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UK grounding to be lifted soon ?

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aerobat

Joined: 07 Nov 2008
Posts: 21
Location: UK

Posted: Tue Jan 27, 2009 9:15 am Post subject: UK grounding to be lifted soon ?

From the Zenair Europe site it seems the UK grounding could be lifted after some modifications agreed between the LAA and Zenair.



Here is the Zenair Site link and text below 



http://www.zenairulm.com/News/index_files/Page849.htm

Information gathered at the meeting of January 23, 2009 between Zenair and the UK LAA: Like most other experimental kit aircraft available prior to 2005, the Zodiac CH 601 XL was designed to meet its stated specifications, performances and design parameters without specifically relying on JAR, VLA, LSA, or NTSB standards. After 2005 (and the introduction of the US “Light Sport Aircraft” definition), the CH 601 XL design was slightly modified so as to meet the ASTM standards for light sport aircraft (LSA). After 2005, all US-made CH 601 XL built to Zenair specifications meet the ASTM rules; in 2009, the CH 601 XL will mostly be replaced with the newer and sleeker CH 650 model, which also meets the ASTM definition for LSA.



 



In Europe, some countries (like the UK) simply do not recognize the national US Light Sport Aircraft (LSA) regulations. Instead, regulators (like the LAA in the UK) ask that imported aircraft meet some of the more stringent ICAO (international) VLA requirements. Structural tests conducted by CZAW in the past were designed to meet Czech ultralight and German LTF-UL requirements, but also to demonstrate that the CH 601 XL design meets specific elements of the VLA rule - to satisfy UK requirements. 



 



Recently, after a thorough review of the way some of the tests were conducted, the LAA has raised questions about whether or not the pre-2005 CH 601 XL actually meets some the more stringent VLA standards that it requires. In order to eliminate such doubts, Zenair has now reviewed a number of LAA-proposed modifications which, if installed, would ensure all versions of the CH 601 XL/CH 650 design far exceed specified VLA minimum requirements. This would allow the UK to lift the grounding order it currently has in effect without the need for additional load testing. 



 



These UK-applicable changes (for MTOW of 560 Kg.) include modifications to the control system (installation of a “spring-booster” for the elevator, and of balanced counter-weights for the ailerons); modifications to the center spar (addition of stiffeners allowing for theoretical operation of the aircraft with “loose spar-bolts”); and modifications to the POH (addition of a statement about “Max Zero Fuel Weight”)… The reason for the required aileron counter-weights is because the LAA does not accept “maintaining cable tensions within specifications” as adequate protection against a potential risk of flutter.



 



While UK CH 601 XL owners will need to install these LAA mandated “upgrades” to their 560 Kg gross-weight aircraft, it is not yet known how much weight, cost and complexity these changes will add up to; basic aircraft performances should not be affected in any way. After these discussions between Chris Heintz and LAA engineers, LAA officials are now finalizing their list of special requirements for UK-registered CH 601 XL. A “retrofit kit” will be made available for UK CH 601 XL owners once LAA requirements have been finalized.

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psm(at)att.net
Guest

Posted: Tue Jan 27, 2009 9:41 am Post subject: UK grounding to be lifted soon ?

Aeorbat,



Thank you for this very interesting post.



I hope Chris will be issuing a general 

distribution letter with his opinion on the LAA 

changes and that someone (Chris, or ZAC?) will 

distribute detailed drawings for the changes 

Chris feels are appropriate for all the different versions of the XL



I am particularly interested in learning whether 

the counterbalance proposal applies equally to 

ailerons with piano hinges and the hingeless (original) aileron design.



Paul

XL getting close





 	  Quote: 	
		  Recently, after a thorough review of the way 

some of the tests were conducted, the LAA has 

raised questions about whether or not the 

pre-2005 CH 601 XL actually meets some the more 

stringent VLA standards that it requires. In 

order to eliminate such doubts, Zenair has now 

reviewed a number of LAA-proposed modifications 

which, if installed, would ensure all versions 

of the CH 601 XL/CH 650 design far exceed 

specified VLA minimum requirements. This would 

allow the UK to lift the grounding order it 

currently has in effect without the need for additional load testing.



These UK-applicable changes (for MTOW of 560 

Kg.) include modifications to the control system 

(installation of a “spring-booster” for the 

elevator, and of balanced counter-weights for 

the ailerons); modifications to the center spar 

(addition of stiffeners allowing for theoretical 

operation of the aircraft with “loose 

spar-bolts”); and modifications to the POH 

(addition of a statement about “Max Zero Fuel 

Weight”)… The reason for the required 

aileron counter-weights is because the LAA does 

not accept “maintaining cable tensions within 

specifications” as adequate protection against a potential risk of flutter.

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johnd(at)data-tech.com
Guest

Posted: Tue Jan 27, 2009 10:19 am Post subject: UK grounding to be lifted soon ?

Hi Sabrina,



Which accident are you referring to when you say:



Did the LAA review the US accident where it was clear that 6+ threads were showing on the main spar bolts?



I've been keeping up with the NTSB reports and dont see any references 

to main spar bolts.



Thanks,

John Davis

601XL - N601JD

3.5 Hrs and counting



Sabrina wrote:

 	  Quote: 	
		   



 Now that the findings are out, all those LAA insiders  that have been writing to us and the list should answer these questions:



 Did CZAW ever redesign the center spar webs to shift it those two extra degrees?



 Did Zenith ever supply center spar webs to CZAW that were bent to the proper shape for the CZAW modification?



 Is the current 650 center spar just the old 601XL center spar?   



 Does the LAA think that the twisting of the center spar webs, re-bending of the center spar webs or re-set of the center spar webs contributed to the accidents they reviewed?



 Did the LAA review the US accident where it was clear that 6+ threads were showing on the main spar bolts?



 Are the "loose spar bolts" they are talking about: not torqued properly or torqued against their own shaft rather than the spar?



 Could the spar bolts that were found not to be torqued properly in that state because the bolt tip was cut off to save weight and the cutting off heated and damaged the nylo nut?





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 27123#227123

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Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Tue Jan 27, 2009 2:00 pm Post subject: Re: UK grounding to be lifted soon ?

 	  Quote: 	
		  The reason for the required aileron counter-weights is because the LAA does not accept “maintaining cable tensions within specifications” as adequate protection against a potential risk of flutter. 	




I have a problem with this. I have yet to see a single bit of evidence that flutter caused an accident.

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601XL Under Construction
See my progress at www.peoamerica.net/N601WR

psm(at)att.net
Guest

Posted: Tue Jan 27, 2009 3:13 pm Post subject: UK grounding to be lifted soon ?

Hi Gig,



I agree with your comment -- to a certain 

degree.  I don't think flutter is behind the XL 

accidents, so I don't think aileron balancing is 

called for.  Indeed I don't think there is an XL 

aileron flutter issue in the real world - just in 

the minds of some people trying to guess what might be happening.



It seems to me the LAA is a government authority 

in Great Britain with responsibility for aviation 

safety.  Since the UK is a "Nanny State" when it 

comes to aircraft certification compared to the 

FAA it is reasonable for them to demand changes 

which might not help but certainly wouldn't hurt 

(as long as you don't mind the additional expense 

and weight).  Their edict should not directly 

impact anyone outside their jurisdiction.



I would like to see a letter from Chris or some 

sort of release from ZAC, Zenair, etc. with a 

more complete discussion of the issues addressed 

by the LAA.  In Particular, I would like to 

understand the scope of the design changes which 

addresses which of the many different XL 

configurations need help and which ones don't. 

The LAA edict applies to LAA certified planes 

which, I believe, have relatively standard CZAW configuration.



My XL has hingeless ailerons, so I am comfortable 

that the design is sound in that area.  As to the 

wing attach bolts being loose, I think some sort 

of inspection schedule is appropriate for 

checking them.  Perhaps annual inspection is 

appropriate once the first few flights have been 

accomplished.  Perhaps the risk is higher than I 

might guess so I would like to hear someone more 

knowledgeable take a position on this.



As to the aileron cables and their tension, I 

think this should be a preflight inspection issue 

- at least for new planes and ones that haven't 

been regularly flown and inspected.  I don't 

think we need an actual tension measurement, but 

a look and "Pluck" inspection behind the pilot's 

seat would be easy to do and should identify 

cables that have become overly loose.



I hope we can all be comfortable with the notion 

that we are not responsible for the LAA's actions 

- only for making sense of the technical 

information presented and taking action WE deem appropriate for our own planes.



Paul

XL getting close

At 02:00 PM 1/27/2009, you wrote:

 	  Quote: 	
		   > The reason for the required aileron 

 counter-weights is because the LAA does not 

 accept “maintaining cable tensions within 

 specifications” as adequate protection against a potential risk of flutter.

I have a problem with this. I have yet to see a 

single bit of evidence that flutter caused an accident.

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leinad

Joined: 19 Sep 2006
Posts: 283
Location: Central Virginia

Posted: Wed Jan 28, 2009 5:56 pm Post subject: Re: UK grounding to be lifted soon ?

Gig,

I'd like to see the data that they made these judgements from too, but from what we all know I think they're reasonable.

1.  You've got something statistically significant happening with XL crashes.

2.  Even the EAA recommends control surface balancing because unbalanced control surfaces are PRONE to flutter.

3.  Reports have been made by members of this list of experiencing flutter.   I'd call that evidence.

4. There is is also some evidence (not everyone is convinced) that some of these incedences happened in straight and level flight. 

5.  Zenith proactively put out warnings about maintaining control cable tension.  (I think they said to prevent flutter, not sure on this point)

None of this is proof that any of the failures were due to flutter, but some might conclude it's enough evidence so that some precautions should be made against that as a possible culprit.

I hope Zenith has some recommendations out soon,as I'm about to begin assembling wings.

Dan

 	  Gig Giacona wrote: 	
		   	  Quote: 	
		  The reason for the required aileron counter-weights is because the LAA does not accept “maintaining cable tensions within specifications” as adequate protection against a potential risk of flutter. 	




I have a problem with this. I have yet to see a single bit of evidence that flutter caused an accident.

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_________________
Scratch building XL with Corvair Engine

Gig Giacona

Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA

Posted: Thu Jan 29, 2009 6:23 am Post subject: Re: UK grounding to be lifted soon ?

Dan,



I don't disagree with anything you wrote. BUT, the single government report that has had any actual data specifically ruled out flutter as the cause for the accident. 



If there is a problem with the 601XL finding the cause is being hampered by organizations harping on the one thing that has been shown NOT to be the cause in the one accident that has been at least somewhat investigated.

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_________________
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601XL Under Construction
See my progress at www.peoamerica.net/N601WR

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