vk3auu
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Everything posted by vk3auu
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HIRTH ENGINES Slightly off topic. The Hirth two strokes should also use premium unleaded as they have a 9 to 1 compression ratio. In the USA they have been modified to 8 to 1 and run OK on Standard. There is a character out here who shall remain nameless who has managed to demise a Hirth by running it on Standard because he thought he was going to save money.
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912 fuel Bert Flood's recommendation is for premium unleaded in 100 HP 912S and Standard unleaded in 80 HP 912. Seems OK in my old 912. David
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5 mile final If you are coming straight in, I would suggest that it would be desirable for you to be somewhere around circuit height when you get into the circuit area. That would be between 1000 and 500 feet AGL, remembering that there are still people out there without radio who are just relying on see and avoid. These people tend to be flying slower "real" ultralights and in general they are draggy machines which come in fairly steeply on final. They also tend to fly fairly close in circuits, so you need to be looking for them to come in from above you when you are on short final. Happy flying, David
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5 mile final Point taken Brent, but where I come from, it isn't considered good airmanship to fly straight in approaches, even if it is legal and you do make the appropriate radio calls. David
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5 mile final Assume you are flying a 1000 foot high circuit and you are still at 1000 foot when you turn base. If you have a glide ratio of 10 to 1 with whatever flap setting you have, you should need 10000 feet to get to the threshold of which half should be base and half should be final, so what the hell are you doing flying a 5 mile final anyway, just getting in the way of other planes. David
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Gazelle accident I'm not too sure about the gazelle, seems to be a problem with the visibility out the front. https://www.youtube.com/watch?v=cpAiYOw2HKk David
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230C as an ultralight Just to save starting a new thread. What is the point of registering a 230C as an Ultralight. The MTOW as an ultralight is 544 kg and the empty weight is around 360 kg. After you put two 80 kg people in it, that leaves only enough weight for about 33 litres of fuel plus a toothbrush. On the other hand, a 160 with empty weight around 300 kg with the same two people can carry 20 kg of baggage and nearly 90 litres of fuel and will still be a legal ultralight at 544 kg. The 170 is not quite as good from the fuel point of view if it is registered as an ultralight. David
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Plane for new pilot Have a look at the Quicksilver GT400. It is a nice cheap rag and tube real ultralight which should be easy for a newly trained ultralight pilot to handle. Stay away from gyro's unless you can get a very good instructor. We have lost 3 gyro pilots around here in the last 15 years, 2 while learning to fly. I also know another who used to live around here who got killed. Happy flying, David
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Whats going wrong in Recreational Aviation lately?
vk3auu replied to a topic in AUS/NZ General Discussion
Tony, you have articulated many of my concerns about the reporting and publication of accidents. A couple of years ago at Narromine I was eavesdropping on a conversation regarding a recent non fatal accident which had resulted in major damage to a popular make of aeroplane, enhanced by what seemed to be a major manufacturing defect. I waited for a report of that accident to appear in the magazine, it never did. I have my own suspicions as to why, but an AD should have been raised and it never has either. Let us hope that a new culture is born with the advent of a new Executive Director. David -
Sapphire A couple of my friends have owned one. Nice aeroplane. My impression is that they are better with a Rotax 447, not the 503. The latter tend to be thirsty beasts and you don't get much better performance. They need a fair bit of strip as they seem to fly in ground effect forever. The later ones may be better. David
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GA vs RAAus GSA, Captain et al, The alternative is of course already there if you want/need to fly above 5000 feet and use flight following quite legally. Register your aircraft as GA and get a GA licence. I believe that is what Brentc has done. That way your Jabiru 230/430's will also be legal up to 750 kg MTOW. I think I have those numbers right. David
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ADSB J430 "I beieve that we all should have the subsidised ADSB transponders." Yea and amen to that. David
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From Greg "I think it's possibly one of the most underutilised facilities as far as RAAus is concerned and certinally an area of leverage should we ever want to get the 5000 ft limit raised in the future." Perhaps I am being too cynical in my old age, but my impression is that if a whole raft of Ultralighters start using the system, then someone, namely the rest of us will be expected to make a contribution towards the provision of the service. It might also make the powers that be think that just because some of you have transponders, there is no reason why all of us shouldn't have them. I still haven't seen anything in the regs which allows us to fly above 5000 feet just because Flight following is available. Perhaps if enough people put up a case we might get that priveledge, no doubt as an addition to the cross country endorsement, but for the moment I think you are pushing your luck. Use FF if you will, but stay below 5000 unless it really is "Operationally necessary" and by that I don't mean necessary to stay in contact with FF. David
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There is also another gap south of Yea called the Glenburn Gap. I don't have a current VTC at hand at present, but I believe you can fly at a greater altitude below CTA that way and it takes you straight to Coldstream of Lilydale. David
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5000 foot ceiling J430 makes some very valid comments. Middo also had something to say along the same lines a couple of months ago in the magazine. I might also point out that a lot of the country which is above 4000 feet is also tiger country, so you shouldn't be flying over it anyway. From my own observations flying cross country to Narromine, most of the ultralight pilots who are flying above 5000 feet have not made the appropriate radio calls when they have entered these levels and some still do not seem to be aware of the heights at which they should be flying according to the hemisphere. Better to stay below 5000 and keep out of trouble. David
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Brent, as an outside looking in. Perhaps your problems there are a result of the engine running too lean. I sort of gather that from the fuel consumption figures that you quoted a week or so ago. I wonder whether there are a few more engines out there that aren't perhaps flown as much as yours that are about to spit the dummy too. For an engine with a TBO of 1000 hours, it should be standing up to the sort of use you put it too, a lot better than it has. David
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HKS 700e Look it up with Google David
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Whats going wrong in Recreational Aviation lately?
vk3auu replied to a topic in AUS/NZ General Discussion
Quiet up front One of the problems today is that most people are learning behind more reliable engines, not the two strokes that some of us older ones had to master and they don't know how they will react when it actually does go quiet up front. I have had it happen twice so I can speak from some experience. Once was a broken crankshaft in an old Rotax 503 and the other was running out of fuel due to a headwind 8 minutes from home which was completely my own fault because I had the throttle open a bit more to compensate and the fuel usage was just a bit higher. It does make you much more cautious about the sort of terrain over which you fly. David -
Airspeed, Groundspeed, TAS = Performance Confusion
vk3auu replied to Admin's topic in Student Pilot & Further Learning
RPM S&L vs T/O Mike says "The thing is that you can only get 5000 rpm out of them flat out on takeoff and about 5100 rpm max in S&L." That doesn't seem to gel. It must be way too much pitch. I was running a 3 blade GSC ground adjustable and on take off at 50 knots it only got to 5000 but at full throttle S&L 83 knots it got to 5800. The GSC blades are very rigid. I swapped it for Sweetapple prop which was very flexible and on T/O it ran at about 5500 but was still only 5800 flat out S&L. The interesting thing was that I had to use full right rudder on take off to stay on the strip with the Sweetapple as there was so much extra power. I had a copy made but it wasn't anywhere near as flexible and I couldn't get the same revs on T/O although it was the same flat out. David -
I had a sit in one with Stan Jarman at Holbrook at a flyin at Easter about 12 years ago and we came to the conclusion that with the appropriate engine, it would be a very desirable aeroplane. This was before the Rotax 912 was available. David
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Odessey Battery Can someone tell me what the size of the battery compartment is in the Jabiru. Seems to me that you are paying a lot of money for what is turning out to be an inferior battery. I just paid $120 for a 110 amp-hour deep cycle battery for my caravan. David
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Battery I have had a Yuasa Gel sealed battery in my CH701 for 9 years and it still turns the 912 over on a cold morning. I'm not sure of the size but it weighs 5 kg. David
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Airspeed, Groundspeed, TAS = Performance Confusion
vk3auu replied to Admin's topic in Student Pilot & Further Learning
Mike said "Their speeds equate to a 75% cruise of 133 knots at 4550rpm." The graph that you got that from is what you get using a dynamometer and getting the maximum power at that speed. The graph in the Owners Manual for the 912 UL shows 75 percent power as 5300 rpm, the actual curve with a fixed pitch propellor, goes the other way as a Y = X^2 graph will go. 5800 80 hp 5500 69 5000 50 4500 37 Fuel consumption seems to be proportional to power, around 0.45 lb/hp/hr. That is close to 17 litres per hour at 0.75 percent. I presume the 912 ULS would be about 20 percent higher. -
Airspeed, Groundspeed, TAS = Performance Confusion
vk3auu replied to Admin's topic in Student Pilot & Further Learning
ASI errors Don't take your ASI readings as gospel unless you have checked it out with a GPS. I generally fly around in a big circle at a constant indicated speed on the ASI and average the max and min GPS readings. If you do that for a few different speeds you will get a fair idea of what is what. You need to repeat the whole exercise at different altitudes too as the true speed get faster the higher you go. From what I have seen there are quite a few aircraft out there that don't fly anywhere near as fast as their owners fondly believe. A couple of rough rules of thumb. Engine power is roughly proportional to the square of the engine speed with a fixed pitch propellor at a constant altitude. 75 percent power is obtained at 8500 feet at full throttle. At the top end, required power is roughly proportional to speed squared as parasitic drag is proportional to speed cubed, but induced drag is inversely proportional to speed.