Bob Llewellyn

Not at all. I suggest that the statistics we do have, indicate that the only change that might benefit pilot training, is to return to the original AUF deal of spin training in gliders. But maintenance is, I believe, becoming the bleeding sore of Recreational Aviation safety at this point in time.

We progress! Re-read my post, I explain why I think that it's reasonable to assume that RAAus pilots are not more than 3 times worse than GA at making decisions. I would note that the majority of commercial operations outside of transport category, are lumped into the GA accident rate, and provided CAR 35s with quite a bit of work. On what basis do you think someone with a commercial rating is superhuman? As to the comparability of the data: I firstly remind you that I'm comparing similar stages of development of regulation in the interests of safety, which requires comparing US GA in the '50s through early '70s to Australian ultralight data. Now, in the US in this period, single engined instrument trainers were few and far between; the majority of pilots operating GA were flying single engined aircraft in VFR, with a bit of night VMC thrown in. By the '70s radio aids were being found in single cockpits. Over the same period, the majority of single lighties changed from the "grasshoppers" and their civil derivatives, to the inimitable Cessna 172 / Beech Debonair / Piper Cherokee; the average stall speed crept up from 40~45kts to 52~57kts (at the top end of town), and constant speed propellors began making a showing. Furthermore, most of the pilots playing GA over this period were not military trained, but the people too young for WW2. So, it's pretty much apples with apples. Note too that the GA accident rate towards the end of the period was ~ twice the current US GA accident rate; the systemic immaturity had an effect. With regard to your struggle with vastly varying HF accident rates, there is no point in further discussion until you can find your way around a normal distribution - I'm not trying to be offensive, but until you can appreciate the difference between 2 sigma and three sigma, you won't see the absurdity of considering 6 sigma as a realistic probability. We know the photo is out of focus. We know that RAAus has, since HORSCOTS, focussed on pilot training. We know that the gross fatality RAAus accident rate has bettered the GA accident rate at a similar stage of development. We know that the RAAus accident rate has been getting worse for four years. We know that the comparable GA accident rate did not get worse over a similar period, or at any time subsequently (to a comparable degree). We know that GA had similar pilot training, indeed less developed. We know that GA had a strong maintenance system. We know that RAAus has nothing comparable as a maintenance system. The differences here? RAAus accident rate getting worse; RAAus no comparable maintenance system. It behoves us all to either demonstrate, with a high level of confidence, that the RAAus accident rate increase has nothing to do with the ongoing lack of a maintenance system; or to improve the maintenance system. Just sitting there saying "I don't know but I disagree", or even "I don't know so I'll do nothing", are delinquent responses.

Yessly. The Seabird ended up needing a couple of auxiliary fins out near the ends of the HS, although it's fin LOOKS big enough. Re stall, if the initial stall doesn't happen in the 5% of wing adjacent to the fuse, it'll drop a wing fairly enthusiastically. Not necessarily a prob - Doolittle used to flick roll P-38 lightnings, which do the same thing stallwise... Taylor solved the 'shaft with a French invention, the shot coupling - as used on the Riley motorblanik. not heavy or hard to do. The 19m Kestrel fluttered the pilot to death with no control slop at all; aeroelastic resonance is a high-energy phenomenom. Good luck! Glass U/C tends to shear between the fibres in an embarrasingly short time; if you sketch the kinematics of the curved bit, you will see that the shortening of the inner fibres causes a transverse tension, on top of the shear forces. I suggest spring steel, or (for gentle landings) aluminium. A properly designed steel springleg for a 600kg LSA I wot of, weighs about 10kg with wheels, tyres and brake discs... For the tailfeathers, a prop brake for engine failures and some kind of dive brake so you can land with a little power on will make a perfectly acceptable aeroplane, although you won't Type Certify it like that!

Yeah, so I took 9 year's worth of data. Not much scatter, either. I think a correspondence course for less than $200- total, would suffice for the L2s interested. The issue is presenting the necessary engineering information in a way that you don't have to be an engineer to use (but you will have to be able to read a chart / graph:cheers:) Note: i can say no more on this head, without violating the non-commercial site rules...

NO - study MIL-HDBK-217; "Probability and Statistics for Engineering and the Sciences"; failure modes and effects analysis. Also, the 2,000 hr TBO Lycoming has been maintained at least 80 times in that period, with the cylinder heads reconditioned at 1,000 hrs. By your "reduce maintenance" argument, a Rotax 503 run 300 hours, with only 12 maintenance exercises in that period (and no head jobs!) must be safer.

The RAAus training syllabus is accepted by CASA; and 20 hours minimum for day VFR to the equivalent of a Restricted PPL (which, pre competency-based days, could be had in 35 hours) suggests that it should be of similar rigour. If you have data otherwise, please notify the Ops Manager and CASA. We also have BFRs, just like GA. Now, if you read the document, I set one boundary at RAA pilots having no less an accident rate than GA; which, you state above, you consider excessively low. I then point out that the residuum of RAAus fatal accidents, some 96% of them, would be an extraordinarily high level to set at the door of hardware failure. I did not do the simple maths in the document, but your calculator will no doubt tell you that if the RAAus hardware failure rate is the same as GA, then the human factors RAAus accident rate must be 14 times the GA rate; and the RAAus training regime, ~1/14th as effective. Hands up anyone who believes that the RAAus pilots (a lot of whom are also GA) are this woeful? Halfway between the boundaries of the same HF accident rate as GA, and the same hardware accident rate as GA, lies a HF accident rate of 7 times that of GA. As a lot of RAAus pilots also have had GA training, and based on those I have met, I do not believe that the non-GA trained RAAus pilots are vastly less competent than the GA trained ones, within the operational limitations of 95:55. A similar situation exists in the Gliding Federation of Australia. As the RAAus training syllabus is CASA acepted, AND the RAAus accident rate spent several years below the GA accident rate at a similar state of maturity, AND the GFA have over 50 years of satisfactory HF accident rate despite putting most pilots through in less than 20 hours, AND a lot of RAAus pilots also have GA training, I consider that assuming three times the GA HF accident rate is unreasonably conservative. I do not see any reason supporting your arguments to the contrary. If you have anything more than a baseless opinion on which to condemn RAAus pilots, I reiterate that you should communicate it to the ops manager and CASA immediately; and also present the justification for your apparently baseless insistence that RAAus experimental homebuilts - and aircraft built to partial design standards, such as the Skyfox - are just as safe as Cessna 172s maintained in accordance with GA practise. My ANALYSIS of the DATA is now fully on the table. Where is yours?

No aeroplane can be designed for infinite life, as no materials give the necessary strength to weight ratios within their fatigue (metals / plastics) or creep (timber) limits. Therefore, the most structurally efficient aircraft will fail "all at once and nothing first..."; to prevent a nasty surprise, surely this means that one should inspect everywhere? If one completely eliminates fasteners of any sort - which means some sort of FRP, including the engine mount - and creates the nanobots necessary to detect the onset of post-impact fatigue damage (see FAA, rudder doublets) - and puts up with the FRP undercarriage springs regularly failing due to the nature of the material - you still have fuel pumps, fuel hoses, fuel fittings, an engine, a propellor, fasteners... but that will be a minimum-inspection aeroplane. A composite glider would be the go... but how do you take off?

Sounds like an aluminium Denny Kitfox...

The AUF concentrated on pilot training, and the accident rate plummeted. Now the accident rate is rising. If it is not hardware-related, how did pilot training screw up in 2009 and subsequently? Is the Human Factors training a killer?

Very good, but I start by considering the possible - NOT the expected bounds.

Pre flight inspections are a maintenance procedure - by your argument, eliminating pre-flights will increase safety. Well, off you go then!

I'm trying to show that the stats establish some boundaries, and anywhere within those boundaries (save for what I consider a laughably high human factors contribution), the hardware contribution is orders greater than GA. I note that some people separate human factors during maintenance (eg misfuelling, not checking a clogged fuel filter) and human factors during flight, which further confuses the issue! A perusal of the accidents and incidents in back copies of the AUF / RAAus rag tend to show more hardware issues - generally minor - than pilot choices gone wrong. At present, L1s and L2s are trying to keep aeroplanes flying with scant or non-existant type specific maintenance data; and I'm saying that relatively little expenditure on training and processes could reap a disproportionally large improvement in achieved safety.

Pish Tish - invest $1 million; sell 200,000 units at $10 profit each (by Net Present Value estimate), and you've recovered your dough. I'm sure there are at least 100,000 people already with $10,010 in their pocket for a Skycraft Scout Mk 1! Oh blast, Victa don't make the engine anymore.

Nonono... get a couple of sailing dingy masts & sails, vandalise the kid's BMX bike, vandalise the Victa (lawnmower), carve a prop, and viola! The Skycraft Scout is born

Look at the early manufacturers - Bedson ("we don't need any airworthiness!") - fatal structural failure, own design. Winton - fatal structural failure, own design. Veenstra - fatal, maintenance failure, own maintenance, own design. The Thrusters have a mandatory AN on the wing to wing strut bracket, an AN on the fin spar; and the single-seat Thrusters (which do not meet 95:25) are known to develop cracks in a number of fittings. As for crashing slowly, I invite you to dive into the ground vertically at 40 knots. Flying most aeroplanes, particularly landing and takeoff, comes down to energy management. Having flown Drifters, Thrusters, a Lightwing, and a Jabiru, the Lightwing and Jabiru were actually safer to land, as neither were prone to drop behind the drag curve and sink like a sack of spuds into a spine-crushing ground impact. This was the basis, which the CAA (CASA) team did not argue, for the HORSCOTTS decision. I was in the room at the time. ps Steve Cohen did a competent job, both mechanically and aerodynamically, with the basic structural engineering, although one or two details are not lovely. Newton Hodgekiss (CAR 35 engineer) applied slightly more sophisticated techniques to lighten the structure for the two-seaters, arm-wrestling with David Belton (who wanted to keep them economically viable). The resultant compromise meets higher load factors and critical airspeeds than the wire-braced Drifter, but age and inadequate maintenance has shown up a few potential traps.

The first conclusion must be (as some people have already observed) that the RAAus accident reporting - that is, the information provided to RAAus by operators and CASA's expert accident investigation team (sorry, put that in for a laugh) is inadequate. Note that the basis of comparison is the timebase against airworthiness standards, which is accepted by ICAO as the prime determinate of hardware safety. Now, if one applies the (some would say, optomistic) assumption that RAA & GA human factors rates are equal, then even on a 1-sigma basis it must be accepted that hardware failure accident rates in RAAus MUST BE higher than in GA. Having been involved in the wreckage analysis of a few light aircraft crashes, and having had over 300 aircraft repair schemes approved, I have no doubt whatsoever that most RAAus aeroplanes would not meet a GA airworthiness standard - or even many ultralight / sports airworthiness standards - in many areas; as said standards are a mechanism for reducing accident rates, the argument is a non-event. Try it thussly: 1) Airworthiness Design Standards reduce the accident rate; 2) Most RAaus aeroplanes meet, at best, parts of an airworthiness design standard; 3) RAAus aeroplanes should, therefore, have a higher accident rate from hardware failure than GA aeroplanes; 4) RAAus aeroplanes do have a higher accident rate due to hardware failure, than GA, although there is insufficient data to be precise about the figure; 5) The Maintenance of Airworthiness, via Approved Maintenance Organisations, Licensed Aircraft Maintenance Engineers, and Approved Maintenance Data, prevents the vast majority of hardware failures in GA; 6) RAAus maintainers have very little training*, very few aeronautical engineering qualifications, and extremely little Approved Maintenance Data; and there is no parallel substitute; so RAAus aeroplanes must undergo a higher rate of hardware failures per hour of operation, as they operate under the same laws of physics etc; 7) The RAAus accident rate is increasing from a minima, and the fleet mean age is growing. It is internationally accepted that the older the fleet (GA or otherwise), the more rigorous the demands on maintenance. *LAMEs are trained to apply Approved Data; LAME training is not of great use in RA, without Approved Data specific to the Type in question. So - RAAus needs to lift the maintenance game. Now, as CASA is ultimately responsible, and CASA does not provide RAAus resources (fiscal or otherwise) to enhance the maintenance practises and expertise of the membership, it is CASA'a irresponsibility - imposed upon them by various Ministers for Aviation - that allows this failure. If you can demonstrate that, somehow, design, construction, and maintenance in accordance with Design Airworthiness Standards do not enhance safety, then there is no safety issue, and the world's airworthiness authorities can retire, saving quite a lot of money,

Yes, a completely wrong focus. RAAus safety has actually developed rapidly to an outstanding level, as shown in the attachment in question; and it's not a very tricky bit of statistical analysis to see that RAAus needs to get real about maintenance, about 3 years ago would be perfect...

AOPA are a sector of industry, and have their own perspective. The more historical one's perspective becomes, and the greater the understanding of the legal principles, the more irate one becomes. For example, CASA's authority is enforced by bullying, to wit deprivation of livelyhood. This is unconsciable, and an affront to common (constitutional) law, yet remains a holy writ. Perhaps AOPA don't want to be bullied...

A very grey area; please ignore the spruik in the tail of the attached doc, and look at what the stats do (and don't) indicate... Becoming Safe, staying Safe.pdf Becoming Safe, staying Safe.pdf Becoming Safe, staying Safe.pdf

Firstly: We are the only ICAO signatory in the world, whose National Airworthiness Authority DOES NOT have immunity from prosecution in the course of their normal affairs - thank you the Balmain pig PM, Paul Keating. As a result, CASA has had a degree of arse-covering since 1988. Secondly, the several attempts to introduce "and foster" into the Act have all failed, thanks to luddite fools in parliament or the senate. This is a matter of record. Thirdly, Dick Smith did (and still, I suspect, does not) understand the link between "airworthiness" and engineering judgement; so Keating - via Brereton - used him to gut CASA of most of its engineering heritage. Since then, with the exception of Byron, Ministers have been appointing fighter pilots to direct CASA. In parallel, since Anderson's era, our NAA has abused its discretionary authority, flouted the constitution, and exhibited a culture of arrogance that began to lose the credibility of supporting expertise in the late 1970s. Currently, CASA officers are trained in their responsibilities under the Administrative Decisions Judicial Review Act 1988, but completely ignore their KNOWN responsibility towards natural justice, when directed by the head fighter pilot. There is no system of internal checks and balances, because CASA has neither the economic resources nor, it would appear, the moral resources* to successfully implement systemic change to the culture. It must be made clear that, at any point in time, CASA has (and has had) a significant number of highly motivated, well educated, and highly capable people, of high personal probity and good intent, who find themselves virtually paralysed in any attempt to reform or improve, due to the pervasive nature of the post-Anderson culture. CASA firmly believes that it has a near-divine responsibility to tell people what they can't do in the interests of safety, and that appointment to a position in CASA automatically imbues the appointee with moral authority, irrespective of the actual expertise. Within this culture, the few persons I have experienced who are persuing personal agendas have virtually no limits on their ability to negate the positive efforts of the most of CASA, most of the time. *The structure and methodologies of CASA do not allow the officers any discretion to speak of, in allowing their personal probity to inform them in matters of regulatory judgement; I have a letter stating that CASA has a team of lawers to guide officers in making each regulatory judgement. it's not a lawer's bloody job to make engineering judgements, but this is the outcome of Paul Keating's all-embracing comprehension of the economics of management of hardware. Now, CASA is - pointlessly, because Australia is very much not the US, OR the EEC - trying to emulate those NAAs, but at the same time do not have the corporate guts to recognise that the bulk of aeronautical expertise in Australia is in private industry, and can be used as a resourse to fulfil our ICAO obligations. because, as a member of CASA Engineering Services said to me (in personal conversation), "you can't trust pilots". John McCormack said to me, personally, face to face, in a room full of the operators of Approved Aircraft Maintenance organisations (LAMEs to a person), "what do these guys know about airworthiness? Nothing!". He was a fighter pilot (Mirages), so he knows. We have a few career politicians, who have been exposed to CASA for so long, that they realise that the furphy of CASA's untouchable expertise is a Furphy; and we have a few relatively young, generally independent MPs, who are sufficiently iconoclastic to consider that CASA may, indeed, be somewhat less than perfect. Well, if they fix the frigging laws, so that CASA people can do their bloody jobs without looking over their shoulders all the time; admit that Australia deserves an aviation industry, and include "foster" as a prime directive in the CAAct; allow the reformers in CASA to work, under a director who (like Byron) was never a fighter pilot; and outsource airworthiness as the FAA so successfully has to DERs (who are members of the FAA when DERing, even if not employed by the FAA - make THAT work in Australia!)... then, in about3-5 years, our industry might start to recover. Otherwise, we need to really work the trans-tasman bilateral, and move our industry to New Zealand.

Okay... the heat carried away by moving air (forced, i.e. faster than convection) varies as the velocity to the 0.78th power; so increasing the velocity increases the heat transfer, but less than proportionally. Now, for a circular (finned) cylinder, a duct of ~1.2 times the sectional area between the fins (on both sides of the cyl), blending smoothly into a pair of arcs that start above the tips of the fins and converge as they wrap around the cylinder, then blend into an exhaust of 0.8 times the inlet duct area, will give near perfect cooling. This is because, as the cooling air gets hotter moving past the cylinder, the contracting passage speeds it up enough to maintain virtually constant heat transfer. The baffles on Austers, and to a degree on Tiger Moths, come close to this ideal. By contrast, the "let the air in over the top, then hit the firewall and drop - stunned - through the fins, rattle out of the lower cowl any old how" is pretty lame. The NACA C-75 exercise shows at least converging inlet baffles / ducts, and an inverted "V" to turn a bit of the outflow past the back of the cylinders must be presumed. Given the known advantages of streamlined struts - the airflow doesn't separate - compared to cylindrical - it does separate - I do not understand how anyone expects cooling air to adhere to the "back" half of a round(ish) cylinder without a great deal of help.

Look fowards to hearing more - technically, cooling is an installation (airframe) issue, not an engine issue - eg the baffles on a Continental O-300 in a Cessna 172 are a Cessna product, not a Continental product. I do not know CAMIT's focus on the redesign, but I assume that the subcomponents and detail design is now virtually flawless (or they mean to find out and fix it immediately!)...

No worries. One of the issues to consider is this: with a non-constant temperature around the barrel, the hot barrel deforms, generally to an egg shape. The piston & rings wear to this shape. The wearing process obviously ups the friction, but - less obviously - as the rings creep around the pistons, they leak a lot more than they should, losing compression, increasing temperatures, and generally being pests. From what I've heard about old Jab engines, they most all have issues with this.

No; but I'll make a few comments anyway! Hirth - back in 1917, Hirth were working on contra-rotating rotarys (from memory), with astonishing power to weight ratios etc - real innovators in the aero engine field. By 1987, Hirth were a quiet little shed across the valley from a huge outfit called Bombadier (Rotax), and had not much of a reputation in ultralight use. In the '90s, Hirth retooled with a bunch of CNC machines, and redesigned everything. From the few I have scraped acquaintance with, the new millenium ENGINES seem very sound, provided you treat them like two strokes... but the PSRU (prop gearboxes) appear designed with no consideration of propellor gyroscopic loads. I was privy to the basic details of a Hirth gearbox, mounted on a motorglider, the prop of which decided to take up a solo career - after about 27 engine hours (or was it 37? less than 40, anyway...). I'd be willing to consider flying behind a Hirth engine, but unless the gearbox design has mutated drastically in the last few years, I'd roll my own PSRU. MZ used to have a good rep in the noisy small motorbike field - ~40 years ago. From your hotlink, it looks believeable, but that output shaft & redrive mount don't look fit for more than about a 50cm balsa prop to me.... Bear in mind that the gyroscopic design loads from a 54" Jabiru prop on a Corby Starlet contribute something like half a ton to the most critical engine mount loads...

NACA Report no. 511 gives much more info about the temperature distribution around a cylinder.