aro

I agree - the sample for the PA28 looks the same. Partly because of the shape of the envelope. The forward limit reduces with increasing weight, and the CG moves forward as fuel is used. The forward limit moves forward faster than the actual CG as fuel weight decreases.

We know you were referring to weight. But I haven't encountered small aircraft where the maximum landing weight is less than the maximum takeoff weight. Did you have specific examples in mind? The C210 example is referring to CG. I could not find anything about maximum landing weight.

It is fairly common. C210 obviously based on this example. It's well known for Bonanzas. Probably most aircraft where the CG can approach the limits. I'm curious, I will have to work a sample for a C172 and PA28 and see whether you can load it so it goes out of balance as you use fuel.

Turboplanner wrote: Facthunter and I replied: Turboplanner replied: Turboplanner's original post was referring to weight, i.e. you may have to burn fuel before landing. But the C210 POH is referring to CG.

The Cessna 210 POH is referring to calculating the CG. Maintaining CG within limits as fuel is used is important for every aircraft, not just cross country. It is not a maximum landing weight and doesn't require you to use up fuel before landing.

C152 and Jabiru are both 2 seaters where you may not be able to carry 2 people and full tanks. It's often said any aircraft where you can fill the seats and the fuel tanks should have bigger fuel tanks. What is the smallest aircraft where maximum landing weight is less than maximum takeoff weight?

"Whatever it takes" isn't much help if you don't know what it takes. What it takes is Vy. That's why the number is in the book. Vx, Vy, best glide - they are documented for a reason.

We're not talking about standard everyday practice. We're talking about what you do when...

Sure - in normal operations a higher speed "cruise climb" is fine. But if you're not climbing, Vy is the speed you need. Speed above Vy is not your friend (unless you are overloaded, when a few knots might be helpful due to induced drag equations). Vy might be the difference between climbing away and crashing. ATEC list 110 km/h i.e 60 knots as "optimum" speed which I assume is Vy. About what I would expect. If you NEED the performance, you NEED to fly the speeds.

True... both are likely to be lower than 90 for common RA aircraft. 90 kts would be for higher performance aircraft e.g. Cirrus, Bonanza are probably somewhere around there. For our aircraft (<45kt stall speed) somewhere around 65-70 seems more likely.

I don't recall doing much performance or weight and balance in my RAA training. It was covered fairly thoroughly in PPL. One of the problems in RAA might be that the results of the weight calculations might be embarrassing, at least for the older lighter aircraft (and even 2 seat GA aircraft like the C150/C152). I suspect there has been a lot of training performed overweight over the years. In GA you probably start learning weight and balance when you start doing navs, when you probably also switch to 4 seat aircraft where the weight isn't a problem. 90 knots seems like an unlikely number for best rate of climb??

Interestingly, the checklists taught to students seem to bear little resemblance to the actual checklist for the aircraft. This is the C172 pre landing checklist from the POH: - Seat backs - most upright position - Seats and seatbelts secured and locked - Fuel selector - BOTH - Mixture - rich - Landing/taxi lights on - Autopilot - OFF The PA28 pre landing checklist: - Fuel - fullest tank - Seat backs - erect - Seatbelts - fastened - Fuel pump - ON - Mixture - set - Flaps - set There are differences there that could be the subject of debate (C172 has flaps in the descent checklist) but there are definitely items there that are typically left off the commonly used checklists.

I think it's the same problem - the what's new page is very large, and the ipad scales it to fit so the text ends up very small.

The site is suddenly very small when viewed on an ipad

CASA don't do any assessment for the basic class 2. Basic class 2 boils down to a yes/no question to be answered by your GP: do you meet the standard for an unconditional commercial driver license. By applying a condition, your GP has said no and the basic class 2 is not available. CASA will do their own assessment if you want them to - it is the normal class 2. The standard for a regular class 2 is less strict than a basic class 2, but you may need to provide more supporting information. The basic class 2 a cheaper path for uncomplicated cases, not a lower standard.

Every engine needs an efficient intake and exhaust system to deliver rated power. The difference between Rotax and other makes is 1) Rotax state it explicitly and 2) They supply an optional airbox. Is the intake system on your average Lycoming as efficient as the one use to measure rated power? Who knows - but odds are it isn't. So your average Lycoming probably isn't delivering rated power either.

I found comparisons for Rotax vs O200 installed in a Kitfox. The consensus seemed to be that the Rotax was about 20kg lighter installed. I also found pictures of Cessna 150s with a STC for a Rotax engine. The Rotax was quoted as 18kg lighter, but the aircraft was fugly with the extended nose to maintain CG. You can save a lot of weight running a smaller engine at higher rpm for the same power. But from the Rotax 912 to Jabiru to the PT6, new engine designs have only really been successful when they have been paired with new aircraft designs. For an existing design, it's much easier to live with the limitations of the existing engine.

When they were designed, but they are old designs now. It's instructive to see what happens when people suggest replacing the smaller engines with similar power Rotax engines. It turns out that the Rotax engines are lighter, which means a longer nose to get the correct CG, which means new spin and stability tests etc. Basically it is possible to build smaller, lighter engines with newer technology but you need to design a new airframe around them (which is exactly what we have seen with the Rotax engines). Pretty much all of them. It's interesting to read about the durability testing they do on new auto engines. They need to know if there is anything that will break, before they build a million of them. Typical seems to be: 300 hours continuously at max RPM, wide open throttle 10-20 hours at 10% over redline, WOT 400 hours varying between peak torque and peak power in 5 minute cycles, WOT 2000 hours idling to verify oil delivery at idle speed Thermal cycle testing, where they chill the engine with coolant at -15C. When the engine is at -15, start it and run at peak torque, WOT until it reaches redline temperature. Then stop it, drain the hot coolant and run coolant through it at -15 until the engine is back to that temperature. Repeat 1000 times. Every time you find way to fail an engine in development and fix it rather than have it fail in the hands of a customer is a win.

The problem with auto conversions is all the other bits that you have to add and the things that are different to a car installation. Auto manufacturers probably spend tens of millions validating the cooling system, gearbox etc. An auto conversion needs: - a PSRU - a custom cooling system - maybe e.g. the sump needs to be modified to be sure of oil supply in different attitudes. Particularly if the engine is installed backwards relative to a car installation - climb power becomes the equivalent of full power *down* a steep hill - not something that cars commonly do The type of people who do auto conversions also like to make their own tweaks, maybe to increase power e.g. based on race tuning or increase perceived reliability. None of these changes get the type of testing that the car installation gets. It's not the engine that is the problem - it's the changes you need to make to put it in an aircraft, and the cost to do that development properly. Car manufacturers can afford to spend the cost - aircraft manufacturers can't. You just can't recoup the costs with the size of the market.

That's my point, aircraft engines don't have nearly the same development resources available. And given the scale of production, car manufacturers can't afford to have anything like the failure rate that we see in aircraft engines. There are still problems - but massively fewer than in aircraft engines. Compare the hp/capacity for an aircraft engine vs. car engine. 100% power in e.g. a Lycoming is relatively low for its capacity. Car engines in development are tested at 100% power for hundreds of hours continuously. It's just a myth that they can't do that. Problems in auto engine conversions for aircraft are most likely due to the parts that are different or don't exist in a car e.g. cooling, PSRU. Auto manufacturers also spend millions validating the cooling system - no-one can match that in an auto conversion. There have been huge advances in engine reliability in the last few decades, but aircraft engines have hardly changed. That is because of the cost of development, not because they are more advanced than auto engines.

I don't know whether per km is the best way to measure reliability, particularly since car reliability probably improves e.g. with more highway km at 100km/h. Would you say the same engine is more reliable in a fast aircraft than a slow one? Even so, 1 in 10,000 hours is probably more like 1 in 5 aircraft experiencing a failure before 2000 hour TBO, rather than 10,000 hours on 1 engine. So using your calculation it's probably equivalent to 1 in 5 engines failing before 200,000km, which I think *would* be bad enough to seriously embarrass a car manufacturer. Any failures are also more likely to be maintenance related, e.g. not changing oil, coolant, hoses etc. in a 10+ year old engine rather than the engine itself. I am really referring to car engines from the last 10-20 years - not older engines e.g. from the 70s and 80s which were definitely less reliable.

Look at the number of cars vs. the number of aircraft. The reality is that if car engines were as unreliable as piston aero engines, there would be cars broken down everywhere by the side of the road. The CASA Jabiru engine failure study quoted a failure rate for Continental and Lycoming i.e. the "good" engines at 1 per 10,000 hours. Car manufacturers can't afford anywhere near the level of unreliability that aircraft engines get away with. The publicity would kill the manufacturer. Car manufacturers need reliability. If there's a way to cause a failure they need to know about it. They put their engines through tests that an aircraft engine would be unlikely to survive. Aircraft engine manufacturers just can't afford the R&D costs that go into a modern car engine. They don't have the numbers.

Ha, I wish! That works as long as you don't need to set an alarm, schedule a meeting, calculate someone's age, calculate interest, display the time... basically most practical uses of time.

I doubt it was an issue for this particular flight because it has more effect on slower aircraft, but: Do not trust fuel calculations from the EFB apps unless you understand exactly how they select the winds for the calculation. I know one of the commonly used apps in Australia makes a poor wind selection for fuel calculations. It only occurs in specific weather patterns, but you can fly from A to B back to A and it will give you a tailwind in both directions. I have finished a flight with significantly less fuel than expected, and it was due to this tail wind both directions scenario.

If your aircraft has a MTOW of 1000 kg and max load factor of 4g it means the the wings can produce 4000kg of lift. If you stall at 100 knots at 1000kg and 4g, it means that at that speed you can't overstress the wings. However, at 800kg, 100 knots still gives you up to 4000kg of lift, but that is 4000/800 = 5g. The wing still sees 4000kg and is OK, but other parts of the aircraft see the higher loads e.g. seats, baggage compartment floor load limits are based on the same 4g limit and might be damaged. The G load applies to the whole aircraft, not just the wings.