Which non-certified aircraft would you buy if there were no restrictions on European flight and parking?

alioth wrote:

… first it seems to begin an oscillation to the left,…

I also think that the cause of the accident is control surface flutter. I found a statement of the builder/pilot on the internet in which he writes that the breakup occurred at 235km/h. The aircraft had been tested and demonstrated up to 300km/h (almost 150kt). They had flown the same routine only a short time before in front of officials of the German authority in order to get the display permission. The breakup was on the 35th flight of the model. The engine which delivers 200lb of thrust survived the crash.

My point really is that with a homebuilt aircraft built by someone else you really don’t know where the weak spots are. If the rudder trim linkage can come off as Peter describes, who knows what other defects were built into the controls? A tiny slackness in the elevator control can cause exactly the kind of flutter shown in the video with ecactly the same result. On flight number 35 as well as on flight 350. It’s a gamble, nothing else.

My experiences with buying and de-bugging certified planes have been similar to that described here for Experimental planes. On the first certified plane it was fuel system issues, tanks and wing covering installed incorrectly, and on the second it was dangerous 30 year old electrical issues under the panel, a rat’s nest that included a lot of uncertified parts. A lot of that stuff won’t be picked up by an annual inspection, or series of them, especially if it’s an unusual type. I think when buying something common like an experimental RV, and assuming its one that appears to be well built, you’re actually less likely to find construction or maintenance issues. In any case, I don’t think you can expect to buy and fly any plane without ‘sorting it out’, maybe even a new one, it’s the real world nature of the beast…

Re foam and glass homebuilts, I remember hot wiring wing cores with my dad but that’s not being done by a lot of people today.

Re flutter, the Dragonfly (a Quickie derivative) that my dad built actually had minor elevator flutter, a buzz through the controls that did not diverge, and it was common on the type. Taper pins versus straight pins to tighten up the linkages fixed it. Nowadays the average guy is building a type that’s a lot more numerous and well developed. In the 70s and 80s it was different, not worse because a lot of interesting types were developed, but certainly more experimental and hazardous than what the average guy does today.

I think it would be fun to build a Quickie single seater today with a more modern engine than the Onan.

Silvaire wrote:

Re flutter, the Dragonfly (a Quickie derivative) that my dad built actually had minor elevator flutter, a buzz through the controls that did not diverge, and it was common on the type. Taper pins versus straight pins to tighten up then linkages fixed it. Nowadays the average guy is building a type that’s a lot more numerous and well developed.

Well, buzz is something completely different than flutter and that is completely different from control surface flutter and that is different from divergence, witch is a static problem and not a dynamic. Anyway, there are much opportunities to fuck up if you don’t understand what you’re doing. Of course, the problems grow if you have long elastic structures, compared to the short stiff design of the VANs. Kits like the VANs are very well tested by now and if you comply to the (very good) plans, you should have a nice aircraft. Same goes for the Falco or the Europa, as far as I can tell.

Silvaire wrote:

My experiences with buying and de-bugging certified planes have been similar to that described here for Experimental planes. On the first certified plane, it was fuel system issues, tanks and wing covering installed incorrectly, and on the second it was dangerous 30 year old electrical issues under the panel, a rat’s nest that included a lot of uncertified parts.

Maybe, but in an uncertified plane, dangerous crap is legal and in a certified aircraft it isn’t and hence you compare systematic crap with the failure to comply to maintenance/repair standards.

Peter wrote:

I would have thought that using the stiffness of control linkages is a bad way to keep a lid on flutter, because they are unavoidably elastic. Surely control surfaces should be flutter-stable on their own, without any linkages attached?

It’s not related to stiffness, what you’re doing is damping with friction. If I understand correctly, friction damping is often used to suppress the amplification factor of vibration, and given that no system will be perfectly balanced I think you need some level of friction damping if you cross a flow excited natural frequency. Maybe somebody else will understand this better, I only direct the activities of vibration analysts, I am not one myself

mh wrote:

buzz is something completely different than flutter and that is completely different from control surface flutter and that is different from divergence, witch is a static problem and not a dynamic

What I’m talking about is a situation wherein the elevator circuit was just damped enough and at certain airspeeds the elevator would buzz fairly violently at high frequency through the elevator control linkages. Additional friction introduced by eliminating clearance in the elevator control linkages suppressed the issue. I don’t think that’s a static problem, but maybe I misunderstand.

mh wrote:

in an uncertified plane, dangerous crap is legal and in a certified aircraft it isn’t and hence you compare systematic crap with the failure to comply to maintenance/repair standards.

I’m talking about reality. I’ve never seen a certified plane that was entirely legal and old ones generally have all sorts of non-conforming issues scattered all over the plane. Newly built RVs and the like are in my experience more airworthy and better maintained than many certified aircraft. I’m not personally very interested in the regulatory status of things that could kill me. I’m more interested in finding them and eliminating them and I don’t believe that regulation has a very powerful effect in making that process unnecessary.

I second Silvaire on this one. My 1946 Aeronca was stuffed full of additions. It takes time to go through the plane and ‘sort it out’.

The cable operated drum brakes were a bit crap, so we rebuilt them. A bit better, but still crap. Then during a float/wheel changeover I noticed the outer brake cable sheaths were a bit worn… I pulled out the parts diagram and ordered the correct replacements. Low and behold the replacements had the ‘stops’ built into the cable housing so that they wouldn’t slip. The cables that had been on the plane were generic bowden cables (with no end stops) that were evidently slipping in the mounts, no wonder the brakes went out of adjustment so quick.

I was cutting out a section of longeron for replacement and noticed weld on weld… no note of a previous repair in the book . Measured the wall thickness and it was one size up from the original specification… no wonder the aircraft was having ‘service weight creep’.

I could go on and on, but it was 69 year old airplane that had been owned by a farmer on a remote lake for the last 35 years…

I learned a lot from this airplane (it has been retired) and will always being going through any future airplanes, certified or not, with a fine tooth comb!!!!

Actually, maybe I will just build one :-), at least I will know what is in it! Although I have a lot experience with composites, I would probably build a Vans. Mostly because the have not compromised the low speed handling for the high speed regime. It also seems like they have reached critical mass, with many thousands of airframes flying. That being said, I don’t look forward to the rivet bashing.

My uncle built a Lancair Legacy (he did the important composite work, e.g. spar bonding and fuselage joining at the factory). It is a great airplane and all the pieces seemed pretty high quality. However, he does note that it weighs more than an RV7. Consequently, it seems that the composite design might be a bit conservative and thus heavier than necessary. That being said, he chose the smaller engine (for range) rather than the bigger one. He is very happy with it and it flies very nicely! You typically get 165 knots (TAS) at 10k feet burning 7.5 to 8.0 us gal/hr.

Silvaire wrote:

I’ve never seen a certified plane that was entirely legal …

I am not so sure. In today’s climate where everybody wants to cover himself from liability claims as good as he can, a shop maintained (owner maintenance may be different…) aircraft is almost guaranteed to be legal in all it’s parts. At least in the environments where I fly (GA commercial operation and commercial training). Both companies do their own maintenance (so one could suspect that there was some temptation to cheat in favor of the company) – but in both companies the head of maintenance would never sign off anything that can be traced back to him in case it gets found. And I am pretty sure that the owner of the flying school would not tolerate less than 100% legal parts and repairs on any of his planes. In case of an incident or accident, even a lesser one, this would mean the end of his company.

Peter wrote:

For example, instrument panel illumination lamps on AOC aircraft are known to have an indefinite life and, if they fail,…

… the MEL permits to fly for so and so many days provided the cockpit floodlights are operational and so and so many flashlights are on board.

I am pretty sure that you will not find an airliner – at least not one registered in this part of the world – where someone replaced a fuel line with a lawnmower fuel line or a panel switch with an auto part. Maintenance staff work under pressure and make mistakes and pilots want to be home in the evening just like everybody else, so maybe a minor defect will be written into the tech log on the last sector of the day. But rewiring an electrical panel with wire for model trains? Certainly not.