saccani

Provided that you design the aircraft in light of the (presently unknown) properties of the materials you are using you could use the methods that you propose. The reason that that might be impractical is that this might require an increase in weight, may be more difficult to fabricate in practice and will have increased design and technical risks - no one else is doing it, so you get to be the one that finds out what goes wrong with the process. This is often painful. There does not appear to be useful engineering data on your proposed material, so you would have to test it yourself in order to do the engineering analysis. The biggest problem is the change in properties you would get from heating the typical aerospace aluminium alloy, some of which respond very badly indeed, such as 2024 series. Joints will of course require redesign to work with the properties of the completed bond, whatever that may be. Using 6061-T6 as an example, the temperature required for the “Ultra Bond” material would, at the least, reduce ultimate strength by close to a third. You now have an unknown alloy forming your joint with unknown properties. Naturally, you will need to test it to find out what those properties are. Fatigue properties would be very important and would also take most resources. And you need to find out if you can manage the quality of these bonds. (How critical is the process control to the end result?) 6061-T6 can be welded using 4043, giving properties similar to 6061-T4. With suitable heat treatment (of the entire welded structure), you should be able to get properties close to T6 again. But at least there is data to support you on this endeavour. Designing for T4 should achieve an acceptable result. That might be practical for you to experiment with. 2024 series would be most impractical for the methods you propose. For what it’s worth, some companies have found it practical to use electron beam welding to attach skins in stressed skin structures. There has been a fair bit of research on the practicalities of welding aircraft structures with common aerospace alloys. You could probably find some helpful papers in the NATO AGARD archive and from the US DTIC. In terms of light aircraft, I suspect that the bolted web joint ends up being lightest, with few process control problems and few ‘unknowns’. Fusion processes would seem very dependant on process control and would thus require an amount of development for each design that may be difficult to justify even for series production, let alone home builders. With regard to welded tubular 4130 structure versus aluminium alloy, the fatigue properties of the welded al. alloy joint could be expected to be ‘not real flash’, thus requiring much thicker material. Forged or cast joiners with chemical bonds (eg, epoxy) would seem practical, but the burden of making the joiners would be high. Using fabricated 4130 joiners with epoxy bonds to Al. alloy would appear practical - but it would be easier to make it all out of 4130, I fear.

The calendar life specified in part 5 of the Rotax AMM gives 10, 12 or 15 years in the 912 series dependant on ESN, certification and model, with a 6 month extension permitted in all cases. The mandatory part of the AMM (in the certified environment) is the Airworthiness limitations section. If you read this, it states that there are no limitations, but it does give a note about the lifed components, TBO, calendar life etc... required in part 5. A note is not a limitation. Therefore running on condition is not prohibited by the AMM in the certified environment. LSA rules are different., With regard to "you can't zero time a Rotax", that is completely untrue. However, there are few facilities authorised by Rotax to do overhauls and Rotax will not supply some of the mandatory components to non-authorised facilities. A zero time 912 always requires a new crankshaft, exhaust valves, rings, seals and gaskets. Cylinders are not reworked (they are nikasil) but may usually be reused just as they are. Heads are reused. Dependant on serial number, a new crankcase may be mandatory to get a 2,000 hour TBO, but if serviceable, it may also be reused even if will give a shorter TBO. Intake valves are changed on condition, as are camshafts. Pistons are on condition. Gearboxes are on condition and usually require no replacement items other than seals - unless run on 100LL or 100/130, in which case the slipper clutch disks may need to be replaced due to lead fouling. The ignition system is on condition. The carburetors have to be overhauled. I haven't caught up with the requirements for fuel injection. An overhaul is expensive, many elect to buy a new engine instead, a certified 912A costs $33,000 new, a zero time overhaul can be expected to be around $17,000, whilst you should be able to get at least $3,500 for the old core when buying new. The mechanically identical uncertified 912UL only costs $22,500 new. There are some good reasons for mandatory crankshaft replacement on hours run, with the design of the 91x series crankshafts. I can think of no technical argument to support a blanket calendar life for them... With regard to "new is best", in my experience this is not the case. 'Newish" to middle aged is best. With regard to cracks etc... this is exactly dealt with by "on condition" inspection. Many engines will not reach their TBO, but we hope to find them 'on condition' before they have a chance to fail. On condition inspections are our best defence, not arbitary TBO or calender life. But there are good reasons for calendar life - however, they certainly don't require a bulk strip and mandatory crankshaft replacement to ensure continued airworthiness. The possibility of a minor oil leak that will not cause a hazard and will be picked up and rectified on a recurrent inspection is not a reason to, in effect, throw away an engine. No matter how much this might suit a manufacturer. By and large, a new engine is much more likely to fail than one that has reached or exceeded TBO with proper maintenance and operation. In the certified, commercial world, there are ways to deal with the calendar life issue for piston engines - in private ops of certified aircraft these are not available, but 'on condition' operation is available, and it does seem a darned sight more practical. Before the latest amendment of AD/ENG/4, there was an explicit authorisation to exceed TBO in private ops if using schedule 5 - now there is not.However, this can be problematical on the regulatory front for many Rotax operators who have uncertified aircraft with uncertified engines. The crying shame is, the 912 series do have a demonstrated potential to greatly exceed TBO if looked after, but due to the method of crankshaft construction, if incidents such as prop strikes, or even engine backfires have been concealed from the logbook, they can also fail catastrophically even before half TBO. This is probably one of the major factors in BRP having such a conservative approach. Anyone who tries to save money by buying the uncertified versions without the slipper clutch has got rocks in their head if you ask me. regards, Paul

Could you perhaps narrow the scope of what it is that contradicts your info? It would make it easier for me to tell you the source. regards, Paul

For what it is worth; The issue is LSA aircraft with ASTM engines. The airworthiness requirements are that the manufacturers maintenance instructions are followed - there is *almost* no scope for "on condition" extensions in this regime if not permitted by the relevant maintenance manuals or explicit manufacturer authorisation. I would argue that with the mechanically identical certified forms of the engine (912A and 912F), there is a reasonable legal basis to run them on condition. But the certification basis for the ASTM version of the engine (912UL) does not allow 'on condition' operation contra to manufacturer instructions. For what it is worth, Rotax had a competition in 2016 to find their oldest certified engine still in service, it was won by a certified 912A, ESN36351, which had successfully run over 5,500 hours and 25 years without overhaul, on condition, (for this ESN, the Rotax TBO is 600 hours/10 years) - this engine remained in service at that time and has presumably gained hours and time since. Rotax have discretely buried that information now.... The price of the certified versions of the 912 runs between 50% and 100% more (dependant on certification basis), whilst EASA certified versions of the later 914 and 915 are in the order of less than 10% more expensive than ASTM versions. For the Rotax 91x series ASTM engines in an LSA, you are permitted by the AMM a 5% over run on TBO and a 6 month extension on calendar life, which is better than nothing, I guess. regards, Paul

Well, you're working in that field, I'll take your word for it. I would have thought it would be fairly straight forward (but not trivial), other than in the redundancy of the high pressure side. All the variable valve timing and so on, you would fix in place, I can't see how something like SDS would have an issue with control. As an aside, I see that Viking are selling their old redrive, for the L15A7 for US$3,000. I'm *really* looking forward to hearing about your project. ;) Regards, Paul

With regard to serial 1, they are available from wreckers, and of course, it is easier to get low time L15B than the L15A7. With serial 2, I'm not sure what you have in mind with regard to the aftermarket. The 130 is the only engine being sold by Eggenfelner, the 110 was discontinued. Of course, "addito salis grano" with any recipe containing Eggenfelner as an ingredient is well advised. But it seems a legitimate enough power/torque claim, and within the stated design parameters of the reduction drive. However, as in the past, any reliability data gathered from the in service engines is now no longer applicable. Regards, Paul

I can't confirm that. It's worth noting that this wasn't the case with the earlier Viking 100, which had less peak power than the standard Honda engine.

You're probably thinking of the earlier L15A series engines. This one is the L15B with direct injection from the later part of the 3rd generation fit/jazz, which makes 130 HP out of the box. The torque/power curves on the Viking site match that engine. That is the current engine used in the North American version.

As I recall it, he already implied that with the Viking 110 Vs Rotax 912s weight comparison.

912 iS is for the fuel injected version of the 912S. The Viking 130 is not the earlier, abandoned L15A7 engine core with turbocharging of the same name. This one is using the direct injection version of the L15, the L15B i-VTEC. AFAIK, it's the Earth Dream version. That means that it is Atkinson cycle, not Otto Cycle. Whether or not it operates on Atkinson cycle after Jan's ministrations, I don't know. But I would presume that he would set it up with fixed valve timing for otto cycle. As always, the Rotax values are for the end of the 2,000 hour TBO and can be relied on, the propeller hub torque at maximum continuous power for the 912 iS is actually 235 ft/lb @ 2,060 Prop. RPM, they understate it. The Viking torque value is at 1,980 propeller RPM, 110 HP, 130 HP comes @ 2,630 RPM prop, 6,100 engine. The 912 iS had a free upgrade (SB-912 I-003iS R1) to 912 iS Sport, which has a max. continuous power of 136 HP @5,500 RPM engine/2,264 RPM prop, , despite still being sold as a 100 HP engine. For practical purposes, the iS is obsolete. So the current version makes 238 ft/lb at the propeller flange. I hope this helps.

<smile> That's some enthusiasm. I didn't find them that hard. You should see the wing attach fittings of an F1 mirage to see welding as an art form. ;) Cheers, Paul

G'day Phil, The bracket (7-F-17-1SP is attached to the fuselage side and also to the U shaped bottom channel 7-F-10-1 with a pair of doublers, 7-F-10-2, just as you say. But the undercarriage leaf itself is hugely stronger than the doubler, and is attached by some bolts that are quite stout. It unquestionably contributes to the attachment of 7-F-17-1SP to the fuselage under positive loading - whether intended to or not. It may very well be that this contribution is completely unrequired and not considered in the stress analysis by Heintz. However, the wise move is to talk to Caleb or someone else at Zenith/Zenair and ask. Undoubtedly they already know if it is an issue, and if needed, would advise on any other modifications if needed. They did offer a tail dragger plans option with the earlier version, so they would know all the answers. All it takes is an email to get the good gen. Cheers, Paul

G'day Phil, I was very much under the impression that the bolts holding the undercarriage leaf on also helped to hold the wing strut attach fittings on to the aircraft with positive g. Might be worth checking with Caleb as to the need for a more robust carry through structure if you follow that scheme. Cheers, Paul

I just work on them. They don't have long lives. I sure wouldn't contemplate a TS for an Aero conversion. ;) Cheers, Paul

Hmmm... well they aren't that flash when made by Italians. I wouldn't be surprised if the Chinese made ones were *better*! Cheers, Paul.

That's what I said - "Unlike the ramps, these [centring springs] will provide additional resistance to turns when taxying.".. :) The ramp angles are there by design, not accident, so it is cavalier to remove them without knowing why they are there, don't you think? The least one should do is talk it over with Caleb. They don't mind you reducing the angle some... The nose bungee does wear out - but it doesn't do so without warning, and it usually fails gracefully. I don't have the ring on my nose leg, as I want the full travel and that restricts it unnecessarily and can result in a bent leg (and prop). I've put a 45 degree bend in my nose wheel axle as a result of a vicious gust - the bungee part and the rest of the structure seemed quite content. As it was a graceful enough failure, I replaced it with another as per the plans, though I have made a stronger one as a spare in case it starts forming a habit. For a very light aircraft, the coil spring set up does look a bit heavier than a lacky band... weight control is pretty high on my list of priorities. Are you making your own floats? I've seriously thought about putting water skis on, there is a good body of test data on "universal landing gear", with wheel penetrating skis to operate on water, snow, etc All you need is a little beach to taxi to and from. I know it sounds quite mad, but there was considerable real world testing on it in the fifties, that was supplanted by further development of helicopters. Cheers, Paul

I think there is a bit more to consider than that. If you look at that link, you will see this "The Preloading of the spring is handled internal to the spring, using an adjustable rod, providing no force to the airframe while in flight. The ramp effect of the original plastic material has been milled away and the steering arms now ride on a flat surface.". The ramp effect is there for a reason. It is a bit of a pain, but it is also necessary. With the all flying tail, you need a centring force on the rudder, and that's what the ramps are for. Milling them flat is altogether too casual an approach. If that is done, you will need to provide some centring springs for the rudder pedals. Unlike the ramps, these will provide additional resistance to turns when taxying. It is one of the disagreeable aspects of the 701's handling in flight, that there is such a self centring tendency, but not having it can be more disagreeable. Other than that, it looks like one of the better thought out ideas from Jan, and it is even reasonably priced. Regards, Paul

I know this is an old post, but just to clarify; The Viking uses the Honda L15A7 engine. That is not dual plug version, the L15A2, A4 and the (rare) A5 engines are dual plug. That's I-DSI in Honda's parlance, for "Intelligent Dual and Sequential Ignition". This isn't used on the VTEC engines, like the one in the Viking. Though the VTEC is disabled in the Viking conversion. I did bring this up with Jan, that it would be better to go with the dual ignition version, even at a small cost in power, but he pooh poohed the idea and he may have been right to do so. I also discussed this with Jeron Smith, of Raven Redrives, during the development of his L15 based engine. He gave a reasonable explanation, that he was excited when I-DSI came out, but that I-DSI swapped two valves for a spark plug, and that though this improved economy and potential reliability was increased, the power to weight trade off wasn't worth it. I can agree, in that an unmodified I-DSI puts out about 86 HP, versus 117 HP for an A7 with VTEC (and consequently, a four valve head). If one was prepared to cut up a few heads to find out where to put it, I think a second plug could be put into the VTEC head, but it would have to be a small plug, like the second one used in 4 valve Alfa Romeo Twin Spark engines. I'd certainly be more content with an independent 2nd ignition available. Regards, Paul

The reality is, if you can't afford a used Rotax 912, you definitely can't afford a "new" Viking. You can get a 912ULS3 with 500 HTR for $6,500 in Australia. With the propeller and spinner thrown in. You would have a much greater chance of running that on condition for 2,000 hours safely without overhaul than you would from the Viking. Sure, the cost of overhaul is greater when it comes - but even if you did that after only 500 hours, it wouldn't be that much greater than a Viking. The idea of having a cheap replacement engine after 2,000 hours is flawed, in that private operations take a long time to chew up 2,000 hours, and the engine is already superceded in production. You can't reasonably expect to get a cheap, low time engine in good condition in ten years time. And you have to remember, you are comparing a used automotive engine conversion with a *new* Rotax 912ULS. The correct comparison is with a used Rotax 912ULS. The claimed 117 HP output of the Viking is an exact match to the published flywheel power of the Honda engine, the 100 HP rating of the Rotax is for the propeller flange *at the end of TBO*, so this may not be as big a factor as some think. And if you have need of any of the reduction drive components in ten years time, the non-availability of spares for Eggenfellner Aircraft reduction drives should factor into your assessment. The Viking isn't that cheap, if you ask me. And it is heavier, particularly when its installation requirements are looked at. Regards, Paul

There are problems with the Knowledge Deficiency Report. RAA are aware of this and dealing with it as an IT issue. Your pass should be correctly recorded, you can log in to confirm this, it should show up as green and passed. This is very much intended as a beta test period, with Feb 2015 as the target date for it to be released properly. Regards, Paul

Indeed. In my view, the CASA have been remiss in this regard. I can't see any legitimate reason to state a high failure rate - and then present no data on the matter. If they have the data, it needs to be shared. If they don't have the data - is their action legitimate? Thus far, they aren't sharing information with the RAAOs and the manufacturer, let alone the aviation community as a whole. The baffles me. I can't see a safety case for it, I can only see a safety case against withholding the information. Cheers, Paul

Indeed, but the problem is, the same name may not mean the same thing. Some refer to a Jesus bolt as the bolt securing a safety strap or cable for the hang point, for instance. Cheers, Paul

Extract from Pegasus XL 447 Operators Handbook, 1992, Pegasus Aviation, Wiltshire, UK. Paragraph 4.3.f -"Hang-point undamaged, heart-bolt and back-up strap secure." Kind of looks like a UK manufacturer (P&M, to be precise) using the term "heart bolt" to refer to a hang bolt, doesn't it? ;) I can provide more UK examples if you wish. Thanks for that. Begging your pardon, but the original post was about using the term "heart bolt" and this being an obscure term and it then being claimed as an Australian-centric term. This term is not peculiar to Australia and is *also* used (meaning also, rather than universally used, as you seem to have taken it) in the UK, Italy and Germany (I'll add Canada and the USA to the list, for that matter), and not peculiar to Australia. As I said, I think the term "hang bolt" is better. But the point of the exercise in the training manual is to use the manufacturer maintenance manual. You need to be able to use whatever nomenclature that they have chosen. They may call the bolt "Fred", if they wish, and when you look at the maintenance schedule and see Fred, you may then need to figure out what Fred is, whether from the maintenance manual, parts manual or asking the manufacturer. I don't think the terms "Jesus nut", "Jesus bolt", "heart bolt", "Jesus strap", etc... are very helpful ones for maintenance - though I suppose they play a useful part in flight instruction. :) Far better to use a more descriptive terms, like "hang bolt", "safety strap/cable" and so on, and discourage the use of the more colourful terms. I'm also aware that UK manufacturers like P&M more usually refer to hang bolts rather than heart bolts, but it has to said that what I actually said was 100% accurate for the UK, it is *also* used there. Just please don't take the word "also" to mean "universally", a word I would have used if it was what I meant to say. The worst thing about using nomenclature such as "heart bolt" is that different manufacturers have used the same term to describe bolts with very different functionality in wings of generally similar construction. This is the more important issue than the term being obscure. Having said all that, the L1 maintainer has to be able to figure out the nomenclature used by their manufacturer in order to safely maintain their aircraft, and this is the worthy goal of the study guide, and to that end, I think that the manual extract referring to the heart bolt was a very good example to use. I would wager most RAA members to have never heard of such a thing, which makes the exercise all the better, in my view. Cheers, Paul

I think that doing something similar for the Ops Manual is a pretty good idea - it need not be compulsory to be useful. Did you get a valid Knowledge Deficiency Report out of it? Cheers, Paul

In Italian production, it is also called a heartbolt.... It is also called that in the UK and Germany. Though hang bolt is probably a better name - the rest of the world also uses heartbolt. Cheers, Paul