Oscar

Geoff: this may well display my lack of experience of power flying, but at 3 metres, I am putting the nose down to gain airspeed...

Great that there are no injuries. An Esqual... engine unknown, but Esquals were distributed by a Bert Flood company, so possibly a Rotax. However, they also accepted Jab. engines. The strip at Wangaratta is 1640 metres, from ERSA. The Esqual publicity says t/o to 15 metres obstacle, 138 metres: less than half that of a Foxbat A22! ( I personally believe that is utter BS, but then I am a cynic). BUT: if it is correct, then there would have been well more than 1K of strip on which to put down. The landing distance in the Esqual PR blurb - from over a 15 metres obstacle - is 200 metres (also less than a Foxbat). SO: why does an engine failure at 3 metres off the deck, with maybe 5 times the potential required landing distance directly in front of it, result in a major crash landing ending in a ball of flame? The mop-up of this, with the health hazards of combusted carbon fibre, will not be cheap.

Yep, don't lift by the tip extension, they're hollow boxes, but by the tip rib (at the end of the aileron.) Preferably right under the mainspar ( about 40% aft of the leading edge.) I think I made some incorrect assumptions in my maths above ( I never trust my maths, to be honest) and overstated the load on the last 100mm 'strip' of wing, but about 50 - 60 kgs sounds about right to me.

Bruce: I can only measure the wing I have here: an LSA55. But I suspect there is not a huge difference in ratio betwen all Jabs. And my maths is not exactly world-class, so forgive me my errors.. I don't have the wing loading figures for the LSA 55, but the J120 is fairly similar. I believe the J120 wings are made from the last of the LSA55'variants' - perhaps the SP470? The wing loading on the J120, is quoted at 63.5 or so KGS/m/2 at Gross weight of 500 kgs. . Since the wing chord is almost exactly 1000, then every 100 mm of span is carrying 6.35 kgs. BUT: when lifting a wing in the hangar, you subtract two x people at 85kgs: Gross weight of about 330 Kgs. = about 42 kgs/m/2, or 4.2 kgs/100mm The lift strut attachment point on my wings, is at 1550 out from the root attachments - or almost half the distance to the tip rib at 3200. Now, when the lift strut is taken into consideration, the 1G loading at empty weight for the last 100mm of the wing span, would be about 4.2 kgs x say 16: about 67 kgs. ONLY the spar and wing skin outboard of the lift strut attachment point is in shear: inboard of that, it is in compression. Now, for a hangar lift against the 'outboard' main wheel, I reckon Nev's estimate of about 70% of the aircraft weight is a good guide: so let's call the force required on the lifting wing tip rib is: 67 /.7: about 95 kgs. I am damn sure I can't lift 95 kgs using just my arms, but I think I can get a wheel up by getting my shoulder into the job.. Try yours: can you lift the inner wheel off the ground by pushing up at the tip rib? If you can then I reckon my estimate of around 100 kgs force is in the ballpark. Now, Jabs are certified/certificated to at least +4G - so that last 100 mm of each wing is lifting about 25kgs. ( they are supposed to have a 1.5 x safety factor : 37kgs, and a claimed +7G structural limit:: about 42 kgs) Just at the .normal flight load' limit of 4G at MTOW, that means a force capability of 37 x 16: 555 kgs - distributed evenly from the outside wheel to the inside tip rib - NOT 555 kgs of fuselage!!!. It sounds CRAZY, but I think you'd need a real engineer to do the maths before you just laugh it off. If you want the best informed opinion, the man to ask is Alan Kerr - he did the structural justification on all the early Jabs.

The Jab wing is untapered and of constant section. It is also supported by a lift strut. The Jab is certificated at around +4G. The mainspar tapers in thickness outboard - but not in depth. If you can't lift a Jab by the outer wing skin and have the wing not even noticeably deflect, then run away from it as soon as you have put it down - it's seriously damaged.

If you are lifting on the tip moulding rather than the wing skin, where the load is carried by the spar) I can see the inadvisability. However - the main wing structure would easily carry the weight being reacted at the opposing main wheel.

jj_ a HUGE apology!. I am starting to build a brand new airbox, and looked at the ( absolutely AWFUL) cobbled-up abortion on my aircraft, that was obviously done when changing from the 1600 engine to the 2200. Id I posted a picture ( that facility seems to have disappeared from the site), I probably wouldn't, to save people from throwing up their Weeties all over their keyboard. I had removed it and thrown it away in disgust, to the back of the workshop - but I dragged it out to look at what I might - possibly - use in the new set-up. You are absolutely correct: the majority of the hot-air passes through the airfilter, though there is a small by-pass in the hot air intake (about 1 inch square in area that exits after the filter.). That has the carby balance tube installed in it. That arrangement is just not kosher: the hot-air intake is supposed to also provide an alternate inlet in the case of filter blockage. Further, it means that a % of hot and unfiltered air was ALWAYS being fed into the engine: power reduction issues and excessive wear issues... If hot air is selected, it certainly DOES bypass the main inlet SCAT hose connecting the cold air intake on the side of the cowl to the airbox - it's a 100% bypass. You get full HOT air - but when cold air is selected, you don't get 100% cold air. In ambients of maybe 20C or lower, that's probably not an issue - but it could be an issue if trying to claw out of a short-ish hot-and high airfield at MTOW.

Two real-life Australian aviator heroes: https://www.amazon.com/Sidney-Cotton-Last-Plane-Berlin/dp/0733615163 Into the Midst of Things. The Autobiography of Sir Richard Kingsland | Kristen Alexander | Australian author

The standard Jab. U/C has been pretty robust over the size of the fleet. There are two potential problems with 'glass legs: a QC issue in the resin mix resulting in lower strength / stiffness, and if the aircraft has been tied down on a bitumen strip in the extreme Australian summer, the lower area glass reaching softening temperature (around 90C) from reflected heat off the bitumen and being subject to high(ish) loadings while in that condition.

EGGsealant!.

I would like to see a coterie of skilled drone pilots with proper sensibility out there supporting the things that drones can do well. Look, there is the Jet-ski mob - mostly dangerous cockroaches on the aquatic fraternity - but Jet--skis are also a powerful and effective weapon in the surf life-saving armoury. A significant proportion of trail-bike riders are bloody oiks, tearing up the country-side and annoying the manure out of a peaceful weekend - but responsible trail-bike riders can cover a huge amount of ground when searching for lost people. Intelligent hunters surgically excise feral animals and give native species a chance of existing, while the Billy-Bobs of the world shoot holes in road signs. Leaf-blowers, originally designed for the purpose of raising the annoyance-level of neighbours to homicidal level, are a fast and effective way to create a safe burn-line for bushfire hazard reduction and back-burning efforts. There is almost nothing that some idiot cannot use to do something idiotic. Up to and including a B-52.

Very true, ra, and once there are aerial ops. in place, the drones would have to be grounded - absolutely. But I've been in the RFS for over 20 years, and aerial support isn't anything like ubiquitous.. and when you're out in some really remote area ( like Bindook, where I've been on four occasions, once literally fighting the fire up to the boundary gate) with only one track in, through miles and miles of bush, you'd like to be able to see what's happening around you.

The 'stupidity' in this case, is not the actual action undertaken - because from everything I have read so far, it was actually undertaken with a decent level of care for the risk of those below. IF CASA prosecutes this bloke, I would hope he gets a $10 fine for public nuisance value and CASA gets lumbered with all the court case fees. The outcome was totally benign ( bar possible flatulence) and I personally consider that it was a hoot, absolutely in keeping with what we like to think is an Australian relaxed attitude.. A Bunnings sauso, delivered to the pool party, without needing to drive ( possibly well-lubricated) down the public roads? Brilliant! BUT: the 'stupidity' was the expressed reason: to make a YouTube video. Nobody with the slightest appreciation of the infinite capacity of human beings to do stupid things would fail to see that once you start down that track, there will be someone with lower intelligence trying to do it 'better' - from a YouTube video perspective. How long will it be before someone decides to see what a visual hoot it could be to video-strafe the spectators at a football match, or go for the close-ups at a 'nude' beach', or panic a celebrity wedding? I happen to believe that the responsible and sensible use of this class of drones has the potential to be a major improvement in information-gathering for a whole and vast area of social needs. BUT - I stress: 'responsible and sensible'. If this guy had been, for instance, using his drone to help search for a lost person, identifying the location of a criminal, reporting the progress of a fire or a flood event, beach patrol, - hell, even traffic reporting: I'd contribute to his Court costs. But just to make a YouTube video and thereby encourage others to mis-use their drones? NO, I class that as stupid.

My brother flew his Auster J5G to De Hav's most days to work, from around 1988 -1990 plus. Tied it down usually on the helicopter test pad. Used a taxiway coming from the river mostly for landing..

It was a bloody stupid thing to do - though in mitigation, apparently he had plotted a route with minimum risk to the general populace. I don't like the thought that numbskulls see getting a video on YouTube as a decent reason to be idiots, but we see way more dangerous stuff posted every day. Had he organised someone at the pick-up point as a 'Safety Officer', and arranged it with Bunnings before hand, I think it would be on the very low-end of 'offences'. I've had a few 'run and dodge' moments in a Bunnings carpark when Fred Fackwit has been driving in with his phone glued to his brain..

Fortunately, the actual sausage probably wasn't MADE for Bunnings, otherwise the silly little bugger would have something gastrically nasty on top of CASA's drastically nasty threats to deal with..

The idea that CASA etc. REPRESENT Aviation, comes from somewhere else than reality. An accurate analogy would be that Parking Inspectors REPRESENT the car owners who get fined.

Seb: you are entirely correct in that the red poly sheet packers go between the leg and the fuselage. There is simply not enough room for a 2.5mm (from memory) thick packer between the 'second series' Type 1 legs and the sides of the clamp ( or 'saddle'). IF your old legs were the early - thinner - Type 1, you may not see any abrasion from the saddle edges. I don't have any early Type 1 legs to comment upon; but the 'Heavy Duty' Type 1's that were installed on my aircraft have notches in the edges from abrasion with the unrelieved edges of the clamp, after around 350 hours maximum flight time according to our log book. Your clamps may have been set-up for the later, thicker legs: I suggest you compare the new leg dimensions at the clamp point with the ones you are replacing. I THINK - but am not sure - that the '470' designation relates to the MTOW - my aircraft has a 430 MTOW - so it may well have had the thicker legs installed as standard, with the appropriate clamp.. .

Seb, be careful when you fit the new legs. The early Jabs. - mine is one - had the 'first' legs: basically rectangular in cross-section, and straight from the outer end of the outer 'saddle' down to the axle bit; the 470 usually had the same legs, I think. Mine was for almost all of its life, a training aircraft, and following an accident, had the legs - all three - replaced with what Jabiru describes as 'heavy-duty': basically the same shape bit with several extra layers of cloth in them, to increase the cross-section. All good BUT: they are an extremely tight fit in the outer saddle, to the point where the vertical edges of the saddle chopped into the legs. The edges of the saddle had not been chamfered to relieve this ( and they were installed by an L2, just one of many seriously bad jobs done on this poor little bugger). The bending point at the saddle is a high-stress area, for two reasons: the first is that it introduces a discontinuity in the line of force being carried by the composite matrix ( note that the later Jabs. have a curved frontal projection, so that where they pass through the 'saddle' they are far closer to straight. The second is, that when they 'rock' under load in the saddle, the square (or flat) shape of the saddle introduces a leverage aspect. This additional leverage as the material flexes adds a very considerable amount of stress to the leg material: exactly that problem beset Citabrias and continued with P92 Echos, to make main leg failure quite common. The cure for that is simple: put a small amount of radius on the bottom face of the saddle and chamfer the edges. Jabiru did a fair job of combating that leverage aspect by adding a polyurethane strip (around 90 durometer, I think from memory) to the top and bottom sides of the 'saddle'; hopefully your new legs will come with new strips for installation. You can buy the sheet from suspension bush manufacturers but honestly, it's cheaper to just get them from Jabiru. I had to replace ONE front-leg donut - because (again) the L2 installation of a new heavy-duty front leg had been done badly - and in another aspect, very, very dangerously, but that is another story.. If the new legs Jab. have supplied are the 'heavy duty' specification, you will need new bolts for the saddles and for the inner ends - about 1 additional dash length. On my aircraft, the replacement was done with (obviously) whatever bolts the L2 had around, and there were up to six washers under one. AND: make sure that you use new, proper-grade, nylocs for final installation: I have to say (with regret) that I am aware of Jabiru sending out good bolts with lousy-spec. nylocs: get yours from Skyshop, or SunCoast Airparts, or your local engineering supply shop - but NOT Bunnings et. al. It's worth a look at the 'drop test' video on the Jab. web-site (well, on the older one, anyway!) to see just how far the main legs distort on hard landing, to appreciate just how much movement there is at the 'saddle'. The recommended toe-in for Jab main wheels is about 3/4 degree, for an unladen aircraft. You achieve that by adding washers as necessary to the front or rear of the axle and THEN install the axle with 'flock' - LC3600 with glue-powder additive - to take the axle load out into the leg. CG Composites: HOME : CGComposites are epoxy resin suppliers and offer composite material information can supply LC3600 in small quantities and glue powder ( e.g WEST 403 or equivalent), and are absolutely GREAT to deal with - 100% recommended. The Jabiru recommended method to set toe-in, is, for my money, lousy - because it uses the side of the tyre as a reference. The damn tyres are NOTHING like accurate ( lift a leg and rotate the tyre with a dial-gauge against the sidewall to see how bad it is); at the least, you need to build a rig that references off the wheel rims. If you only use grass, that doesn't matter, but if you use bitumen, it will make the aircraft twitchy on ground roll.

O K, things get complicated. My aircraft was the first to be certificated (and get VH-reg) that Jabiru produced. That meant that it had to meet all the BCAR S standard for the airframe and engine installation - remember, installation is NOT an engine certification issue: the engine has to meet the requisite standard ( for the Jab. engines, and the Rotax 912A model, JAR 22H.) That is ONE set of performance standards, from which the TBO (amongst other things) gets set - but it also produces the 'limits' for operation: max revs, max temp,max running time at various power setting etc.. Then, the installation has to produce, for the POH, a set of performance parameters that determine the actual aircraft performance limits. Mostly, those relate to keeping the engine within its certificated (or certified) limits for that installation. (However, by way of further information, the allowable climb profile for the Seabird Seeker is actually limited by the NOISE limits: pusher aircraft tend to produce more noise as a result of the prop. passing the wings and producing a noise pulse, than from the actual engine exhaust). What this means, in practical terms, is that the POH climb speeds and revs limits for, say, a J160 with a 2200A engine, is NOT automatically transferable to another aircraft with a different installation. Each installation has to be tested and the aircraft performance profile adjusted as a result of testing. Now, WRT to the airbox conundrum that has been exposed here: as a certificated aircraft, my Jab. had to meet BCAR S standards. In respect to the engine air delivery, that required that the hot air setting bypassed the filter and airbox intake SCAT tube, so that if either caused a blockage, by pulling the hot air on there is a direct input of air to the carburettor. I assume that the rationale for this is that, hot (and therefore less dense, resulting in lower combustible fuel/air mixture) is delivered to the carby: some air is better than none..) The airbox on my aircraft has two 'rubber' flaps. One, is attached to the hot-air ./cold air switch-over mechanism. It appears to be a bit of around 6mm thick conveyor belt-type material. In the 'normal' (or 'cold air) position, it delivers air through the filter that exits into the airbox outer housing, from where the delivery SCAT tube to the carby is taken off. When 'hot air' is pulled, the air coming from around the muffler is delivered directly into the outer area of the airbox, entirely bypassing both the intake SCAT tube and the filter and thence to the carby. In simplistic terms: if your intake scoop ( or NACA duct, depending on the model) gets completely blocked by e.g swallowing a sparrow, by pulling the 'hot air' control, you will still get air coming into the airbox and therefore to the carby. The second flap is a small - about 75mm x 25mm piece- of what looks suspiciously like a bit of car inner-tube on my airbox- that sits on the top of the airbox outside the filter: so a backfire pressure passes around the filter and is relieved by that top flap. Now, I have no idea as to whether that was tested to ensure that the air filter was not severely damaged by a backfire - but it does ( I assume) meet the BCAR S requirements for an alternate air delivery in the case the the filter is damaged and blocked. So: in summary: the airbox (which appears to have been thrown together by a blind idiot working under the lash, it is a truly horrible bit of work) on my aircraft., evidently met the standard required for 'certificated' acceptance. If later Jabiru airboxes operate differently, I can only assume that the ASTM standard does not require the 'redundancy' of the FAR / BCAR S standard. I will not be putting that airbox back onto my aircraft; I will build something more closely resembling what has been used on Lycomings etc. for years, very successfully. That will incorporate backfire relief 'downstream' of the filter.

Thanks for that heads-up - I wonder why AVIC isn't at least recognising the Brumby? It's a competent and well-designed aircraft (AFAIK), with good flying characteristics and for my money, a damn sight stronger than quite a few of the flashy Euro's, and I'd have thought, a good prospect for Training, especially. Has pretty much all the essentials I'd look for in something for more demanding conditions ( such as Australia!). While I am a known and shameless Jabiru fan, I think the High-Wing Brumby in particular had a lot of the same 'design ethic': a reliable work-horse, safe, 'get you there and bring you back' without drama. That is meant as a total compliment: there's a reason why anywhere outback of the major urbanised areas, you see a whole lot of Landcruisers and Prados but damn few Porsche Cayennes. Nothing stuffs up a planned major holiday worse than being stranded at Didjabringabeeralong with a broken main gear leg that failed because it hit a recent rut in the dirt runway from last week's flood.. Especially if the replacement has to be flown from Czechoslovakia... I have no personal exposure of Brumbys, but from what I've read, they handled 'our' conditions pretty damn well.

Hmm - then it's been changed, it did on my (certificated) ST1... via a bloody awfully dodgy airbox, maybe that's why it is so awful!.

jj: the flap on the top of the airbox is there to prevent backfires from crushing the air filter and thus stuffing up further intake air to the engine- not to regulate intake air pressure. The whole hot-air-intake design that bypasses the air fillter, is done that way so that there is a back-up air delivery system in case the air filter ( or the SCAT intake tube) collapses.

Bruce - it just isn't that easy!. The Jab. ram ducts CAN be made to work effectively; there is a guy at Camden airport who has worked for over 12 months - meticulously - on his 160 cooling - including tufting his ducts and recording that with a borescope, in flight, over a scheduled set of flight tests. He's gotten them to work - in conjunction with carefully modifying the extraction lip on the bottom of the cowl - very well indeed. To give you an idea of how intricate this work is: he found that the middle-deflectors in each ram duct had to be varied between the sides by 2mm or so to balance the temps side-to-side in climb. That is because the 1-3 heads are closer to the intakes than the 2-4 heads and the 'ramp' behind the intakes is at a different position relative to the intakes, plus the differential of the prop blast from the upcoming side vs. the downgoing side. (When Alan Kerr was designing the engine installation for Jab. 2200s in Drones to meet Boeing's requirements for their proposal for a modified Israeli drone for the RAAF, he found that in ground running with a slight crosswind, the RH side of the engine was sucking the hot air from the LH side back up the rh side ram duct. You know what damage extended ground running can do - and Jabiru's POH recognised this..) The guy at Camden also found that his extraction lip on the bottom of the cowl was perhaps 25mm longer than ideal - because it was stalling at high climb angles and choking the extraction airflow.. The flow reversal inside the traditional plenum, is quite well-known. In fact, the usual gap of the cowl around the prop. shaft (mandated because the clearance between the cowl and the engine MUST be at least 1/2" to allow for engine movement) actually creates a 'pumping' area of low pressure. The answer to cooling is absolutely NOT just stuffing air in - it has to be able to move past the hot areas with sufficient energy to extract heat.. That means getting the low-pressure area working well - the p-delta. As a crude analogy: you as a farmer would know what happens when you get a serious downpour. You dig ditches to direct that away from your sheds etc. BUT - if the ditches block up, or aren't sufficient, the bloody water floods out everywhere.. Now, assume that you WANTED that water to flow around specific areas... Huge amounts of water flow are coming in, but it's not resulting in huge amounts of water flow in the areas you'd like it to be - its just going everywhere. (and usually, flooding the bloody hayshed and creating a self-combusting mass of your stored hay.. been there, done that). You'd remember, I am sure, that in the 'good old days' of us trying to improve the performance of our cars: extractors were the FIRST thing we'd add. We wouldn't even think about porting and polishing, extended intakes, larger carbies, even hot cams ahead of extractors and a larger and less back-pressure exhaust. Well, basically with cooling of an air-cooled engine, it's the same!. Air In and air OUT is the prime requisite. And the air OUT needs to flow around the heat-intensive areas.

OK, Dafydd Llewellyn worked at Victa with Henry M. I don't think he worked on the four-seater, but may be able to give you some background on the l/e 'cuff' aerodynamics.