Bob Llewellyn

This is all great discussion and a no doubt maintinance is an issue but how will requiring endorsements for each aircraft as proposed help that?

I'm not condemning RAAus pilots at all. My only point is that I believe your logic is damaged by too many assumptions. Your conclusions might be 100% correct, but you don't show the link.You calculated the result if RAA had the same human factors accident rate as GA, and got an implausible result.

 

You calculated the result if RAA had the same hardware failure rate as GA, and got an implausible result.

 

From this, you concluded that the result was somewhere in the middle, and picked the number 3. Why not 2? 4? 1.5 (i.e. 50% higher)?

 

Isn't it possible that the data you are comparing are not directly comparable i.e. you are comparing apples with oranges? In fact, if you are comparing all GA I am fairly sure they are not directly comparable.

 

Your conclusion flows directly from the number you assumed, but you show no evidence to support this number, other than it is likely to be somewhere between 1 an 14.

 

I even have doubts about 14 being implausible. If the majority of GA hours are commercial, would it be that unlikely that GA charter has a 95% lower rate of pilot error accidents than RAAus? More information about the original data is required.

 

I don't have an analysis of the data. My official position is "I don't know". But you don't need to be a photographer to know if a photo is out of focus. Likewise, being out of focus doesn't mean it's not a photo of what the photographer says it is. But if you can't tell, the photo is no use.

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.

Thanks for your comments guys. Now the come back.TP, yes too much prop blanketing and I intended for a more pointy rear end but ran into two problems. First was that I've been experimenting with a new addon to Google SketchUp called Curviloft. This program adds a skin to per-constructed 'formers' or stations. It sounds easy but in reality, if you don't get the stations right, the skin takes on all sorts of weird forms. I lost control quite a few times and my design suffered somewhat. I'll be trying for a better shape shortly. The second reason, and more believable is that, for mechanical reasons, I don't want a long prop hub. Therefore I'm stuck with close proximity of prop to fuselage. As you say in your second post, a ducted prop etc is too far away from what I want so no, not going that way.

 

The possibility of losing the boom and tail assembly has been raised in many discussions on this configuration and my basic answer is,

 

a) build it strong, even at the expense of weight and speed. Choose bearings that will be under running their normal speed and load specs.

 

b) Fit a ballistic cute. As far as I know, there's no previous design using the bearing method that I've designed. Most mid prop systems had a small bearing on a thin tube which necessitated one or two extra stay to hold the tailplane. Again, not what I want.

 

Bob, yes my boom and feathers was too small. When I first set out on this redesign, this assembly was the first to be completed. I was working from "this looks right" point of view. Later, the fuselage turned out bigger than I thought and I never really looked closely at the comparable sizes. I see now where you're coming from so I've scaled up the rear end and, I've taken 10 degrees dihedral (anhedral? not in dictionary) from the horizontal stabs. I knew that the 120 degrees between surfaces was wrong but, being pig headed.............

 

Re shaping the fuselage will help re vortex separation etc. In a perfect would, I would go as far as a pair of contra-rotating props to cure many concerns. I personally think that c/r props should be allowed if on the same axis. Just call it a single 'Propulsion system' not 'twin props'. Yes I know, hellish heavy, expensive and complex..........but doable.

 

As for the stall comments, I don't think it will be as bad as you intimate. the prop only covers about 16% of the total wing span and most of that is that section through the fuselage. Actual wing surface would be about 7%. I have more concerns about the same area having a negative influence when the flaps are lowered. Note that I have a 3 bladed prop so only one blade affected at any moment in time.

 

I have looked at Taylor's Mini-imp but even he had trouble, mainly in the long drive shaft required. Again, I'm not looking for a clone.

 

Would morphing control surfaces need mass balancing? Birds don't have them Guess that's going to be a wait and see type of thing. A more considered answer is that most control surfaces are hinged on a central axis and need some form of dampening from time to time. My system can't flutter as it's driven from both top and bottom simultaneously, side to side in the case of the rudder, and will be much stiffer than conventional. To appreciate that statement, take a piece of paper and fold it in half. Hold the open ends to form a control surface and then push/pull to activate the curve. That's the basis of my design. There is one big drawback however. The surface must have a constant X-section which negates tapered depth wings and tail plane surfaces. Looks particularly ugly on the tail surfaces unfortunately.

 

Under-carriage will probably be wood and fiber-glass composite. Why do you specifically ask that? Ah, thinking of prop strike in the case of a hard landing perhaps. The idea is not to land hard

 

Bearing in mind that all things can change, does this look better?

 

[ATTACH]27097[/ATTACH] [ATTACH]27098[/ATTACH]

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!

The way it's applied in this country.................... could be?There are always blips and dips in stats that hide trends, or make non-existent ones.

I should also mention that when I say some training could help.......I mean as long as it's not an excessive burden, in which case we'll all be safe, because the only way to afford to aviate will be on a 737 with a red rat on the tail.

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...

Which aircraft allow you to inspect everywhere? All aircraft have some areas that can't reasonably be inspected.But what I said was: "Some maintenance is obviously necessary. What I am suggesting is that if you design so less maintenance is required, safety and reliability are improved."

 

Surely you would have to agree with this? Don't engines with thousands of hours TBO instead of hundreds increase reliability?

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.

Your RAA hardware failure rate is based on the assumption that the RAA human factors accident rate is 3x that of GA. Where do you get that figure? You started with equivalent rates, which gave 96% of accidents caused by hardware failure. Then you seemed to conclude that 3x gave a reasonable figure. Where does 3x come from, if not from the result?If the GA figures include all commercial GA flying, under an AOC and overseen by company SOPs etc. I would be surprised if the RAA human factors accident rate was only 3x that of GA. Since the figure translates directly into the result, you can't just pick a figure and assume it.

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?

I'm not arguing for eliminating maintenance. Some maintenance is obviously necessary. What I am suggesting is that if you design so less maintenance is required, safety and reliability are improved. Part of that is because whenever maintenance occurs, errors are possible. Most people who have been involved in aircraft maintenance could give examples of problems that occurred after maintenance - but to repeat, I am not arguing that that means the maintenance should not have occurred.

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?

Quite right Powerin, single seat flying will always be considerably less costly than a two seater because you can use small engines that are plentiful and cheap. Not only does the small engine cost so much less but the airframe can be much lighter since it doesn't have to carry so much weight and it doesn't have to resolve so much power. Even so, single seaters with tiny engines still become exponentially more expensive as you go faster because you need to use exotic materials and manufacturing methods to get the weight right down, and the airframe very smooth to reduce drag.In my previous post I was concentrating on the two seater aspect since it would appear that most people want a two seater even if they often fly alone. It provides the chance to take spouse, friends and family for a flip and also to introduce others to flying. And most importantly, when flying alone the second seat provides space to carry extra fuel and baggage which makes the aircraft far more useful. So, as I see it, in answering the "What can be done" we need to be looking at what can be done to make a two seater less costly than they are at present, and to get reasonable comfort and performance for the least cost.

 

I've been through a lot of this exercise fairly recently with a thread called "Cheap Two Seater Anyone", so I've already discovered a lot of the cost drivers of two seaters when compared with single seaters, and I've also worked through all the various construction methods on another site, and ran polls to determine which kind of construction the majority of people would favour if all or part of the assembly was to be homebuilt from a kit.

 

Having run all the costings, both for materials and for CNC parts manufacture, for the biplane I devised as part of Cheap Two Seater, I was somewhat surprised at the end of the exercise to discover that the parts count was higher than most other methods and the amount of CNC machining made it an expensive kit proposition. The main advantages were that the materials were all commercial grade and the whole thing was pop-riveted and bolted together so almost anyone could assemble it easily enough from a box of supplied parts and sub-assemblies.

 

The Cheap Two Seater was also designed to reduce the costs and complications of ownership by being quick folding to a size that can be trailered or stored in a 20ft/6m shipping container to avoid hangarage costs. What I saw as the least complicated, lightest and strongest way to achieve that and also have side by side seating was to make it a biplane with a high mounted engine. Whilst folks were very generous in their comments it was clear that the whole concept didn't set anyone on fire with enthusiasm and I assume that the 'difference' of a biplane and high mounted engine were the major factors which lost people. After all the majority of people want the conventional layouts. Another factor, perhaps, was the limited performance offered by the configuration due to its high drag both from being biplane and also the frontal area due to being side by side seating.

 

From what was learned from that exercise, and the polls on the other site, there are some facets that are worth retaining for a different design which is also aimed at lower initial cost and lower ongoing costs of ownership -

 

There is a definite cost benefit in using commercial grade materials, albeit with a weight and associated performance penalty but at the speeds we are talking about those penalties can be kept fairly low. From the polls the gusseted/pop riveted aluminium tube, fabric covered was by far the most favoured homebuilder's method because just about anyone can do it accurately with only basic tools. So those two aspects of the Cheap Two Seater probably have to remain, then we have to address the performance and configuration issues while still retaining trailerability, two seats, smaller/cheaper engine (i.e. not a 100hp 4T) and an enclosed cabin.

 

There is a big weight/structure, and therefore cost, saving if the seating is tandem rather than side-by-side (SBS) so it's worth giving long and hard thought to just how important SBS seating really is. If you mainly fly alone but want to take a pax sometimes then taking advantage of the tandem cost reduction is a good way to go. There is also a really big advantage of tandem seating that is often neglected and that is that both people have excellent visibility out of both sides of the aircraft and that is also why tandem is favoured for any ground-related flying such as photography or station work. And when flying alone it's easier to turn an empty rear seat into a baggage compartment by removing the stick, than it is to turn the right seat into one.

 

Looking at the performance aspects you only have to compare the Thruster Gemini with the Drifter or the Piper Pacer with the Cub, the tandem arrangement with its much narrower fuselage and consequently much less severe pressure recovery aft fuselage curvature wins hands down. The Pacer flies slow, the Cub flies slow and relatively fast as well, the Genini and the Drifter compare with each other similarly.

 

A tandem monoplane is always going to be a fair bit harder and more time consuming to fold than the Cheap biplane unless very sophisticated and probably expensive methods are used, but it needn't be too bad. The important thing is that it should be able to be accomplished by one person without too much effort and in windy conditions if necessary.

 

If we are to accept a slower plane than we'd really prefer to have then we need to satisfy ourselves with some other aspect of that plane that is just as appealing as the speed would have been. Of the types that I've flown there's no doubt that I've had the most fun in aircraft that could go where others couldn't. They allowed me to get onto isolated beaches, to untouched fishing spots, onto mountain tops and deep into remote valleys. For any of that a helicopter is best but since we're talking 'more affordable' we really need to look at what can be done for STOL ability without unduly affecting the nice cruise speed of our narrow tandem machine.

 

There's a small plane that was recently brought to my attention that a fella in USA built using some of the parts of an early Piper Cub. After his rebuild and modifications it's still a (close) tandem two seater and it won the STOL championships at Valdez (Alaska) last year. Some of the competitors there had spent half a million on their plane modifications and much to their embarrassment Frank came along and blitzed them with a budget toy. It's the yellow 'Lil Cub' at 1:00 min in the video and in the pics below. It has some pretty clever aspects to the design but there's nothing difficult about it. And Frank Knapp, who built and owns it, reckons it's more fun than anything else he's ever flown. He doesn't ordinarily use it for competitions, it's his local explorer the rest of the time.

 

I must admit,I'd love to get my hands on some drawing and specs for Drifters.I see more clearly what you are saying now, and I agree some maintenance training can't hurt, but I suspect it will improve things very little.

You're probably right, I just see problems with the stats you are using. Adjusting the assumptions until the results are within expected bounds isn't right.I would be more interested to see (and much more convinced by) stats that showed RAA accidents vs. GA private flying accidents, for the same years. Even then you would have doubt about the effect of RAA vs. PPL training, unless you had the figures for how many of the RAA pilots had a PPL and could adjust for that.

The problem with your stats is not with the RAA portion - if you want to compare total RAA fatal accidents, I would expect the RAA stats are adequate - all you need is hours vs. fatal accidents. However, if you want to compare it to GA you need to separate out the portion of GA that is equivalent to RAA flying, e.g. day VFR private flying. This is, I think, difficult.To address your points:

 

1) Airworthiness Design Standards reduce the accident rate;

 

Initially I'm sure they did. Are aircraft still designed to the minimum required by design standards? Do more design standards reduce the accident rate more? How much is enough? Many would argue that airworthiness design standards currently prevent innovations that could themselves significantly reduce the accident rate, e.g. compare non certified synthetic vision features and prices vs certified.

 

In most cases it is the requirement to produce safe and reliable products that drives design, rather than design standards e.g. I understand Lycoming engines far exceed the reliability required by design standards.

 

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;

 

I'm not sure that necessarily follows - really, it is the question that we are trying to answer.

 

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;

 

I wouldn't be surprised if this is true, but I don't know either way. I don't think the figures you present demonstrate that.

 

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;

 

I would expect that is true. I also suspect, paradoxically, that maintenance also causes many of the hardware failures i.e. they prevent wear related failures, but generate maintenance error failures. The relative rate of the different types of failures would be interesting to know.

 

The best way to reduce failures is to reduce the amount of maintenance actually required. Design standards and inflexible maintenance schedules can work against this. RAA aircraft in theory are simpler and require less maintenance - which was the original basis of the current rules.

 

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;

 

Must? Why? If they are simpler or designed to require less maintenance, it is still possible to be more reliable. Do modern cars have more failures per hour of operation than GA aircraft, due to the lower qualifications required for car mechanics?

 

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.

 

True, although the overall effect depends on the baseline level.

 

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

 

I suspect a lot of fat could be cut from the worlds airworthiness authorites without significantly affecting safety.

I think that you are correct in saying that the airworthiness standards improve safety, that really cannot be argued, but I do think that the statistical methods used are somewhat skewed in the direction that the author wants them to be.No, the RAA accident reporting is not going to yield any hard information, but, rather than manipulate stats to say what you want, would it be more reliable to use a probable cause, for example, it would be realistic to suggest that an aircraft stalling as it turns from base to final, or flew into ground when it was dark, was a human, aircraft handling problem, rather than say "we can't be sure it wasn't maintenance, so lets make new maintenance rules"?

We seem to have had quite a few of these sorts of incidents of late. I know that we can't rule out maintenance as a factor, but I would consider that human factors is a more probable answer for a significant proportion of our incidents. We already have HF training, but in it's current form, I doubt it has done much, but that's just a personal viewpoint based on my experiences in aviation maintenance.

 

I'm only going from memory, but if there are actual stats that clearly show maintenance is an issue, bring 'em out, I'd love to see 'em.

 

Good maintenance certainly can't hurt, but I doubt very much that it will make much of a difference to the actual issue of the govt wanting people to stop hurting themselves in those dangerous machines.

 

Those who prefer certified aircraft, with certified maintenance have that option already.

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.

“Crinkle, crinkle, little spar –Stressed beyond the yield-point far;

Up above the World so high,

 

Bits and pieces in the sky . . .”

 

Would the dreamers on this thread please look up CASR Part 21 subparts G and B, plus 21.186, and learn what is actually involved in bringing an aircraft to market?

 

The parts cost for a Drifter-type aircraft are only a small part of it. Firstly, there is the business of getting a Type certificate. That requires full drawing coverage of the aircraft to acceptable aeronautical standards, plus building a structural test specimen and a flight test srticle, and proving that they meet the structural and flight requirements. There are also a slather of other design requirements, dealing with things like fire resistance, crashworthiness, and a thousand other matters.

 

Once a manufacturer has done that, he can apply for a Production Certificate. To get that, he has to have the necessary tooling (and means of verifying that it is servicable), a means of purchasing the correct materials and keeping them segregated, so only the correct parts & materials get used, plus a quality assurance system. Once he has that, he can start to produce aircraft that are capable of being issued with a C of A. Only then are they saleable products.

 

This process involves a large, high-risk investment, both in time and cost. Part of that may be borrowed money.

 

So by the time the would-be manufacturer gets his product to market, he has a mountain of debt of one sort or another.

 

What is the incentive for him to build a product that has a very limited market, and sell it for peanuts? Come into the real world - nobody in his right mind is going to do that.

 

Bill Whitney gave a figure for the actual cost to manufacture a light aircraft - he quoted $5.50 for every dimension on a drawing. That was from his experience with the Boomerang. Do you people have any idea of how many dimensions there are on drawings to build a Drifter? AsI have previously stated, it has nine times the parts count of a Jabiru - and whilst a lot of those are standard parts, a lot of them have to be made.

 

The manufacturer has to pay off his initial investment, and then continue to stay in business so there will be spare parts for his product. Remember, the spares have also to be manufactured under his Production Certificate - or somebody else has to go through a similar process to get an after-market spare approved.

 

There is only one way around this, and that is DIY. So what you can do, is set up a shop in your backyard and get on with it. This whole thread is a piece of cargo-cult wishful thinking, and really a complete WOFTAM. The answer - such as it is - is literally in your own hands. Learn to use them. That's why you have opposable thumbs.

Oh blast, Victa don't make the engine anymore.

It sounds rough, but these days unless you have a mate to lend you an aircraft and pay the petrol the days of prices like this are gone. Start adding the costs and you soon see why it costs so much. Even on a cheap plane with minimum maintMy costs ignoring depreciation except for engine replacement. Based on 200 hours pa.

Engine $13 hr

 

Maint & Parts at least $12 hr if nothing breaks down and every service is straight forward

 

Insurance $15 hr

 

Hanger $8 hr

 

Fuel $34 hr

 

Total minimum cost $82 hour

 

Sorry but people wanting aircraft at $50 - $80 per hour when they dont own the plane are dreaming. And even owners will find it tough to come in under $80 hour. Especially if they are honest about the true costs.

 

Some with hangers and no insurance might do better...

We're all entitled to have a jaundiced view of course, but I don't think the fatality statistics would support your argument.Certainly some of the earliest ultralights weren't built to last, the vibration from single cylinder engines flogged out bolt holes and loosened rivets after a few hundred hours but in recreational aviation that was usually quite a significant number of years. And whilst you might have been horrified by some of the Thruster componentry I don't recall a single instance of a structural failure of them so I think we can presume that the designing engineer did his job just as well as any of those who worked on the types of aircraft you consider to be 'competent'.

 

In the lead-up to HORSCOTS there were certainly a lot of crashes but only a tiny proportion of them were due to structural failures, the vast majority were due to the people who were flying having a severe lack of knowledge of mechanical flight dynamics due to the lack of compulsory training to fly those types.

 

Whilst I'll happily admit that I haven't done the statistical analysis to support my statement, I'd nonetheless feel quite confident in saying that compulsory training and 'competent' aircraft haven't done a thing to improve the crash, injury and fatality statistics because whereas we once had incompetent pilots flying incompetent aircraft, at least they flew very slowly and therefore crashed slowly so the incident was survivable and the aircraft was often repaired and flown again. Instead we now have ageing and supposedly competent pilots flying aircraft that are in many cases far too 'competent' for them and the kinds of crashes that are so very frequent of late clearly indicate to me that the piloting skills are way behind the performance of the machine. The speed and low drag nature of these slick machines means that small piloting errors often result in crashes and a high proportion of the crashes are fatal.

 

I think we've gone way past 'recreational' flying and well into the territory of 'ego massaging' aviation with old blokes (as I am) getting their belated Walter Mitty moment because they can now afford the slippery ship they always dreamed of back in the days when they had half a chance of keeping up with it's performance level. And of course there is a good proportion of the current 'competent' fleet being used as workhorses on the land and daily transport for professionals, neither of which can be described as recreational use but at least they fly more hours and that currency probably results in a lower crash rate which helps to improve the statistics for weekend flyers.

 

Just my similarly jaundiced 2c worth [ATTACH=full]26953[/ATTACH]

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.

I'm not sure that any conclusion can be drawn from the stats as presented. When you apply a reasonable assumption (RA and GA human factors accidents happen at a similar rate) and come up with an unreasonable conclusion (96% of accidents are caused by aircraft failures) I think it points to a problem with the original figures. You then adjust the assumptions (rate of human factors accidents) to get a more reasonable answer for aircraft failure accidents. This doesn't seem right to me.Am I correct that you are comparing GA in the 1960s to RA in 2000+?

 

To get any valid conclusions, I think more variables need to be understood. What types of flying are included in the GA figures? Are there significant differences in e.g. age and experience of the 2 pilot samples?

 

It would be interesting to compare GA vs RA accident rates for GA private pilots only. Or pilots who flew less than 100 hours in the previous 12 months. That would give you are more comparable sample. And I think the comparison should be for a similar time period, not 40 years apart.

 

It's tempting to say "Well, this is the best data we have, so we will see what conclusions we can draw from it" but sometimes the answer has to be "Not enough information".

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,

Well, that surely indicates that introducing individual type endorsements into RAA training is about on a par with buttering the edges of a slice of bread.

You should see the AOPA submission to the enquiry. It was nowhere near as good a submission as those here and I am embarrased to say I contributed to it and they represented me.

I have to agree. Way back, one had to have a separate endorsement in one's log book for each individual aircraft type. That was abolished in the late 1960's if my memory serves me correctly. Ever since then, in GA there are "class" endorsements - you need one for tailwheel, C/S propeller, retractable gear, floats, hulls, low flying, glider towing etc; but if you have, say, a glider towing endorsement in a Super Cub, it also holds for an Auster or a Pawnee or a Cessna 180. If the RAA consider it necessary to take this retrograde step, that's an admission that the RAA training system isn't producing competent pilots, I'd say.

Becoming Safe, staying Safe.pdf

Becoming Safe, staying Safe.pdf

Becoming Safe, staying Safe.pdf

Consider this: " governments gradually employ more and more ambitious elites who capture a greater and greater share of society's income by interfering more and more in people's lives as they give themselves more and more rules to enforce, until they kill the goose that lays the golden eggs"You would think Ibn Khaldun knew about CASA, but he wrote this nearly a thousand years ago.

Personally, I think that if CASA were abolished, we could have a dynamic aviation industry, but alas as a country we are too stupid to consider this. We have Jabiru despite, not because of, CASA. Could it be that you would be better off developing new aircraft in a less over-regulated place?

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.

I was told it was done on a j230 at Cessnock by a well known L2, this was a while ago and I never followed it up to see how it went later but at the time he said it was good. I can't see why it wouldn't give better cooling.

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.

there is one of the new camit motors at my airport i seen it today. it had an alternator and black barrels but looked like a jabiru motor other than that. the guy said it had 20 hours on it at the moment. he said that he had 2 mates in qld that have them too with a fair number of hours so it wont be long before some reports come back if they are no good (or good for that matter)

Great stuff there Bob. thanx.

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.