LoonyBob

A "special certificate of airworthiness" is not recognised by ICAO; if you cart a VH aircraft to another country and want to fly it, it must have a normal Certificate of Airworthiness and a current Maintenance Release. If the other country has a mechanism for aircraft not certified against an ICAO recognised design standard (e.g. the UK, USA), then they'll have a mechanism for making their own determination of airworthiness, which may require having one or more of their "approved" people vet the thing. LSA, despite being accepted in some form by many countries, is a multiplicity of national standards... the Savannah S is an LSA machine, complying with the EASA definition of LSA, which I believe to be accepted in Australia.

Awfully tempting... I find the explicit retention of the freedoms of 95:10 to be a very heartening example of NOT losing the "lower end"(BS phrase, that one!)... but I do like to do the odd long X-country. 450kg is adequate, 600kg is more than enough for an efficient aircraft. I suppose my T83 COULD do long X-country flights...

I don't see a justified safety argument for going full LAME maintenance, or TSO if applicable; the whole basis of "reducaed airworthiness standards" was that GA was exceeding the ICAO target for most everything but pilot error. I think the disproportionate "safety" crap is arse covering for liability; thanks Mr Keating!

I think he's replying to you... he is making the point that "state regfistered" (VH in Oz) aircraft meet design standards that are acceptable to ICAO, and very equivalent, whereas sub-ICAO airworthiness standards are "national standards", and have no portability. ALL Recreational Aircraft are deemed to be non-ICAO, which is why they're allowed pilots with a sub-ICAO medical standard...

The Falco ticks quite a lot of boxes from aerodynamic and structural textbooks; but it gave away nothing in the looks department! A creative tour de force... I'm a bit wary of DeHavilland's comment on looks; he had a penchant for using undersize fins - have a geek at the Mosquito VMC vs stall speed through the series... It's funny how we get used to "conventional" looks, but our tastes vary with time... but I don't know anyone who thinks the Falco is ugly! I've had the pleasure of a close look at the Toowoomba one (Lynette's), and I have room for one in my hangar!

Physical contaminants, yes - the FIAT 850 Coupe used a centrifugal separator - but not the chemical upsets; neither the sulphuric acid that is active until the oil boils off the water, nor the various carbonic acids caused by cracking of the carbon chains... Unfortunately, filtration does little for the upper cylinder... after about 0.4 zillion hours of experiment and study, Ricardo (and others) determined that corrosion was the major determinate of engine life; engine manufacturers have been addressing this issue ever since... chromed bores, anyone? Nikasil? chromeed rings?

Try the second edition of "The High Speed Internal Combustion Engine", Ricardo & Glyde; or Lanchester's work for the RAE in 1916; or any edition of Judge, "High Speed Diesel Engines"; or "Diesel Engine Design" (ship engines, by whatsisface); or Ricardo's 1934(?) lecture to the SAE on the london bus engine life extenstion project; or any text on the cracking of aliphatic hydrocarbons...

Hi PP, no comment on the colour scheme... Tailfin geometry gets critical when it comes to resisting/recovering from an incipient spin; in such a case, the guidelines include: (1) all VS area aft of a line projected up and back from the tailplane LE at 30deg from the vertical, is useless. Mooney took one way to address this, Thorp (PA-28) took another; check out a PC-9. Cessna singles are BAD examples, and the reason the Cessna CG range is limited to make them "unspinnable"... I'd suggest easing your HS back 6 inches or more, to unblanket the fin and also as below. (2) Fin area below the fuselage is worth twice as much as fin above, and four times as much as fin above the tailplane (ie the blanketted bit, 30 degrees etc); see J160. (3) A strake in front of the fin - as per your models - helps re-attach flow on the suction side of the VS in an incipient spin, if it is high enough. Check out the Sequoia Falco. Pitch stability! The propellor has a destabilising effect when it's foward of the GC, and the high thrust efficiency of the 100hp 912 makes it very destabilising. I'd suggest that you use a bigger HS of higher aspect ratio, further aft than you think you need; I promise you won't be disappointed! The canopy opening thing: Another design rule of thumb is that the engine torque pulses are carried back to the main lift truss, where they are reacted by trying to flap the wings. Any number of WW2 fighters hand the enginemount bolted to a bulkhead attached to the mainspar, for this very reason. Your model has the fuselage sides cut down from ~20cm? fowards of the LE, and the fuselage as a torque tube is voided by the hole for the crew, so the fuselage sides back to the mainspar need to be pretty beefy. Rear fuselage... the rear fuselage is a torque tube, transmitting the VS -induced torsion loads fowards to the rear lift truss; the stress (shear flow) through the skin is inversely proportional to the cross-section, so the smaller the diameter (as you move aft), the thicker the skins have to be. Piper and Cessna singles normally step up one or two gauges towards the rear of the tailcone. When Petter designed the Westland Whirlwind, he chose to have a constant section rear fuselage - no taper- right back to the HS & VS spars. Nice concept, I hope it progressesw well - I'd like an RAAus Falco!

Mnk grumble, what about slotted with a 2h slot shape? Fowlers are great, but difficult to have optimally positioned throughout the extension range; and they markedly increase nose-down pitch... (so does the 2h, but not as much for the dCl...)

Totally. I think you've set out a very sensible approach. Go for that 50 hours of satisfactory operation!

Mixing 14's with 13's will "detune" the system, giving two close but separate natural frequencies - just like dynamic counterweights on a Lyconental crankshaft. This can only be good (see below). Apart from that issue, the 14s will transmit a tad more force, which is what you need to limit engine motion, etc. Replacing all the 13's with 14's will not give you that cunning detuning turnip, but will push the natural frequency up maybe 10~15%, which should make naff all difference (if there was something else on the donk that might be triggered to resonate by a 15% higher excitation frequency, it woulda resonated by now (lumps of rubber being not quite the same as tuning forks). Remember, I'm talking about an idle rpm resonance, or less, of the engine & prop. From memory, some Ponk conversions in Cessnas offer "standard" or "heavy duty" engine mount rubbers...

Nice!

i wasn't flying it much myself, aged 10...

True this, and also turboplanner's suggestion; however, the primary benefit of both w.r.t. resonance is that both minimise the rpm before ignition cut, to some way below "normal" idle, thus reducing the rotational energy quite markedly, and so the drama. I seem to recall that our 140 started to shake like a wet dog about 50 hours after we purchased it; a friendly LAME found the rubbers to be inside the wear limit, but advised their replacement, which reduced the effect to a shiver (I think we used full lean before switches off, after that). The local flying school had a couple of 172's, one of which had the same trick, and also a private Grumman on the same base. Dad's Auster never did it! You will no doubt be familiar with a number of GA aircraft that have a "no sustained operation" (or words to that effect) rpm range between idle and full power; most of these are to avoid crankshaft or prop resonances, but some also relate to powerplant/shockmount resonances.

Ahem (sweats visibly...) there are several principles at play, with regard to shockmounting an aircraft engine. Before getting to that, is your installation passing through a resonance event on startup or shutdown? Watch, say, a PA28-140* as the ignition is cut. A s the revs drop, the engine shakes the whole aircraft, and looks about the escape. This is the engine/mount/rubber system passing through a resonance; but because the resonant frequency is below the idle rpm, the energy involved is not disasterous... if your are resonating, a lighter prop - especially a fixed-pitch wood prop - should help a lot. The 9XX typically has a lower prop RPM that a Jabiru or VW, which means larger torque pulses at a lower frequency... *or anything with an O-320 on a ringmount... the Cherokee is just an outstanding example! Now, back to those principles... A basic and very important one is to separate the rubber in shear and the rubber in compression cases... rubber has a much lower stiffness in shear than in compression. This is handy, if one uses the rubber in compression to support the weight of the engine, but in shear to allow the torsional oscillations to take place without being transmitted to the airframe. That's right, we want to allow the engine to oscillate in response to the torque pulses without restraint, but to restrain it against the average torque what's pushing the prop around... (One of the advantages of the 'flat" or "boxer' engine layout is that it will have a small amplitude oscillation in response to the torque pulses (more so at higher revs)). The nifty enginemount pictured in Rogerc's post, shows the traditional approach of aiming the lines of action of the compression axes through the powerplant CG (or close to it, depending on prop weight...); this way, the engine wobbling about the crankshaft only loads the (theoretically perfect) rubbers in shear, but the awesome weight is carried in compression. From the point of view of the rubbers doing their bit, that Sonex enginemount is actually not too awful; because the shockmounts (rubbers) are close to the centreline, most of the rotational vibration is seen as shear, and because they're vertical, all of the weight is seen as compression They look a tad squashed, actuallyu, which means a bit small for the weight). Iff'n you were to replace them with slightly largerer shockmounts of the same Durometer rating, the load passed through the rubber due to weight would be exactly the same. The rotational vibration would be more restrained in amplitude - less hitting things! - at the expence of transmitting more vibration / load into the engine mount metalwork & airframe, AND slightly increasing the resonant frequency (see above - if one pushes the resonant frequency into the operating range of the engine, bad things can happed...). If you were to pull out your magic wand and move the holes in the aluminium further outboard, so the rubbers were a tad further apart, you would also reduce the rotational freedom, and reduce the bending moment on those crude lumps of angle. Again, the reduced angular (rotational) freedom comes at the cost of higher forces transmitted into the metalwork. (If you increase the load through the rubbers, but reduce the leverage on the flange, you could end up with null effect on the most obvious stress concentration...) Assuming resonance is not the culprit, and Sonex did their fatigue calculations i.a.w. MIL-HDBK-5, I would not be alarmed by the results of going up one size or ~10 Durometer numbers with the rubbers, as far as the engine mount metalwork is concerned. I WOULD be very wary of resonance for a while, and (subject to calculation) I'd make checking for cracks in the lower Rose angle radii, a part of my DI. The crude way to check for large-amplitude resonance is to sit in a PA-28-140 with a fixed pitch McHartzell during shutdown, and feel the vibe. If your Sonex does or starts doing that, you have a problem; kick Sonex... The engineering way to check for resonances is to use a V-gauge, which in this case would simply be a shallow V lying on its side, about 30mm long, drawn on the side of the cowl about midway. Set up a video camera or observer on a tripod, about 3m away from the side of the cowl, and start up, and run through as much of the rev range as practicable. On reviewing the video, if the V starts to look like an X at any stage, that's a narrow-frequency powerful vibration, probably resonant in origin. Note that the engine will almost certainly be moving a lot more than the cowl... Note that a cradle mount normally reduces the amplitude of the engine movement, by transmitting more load into the airframe. A given engine/prop combo will run quite happily hanging on the end of a rope, provided it can magically offset itself to react torque; ALL engine mounts restrain the engine, and the more a given engine is restrained, the bigger the loads (vibrational forces) transmitted...

Does anyone know what Richard Sweetapple used as a clear final coat on his later propellors? PolyUrethane, Everdure, something else?

Used to have an ex-Royal Flying Club of NSW PA-28-140 with depleted uranium aileron mass balances... DU was quite fashionable for a while!

"Cost Recovery" (thanks Mr Keating) means CASA is under-resourced too...

The Department of Civil Aviation never had a mandate to aid or foster the aviation industry; I believe the early Regs began "No aircraft shall fly, except...: Not much has changed in the current Act. Functions of CASA: 9 CASA’s functions (1) CASA has the function of conducting the safety regulation of the following, in accordance with this Act and the regulations: (a) civil air operations in Australian territory; (b) the operation of Australian aircraft outside Australian territory; (ba) ANZA activities in New Zealand authorised by Australian AOCs with ANZA privileges; By contrast, the USA seemed to think that aviation could be a good thing... Foundation of the FAA: "the Air Commerce Act was passed in 1926. This landmark legislation charged the Secretary of Commerce with fostering air commerce, issuing and enforcing air traffic rules, licensing pilots, certifying aircraft, establishing airways, and operating and maintaining aids to air navigation. " NOTE WELL: There have been at least three, possibly four, attempts in my lifetime to amend the Act to include "foster the industry"; all were defeated. The Act now includes "foster a safety environment", which functions to oppose industry growth. WHY are Australian politicians so anti-aviation? Keating said "All aircraft owners are silvertailed bastards", which was a bit rich coming from him...

Great look; i'd love to try it, though I'm a little wary about trim changes when the wing wake crosses the tailplane. Wonder about the vibration from the prop...

I'm for training. Simce we stopped spin training in GA, incipient spin accidents have become a staple... https://www.researchgate.net/publication/344638085_A_Review_of_Stall-Type_Accident_Statistics_Over_the_Past_Fifty_Years/link/5f864c9892851c14bcc698ed/download (US ref. as Aus stats hard to find). Since we stopped unusual attitude training, unusual attitude recovery accidents are on the rise. Low level training gives a chance to understand that you have to get your nose well below the horizon in a low turn; and just how many powerlines are hiding out there. Both are pro-safety awareness, even if planning is meant to prevent the need for them. I had the experience of inspecting the bloodstained wreckage of a certain RAAus 2-seater, about 20 years ago, that was - on the balance of very strong probability - downed by mechanical turbulence. The blood was from a father and young son. The height was safe, the speed was safe, the risk appeared to be small... Someone has said that 90% of pilots think that they are in the top 10%... as Nev said, let us wait and find out.

Glad you don't mind the infodumps! Soz, I'm just so glad someone is actually interested...

The turbocharger turbine outlet temperature is always lower than the turbine inlet temperature, and the change in temp (delta t) by the change in pressure (delta P) is always greater than the shaft power out of the turbine. As the pressure drop can only be negligible* - no turbine is a small orofice! - the most of the energy transfer occurs in the temperature drop. *A gas turbine jet engine has several orders of magnitude more volume flow than a piston engine of similar fuel usage; in which case, the turbine does throttle the exhaust - in effect, it becomes a small orofice. For a not overly mathematical explanation, I strongly recomment Hugh McInne's book "Turbochargers"...

Personally, I suspect an unarmed P-47 has sufficient power without boost...

One can buy WW2 superalloys off the shelf, at not vast expence, and the blades were investment cast, like almost all of the zillions of car turbos made each year. The most problematic part would be disassembling an original and measuring it to within an inch of its life.