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aro

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Everything posted by aro

  1. aro
    There are a lot of square inches of wing. The pressure difference required works out to around 0.1 psi for a typical light aircraft.
  2. aro
    Would you be able to turn to starboard if the rudder was attached to the extreme port side of the boat? Of course, you would, so it’s not drag doing the job.
  3. aro
    No, it's fundamentally wrong. I don't even know which side you are suggesting the lift comes from. Dividing people into Bernoulli and Newton camps is completely misunderstanding what Bernoulli and Newton are about. They are both correct* - they are just different ways of looking at the same thing. It depends on whether you choose to view air as a fluid or a stream of molecules. * Some people - usually those who divide people into Bernoulli and Newton camps - use Bernoulli's principle incorrectly. But that doesn't mean Bernoulli was incorrect.
  4. aro
    "Lift on one side" is an inaccurate picture. Lift is the result of a difference in pressure between one side and the other.
  5. aro
    I don't understand the question. Of course they produce lift. Drag is an unavoidable byproduct of lift, but the drag does not produce a force in a useful direction (with the exception of odd configurations, like aircraft with the rudder on the wingtips).
  6. aro
    27 knot stall sounds a bit too good to be true. Indicated airspeed maybe, but I am skeptical that is the real stall speed.
  7. aro
    Where does that put the centre of gravity? That is even more important than the overall weight. Your "confirmation person" doesn't sound like someone who gives good advice.
  8. aro
    You can fill in a form for a RPL, do a flight review in a GA aircraft (which could be something like a Jabiru also registerable as RAA, and which also counts as your RAA flight review) and you're legal to fly a C172 (subject to competency requirements etc.) How much less bull do you want?
  9. aro
    No. The manifold pressure gauge measures approximately how much air is available in the manifold for the engine. It is a measurement relative to zero i.e. a vacuum. It is an indication of how much air will be drawn into the cylinder in an intake stroke, but it doesn't measure how much is being used. If the engine is not running: - at sea level, the gauge measures about 30 inHg - parked at an airport at 5000', it will read about 25 inHg. - launch your Cessna into space and the manifold pressure gauge will read zero. With the engine running, the gauge will read somewhere in between. The pistons are sucking the air out of the manifold, and the throttle limits how fast it can be replaced. The manifold pressure gauge can't tell the difference between low manifold pressure due to flow into the manifold being restricted by the throttle, and low pressure at wide open throttle because you are at altitude. Nor can the engine.
  10. aro
    Manifold pressure is measuring the pressure in the inlet manifold, after the carb/venturi, throttle etc. it is measured relative to zero i.e. a vacuum. It is lower than ambient when the engine is running because the pistons are drawing air out of the inlet manifold.
  11. aro
    Colder air at standard temperature?
  12. aro
    Yes, the master needs to disconnect the battery because that is the most likely source of enough current to start a fire. The contactor should be as close as possible to the battery. My understanding is that the Rotax uses a permanent magnet alternator. There is an option for an external alternator, but I don't think I have ever seen one.
  13. aro
    Just to clarify, which quadrants are IFR only? Too bad if you want to travel in that direction VFR!
  14. aro
    I'm not sure what you consider a real war, but the USA has seem many more deaths from COVID-19 than from the whole Vietnam war. In April they had more deaths in a single day than from the entire war in Afghanistan, on multiple days. They are likely to exceed the number of deaths from World War 2 within 2-3 months. The Spanish flu pandemic is estimated to have killed more people than World War 1. So far we have been relatively untouched in Australia but if you talk to people in New York, when people you know start dying things suddenly get real.
  15. aro
    It is true that treatments have improved and we know more about what works and what doesn't. But the death rate is still very high. While some elderly people die quickly, for many people it is 3 weeks or more after infection. When numbers are increasing, comparing infections to deaths gives a misleadingly low death rate. Deaths lag infection numbers by 2-3 weeks. We are going to see some bad numbers appearing in Australia over the next week or 2 and continuing for a month or more, depending on the effectiveness of lockdowns.
  16. aro
    That's how sore throats and sniffles spread, and it's also how COVID spreads. By the time you have symptoms you are likely at your most contagious. The advice is if you have ANY of: fever chills cough sore throat shortness of breath runny nose loss of sense of smell or taste Don't go to work, don't go out other than to get tested, and stay home until you get the result. People waiting to see whether it turns into something more are why we are ending up with 40+ cases in some workplaces. If you are as sick of this pandemic as I am, please do the right thing and make sure you are not contributing to further spread.
  17. aro
    There are some suggestions that it wasn't a balloon, it was a failed BRS parachute from the aircraft. We need more information I think.
  18. aro
    Make sure that your mask does not have holes or a valve. This can result in breathing out the virus if you have coronavirus (COVID-19). https://www.dhhs.vic.gov.au/face-masks-victoria-covid-19
  19. aro
    The number of bowel cancer cases doesn't double every few days. Infectious diseases are different. The USA is back to 1000 COVID deaths per day, from infection trends it looks likely to increase to 2000 deaths per day. These numbers might be under counted by 30-50% based on the number of deaths compared to a typical year. Several vaccines have reported good trial results in the last week or 2. But the more people who catch the disease before a vaccine is rolled out, the longer it will be to get back to normal when a vaccine is available.
  20. aro
    They do specifically say make sure your mask does not have a valve.
  21. aro
    The majority of the benefit of the mask is to others - if you are infected it keeps your virus out of the air and off surfaces. There is also some protection to the wearer, but it is less than the protection you get from infected people (who may not know they are infected) wearing masks. There is most benefit when everyone is wearing a mask - to get infected particles containing the virus need to pass through 2 masks.
  22. aro
    Glad it was quiet for you, it certainly wasn’t when I was out!
  23. aro
    What does the chart look like over a longer timeframe e.g. 1 year? It looks more like there was a peak around March-April then back to normal (or even a bit above) rather than a decline.
  24. aro
    There has never been a particular need for one in humans until now, so no money to develop one. My understanding is that vaccines are used against coronaviruses in other animals (much cheaper to develop and test I imagine). Immunologists are predicting that multiple different vaccines will be successful out of the 100+ under development. In the last few days I think 2 different vaccines have reported success in phase 1 trials - no safety concerns identified, and antibodies produced against the virus.
  25. aro
    Can you multiply by 10? Case numbers were going up by a factor of 10 about every 2 1/2 weeks. Starting at 3 cases/day, 2.5 weeks later 30 cases/day, 2.5 weeks later around 300 cases/day. Another 2.5 weeks and it's 3,000 cases/day, 2.5 weeks after that it's 30,000 cases/day. 5 weeks without action and we would be in deep trouble. We can't cope with 30,000 new cases every day. That's the same way the disease progresses everywhere, unless you lock down to stop the spread. To deny that would happen here you need to find some reason we are special, and the maths that apply to the rest of the world don't apply to us. (Hint: we're not.) More good news: https://www.newsweek.com/scans-reveal-heart-damage-over-half-covid-19-patients-study-1517293
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