skyfox wings 21 through 25N

[barandbrew]

T

 

John: Remember, this is a flexible wing. The original ailerons before certification were one piece. When loaded in flight, the wing bends enough such that the original one-piece ailerons jammed solid. That's what Llewellyn was testing. That's why the ailerons are now segmented. The wings still bend in flight and so does the full length of aileron. Play when the wing is unloaded on the ground does not necessarily mean play in flight. I suspect that you need some degree of clearance in those bushes to prevent binding in flight. So long as the bushes are still in one piece, I don't think I would worry about it, unless the aileron as a whole rattles around. The wings can flex inches in flight. I think the one bush you should pay attention to is the one that constrains the torque tube where it emerges from the fuselage/turtle deck, based on the experience of my friend Tony Curzon who once suffered aileron flutter. I'm not an expert in this matter. Few people are. Llewellyn is.Carl

Thanks Carl

Yes the plastic bushes are all in one piece it looks like wear to me however I am not sure what is acceptable . The airframe has 1790hrs not a real lot compared to other Gazelles so I may not have a problem however I would like to know for sure.( GA LAME has done a airframe check last year however I was not in attendance to point out my concern)

 

John

 

 

[carlsnilsson]

GA LAME has done a airframe check last year however I was not in attendance to point out my concern

John:

I'd be surprised if anyone could answer your question authoritatively. There has not been any AD or AN re wear on these bushes, to the best of my knowledge. Certainly a number of Foxes have done lots more hours - some up around the 5000 hour mark, I believe. There are probably quite a few which have done 3999.9 hours! However, I would use my own judgement, based on the following:- firstly, can you rattle the whole aileron on the ground inside those bushes? Flutter would probably be more easily induced by a change of aileron angle of attack rather than a minute wobbling of position. (I'm speculating, but this would be my thinking). Flutter is an oscillation, so you have to have at least two opposing forces. When an aileron is out of balance, the moment of inertia changes (probably increases). Flutter occurs when wing/aileron distortion (i.e. elasticity of the system, which may have several components) opposes the air pressure distribution which is distorting the system. In addition, some important part of the wing/aileron structure needs to have a resonant frequency in tune with, say, the fluctuating control surface. "Out-of-balance" for the ailerons is an important factor because it effects the moment of inertia which determines the natural frequency. If you ever felt a vibration of the ailerons that came and went, for example, that would be a warning sign not to be ignored.

 

Now, Daffyd Llewellyn, when testing, found that he could sometimes induce flutter in the Fox ailerons (I can't remember whether they were one piece or segmented, but I can check) at speeds as low as 65 kn IAS by giving the stick a sideways rabbit punch. If you are worried about your ailerons, try that! Try it first at low speed, say 60 kn with a very modest sideways knock. If nothing results, increase the force of the sideways knock a little. A small step at a time is the watch phrase of a test pilot! On one occasion instructor Tony Curzon discovered that he could induce some modest flutter at cruising IAS in a friend's Fox and immediately reduced speed (the correct thing to do) and promptly landed. The torque tube bushes through the fuselage were pretty loose so they did something about that and the effect went away, so I am told. I have given my stick the sideways knock test at 70 kn with no effect. That's good enough for me. "If it ain't broke, don't fix it" might be applicable here with regard to the hanger bushes. The point about the sideways knock is that it generates a sudden force. That is, the suddenness - the short rise time - incites a range of frequencies, unlike a gradual push. The range of frequencies might be enough to excite some resonance in the system. That would be a warning and that, I think, would be what an aeronautical engineer might suggest in order to answer your question.

 

Regards Carl

 

 

[foxworker]

Thanks PaulYes the plastic bushes round the aileron tube it is only slight play but I would like to take it out if possible. I can see no way of doing this apart from taking the whole aileron apart.

Thanks John

Hi Barandbrew,

 

As Carl has stated there have been no proceedures set down for measuring excess play in the bushes in question, certainly none that I am aware of; it hasn't been an issue before. I am currently disscussing this with an ex. Skyfox employee who made the actual 4130 brackets and we are trying to come up with a solution for replacing the bushes if it is indeed possible. I believe tomorrow evening I will be able to give you some usefull info. Thanks again,paul.

 

 

[Blueadventures]

G’day Mike:Good luck to you learning on a CA21. I don’t know if you have previous experience with taildraggers, but learning on a CA21 is not the easiest way. I had a few hours solo on a Piper Cub back in 1968, but when I started again on a CA22 in 1996 at Penfield, Vic., I was classed as a slow learner. I had difficulty, to say the least, in landing! Eventually circumstances caused me to transfer to a Drifter on which I made better progress and eventually, much poorer in pocket, I got my certificate! I then hotfooted up to Caloundra and bought a much-used, much loved and sometimes-abused CA22, namely 55-747, which my friend Tony Curzon (instructor) and I flew back to Penfield. At the time, I was not aware of some of 747’s chequered history, but I have to say that I kept that aircraft on line at Penfield for many years and it never gave any significant trouble and helped a lot of students get their certificate. Since then I have bought two others and sold one, keeping 55-0688 for my own use sinceY2000. I could converse at some length on the joys and pitfalls of learning on a Fox, but maybe not on this thread.

In my opinion, wooden or aluminium hangers is not too much of an issue with respect to Fox wings. Get hold of Skyfox Aviation’s Service Bulletin No. 24 or the equivalent issued by the (then) AUF – now RA-Aus. There was an AD or similar issued by CASA on the subject, as there were a number of VH-registered CA-22’s, not to mention all the Gazelles. Basically, SB 24 gives some guidelines on examining wooden hangers. As best you can, look for any signs of wood rot. You can’t really examine them properly unless you remove fabric. What you can and should do, is make sure every wing bay has a decent (>4 mm say) and clear drain hole close to a rib and as near to the trailing edge as possible. Ailerons should also have drain holes in each segment near the trailing edge. Also, there was an AN and AD (Airworthiness Notice and Airworthiness Directive) regarding the removal of the outermost bit of the outboard aileron (outside the last hanger). The aim was to prevent water ingress – which can also be achieved by application of a suitable filler material through the slot for the hanger bracket. Use your common sense – you are acting to prevent water getting into the aileron segments and providing a means of letting any water out.

 

Wood rot takes place when moisture is present around unsealed wood and there is lack of air circulation. Water inside wings is a pretty good starter for the fungus. That’s why foxworker stressed the sealing of all wood surfaces. Unfortunately, on some early wings (CA21 and CA22), some epoxy joints were not made with proper attention to smoothing out fillets with a sufficient amount of epoxy and blending to the wood , particularly around the trailing edges where they attach to the ribs. Any cavity, be it in your teeth or an epoxy joint to a rib inside the Skyfox wing, provides a nucleous for rot. This could well apply to the attachment of aluminium hangers to the wooden ribs, just as to the wooden ones.

 

Foxworker would advise you to take a look at your trailing edges. Are they even where they join each rib – that is, does one side sit higher than the other? Feel them between thumb and forefinger. If one is loose and co-joins a hanger, you have a potential site for water penetration. You seem to be doing this OK. Don't get too obsessed with this matter. If you read the ATSB report of the NT accident (No. 199800361) you will see that the rot was widespread and advanced and should have been very detectable.

 

It helps a lot if the aircraft is hangared (I’m spelling it correctly this time!) – a Fox is not a machine which should be left outside in the elements for months at a time. This is not to imply that it has to be cosseted and is particularly fragile – but a machine of wood and fabric is not designed for prolonged outdoor storage in the tropics.

 

To me, these are the issues that warrant attention – more than the question of wood vs aluminium hangers. The other matter to arise from the two occasions of which I am aware a hanger has broken in flight is the question of ensuring the ailerons are balanced – that is, the C of G of the ailerons has not moved aft either due to a weight coming loose or water ingress and retention. There is an AN on this and you have to remove the ailerons (not a big job) to check. As I said, if you get severe aileron flutter due to unbalanced or insufficiently supported ailerons, things will quickly tear apart regardless of whether the hangers are aluminium or wood. I would prefer the guilty aileron to depart swiftly from snapped hangers and broken aluminium torque tube and good luck to all who sail in her! I would watch it flutter to the ground as I flew home with one good aileron! But it won’t happen to me!!

 

Now you have me going on this forum, I want to write something about the behavior of the wing in turbulence – the easy guide to Daffyd Llewellyn’s enlightened report. Give me a couple of days.

 

Regards Carl

Hi Carl

 

Thanks for the detailed information. I will review my method of checking and give more attention to the trailing edge areas. They are good and sound; but will contine with checks. I had read all the available info re the couple of incidents. It is a slow conversion from gliding but I'm on my way.

 

At present I have the aircraft at home and presently fitting the clear bottom halfs to the door panels. At present the lower half of each door is painted blue and this restricts available vision that may be handy at times.

 

Other wise I'm enjoying the flying.

 

In a couple of weeks I will be back into flying full time. And a few of us are building a hanger, site prepared today and the profiles will be set up soon, the metal is on site and we'll have to place some fill first only need to raise ground 100mm on top of about 80mm ground uneveness. Busy times but the end result will be a hanger for 4 and later 6 ultralights. (xair, drifter, thruster and the skyfox) so should be plenty of opportunity to local fly and visits xcountry before the next rain season.

 

Look forward to staying in touch. I give you a call sometime and exchange skyfox experiences.

 

Cheers

 

Mike

 

 

[Blueadventures]

Hi Blueadventures, good to hear from you. You can contact me on mobile 0402871771. Often I don't hear my phone during work hours due to the noise where I work, so please leave me an sms message with a contact number and I will call you back as soon as I am able. Look forward to talking 'fox wings. chers paul

Hi Paul

Do you have any details about the paint type/proceedure that is used. The Ca21 I have was first built as 0606 and in 1994 she underwent a major rebuild and was reasigned 0637. Painted in metallic blue with the leading edge and front of cowl being yellow. I'm just gathering info as i'll repaint some of the top engine cowl (Metallic Blue) where an air scoop was fitted and then removed (must have been years ago). The inserted panel needs a tidy up and then I'll repaint the area. I was told it looks like a two pack epoxy finish.

 

Regards Mike

 

 

[Mike S]

If I can be of any assistance to anyone with respect to skyfox wings, repairs, rebuilding etc. feel free to ask me any questions. I built pretty much all of the Gazelle wings, updated and re-wrote the specs. for them, and know them inside out. Also have access to the covering process and the fellow who did the covering in the factory. Repairing 'fox wings including hangar brackets, trailing edge sections, epoxy joints, drag braces etc. isn't rocket science however if you're going to do it yourself and you're not an L2, you need the correct info. and the correct proceedures on how to go about it. I've read some pretty disturbing comments written by people fixing their wings obviously not really knowing what they're doing. I am happy to help anyone who is prepared to listen and do it properly. cheers.

Hi 'Foxworker' - I've just started looking at a CA25 TG that has been 'flipped' - tripped while on the brakes. There is not a great deal of damage - left wing has had all the aileron hangers snapped [ ailerons appear undamaged ] off and wing struts ruptured- at this point I can't determine if there is more damage to the wing or fuse although - I've got my suspicions. There's little damage to the tail so I think the flip was gentle. - from other threads here it seems the impact damage is genuine - I couldn't see how the hangers would break from such an impact but obviously they can be it would seem - and the same with the struts - it would seem the repair is fairly straightforward from yours and others comments? Right or not? [Assuming theres no other damage?] I'm still collecting info.about the 'Foxes' so I'm finding this particular thread interesting - thanks for starting it off!

 

Thanks ,

 

Mike.

 

 

[carlsnilsson]

Hi 'Foxworker' - I've just started looking at a CA25 TG that has been 'flipped' - tripped while on the brakes.

G'day Mike:

Either my brain (?) has gone to sleep or I'm not familiar with the "TG" in CA25TG. I presume that's a taildragger CA25 -yes? If all the aileron hangars snapped and the wing struts ruptured, it would seem that the left wing took a pretty severe impact. Did the fabric tear above the fuel tank in the bay nearest the fuselage - that would indicate a fair amount of shear on the wing which may have bent the spars - or at least the front spar. Also, take a look at the wing attachment points.

 

On the other hand, I have a friend with a Fox that hit power lines on final approach and nose-dived into the ground. He and his wings were undamaged, although the fuselage needed some repair. It flies beautifully today.

 

Carl

 

 

[Mike S]

G'day Mike:Either my brain (?) has gone to sleep or I'm not familiar with the "TG" in CA25TG. I presume that's a taildragger CA25 -yes? If all the aileron hangars snapped and the wing struts ruptured, it would seem that the left wing took a pretty severe impact. Did the fabric tear above the fuel tank in the bay nearest the fuselage - that would indicate a fair amount of shear on the wing which may have bent the spars - or at least the front spar. Also, take a look at the wing attachment points.

On the other hand, I have a friend with a Fox that hit power lines on final approach and nose-dived into the ground. He and his wings were undamaged, although the fuselage needed some repair. It flies beautifully today.

 

Carl

Hi Carl,The 'TG' tag is mine - I know the taildraggers were just plain CA25! I've got too used to a number of people not realising this so I've added the TG.

 

There's no tears near the tank - the only one is in the underside near the spar attachment point where I think the spar bent & went through the fabric. - apart from the spars & the broken hangers the tear is the only other sign of damage on the wing. I will check the wing attachment points.

 

There is one other issue for me and that is that one of the frame tubes - the one from the upper corner of the left windscreen/ front wing attachment point and runs diagoally down to the centre of the screen is bent slightly in toward the pilot.

 

There is no apparent damage to the windscreen - no impact point that I can see and when I pointed it out to the owner he commented that he'd never seen it before and was trying to work out how it got bent like it did. Its about 20mm off straight in the middle of the run. I thought maybee the upper front wing attachment point had moved but I'd have thought there'd be some cracked paint or something to indciate stress but I can't see any - I'm yet to check the bottom attachment point at the base of the screen. Any ideas?

 

Thanks,

 

Mike.

 

 

[carlsnilsson]

There's no tears near the tank - the only one is in the underside near the spar attachment point where I think the spar bent & went through the fabric. - apart from the spars & the broken hangers the tear is the only other sign of damage on the wing. I will check the wing attachment points.There is one other issue for me and that is that one of the frame tubes - the one from the upper corner of the left windscreen/ front wing attachment point and runs diagoally down to the centre of the screen is bent slightly in toward the pilot.

Firstly, it takes a pretty good crack to bend that spar. When I pushed mine (backwards) through hitting a tree, the shear force tore the mounting of an internal diagonal drag brace and showed that shear by tearing the fabric above the fuel tank. The innermost bay with the tank has no drag brace and hence can be more easily distorted in shear

- the tank taking some of the distortion. My front wing mount bracket (the short vertical tube into which the clevis pin goes) was also bent, as was the pin itself. I managed to straighten the bracket tube, after checking that the weld was not damaged, although I spent a couple of days doing it rather carefully. In your case, it rather sounds as if the frame tube took up the distortion. If it is not kinked, then it likely could be straightened.

 

As for the spar, all may not be lost. If you decide to go ahead with repair, get into contact with foxworker. He has some good contacts in prime Fox country (SE Queensland).

 

Regards Carl

 

 

[djpacro]

On one occasion instructor Tony Curzon discovered that he could induce some modest flutter at cruising IAS in a friend's Fox and immediately reduced speed (the correct thing to do) and promptly landed.

Most people expect flutter to appear first at high speeds so being wary of Vne is good however aileron flutter in the mid-speed range is fairly typical of structural configurations like this.(I've redesigned ailerons on a number of aircraft types)

Good to have this forum so that the maintenance tolerances that you guys have been discussing can be sorted out on the ground. If you think that there is a chance of even "moderate flutter" and you are going looking for it perhaps consider all the risks and mitigating actions eg a parachute.

 

 

[carlsnilsson]

If you think that there is a chance of even "moderate flutter" and you are going looking for it perhaps consider all the risks and mitigating actions eg a parachute.

.That's good advice. You can get pretty compact emergency parachutes that open smartly. Glider pilots sometimes have them. Use as a cushion - either for the back or the bum.

Carl

 

 

[foxworker]

Hi PaulDo you have any details about the paint type/proceedure that is used. The Ca21 I have was first built as 0606 and in 1994 she underwent a major rebuild and was reasigned 0637. Painted in metallic blue with the leading edge and front of cowl being yellow. I'm just gathering info as i'll repaint some of the top engine cowl (Metallic Blue) where an air scoop was fitted and then removed (must have been years ago). The inserted panel needs a tidy up and then I'll repaint the area. I was told it looks like a two pack epoxy finish.

 

Regards Mike

Hi Blueadventures, thanks for your question. Now, I do know that all of the CA25N Gazelles were painted in Dulux 2 pak polyurethne and a couple were painted with Dulux clear over basecoat. The fibreglass cowls, spats, tips had a 2 pak epoxy hi fill primer and were finished with the Dulux 2-pak. If I had the job of re painting a cowl etc. I would be removing all the top coat down to the undercoat, and if it were metallic or mica, I would be going 2-pak clear over base. The 2-pak polyurethane used on the Gazelles where it was metallic blue was called "Magnatite Blue". I'm not sure what is on your cowl, I'd be rather surprised if it were 2-pak epoxy. I find it always a hec of alot easier to respray the whole item. I hope this has been helpfull.

 

 

[foxworker]

Hi 'Foxworker' - I've just started looking at a CA25 TG that has been 'flipped' - tripped while on the brakes. There is not a great deal of damage - left wing has had all the aileron hangers snapped [ ailerons appear undamaged ] off and wing struts ruptured- at this point I can't determine if there is more damage to the wing or fuse although - I've got my suspicions. There's little damage to the tail so I think the flip was gentle. - from other threads here it seems the impact damage is genuine - I couldn't see how the hangers would break from such an impact but obviously they can be it would seem - and the same with the struts - it would seem the repair is fairly straightforward from yours and others comments? Right or not? [Assuming theres no other damage?] I'm still collecting info.about the 'Foxes' so I'm finding this particular thread interesting - thanks for starting it off!Thanks ,

Mike.

Dear Mike, thanks for the question. I recall when I was talking to Carl about repairing his wing before he made the decision to bring it up to me, that after many conversations on the phone his repair seamed pretty straight forward. It wasn't until the fabric was removed that the whole picture began to un-fold. My point being that what at first appears to be straight forward can very well turn out to be quite substantial when you actually see the structure. Okay, now to try and answer your question. I have stated before that it is not rocket science to re-build or repair 'fox wings, but in saying that I have built almost 70 sets. You do need pretty specific skills and knowledge to properly repair these wings, I'm pretty sure Carl will back me up on that point. If you don't have a very good eye/attention for detail, and if you are not great with your hand skills, you're probably going to get quite frustrated and possibly make mistakes. If on the other hand you are used to using all sorts of hand tools, including air, if you can make cuts in materials to very fine tolerances, if you can remove materials very carefully without damaging substrates, if you can form epoxy/cotton flox glue joints very cleanly and neatly and you are able to build jigs and templates, you've got a good chance of repairing your wings to the same standards that they were built to ie. SA-10. One of the best "students " I ever had the pleasure of teaching the art of 'fox wing building was a retired vetinary micro-surgeon. In saying that, 1000's of people have built Kitfox wings successfully. I've also stated before that I've read of people attempting to repair their 'fox wings when clearly they didn't have the skills or expertise needed, which I think is a bit of a worry especially if they intended to sell their 'fox down the road. I think you need to ask yourself this question; would you be happy to sell your aircraft with wing work that you had carried out yourself to, say, a casa inspector who told you he would be re-fabricing the wings if he were to buy it? You'd want to be real sure you did a spot on job. I remember at one stage Skyfox decided it would be a great idea to have Sir Joe Bjelki-Peterson as their ambassador to help boost sales, (unfortunately had no effect what so ever), and on meeting ol' Joe, he said to me "wing building-that's an art within itself". He was correct and you need to look at it that way to some extent. I do hope I've shed a bit of light on the practise of Skyfox wing building/repairing as it really is not for everybody. Mike, is the fox your talking about white with blue stripe rego. 24- 40**. If not disregard this question. I f you want to talk more you can contact me on 0402871771. Leave a message if I don't answer. cheers paul

 

 

[foxworker]

Hi Barandbrew,As Carl has stated there have been no proceedures set down for measuring excess play in the bushes in question, certainly none that I am aware of; it hasn't been an issue before. I am currently disscussing this with an ex. Skyfox employee who made the actual 4130 brackets and we are trying to come up with a solution for replacing the bushes if it is indeed possible. I believe tomorrow evening I will be able to give you some usefull info. Thanks again,paul.

After further investigation it appears as though it is not possible to replace the bushes. Removal and replacment of these bushes was not considered when producing the ailerons. If someone has come up with a solution that is practical and of an acceptable standard, I would surely like to know.cheers paul

 

 

[barandbrew]

T

 

Hi Barandbrew,As Carl has stated there have been no proceedures set down for measuring excess play in the bushes in question, certainly none that I am aware of; it hasn't been an issue before. I am currently disscussing this with an ex. Skyfox employee who made the actual 4130 brackets and we are trying to come up with a solution for replacing the bushes if it is indeed possible. I believe tomorrow evening I will be able to give you some usefull info. Thanks again,paul.

Thanks Carl and Paul

This has been a very informative thread with advice given by experts with this aircraft It is very much appreciated by myself and others I am sure

 

Thanks again

 

John

 

 

[foxworker]

Hi Blueadventures, thanks for your question. Now, I do know that all of the CA25N Gazelles were painted in Dulux 2 pak polyurethne and a couple were painted with Dulux clear over basecoat. The fibreglass cowls, spats, tips had a 2 pak epoxy hi fill primer and were finished with the Dulux 2-pak. If I had the job of re painting a cowl etc. I would be removing all the top coat down to the undercoat, and if it were metallic or mica, I would be going 2-pak clear over base. The 2-pak polyurethane used on the Gazelles where it was metallic blue was called "Magnatite Blue". I'm not sure what is on your cowl, I'd be rather surprised if it were 2-pak epoxy. I find it always a hec of alot easier to respray the whole item. I hope this has been helpfull.

Apologies, from memory I think it was "Dulon" and not Dulux. cheers paul

 

 

[carlsnilsson]

Guys my question might have got overlooked in the flurries of posts' date=' the skyfox forum has never been as busy, so does anyone have any clues as to the flutter I've heard they can exhibit! [/quote']Not much of a clue, actually, except that the incidence seems to have gotten a bit exaggerated. Flutter has been implied as a possible cause of two incidents of hanger breakage, so far as I'm aware - and been reported by Tony Curzon in mild form on one Fox. One case of hanger breakage (in NT) was with rotten hangers. The other in Qld, as best I recall, also had some incidence of rot in the hangers, but I would have to check that report. The case with pilot and Tony Curzon was mild, I am told, resulted in no breakage of anything, and did not repeat itself after the fuselage bush was maintained/replaced. Only the NT hanger breakage resulted in a crash.

From what I recall of what Daffyd Llewellyn wrote, the flutter he observed during testing was caused by feedback between the wing structure and aerodynamic forces from movement of the ailerons. This seems to be made worse by out-of-balance ailerons. That was his advice resulting from the incident (departure of an aileron) in Qld. The lesson is pretty clear - periodically check the balance of the ailerons - particularly note any rattle due to a loose weight when you move them up and down sharply and make sure that they are adequately drained and water does not have a ready ingress - and you'll be OK. I have never experienced flutter myself. Visitors - got to go - will continue later.

 

Carl

[foxworker]

:thumb_up:

 

Hi Paul,Answer to which 'fox' -its not the one you've mentioned.

Thanks for the advice re the work standard - I would certainly seek 'professional ' advice in regard to any repairs I carried out - my son-in-law is a LAME and I'd talked to him about refabricating the struts to cert standards and signing off on them - he has pretty high standards so I have no concerns about that and has tickets for fuselage repairs! In regard to wing repairs - yes, I agree - I build wooden boats and use handtools in wood construction and also repair & rebuild cars & motorbikes but I'd probably get someone else to actually do the work for the exact reasons you have outlined and to ensure the aircraft retained its certification status!

 

The fuselage damage that has caused the cockpit tube to bend is probably also repairable - but again I'd get someone else to do that after I'd prepared the areas - I'd also like to know exactly what caused it if it wasn't the impact from the flip - which I'm starting to think is as has been suggested and is deformation from somewhere else - possibly the front mounting point for the wing - from memory the mounting pin was not deformed though & I'd have thought it would have been - will have to have a closer look at it next time I see it - I guess at this point in time I'm just trying to work out the extent of the repairs needed before committing myself to a purchase I may well regret a little down the track - been there done that before - so I'm a bit 'once bitten' !

 

Thanks for the contact number and I will definitely look you up once I have another look at it ! Unfortunately that was to happen this weekend but life intervened and I couldn't get to it. The problem for me is that its 300klms from wheer I live - be in touch again but not for a few weeks!

 

Thanks, Mike.

Good stuff Mike. Just so happens that I have email pictures of a 'dragger that appears to have almost identical damage including the bent diagonal tube, bent towards the pilot roughly 20 mil or so. A friend of mine "may" be able to answer your question on why the bend happened; he built all the fuses. When you're ready, give me a call as I know someone who can probably supply strut material etc. for your repairs,(he is also approved to build new struts as well if need be), and "possibly" a spar if you require one. Also new hanger material. I would suggest you get an idea of all the costs and time involved in the repairs neccessary and take that off the average price for such a Fox in cosideration of the time left on the engine etc. etc.cheers paul

 

 

[carlsnilsson]

hey guys I have always wondered why the skyfox had the issue with aileron flutter but I've never heard of it on the kitfox or the avid' date=' I check out the kitfox forum at times and you never hear of them having a problem ,even with much higher VNE, any explanations? [/quote']

give me a call as I know someone who can probably supply strut material etc. for your repairs' date='(he is also approved to build new struts as well if need be), and "possibly" a spar if you require one [/quote']To continue on the question of flutter on 'foxes but not on Avids or Kitfoxes: I'm trying to remember, but I think the Kitfoxes have flaperons? Can't see that that would help. Also, the Kitfox spars do have an inserted vertical web, but I doubt that would resist bending as well as the integral web on the fox spars. In general, I do not think that the Kitfoxes were as sturdily built as the CA22's. For example, the CA22's sometime after serial 22010 but well before 22027 has 5/8 inch moly (4130) longerons, whereas the earlier ones and the CA21 had 1/2 inch tubes. I suspect (but don't know) that the Kitfoxes of that period only used 1/2 inch also.

Perhaps someone can enlighten me on the Vne for the Kitfox? I see no reason offhand why it should be greater than that for the CA22 (93 kn). That Vne is conservative, in line with proper practice. I can admit to (quite foolishly) exceeding Vne on the dial on a few occasions and having nothing bad happen. So Tony Curzon's report of mild flutter or at least vibration on one occasion and the suspected flutter as cause of the Qld incident are about the only two occasions that flutter has been raised as (possibly) occuring on production model foxes. I am discounting the accident in the NT as that was most likely caused simply by a rotten hanger snapping under load. The report (no. 199800361 for Skyfox CA21017) does not even refer to flutter. So in fact there are no confirmed cases of serious aileron flutter in any production 'fox of which I am aware. There is no real "issue with aileron flutter on Skyfoxes compared with Avid Flyers or Kitfoxes". That's a furphy. We have been taking about possibilities and precautions and, by and large, these apply to many recreational aircraft.

 

I have refered to foxworker's comment about building new struts. If I were putting a new strut on my 'fox I would incorporate a modification suggested by Daffyd Llewellyn - who, as a Reg. 35 engineer, can properly sign it off on a certified aircraft. I will refer to it more fully in another post on the behaviour of these wings in turbulence.

 

regards Carl

[Mike S]

Hi Paul,Answer to which 'fox' -its not the one you've mentioned.

Thanks for the advice re the work standard - I would certainly seek 'professional ' advice in regard to any repairs I carried out - my son-in-law is a LAME and I'd talked to him about refabricating the struts to cert standards and signing off on them - he has pretty high standards so I have no concerns about that and has tickets for fuselage repairs! In regard to wing repairs - yes, I agree - I build wooden boats and use handtools in wood construction and also repair & rebuild cars & motorbikes but I'd probably get someone else to actually do the work for the exact reasons you have outlined and to ensure the aircraft retained its certification status!

 

The fuselage damage that has caused the cockpit tube to bend is probably also repairable - but again I'd get someone else to do that after I'd prepared the areas - I'd also like to know exactly what caused it if it wasn't the impact from the flip - which I'm starting to think is as has been suggested and is deformation from somewhere else - possibly the front mounting point for the wing - from memory the mounting pin was not deformed though & I'd have thought it would have been - will have to have a closer look at it next time I see it - I guess at this point in time I'm just trying to work out the extent of the repairs needed before committing myself to a purchase I may well regret a little down the track - been there done that before - so I'm a bit 'once bitten' !

 

Thanks for the contact number and I will definitely look you up once I have another look at it ! Unfortunately that was to happen this weekend but life intervened and I couldn't get to it. The problem for me is that its 300klms from wheer I live - be in touch again but not for a few weeks!

 

Thanks, Mike.

 

:thumb_up:Good stuff Mike. Just so happens that I have email pictures of a 'dragger that appears to have almost identical damage including the bent diagonal tube, bent towards the pilot roughly 20 mil or so. A friend of mine "may" be able to answ What a dope!

 

your question on why the bend happened; he built all the fuses. When you're ready, give me a call as I know someone who can probably supply strut material etc. for your repairs,(he is also approved to build new struts as well if need be), and "possibly" a spar if you require one. Also new hanger material. I would suggest you get an idea of all the costs and time involved in the repairs neccessary and take that off the average price for such a Fox in cosideration of the time left on the engine etc. etc.cheers paul

Hi Paul,

 

I think I must be on an other planet! The number I looked at was the serial number!!!

 

Yes, I think its probably the same one - I'll be in touch!

 

Mike.

 

 

[carlsnilsson]

Guys my question might have got overlooked in the flurries of posts' date=' the skyfox forum has never been as busy, so does anyone have any clues as to the flutter I've heard they can exhibit! [/quote']

There is no real "issue with aileron flutter on Skyfoxes compared with Avid Flyers or Kitfoxes". That's a furphy. We have been taking about possibilities and precautions and' date=' by and large, these apply to many recreational aircraft. [/quote']Just to finish up my comment on the fact that there is no particular issue re flutter, providing the ailerons are kept adequately in balance, I have dug out some correspondence I had with Daffyd Llewellyn (the testing Reg. 35) in Dec. 2004 following the Bluff Central accident in which a 'Fox tragically lost a wing through being flown too fast in turbulence. He wrote (copied to then RAA-Aus tech manager Jeff Shepherd):

"Carl, thanks for copying us in. I had already let Jeff know about the development history of the Skyfox aileron system; however I would comment, from prior experience, that it is counter-productive to hypothesize on the cause of an accident until ALL the investigation data is in. I would, however, comment that so much effort went into eliminating the aileron flutter problem during the pre-certification development phase, that a Skyfox that was both built to plans and correctly maintained, is extremely unlikely to experience any flutter, let alone a catastrophic flutter, so long as it is being operated within its certificated limitations.

 

Therefore, if indeed aileron flutter was a factor in this accident, it would follow that some defect condition must have existed that would pre-dispose the aircraft to flutter. Because it takes a fairly significant excitation to initiate flutter in that aircraft (due to the friction in the aileron hinges) such a condition could develop over time, and the fact that the true flutter onset speed was reducing down into the normal operating range would be masked until the aircraft encountered something (e.g. turbulence) that set it off.

 

Further, for that to cause the wing to come off, suggests that there was more to it than simply flutter, because I fluttered the ailerons on the prototype CA21 a number of times (approaching a dozen) with no detectable structural damage until the last one, which occurred at around 108 KCAS; it broke a single aileron hanger.

 

Therefore, detailed examination of the wreckage is necessary to identify, if possible, whether any pre-existing degradation to the airframe existed; and until we have the results of that, I believe it is unwise to speculate."

 

"The accident" to which Daffyd refers is the Bluff Central accident, on which he subsequently supplied a full and detailed report on which I intend to write further, as it holds some important lessons for Skyfox owners. I hope the above lays to rest any unfortunate impression that may have been given on this thread that Skyfoxes have a particular problem with aileron flutter. It just aint so.

 

Regards Carl

[carlsnilsson]

I was wondering the other day if anyone has thought of having a Skyfox/Gazzelle flyin' date=' maybe even have it as a part of Natfly, just some thoughts and I realize that as soon as a good idea crops up someone gets to work hard to make it happen, it would be cool to have a line up on the apron!!! [/quote']Good thinking 99! 'bout time we did that again. I really like Temora - friendly people, good old pub, old warbirds flying - and I haven't been there for 5 years.

I just had some comms with Daffyd Llewellyn - he confirmed that the Darwin fatal accident was with a CA21 which had suffered some significant rot problems - Llewellyn's analysis, which was submitted in Court with a heap of supporting evidence, read like the denoument in an Agatha Christie episode of Poroit. To my mind, it confirmed that that accident almost certainly was not caused by flutter or even rotten hanger breakage (which I had always understood from the initial report), but rather was probably initiated by overloading the wing and breaking a rib near the rear spar (the rib nearest the lift strut attachment point), which itself had suffered weakening due to moisture ingress. That rib (and hanger) suffers the most strain from the ailerons when using them over-vigorously at speed. You should pay particular attention to drain holes in those bays and the condition of that hanger. "Look after the aeroplane and it will look after you", is the main message.

 

Regards Carl

[Blueadventures]

Hi Paul

 

When were the aileron centering eye bolt, wire and spring setups fitted to the Skyfox and do you know why they fitted these?

 

Cheers

 

Mike

 

 

[Neil_S]

Hi Paul,

 

I co-own a Gazelle with a friend, and had the following question. It would be great if you could assist.

 

The edge of some of the fabric on top of the wing of the Gazelle is just starting to lift. It is only a bit at the moment (about a quarter of an inch or so - on top of a rib next to the tank), but obviously the longer we leave it the more it will lift off. I was wondering what you would recommend as the best way to stick it back down again? Is there some particular glue we should use, or some other technique to fix it back down?

 

If it would be better I can send you some photos if you care to let me have your email address.

 

Thanks!

 

Neil

 

 

[foxworker]

Hi Paul,I co-own a Gazelle with a friend, and had the following question. It would be great if you could assist.

 

The edge of some of the fabric on top of the wing of the Gazelle is just starting to lift. It is only a bit at the moment (about a quarter of an inch or so - on top of a rib next to the tank), but obviously the longer we leave it the more it will lift off. I was wondering what you would recommend as the best way to stick it back down again? Is there some particular glue we should use, or some other technique to fix it back down?

 

If it would be better I can send you some photos if you care to let me have your email address.

 

Thanks!

 

Neil

Neil,

Apologies for the response time. I do know what you are referring to so I don't require photos. The glue that was used in the factory was polytac. Iwould be using the same. Google the product and you should be able to get a good idea on how to go about your repairs. The other person who would be of help to you is carlsnilsson via this forum. Thanks Paul