Update from the 22nd Jan meeting

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Ian Melville
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Joined: Mon Feb 11, 2008 7:21 pm

Update from the 22nd Jan meeting

Post by Ian Melville » Tue Jan 27, 2009 10:26 pm

On the 22nd Jan 2009 we had a meeting with Nigel Bamber at the LAA HQ to move the CX4 project forward. The meeting was very positive, and the four attendees(and one apology) were please to see that the LAA is taking a pragmatic approach to the approval of this delightful aircraft.

The meeting started by making sure that everyone had the same versions of the drawings, as it would appear that those with early plans were not always up-to-date with developments. Then followed a lengthy discussion of the compliance with CS-VLA, in particular the load testing and structural analysis. Dave Thacther has provided proof or practical load tests, however there were some grey areas, one of which had been identified and resolved prior to the meeting. This does not mean that the CX4 is deficient in the remaining areas, but we do need to prove by stress analysis or load testing that it will comply with the CS-VLA standards. Nigel will assist us by providing as list of engineers able to undertake there calculations. Through us, he will be able to steer this third party and ensure that we are not taken for a ride.

After a break to sample Turwestons bacon baps and tea, discussions centred around what options would by included from the start. The consensus was that the VW engine was the only practical choice at the moment. The cost of the UL260 defeating the object of affordable flying. The Aux tank would not be used as a 10.5USG forward tank would give sufficient endurance for the type of flying the CX4 would be used for. A roll-over bar will not be required by the LAA as there are many examples on the LAA fleet that do not meet CS-VLA in this respect. A builder may desire the additional protection of a roll-over bar, but we would have to not only provide a design that meets the CS-VLA requirements, but also prove that it does not compromise the structural integrity of the fuselage. The LAA may also require new loading tests. Also discussed were the changes for the 'Tall and Wide' version. The general consensus was that the 'Tall' option was required, but not the 'Wide' option. The 'wide' option makes changes to the top longeron, and the possibility that load testing would have to be repeated.

Jon Ward brought in the parts that he had constructed so far. Wing and centre section spars, ribs and formers. It was great to get our hand on a bit of CX4, instead of the paper version.

You know that you have done as much as can be done at a meeting when we start discussing the panel fit, paint and upholstery :roll:

In the next few weeks Nigel will be compiling a status report with action points for the team. We expect that there will be more questions in the future but we are all sufficiently confident that the CX4 project is going to take flight.


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Post by tlangdon12 » Thu Jan 29, 2009 8:19 pm

Thanks for the update Ian.

Are the group willing to publish the status report and progress on the action points?

Was there any discussion as to how to pay for the stress analysis?

Best Wishes


Ian Melville
Posts: 1000
Joined: Mon Feb 11, 2008 7:21 pm

Post by Ian Melville » Thu Jan 29, 2009 9:52 pm

Hi Tony,
At the moment we cannot publish any details until Nigel returns to us with the report. We have yet to decide if it will be make public in it's entirety or just a more detailed summary. I am keen that the wider public should be aware of the progress, but do not want to jump the gun with info that is inaccurate or subsequently change.

Until we know the costs (one of the action points) we cannot discuss how the additional calculations will be funded. It is probable that they will be split between the current builders. Whether we are able, or want to reclaim some of that back from future builders is debatable.

John Wighton
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Joined: Sun Mar 08, 2009 4:04 pm
Location: Stansted UK

CX-4 Stress Calcs

Post by John Wighton » Tue Apr 21, 2009 9:00 pm

I have an interest in the CX-4 and wonder what the current status of the design submission is? I own Aerodesign(UK) (the trading name of Ultraflight Ltd) which provides commercial services for aircraft design, stress analysis etc (l am listed by LAA in their Engineers referral list). It may be that l can provide the group with some help in getting the design dossier prepared for Nigel to critique.

For my part l would prefer the UL260 engine and would proceed on basis of stressing for the power/torque/weight of this engine. A standard VW mount could be used or adapted (the stress requirement being to check the firewall/structure).

I would argue that an acceptable MoC for this aircraft would be existing test data and analysis. I wonder why the CS-VLA code has been mentioned as a basis for the design?

John Wighton

Ian Melville
Posts: 1000
Joined: Mon Feb 11, 2008 7:21 pm

Post by Ian Melville » Wed Apr 22, 2009 8:39 pm

Hi John,
At the moment we seem to be stuck on the stress analysis caused by design changes that the LAA were not aware of, and invalidating previous tests. There are some areas that has no analysis or test data as well I am trying to get a better picture at the moment from David Hey who has this as an action point. I don't think there are insurmountable issues, but it is more than the layman can do using TLAR design methods.

I also would like to see the UL260 as an approved powerplant (and the jab2200). It is highly likely we will still require the VW variants to be approved first, and as you point out there has been previous work that can be adapted.

Not sure what an MoC is? It is the LAAs insistance that CS-VLA is used as a basis. There does seem to be some lattitude is certain areas, if we can present a valid case.

Can I or Dave contact you when I have had some feedback from the UK builders?

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