Today's Message Index:
----------------------
1. 03:12 PM - Re: Re: 601 problems (Bryan Martin)
2. 04:56 PM - Re: Re: 601 problems (David Downey)
3. 06:31 PM - NTSB report (Walter Carey)
4. 07:01 PM - Re: NTSB report (Paul Mulwitz)
5. 09:13 PM - Re: 601 problems (Sabrina)
Message 1
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| Subject: | Re: 601 problems |
It's not any kind of concern for the 601XL. The amount of sweep is not
significant. All of the FSW aircraft you have mentioned have
significant forward sweep, on the order of 15 degrees or more, and
that sweep comes from sweeping the spar forward at an angle to the
fuselage.
On Dec 26, 2008, at 7:34 PM, David Downey wrote:
> the FSW is not an aerodynamic concern - it is a structural concern.
> ALL FSW built/designed from isotropic materials suffer from
> structural divergence with bending due to increased AOA at the tip
> under those conditions. It is not a coincidence that the first
> "successful" FSW occurred in teh 90 with the advent of tailored
> structure courtesy of advanced composite materials - very highly
> anisotropic in nature. Only with those materials is it possible to
> desing any degree of FSW without a massive weight hit.
>
> The short lived Hansa bizjet is the only fsw comercial design
> extant. The germans tried during WWII but found that when the
> structure was befed enough to withstand the divergence issue, it was
> too heavy to offer any benefit.
>
> David L. Downey
> Harleysville (SE) PA, USA
>
>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
Message 2
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| Subject: | Re: 601 problems |
Bryan;
I hear you loud and clear - I am not suggesting that it is a major issue. W
hat I am suggesting is that there is a contributing destabilizing design fe
ature that may come into play only under abuse or repeated abuse.
The reason for angling the spar forward more than the 25% chord line of the
wing planform is to attempt to control the structural and aerodynamic dver
gence that is the issue with FSW. When aerodynamic loads start to bend the
wing, the twisting forces due to the placement of the spars tends to reduce
the instantaneous AOA whereas in the case of a spar located on a constant
percentage of chord or actually shifting to a greater percent of shord as s
pan increases (the actual situation with the 601XL) and aerodynamic loading
prior to stall simply bends the wing to a greater AOA - and greater loadin
g.
I will not post to this again. I meant no assault - to anyone. Having spent
my entire life in the design and testing of airframes and materials, and w
ith that the associated loss of a couple of good friends in flight test acc
idents,- it bothers me to see a detail glossed over that may be a (perhap
s tiny) piece of the puzzle that is the service history of the XL.
David L. Downey Harleysville-(SE) PA, USA
--- On Sun, 12/28/08, Bryan Martin <bryanmmartin@comcast.net> wrote:
From: Bryan Martin <bryanmmartin@comcast.net>
Subject: Re: Zenith601-List: Re: 601 problems
<bryanmmartin@comcast.net>
It's not any kind of concern for the 601XL. The amount of sweep is not
significant. All of the FSW aircraft you have mentioned have significant fo
rward
sweep, on the order of 15 degrees or more, and that sweep comes from sweepi
ng
the spar forward at an angle to the fuselage.
On Dec 26, 2008, at 7:34 PM, David Downey wrote:
> the FSW is not an aerodynamic concern - it is a structural concern. ALL
FSW built/designed from isotropic materials suffer from structural divergen
ce
with bending due to increased AOA at the tip under those conditions. It is
not
a coincidence that the first "successful" FSW occurred in teh 90 with
the advent of tailored structure courtesy of advanced composite materials -
very
highly anisotropic in nature. Only with those materials is it possible to d
esing
any degree of FSW without a massive weight hit.
>
> The short lived Hansa bizjet is the only fsw comercial design extant. The
germans tried during WWII but found that when the structure was befed enoug
h to
withstand the divergence issue, it was too heavy to offer any benefit.
>
> David L. Downey
> Harleysville (SE) PA, USA
>
>
--Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
=0A=0A=0A
Message 3
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Hi Everyone,
-
- Walt Carey here. Currently building a 601XL w/Jabiru 3300A in Beavercre
ek, Ohio, on the outskirts of Dayton. Wings, control surfaces and vertical/
horizontal stabilizer complete. Fuselage 25%complete. And I'm going to fini
sh it and fly it God willing.
-
- I've been following the discussions regarding the "suspect" wing failur
es on the 601XL, and possible causes.-And I'm also-am aware of the advi
sory that was published regarding improper control cable tension being the
possible culprit. I personally think that's a good possibility and-recomm
end that all Zennith builders get the word out to their fellow builders ASA
P. No harm whatsoever in having the correct control cable tensions. Someone
recently mentioned that the "suspect" wing failures are pecular to the 601
XL and 601 variants. Take a look at the following "preliminary" NTSB accide
nt report on an Ercoupe:
-
NTSB Identification: ERA09FA087
14 CFR Part 91: General Aviation
Accident occurred Saturday, December 13, 2008 in Sebring, FL
Aircraft: ERCOUPE 415-D, registration: N99154
Injuries: 2 Fatal.
This is preliminary information, subject to change, and may contain errors.
Any errors in this report will be corrected when the final report has been
completed.
On December 13, 2008 at 1206 eastern standard time, an Ercoupe 415-D, N9915
4, was destroyed during an in-flight breakup near Sebring, Florida. The cer
tificated commercial pilot and the passenger were fatally injured. Visual m
eteorological conditions prevailed, and no flight plan was filed for the lo
cal flight, which departed Avon Park Executive Airport (AVO), Avon Park, Fl
orida about 1115. The personal flight was conducted under the provisions of
14 Code of Federal Regulations Part 91.
According to a friend of the accident pilot, who was also a certificated ai
rcraft mechanic, he and the pilot flew together in the accident airplane im
mediately prior to the accident flight. The friend did not note any abnorma
lities with the performance of either the airplane or the pilot during thei
r flight, and upon returning to AVO, the friend disembarked the airplane an
d the accident passenger boarded.
Numerous witnesses observed the airplane flying in the local area around th
e time of the accident. One witness was outside talking with a neighbor whe
n he observed the airplane flying overhead. The airplane was initially flyi
ng southwest, and made a "very slight dip and turned to the right. Then the
airplane pulled up severely and started turning to the left." As the airpl
ane continued upward and banked to the left, something "shiny" exited from
the tail area of the airplane. The witness remarked to his neighbor, "What
the heck is he dumping," and the airplane then began to break apart. The wi
tness added that he did not hear any type of explosion and did not observe
any smoke or fire.
Another witness, who was also a certificated airline transport pilot, state
d that while outside working on his house he observed the accident airplane
flying overhead. He estimated that the airplane was flying at an altitude
about 1,200 feet above ground level, and did not note anything abnormal abo
ut its flight path. About 45 minutes after first seeing the airplane, he he
ard an abnormal engine sound that diverted his attention again back to it.
The witness stated that the engine sound was smooth, continuous, and sounde
d as if the engine was being "over-sped," as if the engine were at full pow
er and the airplane was in a high speed dive. When he looked up, he saw the
airplane pitching up and rolling into a steep left bank, and initially tho
ught that the pilot was attempting to perform a "barrel-roll or a slow roll
." From his position, he could see the bottom of the airplane, as well as b
oth wings, as the airplane traveled north. He additionally noted that while
the airplane was banking, both ailerons were "fluttering" at a high freque
ncy. The bank angle increased to almost 90 degrees, when the left wing of t
he airplane "folded back" and separated from the fuselage. The airplane the
n pivoted about the lateral axis 90 degrees, and the right wing then separa
ted from the fuselage along with a portion of the cabin. The wings "flutter
ed=94 or "twirled" to the ground, while the portion of the cabin
continued forward and down to the ground. He recalled hearing three distin
ct "thuds" as the pieces of the airplane impacted the ground.
The witness also reported that during the breakup, the airplane released wh
at initially looked like "confetti," which he later determined to be painte
d chips of dope from the airplane=92s fabric covered wings.
The weather conditions reported at Bartow Municipal Airport (BOW), Bartow,
Florida, located about 24 nautical miles west of the accident site, at 1152
, included winds from 020 degrees at 9 knots, gusting to 15 knots, 20 statu
te miles visibility, clear skies, a temperature of 16 degrees Celsius (C),
a dewpoint of 6 degrees C, and an altimeter setting of 30.21 inches of merc
ury.
The pilot held a commercial pilot certificate with ratings for airplane sin
gle engine land and sea, airplane multiengine land, and instrument airplane
. He also held a flight instructor certificate with ratings for airplane si
ngle engine, airplane multiengine, and instrument airplane. His most recent
FAA second class medical certificate was issued on June 2, 2008.
Examination of the pilot=92s most recent logbook, which began on May 3, 200
1, revealed that he had logged 7,126 total hours of flight experience, 12 h
ours of which were in the accident airplane make and model.
According to records provided by the FAA, the accident airplane was manufac
tured in 1946. According to maintenance records, the airplane=92s most rece
nt annual inspection was completed on May 9, 2008. At the time of the inspe
ction, the airplane had accumulated 2,588 total hours of operation.
The in-flight breakup occurred over a residential community built around a
golf course. Portions of wreckage were found along a wreckage path that was
3,100 feet long, and oriented on a magnetic heading about 020 degrees. The
first pieces of wreckage, found at the most southern end of the wreckage p
ath, included both aft cabin windows. Paint chips, inspection panels, and v
arious personal effects from inside the airplane were located further along
the wreckage path, with the right wing being the next most substantial com
ponent located.
The right wing was located about 2,000 feet from the aft cabin windows, alo
ng the wreckage path. The wing was lodged in the ground, oriented perpendic
ular to the terrain. The wing remained largely intact, and was separated fr
om the fuselage at the wing root, just inboard of the leading edge fuel tan
k. The wing spar remained intact to a point about 1-foot inboard of the win
g root, where it separated from the remainder of the airplane's structure.
Ten of the right wing's 17 inspection port covers were dislodged, and locat
ed at various points along the wreckage path in an inverted or "popped" pos
ition. All of the displaced covers had, with one exception, come from the w
ing root, leading edge, and outboard edge, while the inspection covers from
the center and trailing edge portions remained in place.
The left wing was located about 900 feet beyond the left wing, along the wr
eckage path. The left wing spar was fractured at a similar location as the
right wing spar. Several of the inspection port covers were dislodged, but
did not display any discernable pattern as was observed on the right wing.
The inboard portions of both wing spars were forwarded to the National Tran
sportation Safety Board Materials Laboratory for further examination.
The main portion of wreckage came to rest about 200 feet beyond the left wi
ng, along the wreckage path. The nose, cabin, and aft portion of fuselage e
xhibited extensive crush damage, and its entirety was contained with an are
a about 10 by 10 feet. The cabin was severely compromised, and the seat pan
, where both occupants were located, was found about 125 feet north of the
main wreckage. The empennage, horizontal and vertical stabilizers remained
largely intact, but separated from the remainder of the fuselage, and was c
o-located with the main wreckage. The propeller was lodged in a shallow imp
act crater, and remained attached to the engine at the propeller flange. Ch
ordwise scratching and burnishing was present on both blades.
Aileron and rudder control continuity was traced from the flight control su
rfaces to the control "mixing" bellcrank, normally located just aft of the
main spar carrythrough. Separations of the aileron control push-pull tubes
were noted at both wing roots, and the elevator push-pull tube was separate
d about 1-foot forward its bellcrank.
Index for Dec2008 | Index of months
-------
-Thoughts?----
Message 4
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At 06:29 PM 12/28/2008, you wrote:
>
> Thoughts?
>
>
I have one thought about the Ercoupe and Zodiac in-flight
failures. It stems from the comments by observers that the engine
changed pitch just before the breakup.
I remember a report about a Zodiac that made vibration sounds (over a
power plant?) and the pilot managed to get it to stop with radical
roll maneuvering. I wonder if other pilots experiencing unusual
vibration sounds might first suspect something wrong with the
engine. If so, they might try changing throttle or other engine
settings to make the noise go away.
I have absolutely no confidence that my notion is correct. All I
hope to accomplish with writing this comment is to alert Zodiac XL
drivers to the possibility of airframe vibrations and to consider
something like the deep roll rather than changing engine settings to
deal with such noise. It may help, or it may not.
Paul
XL getting close
Message 5
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| Subject: | Re: 601 problems |
"The forward sweep is an artifact of the 3 degree forward tilt of the spar and
the wing dihedral. If you raise the nose until the spar is vertical you will see
no forward sweep." Bryan
I will not post to this again. I meant no assault - to anyone. David
David, you should keep at it. The forward sweep of the wing in cruise attitude
changes the way the air flows over the ailerons. In otherwords, spanwise airflow
over a forward-swept wing is the reverse of a conventional swept wing. The
fact that the sweep is so slight and can change with flight attitude may be
an important factor for the LAA and NTSB to consider in determining how and when
the ailerons that did unzip, unzipped since the airflow across them reverses
while leveling off after a climb. Correct?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221565#221565
Attachments:
http://forums.matronics.com//files/forward_swept_wing_aerodynamics_920.jpg
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