Bob Llewellyn

95:10 is there for YOU! And, we have a version of experimental - self education in 95:55. Read the operational categories?

I don't fly in cowsheds!

For flutter to occur, there have to be two flexural modes in the same frequency. For example, if the pendulum frequency of your elevator, as modified by the dynamic pressure of your speed (naff all change below ~100kts is the rule of thumb) happens to match the primary flapping frequency pf your tailboom - i.e. the musical note it would make if you held the tailboom off the ground by the fwd fuselage, and hit the aft end with a hammer - then it's goodbye tailplane, possibly tailboom as well. You will then return to the ground... 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.

In the beginning, it was 170lb (77kg); then it arose, and (pausing briefly at 80kg in a few draft Design Standards) became 86kg. CAP-482 (BCAR-S), JAR VLA (is it EAR-VLA now? No, CS-VLA, that's right...), ASTM 2245 (LSA, US-style) all use 86kg. I suspect something - Transport Category seat design? - uses 90kg, but if you're under 5,400kg MTOW, 86kg is considered the upper limit. 50kg is about the lower limit.

Douglas Adams considered that being a Director of an insurance company should be punishable by death. He was right. The whole thing demonstrates the luddite ignorance and incompetent credulity of the actuarys - it COULDN'T be unmitigated greed on the part of management, I'm SURE they don't think that way...

Yes. Yes you are. You see, everyone who tried it before, DIDN't KNOW what I know... they said I'm mad, but I'll show them... I'LL SHOW THEM ALL (wipes foam from mouth)... off to Bunnings for a Chinese mower; off to Big W for a kid's bike; off to Ag Supplies for some aluminium tubing... and the SkySmart Scout will RE-INVENT AVIATION!!!!!!!!!!(!!!!!)

A 912? but they're made out of gold and platinum, with rare jewells and exotic incense - or that's what the prices reflect. 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!

Oh well, the French are just... french. Having got that bit of racism out of my system, the stresses in such a fabric balloon are actually quite high, and the technology of garaunteeing the stitching strength etc is pretty high. Look like fun though. 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...

Thermosetting plastics of the epoxy family have two modes of polymerisation. The fundamental mode forms large elongated molecules, with (relatively) rigid zig-zag shape, and a few cross-links to adjacent molecules. The GTT is, crudely speaking, when the "free" energy level exceeds the cross-link energy sum for each molecule - wtf? well, hotter = more amplitude of vibration of the atoms, and when they are stretching the intermolecular bonds too far, the bonds can "snap" across to the nearest adjacent attachment site. So, them there rigid zigzag molecules start to slide past each other. 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,

(a) sitting in 40 degree heat gives an elevated temperature cure, only takes a few hours or less; (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.

Go gliding. The adverse aileron yaw is something fierce, so feet are always in use. When thermalling, the inner wing is always on the point of stall, so you are dancing between keeping it co-ordinated, and picking up the inner wing with a dab of rudder. After that, 3-pointing Thrusters was a piece of pxxx...

I suspect the 160 has slightly smaller structural margins than the earlier generations of Jabs; and the 120 uses (used to use?) an earlier gen wing design, albeit updated to somewhat later production techniques - I think - Jabiru don't share these little details with me...

Could be engine approaching detonation limits, elasticity of airfame approaching flutter limits, reduced stiffness of spar boom approaching buckling limits, reduced atmospheric density exacerbating prop compressibility... the GTT is not a magic number, it is a critical boundary; then little thangs in the plastic change their nature before the GTT is reached, and there are other considerations (as listed, plus probably a few i ain't thunk of).

Much becomes clear, particularly the state of Tony's records (which I hold); thank you! A pity Belton trashed the documents, though it brings into question what (business shenannigans?) he might have been hiding. Academic now. 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!

Goodyear Inflatobird. One of the many efforts to make a glovebox pilot retrieval aircraft for the USAF...

I'm SURE I could fit a minigun to a Drifter, FT ...for peaceful purposes only... :cops:hang on, am I bringing the thread into disrepute???

... or AAMs (defensive only, of course) for jabirus...

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

Ok, ta. As I understand it, Steve's legacies - the use of 304 stainless steel lugs, of the correct form for failsafe and size for reparability; the use of 6061-T6, the short tail arm and big pendulum stability etc, lived on through the Gemini, UK TST, TST-L / T-300, TST-E / T-500... 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!)

The Skyfox is not required, by its design standard, to have either a Vb or Vno. This has cost lives. How many RAAus pilots know the difference between Vb and Vno? How many know that, eg, the Drifter Vb is ~12 knots below Va?

no worries! However, if I give advice, I am meant to be guided by any relevant Product Safety Standard - which for erringplanes comes under Certification. So, I am indicating that I have been so guided, and consider them of little relevance to getting your creation off the ground. Or we could just kill all the lawers... (Shakespear)

The cost of horribly expensive prototypes can be reduced by avoiding repeting known mistakes; this is what experts are for. Now, such an expert (I can think of one who did) can say, "if you do it like THIS and THIS it will work, no further discussion", which is pretty unhelpful to the innovative designer. 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!

Yes, the RAAus IS a source of military pilots for times of conflict, which is why they need a military-level medical, and why the government sponsors flying clubs... hang on, that was the 1930's. BS proposal, flytornado. If they're fit enough to be in charge of a motor vehicle capable of killing tens of people in a single accident, then they're fit enough to fly a Skycraft Cyclone over this wide brown land. Have a coffee, eh?

Ok, so you have nothing tangible on commercial operator's accident rates vs RAAus, you just think my arbitrary "no more than 3 times GA average" should be "no more than much more than 3 times charter average". So what? 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.

They used to have twin pioneers there, they give a Caribou a run for its decibels...