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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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 Posted: Fri Mar 13, 2009 10:13 am Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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At 09:51 AM 3/7/2009 +0100, François Chapperon wrote:
| Quote: |
So you must know that last week , ZENAIR FRANCE (Michael Heintz) sent a 601XL to a private laboratory in HAMBOURG (Germany) to have dynamic examination in an artificial speed room ( blowers)
They also asked ZENAIR to have a dynamic gtest by loading wings , both sides, (intrados and extrados) with a charge of sand sacks .
Yours,
François Chapperon |
As François points out, Zenair Europe have committed to conducting a series of load tests and ground vibration tests so that the German government will lift the flight restrictions on German 601XL's.
Zenair's planned tests may be good news for all 601XL/650 owners whose planes are registered as European ultralights at 450 kg (472.5 kg [1041 lb] with BRS). The news is not so good for builders in the States and elsewhere where the 601XL/650 is spec'd for 1320 lbs (600kg) (at) +/- 6G, because Zenair plans to test the 601XL wing to only the European ultralight spec for the DAeC.
When I became aware of the upcoming German tests, I posted a message on the ZBAG forum listing test requirements that I believed were important based on what ZBAG's analyses have uncovered over the past 8 months. I then exchanged several emails with Mat Heintz on the subject. The final outcome followed Mat's initial reaction to my post: Zenair would only test to US LSA standards "If we still have money left over after the completion of the German tests." I think that means "No. We will not test to US specs." While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the 601XL to flutter. Accordingly, ZBAG believes that we had to do something to encourage Zenair to test the 601XL to US specs. Since Zenair is apparently short on funds, ZBAG offered them $2500 so that they could afford to test to US specs. The email with our offer is appended below. If you would like to read my complete email exchange with Mat, let me know off line and I'll send you a copy. If you'd like a primer on how to handle load test results, see, e.g., http://www.vansaircraft.com/public/rv-10int2.htm .
Why should you care? Well, one reason is that your various operational limitation speeds, Vne, Va, Vc, etc., are a function of the wing strength. If the wing is only good to +5G (say) rather than +6G, then Vne might well be reduced from 160 mph to perhaps 150 or 140 mph and the gross weight would also be reduced. The calculations are beyond me, but the correlation between gross weight, load factors and Vne is clear. Reduce the wing load rating and you must reduce the design airspeeds and gross weight.
Another reason is that ZBAG is convinced that flutter is a factor in many, if not most, of the wing loss accidents. However, if Zenair tests a new airframe with lots of friction and cables tensioned to specs, the system stiffness could mask the tendency of the wings to flutter. That test would be unrepresentative of the 601XL fleet that includes aircraft with many flight hours and various levels of maintenance. Accordingly, we have asked Zenair to test at several cable tensions. The extra cost to test the fully instrumented airplane at three additional cable tensions would be very little. My message to Zenair is appended below below.
If Zenair accepts our offer that be would terrific. The tests would be done to LSA standards and Zenair wouldn't have to foot the whole bill. However, since they have not even acknowledged our message in three days, it looks like they may not accept the offer.
Every builder/owner of an 601XL/650 with a gross greater than 1041 lb has a stake in this. The load tests that Zenair are planning are irrelevant to your airplane! The GVT tests may be irrelevant to all 601XL/650's, unless Zenair takes data at cable tensions lower than specified 30 lb.
This is important. If you would like to see Zenair test the 601XL to US Specs, you might let them know. Tell the three Heintz brothers (listed below) that you want them to accept ZBAG's offer to help test the 601XL/650 airframe to US Specs. If they get the message from enough of their customers they might change their plans. Maybe. Time is short. If you care about the 601XL/650 tests, let Zenair know today.
Thanks for listening.
Terry
P.S.
Why is it so important to do the tests to US specs now? Well, if you do the tests in the sequence that Mat seems to favor: - Test to DAeC limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing yields after the the DAeC ultimate test, that may argue against using the same airframe for the ASTM tests. I'm awaiting an expert opinion on this point. But you probably need two airframes, two test setup expenses, etc.
But, if you use the following sequence: - Test to DAeC limit load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing doesn't yield in the ASTM limit load test, but does yield after the the DAeC ultimate test (a plausible outcome), one could probably use the same airframe for the ASTM ultimate test. I'm awaiting an expert opinion on this one also. But I think it is very likely that you could get away with one airframe and one test set up.
The lesson is that, by cleverly combining the DAeC test with the ASTM US specs test, you double the data for a 10 or 20% increase in test cost. If you do them separately, you probably double the costs. If you want the data you take the clever route.
| Quote: | | Quote: | Date: Mon, 09 Mar 2009 23:10:02 -0600
To: micheintz(at)gmail.com,"S. Heintz / Zenith Aircraft Co." <seb.heintz(at)zenithair.com>, "heintz_mat" <heintz_mat(at)yahoo.com>
From: Terry Phillips <ttp44(at)rkymtn.net>
Subject: ZBAG Offer to Help Zenair Pay for Ground Vibration and Load Tests
Michael, Sebastien, and Mathieu
In response to five accidents involving in-flight breakup of Zenith 601XL's the Zenith Builders Analysis Group (ZBAG) was formed in 2008 to conduct independent engineering analyses of the Zenith 601XL airplane. Since ZBAG began in May 2008, in-flight breakup is suspected in at least three additional 601XL accidents. While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the airplane to flutter. Zenair recently announced a series of tests on the 601XL in response to German Government restrictions on 601XL operations. Mat Heintz has publicly stated that Zenair will only test to US LSA standards "If we still have money left over after the completion of the German tests."
Since Zenair funding is apparently critical at this time, ZBAG is stepping forward to help out.
This message is a formal offer from ZBAG to Zenair to contribute $2500 to Zenair to extend the German test series from the German requirements of 992 lbs gross to Zenair's US specifications of 1320 lbs (at) 6G. Since ZBAG funding will give the test results an implied approval by ZBAG the test plan must meet the following conditions: - The ground vibration test series should include measurements of the control system vibration frequencies at 3 or more of cable tensions below the specified tension of 30 lb +/- 5 lb. The range considered should include 20 lb, 10 lb and a tension of near zero (i.e. slack cables) that is still sufficient to produce an oscillatory response.
- We are concerned that the test plan may include only a single test at 30 lbs tension in a high friction, brand new airframe. This will make the GVT results irrelevant for real world 601XL's in the fleet.
- We have a documented instance of significant loosening of 601XL cables during a short cross country flight.
- The UK LAA has raised an issue regarding handling of fuel in the load calculations. Following the LAA's lead, the assumed fuel load should be the case of MTOW with minimum fuel.
- The load test program must include loading to limit load factor (4g), unloading and inspection of the wing for yielding and then a final loading to ultimate load.
- The airframe must be correctly supported for the tests by the engine mount, seats and tailplane. According to the LAA, in some earlier tests on the 601XL, the airframe was supported directly by the center spar which is an unrealistic condition that would bias the test results. The support of the airframe for future testing should provide for realistic loading of the center section and the uprights that shear the loads into the fuselage sides.
- Two positive load cases should be done.
- PHAA (Positive High Angle of Attack). This condition is representative of the VA / n1 condition. In this condition the wing center of pressure is forward (i.e. the leading edge of the wing is highly loaded) and the maximum forward chordwise components of drag load are applied to the wing. The wing is simultaneously loaded with maximum bending and shear loads. The airplane should be positioned in a high angle of attack attitude (i.e. upside down with nose down).
- PLAA (Positive Low Angle of Attack). This condition is representative of the VD / n1 condition. In this case the center of pressure is aft and thus the wing is critical for symmetric torsion together with maximum shear and bending. The airplane is positioned in a low angle of attack attitude.
- There must be an independent review of the test plans. xxxxxxxxxxxxx***, a xxxxxxxxxx professional aeronautical engineer - the xxxxxxxxx equivalent to a US FAA DER, is working with ZBAG. You have seen his reports and should be familiar with the quality of his work. xxxxxxxxxx is extremely busy just now, but he would make time to perform the review. The test plans would be released to xxxxxxxxx under a confidentiality agreement.
- Zenair must share the test results with xxxxxxxxxxx under the confidentiality agreement. xxxxxxxxxx could use the results of the ground vibration analysis to validate his flutter analysis models, but could not publish the test report.
ZBAG's sole intention in granting this funding to Zenair is to produce information that we believe is crucial to saving the lives of 601XL pilots and passengers who are flying their 601XL's at a gross weight of 1320 lbs. We sincerely hope that Zenair will accept our offer of financial assistance to extend the current test series. If our $2500 is insufficient to cover the cost of these tests, ZBAG will commit to an broad based fund raising effort using all possible resources to communicate with as many 601XL/650 builders and owners as possible to raise whatever additional funds are needed. I will personally commit to a contribution of $100.
I look forward to your response.
Sincerely,
Terry Phillips |
|
***The engineer asked that his name be removed from posts to the net.
Terry Phillips ZBAGer
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons are done; working on the wings
http://www.mykitlog.com/N47TP/ [quote][b]
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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Gig Giacona
Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA
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| Posted: Fri Mar 13, 2009 11:25 am Post subject: Re: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airp |
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| Terry Phillips wrote: |
Another reason is that ZBAG is convinced that flutter is a factor in many, if not most, of the wing loss accidents. |
Terry now that you've made this statement in a public forum (someplace other than ZBAG) I have to ask what ZBAG is basing this on? Was there some data in test ZBAG had done that shows this. I realize that you guys own the data you paid for and that you have shared or offered to share it with Zenith. But if you are going to make statements like the one above you need to back it up as publicly as you make it.
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W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR |
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hills(at)sunflower.com
Guest
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| Posted: Fri Mar 13, 2009 4:00 pm Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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As long as I’m sending emails…
This statement (below) does not apply to the zenith line directly, I have been told by the factory that the Vne of their planes is not a structural failure speed, it is the speed to which the factory has already tested the plane in flight and knows it to be safe to operate it to that speed limit. They also told me they don’t know the actual structural Vne of failure, they do those test or perform those calculations.
They also told me that the 601 HDS is stressed to 9 Gs, but they only state it to be 6 Gs because they don’t want folks using it for aerobatics ( for liability reasons).
Roger
Why should you care? Well, one reason is that your various operational limitation speeds, Vne, Va, Vc, etc., are a function of the wing strength. If the wing is only good to +5G (say) rather than +6G, then Vne might well be reduced from 160 mph to perhaps 150 or 140 mph and the gross weight would also be reduced. The calculations are beyond me, but the correlation between gross weight, load factors and Vne is clear. Reduce the wing load rating and you must reduce the design airspeeds and gross weight.
From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Terry Phillips
Sent: Friday, March 13, 2009 1:08 PM
To: zenith-list(at)matronics.com
Subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane?
At 09:51 AM 3/7/2009 +0100, François Chapperon wrote:
So you must know that last week , ZENAIR FRANCE (Michael Heintz) sent a 601XL to a private laboratory in HAMBOURG (Germany) to have dynamic examination in an artificial speed room ( blowers)
They also asked ZENAIR to have a dynamic gtest by loading wings , both sides, (intrados and extrados) with a charge of sand sacks .
Yours,
François Chapperon
As François points out, Zenair Europe have committed to conducting a series of load tests and ground vibration tests so that the German government will lift the flight restrictions on German 601XL's.
Zenair's planned tests may be good news for all 601XL/650 owners whose planes are registered as European ultralights at 450 kg (472.5 kg [1041 lb] with BRS). The news is not so good for builders in the States and elsewhere where the 601XL/650 is spec'd for 1320 lbs (600kg) (at) +/- 6G, because Zenair plans to test the 601XL wing to only the European ultralight spec for the DAeC.
When I became aware of the upcoming German tests, I posted a message on the ZBAG forum listing test requirements that I believed were important based on what ZBAG's analyses have uncovered over the past 8 months. I then exchanged several emails with Mat Heintz on the subject. The final outcome followed Mat's initial reaction to my post: Zenair would only test to US LSA standards "If we still have money left over after the completion of the German tests." I think that means "No. We will not test to US specs." While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the 601XL to flutter. Accordingly, ZBAG believes that we had to do something to encourage Zenair to test the 601XL to US specs. Since Zenair is apparently short on funds, ZBAG offered them $2500 so that they could afford to test to US specs. The email with our offer is appended below. If you would like to read my complete email exchange with Mat, let me know off line and I'll send you a copy. If you'd like a primer on how to handle load test results, see, e.g., http://www.vansaircraft.com/public/rv-10int2.htm .
Why should you care? Well, one reason is that your various operational limitation speeds, Vne, Va, Vc, etc., are a function of the wing strength. If the wing is only good to +5G (say) rather than +6G, then Vne might well be reduced from 160 mph to perhaps 150 or 140 mph and the gross weight would also be reduced. The calculations are beyond me, but the correlation between gross weight, load factors and Vne is clear. Reduce the wing load rating and you must reduce the design airspeeds and gross weight.
Another reason is that ZBAG is convinced that flutter is a factor in many, if not most, of the wing loss accidents. However, if Zenair tests a new airframe with lots of friction and cables tensioned to specs, the system stiffness could mask the tendency of the wings to flutter. That test would be unrepresentative of the 601XL fleet that includes aircraft with many flight hours and various levels of maintenance. Accordingly, we have asked Zenair to test at several cable tensions. The extra cost to test the fully instrumented airplane at three additional cable tensions would be very little. My message to Zenair is appended below below.
If Zenair accepts our offer that be would terrific. The tests would be done to LSA standards and Zenair wouldn't have to foot the whole bill. However, since they have not even acknowledged our message in three days, it looks like they may not accept the offer.
Every builder/owner of an 601XL/650 with a gross greater than 1041 lb has a stake in this. The load tests that Zenair are planning are irrelevant to your airplane! The GVT tests may be irrelevant to all 601XL/650's, unless Zenair takes data at cable tensions lower than specified 30 lb.
This is important. If you would like to see Zenair test the 601XL to US Specs, you might let them know. Tell the three Heintz brothers (listed below) that you want them to accept ZBAG's offer to help test the 601XL/650 airframe to US Specs. If they get the message from enough of their customers they might change their plans. Maybe. Time is short. If you care about the 601XL/650 tests, let Zenair know today.
Thanks for listening.
Terry
P.S.
Why is it so important to do the tests to US specs now? Well, if you do the tests in the sequence that Mat seems to favor: - Test to DAeC limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing yields after the the DAeC ultimate test, that may argue against using the same airframe for the ASTM tests. I'm awaiting an expert opinion on this point. But you probably need two airframes, two test setup expenses, etc.
But, if you use the following sequence: - Test to DAeC limit load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing doesn't yield in the ASTM limit load test, but does yield after the the DAeC ultimate test (a plausible outcome), one could probably use the same airframe for the ASTM ultimate test. I'm awaiting an expert opinion on this one also. But I think it is very likely that you could get away with one airframe and one test set up.
The lesson is that, by cleverly combining the DAeC test with the ASTM US specs test, you double the data for a 10 or 20% increase in test cost. If you do them separately, you probably double the costs. If you want the data you take the clever route.
| Quote: |
Date: Mon, 09 Mar 2009 23:10:02 -0600
To: micheintz(at)gmail.com,"S. Heintz / Zenith Aircraft Co." <seb.heintz(at)zenithair.com>, "heintz_mat" <heintz_mat(at)yahoo.com>
From: Terry Phillips <ttp44(at)rkymtn.net>
Subject: ZBAG Offer to Help Zenair Pay for Ground Vibration and Load Tests
Michael, Sebastien, and Mathieu
In response to five accidents involving in-flight breakup of Zenith 601XL's the Zenith Builders Analysis Group (ZBAG) was formed in 2008 to conduct independent engineering analyses of the Zenith 601XL airplane. Since ZBAG began in May 2008, in-flight breakup is suspected in at least three additional 601XL accidents. While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the airplane to flutter. Zenair recently announced a series of tests on the 601XL in response to German Government restrictions on 601XL operations. Mat Heintz has publicly stated that Zenair will only test to US LSA standards "If we still have money left over after the completion of the German tests."
Since Zenair funding is apparently critical at this time, ZBAG is stepping forward to help out.
This message is a formal offer from ZBAG to Zenair to contribute $2500 to Zenair to extend the German test series from the German requirements of 992 lbs gross to Zenair's US specifications of 1320 lbs (at) 6G. Since ZBAG funding will give the test results an implied approval by ZBAG the test plan must meet the following conditions: - The ground vibration test series should include measurements of the control system vibration frequencies at 3 or more of cable tensions below the specified tension of 30 lb +/- 5 lb. The range considered should include 20 lb, 10 lb and a tension of near zero (i.e. slack cables) that is still sufficient to produce an oscillatory response.
- We are concerned that the test plan may include only a single test at 30 lbs tension in a high friction, brand new airframe. This will make the GVT results irrelevant for real world 601XL's in the fleet.
- We have a documented instance of significant loosening of 601XL cables during a short cross country flight.
- The UK LAA has raised an issue regarding handling of fuel in the load calculations. Following the LAA's lead, the assumed fuel load should be the case of MTOW with minimum fuel.
- The load test program must include loading to limit load factor (4g), unloading and inspection of the wing for yielding and then a final loading to ultimate load.
- The airframe must be correctly supported for the tests by the engine mount, seats and tailplane. According to the LAA, in some earlier tests on the 601XL, the airframe was supported directly by the center spar which is an unrealistic condition that would bias the test results. The support of the airframe for future testing should provide for realistic loading of the center section and the uprights that shear the loads into the fuselage sides.
- Two positive load cases should be done.
- PHAA (Positive High Angle of Attack). This condition is representative of the VA / n1 condition. In this condition the wing center of pressure is forward (i.e. the leading edge of the wing is highly loaded) and the maximum forward chordwise components of drag load are applied to the wing. The wing is simultaneously loaded with maximum bending and shear loads. The airplane should be positioned in a high angle of attack attitude (i.e. upside down with nose down).
- PLAA (Positive Low Angle of Attack). This condition is representative of the VD / n1 condition. In this case the center of pressure is aft and thus the wing is critical for symmetric torsion together with maximum shear and bending. The airplane is positioned in a low angle of attack attitude.
- There must be an independent review of the test plans. xxxxxxxxxxxxx***, a xxxxxxxxxx professional aeronautical engineer - the xxxxxxxxx equivalent to a US FAA DER, is working with ZBAG. You have seen his reports and should be familiar with the quality of his work. xxxxxxxxxx is extremely busy just now, but he would make time to perform the review. The test plans would be released to xxxxxxxxx under a confidentiality agreement.
- Zenair must share the test results with xxxxxxxxxxx under the confidentiality agreement. xxxxxxxxxx could use the results of the ground vibration analysis to validate his flutter analysis models, but could not publish the test report.
ZBAG's sole intention in granting this funding to Zenair is to produce information that we believe is crucial to saving the lives of 601XL pilots and passengers who are flying their 601XL's at a gross weight of 1320 lbs. We sincerely hope that Zenair will accept our offer of financial assistance to extend the current test series. If our $2500 is insufficient to cover the cost of these tests, ZBAG will commit to an broad based fund raising effort using all possible resources to communicate with as many 601XL/650 builders and owners as possible to raise whatever additional funds are needed. I will personally commit to a contribution of $100.
I look forward to your response.
Sincerely,
Terry Phillips |
***The engineer asked that his name be removed from posts to the net.
Terry Phillips ZBAGer
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons are done; working on the wings
http://www.mykitlog.com/N47TP/ | Quote: | | http://www.matronics.com/Navigator?Zenith-List |
0123456789
[quote][b]
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eldenej(at)yahoo.com
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| Posted: Fri Mar 13, 2009 7:25 pm Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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I am deeply grateful, Terry, for all of this work. If there is an agreement to test to U.S. standards, and additional funds need to be raised, I, too, will contribute $100.
Elden Jacobson
xl, 3300
--- On Sat, 3/14/09, Terry Phillips <ttp44(at)rkymtn.net> wrote:
| Quote: | From: Terry Phillips <ttp44(at)rkymtn.net>
Subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane?
To: zenith-list(at)matronics.com
Date: Saturday, March 14, 2009, 2:07 AM
At 09:51 AM 3/7/2009 +0100, François Chapperon wrote:
| Quote: |
So you must know that last week , ZENAIR FRANCE (Michael Heintz) sent a 601XL to a private laboratory in HAMBOURG (Germany) to have dynamic examination in an artificial speed room ( blowers)
They also asked ZENAIR to have a dynamic gtest by loading wings , both sides, (intrados and extrados) with a charge of sand sacks .
Yours,
François Chapperon |
As François points out, Zenair Europe have committed to conducting a series of load tests and ground vibration tests so that the German government will lift the flight restrictions on German 601XL's.
Zenair's planned tests may be good news for all 601XL/650 owners whose planes are registered as European ultralights at 450 kg (472.5 kg [1041 lb] with BRS). The news is not so good for builders in the States and elsewhere where the 601XL/650 is spec'd for 1320 lbs (600kg) (at) +/- 6G, because Zenair plans to test the 601XL wing to only the European ultralight spec for the DAeC.
When I became aware of the upcoming German tests, I posted a message on the ZBAG forum listing test requirements that I believed were important based on what ZBAG's analyses have uncovered over the past 8 months. I then exchanged several emails with Mat Heintz on the subject. The final outcome followed Mat's initial reaction to my post: Zenair would only test to US LSA standards "If we still have money left over after the completion of the German tests." I think that means "No. We will not test to US specs." While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the 601XL to flutter. Accordingly, ZBAG believes that we had to do something to encourage Zenair to test the 601XL to US specs. Since Zenair is apparently short on funds, ZBAG offered them $2500 so that they could afford to test to US specs. The email with our offer is appended below. If you would like to read my complete email exchange with Mat, let me know off line and I'll send you a copy. If you'd like a primer on how to handle load test results, see, e.g., http://www.vansaircraft.com/public/rv-10int2.htm .
Why should you care? Well, one reason is that your various operational limitation speeds, Vne, Va, Vc, etc., are a function of the wing strength. If the wing is only good to +5G (say) rather than +6G, then Vne might well be reduced from 160 mph to perhaps 150 or 140 mph and the gross weight would also be reduced. The calculations are beyond me, but the correlation between gross weight, load factors and Vne is clear. Reduce the wing load rating and you must reduce the design airspeeds and gross weight.
Another reason is that ZBAG is convinced that flutter is a factor in many, if not most, of the wing loss accidents. However, if Zenair tests a new airframe with lots of friction and cables tensioned to specs, the system stiffness could mask the tendency of the wings to flutter. That test would be unrepresentative of the 601XL fleet that includes aircraft with many flight hours and various levels of maintenance. Accordingly, we have asked Zenair to test at several cable tensions. The extra cost to test the fully instrumented airplane at three additional cable tensions would be very little. My message to Zenair is appended below below.
If Zenair accepts our offer that be would terrific. The tests would be done to LSA standards and Zenair wouldn't have to foot the whole bill. However, since they have not even acknowledged our message in three days, it looks like they may not accept the offer.
Every builder/owner of an 601XL/650 with a gross greater than 1041 lb has a stake in this. The load tests that Zenair are planning are irrelevant to your airplane! The GVT tests may be irrelevant to all 601XL/650's, unless Zenair takes data at cable tensions lower than specified 30 lb.
This is important. If you would like to see Zenair test the 601XL to US Specs, you might let them know. Tell the three Heintz brothers (listed below) that you want them to accept ZBAG's offer to help test the 601XL/650 airframe to US Specs. If they get the message from enough of their customers they might change their plans. Maybe. Time is short. If you care about the 601XL/650 tests, let Zenair know today.
Thanks for listening.
Terry
P.S.
Why is it so important to do the tests to US specs now? Well, if you do the tests in the sequence that Mat seems to favor: - Test to DAeC limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing yields after the the DAeC ultimate test, that may argue against using the same airframe for the ASTM tests. I'm awaiting an expert opinion on this point. But you probably need two airframes, two test setup expenses, etc.
But, if you use the following sequence: - Test to DAeC limit load, unload, inspect
- Test to ASTM limit load, unload, inspect
- Test to DAeC ultimate load, unload, inspect
- Test to ASTM ultimate load, unload, inspect
And, the wing doesn't yield in the ASTM limit load test, but does yield after the the DAeC ultimate test (a plausible outcome), one could probably use the same airframe for the ASTM ultimate test. I'm awaiting an expert opinion on this one also. But I think it is very likely that you could get away with one airframe and one test set up.
The lesson is that, by cleverly combining the DAeC test with the ASTM US specs test, you double the data for a 10 or 20% increase in test cost. If you do them separately, you probably double the costs. If you want the data you take the clever route.
| Quote: | | Quote: | Date: Mon, 09 Mar 2009 23:10:02 -0600
To: micheintz(at)gmail.com,"S. Heintz / Zenith Aircraft Co." <seb.heintz(at)zenithair.com>, "heintz_mat" <heintz_mat(at)yahoo.com>
From: Terry Phillips <ttp44(at)rkymtn.net>
Subject: ZBAG Offer to Help Zenair Pay for Ground Vibration and Load Tests
Michael, Sebastien, and Mathieu
In response to five accidents involving in-flight breakup of Zenith 601XL's the Zenith Builders Analysis Group (ZBAG) was formed in 2008 to conduct independent engineering analyses of the Zenith 601XL airplane. Since ZBAG began in May 2008, in-flight breakup is suspected in at least three additional 601XL accidents. While ZBAG's analysis is ongoing, enough has been learned to raise concerns about the strength of the 601XL wing and the susceptibility of the airplane to flutter. Zenair recently announced a series of tests on the 601XL in response to German Government restrictions on 601XL operations. Mat Heintz has publicly stated that Zenair will only test to US LSA standards "If we still have money left over after the completion of the German tests."
Since Zenair funding is apparently critical at this time, ZBAG is stepping forward to help out.
This message is a formal offer from ZBAG to Zenair to contribute $2500 to Zenair to extend the German test series from the German requirements of 992 lbs gross to Zenair's US specifications of 1320 lbs (at) 6G. Since ZBAG funding will give the test results an implied approval by ZBAG the test plan must meet the following conditions: - The ground vibration test series should include measurements of the control system vibration frequencies at 3 or more of cable tensions below the specified tension of 30 lb +/- 5 lb. The range considered should include 20 lb, 10 lb and a tension of near zero (i.e. slack cables) that is still sufficient to produce an oscillatory response.
- We are concerned that the test plan may include only a single test at 30 lbs tension in a high friction, brand new airframe. This will make the GVT results irrelevant for real world 601XL's in the fleet.
- We have a documented instance of significant loosening of 601XL cables during a short cross country flight.
- The UK LAA has raised an issue regarding handling of fuel in the load calculations. Following the LAA's lead, the assumed fuel load should be the case of MTOW with minimum fuel.
- The load test program must include loading to limit load factor (4g), unloading and inspection of the wing for yielding and then a final loading to ultimate load.
- The airframe must be correctly supported for the tests by the engine mount, seats and tailplane. According to the LAA, in some earlier tests on the 601XL, the airframe was supported directly by the center spar which is an unrealistic condition that would bias the test results. The support of the airframe for future testing should provide for realistic loading of the center section and the uprights that shear the loads into the fuselage sides.
- Two positive load cases should be done.
- PHAA (Positive High Angle of Attack). This condition is representative of the VA / n1 condition. In this condition the wing center of pressure is forward (i.e. the leading edge of the wing is highly loaded) and the maximum forward chordwise components of drag load are applied to the wing. The wing is simultaneously loaded with maximum bending and shear loads. The airplane should be positioned in a high angle of attack attitude (i.e. upside down with nose down).
- PLAA (Positive Low Angle of Attack). This condition is representative of the VD / n1 condition. In this case the center of pressure is aft and thus the wing is critical for symmetric torsion together with maximum shear and bending. The airplane is positioned in a low angle of attack attitude.
- There must be an independent review of the test plans. xxxxxxxxxxxxx***, a xxxxxxxxxx professional aeronautical engineer - the xxxxxxxxx equivalent to a US FAA DER, is working with ZBAG. You have seen his reports and should be familiar with the quality of his work. xxxxxxxxxx is extremely busy just now, but he would make time to perform the review. The test plans would be released to xxxxxxxxx under a confidentiality agreement.
- Zenair must share the test results with xxxxxxxxxxx under the confidentiality agreement. xxxxxxxxxx could use the results of the ground vibration analysis to validate his flutter analysis models, but could not publish the test report.
ZBAG's sole intention in granting this funding to Zenair is to produce information that we believe is crucial to saving the lives of 601XL pilots and passengers who are flying their 601XL's at a gross weight of 1320 lbs. We sincerely hope that Zenair will accept our offer of financial assistance to extend the current test series. If our $2500 is insufficient to cover the cost of these tests, ZBAG will commit to an broad based fund raising effort using all possible resources to communicate with as many 601XL/650 builders and owners as possible to raise whatever additional funds are needed. I will personally commit to a contribution of $100.
I look forward to your response.
Sincerely,
Terry Phillips |
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***The engineer asked that his name be removed from posts to the net.
Terry Phillips ZBAGer
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons are done; working on the wings
http://www.mykitlog.com/N47TP/ | Quote: |
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chapred(at)free.fr
Guest
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| Posted: Sat Mar 14, 2009 2:23 am Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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Hello !
Yesterday French aeronautics authorities decided to restrict flying with 601 XL ultra-light version .
means maximum weight is : 992lb without parachute and 1042 with parachute (total rescue system)
1)All owners must check cables tension according to Service Bulletin and check it again every 50 hours.
2)Vne : is restricted to 180km/h è97 mph !!!!!
Position of authorities could be modified according results of German test .
For those who understand French, the link:
http://www.aviation-civile.gouv.fr/html/avia_leg/navigabilite/CN/CN2009ULM001_ZENAIRCH601XL.pdf
On my side I have contacted my dealer, and sent a personal e-mail to Michael Heintz…
I agree with your idea; if the 601 can get through USA tests it would be better as weight (1340lb)is higher than in Europe.
François
[quote][b]
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Al Hays
Joined: 01 Oct 2007
Posts: 42
Location: Gore, VA
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| Posted: Sun Mar 15, 2009 6:53 am Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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Sabrina,
I absolutely agree that it would seem pretty easy. However, I am only
speaking up here in response because I fear someone may attempt
exactly that simple "spring loaded set of three pulleys" and suffer
unintended consequences. While I have installed and worked on quite a
few things that use spring loaded tensioning systems in cars, farm
equipment, and mechanical systems in buildings, I don't believe it
would be a safe and reliable add-on to the control cables. The
tension we adjust to or check for in pre-flight is with the aircraft
at rest. In flight, those cables might be subject to quite a variance
of forces. I'd worry that, among other things, a potential flutter
problem could be exacerbated by the spring. I suspect properly
designing a spring loaded auto-tensioning system by qualified
engineers and dynamicists would be cost-prohibitive. Of course, I'd
be happy to be proven wrong on this.
I really do hope that Zenair will extend the testing to meet U.S.
specs and in an ideal world, they would be able to say "thanks for
offering, but we've decided to do that anyway and don't need the
money". I'd like to know that in the event of cables unexpectedly
becoming slack for whatever reason (possibly even due to builder
error), the plane could be flown to a safe arrival on the ground.
I'll be willing to make additional contribution to fund testing if
needed.
Al Hays
alhays(at)hickoryhillfarmsheep.com
N5892H reserved
On Mar 15, 2009, at 12:25 AM, Sabrina wrote:
| Quote: |
"2)Vne : is restricted to 180km/h �97 mph !!!!!"
180 km/h = 112 mph = 97 knots and they are assuming slack cables
I can't imagine anyone on this list flying their XL over 112 MPH
with slack cables...
it is so easy to reach behind the seat on the pre-flight and check
them...
Until we know more, it would seem pretty easy to design a spring
loaded set of three pulleys to maintain minimal aileron balance
cable tension... maybe do that with the $2500 rather than paying
someone to do something they already have a duty to do.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 34628#234628
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Sun Mar 15, 2009 8:49 am Post subject: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airplane |
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The springs on the Cirrus are probably to help coordinate turns and
help its spin resistant characteristics. As I recall, the Cirrus
aircraft were exempted from much of the spin testing requirements
during certification because they incorporated many features to make
them spin resistant. The springs on the Cessna operate the nose-wheel
steering. Those springs aren't there to keep the cables properly
tensioned.
Adding pulleys and springs to the aileron control system will add
unnecessary complexity and additional failure modes. If one of those
springs let go in flight, you might find yourself thoroughly screwed.
If it turns out that there is a problem with the ailerons, the
simplest solution would be to counter-balance them. A few people have
already devised modifications for that.
| Quote: |
Cirrus have rudders interconnected to the ailerons with springs.
Cessna's have spring tensioned rudder cables.
A lot of engineering was done on this issue in 2007:
http://www.casa.gov.au/airworth/airwd/ADfiles/UNDER/CIRRUS/CIRRUS-009.pdf
If ZBAG is using an Australian engineer, he should have ready access
to all this data... maybe $2500 is enough, maybe not...
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--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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steveadams
Joined: 10 Jan 2006
Posts: 191
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| Posted: Mon Mar 16, 2009 5:02 am Post subject: Re: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airp |
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I'm not building a 601, so this is just a comment from an outside observer regarding testing. First off, I think testing is a good thing and should relieve a lot of peoples anxiety, or possibly demonstrate an unforeseen design flaw. However, the notion that you need to test the airframe with multiple different cable tensions is ridiculous. Why stop there, why not also test one with a few loose bolts, or maybe one built with unspecified rivets, over sized rivet holes, or maybe with a few wasp nests in the trailing edge of one aileron. Test one that has been abused with poor maintenence, aerobatics, and repeated overstressing of the airframe. The airplane has specifications including rigging and cable tensions. To expect them to test an airframe not built or flown to specification is just silly. Build, rig, and fly your plane to specs and keep it that way.
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Mon Mar 16, 2009 1:03 pm Post subject: Re: Is Your CH601XL/650 a 1320 lb Airplane or a 1041 lb Airp |
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I'd donate $100 to see a real 601XL tested to US standards.
[quote="eldenej(at)yahoo.com"]I am deeply grateful, Terry, for all of this work. If there is an agreement to test to U.S. standards, and additional funds need to be raised, I, too, will contribute $100.
Elden Jacobson
xl, 3300
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