SteveJeff

Was it an experimental model modified by the owner? As far as I know, 52TW, they are factory-built in Romania at Aerostar, a local reputable company in aircraft design/maintenance.

Flutter at high speed below VNE. During a descent for an airshow at 240 mph.. 240 mph for that airplane seems to be above Vne. I'm sorry, but I would say more pilot fault than airplane fault. Even if it was a modified version, I guess 240 mph would be pretty close to VNE. It is not the first time when at speeds close to VNE happened something to broke. Anyway, I think pilots should be more reluctant to take flight at such speeds especially if there is no possibility to bail out quickly. Just my 2 cent opinion...

I thought about a conventional control system, elevator with trim tab with its separate control, not spring or jackscrew. I practiced a lot of trim + power landings in a Cessna, I would say it's pretty manageable, at least to get you safely on ground, if not even the airplane intact. You have chances to brake the nosewheel, propeller, but at least you won't be fatal injured, I think in such a rare and critical situation, yours and passengers safety is the first thing despite the airplane might be demolished. If hinges are not broken, the only two possibilities I imagine, not sure if likely to happen, just thinking about them, are either the surface vibrates, oscillates (maybe from stop to stop) and eventually, finally jams in an unfair position to recover with the remaining controls or when one componnent from the flight control systems broke, e.g. pulley, pushrod, the break reaction effect might slam the surface in an extreme position, however, don't have enough knowledge about how flt control system componnents are rigged if it would be possible to slam so when it breaks. What do you think?

Watched the webinar. Quite interesting. I found a flt control malfunctions is pretty manageable assuming the control doesn't jam to an extreme. What I wonder if when something breaks, wouldn't it slam the surface to an unfavorable position i.e. towards an extreme, let's say more than a half deflection, and jam there where you don't have enought authority to stop it with the remaining controls? Or due to flapping/fluttering wouldn't it jam to an extreme? Of course not talking about the case when the pilot got a large deflection and the jam occured at that moment jamming the stick in that current position. What do you think?

Also, have a look here at the C172 flight control systems. Page 210-211. There are two cables which run from trim wheel to trim tab pushrod. Only if the pushrod would detach from the tab surface you'll have a freefloating tab which is extremely unlikely cause we can consider it as strong as the tab itself. This kind of fail-safe I was talking about when I referred FAR 23 requirements.

Ok, I read it, quite useful piece, I figure out that it's a very complex subject and I knew that in some particular condition you can encounter flutter even in a normal system without any failure. What I wonder is regarding my first question, about disconnected unbalanced surface. Basically, the question was, are these airplanes with unbalanced surfaces more at risk than the balanced ones in a disconnected situation, considering the airplane didn't have flutter occurences in normal operation and it was also tested for flutter during certification? Also, I would really appreciate to detail a little bit this, if it's not a mistype:

If the spring breaks, I figure out the trim tab remains linked to cable, so it's not freeflaoting or just a little. Even that would be critical to flutter?

Not redundant, I thought that usually being a two cable system and the trim tab is linked in two points to these cables, so if one breaks the other prevents the tab to free-rotate. And about the spring. Have a look at this photo here , zoom on the trim tab and at the bottom of the trim tab you'll see a spring. The cable is atached on the top of trim tab. If the cable fails, I assume the trim tab wouldn't freefloat having that spring there and thus it prevents flutter, or am I missing smth?

The new FA 23.629 is not really so new. I read a document from 1991 and it had those requirements and I didn't have time to search more, but I guess they are much older than that, so I can figure out that they are at least 30 years old. It's true that the mean age from first flight of GA aircrafts may be more (and usually it is) than 30, but in this case I can figure out that most aircrafts have not undergone any changes since they were first certified? Basically all FAR safety improvements changes made over the years does not apply to them? That hurts if it's true. I thought most of FAR 23 aircraft (and all of them must, considering FAR) have two cables for actuating the trim tab (if I remember correctly, Cessna 172 has it), but I may be wrong. Also, I saw some have a spring which (in a cable failure situation) will make the trim tab to stay fixed in position in case of single cable system.

No consideration of a tab disconnect, are you sure? If so, they don't comply FAR 23.629: (f) Freedom from flutter, control reversal and divergence up to VD/MD must be shown as follows: (1) For aeroplanes that meet the criteria of sub-paragraphs (d) (1) to (d) (3) of this paragraph, after the failure, malfunction, or disconnection of any single element in any tab control system. Aileron flutter is more of a concern for low speeds. I'm sorry, it is mistyped or fact? I thought high sppeeds. Read the topic and it reinforces my concerns. Are these airplanes at risk for an inflight breakup due to a control cable failure? Report 45 seems to have a lot to do with mass-balance. I don't think that using it exempts mass-balanced surfaces, on the contrary, it seems that according to it requires that and using it and being mass-balanced makes flutter less of an issue. I don't believe that FAR requires flutter concerns regarding a small trim tab disconnected scenario and won't do that for a primary control surface, but my question is more from a technical point of view, how do they show freedom from flutter if not using mass-balanced surfaces as others have. And regarding LSAs aircrafts, the problem is even more complex considering ASTM standards, unlike FAR, are no very specific on this issue.

I found that many certified LSA aircrafts, unlike most standard certified FAR 23 light aircrafts, don't have mass-balanced surfaces. I'm interested in how they are designed to show freedom from flutter, especially control surface flutter and if these aircrafts can handle a disconnected freefloating surface emergency (due to cable failure, for example). Thank you very much!