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The AN requires a mandatory inspection before next flight. This grounds all 19 reg aircraft, where ever they are, until the inspection can be carried out. A quick look at the RAA registration list suggests that is about 1500 aircraft grounded without warning. You might think that is no big deal - some might see that as a little extreme. Maybe that is not what the RAA intended, but that is how I read the "Action required: Mandatory inspection requirement before next flight"

The difference between should and must/shall is fairly well accepted. Should is a strong recommendation. Ignoring it may be unwise, but is not prohibited. Must/shall does not give an option. e.g. You must obey the speed limit. You should slow down when it is raining. In one case you can be charged if you ignore it. In the other you cannot, although it could be used as evidence to support other charges e.g. negligence.

The requirement for a duplicate inspection is not new or controversial. However, I'm not sure whether people are reading the notice carefully? It lists: "Duplicate Inspection" and "Mandatory Inspection" and "Action Required: Mandatory Inspection requirement before next flight" The mandatory inspection appears to ground all 19 reg aircraft immediately, until they are inspected. If the requirement was only for a duplicate inspection after maintenance, why would you single out 19 reg over other aircraft? And it appears that every inspection needs to be reported to the tech manager ("On completion of the inspection, and if any issues are identified..." is different to "On completion of the inspection if any issues are identified...") so it wouldn't surprise me if this will be checked, at least on registration renewal if not earlier. Could it even be a test to see which owners read and take notice of airworthiness notices? Most should be carried out and reported fairly quickly, if they are done. Alternatively it could be an error and they are not ready for a deluge of reports with one for every aircraft...

The earlier you start braking, the bigger difference it makes in your stopping distance. The problem in a taildragger is that you have a high AOA in a 3 point attitude, so by the time you get the tail down, let alone get enough weight on the wheels for significant braking you are too late to make a big difference to your stopping distance. I have seen suggestions to touch down almost at approach speed and brake immediately with the tail up for the shortest landings, eliminating the time spent in the flare, because at flying speed the tail is powerful enough to stop the nose over and the early braking has most effect on the total distance. This is obviously a potentially risky technique requiring a large amount of skill to reduce braking as the tail loses effectiveness. I suspect it was more appropriate to larger, faster taildraggers requiring long runways. I wouldn't try it myself. In the tailwheel aircraft we fly, we are better to accept that the brakes make minimal difference to landing distance. (Incidentally, I have noticed that wheel vs. 3 point landings give a good demonstration of how much drag the wing can produce. The aircraft slows noticeably faster without braking in a 3 point attitude than tail up.)

1) is all down to the programming - it can do whatever you like. As I understand it, primitive ABS just senses the rate of change in the rotation of the wheel. If it exceeds what is possible from normal braking (i.e. a locked wheel goes from rotating to stopped almost instantly), it releases the brake. However systems now could be much smarter, and take more parameters into account. However, the anti-groundloop stability suggestion obviously would be a problem if you felt the need to deliberately groundloop. 2) If you tied it into a system like a Dynon (or any similar system) you could have a pressure sensor to detect when the brakes were applied, and release them if the tail lifts (say) 10 degrees from the attitude where the brakes were first applied. This would stop a nose over even when tail up braking after landing. The more I think about it, the more I think a mechanical switch in the tail is the hard way to do it... we have the technology to make it a much smarter (and simpler and more easily tunable) system.

ABS is just sensors, a servo and a computer. With the right sensors and computer program it can do whatever you like (case in point: stability control where the computer can apply brakes individually). Actually there's a point, there's enough sensors and probably enough processing power in a Dynon to not only reduce the braking if the tail started rising, but it could even apply differential brake to stop a ground loop - with the right servos and the right programming (not necessarily as easy as it sounds). Possibly. I'm happy in my taildragger as is but I can see the value of something to address these issues from the insurance perspective. Although the insurance companies would probably say we already have a fix for that problem - the nosewheel :-). Interesting discussion though.

The question is whether it is better to nose over, or release the brakes and tear off across the airfield under high power? At least nosing over is a stationary accident. Sure, you should close the throttle, but how many people will do that before they hit something vs. just standing harder on the brakes? Nosing over is not common, so presumably having the brakes release would come as a surprise - and remember the common question before an accident, "Why is it doing that?" I could also imagine a situation where it makes it worse... the tailwheel lifts, the brakes release, you start moving forward and the tail comes back down, the brakes reapply, and now you have forward momentum + the rebound from the tail spring + braking all working towards a nose over. If you had something like ABS that modulated an essentially constant braking force it might be OK - but you can do essentially the same thing by matching the braking power to the airframe. Are there taildraggers that can use more braking power when landing than it takes to nose over during runup? Runups with flaps down I guess is one situation... As to how it might be implemented, the linked brakes on Honda motorcycles might provide some ideas. (Beware of patents, probably.) The torque from front calipers partially applies rear calipers and vice-versa. Maybe a secondary master cylinder in the tail operating a second set of brake pistons. It could be operated by pressure from the primary master cylinder, but opposed by a spring that was linked to the weight on the tail. So as weight comes off, the spring works against the pressure on the secondary master cylinder. As weight is applied, it removes the spring pressure that was preventing pressure on the secondary master cylinder...

The relationship between angle of bank and stall speed is drummed into us, and we are repeatedly told not to bank too steeply to maintain a margin. It would be interesting to know however, how many stall/spin accidents were caused by too much bank, and how many by too little bank. Keeping a shallow angle of bank, a bit of back pressure to avoid losing height and a bit of rudder because you feel like the turn is too slow is a bad combination.

If you are suggesting that an accident shows that the aircraft cannot land at or takeoff from the place in safety, I don't know whether it is that black and white. Is there a difference between "did not" and "can not" in the law? Does "did not" prove "can not"? If so, basically every takeoff or landing accident would appear to contravene CAR92.

This sounds a lot like it would fit the definition of price fixing, you are arranging between companies to control the price you pay for the services of your employees.

I think you missed my point. Certification is about safety, not about a level playing field. In an unintentional spin with 4 POB, are the occupants more or less likely to be killed in a Cirrus than in e.g. a PA28 or C172? Maybe you could look at it the other way - C172 etc. have to be able to recover from a spin (hopefully! but possibly dependent on CG, rigging & pilot skill) BECAUSE they don't have airframe parachutes? My understanding is that making an aircraft more spin resistant can make it more difficult to recover if you actually do get it to spin, so perhaps this is also a factor - if it is more difficult to induce a spin, does that make it safer? If you have to make it easier to spin in order to make recovery easier, does that make it safer? In the certification process there are cases where one safety feature can allow others to be waived. For example, multi engine aircraft don't have the same stall speed requirements as single engine aircraft, presumably because the likelihood of off airport landings is considered lower. Ultimately it is about the overall safety of the aircraft.

Would you care to name another 4 seat aircraft in which you would prefer to be a back seat passenger when Joe Average Pilot encounters his first spin, with 4 POB? While some other aircraft might recover from a spin without aggressive control inputs within the CG approved for spinning, it may be a totally different at further aft CG, where intentional spins are not approved.

126.7 is what is written in AIP. If confusion exists, I'm not sure whether those following AIP are the ones that are confused, or those that wrote the CAAP? Is the CAAP reducing confusion or creating it?

Absolutely. Again the rudder is being used to keep the tail directly behind the nose, except that in this case it is relative to the direction of travel over the ground instead of through the air. I don't really see the crab or sideslip as different crosswind methods - more a difference in how early you align the aircraft with the runway. Not even the most ardent proponent of the sideslip method would be slipping on a 5 mile final for a straight in approach - they will crab, then at some point align the aircraft with the runway. Once you align the aircraft with the runway you need to lower the wing to avid drift - unless you do it so late that drift doesn't develop before you touch down, which is only really applicable if there are reasons you can't lower a wing in the flare.

To deliberately spin an aircraft, you use rudder to yaw the aircraft at the point of (and after) stall. Aileron might aggravate the spin in some aircraft, but the primary control turning a stall into a spin is the rudder. To roll an aircraft using rudder you are yawing the aircraft so that one wing is at a greater angle of attack than the other due to dihedral etc. This increases the likelihood that one wing will stall before the other, causing a wing drop or spin. Using the rudder for roll, particularly close to the stall, makes it MORE likely that you will spin, not less. After the stall (with or without wing drop) you use the rudder to PREVENT or reduce yaw - not to pick up a wing with additional yaw. If a wing drops you may well be uncoordinated, but after the stall it isn't really relevant - the actions are: prevent yaw (e.g. caused by the wing drop) with rudder, unstall the wing by reducing angle of attack (elevator), then you can roll the aircraft level using aileron as normal. Adverse yaw isn't a reason not to use aileron. It is a natural consequence of increasing the lift on the down aileron - additional lift means additional drag. you counter that with rudder - that's what it is there for. The rudder is not intended to be a steering control in the air. It is there to keep the tail directly behind the nose with the varying forces from aileron adverse yaw, and slipstream changes with different power settings.

I don't think people with commercial ratings are superhuman, but we know that commercial operators are supposed to have standard operating procedures etc. as part of an AOC, and I would be astonished if they didn't have an accident rate much better than 3x less than RAAus. You are comparing comparing US GA in the '50s through early '70s to Australian ultralight data. You say they are directly comparable, but what evidence do you have? You should be able to produce some statistics to demonstrate they are more comparable than RAAus vs. GA today, for example. I personally don't buy it. I am not unfamiliar with a normal distribution. I would make a few couple of points: - It only make sense to fit values into a distribution if they are part of the same population. There is evidence in this case they are not, e.g. if you assume the HF accident rate, or the maintenance problem rate are the same, the results are implausible. This to me is evidence the populations are not the same. - 2 sigma, 3 sigma, 6 sigma - being outside these bounds is not impossible, it just means that a value is not likely to be part of the originally measured population i.e. there is something different about it. - I think you are confusing the standard deviation and the mean. I have not referred to the standard deviation, and I think this is the first time you have mentioned it. A value 6x the mean is not remarkable in itself. Asking for evidence is not a delinquent response. It is part of ensuring that we don't waste our time and energy in one area when the problem lies in another.

I'm not condemning RAAus pilots at all. My only point is that I believe your logic is damaged by too many assumptions. Your conclusions might be 100% correct, but you don't show the link. You calculated the result if RAA had the same human factors accident rate as GA, and got an implausible result. You calculated the result if RAA had the same hardware failure rate as GA, and got an implausible result. From this, you concluded that the result was somewhere in the middle, and picked the number 3. Why not 2? 4? 1.5 (i.e. 50% higher)? Isn't it possible that the data you are comparing are not directly comparable i.e. you are comparing apples with oranges? In fact, if you are comparing all GA I am fairly sure they are not directly comparable. Your conclusion flows directly from the number you assumed, but you show no evidence to support this number, other than it is likely to be somewhere between 1 an 14. I even have doubts about 14 being implausible. If the majority of GA hours are commercial, would it be that unlikely that GA charter has a 95% lower rate of pilot error accidents than RAAus? More information about the original data is required. I don't have an analysis of the data. My official position is "I don't know". But you don't need to be a photographer to know if a photo is out of focus. Likewise, being out of focus doesn't mean it's not a photo of what the photographer says it is. But if you can't tell, the photo is no use.

Which aircraft allow you to inspect everywhere? All aircraft have some areas that can't reasonably be inspected. But what I said was: "Some maintenance is obviously necessary. What I am suggesting is that if you design so less maintenance is required, safety and reliability are improved." Surely you would have to agree with this? Don't engines with thousands of hours TBO instead of hundreds increase reliability?

Your RAA hardware failure rate is based on the assumption that the RAA human factors accident rate is 3x that of GA. Where do you get that figure? You started with equivalent rates, which gave 96% of accidents caused by hardware failure. Then you seemed to conclude that 3x gave a reasonable figure. Where does 3x come from, if not from the result? If the GA figures include all commercial GA flying, under an AOC and overseen by company SOPs etc. I would be surprised if the RAA human factors accident rate was only 3x that of GA. Since the figure translates directly into the result, you can't just pick a figure and assume it.

I'm not arguing for eliminating maintenance. Some maintenance is obviously necessary. What I am suggesting is that if you design so less maintenance is required, safety and reliability are improved. Part of that is because whenever maintenance occurs, errors are possible. Most people who have been involved in aircraft maintenance could give examples of problems that occurred after maintenance - but to repeat, I am not arguing that that means the maintenance should not have occurred.

You're probably right, I just see problems with the stats you are using. Adjusting the assumptions until the results are within expected bounds isn't right. I would be more interested to see (and much more convinced by) stats that showed RAA accidents vs. GA private flying accidents, for the same years. Even then you would have doubt about the effect of RAA vs. PPL training, unless you had the figures for how many of the RAA pilots had a PPL and could adjust for that.

The problem with your stats is not with the RAA portion - if you want to compare total RAA fatal accidents, I would expect the RAA stats are adequate - all you need is hours vs. fatal accidents. However, if you want to compare it to GA you need to separate out the portion of GA that is equivalent to RAA flying, e.g. day VFR private flying. This is, I think, difficult. To address your points: 1) Airworthiness Design Standards reduce the accident rate; Initially I'm sure they did. Are aircraft still designed to the minimum required by design standards? Do more design standards reduce the accident rate more? How much is enough? Many would argue that airworthiness design standards currently prevent innovations that could themselves significantly reduce the accident rate, e.g. compare non certified synthetic vision features and prices vs certified. In most cases it is the requirement to produce safe and reliable products that drives design, rather than design standards e.g. I understand Lycoming engines far exceed the reliability required by design standards. 2) Most RAaus aeroplanes meet, at best, parts of an airworthiness design standard; 3) RAAus aeroplanes should, therefore, have a higher accident rate from hardware failure than GA aeroplanes; I'm not sure that necessarily follows - really, it is the question that we are trying to answer. 4) RAAus aeroplanes do have a higher accident rate due to hardware failure, than GA, although there is insufficient data to be precise about the figure; I wouldn't be surprised if this is true, but I don't know either way. I don't think the figures you present demonstrate that. 5) The Maintenance of Airworthiness, via Approved Maintenance Organisations, Licensed Aircraft Maintenance Engineers, and Approved Maintenance Data, prevents the vast majority of hardware failures in GA; I would expect that is true. I also suspect, paradoxically, that maintenance also causes many of the hardware failures i.e. they prevent wear related failures, but generate maintenance error failures. The relative rate of the different types of failures would be interesting to know. The best way to reduce failures is to reduce the amount of maintenance actually required. Design standards and inflexible maintenance schedules can work against this. RAA aircraft in theory are simpler and require less maintenance - which was the original basis of the current rules. 6) RAAus maintainers have very little training, very few aeronautical engineering qualifications, and extremely little Approved Maintenance Data; and there is no parallel substitute; so RAAus aeroplanes must undergo a higher rate of hardware failures per hour of operation, as they operate under the same laws of physics etc; Must? Why? If they are simpler or designed to require less maintenance, it is still possible to be more reliable. Do modern cars have more failures per hour of operation than GA aircraft, due to the lower qualifications required for car mechanics? 7) The RAAus accident rate is increasing from a minima, and the fleet mean age is growing. It is internationally accepted that the older the fleet (GA or otherwise), the more rigorous the demands on maintenance. True, although the overall effect depends on the baseline level. If you can demonstrate that, somehow, design, construction, and maintenance in accordance with Design Airworthiness Standards do not enhance safety, then there is no safety issue, and the world's airworthiness authorities can retire, saving quite a lot of money I suspect a lot of fat could be cut from the worlds airworthiness authorites without significantly affecting safety.

I'm not sure that any conclusion can be drawn from the stats as presented. When you apply a reasonable assumption (RA and GA human factors accidents happen at a similar rate) and come up with an unreasonable conclusion (96% of accidents are caused by aircraft failures) I think it points to a problem with the original figures. You then adjust the assumptions (rate of human factors accidents) to get a more reasonable answer for aircraft failure accidents. This doesn't seem right to me. Am I correct that you are comparing GA in the 1960s to RA in 2000+? To get any valid conclusions, I think more variables need to be understood. What types of flying are included in the GA figures? Are there significant differences in e.g. age and experience of the 2 pilot samples? It would be interesting to compare GA vs RA accident rates for GA private pilots only. Or pilots who flew less than 100 hours in the previous 12 months. That would give you are more comparable sample. And I think the comparison should be for a similar time period, not 40 years apart. It's tempting to say "Well, this is the best data we have, so we will see what conclusions we can draw from it" but sometimes the answer has to be "Not enough information".

It's the sort of change that looks quite reasonable until you try to work out the details. How do you find an instructor rated in type? Or are instructors assumed to have competence in all types? What about types where training is not allowed e.g. amateur built where you are not the original builder? What about single seat types? I don't understand why RAA writes rules that are more restrictive than GA. If you train in a 172, what training are you REQUIRED to have before you fly a 152, a Warrior, GA reg. Jabiru or Gazelle, Tripacer, Glastar, RV-9A, etc? Certainly training is advisable. It might not always be available. A wise pilot would get training in something as similar as possible, certainly. Are GA pilots wiser than RAA? If RAA pilots can't be trusted to make sensible decisions about training, maybe that needs to be addressed rather than making rules that are likely to be problematic.

Dr Zoos, that's the kind of long & complex explanation that gave me trouble when I was learning crosswinds. The problem with that explanation is it doesn't answer the question of how much rudder and aileron is required. How do you translate what the instructor is asking for into what you see through the windscreen? How do you translate what you see through the windscreen into the correct rudder & aileron to keep the instructor quiet? Crosswinds clicked for me when they were boiled down to a few simple principles: 1) Every landing is a crosswind landing. The wind is rarely straight down the runway, so use crosswind technique every landing, even if it is for only 2 knots crosswind. That way, you get lots of practice and it becomes automatic, rather than thinking OK, I've got a crosswind today, was it right rudder and left aileron or vice-versa? 2) Crosswind technique is: a) Point the nose down the runway, exactly the same as when you are taking off. Stop thinking left crosswind, right rudder, just point the nose down the runway. You do the same thing taking off and even just taxying around, so you actually get plenty of practice at this. b) Stop the drift with aileron as required. The problem with pre-planning left rudder and right aileron or whatever is that it depends on how much you put in initially. If you put in too much, all of a sudden you need the opposite. Or maybe you have too much aileron and not enough rudder, so need to apply left rudder and left aileron (i.e. less right aileron). Just look out the window, align the nose with the runway and stop left/right drift with aileron. This is something that is easy to understand, and easy to see the feedback visually rather than waiting for your patient/exasperated instructor to tell you whether you got it right. I also had a problem with the early wing down method. When you have one wing down, adding up elevator to break your descent has a temporary turning/sideways component to it, moving you sideways across the runway. So I found I was on centerline, wing down, then rounded out above the runway. All of a sudden I found myself drifting sideways off centerline. So I corrected the drift with aileron, which also requires rudder corrections. But breaking the descent was a temporary state, so as soon as you transition to the holdoff, you don't need the corrections and you drift the other way and have more rudder/aileron corrections in the opposite direction. This is the advantage of the crab method. If you put in the crosswind correction after breaking your descent, you are coordinated when you add the up elevator to stop the descent, so you don't add a temporary sideways force. My current method for crosswind landings (and every landing is a crosswind landing!) is: 1) Crab as required to maintain runway alignment on final 2) After stopping the descent i.e. between round out and hold off, align the nose with the runway and stop any drift with aileron I acknowledge this might not work for every aircraft. Extra inertia might make it more difficult with heavier aircraft. Some people find the wing down method works fine for them. A flatter approach will definitely reduce the sideways component when you round out with one wing down.