 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
macleod(at)eagle.ca
Guest
|
 Posted: Sat Apr 25, 2009 8:54 am Post subject: My plans for flying my XL |
 |
|
List:
I believe that I am one of many that read this list primarily to see the
comments and suggestions from a few of the list members (ie Larry, Bill,
John & a few others). These days there is a lot of speculation by members
on a possible problem with the XL and I can't sit here any longer reading
the posts without giving you my perspective on the issue.
Within a month I should be flying my XL. Am I concerned - NO! Why not?
First let me introduce myself. I am Mike MacLeod, a retired professional
Metallurgical Engineer. The XL is my third kit plane (and first Zenith).
I have finished building 601 XL kit 6-6771 and am waiting for final
inspection. The first part of my career was spent in the chemical
industry, and part of that was leading a group involved in failure
analysis of chemical plant components. We investigated hundreds of
failures. The failures were due to thing like general corrosion, stress
corrosion, fatigue, impact by equipment (ie trucks or tractors),
construction errors, misoperation by operators and a very very few "cause
unknown". Many of the failures in the first year of operation of any
chemical plant are design related. So, with this background, this is how I
read the current controversy.
1. My experience with equipment failures.
Chemical plants often have identical parallel trains and almost identical
(usually differing in size) serial trains. I consider all XLs to be
'parallel trains'. I realize that investigating chemical plant failures,
where the failed component is usually immediately obvious, is far easier
than examining an aircraft crash where the root failure is far from
obvious. When a failure occurred in a chemical plant we would go to the
scene (after the leak and/or fire was stopped) and do extensive non
destructive checking (Xray, ultrasound etc) of the failed component and
equipment close to it. We would then do similar checks on the
corresponding equipment in any serial or parallel trains. After this
on-site work we would have the failed component removed for lab analysis
(100% of the time after a catastrophic failure). Lab analysis can easily
identify the cause of a failure, especially where fatigue, cracking, or
stress related failures are present. I believe that given a failed sample
from an aircraft component a competent technician can easily detect the
cause of the failure.
A summary of our findings:
Failures due to Design Issues (in the first year of a plant' s operation
this could be 1/2 of all failures)
- if a failure was design related, similar degredations (which had not
yet progressed to failure) would
be found in about 50% of identical components on parallel
trains.
- we would also find similar degredations in about 10% of similar
components in serial trains.
Conclusion: Design related failures affect a large percentage of
identical/similar components.
Failures due to All Other Causes
- These failures type rarely resulted in similar degredations on similar
components in serial or parallel trains.
In the few cases where they did, the failure could usually be traced
to faulty procedures or poor construction work.
Conclusion: These failures only involved the component that failed.
2. ZBAG
I am not a member of ZBAG but I do owe them a debt of gratitude. Like
some others I looked at the hole I cut in the wing for the wing lockers
and wondered if these openings affected the strength of the wing. I also
wondered about the wing to fuselage connections, especially the rear spar
connection to that 'thin' 6-B5-4.
By their silence on these issues (and their engineer must have paid
particular attention to these) I am even more confident that:
- the wing attachments are robust
- the wing locker does not affect wing strength appreciably
- the lack of a rib at station 4 to make room for the larger fuel tank
does not affect wing strength
- the main landing gear attachments are robust (my second homebuilt was
destroyed by a landing gear failure)
- the rudder attachments are robust
We all look at things as we build and the above were the ones that made me
think (and take extra care).
My thoughts on the ZBAG group
This is a group of well meaning individuals who invested time and money to
find a fault with the design. Well, apparently the design is ok - but
their mission was to find a problem - so they found one - flutter - not
easily refutable - and, despite a lack of evidence, went with it. (To the
NTSB no less).
3. The 601XL
My reasons for purchasing the kit were as follows:
- above 100 kts cruise
- inexpensive
- will take my Rotax engine (from my previous homebuilt)
- BUT MOST IMPORTANTLY - IS SIMPLE AND COMES WITH ENGINEERING DRAWINGS (so
I can fabricate any part myself)
The fact that even though I bought a kit, this plane is simple enough for
me to build from scratch was paramount. My first plane was a 2 place
ultralight (about 1000 lbs gross). In many ways the ultralight was more
sophisticated than the XL, but don't ask me to fabricate those parts! I
believe that to achieve the level of simplicity present in the XL means
that some sacrifices in performance must be made.
I have seen videos of XLs where the pilots don't seem to realize that a
plane as simple as the XL can't be flown like a fighter.
I have read reports of XLs diving, looping, flying in strong winds and
other (in my opinion) very, very risky acts.
In Canada the XL can be registered as an ultralight. I will treat it as one.
4 My thoughts on Flutter
Flutter is a speed issue, go faster and increase the likelihood of being
caught.
I don't know how many XLs are flying, but based on the number of pictures
of XLs on the Zenith website I suspect that there are hundreds. In my
experience with design problems if flutter was an issue with the design
there should be many, many reports of flutter (up to 50% of aircraft).
But there aren't. I only know of one and I truly question if it was
really flutter (I once flew my Pelican at 1500 ft AGL over the stacks of
Algoma Steel in Sault St Marie Ont. as a shortcut to the airport "lets fly
direct, we will get to see more"; the plane shook rapidly and extremely,
extremely violently in the turbulence, I am lucky to still be married).
But this wasn't flutter.
Another problem I have with the flutter scenario is that some of the XL
incidents seem to involve aircraft that were apparently flying much slower
than Vne (or even Vc). One may have had its flaps down. Yet these
aircraft suffered an accident. They were probably flying much faster in
the period before the incident (even minutes before). This is not how
flutter works.
How can this be? No reports of a problem, even by pilots who far exceeded
VNE in phase 1 testing, yet people frantic for a solution.
5.My thoughts on aileron and elevator balancing
My Pelican PL (VNE 141 kts) had both aileron and elevator balancing. But
its successor the almost identical Pelican Sport had neither. When I
questioned the designer on this he assured me that on these planes as long
as the speeds were less than about 200 kts there was no chance of flutter.
Flutter is a phenomena that can be computer modeled. If these models
tell us that flutter is not an issue, I believe them.
In addition, trying to scare us by suggesting that our XLs will behave
similarly to the posted videos of flutter on non XL wings is
irresponsible. We all know that given the right conditions (well above
Vne) flutter can occur.
6. Witness reliability.
I live in the country. Occasionally we have flight schools practicing in
the skies above. I often go out to watch the stall practice (not much to
see - just a plane that seems to go very quiet, slow down, maybe a slight
change in heading, then noisier than before). Sometimes though they are
practicing spins, same as before - plane goes quiet, slows down - then
WOW, are those wings broken? . The illusion that as the plane spins one
or both wings are no longer at 90 degrees to the fuselage is very
powerful.
MY CONCLUSIONS:
- There is not a design problem that causes flutter.
- There is probably no single cause of the accidents. (unless you count
pilot error)
- Aileron balancing is not required.
- Eyewitness reports can be misleading.
MY PLANS
- First, before taking FSVB up - practice, practice, practice landings in
another low wing plane until I can grease it in every time.
I think the stresses on the wings from hard landings far exceed
anything you can do in flight.
- Avoid off airport landings (and try to avoid grass strips)
I know that many XLs use grass strips but in my experience they can be
very rough and again put stress on the wing attachments.
- Keep the cables tightened to 'spec'.
- Never fly faster than 130 kts.
- Fly only in good weather (I have always done this, I hate "bumps")
- Treat the plane with kid gloves (no spins, dives, turns over 60 degrees
bank, etc)
- Watch that rearward C of G
With the light Rotax engine my plane's C of G can easily go behind 450mm
as the fuel is burned.
- Never, never make abrupt fore or aft movements with the stick
I have the dual stick option, I think this will give me more leverage
with less feedback when I move the elevator.
- I will not 'balance' my ailerons or elevator.
My Thoughts.
Any Comments? (especially on MY PLANS)
Mike
macleod(at)eagle.ca
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
 |
d.goddard(at)ns.sympatico
Guest
|
| Posted: Sat Apr 25, 2009 2:05 pm Post subject: My plans for flying my XL |
|
|
Since you asked. People have died in unexplained circumstances with the
601XL. So I think you should be concerned. Not frightened, not grounded,
simply aware and concerned, it may in fact turn out that a modification is
required. With all due respect for your history and such, expertise in one
field does not confer expertise in another, so it has little bearing. Fly
carefully and I believe you'll be ok. But that believe has no basis in fact,
it is simply my feeling about the aircraft. Good luck and safe flying.
---
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
jmaynard
Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)
|
| Posted: Sat Apr 25, 2009 6:02 pm Post subject: My plans for flying my XL |
|
|
On Sat, Apr 25, 2009 at 12:53:20PM -0400, macleod(at)eagle.ca wrote:
| Quote: | Within a month I should be flying my XL.
|
Happy to hear it!
| Quote: | My thoughts on the ZBAG group
This is a group of well meaning individuals who invested time and money to
find a fault with the design. Well, apparently the design is ok - but
their mission was to find a problem - so they found one - flutter - not
easily refutable - and, despite a lack of evidence, went with it. (To the
NTSB no less).
|
Sorry, but no. I, at least, would have been perfectly happy had there been
nothing at all found. I'm happy Zenair chose to run the exhaustive analysis
of the Zodiac structure, both static and dynamic, they hadn't run before. I
look forward with interest to reading the reports they've promised to
publish.
| Quote: | Flutter is a phenomena that can be computer modeled. If these models
tell us that flutter is not an issue, I believe them.
|
However, those models are only approximations unless and until they're
validated with ground vibration testing. Zenair has now done that; until
then, it's just a guess.
| Quote: | In addition, trying to scare us by suggesting that our XLs will behave
similarly to the posted videos of flutter on non XL wings is
irresponsible. We all know that given the right conditions (well above
Vne) flutter can occur.
|
That assumes that the design was analyzed and tested for flutter above Vne -
something that may or may not have been done before now in the case of the
Zodiac.
| Quote: | MY CONCLUSIONS:
- There is not a design problem that causes flutter.
|
Zenair's testing this week seems to agree with you. If so, it's the first
time anyone can say so definitively.
| Quote: | - There is probably no single cause of the accidents. (unless you count
pilot error)
|
Sorry, but I can't accept this either. For example, where did Mathieu Heintz
get the Yuba City accident having a -8G load?! The NTSB report didn't say
anything like that. Not all pilots have been doing aerobatics in their
Zodiacs.
| Quote: | - Aileron balancing is not required.
|
If there's no flutter, then you're correct. However, *every* aeronautical
engineer I've discussed the Zodiac with, and *every* bit of written guidance
from the FAA, says that the only way to *guarantee* no flutter is to use
mass balanced controls. Given that, it's not unreasonable to assume that
mass balancing is required.
| Quote: | - Eyewitness reports can be misleading.
|
No arguments here.
| Quote: | MY PLANS
- First, before taking FSVB up - practice, practice, practice landings in
another low wing plane until I can grease it in every time.
I think the stresses on the wings from hard landings far exceed
anything you can do in flight.
|
I'd *strongly* recommend getting some time in a Zodiac. The pitch
sensitivity is such that you *will* need some transition time. Landing a
Zodiac is not like landing a Cherokee or a Mooney or a Musketeer. The
principles are the same, sure, but your first few landings in a Zodiac
*will* suck.
| Quote: | - Avoid off airport landings (and try to avoid grass strips)
I know that many XLs use grass strips but in my experience they can be
very rough and again put stress on the wing attachments.
|
I've flown in ad out of grass strips with mine. No issues. (In fact, my
favorite picture of my airplane was taken at a fly-in at a grass strip in
the middle of nowhere on Michigan's upper peninsula.)
| Quote: | - Keep the cables tightened to 'spec'.
- Never fly faster than 130 kts.
|
Both very good ideas.
| Quote: | - Fly only in good weather (I have always done this, I hate "bumps")
|
That's a good idea in theory, but in practice, you'll get them anyway...just
remember to slow to maneuvering speed if the bumps get too bad.
| Quote: | - Treat the plane with kid gloves (no spins, dives, turns over 60 degrees
bank, etc)
|
This is just prudent piloting. The Zodiac is not an aerobatic airplane.
Don't fly it like one.
| Quote: | - Watch that rearward C of G
With the light Rotax engine my plane's C of G can easily go behind 450mm
as the fuel is burned.
|
Good advice, always. I have jsut the opposite problem with the O-200: it
takes some weight in the seats with full fuel to keep the CG in limits
forward.
| Quote: | - Never, never make abrupt fore or aft movements with the stick
I have the dual stick option, I think this will give me more leverage
with less feedback when I move the elevator.
|
Don't think of it as moving the stick. Think of it as pushing on the stick
until the airplane does what you want. The Zodiac will teach you the meaning
of 'control pressure".
| Quote: | - I will not 'balance' my ailerons or elevator.
|
Your choice, but I suspect that, should Zenair develop and release a mass
balance kit, the market will force you to install it if you ever want to
sell your airplane.
That said...why wouldn't you? What bad effects would you expect such a kit
to have?
--
Jay Maynard, K5ZC, PP-ASEL, AGI http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (KFRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC |
|
| Back to top |
|
|
rpf(at)wi.rr.com
Guest
|
| Posted: Sun Apr 26, 2009 5:48 am Post subject: My plans for flying my XL |
|
|
Jay, you say this with a matter of fact "but your first few landings in a
Zodiac
*will* suck." Maybe yours did, but mine didn't, and I'm sure some others on
this list didn't either. It is sensitive in pitch; but you get the feel
for that before you enter the pattern for your first landing.
Randy
---
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
jmaynard
Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)
|
| Posted: Sun Apr 26, 2009 6:04 am Post subject: My plans for flying my XL |
|
|
On Sun, Apr 26, 2009 at 08:47:05AM -0500, Randy wrote:
| Quote: | Jay, you say this with a matter of fact "but your first few landings in a
Zodiac *will* suck." Maybe yours did, but mine didn't, and I'm sure some
others on this list didn't either. It is sensitive in pitch; but you get
the feel for that before you enter the pattern for your first landing.
|
Oh, I'm sure there are folks out there who got it right the first time.
Still, isn't it better to treat it carefully, and if your first few
landings don't suck, take it as a pleasant surprise?
It's still far, far better to get some transition training than to have to
learn the hard way on the first flight of your shiny new aircraft.
--
Jay Maynard, K5ZC, PP-ASEL, AGI http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (KFRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC |
|
| Back to top |
|
|
Juan Vega Jr
Joined: 13 Jan 2009
Posts: 157
|
| Posted: Sun Apr 26, 2009 6:47 am Post subject: My plans for flying my XL |
|
|
Speak for your self Jay!. DUde. the 601 once you get the hang of the stick motion up in the air, the landings are Asymptotic! Cushy is the word!
Juan
--
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
|
|
| Back to top |
|
|
jmaynard
Joined: 27 Feb 2008
Posts: 394
Location: Fairmont, MN (FRM)
|
| Posted: Sun Apr 26, 2009 7:25 am Post subject: My plans for flying my XL |
|
|
On Sun, Apr 26, 2009 at 10:45:44AM -0400, Juan Vega wrote:
| Quote: | Speak for your self Jay!. DUde. the 601 once you get the hang of the
stick motion up in the air, the landings are Asymptotic! Cushy is the
word!
|
*Once you get the hang of it*, I agree. The transition is the hard part.
--
Jay Maynard, K5ZC, PP-ASEL, AGI http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (KFRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC http://www.tronguy.net/N55ZC.shtml
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
|
_________________
Jay Maynard, K5ZC
AMD Zodiac XLi N55ZC |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
