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That's not a benchmark on failure rate, its a way of estimating failure rate from accident data. It is saying the numbers for engine power loss and shutdown are unreliable, and provides a way to estimate them from accident data - which is considered more reliable. According to that document, historically engine power loss/shutdown frequency is greater than 1 in 10,000 flight hours (doesn't specify how much greater). Their estimate of power loss/shutdown frequency is Number of accidents x 10 or Number of fatal accidents x 100. So it doesn't provide any actual benchmark. However, it does provide a way to estimate the number of engine failures across each engine type: the number of accidents x 10. The number of fatal accidents is probably too low use reliably. However there have been a number of fatal engine failure accidents behind Lycomings and Rotax, so using this methodology would suggest that those engines have a failure rate much higher than Jabiru.

That's my point - without knowing the variation you can't conclude anything. The number on it's own is meaningless.

The number seems unlikely to have doubled in 1 year. If there is a trend over several years you would look at it, but you can't conclude anything from those 2 figures. That's when statistics come in - you plug in the numbers over several years, and statistics can tell you how likely it is that this number is produced by chance. If it is unlikely to be produced by chance, then you need to start looking for causes.

What FAA benchmark were they referring to? Assuming there is such a benchmark, there are still 2 problems: 1) What if other engines e.g. 2 stroke Rotax, VW conversion etc. also don't meet the FAA benchmark? 2) How long does it take to demonstrate that you do meet the benchmark? This is what I was saying might take 5-10 years of figures to produce valid statistics. When numbers are low, you get a natural variation in figures. Just the other day on the news they were saying that this year 14 people have drowned on beaches this year when the equivalent figure last year was 7. Have the people responsible for beach safety made some big change that is causing people to drown, or more likely, is it just a particularly unlucky year?

And that may be very difficult without good data on what triggered the restrictions. CASA have painted themselves into a corner where lifting the restrictions might be very difficult. They have to either: - Come up with some metric for Jabiru to reach to justify lifting the restrictions. This will have to be something that Jabiru didn't previously measure up to, that other engines DID, where Jabiru can demonstrate a change. This is essentially what people have been asking for when asking for justification for the restrictions - a measure to meet to have them lifted or - Demonstrate that the rate of engine failures has decreased statistically. Given the low number of occurrences overall, and the fact that you need statistics over over a reasonable lifetime in a range of operations, it will probably take 5-10 years to get statistically valid data. These statistics would obviously also have to be a measure where Jabiru failed and other engines passed. CASA might have a problem where they can't produce a trigger for lifting the restrictions without providing evidence that the restrictions were not justified i.e. other engines must also pass the same test. A note on statistics: Statistics is more than a count of occurrences or even a set of data. Statistics is a set of tools to tell you whether you can draw reliable conclusions from your data. If you have data with the number of Jabiru failures and the number of other engine failures, the science of statistics can tell you whether you have enough data to draw a conclusion and how reliable that conclusion is. I haven't seen anything like this produced. I have my doubts whether CASA actually employ anyone with statistics qualifications.

The problem is that people don't look at the actual risk. They look at what other people guess is the risk. If you look at the actual incidents of people killed on the ground, it is clear that the most risk comes from: 1) Cargo flights 2) Small jets 3) Large jets 4) Military jets 5) Medium turboprop Not necessarily in that order, but these are the aircraft that appear most in accidents where bystanders are killed on the ground. Single engine piston barely appear on the list - even when they crash into urban areas. It's not really surprising if you look at it objectively - the danger comes from speed+mass, and fuel carried.

Landing on crossing runways, basically the same distance to run, both go around. ATC were behind the situation and were not separating the aircraft at the critical time. There appears to have been little time for ATC to issue vectors and the aircraft were below minimum vector altitude. The instructions issued by the trainee were unclear and it seems misunderstood. The aircraft may not have got too close but that looks like good luck not good management. http://atsb.gov.au/publications/investigation_reports/2015/aair/ao-2015-084/

2 aircraft crossed paths when ATC did not intend it to happen. ATC didn't specifically separate them by altitude or track. One was at 4 mile final when the other was turning base 3.5 miles from the crossing runway. Then both aircraft go around. The only thing that separated them was big sky theory, and we know from experience that the sky is not so big in the vicinity of an airport. So this does look pretty serious to me. Way closer to an accident than we are supposed to get.

I think the 161 Warrior is probably the most common PA-28 in training now, and 140s are mostly in private hands. I don't see that I can separate to that level, but since we are interested in the engine not the operation it probably doesn't matter. I searched for Pa-28, C172, C152 engine failure or malfunction from 2007-2012 inclusive (6 years). I got about 160 records. It's a bit hard to interpret, many of the records don't give a reason for the malfunction or much detail on where the aircraft ended up. My counting came up with: * 70 incidents with a serious loss of engine power in the air. * 35 incidents where the aircraft ended up off runway (most off airport, some overran the end of the runway etc. after engine failure) * 24 incidents where a major engine component failed (cylinder, crankcase, valve, fuel pump, fuel controller etc). That's only the incidents where it is spelled out explicitly. However... it doesn't tell you much without the total hours to work out a failure rate. It does tell you that Jabiru engines are not the only engines that can and do fail. I will attempt to attach the data file for those who want to do their own analysis. The biggest problem with the Jabiru issue is that the RAA rules were developed when the engines in use were much less reliable and already assume that engines are unreliable. Unreliable engines is the reason we have a low maximum stall speed. Unreliable engines is the reason we have a low maximum weight. Unreliable engines is the reason we are limited to 1 passenger. Unreliable engines is the reason we are required to be able to glide clear of built up areas. Sure, restrict to GA Jabirus that do not have the same restrictions if it is believed that the engines are not up to certified standard. But I don't see the reason for additional restrictions when the assumption of an unreliable engine is at the heart of the rules we operate under. ATSBSearchResults (6).xlsx ATSBSearchResults (6).xlsx ATSBSearchResults (6).xlsx

I also searched for Cessna 172 specifically, there were about 50 Engine failure or malfunction reports in the last 5 years.

Just playing around with search on the ATSB site. Searching the last 5 years: Detailed Data Results You searched for: Date range: From 03 Jan 2011 to 02 Jan 2016 Location: All Occurrence Category: All Occurrence Type: Engine failure or malfunction Aircraft and Airspace: Manufacturer: Cessna Aircraft Company - All, Piper Aircraft Corp - All Injury Level: All The number of occurrences during this time period were: Total 334 Accidents 35 Incidents 247 Serious incidents 52 Number investigated by ATSB 25 334 reported engine failure or malfunctions in 5 years from Piper or Cessna aircraft. Any foreseeable danger there?

That doesn't tell you much, just refers you to sb-912-066 but from my reading sb-912-066 says if you have the new style cylinder heads, you need to change the instrument labels and temperature limits to match.

Missed a word: Anchorage did what they had to do to make the business >look< profitable It doesn't appear that they made any changes to the business, just some accounting number shuffling to produce a paper profit for valuation purposes.

Is that true? It seems remarkable that someone would buy a company without the unrestricted right to use the company name. Maybe it is true, but I would like to see a reference to support it.

It's important to note that Dick Smith the person hasn't been involved in the business since 1982... turning 10 million into 520 million was the private equity group that bought it from Woolworths. More than anything it illustrates why it may be unwise to use your name as a business brand that you might later sell...

1 square foot is 144 square inches, so 14.49 pounds per square inch is 2087 pounds per square foot. C172 wing loading is about 14 lb/square foot so we only need a difference in pressure of about 0.1 PSI or 0.7% at sea level.

You need to ask the question "what is pressure?" Pressure is what we call the overall effect of air molecules bouncing off each other and various surfaces according to Newton's laws. Pressure is just Newton's laws working at molecular level in a fluid. They are one and the same. When we say that we have a lower pressure on top of the wing, we mean that the overall forces from Newton's laws of air molecules bouncing off the top of the wing is less than the bottom of the wing. This is caused by the air flowing around the shape of the wing. But there is a pressure change ahead of the wing and you will find that the actual airflow around the wing behaves as if the wing had a positive angle of attack. (Genuine question: can a supersonic wing produce lift at a negative angle of attack?) Motion is relative, it just matters that the air is flowing relative to the wing. A wing works the same way when the aircraft flies at 100 knots airspeed into a 100 knot headwind and 100 knots airspeed in still air. It doesn't matter which is actually moving.

The longer path theory was just someone who didn't understand Bernoulli trying to explain Bernoulli.

It's not a combination - THEY ARE THE SAME THING. 100% of the lift comes from mass displacement - that is what Newtons laws say, and there is no way around them. The mass is displaced because of pressure changes around the wing - higher pressure below and lower pressure above. Bernoulli tells us that if we change the pressure, the speed must change, and if we change the speed the pressure must change. Changing the speed of the air is exactly what produces lift according to Newton's laws. Bernoulli is talking about energy, Newton about momentum. You don't have either energy or momentum, you have both. Measuring only one doesn't mean that the other ceases to exist.

The arguments about how planes fly are kind of like arguments about whether cars move due to power of the engine, torque at the driving wheels, friction between the tyres and the road or Newton's laws of motion. With each one you are just analyzing from a particular point of view - you are not excluding the others. The reason why there are arguments is that it is almost invariably taught by people who don't understand it in the first place.

I'm pretty sure there would be enough redundancy and computer power to do this without additional devices. E.g. when everything is working the computer knows your airspeed and AOA so it can deduce the weight. If you lose airspeed, it should be able to know the last good weight (correcting for fuel burn) and deduce approximate airspeed from AOA. If there's enough information for a pilot to fly on the instruments, the computer/autopilot should be able to do a passable job.

When I said unstable I meant that in these specific situations the aircraft would not maintain straight and level without immediate pilot input rather than referring to alternate law in general. AF447: The autothrust disengaged during a speed change, so the thrust was set to less than required for level flight, plus there was turbulence requiring pilot input to maintain wings level. AirAsia: The rudder was off centre so the aircraft immediately rolled when the autopilot disengaged. There is also more than a page in the AF447 report describing Aeroplane behavior in reconfiguration laws which concludes: ...the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall. So I think by at least some definitions the aircraft is not stable with respect to speed. But if the autopilot has disengaged and the aircraft changed to alternate law, it also suggests that something has happened that might also destabilize the aircraft. No doubt. But what percentage of these incidents resulting in crashes would be OK?

I'm not suggesting something that would hold altitude or even course - just enough to give the crew time to take over with the aircraft under some form of control. I think this aircraft had rolled to a 55 degree bank about 6 seconds after the autopilot disconnected. The AF447 report listed a set of pitch power combinations for loss of airspeed at different altitudes. If a degraded autopilot simply maintained wings level and airspeed/AOA/pitch+power depending on the information available, until the crew can respond to the autopilot failure it would be a big improvement.

The PIC was ex airforce with experience in transport and fighters so it's hard to make that case. It is startling how similar this is to the AF447 case though. In both cases the autopilot unexpectedly disconnected, leaving the pilots with an unstable aircraft in alternate law. In both cases the loss of control was very similar. One interesting tidbit is that the dual control warning was overridden by the stall warning. You wonder whether the autopilot needs some sort of fail-safe so that instead of disconnecting completely it would maintain wings level with pitch attitude/AOA and thrust based on last good data, to give the crew time to deal with the failure. The current system seems to require an immediate unusual attitude recovery in alternate law.

I was trying to give the benefit of the doubt to those more experienced than me, but yes that's probably true.