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About MEH

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  1. And the Private, Commercial, or ATP pilots exercising privileges of a Sport Pilot (flying with a driver's license medical) must also maintain visual reference.
  2. Correct. "Light Sport" and "Sport Pilot" are two different things. "Light Sport" is what the CT series is defined as. The original question was basically: "Can I fly above a layer" and "Is the AWOS report inviolable?" The pilot certificate holder level was not defined. As this is a CT and hence "Light Sport" forum, and as of 2019 there were 6,467 active Sport Pilot certificate holders in the USA and more than 161,000 active Private Pilot certificate holders (Wikipedia), and the original certification level of the query was not specified, the assumption is that the original question proposed was by a Private Pilot Certificate holder, not a Sport Pilot certificate holder, and the question was referring to the CT design, not the training level. As such, the answer is: "Yep. Fly over a cloud layer all you want to with your CT. It is VFR, even if you can't see the ground." (Assuming VFR cloud clearance and visibility minimums). Certainly those Sport Pilot minority among us (who had the requisite 20 hours of flight training) would have remembered those limitations drilled into them by the FAA flight examiner on the day of their examination, and it is the Light Sport designation of the Flight Design aircraft type that is the origin of the ambivalence, not the Sport Pilot certificate limitations. However, if the assumptions are incorrect, then apologies are in order, and are given. MEH
  3. Light Sport rules demand all operations are performed in VFR. VFR over the top of a solid layer is still VFR. "Over the top" is perfectly legal VFR for all. Here is an AOPA article which discusses that: https://www.aopa.org/news-and-media/all-news/2001/july/flight-training-magazine/over-the-top Regarding what the AWOS says vs reality: It is up to the PIC to decide the go/no-go; but the caveat is, if there is an incident, the NTSB report (and the lawyers and the FAA) will refer to the nearest AWOS record, and the report will say... "continued flight despite reported IMC (or marginal) conditions..." I have, on occasion, taken a photo on my phone out the windscreen during a flight where the AWOS has reported IMC but the actual conditions are VFR, just to document what the actual conditions are like, should the feds get involved. A picture is worth 1000 words. My "get out of jail free" card.
  4. That is an impressive amount of work, both collecting the data and the analysis. Thanks!
  5. Looks like some fuel staining around the filler ring. You might consider doing the dremel and epoxy repair to mitigate that.
  6. The F2 on the cover of Flying Magazine. What is that wrinkle?
  7. My apologies. The waterless Evans (in the blue jug) approved by Rotax, is not to be confused with the 50/50 BMW blue stuff approved by FD.
  8. Be careful if you are intending to add anything to "Blue" coolant! You should read the Rotax Fluids Service Instruction that was just revised (attachedRotax fluids service instruction.pdf). According to Rotax, the blue stuff should be "Waterless Coolant" aka Evans in the USA and Aero Cool 180 in Europe. You should never add water or water based coolants (green or orange) to the waterless blue stuff. See the Rotax Service Instruction.
  9. MEH

    Piston Head

    The frequency of exhaust valve failures in Rotax? Very low. Probably on the order of frequency that the engine starts making metal, but we cut the oil filters open at every oil change looking for that remote possibility. As to why you would want know that your exhaust valve is in the process of failing earlier than detectable by compression testing? Same reason people want to catch their polyp when it is small. We have no idea how long it will be until there are regrets. Presumably every in flight exhaust valve valve failure had a compression test at the last annual. As to why the industry standard hasn't uniformly adopted the borescope inspection? Same logic as has been highlighted. We have been doing only compression testing for the last 75 years, why should we change now?
  10. MEH

    Piston Head

    The consensus thinking on exhaust valve failure is that there is imperfect seating of the valve and escape of burning gasses around the valve during combustion causing a hot spot on the edge of the valve at the point of the microscopic leak. It takes some time for the hot spot to result in a crack and failure. The failure of the compression test is one way to detect the failing exhaust valve, but it only detects the valve that has a big enough leak at the moment of the test and the test is done at 80 psi. The peak pressure in Rotax 914 cylinders during combustion at 4000 rpm is about 435 psi and at 5800 rpm is over 700 psi. (https://www.researchgate.net/figure/Comparison-of-measured-and-calculated-cylinder-pressure-at-5800rpm-4000rpm-Rotax-914_fig3_280656658). It is the hope of the borescope to catch the failing valve earlier by detecting the developing heat damage before the leak gets big enough to detect by differential compression testing. The inspection takes about 2 minutes per cylinder once you are practiced in manipulating the scope. For those who would like to spend $200 on a borescope and a little time to go the extra mile and learn how to borescope their cylinders/exhaust valves, AOPA has an article with a poster included that gives pictorial examples of normal and sick exhaust valves. Check it out: https://www.aopa.org/news-and-media/all-news/2014/june/pilot/pe_ownership As there are vastly more Continental and Lycoming engines in service than Rotax engines, it is my contention that those who are producing publications on the topic are basing their recommendations and observations based on the legacy engines simply as a matter of volume in the fleet. Rotax engines have exhaust valves and in 8 minutes you have gone the extra mile. Sit on the couch, or an 8 minute mile. Your choice.
  11. MEH

    Piston Head

    My "summary" is not "quite misleading". The facts of the ATSB publication stand as stated. The point made by quoting their published data was to refute the notion that "Rotax is not prone to the same issues as other aircraft engines", as if Rotax was somehow immune to engine failure. If your engine fails and you did everything possible and reasonable to ensure that the engine was safe ahead of time, you will sleep well. I would hate for anyone to wonder on Monday morning if they should have played the game differently on Sunday.
  12. MEH

    Piston Head

    According to data published by the Australian Transportation Safety Bureau (the equivalent to the NTSB), Rotax powered light aircraft were the second most common type of engine to have an engine failure or malfunction over the 2009-2014 period they looked at (link below). Worse than Lycoming and Continental. Jabiru was the worst. Would borescope have helped? Who knows. But the publications I read say it is prudent to borescope, easy to do, and may just save your bacon one day. https://www.atsb.gov.au/publications/2013/ar-2013-107_research/
  13. MEH

    Piston Head

    This article from AOPA is a good start in convincing everyone to start borescoping. https://www.aopa.org/news-and-media/all-news/2017/may/pilot/savvy-maintenance-borescope
  14. MEH

    Piston Head

    I have seen 1/8" of irregular buildup on pistons after 2000 of 100LL. Chunks of junk broken off. Looks like the moon surface. Really, it is the valves you want to focus on. Especially the exhaust valve. Look for asymmetry in the face (a hot spot). A little bit of a bulls eye--good. The rising sun--bad. https://www.aopa.org/news-and-media/all-news/2016/november/04/aircraft-maintenance-tackling-top-overhauls-borescope-tests The exhaust valve is the most crucial component to inspect. Exhaust valves are the weakest link in most cylinders because they are subject to extreme heat as the combustion gasses flow out of the cylinder, and they can only dissipate this heat through the valve guide and valve seat. In addition, they tend to collect deposits of lead and other byproducts of the combustion process on the valve surfaces as the gasses flow by. This can cause a poor seal between the valve and the valve seat. Once a breach begins in the sealing surface of the valve and seat, the hot gasses passing through it will quickly erode the valve and begin the failure process. One indication is to look for uniformity of the coloration on the face of the valve. If the valve is seating properly, the face will typically look uniform with no color variations at a particular "clock position" on the face. Don’t worry too much about the "burnt pizza" look on the face of the valve—it’s the uniformity that matters.
  15. Engines do quit. Before AND after TBO. If the engine were to quit, the FAA will investigate. The guidance they give their Aviation Safety Inspector regarding beyond TBO ops on certificated aircraft is here: https://fsims.faa.gov/wdocs/8900.1/v03 tech admin/chapter 64/03_064_002.htm Thank you, Roger, for linking the FAA opinions regarding the official position on S-LSA "mandatory" TBO. The bottom line is that beyond TBO ops are allowed, BUT it will go well with you, should you have an incident, if you can show that you are going the "extra mile" to make sure your beyond TBO engine was healthy. Namely, record your cylinder borescope findings in your annual logbook entry. Submit oil for analysis at every change and keep a folder of the results. Record oil consumption, if only in your own records (the oil analysis provider I use records the oil analysis I tell them on their report). By showing that you are going the "extra mile" you are not only doing everything you can to assure the engine health but you are demonstrating to those who care, that you made the effort. Stuff happens anyway. PS: For all of you who are not performing a borescope cylinder inspection, please read Mike Busch's book "Manifesto: A Revolutionary Approach to General Aviation Maintenance".
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