Bruce Tuncks

I just looked up "car parking aids" and they have ultrasonic stuff too. Surely somebody has tried one for flaring out?

I looked up the Sea Rey website where they have an ultrasonic thing which has the audio signal Spacey suggests and I agree with. The rationale is that the water is sometimes too glassy to see it properly. I would like to try one just to make my landings easier. Yes, I appreciate the comments made about learning properly, but it is still the hardest thing in flying I reckon. And I don't fly a seaplane, just the Jabiru.

Thanks RF guy. I grappled with the question of glider ventilation air for years before coming to the view that there was no zero-drag solution. you take in air at the relative airspeed ( 80 knots say ) and then let it out at zero knots relative to the glider. So each kg of ventilation air costs 840 J. This can only come from the potential energy of the glider so it costs a 300 kg glider 0.3 meters of height. Airliners knew about this and so they recirculate the stale main cabin air all day. Only the pilots get fresh air. Mind you, with the gliders, there are worse ways to get rid of excess ventilation air than a reverse scoop at the fuse fattest point., so the .3m would be the best you could do.

The detail design of the airflow from the opening to the radiator is very important. You need to avoid separations and steps and leakages. Thats a very good question pen-name. I don't see how a bigger radiator could be less drag, but there may be a way. I don't think Rotax engines are completely liquid cooled , It is only the heads. A coolant leak when at a remote location can be very expensive. Often times, you are not allowed to fix it yourself, so you are up for charter flying a lame in n out.

I thought that the legal reserve was 40 mins flying time, which is 11 liters for a 2.2 Jabiru. I just don't know under what circumstances it is legal to use some of this... maybe none ! Personally, I have never used any reserve so I need some help here.

It would have been OK if he had done the check earlier. As it was, he did it just as he was lining up for take-off.

There was a Jabiru in SA which "landed" in a vineyard. Apparently the student pilot turned off the fuel when doing his pre take-off checks. There was just enough fuel in the bowl to get airborne and past the runway. I'm pretty sure they were uninjured because the instructor took over and they came down between rows.

Apparently it really happened that a Stralian Quantas captain said "welcome everybody here today" A group of Pakistanis got really upset at this and they sent a spokesman up to tell the captain.. " we did not come here to die, we came here to fly to London"

I think it was Old K, but somebody tufted a plenum and found that the air flow directions were sometimes not as our intuition would expect. For example, airflow near the crankcase center was forward ! So I learned from this that you needed to test out theories first, and tufting and photographing was a good idea. Once, this was done on a glider wing and it was found that the flow on a glider aileron was ALONG the wing towards the fuse on the top surface. A separation lay ahead of this flow.

We used to have quite a few foreign students, some of them wore coke-bottle glasses and spoke poor English. I reckoned that they were the sons of Indonesian generals and they were going to become airline pilots. Hopefully back in Indonesia. Back to radio transmissions... I rarely hear the place of origin mentioned even on unicom 126.7, where it could be lots of places. You can only tell they are a long way away because of the poor signal strength but it would be good to know for sure that they were at Naracoorte for example. Yes, at the beginning and end of each transmission is correct. And, Turbs, I don't think there is a strip at Natimuk. Be good if there was . ( I know you didn't say there was a strip there, but you got my hopes up. ) Yes, standard phrases can sometimes be helpful but plain English is better I reckon.

I have both, and I much prefer the android galaxy because it is easier to use. My smart son says that the Apple has more features, and I am sure he is right. But I want less features and easier to use. Here's the explanation... every feature requires a command. So you pick up the thing and if you have your fingers touch something, you get some feature you didn't want.

I've never heard of an aircraft failure due to debonding, although I have heard ( but not seen ) a Jabiru undercarriage leg which went "soft" due to disbonding within the leg. This leg did not fail, but was nasty to handle on the ground. Anyway, a question for you boat experts... Are those black sails on some leading ocean racers made of carbon? Since when did carbon fiber become used for sails? are they much lighter? what about their porosity? Could ( should ) I consider carbon u/c legs for a Jabiru?

I like and agree with your wish-list skippy. With water-cooled heads, you shouldn't have too much of a problem keeping things cool enough. My suggestion is to shamelessly copy sizes etc from a known good-performing plane with that engine. The Dimona comes to mind for me. If I were starting from scratch, I would look carefully to see if simple cowl-flaps could be put in too, but this is just a thought bubble. In a recent eaa article, they paid attention to streamlining the air exit from the lower cowl. Wow, drag can occur anywhere.

I don't know anything about boats turbs. Of course you can under-design anything . Bet I too could under-design a boat part. The earliest fatigue tests they did on FRP consisted of a rotating shaft of FRP with a cantilever end carrying a weight. So the inboard end of the shaft had a cycle of tension and compression for each rotation, and the weight and geometry gave any stress you wanted. And you can compare different metals with FRP using this. Set the thing to be driven, and you get millions of cycles of stress in time. 3,000 rpm gives over 4 million cycles in a day. This was done over 60 years ago, and the main finding was what I said. FRP does not fatigue, well not in the way metals do. The individual strands of glass are crack-stoppers and they don't form a contiguous medium in which a crack can grow. Sure enough though, if the stuff is over-stressed, the resin powders over time and the part fails as the glass strands are left unsupported. This is called a greenstick fracture and I guess this is what happened to those boat transoms. It just may be that the materials between boats and planes differs too... planes are,or should be, made of high glass to resin layups with glass cloth and ( usually ) epoxy resins. These days, the glass has largely been replaced by carbon, which gives good and bad changes to what i've been saying. But not in Jabirus, thank goodness.

Here's the deal on fatigue and frp... THE STUFF DOES NOT FATIGUE. There is a type of overload failure where the resin can turn to powder and gradually a greenstick failure will ensue. Fatigue is a metal failure where cracks grow between metal grains. Look up the story about Blanik gliders, wooden gliders, the Janus project etc . Fiberglass "fatigue" is an invention of bureaucrats which has no basis in reality or evidence.

Yep, I would suspect the sender first. An electrical connection sure could do that. I have EGT on all 4 cylinders of my SK jabiru, and I don't use it much now that the 4 cylinders have been equalized. I was surprised how different the cylinders were to start. I don't see much use in the EGT figures except to show if the cylinders are the same like you want them to be. Remember you are just reading the average temperature of a probe, and this probe gets a blast of hot gas for 45 degrees in every 720 degrees. Apparently the "real" combustion temp is about 2000 degrees C. So the difference in 700 to 740 is not that much. Did the CHT show a change?

Hear here says me.

Old K, your point is a good one and more true for wood and fiberglass planes than metal ones I think. Once I saw the Janus fatigue-test rig at RMIT in Melbourne. It was being abused far more than any real-life plane I had ever seen, and the reason was that they had measured the wing and found it was 5mm thicker than designed. Any natural or hand-made thing has a range of strengths, so of course the authorities have to apply a big fudge-factor. Here's another example.... "smooth air" can, I have been told, contain a sharp-edged upgust of 15 knots! In all my 3000 hours of gliding, I only found a thermal that good a couple of times. And that was flying on good days and looking hard for thermals. This makes me wonder about all the ASI markings we live with. And, it makes me wonder about if that fudge-factor has been made too big.

You are more the average, kgwilson. I reckon that Nev is right again and hours ain't hours, well not all hours are the same. My new Jab has an autopilot and when that is doing the flying, how can you compare that hour with say an hour doing circuits or aerobatics? AND, to confuse things even more, there is the possibility that not all hours are properly logged on account of how logging hours brings up maintenance costs. I know that nobody here would even think of doing such a thing, but I also know a service guy who says that private hours in the log need to be doubled to get the reality. Apparently stock roundup helicopters in the top end have come to grief by overdoing this tactic.

Correction.... I looked up the span of the nimbus 3. It can be 22.9 m to 25.5m, depending on the wing extensions in use. Wow, says me, my jabiru is nearer 8m.

The effect is very noticeable in thermalling gliders, where you are often applying opposite controls to keep the glider from steepening its turn. And, as usual, Nev is correct. The effect of bank is to make the speed of each wing more equal. Once I watched in awe as two 21m span nimbus 3 gliders were thermalling very tightly and approaching that impossible 90 degrees of bank. Actually the dihedral and flexing meant that the tip of the outer wing was close to 90 degrees, but the inner wing was less. And yes they were climbing in a tight thermal core and going up fast. I dunno how hard it would have been for them to shift their circle, but it was a great example of how open class gliders really are better.

The JAb takes about the same fuel to get to the farm as the car... but it does it in less than half the time. Mind you, it can't carry gear like the car can. Both their engines are similar, but the Jab engine is working harder I think. The plane has to keep airbourne, so the induced drag has to always be there, while a car only had parasite drag.

I reckon the SK was quite hard to control on the ground when going fast. The 230 is much easier I reckon, but then that accident was a 230... Once, a fellow pilot passenger ( but he was over 80 ) lost control of my SK on take-off. I had to take over. He was not using the rudder enough.

While I understand Turb's worry about shock cooling, I reckon that this is more likely to cause cracking with a more brittle alloy than the Jabiru heads were made of. But why increase the water? I thought the first system gave you the bit of extra cooling you needed. Minimal flow-rate gives less weight of water to carry. Anyway, we sure appreciate the work you are doing on this project.

Thanks old K. If the water injector setup is enabling you to keep the temps under 160 C then that is just great.