Dafydd Llewellyn

Ta - hadn't come across that technique; sounds no bad idea, but it has nothing to do with crankshaft torsional vibration stresses.

JJ, what do you mean by "dynamic prop balance" ? The term "dynamic balancing" means to me, a form of balancing that spins the rotating assembly and measures the reactions by load-cells or accelerometers at the supports. This method is capable of detecting "moment" out-of-balance, which cannot be detected by simply allowing the assembly to find its point of balance when resting on a couple of smooth rolling surfaces ("static balance"). A propeller that is badly out-of-track will produce a "moment" out-of-balance, even though it may be in static balance. If this is what you mean, to do this for more than just the propeller, then I don't see how one could do this except by removing the crankshaft from the engine, bolting the propeller to it, and dynamic-balancing the assembly. (One can dynamic-balance car wheels using the vehicle suspension; but I don't think this can be applied to a complete aircraft engine). If, however, you are referring to a crankshaft torsional damper, such a damper has nothing to do with propeller balance. The crankshaft has a "flywheel" mass at either end - the propeller at the front, and the ring gear assembly at the rear. The crankshaft acts like a stiff spring, connecting them. This system has a natural frequency, and to the extent that this frequency is excited by the firing impulses, the resulting torsional oscillation will add to the loads being carried by the flange attachments at the front and rear of the crankshaft. A torsional damper acts to absorb energy from this torsional oscillation, which tends to reduce the oscillatory torsional stresses , thus helping to reduce the loading on the flange attachments. The belt-driven alternator acts this way, whereas the mass of the Jab alternator magnets adds to the flywheel mass at the rear end of the shaft. I do not know how significant this change may be, but it's in the right direction.

I didn't think we were arguing about the Mildura one on this thread - it has its own thread.

I think we all knew that. We have one J 170 which we believe, on the basis of hearsay, to be a fuel exhaustion due to uncoordinated flying situation, having come down with some fuel in the left tank, but we don't know how much; and one J230 with Lyconental power (not sure which, but probably Lycoming), having come down due to "fuel exhaustion" with one tank about 60% full ?!&**? Or do I have that wrong, again?

New Zealand would be the place to start, I suspect.

Good question. Next question? . . . . The whole recreational aviation situation is based on a structure of exemptions, under the 95 series CAOs. It "just growed" that way, like Topsy, because under the old regulations, that was the only available way to do it; CAR 308 allows CASA to make exemptions, and it goes way back to the old Air Navigation Regulations, and the GFA hauled itself together about 1947 or whenever, and applied to DCA to be allowed to manage itself via such an exemption. That mechanism, in one form or another, was copied by all the other recreational bodies as they reached the point of being able to do so; and DCA/CAA/CASA saw this as a useful way of unloading the work of administering such "fringe activities" to the world of the airlines and GA. The result has been a whole bunch of administrative bodies, each with its own patch of turf which it defends furiously, each with its own set of overheads, and each being somewhat parochial. The exemptions are handled somewhat differently in each case, so there's no uniformity. In America, it is all handled by FAR Part 91; and the whole of experimental "category" is covered by a couple of paragraphs in Part 91. I have not studied the details. In Britain, there are the British Gliding Association and the Popular Flying Association - and they work fairly autonomously, and seem to do a pretty competent job of it. I'm inclined to think that we should examine these other countrys' ways of doing it, and see where our way could be improved. I do not think AUF/RAA were altogether wise in the way their modus operandi was established.

No -that was a twin-engined aircraft in disguise. Westland Wyvern. (And Wright Flyer, if you think about it). Adverse aileron effect always increases with increased wing span in proportion to fuselage length; that's why doing some early training on gliders is good for curing "lazy feet". To a degree, it's a price you have to pay for increased aerodynamic efficiency. However, I agree that quite a lot of aircraft seem to have their vertical tails designed by eye; and what we are accustomed to thinking of as "pretty" in this regard is based pretty much on WW2 fighters - almost all of which had vertical tails that were barely adequate; you only have to look at the development history of the Spitfire - its vertical tail almost doubled by the Mk 24. As my flying experience increased, I found myself increasingly irritated by aircraft with inadequate directional stability, so I know what you mean. There are quite a lot of aircraft I'd walk way from, too. Also, most vertical tails are, even now, incorrectly designed for spin recovery. If the designers MUST imitate the F 86 swept tail, they could at least learn something from the evolved form of it on the F-18 - it has two of them, and each is large enough to be worth hiring as advertising space . . . Another aspect of this problem is improper control harmonisation; and both the early Jabiru and the Skyfox suffered from this; the rudder forces were too light, so it had very little "feel". Quite a few gliders also have this defect; the H201 Libelle and the Ka2 were amongst the worst - but people get used to them and love them (I didn't). I've not sampled much of the current crop of recreational aeroplanes, they don't turn me on, so I can't comment on them; but the desirable control harmonisation is generally considered to be that the ailerons should be the most responsive control relative to the pilot effort; the elevator should be twice as "heavy" as the ailerons, and the rudder twice as "heavy" as the elevator. I've found many gliders and such recreational types as I've flown, the opposite way round - the rudder is lightest and the ailerons heaviest. This does not make them good training aircraft, I should imagine. Once you'e experienced an aircraft with correct harmonisation, the others become quite annoying to fly. So I agree, Turbs, but that does not answer the question. Adding rudder trim is treating the symptoms, and it's something you can forget in pre-take-off checks and it can be a real nuisance in an aborted landing.

Best rivetting gun I've come across is a Sioux. Not cheap, but having tried to do it with a cheap air-hammer, the extra cost is well worth it.

So how would you fix it, Turbs? 99% of single-engine propeller-driven aircraft are fundamentally assymetrical; only the ones with contra-rotating propellers are not (Seafire 47, Macchi-Castoldi MC72, and I'm sure there was another one . . .). I'd dearly like to know how, and I've been studying aircraft design for 50 years. (Contra-rotating props are out of the question nowadays, due to noise regulations).

Are you being logical AGAIN? I've spoken to you about that . . .

Ta - that clarifies it. Candidly, I try to avoid non-return valves in fuel systems if at all possible; they have to work at such minimal pressure differentials that they are a considerable reliability issue; and extremely difficult to check in many in-tank installations.

OK, it's a while since I looked at a 160, and I've never looked closely at a 170. In that case, an outboard pickup running down the lift strut would work well, I believe. It would be "messy" for rigging and de-rigging, and may increase the risk of fire in a crash, those aspects would need to be assessed against the design standard. It would also allow the header tank to drain to the low wing, unless it had non-return valves - which introduce a diabolical "hidden function" into the equation. The overall benefit of this versus simply teaching people to fly coordinated seems dubious.

I think you'll find the tanks go all the way to the wingtips; they did on the prototype. However I suppose an outlet at the tip than ran inboard to the lift strut and then down inside the strut might siphon.

Depends how fast you get there, doesn't it? The CA21 Skyfox had an Aeropower, and cruised at close to 70 knots, as I recall, tho it was more comfortable at 65 or so. It was a smooth, civilised sort of an engine, but you had to let it climb in its own sweet time.

You miss the point, Andy; that much endurance allows you to fly to a site , say 300 miles away; (with a piddle-stop on the way if you need it); and after you have dome whatever you needed to there, fly home again. A short endurance means you have to fly to where there is fuel. A long one allows you to get fuel where you want to.

Not in GFA. Gliders (and motor-gliders) are registered VH. They do not HAVE to be maintained by a LAME; they have to be signed out by a GFA Glider Inspector holding the appropriate glider maintenance authority.

Yes, it's a very effective fuel system - but you don't get 8 hours endurance out of it.

Be careful how much mass you add to the wingtips; and keep it as far forward in the wing as possible, otherwise it will adversely affect the flutter margins of the wing. If the pump has a reasonable suction head capability, (and it wouldn't need much - half a metre woulfd be ample) I'd be inclined to locate it in a modified lift-strut fairing.

The 582 will spin a larger propeller than the aeropower; at the slow speeds these things fly, that makes a big difference.

Erhm - I trust you'll excuse me, but see attached . . .

Simplicate and add lightness . . .

Provided one could arrange matters so the pump only ran when there was fuel at the outboard end of the tank - a mercury switch, perhaps? Because those pumps wear out pretty fast if you run them dry.

ATSB is always careful not to attribute blame; their function is to discover the cause in the interest of increased air safety. The wrangles over blame come in civil court cases afterwards. FT, what is the source of that post? I bet it was NOT ATSB; looks like CASA to me. CASA and ATSB are entirely separate organisations. I'm not convinced that what those documents say is correct; the torque has to be transferred by friction, achieved by the clamping force generated by the bolts. Dowels only come into play after movement occurs due to inadequate friction - i.e. when the thing is already on the way to failure. In an attempt to improve the effectiveness of the dowels, people make them a tight fit - so the clamping force is reduced by the force necessary to push the dowels into their holes. Further, pressing dowels into the end of the crankshaft results in a minute amount of "bulging" of the metal around the dowels (and there isn't much of it!) which reduces the area of contact by which the friction can work to transfer the torque. If I had a -19 Jabiru, of any description - but especially if it used a Jab 3300 - I'd fit Ian Bent's belt-driven alternator - which as well as supplying more electrical power and also being a 3-phase field-regulated device, ALSO acts as a crankshaft torsional damper.

That also happened on my PA 28 - and it had plenty of dihedral, and short tanks. It's not really an issue of dihedral; it will happen in any aircraft unless the fuel shut-off valve isolates the tanks when in the "off" position - and many of them don't. The alternative way to stop that is to use a "cross-over" vent system; but you end up with a multitude of drain points to check every morning, because the low points in the vent plumbing must have drains to remove any water that may collect there.

Yep. That's the way it works, on the VH register.