aro

The amount of fossil fuels being burned and the rate of change has increased markedly in the last 50 years. So it doesn't matter whether you pick a baseline of 50 years ago or 250 years ago, the change is very similar because most of it occurred in the last 50 years.

That's not how it works. 1.5 degrees is the average over the globe, not what is experienced in particular locations. Weather is driven by the heat and water vapor in the atmosphere. A warmer atmosphere has more energy and more water vapor, and weather in general is more intense. Storms are more powerful, winds are stronger, rainfall is more intense. Some places will be much hotter. Some places may even be colder at times because stronger winds are bringing colder air from the polar regions. But when that happens, the warm air goes to the polar regions which end up much hotter. The average is still higher. The big problem for humanity with climate change is not the absolute change in temperature. The big problem is that civilization relies on so much immovable infrastructure (cities, transport, water supplies etc) that has been built based on current weather patterns. If we were nomadic and could pick things up and move them when the weather becomes a problem, it would not be such an issue. We can't.

If you want to disagree with something, perhaps you can tell us what? Knowledge isn't worth much if you don't put it out there to test.

The shaded area is above 27" manifold pressure. Manifold pressure is reduced when you close the throttle. The reference to 3500 feet is because the air pressure reduces as you climb, so the manifold pressure possible at full throttle reduces. It is absolutely permitted to close the throttle and reduce RPM and cruise at a lower power setting because your manifold pressure is reduced by closing the throttle. The relationship between manifold pressure and rpm is set by the propeller. If you have a constant speed propeller, you have to manage manifold pressure to make sure you don't exceed allowable manifold pressure for the RPM. If the propeller is fixed pitch or ground adjustable, the pitch determines whether the engine is overloaded. If you are at less than 5200 rpm at wide open throttle you are lugging the engine (too high manifold pressure with too low rpm). In that situation Rotax recommend you close the throttle and reduce RPM by at least 100, because that shows that the manifold pressure has been reduced. It's not lugging at a lower rpm because with a fixed pitch propeller the load from the propeller reduces. They have provided a number of points on the chart: 5500 rpm 27"MP - max continuous power 5000 rpm 26"MP - 75% power 4800 rpm 26"MP - 65% power 4300 rpm 24"MP - 55% power Without a manifold pressure gauge we don't know the exact power setting, but it's pretty safe to assume if you get 5200+ at WOT at climb speed with a fixed pitch prop, manifold pressure will be OK in cruise. If you're only using 13-14 l/h at 5200+ you should be well below 75% power so well below 26" MP. 75% power fuel consumption is about 19l/h. 14 l/h should be around 60% power. With a variable pitch prop you would probably be better at around 4700-4800 rpm. However with a fixed pitch prop and a faster aircraft, 5200 minimum at WOT in climb means higher rpm at cruise speeds.

It doesn't show that at all. It has e.g. settings for 55% power cruising. What it shows is that 5200-5500 are the recommended/required rpm for full throttle at low altitude.

Can you provide a reference to the recommendations in the manual? I can't find anything. I have heard for many years that the 912 should be run at over 5000 rpm but I have never seen anything official from Rotax. It seems as likely as not to just be folklore. Exactly what problems are people anticipating running < 5000 rpm (assuming unleaded fuel)? Is there any real decrease in engine life?

You didn't use 55l/sec in your original calculation. You used 5.5l/sec. True, but it gives a reasonable point to start from. If you really want a more accurate answer you can start refining various figures but there's probably lots of factors unaccounted.

I think that is too low - should it be 55l/sec? ~40C doesn't sound unreasonable, that would presumably be measured as a drop in EGT.

Cars have a knock sensor that will retard timing if detonation is detected. If they have to retard timing from the optimum value due to low octane fuel, higher octane will give better economy. If they can run at the optimum timing on the lower octane fuel (i.e. engine design) they get no benefit from higher octane. Also, some of the 98 octane fuels claim to be "denser" i.e they need a leaner mixture. A car with an O2 sensor will adjust the mixture and use less fuel. If you have a mixture control in your aircraft, you might also use slightly less fuel. A carb without manual mixture control i.e. Rotax, Jabiru will use the same amount of fuel but run slightly rich.

Before V1 you need to be able to abort the takeoff and stop safely in the remaining runway. After rotation the task is fundamentally different, so V1 cannot be higher than Vr. If you don't plan to rotate at "Vr" it is not Vr. I was thinking about when V1 might apply in a single. There are problems where the correct thing to do is continue the takeoff so you could say V1 does apply. For example, if a door pops open in the takeoff roll. Early in the takeoff roll, if a door pops open, cut the power and come to a stop, no problem. If the door pops open as you rotate, cutting the power and trying to stop on the runway is a recipe for a broken aeroplane. Better to continue the takeoff, and do a normal circuit and landing. Or if the runway is really long, maybe you can stabilize the aircraft, reduce power and land straight ahead. But again that is different to an aborted takeoff before rotation. If the runway is short, e.g. you have a 500m runway and calculated a 400m takeoff distance, at some point before rotation you are committed - you probably can't stop in the remaining runway. At that point, if the door pops open you need to continue the takeoff. That is your V1 - even if no-one ever calculates it. There is no reason for V1 to exist except "what it is for". If the definition doesn't quite capture it there is a problem with the definition. "What it is for" and how it is used are the whole basis of V1. V1 is most critical when the runway length is limited. Yes. on longer runways V1 can be equal to Vr and you can abort the takeoff any time before rotation.

The point of V1 is that it is a pre-made decision about when you will continue the takeoff instead of stopping in the event of an emergency e.g. engine failure. It is there so you don't use up runway and options while you wonder should I stay or should I go? We don't use V1 in smaller aircraft For the case of an engine failure in a single, V1 doesn't exist. Jets etc. are required to be able to stop on the runway from V1, because running off the end of the runway after an engine failure is considered a bad thing. For smaller aircraft, people don't really care e.g. your takeoff charts for runway required do not include an allowance for stopping distance after a rejected takeoff. If it's a planned speed for rotation, aren't you using a lower Vr?

That's never supposed to happen. The theory is you detect the problem before V1. At V1, you should be able to reach Vr and fly away even if you lose an engine. This is factored into the aircraft design. If you need to be able to stop from Vr you potentially need a much longer runway or much more restrictive limits on weight.

If you don't rotate at Vr, it's not Vr?? V1 is only applicable to multi engine aircraft. It's the point after which you can't reject the takeoff, either because there is not enough runway to stop or you have already begun to rotate. Performance calculations ensure that at V1 you have enough power to continue the takeoff even if you lose an engine. If you don't, you have to adjust performance e.g. reduce the aircraft weight. The ability to continue the takeoff or stop on the runway after engine failure is only a requirement for larger aircraft. For smaller twins on shorter runways it may not be possible. I'm not sure where the cutoff is but it definitely applies to the jets operated by the airlines. (Not a multi engine pilot myself, happy to be corrected...)

Rejecting a takeoff after rotation would be considered a different kind of emergency... it gets significantly more difficult.

FAR part 103 is totally different to anything we have here. It is for single occupant, <254 pounds empty, <5 gal fuel capacity, 55 knots max speed and 24 knots stall speed. As I understand it, no license or training is required. It is probably closest to the pre-AUF ultralights in Australia. Not really what anyone is talking about.

Can you be specific? You quoted an EO to put a GoPro on a wing strut, whereas in the US it's a '337 Canada has 'owner-maintenance' for a range of basic GA certified aircraft right up to 172 variants Consider that you can go straight over the top of LAX, JFK or SFO in Class E in the US were you referring to any of those? Or anything specific in the post you quoted?

Which "things" have you searched for? I am not aware of changes in the US regulations, but Australian regulations seem to be going backwards e.g. maintenance on Experimental aircraft.

I'd prefer to leave the politics out. I think I'll give it a miss.

Is it a fly away or a political rally?

Rotax SI-912-016 has the answer: https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-912-016-r12.pdf

I doubt that semi synthetic motorcycle oil has any additives that fully synthetic oil didn't have that made it more suitable for leaded fuel. Or that any effort has been put into synthetic oils to make them more suitable for leaded fuel. The Shell website description of the Sport Plus 4 oil says it "blends high-quality hydrocarbon base stocks and incorporates synthetic technology" and "combines synthetic and high-quality mineral oil". So it is not fully synthetic. The bottle says "Synthetic Technology".

I don't know the chemistry, but I have seen many different sources saying that synthetic oil doesn't hold the lead in suspension the same way that mineral oil does. (One source says mineral oil molecules have more branches which mean they bind better to deposits.) Synthetic oil results in more lead sludge being deposited in the engine rather than removed when the oil is changed. Looking at old versions of Rotax SI-912-016 where they recommended motorcycle oils rather than only the Aeroshell oil, it specifically listed synthetic oil for use where only unleaded fuel is used. E.g. 1 Fully synthetic motorcycle oil with gear additives. Highly recommended for high oil temperature operation (higher than 120 C / 250 F) using only unleaded fuels ... 3 Semi synthetic motorcycle oil with gear additives. Highly recommended for normal (lower than 120 C / 250 F) and high oil temperature (higher than 120 C / 250 F) operation using leaded or unleaded fuels Fully synthetic oils were specifically listed for only unleaded fuels.

Rotax 912 oil is typically semi-synthetic. Fully synthetic is OK as long as you don't use avgas, but fully synthetic oil does not handle the lead as well as mineral oil. So if you use avgas, oil with some mineral content should be used.

Yes. The requirements for cloud clearance are to (in theory) allow you time for visual separation from IFR aircraft popping out from the cloud. So, (my understanding) special VFR means you don't have to comply with those requirements, but then ATC must separate you from IFR - i.e. by denying special VFR if there is conflict with IFR.

Rules for helicopters are significantly different, but I'm not sure what the point is?