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Bruce Tuncks

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Everything posted by Bruce Tuncks

  1. Bruce Tuncks
    There is all the difference in the world between entering cloud with a hidden mountain close by and entering a cumulus cloud based at 10,000 ft over flat land. They were in great danger, but the danger came from hitting the mountain and not from hitting the cloud. Close proximity slope soaring is dangerous enough without doing it in conditions with cloud like in the video.
  2. Bruce Tuncks
    Here's my figures... my new prop has a 44" pitch so it would have a no-thrust forward speed of 44/(12times 6076) n-m/rev. So at 3000 rpm, the no thrust speed would be this times 3000 times 60 or 108knots. This is smaller than I expected. It means my plane can never get to 108 knots at 3000 rpm. Slowing to idle of 1000 rpm, the no-thrust speed is now 36.2 knots so a glide of faster than 36.2 knots will produce negative thrust from the prop. But the idle speed is higher when you have the windmilling effect helping the engine turn over. At 1700 rpm, the no-thrust speed is just over 60 knots. I have never done this calculation before, and I think that my idle speed on the glide has been too high for me to notice the drag from the prop.
  3. Bruce Tuncks
    Regarding "negative thrust" from a rotating prop at low rpm, while I understand the theory, in practice I find this hard to see in the air or even with a model plane. It seems to me that any rpm helps a bit, and though I know this can't be so, it is what I think I observe. For some years, I crewed for my son in model-plane aerobatics competitions, and the guys there said that an idling prop was more drag than a stopped one, and they were better pilots than me. Even knowing all this, I still can't see it with the Jabiru.
  4. Bruce Tuncks
    I agree with the idea of flying with a gliding instructor in a real glider to test this stuff out. There have been some awful crashes into flat paddocks following engine failures, and it is possible that the hitherto unknown sound of silence causes some pilots to panic. So, because Kensla is correct about some engine rpm causing more drag than a stopped prop, and Facthunter is correct about the risk of a restart failure, there is no other safe way to experience a real engine failure.
  5. Bruce Tuncks
    My idea has been to get model plane vibration meter and wire it to an instrument like maybe a milliamp meter. This would tell me if there was more or less vibration. My senses are not reliable enough to do this alone. I would like a Balance Master but need to understand how it works. My intuition says a liquid will migrate to the outside and make things worse. Smarter guys than me say it works good, so I am still wondering where my simple ideas are wrong.
  6. Bruce Tuncks
    Just imagine that the force of gravity was different from inertial force. We could have a much better artificial horizon and cheaper too.
  7. Bruce Tuncks
    The correspondence between weight ( the force exerted by gravity on a mass ) and inertial change ( F=MA ) was so amazing that it led Einstein to relativity. There is NO WAY to distinguish between weight and force due to acceleration. So Einstein concluded that they were indeed the same thing and that the fabric of space-time had to be re-thought, in such a way that space and time were warped by a mass to make this so. Gosh, this is even harder than Jabiru maintenance. The Einstein thing led to different math and things like the " aberrations" of the orbit of Mercury were explained and measured to be true. Wow, I wish I were smart enough to understand the math.
  8. Bruce Tuncks
    The laser horizon sounds like a good idea to me Jase... why did it not work?
  9. Bruce Tuncks
    Yep, I don't know the details of just what was different about the Bohli. But if you google up Bohli compasses and cloud flying and gliding competitions then you will get the story. I'm sure that they were not ideal, but keen and gung-ho glider pilots found them to be a loophole in the rules which they were happy to exploit. They would have been less use in Australia anyway, with our higher cloudbases. And you would need a southern hemisphere version to get things right. I have no idea if they even made a southern hemisphere version.
  10. Bruce Tuncks
    I don't like to disagree with you Nev, but the Bohli compass thing is a matter of historical fact. People really could use these things to climb inside clouds. Personally, I would prefer a gyro but these were banned even before the Bohli was used. The compass dip, properly compensated, gave a stable enough platform for the plate which was independent of inertia. The old turn and bank simple gyro could be used, but you would be hunting the airspeed. I remember having to remove this before the nationals. Personally, I never even saw a Bohli.
  11. Bruce Tuncks
    I googled that stuff up blue and liked what I saw. Is it easy to undo?
  12. Bruce Tuncks
    there was a time when Bholi compasses were banned from glider competitions. They were so stable ( the plate) that they could be used as an AH for illegal use of cloud lift. And yes, you can use a compass to fly a bearing in cloud, even though the speed will hunt as you have no horizon. But if the compass is not turning, the elevator will work properly but with a lag compared with using the horizon.
  13. Bruce Tuncks
    Those nuts n screws are designed to not come loose and so have a deformed thread to make them hard to move. In the fullness of time, with lots of undoing etc, they will become easier to operate and then they will become illegal on account of how they can vibrate loose. Your plane is just too new. I reckon those nuts are a stupid idea and you did the right thing fixing them with a file. If you are worried about them vibrating loose ( I don't think they would ) then you could use a drop of loctite on them. If you do this, make sure its the weak loctite or you will have even more trouble undoing them.
  14. Bruce Tuncks
    thanks OME
  15. Bruce Tuncks
    I hope he is good, but the job seems a bit like the prison camp capos of ww2. What can the incumbent do if CASA makes demands? Does the job allow the incumbent to disagree with anything CASA wants? The main threat to our existence as fliers is the cost. Look at how gliding has shrunk since it ceased to be the cheapest way to fly. What can the new guy do to lower costs? Owner maintenance and less red-tape and lower fees come to mind. But CASA has to approve everything I think.
  16. Bruce Tuncks

    Why I don't fly now

    Bruce Tuncks commented on Admin's blog entry in Ian's Blog

    Best wishes Ian. The medical profession, despite my criticizing them, is real good these days. Apart from that endorsement, I agree that you will always be welcome to the right hand seat of the many planes owned by us forumites, certainly my Jabiru for one. We are very grateful for all you have done with this site.
  17. Bruce Tuncks
    wow onetrack, is that for real? it looks like an april fool thing.
  18. Bruce Tuncks
    I agree Jim. It's brilliant. The problem (structural) with adding more wing to a jab is that the loads become too great at the required "g" forces. So if you arrange for the outboard wing section to hinge up, this can remove the the structural load when needed. I reckon we are seeing the first stirrings of a new way of building planes which will have glider-like performance... I reckon though that a whole new wing would be needed for the Jab. It would be much higher aspect ratio than the present one.
  19. Bruce Tuncks
    Good point rastus. We should all be aware that the glider or plane might have been mistreated. At least a walk-around before flying is what I do these days. Once, many years ago, I had flown our Janus in converting to my coming flapped glider. The next day I was at work and over the phone asked if I had done a hard landing, and the answer was that it was a real greaser, the sort you feel the weeds start the wheel spinning before it touches down. " well, said the guy on the phone, you flew it with a serious crack just before the fin... must have happened when the previous front-seat guy got out and the tail slammed down on the concrete runway".
  20. Bruce Tuncks
    While I agree with what has been said, I need to state that not all clouds are the same. There is no comparison between a rock-filled low cloud and a benign cu miles high over flat land. In Europe, there are many countries which allow cloud flying. One European who came here told us that on a good day, the cu were like inverted bowls and you could get the best climb of the day up inside the bowl, but then you had to fly through the cloud using the compass to maintain your heading while blind. Well he was faster than those of us who obeyed every regulation. That CASA vid "178 seconds to live " was accurate for the situation of low cloud over high ground. To transfer the lesson to benign cu at 12,000 ft over flat land is just silly, and it weakens the safety message to try to do this. There is a risk though that the benign cu can turn into cu-nim but this is a whole different set of circumstances.
  21. Bruce Tuncks
    Why not increase the allowable height except for the approach path crossings? My explanation is that CASA actually wants us lot to have more accidents. Imagine we went on strike and stopped having accidents. After a few years of this, I bet CASA's funding would be cut. And of course vice-versa... the more we crash, the more funding CASA gets.
  22. Bruce Tuncks
    Doe anybody know why RAAus ( and GFA too ) do not put the expiry date on their cards? I recently found out that the GFA card , which has a date on it, records the date at which you paid. Then I checked the RAAus card. It tells me the date at which I first joined ( for historical interest, this was 1999 according to the card ) but not the date at which the card expires. There must be a reason in favor of the organizations, but I can't figure it out. It sure buggers me up, my membership to GFA had actually expired and I didn't know.
  23. Bruce Tuncks
    I don't even know the risk. How much has been paid out in injury claims in recent years for RAAus members? Where is this information? Anybody who can do arithmetic will tell you that a one in a million chance of a one million payout is worth one dollar, but we all know that we have to pay overheads and profits on top of this. But hull insurance has already been priced too high for me.
  24. Bruce Tuncks
    And, let motorbikes also suffer the same test. With lower limits after hours.
  25. Bruce Tuncks
    I reckon the reason for airfield closures is not the noise, but the money people will pay for a housing block. If noise is a problem, let it be tackled directly, with decibel limits. Personally, I prefer the noise of a proper engine to the whine of rotax. Maybe some frequencies are more annoying than others , and this could be built into the db limits.
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