Bob Llewellyn

So, where does that put the idea (my idea) of wanting to build something because I want to build it?I want to build a flyin' machine out of metal (I like to work with metal), that looks very 1930's, a sort of roughly scaled F4U. I don't want to make it because it's a practical economical aircraft, I don't want to mass produce or market it, I want to make one because I've always wanted one.

Be very careful out there:If it happened in Germany, it could happen here too ....

 

http://www.skynews.com.au/offbeat/article.aspx?id=945805

Hey guys! Just wondering do the really simple fabric ultralights have a weight balance to stop the flight surfaces such as the elevator from fluttering? or are they spring balance or use tabs to lift up the flight surfaces during flight? Because in plane like Lazair don't really have much on them from what i can see except small tabs, is that what they use to balance the elevators?Thanks guys!

There are a number of ways to prevent flutter, one of which is mass balance. Mass balance is the no wearing parts, garaunteed 100% reliable option (until someone modifies / repairs the control surface enough to push the thing out of balance, but that's another story...).

The Lazair/Drifter/Thruster/Quicksilver/etc all have a much lower elevator pendulous frequency than the propellor blade passing frequency, so the prop causes no flutter (doubly so for the Lazair!); and the natural, or resonant, frequency of the tailboom itself is also much higher than the elevator critical (pendulous, natural, resonant, it's all the same frequency) frequency. The boom flapping frequency with the tail assembly on it is much closer to the elevator frequency, but has a great deal of aerodynamic damping, and quite often the unbalanced elevators will actually act as tuned dampers if the two frequencies near each other.

Essentially, the above airframe tuning, the porous fabric, the high aerodynamic damping (ie all the air that a flapping tail must push out of the way), and the low driving energy - ie the low dynamic pressure / low speed, make such designs quite resistant to flutter.

If you use calendared fabric, or sealed Mylar skins; put a sharp trailing edge on your elevator; and put a loosely rivetted aluminium adjustable trim tab, driven by a lawn mower bowden cable through a bent tab, you stand a much better chance of having a destructive resonant event. Do not try this at home.

Hi Guys,I'm trying to find a reference for standard pilot weight for W&B calculations.

 

I thought I read somewhere that it had been upped from 75KG to something like 80KG, but haven't been able to find anything definitive.

 

Any pointers out there?

 

Thanks in advance

 

Richo

what a bunch of wankers! What the hell has it got to do with Repco what you use the plugs for. If someone asks just say they are for a getaway car, that'll make it ok....I was once trying to buy a actuator in the US I happened to mention aeroplanes and they shut right up.. Untill I told them the actuator was to remotely open the mailbox, then it was ok....If I buy something it's up to me what use I put it to once I leave the shop....... The sellers should just pull their nosy heads in....

Remember that it all started with the Skycraft Scout. The people who wrote the original design standards for ultralight aircraft tried to "simplify" the certification process - which was seen as the major cost factor - by omitting things from the standard. In effect, they started with the obsolete standard, CAR 3, which already lacked any requirement to calculate the safe fatigue life, or otherwise make the structure damage-tolerant, and also largely ignored any requirement to produce a maintenance manual; and took a machete to it and cut out a lot of other things - gust loads, for one. The concept was that, firstly, the things were butterflies and not likely to fly more than 100 hours per year; and secondly, that if (when) problems arose, they would be dealt with by issuing ADs; and anyway, they flew so slowly that it was not really necessary to bother calculating the gust loads. Also, those were the days when everybody did his own car maintenance. A Drifter looks like the sort of thing any handyman could build using a Wolf Cub electric drill and a hacksaw, starting with a Hills Hoist, and people felt that building aircraft had at last come into everybody's backyard capability. Fatigue life? What's that?Concepts such as designing for minimum maintenance were not even dreamed about; the attitude to even CAR 3 aircraft (such as most of the Cessnas and Pipers from the 1950s thru 1980s) was epitomised by a Piper sales rep, who gave a spruik at the NSW Royal Aero Club, on the latest version of the PA-28. When somebody pointed out that the original PA-28s the club had purchased were already showing signs of corrosion, he reply was "Gawdam, man, those airplanes are five yars ole!".

 

What has in fact been happening, ever since it progressed past the Skycraft Scout, is the re-invention of the aeroplane. The evolution from open frame, externally-braced aircraft such as the Drifter and the Thruster, to enclosed bone & rag things like the Lightwing & the Skyfox, to stressed-skin devices like the Jabiru and Tecnam, is almost an exact replica of the progression from the Wright Flier No 8 to the Cessna 172 - the differences have mainly been due to modern materials. We even had a few biplanes along the way. though they hardly made a dent in the progress.

 

Now we're starting to see the necessity of re-inventing FAR 23 - or even going a bit further, to include low-maintenance design. This is, I suppose, a natural consequence of the fact that, far from the fix-it-yourself attitude of the 1960s, we are now in the "throw-away white goods" era where people have lost the basic skills to do maintenance, and anyway can't be bothered with it.

 

The whole idea started out with the belief that "there has to be a simpler way". If you study history, this is a recurring theme; the first manifestation of it was the "Flying Flea" of Henri Mignet; the second one was Bensen's Gyrocopter; the third was the rogallo-wing hang-glider; and the fourth was the ultra-light aeroplane. They all go through much the same phases. They all have small groups of fanatics who persist with the original idea after the mainstream has moved on. They all have fundamental shortcomings; and by the time people have identified the shortcomings and addressed them, somebody else says "Hell, this is too complicated - there HAS to be a simpler way!" - and the cycle starts again, in a new guise. Overall, it does not seem particularly sensible, to me. I wonder at the overall sanity of the human race, actually.

 

The way to break out of this endless loop, if anybody actually wants to, is to do some reading; Stinton's book "The Design of the Aeroplane" is not a bad starting point. The statement "those who fail to study history are doomed to repeat it" is observably correct. How about we look at all this experience, and make our minds up what we really think personal aircraft should be (and obviously that will need to be divided into several categories), and in effect present the manufacturers with a realistic design specification?

 

Or am I being altogether too logical?

Not sure how "experimental" you want to be but here's a new design... http://www.quicksilveraircraft.com.au/QUICKSILVER/AVIATOR_HFA.htmlAnd I was just thinking that people use the half-VW engines, so why has no-one made a half Rotax 912? Got to have potential?

Seriously, a horizontally opposed 4-stroke twin is a good way to shake the fillings out of your teeth, the cylinders out of the crackcase (it will be, trust me!), the nav lights off the wingtips... the halflingers work thanks to low powers, low stress levels, and short lives. Go and buy a 25hp Honda V-twin industrial engine; 42kg ready to rock your cement mixer, electric start, CDI, oil pump. Trash the "industrial' carby & fuel tank, and it'll make your Hummelbird zip!

Nah.....this is the one I was thinking of......actually a trike....great for a bit of fun in a paddock or on the beach.Comments seem to suggest $12000 is a bit rich.......

 

The InflatoBird packed into an 18" diameter tube, about 6 feet long, plus the power plant (a 72hp McCoullacghragh); and inflated into a 2-seat, side by side motorglider. The same USAF requirement spec gave us the 2nd application of the Rogallo wing, the Bensen gyrocopter, and I think started the WASP jet platform program...

I was referring to things like main rotor blades that are already cured, usually in an autoclave, and definitely epoxy. But was interested to know what sort of stuff they might be using that is incapable of dealing with temps under 60 deg C, as that is usually the lowest temp for an accelerated cure, most I've done are around 120 C +.

Now, the secondary mode of polymerisation of thermoplastics, involves a lot of cross links forming close together; if excited by enough heat - as in staged elevated temperature curing - the zig-zag molecules can actually get a bit shorter, as the intra-molecular bonds are reformed into inter-molecular bonds.

The more inter-molecular bonds there are, the higher the GTT becomes. So, a room-temperature cured epoxy has a low GTT as cured; running it through temperature cycles - such as day and night through half a year - gradually elevates the GTT.

So why not autoclace the crap out of it? Because the maximum rupture strength of the epoxy matrix is reached at less than complete cross-polymerisation; AND, critically, the maximum fatigue endurance is reached at rather less cross-polymerisation than the maximum rupture strength. The Jabiru "system" - which includes chemicals, application temperatures and times, and cure cycles - achieves outstanding fatigue resistance, at adequate rupture strengths, using low-overhead production techniques (otherwise nobody could build LSA-E kits!).

Rotor blades are rather specialised, in that the centrifugally induced stresses dominate; their fatigue resistance has to be optimised only for a spanwise mean-plus-cyclic situation, and no triaxial restraint exists in the loaded area, unless the designer has gone to truly extraordinary lengths to screw up!

I have had the - pleasure? - of designing a repair scheme for a set of doors on a certain model of FAR-23 composite piston single, which at 1100 hrs TT (then the oldest in the world fleet!) had developed fatigue cracks above both door-mounted windows, from slipstream tip vortex impingement. They were autoclaved carbon fibre doors, strong enough to kill oxen, but they couldn't handle fatigue.

Jabiru put loads of work into structural integrity / composite fatigue research, and when it comes to resilience, they are the (composite) light aeroplane gold standard. Note that I hold no shares in Jabiru, do not own a Jabiru, and have no present intention to get one; but I have (somewhat grudgingly) acquired a high respect for Rod's approach to composite structure,

What sort of composite resins are they using? The ones I'm used to get painted dark green and sit in 40 deg heat long enough to burn you if you lean on it, then they spin it up over 300 rpm, and lift 6+ tonnes with it while it flexes all over the place.

(b) They're probably using epoxy, because it is the superior fatigue resistant resin at high stress levels (vinyl ester can be very good re fatigue, but it is subject to creep at high stress levels, and unlike epoxy, it is not specifically nominated for aircraft use). In fact, as the J-160 was designed against JAR VLA, it can only be epoxy.

OK it's been driving me crazy. A thread with this heading has been on and off the instructors forum for weeks. What is the secret that the instructors are keeping to themselves? What pearl of wisdom would make my landings more predictable and professional? What are those two pedals for anyway?

Interesting then that Jabiru haven't added anything similar to their 120 and 230D POH, yet they're the same resin.

The minimum quoted Glass Transition temperature for lc3600 cured at 25C ( i.e. fairly much ambient for Jabirus since the minimum construction temp is normally quoted at 24C) is 50C, so there's a fair bit of margin there. Certainly it's the reason why nothing other than white is acceptable on the upper surfaces. Perhaps Jabiru are becoming very conservative (and they have always been reasonably conservative in all their performance claims, relying on only properly conducted tests to required flight test specifications), but I'd not be surprised if the reason has more to do with maintaining an acceptable climb performance than simply structural reasons.

I gave Tony all the information I had about the Thrusters. We spent around six months trying to fill the blanks.All documentation that was at the factory was burnt by Belton when the company failed.

We also covered the pendulum instability as I was the first to experience it at the time I had put it down to my ham fisted flying from the right seat. I think Tony tracked it down to turbulence caused by the exhaust positioning compounded by the shortened tail. The shortened tail boom was brought about so the aircraft would fit into a 747 cargo pod.

 

Never liked the stainless strut fittings. All stainless originally came from Alex Prior at Path Aviation at Taren Point now long gone.

 

The Thruster was never meant to be certified when it was first designed. It was really a round peg bashed into the square certification hole. Made a few people sit up and notice when we pulled it off. Even more pleased we beat the drifter to it.

 

I'm not sure where Brian Fimmell is if he is still alive but he would be the one to track down. Steve will still not talk about the Thruster either will Belton. He is ferrying Dash 8s around the world.

Tony and I did discuss the pitch instability / pendulum behaviour, but it was not until just before his death that I figured out it was due to the wing wake touching the LE of the tailplane, at the roots. As the boom appeared to grow longer over the first 20 or so Geminis, and then the nose of the T-500 grew longer than the T-300, Tony's records indicate a range of boom lengths that were factory made, and therefore presumptively ok. A bit of extra shortening for shipping purposes also explains a lot.

TOSG went into hiding shotly after Tony died - my professional life went bizarre, and finances got thin - but it's re-appeared, as the CASA audit of RAAus appears to be threatening the status of Thrusters. I'm in the process of packaging the justification for retrofitting 582s without specific EOs at the moment. Tedious, and shows that CASA / RAAus still aren't up to speed with Australian law, sigh...

You can find the new TOSG website via the Thruster's forum here in Recreational Flying; the admin of the old website is giving great support re transferring all the previous data. Pnward and upwards!

Isn't there a "blow up" aircraft. Air pressure holding the wings in shape or something?

There is definitely a war for the lower airspaces starting soon and CASA are definitely in no way equipped to deal with it.

I sense a market opportunity for an eight-gun 95:10...

The finger of blame only stops when the accident rate drops though. Wait until a UAV takes out a Jabiru, then CASA have to make a choice.

Bob, by the time the two seat Thruster came along Steve was pretty well out of the picture. First TST was known as the Gemini. Main players were Belton, Brian Fimmell When certifaction started Newton was involved from memory. I left just as certification was completed. The TST passed three times with the then dept moving the goalposts each time.When it finally passed it was given the 19-0001 number by AUF. 0002 went to the Drifter .

0001 number was taken by Middo and placed on his drifter while the Thruster was being rebuilt. Should go back to show history as it was.

By my records, the 532 installation was walked through by Neville as an addendum to the T-500 package. Can you shed any light on this? particularly documents? (I have taken over from Tony as the principal of TOSG, but don't have his encyclopaediac knowledge of the marque!)

You said it yourself - knowledge of the flight envelope. The basic comprehension of what it means should be in whatever theory exam people have to do ( I assume, the equivalent of BAK - but it's 50 years since I looked at that sort of course material); the actual numbers that apply to the particular aeroplane are in the flight manual (and, hopefully, the speeds are colour-coded on the ASI - but not always). This covers factory-built aircraft. How does specific type endorsement deal with home-designed aircraft? The whole concept of type endorsements comes apart on that point alone.

Was never thinking of type certification Bob. This is a one off for sure.

http://www.airdromeaeroplanes.com/index.htmlIf your not into the WW1 scene his ultralight kits are pretty well priced, even with the cost of an engine you'd be flying for around $25-30k,

 

http://www.teammini-max.com/aircraft/

 

These guys were giving plans away for free recently,

 

http://www.liteflite.com.au/Default.aspx

 

I've been trying to get up north for awhile to do tug training with one of these, not sure of the cost ,but the utube vids show a very capable plane

 

The point is , there's plenty of these types around if pilots want them, the thing is ,not many want them so the numbers are low, there was a neat little single sweater at Natfly a couple of years back, great little aircraft, I wonder if they sold many kits?

 

Matty

I don't think this thread was intended for the negative experts who can somehow prove that simple design isn't possible.Fortunately in human history someone will come along and prove them wrong.

Prototypes are always horrifically expensive in hours and dollars, but if done professionally, the inverse applies to production models.

 

It seems the minute I suggested that there was enough new and used product on the market and the issue was promoting the class it sparked ab irrelevant design spit

The body of law built on the english system, allows minimal safety standards for single seaters; self-risk is (grudgingly) considered a human right. As soon as the possibility of harming another person comes into play, the required safety standards - and so cost of everything - goes up hugely. You can still build a modernised Skycraft Scout for under $10k, and it flies, so stop ys whinging!

Dafydd you are confusing the legal implications of learning to fly with flying, the type endorsement is for people that have certificates.The RAA really needs to bite the bullet and introduce the GA style medical examinations to thin the pack of the weaker and sicker pilots who are more likely to kill themselves flying.

 

Its the only way to diminish the RAA of the negligent liability

I don't think people with commercial ratings are superhuman, but we know that commercial operators are supposed to have standard operating procedures etc. as part of an AOC, and I would be astonished if they didn't have an accident rate much better than 3x less than RAAus.You are comparing comparing US GA in the '50s through early '70s to Australian ultralight data. You say they are directly comparable, but what evidence do you have? You should be able to produce some statistics to demonstrate they are more comparable than RAAus vs. GA today, for example. I personally don't buy it.

 

I am not unfamiliar with a normal distribution. I would make a few couple of points:

 

- It only make sense to fit values into a distribution if they are part of the same population. There is evidence in this case they are not, e.g. if you assume the HF accident rate, or the maintenance problem rate are the same, the results are implausible. This to me is evidence the populations are not the same.

 

- 2 sigma, 3 sigma, 6 sigma - being outside these bounds is not impossible, it just means that a value is not likely to be part of the originally measured population i.e. there is something different about it.

 

- I think you are confusing the standard deviation and the mean. I have not referred to the standard deviation, and I think this is the first time you have mentioned it. A value 6x the mean is not remarkable in itself.

 

Asking for evidence is not a delinquent response. It is part of ensuring that we don't waste our time and energy in one area when the problem lies in another.

Ok, you personally don't buy Airworthiness Regs or Pilot Training as relevant to accident rates. You're entitled to that opinion.

No, you are arguing that the two populations have a vastly different skewness or Weibullness, which there is no evidence whatsoever to support.

It is not the first mention I have made of the standard deviation; and as I understand maths, the occurence of an event with probability of >1 / 99.9999 is much more remarkable than that of an event with probability 1 / 99.7.

You have so far rejected any relationship between Airworthiness Regs or Pilot Training and accident rate; you have rejected any similarity between US GA of the 1950-1970s and RAAus operations; you have rejected any similarity between Piper Colts and Cubs, Cessna 140s and 170/172s, etc, and RAAus aeroplanes; you have rejected any similarity between US air and Australian air; AND YOU HAVE GIVEN NO BASIS FOR THESE REJECTIONS.

There are none so blind as those that will not see.

Bring down a couple of Caribous, so that they know what noise really is........