to put my mind to rest......
Or sell this and buy a 152! Lol. At least I know they don't break-up in flight.
Thanks in advance!
Chad
--------
C-GYXQ. 912ULS. 601XL-B
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=401365#401365
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rpf(at)wi.rr.com
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| Posted: Sun May 26, 2013 3:40 am Post subject: FAA Special Review Team final report.... Have questions... |
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They did a ground vibration test (in Germany) on a pre-mod XL, with only
5lbs of cable tension and did not get any flutter.
--
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paulrod36(at)msn.com
Guest
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| Posted: Sun May 26, 2013 10:25 am Post subject: FAA Special Review Team final report.... Have questions... |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> I more or less agree with Paul M but there are also other other ways to de-epidermize the feline. Cables may be nice, but we can steal a page from the RV-whatever book, and put in push-pull aileron tubes. A very easy fix, which obviates any tension problems. If you ain't got no cables, you don't gotta worry about them. Also, after the mod was done on Zenith's demo XL, if memory serves, they reported that they got a test pilot to wring it out. He never publicly stated what he did, and they weren't about to, (probably to avoid encouraging those whose macho score exceeds their IQ), but the report was that the wings were "very robust". And, of course there's always the BRS, which, for under 5 grand, will allow you to rip apart your sweet little ride for the sake of a bar story....
Paul R
From: Paul Mulwitz (psm(at)att.net)
[quote] To: zenith601-list(at)matronics.com (zenith601-list(at)matronics.com)
Sent: Sunday, May 26, 2013 5:39 AM
Subject: Re: FAA Special Review Team final report.... Have questions...
--> Zenith601-List message posted by: Paul Mulwitz <psm(at)att.net (psm(at)att.net)>
Hi Chad,
I feel your pain. I will try to address all of the issues you raised,
but I'm sure I will forget some (rather than avoid them). Please feel
free to ask any questions again.
First, let me say I too have issues with my Zodiac XL with mods. The
good news is I had much greater ones and feel a lot better now than I
did when the upgrade was first announced. In general, I feel confident
in the structure now and believe it is possible to safely fly this
plane. There are limitations from my point of view, but the structural
issues seem to have been solved.
The biggest limitation for me is the light wing loading when combined
with unstable air. You get thrown around the sky compared to planes
with heavier wing loading. A C-150 would have similar problems but not
quite as bad. A C-182 will provide much more reliable and comfortable
transportation in most conditions, but you will pay for this comfort and
convenience.
I was not convinced the design was really fixed after reading the big
report from the FAA. I am not an aeronautical engineer and apparently I
didn't interpret the jargon correctly. I had a lucky meeting with the
guy whose name appears on the bottom of that report, Wes Ryan, at an
ASTM F37 meeting about a year after the report was issued. We discussed
the Zodiac issue for around 20 minutes. He convinced me that my
interpretation of the document was incorrect. They really did find
design problems with the Zodiac XL, and they really were fixed with the
upgrade package. History has supported this idea. There have not been
any more structural failures after installing the upgrade.
By the way, I have not changed the designation of my plane by adding the
"B" to its name. This is very difficult to do after the plane is
registered and I saw no reason to go through all that. Calling it
"Upgraded" is just as informative as adding the "B". It is different
for Zenith who sells kits long before they are registered.
There are a number of good reasons why you get different numbers from
different builders. All Zodiac XLs are not identical. Indeed, each one
is unique. There is no version control at Zenith, and changes are made
willy nilly whenever they feel like it. I doubt there is any reliable
way to track the changes that might appear in any given instance of the
XL. This is not really a problem, but it does mean you will get
differences from one plane to another. Of course it matters a great
deal what engine you mount after finishing building the kit. My point
is you shouldn't lose sleep over the different V speeds reported by
different builders. These planes are all built by amateurs and mostly
by people building their first plane. The rigging is less than optimum
on many of them. While there are problems with the design this is true
of all planes. The big problem - in flight structural failures - is
fixed now. The little problems are easy to live with if you operate the
plane in a conservative fashion and under weather conditions that are
reasonably benign.
I agree there is a problem in the rudder hinge area. I added bushings
to mine after seeing wear in the first few hours of flight. The
original design (at least the design as it appeared in my prints) had
steel rubbing against nylon each time the rudder was moved. This isn't
a good thing. Adding bushings so the steel is rubbing against a hard
and lubricated bushing seems to work a lot better.
I have nylon stops on the upward movement of the flaps. They are easy
to see from the top of the wing. Each flap has a couple of pieces of
nylon (1/8" sheet?) stuffed between the skin layers and riveted in
place. The nylon sticks out perhaps 1/4 inch from the top skin and the
flap presses against the stops. It is part of my normal preflight
inspection to try to wiggle the flaps. If they move at all I check to
make sure they are fully up. If they still move (they haven't yet in my
case) I would not fly the plane.
I do not know if the plane has been fully tested for flutter and other
bad juju since the mod was installed. This is a question for Zenith. I
am comfortable with the fact that history has shown the mod to be
effective. All the other possible tests only hope to predict the good
outcome we actually see now.
For what its worth I consider my XL to be as safe as you might expect
from any home built airplane. It has limitations, but they are not
particularly bad ones. I only fly in nice weather, and consider the XL
to be a fair weather plane. I would prefer to have a heavier and more
powerful plane but my lack of a medical certificate currently limits me
to light-sport designs. The XL is a reasonable example of the high end
of these planes. If the rules for medical certificates change in the
USA it is likely I will trade up to something bigger, heavier, and more
expensive to operate. Depending on the change I will probable go to the
upper limit of planes I can legally fly. For other people who treasure
inexpensive flying with reasonable cross country capability in good
weather I am comfortable recommending the XL as a possible choice.
Good luck,
Paul
Camas, WA
USA
On 5/25/2013 9:07 PM, SIDESLIP wrote:
| Quote: | --> Zenith601-List message posted by: "SIDESLIP" <Chad2007(at)rogers.com (Chad2007(at)rogers.com)>
So I read all 40 pages thoroughly, and much of it does make sense. It appears to be a series of compounding issues that simply escalated an already borderline wing design.
My question is this... Does anyone know if the COMPLETE Bravo mods were tested for flutter, strength etc? The FAA reccomended that they (Zenith) run through further testing for structure and flutter.
Here's where I stand....
I own a 601XL-B that climbs like a rocket, and cruises 100-110kts happily, and the aircraft seems to perform great. HOWEVER, this IS my first Homebuilt, and I didn't buy it. I am highly mechanically enclined, so I know mechanics and the the basic engineering behind it all.
My searches turned up very little, both on the net, and on here. For example, my V-Speeds are as follows...
Vso- 44kts
Vs - 51kts
Va- 85kts
Vno- 113kts
VNE - 140kts
VX - 58kts
VY - 60kts
I've found many MANY different versions of the numbers, and that concerns me. After reading the FAA report, Va should be 80-82kts, Vno 103kts or lower. The VNE seemed to be the most consistent at 140kts (16mph)
The rudder upper bolts seem to wear and get play In them, there is flap stops, which I have never seen on a single zodiac yet, and haven't any idea what they look like. There are just so many variables.....
Is there anything that anyone can say to help ease my mind? What does the general concensus say about this airplane, both before and after the Bravo Mod? How sloppy do the cables need to get to become a hazard? My bottom line is that I am DEEPLY in love with flying the airplane, it's performance and slickness! It's a sexy looking airplane, and I get stopped for photo ops everywhere I go. It's amazing. The performance is unreal!
BUT, and a BIG BIG BUT here.....
How safe is this airplane? I have a G-Meter so I can monitor so that I'm not stressing the airframe. I don't jerk the controls, I'm smooth with them. I don't push the airplane or "hot dog" it. I just fly it like I would a 152. I can see how one would get in trouble quick though, because it IS so much fun to fly!
But at the end of the day, can I feel safe? Will it truthfully try to kill me? I've got three little ones that rely on me. Two 4 year old daughters and a 7 week old baby boy.
I see tons of videos from Europe with guys flying these 601's XL's and HD's with the same power plant as me, same set up, and they seem just fine. They have a blast it seems!
Chad..... Fighting to put my mind to rest......
Or sell this and buy a 152! Lol. At least I know they don't break-up in flight.
Thanks in advance!
Chad
--------
C-GYXQ. 912ULS. 601XL-B
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=401365#401365
>nbsp; Features Chat, http://www.matnbsp; via the Web title=http://forums.matronics.com/ href="http://forums.matronics.com">http://forums.matronics.com
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Fderfler
Joined: 29 Jun 2013
Posts: 2
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| Posted: Sun Jun 30, 2013 7:36 am Post subject: Re: FAA Special Review Team final report.... Have questions |
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I just wanted to chime in and say that I completely agree with Paul who
said, "The biggest limitation for me is the light wing loading when combined
with unstable air."
These light sport aircraft weigh less than 800-900 pounds dry. The tail
of a white puffy cloud can give you an unexpected slap in the rudder that
makes you say, "Whoa"! This ain't no Cherokee.
Also, it is my personal opinion that the lower rudder bearing is another
problem waiting to sneak up on folks. Look for rudder play (up and down)
on every pre-flight. We put an Oilite impregnated bearing on my airplane
and there is NO up and down rudder movement. I'm coming up on 450
flying hours on my airplane and I've loved every hour. (Well, there was
that one time just north of Naples... but that's another story...)
Frank Derfler
Islamorada, FL
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