Ian

Liquid sodium has extremely good head transfer properties which is one of the reasons why they've been trying to use it in Nuclear reactors for a long time. You're right in that it weakens the stem, however it has a significant cooling advantage. Like everything, its a tradeoff and it would appear that some rotax's were having enough of an issue to accept the compromise. Below is a link to more information. https://www.rotax-owner.com/en/support-topmenu/40-uncategorised/658-si914030-914

The environment that valves operate in is extremely harsh and the metallurgy complex. A quick summary of what they do to address this is https://www.intervalves-technologies.com/exhaust-valve/ The difference between nominal operating temperatures and temperatures high enough to damage the valves is fairly small. Modern car engines, being computer controlled have smaller temperature excursions than the more primitive tech used in airplane engines. My guess, and it is a guess is that this valve has been running hot at some point so you're seeing pitting in some areas, ablation and deposition in others. Rotax introduced sodium filled exhaust valves, which assist in valve heat removal, in some engines which indicates that the margins in their designs were close enough to warrant design changes.

I'm not too sure about the cavitation explanation and physics given here. Steam bubbles don't implode in gaseous mediums. Cavitation is a process that only occurs in liquid phase and the collapse of vapor bubbles creates extremely high energies which damage materials. https://en.wikipedia.org/wiki/Cavitation Water or Water/Methonol injection is commonly used in engines and only in exceptional circumstances will it cause erosion of metallic components. What is more common is erosion of turbine components due to water droplets impacting high speed compressor components or with extremely high usage remove lubricating oils.

I believe that CASA is taking feedback on this subject at the moment after they found that rejecting pilots because of a diagnosis and on medications was found to be incorrect. However I believe that there's a bigger issue at play here. There's an article on diagnosis trends here which reflects an increase from 6% to 10%. Personally I believe that a number of people in this category would make fantastic pilots and they are interested. They are high functioning people, I'm saying that not in terms of amongst their peers but amongst the population in general, we're talking lawyers, doctors, scientists project managers etc.

I recently came across an article where a pilot was refused a medical because he was taking Ritalin for ADHD. Later this was overturned by the AAT on the basis that CASA failed to adequately assess the situation. https://hwlebsworth.com.au/adhd-diagnosis-not-fatal-to-aviation-medical-certificate-application-nam-v-civil-aviation-safety-authority/ CASA now appears to have the policy under review and are asking for comments. https://www.casa.gov.au/licences-and-certificates/medical-professionals/dames-clinical-practice-guidelines/attention-deficit-hyperactivity-disorder-adhd#Attentiondeficithyperactivitydisorder(ADHD) I find this stance interesting because a number of my work colleagues have been diagnosed with mild ADHD, take medication and I regard them as some of the top performers in their field both prior and post their diagnosis and subsequent medication. It's even more interesting that given the penchant for Defence forces, included the US DoD to provide the very drugs prescribed for ADHD reducing the error rates and alertness for extended combat missions and high operational loads. https://pubmed.ncbi.nlm.nih.gov/7661838/ https://jmvh.org/article/should-the-australian-defence-force-conduct-a-drug-trial-of-wakefulness-promoting-medications/ I'd be interested in people's thoughts on this matter as these same people are interested pursuing their pilots licence. Personally I think that numerous pilots appear to have traits which would fit on the spectrum which could be considered sufficient to get them diagnosed with ADHD. If this is the case, would they be better pilots if this condition was treated?

Yeah this is a fair call and I'll probably rail against the injustice of the world at that point. But on the flip side I still remember a trip into town with my Grandma who lived in regional Australia when I was young. It remains one of the scariest experiences of my life, luckily no-one else was on the roads. However I still believe that assistive technologies are really beneficial to older drivers. For example my mother's last car has lane assist tech which alerted her to the quality of her driving which sadly is not what it was 20 years ago. It has improved her driving considerably because it has made her aware of her deficiencies.

But there is also plenty of evidence in Australian that this view is promoted for revenue raising. For example the state Governments have strongly resisted releasing the dataset associated with road fatalities and only recently has the Federal Government, after encountering years of resistance tied road funding to releasing this data. https://www.drive.com.au/news/government-under-fire-over-road-safety-reform-as-death-toll-rises-again/ We need a policy which reflects deaths per km travelled and balances the needs of those who regularly travel long distances in regional areas. Or preferably fund the building of lots more high quality airports and airstrips. 😉

There are excellent older drivers and pilots, however it's likely that they were even better operators in their heyday and it's regretful that we place additional burdens on them however amongst their cohort is an increasing number of dangerous drivers. I'd actually like to point out that the current requirement for getting a driver's licence are far far higher than what was required 60 years ago. Then you did a written test which was laughable simple, practiced three months and did a driving test with the local policeman. Many people simple drove around the block or less, four left turns and parallel park in a 100m of free space. Now people have to pay instructors, spend over 100 hours driving with an instructor, do a driving test which takes 30 minutes, and pay for tests. I'm all for pushing back to the original approach because based upon my experience and the comments here this hasn't resulted in any changes at all to the quality of drivers and has only created a cottage industry made possible by bureaucracy. Testing all drivers with the same frequency would be dumb when we have better information. Older drivers, and pilots are simply more likely to be struggling in terms of baseline competence and getting worse, in this situation they're more likely to endanger others, so it makes sense to test their competence frequently. Look at both Biden and Trump, they're both in cognitive decline and if they were driving or flying I'd want them tested regularly. Below is an example of what can happen, would you like this guy flying your plane or driving your car. https://www.abc.net.au/news/2023-08-31/senator-mitch-mcconnell-freezes-up-for-a-second-time/102796926

Testing for bowel cancer isn't done for all ages because it is better targeted at specific age groups. There's a cost borne by both the individual and public when testing and it's better to do this in a targetted manner. Similarly testing the skills competency of people is best done to address the actual risks. I don't object to testing every 5 years however 5 years is far too long for older people. People often have a significant cognitive decline over a single year. I was following an elderly driver the other day who was driving at 40km/h on an 80km/h road. When navigating a roundabout he pulled out in front of another car. Clearly he shouldn't have been in control of a vehicle that can kill people. I agree that getting old is bad and that many older people are both mentally and physically capable, however we do need systems which address the risks associated with ageing. That being said there are some drugs which may slow the process, rapamycin, D+Q etc.

Actually it's not agism, it's science. 80 year old drivers accident fatalities are on par with new drivers, and they get worse not better. Ageism is where an unreasonable bias is held against the elderly, in this case it's a reasonable bias. It's better to spend public resources where they're actually necessary, we've made getting a licence incredibly burdensome for the young, often requiring hundreds of hours of supervised driving. We do SFA on policing the similar decline in driving skills. The current scheme of getting a doctor to decided if a driver has adequate cognitive skills is frankly woeful. A computer generated based test which simulated busy traffic which tested reaction times and decision skills would be better.

Technology can make for better drivers. Just as technology can make for better pilots. My experience is that there are poorly trained drivers. There are also drivers who are so old they're no longer competent to drive. If a computer can drive a car better than a person let the computer drive. Similarly I'd like to see planes largely automated allowing someone with limited skill to fly, it would improve the infrastructure and quality of life of many many people.

Personally I'd like to see the highway/freeway speed limit lifted to 160kmh for electric vehicles with automate safety features and a demonstrated low highway accident rate. This would make electric cars more useful. I would note that state government are fighting the release of their accident data. I suspect that this is because the areas where they raise the most revenue from speeding to keep us safe are not the areas where accidents occur. https://www.drive.com.au/news/urgent-call-secret-crash-data-shared-toll-rises/

ADSB is a tool which provides additional information on suitably equipt aircraft in the vicinity. Being proud of the fact that you switch ADS-B off is the same category as being proud of not wearing a seatbelt, or of not wearing a helmet when riding a motorbike or being able to drive home after having a skinful. The see and avoid report is a pretty blunt assessment of the efficacy of the approach. I tend to agree with the likelihood of ADS-B becoming a mandatory requirement at some point in the future if the price of in and out continues to drop. That being said ASD-B is a flawed technology from a protocol point of view.

The short outtake from the video. There are a lot of unknowns associated with the impact. Two aircraft collided, one joining downwind, the other doing circuits with a crosswind join and turning downwind. One was a high wing, the other a low wing. Both Aircraft were fitted with ADS-B. One of the pilots didn't like the FAA knowing where he was an would often switch the ADSB off. This was a view that he frequently shared with his associates. Whether activating his ADS-B could have saved his life is unknown.

Buy again if you're based in Canberra your options are limited. Canberra to Cowra is about 2.5 hours, so a round trip commute is 5 hours on top of a working day doesn't really fit. This doesn't mention hitting roos in the morning and evening. Compared to Goulburn which has a RTT of 2 hours along a much safer road allows a single day trip. But the comments about the weather are valid.