Oscar

OK, this is a subject that anyone who has a 'glass ( mainly, Jabirus) / other composite structure aircraft ( mainly Carbon fibre Euro 'fantastics') perhaps needs to understand. Caveat: I have followed Project Binky for several years, and as someone who has built several racing cars and done serious modifications for road and rallye cars, I am in total AWE of what they are doing. As a fellow Pratchett (Binky is Death's horse in Pratchett books, and acknowledged by the guys as the inspiration for the name), and also Wallace and Grommit ( watch the series and you'll see their attachment there), they are kindred spirits. So this is NOT any kind of negative rant against what they are doing! A composite structure is a combination of fibres (of glass, Carbon fibre, kevlar and some other weird and wonderful materials, particularly aramids), and a resin that holds those fibres together so they can take out loads. By comparison with the fibre matrix, the resin is relatively 'plastic' - but it grips to the fibres well and doesn't deflect much, so the loads being taken out by the matrix are shared well by the entire fibre mass. The resin also provides 'toughness' - resilience to local shock loads. That comes at a cost of weight to strength: for pure strength, the resin/fibre ratio by weight is around 55%. It can get lower, with techniques such as Vacuum infusion. For high-strength, low-weight composite structures, the designers take into account the fibre mass directions: you can find bi-xaxial, tri-axial and quadraxial fibre cloth, where the strength in one axis may be far higher than the strength in a secondary or tertiary axis. The fibre orientation of the matrix may be a critical part of the design equation. We are all familiar with the 'reo' that is laid into house slabs: it is there for a reason - it adds strength to the concrete (which we might like to think of as the 'resin', though that is not the best explanation.) When high strength and low weight is required, carbon fibre is fairly much the preferred option. That is because the carbon fibres are very, very 'stiff' and strong. But that comes at a price: the structure is increasingly brittle, and non-damage tolerant. The OTHER price, is increased production cost: not just the cost of the C/F cloth but the entire production cost, often requiring autoclaving ( high temp., vacuum conditions) requires very large investment in moulds and processing equipment. Your average, polyester-resin and chopped-strand mat laid up yacht, bounces off wharves. Pure C/F Maxi-racers and America's Cup yachts break.. because the composite matrix - the resin AND the reinforcement - become overstressed. The guard extensions for Project Binky were done to produce quickly an acceptable shape ( and you can note that the Lycra did not really conform to the compound curve, but required a lot of bog-filling..) The only 'structural' requirement for those guard extension, is the ability to not be damaged by stones thrown up by the tyres - and the Lycra is fine in the use for a very 'tough' against impact, but almost zero 'strength' requirement.

Mass balancing of a control surface rarely means that it is 100% statically balanced at the hinge line. A degree of 'out-of-balance' is in fact required to dampen the combined effects of kinetic energy and moment arm AND aerodynamic effect excitation of flutter - with regard, as you have said, to the stiffness (and therefore harmonic period) of the structure to which they are attached. Recent developments in computer modelling may have made all of that predictable, but until fairly recently it has been ultimately a matter of test-flying. AFAIK ( but I am most happy to be better advised), it is still the 'rule of thumb' in the FARs that no more divergence than 5% to the demonstrated 'flutter-free' configuration to a control surface is allowed without full flight testing for any modification to the control surface. By way of example: when I changed the fin and rudder of my LSA55 to use a UL450 ( also used on the J120) fin and rudder, I found the supplied rudder was a bad fit to the fin. To rectify that, I needed to split the rudder spar and widen it at the top, necessitating a new spar moulding and some additional insertion structural changes. (It was done in consultation with the aero-engineer who did the structural justification of the LSA55, Alan Kerr, and the aero-engineer who did the certification flight testing, Dafydd Llewellyn). When all the mods were done, the change in balance was less than 3% - and by way of explaining relevance: the additional spar moulding, which sits around 45mm behind the hinge line, was about 60 grammes! Seriously: a heavy coat of new paint on something as large as a full-span elevator can upset the mass balance. This is absolutely NOT an area where one should just wade in with some well-intentioned changes, without expert advice.

Nev:, Bruce is correct, the trim cable IS attached to the elevator horn. In the fairly early days of Jabiru flight testing, the elevator cable became detached at the forward clamp (under the pilot's elbow), due to inattention in assembly and was landed without drama (apart from some excited chatter coming from the ground..) at Bundaberg on trim only.

The simple answer to the question: 'Why is private aviation so different?' lies in the media attention that every aircraft crash receives. Even, sometimes, a 'precautionary' landing is treated as a 'crash' by the media... There is a massive dichotomy here for us and it encompasses almost every aspect of our activity: legal, financial, utility. On the one hand, we ask for decent access to airspace, facilities etc. We ask for the possibility of insurance for our sometimes $150k-plus aircraft at reasonable rates. We ask for a decent level of professional back-up, in the form of standards and maintenance to standards, so that we can actually enjoy our activity in the expectation that we will NOT be killed or injured, and that we can take our loved ones, our friends, and just those who would like to experience flight up with us without deliberately placing them at some huge risk. On the other hand, we - or at least a considerable portion of 'we' - seem to object strenuously to any form of restriction on our right to do what the bloody hell we please, because it is 'our choice'. Now: a caveat here before I proceed further: should I ever decide to attach ten weather balloons to a plastic deckchair and add my ceiling fan to my whipper-snipper and go fly around my property at under 500 feet, and some CASA bastard comes out to stop me, I WILL be removing my gun from its safe and perforating his (or her) vehicle and quite probably introducing spasm incontinence from close exposure to supersonic lead projectiles. However, I will ALSO have told my descendants that 'Papa may not be coming home again' before I take-off, and left a signed and witnessed statement for them to provide to the media that I fully understood the risk involved in being a F-wit and my demise was entirely due to my own stupidity... The whole and only point of crash investigation, is to determine the cause(s) and thereby attempt to remove such causality for the future. Since we cannot legislate effectively against stupidity - fools are always more innovative than legislation can predict - all we can do here is enhance the envelope of protection. High-quality aircraft crash investigation, with appropriate follow-up - is a major tool in enhancing the envelope of protection. RAA management receives a vast amount of negative opinion - and it is certainly the case that RAA resources are inadequate to do expert investigation of all crashes. BUT, I submit, the expertise in RAA is not inadequate: I submit the case of the Morgan Sierra crash at Moruya, where a decent level of forensic investigation showed that a totally faulty securing mechanism for the elevator control killed two people. Rectification of that will save lives. Another example: A Thorpe T-18 crash, quite some years ago, where a fully-qualified and current airline pilot was killed in what was initially classified as a CFIT incident, with a preliminary conclusion of a medical / fatigue cause. I won't go into all the details, but an expert crash investigator and aero-engineer was called into the Coronial Inquiry by the Police and he found that the cause was in fact CO ingestion into a negative-pressure cockpit due to a fine crack in the under-floor area just aft of the exhaust outlets. It took a secondary autopsy to examine the CO levels in the body to show that the pilot was dead, probably many minutes - possibly as many as 30- before the properly-trimmed aircraft hit the ground due to fuel exhaustion. If we - as a group - of Recreational Aviators want to be treated as 'responsible' members of society, then we MUST also accept the constraints of membership of society. I absolutely believe that there are many refinements of the 'rules' that we operate under to qualify us as 'responsible', 'safe' etc. but we need to try to refine the rules, not simply ether accept OR reject them.

HITC - fantastic work, as always. But a small correction to the above: the time to double the rate of change of heading MUST exceed (or at least be no less than approximately) 10 seconds. Easy mistake to make when typing, to add the 'not' - ( I suspect we are conditioned to write 'must not' more often) but when you think about it, it's obvious - the aircraft MUST NOT screw itself into ever-faster turning at a rate too fast for the pilot to catch up with! I think you got the first version from DL, and he corrected it soon afterwards - and in long emails it's so easy to miss one changed word - but that word is important here! If anybody is thinking of trying to check their own aircraft out of curiosity, or looking for improvements in stability / flying characteristics, I urge them to get advice from an experienced test pilot as to how to carry out the tests safely. Test pilots do not - despite the romantic notions shown in some movies or written in some books - just blaze off into the ether and 'wring her neck to see what happens'. There is a reason why they wear parachutes and have spin recovery chutes ( and nowadays, BRS as well, if possible) - because bad stuff sometimes happens. Ask Keith Engelsman - he's had to use a spin-chute in anger..! And it's worth remembering, Cessna lost TWO (I believe) Skycatchers in testing, so if Cessna can't always get the design right, I wouldn't bet on anybody else always getting it right every time, either - just personally.. Edit - sorry about the vast use of red text, but I can't seem to change it as an edit.

Melocco Bros? Wombeyan Caves marble was used in the surround to the Tomb of the Unknown Australian Soldier. Used to travel that road going from Mittagong to Mt Jerrong and back to help a mate on his Pine plantation on the weekends in the late 80's ; at night, an ex-Aus Post Toyota Hilux ( the orange ones, first model, with half a candle for headlights); gave it up because too many fwits travelling at 10 kph frightened out of their wits, going to the Caves to camp for the weekend, who never moved over to let anybody past. Faster to go to Goulburn and up through Taralga. As a member of the Jerrong- Paling Yards RFS unit, have fought over the years many fires in that general area, from the bottom of the Blue Mountains National Park to as far as Yerranderie, including five times to keep the Bindook Nav. Station safe ( some b@stard was lighting them up every couple of years at one stage), and until you've been in a Cat 7 fire truck driven expertly by the guy who maintained the roads ( to use the term lightly) around there for years and knew every damn corner so could travel at 80 - 100 kph drifting the truck everywhere, you don't know terror. That whole area is one that anybody flying over in an RAA aircraft who does NOT have sufficient height to glide to a clear landing site is a damn fool and frankly does not deserve a rescue attempt in the case of a crash if not carrying an EPIRB. That may sound harsh, but the terrain and the bush coverage would swallow up anything less than a heavy with no trace from an air search and trying to cover any area off the tracks on foot is hugely difficult. There are areas where you'd be pushed to the limit to make 1k over the ground in an hour.

Aha, ok. I sure hope it gets sorted ok and the strip remains in use and serviceable, as it would be good to know there's a spot that's possible if flying up north on a track from Mitta through to Taralga and then up past Oberon..

Where is this strip? I live near Colo Vale, and am not aware of any strips around here other than the Mittagong strip (leased by BDAC) and a small strip opposite my place used for RFS fire support work (choppers and Thrush water bombers).

Around 15 litres/hour at 2850 in cruise sounds about right. If you got consistently less than this, then I'd be concerned about combustion temps, and if you are using less than about 18 litres/hour when doing Vy climb-outs, I'd be very concerned - you need to throw a bit extra fuel at the engine for cooling under heavy load at lower airspeeds. FWIW - any Jab. 2200 installation should have the available fuel flow rate checked at 100-hourlys, to deliver AT LEAST 25 litres/hour from either the mechanical OR the electrical boost pump, used singly. - and in max. climb attitude i.e. around AoA of 15 degrees. The Jab. Bing carby is simple to operate - there's no 'mixture' control other than starting choke. Rotax carby engines use the same carby - but Rotax engines have the operating latitude afforded by water-cooled heads. Jabs. are simpler, cheaper, and DO require more intelligent / observant operation to get reliable service. By 'intelligent' - I do NOT impugn Rotax owners - they have made a decision to pay the extra money for a more robust engine. Jab. owners should NOT expect to get a cut-price Rotax without having to pay their dues by way of careful engine management practices and attention to maintenance, any more than a farmer should expect to harness a Polo Pony to a plough and expect it to do the work of a Clydesdale. I own a Jabiru that has spent almost all of its life as a training aircraft. The log-books record a number of engine failures - and I own it because an EFATO resulted in accident damage that has required well north of 1,000 hours of rebuild time!. ( Admittedly, I've done a huge number of changes/improvements in that time). It is entirely obvious that my (L2-maintained) aircraft was subject to some of the worst maintenance I've ever seen on anything, motor-mowers included. Yes, RAA has been informed.. Not ONCE in any of the 100-hourlys signed off, is there evidence of a fuel-flow check. However, there IS evidence of repeated engine failures at low hours - but from the evidence, there is no reason to believe that any work was ever done to check that the engine installation performed to Jabiru specs. I have numerous examples of work done on my aircraft ( when I did NOT own it - it's never flown in my ownership - yet) that would be totally unacceptable for a ride-on mower. Some of those could have resulted in catastrophic failure to primary control circuits. Think rod-end fittings with the shank bent 15 degrees or more, to the nosewheel - and the effect on locking the rudder hard over.. Now - if things that could be seen on a relatively casual inspection were allowed to operate in that condition - what chance did the engine have to be operated in a responsible manner?

Post does not add value so removed - Mod

I would absolutely agree with everybody who says that you should NOT treat an AoA indicator as a 'silver bullet' - and I'd go further, to suggest that IF you install one, you should take the time / ask respected knowledgeable people, as to what the specific characteristics of the instrument you have installed are likely to be. I believe that Yenn has a valid point: a single measurement at a specific location can tell you no more than the performance at that location. FWIW: we bought two AoA kits ( in case we stuffed up the making of one), from: AOA_kit Following our enquiry re an audio take-off capability, Barker not only added that but sent us piezo horns!. Really good service!. The instrument is small - very easily mounted on the top of the panel, in eye-line, without blocking forward vision. A pair of them - one driven from each wing strut location - would take about 40mm high x 20mm wide display area. Either could drive the one piezo horn. You wouldn't need to LOOK at them to be warned that A wing was on the point of stalling: if the horn is blaring, you're getting into the danger zone. For a total cost of less than $200. Mind you - even that is HUGE, compared to the solid-state, mechanical, HUD turn coordinator that gliders have used since time immemorial: 125mm or so of wool twist, taped to the centre of the canopy dead in front of your eyes.

Not necessarily. We bought an inexpensive kit from the USA, and upon request, the kit maker not only added a take-off for the audio but a small piezo tweeter. As I understand it, the FAA requirements for stall warning is that it shall provide the pilot with a stall warning that does NOT require inside cockpit vision, so an audio horn or a stick shaker or a pre-stall buffet strip arrangement are all, I believe, satisfactory.

Mark: that cowl exit is very likely to be more effective that the 'lip' solution; it creates a low-pressure area in all flight attitudes.

I may be wrong here, but a family member learned to fly on Chipmunks. They required a lot of height and specific recovery techniques from spin entry; he was out practicing solo spin recovery in the training area outside Moorrabbin, and actually spun down between three C-47s of the RAAF traversing the training area with no radio calls to announce their presence. 'General' guidelines for manoeuvers need to be audited against the specific characteristics of the aircraft involved: the most-skilled pilot still cannot defeat the laws of physics. The classic B-52 crash at Fairchild is an exemplar here: With all respect and sadness for the results of this incident, it appears to me (who has no claim whatsoever to expertise), that the turn entered had almost no chance of success at that height and in that restricted airspace - restricted because of a 'populated area' at the margins.. I see that CASA has come out with a statement that there was no clearance for flying at that altitude in that area. As aviators, we generally have a love of 'showing off' to the general public. That is not ego, I believe, but a genuine desire to try to involve the public in the thrill of flight. However, there are so very many examples of airshow crashes that make headline news, that I ask: should we re-calibrate our perspective? Should we, as a group, factor in that our capability extends only so far and plan any demonstration flight accordingly?

LUXURY!. I had to make the smelter... and Dad would beat us with a belt full of razor-blades it we didn't clean out forge wi' tongue before the clinker set hard.. You tell that to the kids of today, and they'll never believe you...

Yep, at the moment it is the old, original scoop on an LSA55. Given the latest info from Jab., that may well change, but I'd like to put some wool tufting ahead of it and video it from a go-pro on the strut before I remove it. My new cowls are a rather different shape from the standard Jab. cowl (for an LSA55), so airflow back there may not be similar. It's important to remember that every element of a system affects everything else; the initial intake pressure you may be getting MAY not be a problem - it could be that the carby balance tube is not feeding the right info. to the Bing. This is a real 'suck it and see' ( little intake physics joke there) situation. For example: in the original certification testing of the Skyfox Gazelle, pulling hot air resulted in an instantaneous loss of nearly 2000 rpm - the carby balance tube was vented to the ambient cowl pressure. When it was changed to vent to airbox exit pressure, that revs drop went to almost nothing!. THEORETICALLY, a reasonably neutral airflow pressure at the carby throat SHOULD reduce the effect of both swirl and butterfly opening position to a minimum. Given the airflow restrictions of the filter and the airbox convolutions ( including the friction losses from lengths of SCAT tube), a slight positive pressure at the air intake SHOULD be beneficial. However - and this is something that every Jab. owner should take into consideration before just changing things - it's all a balancing act. The proof of any change lies in the recorded performance. I have gone out very much on a limb with my mods. They could turn out to be an absolute packet of poo tickets!. However, we are resigned to a serious regime of professionally-conducted testing, by someone who has undertaken the certification of a number of similar aircraft over more than 20 years, with all his test gear. If it doesn't work, we will know...

Bruce: nobody will be more interested than me! But it'll be many months yet before we can think about test flying, I still have a lot of work to do, and whether it works will only really be told by BOTH temps. achieved AND pressure-drop recording, as I've also made up a radically different airbox to try to eliminate, or at least significantly reduce, the swirl effect at the carby throat from the Jab. set-up.:

Bruce: if the 'lip' on the bottom of the cowl is too steep, in climb it will stall and the backwards flow of the outside extraction air will actually block the cowl air exit. The Jab. engine install manual shows this, and I have also been so advised by a J160 owner who has done the best work on the cooling set-up of which I am aware. Just for the giggle, this is the radical (and as yet, totally unproven!) approach I have taken with my installation, to match my entirely new cowl(s) : The barrels are fed entirely separately from the heads. This is for research purposes.

HITC: very happy that that 'lead' turned out well for you! And, very impressed with your machining - bloody great work!. Here are two piccies of the strut end fittings (for the same strut material) that we had CAMit machine up for us about two years ago for our Jab. and I reckon anybody can see that your work is right up there for quality with stuff produced on mega-buck cnc machines.. They are to the design of an aero-engineer who is somewhat notorious for not 'underdesigning' things - they are in 4140 and should last for about another millenium... but certainly not featherweights.. Since he will be the test pilot when it's back in the air, and we'll be doing the full suite including full spin testing, I guess I can't argue with what he feels comfortable to fly with..

People who blithely say 'A poor workman blames his tools" have NEVER spent half-a-day carefully machining something to the very best of one's ability - and then finding it has unacceptable tolerances due to the limitations of the machine, and a further two days or more having to make a work-around for that. I have the same problem with the only FAQ chucks on my own (fairly similar) lathe, and I reckon in the last two years I have half-filled a garbage bin with the swarf just from making adaptors for various jobs to take out the eccentricity!. Welcome back to the wonderful world of building, HITC. It's been a bitch of a summer so far down here, and I believe worse up there, for working comfortably and sometimes a bit of a break is welcome - but the 'itch' starts again, doesn't it!. The old, walk into the workshop and get the 'right, now where was I?' feeling....

No 'And?' answer... but a whole lot of small Clubs lost their investment in an ab-initio trainer-glider overnight. Blaniks had trained - to a good standard - possibly hundreds of thousands of pilots over the years. They were a decent thing to fly - albeit not sexy - and pretty cheap to run in the main. And they didn't kill people from nasty habits. About the best parallel I could think ( since Blaniks were the most populous glider produced), would be the total grounding of all C172's because one being used for a stunt plane had shed a wing. Possibly justified, but with huge consequences for GA world-wide.

Absolutely NOT having a shot at Yenn here: but isn't there a proscription about 'low-level flight' over 'public gathering' crowds? I reckon that in 99.9% of the time, a sensible,well- considered low pass down a runway with almost NO chance of danger to the public by a competent pilot is as safe (or safer) for everybody than driving your car along a public road. If it's a private fly-in situation, one could reasonably expect that all the 'spectators' are aviation-aware people who have voluntarily chosen to be in the vicinity. In terms of liability, IF something happens, the argument that 'Recreational Aviation is an inherently dangerous sport' MIGHT mitigate any damages in the case that there is an accident involving 'spectators', who could be argued to be voluntarily engaging in 'Recreational Aviation.' I would NOT like to be the one to be on the receiving end of having that tested in Court. And, let's face it, not ALL low-passes' at fly-ins go to plan. IIR, the 'SuperSTOL' demonstrator had a crash at one such fairly recently ( though having seen some of the vids. of his slow passes, I was not impressed by his judgement of safe flying). I am sure that there are many, many impromptu demos. of aircraft at fly-ins etc. that are conducted with complete observance of the best standards of airmanship - and since Yenn's passes were absolutely incident-free (just an apparent minor technical breach of the regs.), I think we all should assume that this was the case. However, 'compliance' with regulations is the first line of defence: 'I was doing everything in accordance with the requirements: this was an accident not foreseen by the regulators, therefore could not be foreseen by me'. The temptation to demonstrate one's aircraft and to provide a bit of entertainment for the crowd, is very natural. We talk about the emergence of 'the Nanny State' in disparaging terms - but even in the 1970's, EVERY ticket to a motor-car race meeting had the statement printed on it: 'Motor Racing is Dangerous, you Enter Onto the Circuit at Your Own Risk'. Small print, perhaps, but EVERY sanctioned motor-sport event carried its specific Public Risk Insurance premium cost. And this is where it gets serious: it will take only ONE high-profile 'tragedy' at a fly-in or similar, where standard regs. were ignored, to have every 'public-involvement' Rec. Av. activity subject to strangling new regs. .No 'Brekky Barbecues', no Lolly Drops at Christmas, no 'come one, come all' fly-ins without permits, huge insurance premiums, etc. Yes, it's sad and a reflection on how society has evolved. BUT: we cannot ignore it.

FWIW, for those rejuvenating old clecos. I obtained a batch of the screw-type clecos from the clearing sale of Terry Kronk ( RIP - very sad day for aviation) that had been left outside in a bucket and were somewhat rusted-up. (I prefer the screw-type to the pliers type, but that's just a personal choice.) Put them all into a molasses/water bath (around 15% non-de-sulphurised (still has the sulphur in it) molasses used for cattle-feed supplement - you get it from a Farmer's Co-op pretty much anywhere, cheap as chips) for about a fortnight. Put a mesh screen ( I used some s/s wire mesh) on some spacers at the bottom of the container to allow the iron oxide to settle out below the clecos. Then, you need to soften and remove the almost inevitable congealed duralac. I don't know of anything that will actually dissolve duralac, so I bathed them in turps for about another fortnight, then dis-assembled each one and put each shank in a battery drill and ran it using a brass (soft) wire brush on the thread. It's a bit tedious but they all came up almost brand-spankers new condition. Whether the turps idea would work on spring-type clecos, which can't be disassembled AFAIK, I have no idea.

Red Bull Glider Aerobatics team; had been doing things in Blaniks that they weren't supposed to do anyway, with an ex-air force - possibly Romanian?, I can't remember - that had unknown hours, launches ( both type and number) and unknown general use history. That caused the grounding of ALL Blaniks, world-wide, with the exception of the Australian-modded ones.

Inspired by the Wainfan Facetmobile?