LAA Approval

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LAA Approval

Postby Gerry Holland » Mon Mar 24, 2008 8:33 pm

I'm considering the CX4 as my next build and referred to the LAA Engineering statement regarding type approval on Website. Why is it that the LAA has found technical shortcomings in design after initially trumpeting the opportunity this aircraft could bring to plans based home building. This is an Aircraft that does fly albeit early days and is being built by up to 100 builders in other countries without undue hindrance. It has modifications being applied as problems arise, no different to any engineering development.
Sorry to sound negative but experience of past PFA building projects has left me with a jaundiced view on the politics and prejudices of the Engineering leadership. The onus that the Designer should take onboard the changes needed for the LAA permit is near laughable along with the inference that LAA Design and Stress Engineers would assist at a price. We need reasons why the design has flaws first!
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Gerry
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Postby ivanmanley » Mon Mar 24, 2008 9:08 pm

Gerry,

The LAA like the design and are keen to see it fly over here. Remember, we operate a different system than in the US where they enjoy certain freedoms to build what they like as long as it's built "right". Our permit system is not quite so "experimental" as theirs, and the design itself is scrutinised far more. There are essentially no really big problems with the CX4 and it looks like it's just some parts of the control system that do not meet the standards to which the LAA are obliged to apply. These should be easily rectified and I can't see any stress work amounting to much if anything, but I suppose they have to say that any costs fall to the builder/s to cover themselves? The points that are/were in question are 1. The undercarriage (now accepted) 2. the rudder control system and 3. An unbushed pivot bolt through the control columb. There may also be odd thing or two thrown up during construction, as is often the case.

Yes, it would have been nice if they'd been clearer when they put the article in the magazine, but there you go :roll: As it stands, the design IS good and WILL end up on the LAA's approved list! Myself and at least three others have started down the road to ensuring that it does!

Ivan
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LAA Approval

Postby Gerry Holland » Mon Mar 24, 2008 10:20 pm

Ivan Hi!
Thanks for the update and your optimism. I feel happier now.
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Gerry
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Postby David Hall » Tue Mar 25, 2008 9:24 am

From the Thatcher Yahoo Group, it has been suggested that the rudder pedal arrangement of the Harmon Rocket is studied with reference to any modification to that in the CX4 - it being of a similar design?

If it is the same, the Rocket set-up will certainly be adequately robust!
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Postby Guest » Tue Mar 25, 2008 1:32 pm

There's one customer in the USA who is fitting the UL Power UL260i engine to the CX4, so this will be a great little set up.

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Mark Jones
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Postby David Hall » Tue Mar 25, 2008 2:06 pm

That is excellent news, I was just discussing that engine with my Inspector :D
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Postby Guest » Tue Mar 25, 2008 2:11 pm

The Good news here is that UL Power have designed the engine mount for them too so if you do decide to put this engine in the Thatcher CX4 I can supply you the engine mount too..

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Postby ivanmanley » Tue Mar 25, 2008 3:52 pm

Well it certainly looks like a lovely engine, but at three times the price of a new VW kit, it certainly isn't the cheap option. An 1834 VW powers the CX4 along nicely at 125mph and doesn't struggle so why spend that much more? Stick one on a VP2 and apart from the fact that the engine would be worth four times the value of the aeroplane with a VW already in it, I can see the advantage (ie, the bl@@dy thing might actually climb).

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Postby Guest » Tue Mar 25, 2008 4:16 pm

Ivan, your points are well made and justified but I never mentioned the pice diffrence. It was mearly a statment pointing out that there is another option.

Climb is not the only advantage, its 95 hp at 3300 rpm, you have multi port fuel injection ( no carb Iceing or carb heat ) electronic ignition with variable timing, and temperature pressure compentation, and its silenced too and weighs 74 kg installed but some of that is fuel pumps and ECU which can be mounted further back if desired.

The price is for everything you need ( bar fuel fitting kit ) to fit it to the aircraft and engine mount.

If UL Power get 10 serious interested parties ( money on the table ) for an inverted dry sump oil system, they will develope it and have it as an option. That will then make it a fully aerobatic engine what with the fuel injection.
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Postby ivanmanley » Tue Mar 25, 2008 5:03 pm

And I certainly didn't knock the engine :)

It does look superb and would be great on the CX4.

For me though, the attraction of the CX4 is the performance offered on such a cheap and cheerful engine as a VW.

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Postby Ian Melville » Tue Mar 25, 2008 7:15 pm

Great mind think alike or fools never differ :?:

I too have been looking at the UL260, Cost as Ivan points out is the one area that put me off. I am well aware of what you get for your money.
I wasn't aware that it was 3 times the cost.

The downside for VeeDubs to me is that the are old tech, and the larger capacity engines are rumoured to have reliability issue due to the crankcase strength. (Revmaster get round this by using a new crankcase in one of there models). Building one from a pile of bits also scares me, but I am sure with the right advice I can get over that.

Will the CX4 Take 95hp anyway? and not exceed VNE in level flight :shock:
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Postby David Hall » Tue Mar 25, 2008 7:25 pm

For me, a modern engine with silencer and no carb icing problems would be an attractive option.

With the inverted dry sump oil system, there's one aircraft the UL is perfect for - an aerobatic Twister 8)
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Postby Guest » Tue Mar 25, 2008 7:30 pm

Ian Melville wrote:Great mind think alike or fools never differ :?:

Will the CX4 Take 95hp anyway? and not exceed VNE in level flight :shock:


You could alway get the ECU remaped to bring the rev limiter down to more exeptable levels. Its currently set at 3400 rpm

95 hp @ 3300 rpm / 82 hp @ 2800 rpm

Or Gate the throttle, pitch the prop. Low end rpm is still very good on the UL260i as the power torque curve is very even. Idle rpm has been demonstrated down to 650 rpm with no lumpiness and throttle response is very smooth and linear.
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Postby Ian Melville » Tue Mar 25, 2008 7:36 pm

Gate the throttle would be the better idea, then you can have WEP (War Emergency Power) to get away from bandits in VP1s :D

I'm a way off yet from making the decision
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Postby Guest » Tue Mar 25, 2008 7:39 pm

LOL, yeah, a bulsa gate with wax block behind to prove you have used it, fantastic. :twisted:

I am slowly working towards getting My Escapade microlight version flying with the UL260i in as my company demostrator for the engine. Friend of mine has his UL260i up and running in an Escapade VLA to 499kg and its a dream to fly behind.
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