"ORIGINAL: David Gladwin

In my view, based on a lifetime of operating jet aircraft, as soon as this incident occurred, there should have been an immediate world wide alert to the problem, requiring an immediate inspection of the stab. structure BEFORE further flight.

ORIGINAL: rhklenke
Geez David, in this country, even the NTSB takes a few days to investigate an accident before delivering recommendations for inspections and such. It could well have been that the owner bumped the elevator against the side of the trailer taking it out, stripped a servo gear, and the resulting flutter in-flight took the stabilizer halves off. What good would an "immediate, world wide alert" (if there is such a thing for models) done if this was the case except panic everyone who owns Lightnings?"


Except this...if he did NOT post it, and then another lightning went in this weekend for the same reason...what then? How would YOU feel if some other people knew all about the problem, and decided not to mention it? Better safe than sorry.



"And no, I have no hidden agenda, just an open one. If we are to secure the future of this branch of RC modelling and do our utmost to avoid a "big black eye" the we have to react to problems such as this, rapidly and with total objectivity. If anyone wishes to describe a serious flight safety issue such as this as "product bashing " then you have totally missed the point, and you have no idea of the culture and practices, built up over many years and with the experience of some very, very hard lessons, which exist in professional aviation, both civil and military. This hobby could , would, do well to follow their example.

Regards,

David Gladwin.

I don't believe you have a hidden agenda, but I do believe that you have somewhat of a different perspective on jet model aviation. Yes, I realize that we could be in trouble as a segment of the hobby if there is a serious accident, and yes want the flying of jets to be taken seriously, but this is a hobby, not "professional aviation" (which by the way, has its own problems - see the "Citation Jet Boat" thread). I think you should drop down just a notch and take into account that these are not commercial full-size aviation products being operated by "professional aviators" (which we all know is no guarantee of safety either)"



Well said. I think you cannot expect really professional behavior from many modellers. Nor even a most basic UNDERSTANDING of what happens. It's very surprising nowadays to see the amount of pilots who essentially see it as a big shiny toy to drive...they do not have even the most rudimentary schoolboy understanding of aerodynamics that is second nature to a guy like you. Like you, I think David's expectations are too high. But I suppose he is correct in that "professionalism" is at least a target to AIM for, try to get as close as we can, even if we never get where we really need to be, somewhere near the level of full-scale.


"and sometimes, "stuff happens.""

Sometimes. And sometimes there is no glue on a spar!


" IMHO, the manufacturer has outlined a probable cause in a timely manner and offered a solution for paying customers, so case closed..."

I have a different perspective. This is a company with a long, sordid track record of being somewhat less than candid, and putting out products that are often somewhat less than well-made. And I took their press release as nothing but some basic glad-handing, foisting off any potential problem as operator error, and offering some scraps of carbon fiber as a palliative. In other words....it smacked of BS! But I have an open mind, I don't know why this lightning crashed, but I would not be surprised in the slightest to hear it was a manufacturing defect.

G.R.
Was that the incidet with the Pitts where the radio suffered iterference on the same frequency and locked out rarther than structural failure. If so how can C-ARF be responsible for that? Or is it one i have missed?

Trevor Skedge.

[/quote]

They weren't, and that was an inappropriate comment. Say what you will about C-Arf, but that's out of line, to blame them for that incident.

As much as I dislike Carf and their business practices, and oftimes shabby construction, and as much as I dislike Sandor, the root cause is most LIKELY(not definitely) flutter. While I find the tailplane spar pictures to be pretty frightening, it's only possible, and not probable, that a stronger spar would have survived a flutter issue.
KEEP IN MIND THIS IS ONLY SPECULATION...before anybody jumps down my throat, I do not KNOW why this tailplane failed, this is pure speculation.
Did anybody hear the classic "brrrraaap!" of flutter before the plane went in?

ET

It would appear, and I say "appear" from the photographs of the stab and remarks posted by Paul Gray that the stab smacking the ground on take off / landing was not the cause of structural failure posited by Comp. ARF, so it "appears" that it could be a manufacturing / design defect.

As expected Comp.ARF have tried to suggest that David Gladwin is commenting in an innapropriate manner. Sometimes David does go in with all guns blazing, but as you correctly suggested, how would he feel if the same thing happened with more serious results and he had not commented. He was there , we were not.

If you asked me who are the safest jet model pilots are my response would be the guys who fly the real thing. They include David, Craig Gottshang and our own Alasdair Sutherland. All current or ex commercial / military pilots with vast experience and to whom check lists are second nature. We would all do well to follow their examples.These guys have technical and aerodynamic knowledge streets ahead of most of us.

John

Well said. My fear, though, is that DG will be dissapointed in the reactions he gets from an awful lot of modellers. The bottom line is, though, that DG is absolutely correct in his attitude about safety, but his aspirations will probably never get completely fulfilled. Still, it's a pinnacle of safety that IS soemthing to aim for.

Using that same caveat "appear"...it would APPEAR that smacking the ground had nothign to do with this...guess Geitz figured if it worked for Bob's Booms, it will work for him...but I do not KNOW....it MIGHT be a manufacturing defect, or it might(I hate to say it, but more likely) be a problem with the elevator linkages and the way they were set up that led to flutter and the demise of the aircraft.

As far as C-arf or their reps having the temerity to say David Gladwin is acting inappropriate, well...let's just say they are throwing stones from a really poorly built fiberglass house that looks all nice and shiny on the outside but is missing glue on most of the ribs and formers hidden inside!
But Bidness is Bidness, I would HARDLY expect them, with their track record, to publicly say "oh, MY BAD, so sorry, want your money back?" For that matter, I would not expect ANYBODY, even BVM, to do that.

I grew up around professional pilots and I can tell you that as a blanket statement, that is simply not true. Those folks you mention have the attributes that they possess because of who they are, not what they do for a living. Professional pilots run the spectrum just like everyone else, from very knowledgeable in technical areas, including aerodynamics, to guys who would have a hard time explaining Bernoli's theroem to you. As far as checklists go, sure, they use them all of the time, but I've met a few who refuse to use any sort of checklist outside of work.

I've read a lot of David's writing and I think he is knowledgeable and I do agree that he has a point. However, I think he went a bit over board in the "immediate world wide alert" area and I definately don't think the hobby can, or should, be held to the same "standards" as it were, as full-size aviation. Its too difficult, too expensive, no fun, and doesn't guarantee 100% safe operations anyway...

That is a very true statement and anyone who thinks differently has their heads burried very deeply somewhere...

I do not agree with some of the things that CARF has done, or been accused of doing, but there are two sides of every story and no one in any of the dealings with them that I've heard about is "untarnished" either. As far as their products go, there are some issues, but I see a lot of guys flying both their jets and props and they are, to a very large percentage, very happy with the product. There are price/performance (or quality) tradeoffs up and down the spectrum and IMHO, CARF has a fairly comfortable point along that line...

Bob

Am I missing something or is the front spar pictured in the layup of the tailplane in post #79 in 3 pieces & joined in the place where the tailplane broke? Does it rely entirely on the skins with the spar just there to 'puff it out'? - John.

Sandor but why both sides?
seems like a unlucky event then?
seen many things fails , and flutter can do a lot of damage.
even if one would not be glued correctly , both at the same time?

I think you are missing the point, it is not a case of just the glue failing.
Is is bad engineering practice to cut/reduce/or otherwise tamper with the load bearing item.

You should not have to 'rely on' the glue.
The load should be carried by the spar with other items 'glued to it'
Unfortunately at the point of maximum load and leverage the spar is weakened by cutting it to fit to the rib.

The glue is on a but joint which is not good.
If you HAVE to join a spar ( or any load bearing structure) you should use an angled slice on both parts to increase the glue area considerable. Usually this is around 30 degrees, from the edge.

I ask you, if you were building the plane and the balsa spare was not long enough, would you Butt joint another piece to it?
I am sure the answer is no.
Now, if i ask you to do that at the fulcrum point where the tail-plane is applying maximum force as it moves up and down and twists! I know the answer would be no.

I sure hope so, as a balsa spar, with big notches cut out of it, with or without fiberglass on the sides of it, sure don't look like it will cut it as a load-carrying member. I ASSUME you are correct, that the skins are the only stressed members....

Again...it could only be a stressed-skin structure, with the spar just there to give it the shape. I doubt even CARF would be insane enough to think a balsa spar would cut it as the load-carrying member.

"I grew up around professional pilots and I can tell you that as a blanket statement, that is simply not true. Those folks you mention have the attributes that they possess because of who they are, not what they do for a living. Professional pilots run the spectrum just like everyone else, from very knowledgeable in technical areas, including aerodynamics, to guys who would have a hard time explaining Bernoli's theroem to you. As far as checklists go, sure, they use them all of the time, but I've met a few who refuse to use any sort of checklist outside of work."

All true, there are exceptions to every rule, there are some really dumb full scale pilots who do some really dumb things. And often die from it. But the basic aspiration to professionalism is the point David Gladwin is making, we don't want to get too far off topic...

"I've read a lot of David's writing and I think he is knowledgeable and I do agree that he has a point. However, I think he went a bit over board in the "immediate world wide alert" area and I definately don't think the hobby can, or should, be held to the same "standards" as it were, as full-size aviation. Its too difficult, too expensive, no fun, and doesn't guarantee 100% safe operations anyway..."

True...but I think the idea of setting the bar high and TRYING to get as close as possible is great.

"But Bidness is Bidness, I would HARDLY expect them, with their track record, to publicly say "oh, MY BAD, so sorry, want your money back?" For that matter, I would not expect ANYBODY, even BVM, to do that.


That is a very true statement and anyone who thinks differently has their heads burried very deeply somewhere..."

You might be unpleasantly surprised at the naievete of some people. They will take C-arfs statement as gospel. The factory says, therefore it must be, end of story. It works on a big percentage of the population.

"I do not agree with some of the things that CARF has done, or been accused of doing, but there are two sides of every story and no one in any of the dealings with them that I've heard about is "untarnished" either. "


This is true. And it's sort of hard to listen to someone complain about their C-arf dealings or products, being that they must know a thing or two about what they are getting into. If you lay down with the devil, sooner or later you are going to have to...well...you know!

"As far as their products go, there are some issues, but I see a lot of guys flying both their jets and props and they are, to a very large percentage, very happy with the product."

I hear you. But I wonder what the percentage REALLY is? I don't care to speculate too much, but I think a lot of Carf planes go down, could be a lot more than you think. Again...pure speculation.


"There are price/performance (or quality) tradeoffs up and down the spectrum and IMHO, CARF has a fairly comfortable point along that line..."

Yes, that's very true, about tradeoffs of price and quality. Carf stuff is a great bargain. EXCEPT to those who had an airplane fall apart. Then it's not such a bargain! But to the nine(or whatever) other guys, it's a very, very good deal. It's a tough call...lots of people flying and enjoying the models, but lots of people crashing them, too, and there is this possibility that David Gladwin rightfully points out...that sometime soon, a really bad accident might happen, and the repercussions might be very bad, and it might be due to faulty construction on one of these models, and at that point, we all might be wishing that we paid a little more for better quality control, and some of these models might not seem like such a great bargain after all. I gather that is at the heart of his posts, and I feel strongly that his intent is nothing but pure.

I've seen plenty of shabby Carf planes. I've only had a cursory look at an unbuilt Lightning, seemed like QC was better than usual, but that does not mean a thing. As far as I am concerned, the jury is still out on what happened to poor Robrow's plane, I'd hardly accept Carf's explanation(user error!) as definitive, but nor would I immediately blame a manufacturing defect.

Bob
[/quote]"

I'm sure we all have mod ideas, but here's what I've been thinking...

There is limited access thru the servo panel, but it does seem possible to put about an 18" carbon cloth strip inside on the bottom skin that runs under the servos. It would not be easy to prep & insert, but I think it would help. The servo arm slots are what weakens the skin. Definitely need carbon in that area like Comp-Arf's mod kit is supposed to have.
It's also possible to laminate carbon cloth inside the upper skin & servo hatch.

You can't really laminate anything to the front of the spar because the servo mount is in the way. I suppose you could grind out the mount out in order to put a continuous carbon piece on the spar then reinstall the servo mounts.

Or we could easily laminate carbon strips on top the spar to the skin exterior like the early kingcat booms.

I'd assume if this is a widespread problem Comp-Arf will fix in later production. (just like they did on the latest Eurosport & kingcat booms)

Now I hope this thread will just stick to the fix, instead of all the other b.s.

...Scott

I find it hard to believe that with all the Lightnings out there flying and only 1 issue that there is a design problem. You guys are looking at the crash photos, did you not notice that there is a servo screw missing and I could be wrong here but it looks like a plastic servo arm in the photo. Come on, you don't build a $10K airplane and not use all the parts or use cheep parts and then say it a poor design when it breaks. I sure would hate to see CARF's rep hurt if they are not at fault, I for one can't afford to buy a $20K UB. I love my Lightning and will want another one when I wear this one out.

You might be right, in that there is no design problem. Remains to be seen.
Can't help but notice that both the servo and the plastic servo arm are both still in place, so I don't think THAT was it...

The servo screw was not missing, the photo was taken part way through dissasembly and removal of the servos for Andreas to inspect the whole stab assembly.

The servo arms are OEM heavy duty rigid glass filled nylon as supplied with these high torque digitals and are more than up to the job. They are impossible to bend by hand and stronger than the dual phenolic control surface horns and 3mm brass reinforced pushrods via which they move the respective control surfaces.

Hope that helps explain the picture more clearly.

Rob.

Sir
The fact that this is bad design practice is not questionable in my opinion. Ask ANY mechanical design engineer and he will tell you the same.
Also please note, the fact that others have not failed at this time also does not mean that this is not bad practice.
History is littered with issues where bad design practice has survived for many years, the issue is, how close to the edge do you want to be?
Aircraft (full size) are built to exacting standards and each item is designed with a large factor of safety, that is the best us mortals can hope to do.
This however does not stop failures occurring and full sized planes crashing due to miscalculations or lack of forethought in design.
What you will NOT find in full size is a design feature breaking what are fundamental basic mechanical design laws.

What i say here should not be taken wrong.
I have no issue with CARF, I very much like the Lightning and the Flash and what CARF have done to lower prices and deliver product worldwide.


Dave Wiltshire is in my club and flys the Lightning and Flash regularly, he is a great pilot and the planes perform admirably.
This fact however does not distract me from my above concerns and the facts as they exist.
As i said before, i am sure CARF will take all actions necessary to correct any issues they feel exist.

"The fact that this is bad design practice is not questionable in my opinion. Ask ANY mechanical design engineer and he will tell you the same."

Me, I can't STAND C-arf and their ways, but I still have to disagree with the statement above. If the structure was designed as a stressed skin deal, I supposed the spar material is irrelevant, all it needs to do is keep the skins apart at the proper distance.
Now...if that spar is actually supposed to be load bearing, now...that would be pretty frightening...

This stab, it has anhedral, or it's flat?

anhedral

Not sure how a stressed skin structure would work in that situation, without a really heavy spar in the middle...

It would not work.
Any stressed skin needs a method of transporting load to a strong point.
You can not just have a 'stressed skin'.
The stressed skin acts to keep the load bearing spar (Or members) upright and in position.
If you just had a stressed skin with no load bearing spars the top ( or bottom skin) has no support, it creases and the strength has gone....the end of the structure! Something HAS to take the load and transport it..

Let me guess. A big lump of plywood without joins and cut to suit the anhedral will mysteriously be introduced as part of CARF's 'policy of continual product and design improvement'. And, of course, every existing owner will be offered the new improved tailplane free of charge as part of a voluntary product recall just as RESPONSIBLE companies do when they sell you a dangerous product. And, of course, the poor guy who spread his $10K jet over the runway will be compensated for his loss and be all happy again. Oh yea! [sm=lol.gif]

Issues? Is the issue a dangerous model which may injure people (or worse)? Or is the issue 'sheet, our product is on the nose & no one is buying them so we are not going to make any money'. - John.

Just got back to London from Jet Power, a truly, truly, fabulous event, best meeting I have ever been to, the real "Farnborough" of model jets. Winnie did a truly outstanding job.

Of course I got the cold shoulder from C-ARF but everyone else who raised the Lightning issue was VERY supportive. I have many e-mails waiting and all will be replied to but PLEASE be patient as I am returning to Sydney next Tuesday and lots of last minute things to do. My sincerest thanks to all who gave so much of their time to discuss their products with me, RCJI will cover them in due course.

Hot tip : New Airworld kit could well be a large BAC Lightning F3a/6. One was flown by Tommy Gleissner, in 92 Sqn markings and later appeared adjacent to the Airworld stand ! More later.

Regards,

David Gladwin.

Its C-ARF, BVM, Airworld.....OK

Was there this much panic on BVM's web site when tail's were falling off King Cats? Why did they figure the skin would take the full load of the whole tail? I know there was no reinforcement structure inside. Don’t try to tell me it was CARF’s fault, it was not their design!! I don’t believe for a minute that the stab broke from normal use, something tells me there’s more to the story then we are being told. If you want to try to compare this to full scale, if you were landing a full-scale plane and hit a wing on the ground, would you go and fly it again with out proper inspection and repair? Do you think that if you had large cracks in you wing panels that the internal structure alone will hold the wing together? I don’t thing so.