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Bruce Tuncks

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Everything posted by Bruce Tuncks

  1. Bruce Tuncks
    Lots of correct stuff in this discussion, but OME introduces velocity when it is not required, and force= mass times acceleration not mass times velocity. Yes the venturi effect is needed to explain the inner workings of the carburetor, but not this question which as has been said is not clearly written. We need to distinguish between Absolute pressure and Gauge pressure. Gauge pressure is the difference between the internal and external pressures as applied to the gauge, and it is the only one we actually see in practice. Only if the external pressure is removed can a gauge read absolute pressure. There may be gauges with a built-in vacuum chamber and these would read absolute pressure. But our common gauges do not do this. Think of your car tyres. You pump them up to 30 psi gauge but the atmospheric pressure at the service station is 15 psi. Then you send the car to the moon where there is no atmosphere. The gauge will now show 45psi which has always been the absolute pressure in the tyre. In my Jabiru, at cruise at 2000 ft, the "vacuum " gauge shows -20kPa, while the atmospheric pressure is 100kPa. So the absolute pressure in the inlet manifold is 80kPa. If the "vacuum " increased to -30kPa then the absolute pressure would reduce to 70kPa.
  2. Bruce Tuncks
    The ASI will show a reduction in airspeed. The engine has lost a bit of power, and the constant speed prop has gone a little finer to keep the rpm's up. It wasn't a Jabiru engine in which you would not notice anything, not that Jabiru's have those fancy props.
  3. Bruce Tuncks
    Yep, that would sure bring it down.
  4. Bruce Tuncks
    I don't think the helicopter would crash if the cable broke. The helicopter is lifting as well as pulling. So there would be an acceleration upwards and backwards. If the pilot reacted properly then I reckon he would be ok. I agree it looks dangerous, but I don't think it really is. On one of the last days I used auto-tow launches for my glider, there were 3 broken cables in a row. I gave up and pushed over to the aerotow line. There never is a time on a cable glider launch where the glider is in danger, provided the pilot does the right thing. Once we had to contribute towards an appeal where the coroner ( who in my opinion was used to dog-men dying when their crane-cable broke ) decided that glider launch cables needed to be like crane cables. Luckily the GFA won that appeal.
  5. Bruce Tuncks
    Gosh those guys earn ridiculous amounts. They have a government backed monopoly as well as a closed shop as well as the ability to prevent new people entering the trade. How they got or deserve this largess is a mystery to me. If electricians had the same deal then they would all be millionaires too.
  6. Bruce Tuncks
    Why are motorcycles exempt from the vehicle-noise rules? I know that the appeal of a Harley lies partly in the noise, but this is so for muscle care too and they have to be muffled.
  7. Bruce Tuncks
    Sorry guys I have zero experience with injury claims. I would expect the insurance company to avoid paying out if they could. My hope is to retire before finding out the answer to this. In the meantime, I just hope the RAAus insurance will be ok. If you ever maim a young doctor while crashing into a kindergarten, you have my sympathy and I suggest you would be better off not surviving yourself.
  8. Bruce Tuncks
    As far as I know RF guy, they do not pay out if you have done anything against the regs. So if you are insured, you need to obey the regs to the letter.
  9. Bruce Tuncks
    I agree that if you are the club's insurance officer then you will insure the hulls. I know this from personal experience. It would take a braver person than me to say "no" to insurance. Who knows what some idiot of a club member might do? But the insurance companies are not stupid and although we sure made claims, we always paid more in premiums than we collected in claims. Look at it from the company's point of view: Premiums = income, and costs = payouts plus overheads plus profits. The payouts can't come anywhere near the income from premiums. I reckon the aviation world is small enough that news of poor treatment of a claimant would get around. This is a cynical way of saying that people I know who have made claims have been happy with the results. Personally, my last dealings with an insurance company were a pleasant surprise. I had a bike stolen from my local gym, and it was my fault because the bike had not been locked with a cable. The bike was not insured either, but they paid out under my household insurance. Sure, the amount was less than a year's premium, but here was I surprised to get anything. What would really interest me would be an insurance co-op where a bunch of similar guys pooled their risk and where you paid nothing if nobody crashed. Has this ever been tried?
  10. Bruce Tuncks
    Here's my rationale for not paying for hull insurance: Firstly, the plane is really just a toy and life would go on without it. Secondly, the cost of insurance is too much. In 20 accident-free years I would easily have paid for a replacement plane if I had only banked the premiums. Thirdly, a handy-person can fix a lot of stuff for only the price of the inputs and this is cheap compared to the commercial quotes that insurance uses. As a generalization, it is bad economics to pay insurance for a loss you can afford. If you have ordinary luck, you will only recoup a third of your premiums with claims. I hasten to say that I am referring to hull insurance, not third party injuries.
  11. Bruce Tuncks
    The whole idea of warfare is to avoid a " fair fight ". My ex-next door neighbor, a very kind and nice bloke who would never have voted for Hitler, finished the war as a German 18 year-old sheetmetal worker attached to a Luftwaffe base. One day they ( all 300 or so non-flying staff) were told to become infantry and fight off the Americans. Well the Americans came over the hill with 3,000 tanks. Were they cowardly? Not in my book. The disparity in fighting power meant that the Germans could surrender with dignity, which is what they did. But having said that, I have to say that I don't like the idea of using drones ( or killer robots ) to do the fighting.
  12. Bruce Tuncks
    Here's a heretical point of view... I reckon the fewer staff CASA has then the less harm they can do. I think that South Africa has a much smaller CASA than we have and they are better off there. If CASA had so few staff that their activities were confined to educating ( as opposed to policing ) then we would have more freedom and probably no less safety.
  13. Bruce Tuncks
    In case you are in danger of thinking there is any hope for the human race, I offer the fact that in our tiny blue starship planet, the main occupation is fighting the other passengers. The total spending of the planet on our militaries now surpasses other occupations. The superseded occupation was giving praise to imaginary super-beings.
  14. Bruce Tuncks
    And Binghi, the Moslems think like you do... "it is written" is a thing they often say. They say this about road accidents and so they don't wear seatbelts and they die a lot. When making an appointment there the correct thing is to add "inshallah" which means " god willing".
  15. Bruce Tuncks
    We are but victims of our inheritance, and the fact is that our tree-dwelling ancestors left us with an innate fear of heights. So do not expect people to be rational about flying.
  16. Bruce Tuncks
    I reckon the bear would have been white Jase, on account of how only at the north pole could you do that nav stuff. I had not seen that one before, but there was another one about the house where every window faced south...
  17. Bruce Tuncks
    At Gawler, years go I heard about a guy who took off from a taxyway which was between 2 rows of hangars. I thought it was funny but a wiser mate thought he should have been grounded. A few months later, he killed himself and a young passenger by hooning, but not at Gawler. This was a sobering lesson for me and I have come to the conclusion that he should have been in big trouble for that take-off. If he had, he may have thought twice about hooning with a passenger.
  18. Bruce Tuncks
    Ever seen those RC guys who "hover " their 3m size models with the rudder just missing the ground? They have the C of G way back, like 100% of chord, to do this. They sure are unstable like this... the rudder and elevator are moving fast and with big movements.
  19. Bruce Tuncks
    I've wondered about that too... Maybe owners of pit bulls have small ones too and they feel the need for an equalizer?
  20. Bruce Tuncks
    On the way to Port Augusta.jpg
  21. Bruce Tuncks
    Jab plenum... I just saw the latest kitplanes email and they featured a carbon "tunable" plenum. There is some sort of adjustment thing in the very middle of a x shaped plenum with 4 exit pipes. This got me to realize that the standard Jab plenum could be much improved by making the exits radial. If you could do this, then every cylinder would get the same fuel/air by symmetry.
  22. Bruce Tuncks
    Injectors have been used on Jabirus. There is one of these at Tailem Bend and the owner is happy with it. But Rod Stiff has pointed out that this makes the engine dependent on an electric system and so opens up another possibility of failure.
  23. Bruce Tuncks
    After more than 15 years I finally installed EGT and CHT on each cylinder and finally got the temps fairly equal. I tried lots of things, and the big break came when I was told on this forum that nothing much upstream of the carby would be very effective. The story and some pics are on here.
  24. Bruce Tuncks

    Why I don't fly now

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

    Sorry to hear of your eye problems Ian. But danny is right, you will be able to fly in 2 seaters with another pilot. You sure are welcome to fly like this in my Jabiru if you ever make it to Gawler or Edenhope.
  25. Bruce Tuncks
    Just try different speeds etc at a safe altitude. I find that in my Jabiru SK, I lose about 200 ft doing a teardrop, starting at 80 knots and a simulated engine failure. You minimize the height loss by turning slow( 60 knots) and steep ( 45 degrees). You need to start the turn quickly so the first bit is climbing as you slow from 80 knots to 60 knots . When I told an instructor this, he said it was more like 500 ft and he proceeded to show me with a spiral dive where I was scared he would rip the wings off. He got it into the yellow zone on the ASI. In a glider, starting at 60 knots, you can do a CLIMBING teardrop finishing at 45 knots. BUT I hasten to add that if you are slow and dopey starting the turn, you will lose your speed before you start. Further, if you are in panic mode because of the sudden quiet, you will likely stuff things up. So the advice to " choose the least worst straight ahead" is not so silly. ( straight ahead really means no more than a 15 degree turn).
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