Bruce Tuncks

Yes onetrack, and I agree about the magenta line being a concentrating factor. That is good advice to stay away from it. With gliders, you also have thermals and clouds. This is why you have to wear a parachute for competitions , and they do get used from time to time. A Libelle once lost a wing outer ( halfway along the aileron! ) and the wreckage landed on a Narromine street. The unhurt pilot didn't even fly the task before landing. Harry Schneider kept that wing for the next 20 years in the hope of using it in a repair job.

I once worked out that if 50 planes were flying at random over australia's wheat lands, there would be a mid-air once in 20,000 years on average. The workings included that the pilots were not looking out at all and there were no concentrating factors, like GPS tracks and airspace boundaries. Has there ever been a midair in Australia in the absence of concentrating factors ?

I stopped using a 550 METRE farm strip because of discomfort. And yes the approaches were not the best. One direction involved coming in over the shearing shed, only 100m from a fence at the start of the 550m. These days, I use the town strip, 1000m of bitumen. What a wimp, I hear you say.

I have wondered about skeleton spats for the Jabiru. the wheel is exposed, and the spat consists of a front and rear fairing . This makes pumping up the tyres easier and keeps the spat slimmer. They don't look good though. Anybody tried them?

You could get Rotec heads for your Jabiru, RF, and try that.

My son, the stuck-up Lancair owner, says struts cost 15 knots, but what would he know. When I sharpened the trailing-edge of my old struts ( yep, they were real round at the back), I hoped for 3 more knots but alas I can't see it. Later Jabirus have a different strut extrusion which is already sharp at the back. I have been told though that there is a law of diminishing returns on aerodynamic improvements so bugger it you can't do ten things at 3 knots to get 30 knots.

Carbon is a lot stiffer than glass, and this is good and bad. With glass, the resin fails first and this gives a milky appearance to overstressed areas. Not so with carbon. Carbon dust also kills you faster than glass dust. Carbon is biologically more active. BUT carbon is lighter.And stiffer. Modern big-span sailplanes have to use carbon or the wings would twist and muck up the spanwise loading. If you wanted to make a super fast Jabiru you could make cantilever carbon wings instead of the strut-braced glass ones. This would give you about 15 knots and cost about 30,000 dollars. It would also make it unrepairable, at least by a mug like me. Personally, I like glass better and yes I know this shows my age.

What I can't understand is why they are so bad at the quarantine stuff. In the olden days, they used islands... today they fly people in from india and give them only 14 days in a cbd hotel!. No wonder we are getting new cases all the time, then they do ridiculous restrictions on people who have never even been near a covid case.. I bet if they used islands, or remote camps, and had an extra 2 weeks spent in quarantine without contact with new arrivals, we would be clear of the virus by now.

Alan, you are doing the right thing by getting the issue up front. Just how they can say that your insurance is invalid if you made a claim that had nothing to do with the strip is beyond me. Personally, I don't believe in insurance. I would rather pay the premium money out on building a fireproof etc house.But that's just me. I know of others who have had a great response from the insurers. The Alice Springs Gliding Club comes to mind.

Markdun, you are being a bit unkind to Cook. He was able to navigate using the lunar angular distance method for longitude. There were only a few people in the world at the time who could do the maths. I sure can't.

Wow spacey, those railway guys took it too far I reckon. But oil-testing is an example of how the newer maintenance systems are just as rigorous as the old ideas were. Mike Busch uses oil analysis to detect aero engine problems a long time before any symptoms show up say on a leakdown test. Alas, Jabiru engines do not have the database to use oil analysis, or so I have been told.

I have wondered about "gull-wing " baffles on the top of the cylinder walls and heads. Following the Limbach example, I put these on the underside of the cylinders, with the idea of keeping air in contact with the fins for longer. Now I am thinking of swapping them to the top or adding them to the top as well and having both top and lower baffles. Any comments?

It's not quite that simple Onetrack. Waddington's stuff was top secret, and it was the 1970's fuel crisis which led to the rediscovery of reliability centered maintenance. This rediscovery was quite independent of Waddington. I would guess that his work is still unknown to our airforce. But I do have to say that in looking through the Jabiru maintenance schedules, I cannot find much unnecessary stuff, and this supports your argument. Maybe replacement of filters and spark plugs, but as stated earlier, the factory has little choice but to assume the worst possible operating conditions. Getting back to rubber hoses, I personally have replaced them as per the official schedule, but I do think this is too often as there has never been any sign of deterioration in the old ones. 4 years is considered "often" for automotive stuff, which usually lasts ten years. The same goes for the filters and spark plugs. Jabiru do give a warning about getting oil on the new hose-joint and thus making the new hose more likely to blow off. Yes this stuff is cheap for Jabirus, but costs thousands for Rotaxes. There was a car ( I think a mini ) that had a warning light for oil-filter replacement. This light was controlled by a differential pressure switch and the filters lasted years and years. My guess is that the filter-makers persuaded the carmakers to stop fitting this warning light.

Yep, spacey, I have done exactly that with fan belts. You take off the old one to replace it with a new one and then you wonder how long the old one would have gone for... possibly years. So instead of putting it in the bin you carry it as a spare.

Nev, read the second sentence again... " some maintenance jobs enhance reliability and some do the opposite". I reckon you have fallen into the trap of thinking that maintenance is so good that you can't have too much of it. Reliability-centered maintenance is the subject of books these days and the message is NOT one of neglect at all. There are some actions, like changing the oil, which enhance reliability. The other things you mentioned like tread depth and tyre pressures are also in this category. There are other actions, like replacing perfectly good hoses, which detract from reliability. I was a mate of this guy who flew helicopters in the airforce. He hated the first flight after maintenance as there would be something wrong for sure. From your response, I don't think you know the Waddington story. He faced a lot of the stuff you have come up with but, amazingly to me, he got his way and doubled the reliability of those Liberators. I reckon he must have had powerful backing, possibly up to Churchill, to do this. He was not a pilot or an engineer himself, but he was a good scientist who believed in evidence. Of course, the Waddington stuff was top secret and unknown for many years.

2 readings are worth doing here... I'd start with Mike Busch. Some maintenance jobs enhance reliability and some do the opposite. It takes some knowledge to see what is what here. Reliability centered maintenance is quite a science now but as Mike Bush says, this has gone unnoticed by GA. In ww2, a prof called Waddington vastly improved the reliability of a squadron of u-boat killing Liberators by doing LESS maintenance. Yes, it is intuitive to think " maintenance is good therefore the more we do the better" but this is just not so. On rubber hoses : I reckon these are highly inspectable things and you squash them too see if there are tiny cracks showing in the tension surfaces, also you feel their elasticity. How often do you replace them in your car? But if you were Mr Rotax, of course you would assume the worst possible case for rubber deterioration. There was a Jabiru landed on the Sruart Highway because of a tiny fault caused by replacement of the fuel hose. I could cite other examples, but the message is that maintenance is quite a dangerous thing to do. And as for airliners, their increased reliability is partly due to their smaller maintenance lists.

My Jabiru kit came with a motorbike lead-acid battery which was not good enough to start the engine, well after I left it on a small solar charger for months. It was replaced with an Odyssey, which performed well for more than ten years. It is still going, that battery, these days on a farm buggy. I am sure Onetrack is correct, but I didn't know that stuff at the time. The reason for replacing it in the plane was because of weight. A LiFePO4 was 5kg lighter! and much cheaper too, from a chinese hobby online shop. ( without the charging electronics and the case which looks like a regular car battery) These lithium batteries are not as robust as the odyssey, and I am on my second lithium after about 5 years, on account of buggering up the lithium battery by leaving the master on. ( I had done this with the Odyssey, and it came good again... one tough battery, huh.) My advice is not to change to lithiums unless you are quite expert. There are types which are dangerously flammable, their voltage is not compatible with simple charging systems and they cannot stand terminal voltages outside a narrow range. In particular, don't be sucked in by a " lead acid equivalent" figure.

Once I was doing a passenger flight in a glider, and the passenger was a hang-glider guy, so I gave him a go on the controls. He was so good that I took my eyes of the tug to look around. On looking back, NO TUG! After a frantic search, I found we were formating wingtip to wingtip. So I learned the hard way. Yes I still give people a go on the controls but now I am more careful.

Roundsounds certainly agreed with my local gliding club. Before going solo, everybody had to show they could fly with the asi and the altimeter covered. The instructors had little round covers with suction cups for just this purpose. Most of us flew the circuit about 5 knots faster than usual.

Thruster, no criticism of you was intended. But I have to say that SID (Sudden Infant Deaths) doesn't make me think of Cessnas at all. Anyway $20,000 dollars seems a good price. They were a lot more expensive in the Aviation Trader my son gets. One big Cessna was over $200,000!

Kasper, can you confirm that the Rotax crankshaft is made up of pressed-together bits? Just like a lawnmower? If so, I am surprised that it was ever certified but I have to say that you don't hear of them failing often.

This is just what the old air-cooled volkswagens used! I loved the sound, but how much power did it consume?

I like the idea of 150 to 160 being the max temps for a Jabiru engine. This is what I achieve in practice as on a hot day the temps can exceed the 150 "max" on climbout. But anything over 160 and it is time to panic. The first Jab engines were redlined at 200 C and this was way too hot, as evidenced by the distortions in the cylinder heads. Then they lowered the max down to 175 degrees which is still too hot in my opinion. BUT cooler running on avgas turns up another problem.

If you look up stuff on wind gusts as written for wind energy turbines, you may see it claimed that the strongest gusts are 15 degrees off the main direction. This is clearly because of the thermals mentioned before. The only advice I can offer is to expect side-gusting on a windy day. At least, near the ground, the vertical motions of the gusting are no longer there.Imagine how hard it would be to try and land on a mesh runway at 2000 ft.

oops, the word is obfuscation.