Ian

So where we are is that Sensing mechanisms for knock detection are common and low cost Acoustic sensors are probably the simplest approach. No-one is aware of it being done on Lycoming engines. There are many mechanisms for controlling knock including mixture & throttle control but other mechanisms requires tweaking ;-). Of interest is the knock frequency calculator https://phormula.com/knock-frequency-calculator/ The frequency for the an 0360 would be about 4.4 kilohertz.

I wonder if this relates more to the condensate of carbonic acid ie CO2 in liquid water in a long exhaust where the gases cool significantly. This could possibly corrode steel exhausts. Are the exhausts of an airplane likely to get to the temperatures where an the steam would form a condensate and be able to form an acid? Probably only during startup. https://content.ampp.org/materials-performance/magazine-article/2613/Some-Aspects-of-Steam-Condensate-Corrosion

Your understanding of the term differs from mine. From the Oxford dictionary definition improve (a mechanism or system) by making fine adjustments to it. "engineers tweak the car's operating systems during the race" Based upon the above I think that adding telemetry doesn't change the system so it's not a tweak. Happy for you to continue to disagree but I'm not buying. 😉 You can take this to extremes and ask yourself if putting a car on a dyno is a tweak? It's temporary external instrumentation.

As I said, both events can ruin your day. Is AVGAS now a low sulfur fuel? I know that sulfur has been stripped from both diesel and automotive fuels.

Exhaust gas is already full of water, which also goes into the crankcase. Water injection doesn't greatly impact this issue and exits the engine as steam along with combustion steam. If you're using water injection during landing there's other issues at play. Yes water is heavy however water injection is only needed across a small fraction of the flight envelope, so the weight penalty is small in relation to the benefits. Cruise and decent don't as a rule require optimal RON fuel. Corrosion of the fuel system was effectively controlled by mixing a small amount of water soluble oil into the mix. I'm not familiar with severe corrosion being caused by water injection in the exhaust and I haven't seen or heard of this being an issue. I've never seen it in cars and it's not mentioned in the STC for water injection in planes. Water is an existing component of exhaust gases equal in quantity to CO2. Basic organic chem says there's about 2 hydrogen for every Carbon atom in hydrocarbons, water injection just puts a bit more steam into the mix. Wherever there's an air conditioner there's a ready supply of clean distilled water, so availability's not that much of an issue. Water from a rainwater tank also has very low levels of electrolytes and you can test it with a simple electrical device. Water will be far more available than lead in the future.

Knock detection is an out of band event sensor. There's no requirement to direct engine control, it's similar to an EGT sensor. I wouldn't characterise it as tweaking, I'd probably characterise it as instrumentation and telemetry.

For those of you who hold the quality control of AVgas in high regard the following article might temper your beliefs. I'm not sure if standards were changed or adopted as a result of this. Trust but verify is a pragmatic approach & knock sensors might be relevant. https://www.atsb.gov.au/publications/2001/sir200103_001

Knock detection allows a safe way to operate closer to detonation limits especially with lower quality or variable fuels, and also could allow for the detection of a bad batch of fuel on the ground with an engine run up. As has been suggested, knock detection goes hand in hand with digital engine controls which on automotive vehicles add a cost of far less than $100 per engine. Digital systems can and do operate engines far more reliably and intelligently than people and the ongoing reliance on manual engine control is a blight on the industry. There is no reason for FADEC on a plane to cost significantly more than automotive systems or to be anything but standard, however we are where we are through well intentioned but poorly implemented policy controls. It's also worth pointing out the knock and preignition are different beasts. Knock is detonation of fuel air mixture where the chemical reaction is propogated by a shockwave rather than a flame front. Preignition is where something other than the spark is igniting the fuel air mixture, such as an overheated exhaust valve. Both can ruin your day, however it's important to understand the distinction. Knock sensors will detect detonation but not preignition (unless the preignition then also creates a detonation event) There are a number of controls that can be used to stop knock. Making the mixture richer Cooling the intake charge Retarding ignition Octane enhancers such as water or Water/methanol Reducing manifold pressure. Running rich of peak is safer for sacks of meat because humans can't effectively juggle the variables in real time in a consistently manner. In short, digital systems have operated engines for the last 40 years lean of peak through all phases of operation far more safely, reliably, efficiently and at higher power levels than people can. The question is, can we utilise some of the technologies developed in the Automotive space to make flying safer? Knock sensors are a baby step with limited gains however it is an important functional sensor for safe engine operation. For those concerned about the octane ratings of lean vs rich fuel mixes, water injection also can increase the RON by 25 which if implemented would provide significant safety margins for METO operations. It's not new technology, the Germans in WW2 used it effectively to compensate for their poor quality fuels. It's also available, far less toxic and cheaper than Tetra-ethyl Lead. It's also cheaper to retrofit than an engine rebuild. https://pmc.ncbi.nlm.nih.gov/articles/PMC6389520/

Yes however I'd expect direct injection as a retrofit to be at least an order of magnitude more difficult to develop and install on existing aircraft. Is backfiring a common damage mechanism on existing aviation powerplants?

You're absolutely on the money here. Virtually every petrol vehicle that's on the road today detects knock and retards the ignition, however as airplane engines don't have the strict emissions targets of their land based brethren, enriching the mixture or even water/methanol injection can assisting in controling knock. In the experimental world there are a number of providers selling electronic ignition and fuel injection solutions. But none of them appear to have knock sensing logic. Digital systems do a much better job than people in ensuring that engines operate using the best possible parameters be it maximising power, minimising fuel flow and keeping engine temperatures sane. Given the low cost commodity nature of these systems it seems insane that there isn't more development in this area. I can't see a long or even medium term future for leaded fuel, even without a national approach, it's simply too toxic to withstand a concerted effort from a concerned local community worrying that their children are being brain damaged by the folly of a few people who love to fly. Even though the real reason is that they simply don't like the noise. https://pmc.ncbi.nlm.nih.gov/articles/PMC3230438/ I suspect that part of the change will involve a significant push towards mogas as the standard fuel for the GA fleet as High octane lead free fuels will not be cheap. Many flying schools operate today on Mogas due to the economics. To mitigate the risk of fuels with less stringent quality controls electronics appear to be the simplest and safest solution.

Don't mention the war.

Amen

It doesn't matter if you're not convinced. The fact remains underground HVAC is a shitty solution. As stated, the main reason for underground cables is voters and very occasionally safety related issues such as proximity to a runway. Would the subterranean power lines have the (a) same (b) lower (c) higher maintenance cost ? Generally lower maintence costs however things like active soils etc can reduce lifespan. But this is dwarfed by installation costs. I suspect that the service life of underground cables is significantly longer than for aerial. The same line again the pipelines carrying the cables would have a very long service life. The service life of underground power lines is less than above ground. Generally about 40 years for below ground and 60 years above ground but technologies may change this. The service life is lower because it's a harsher environment, water ingress, salts, ground movement etc. The other differences is that you are likely to be able to increase the capacity of above ground powerlines at a later date. This isn't an option with below ground. If you don't believe the service life argument ask a farmer if fenceposts last longer above ground or below ground. Below ground power lines are technically an inferior solution. For example most power lines are heat limited, heat dissipation is worse underground as the ground acts as an insulator. You also get higher capacitance leading to higher power losses in operation. So you lose more power per km underground than above ground. In short underground power-lines cost many times more, don't last as long, can't be uprated, have higher power losses and are heat limited. If you're not convinced, do the research. https://shop.elsevier.com/books/transmission-and-distribution-electrical-engineering/bayliss/978-0-08-096912-1 Note the safety related runway context to make it aviation related 😉

But the question remains, does anyone do it for Lycoming engines? From a safety point of view it would be nice to know when the engine is misbaving. I used to have a Subaru B4 which was designed for 100 octane fuel and detuned for the Australian market. Bad batches of fuel occurred on a regular basis from all the fuel majors and it would ping badly when you accelerated. The "fix" was putting a few litres of ethanol into the fuel which was even easier when E85 became available.

Not all knock sensors are so pricey, acoustic and ion sense are reasonable cheap. Ion sense is build into mazda coil on plug assemblies. https://www.repco.com.au/clearance/fuelmiser-knock-sensor-cks268/p/A5385939?rgfeed=true&cid=google-shopping&utm_source=google&utm_medium=cpc&srsltid=AfmBOoqFnb7sk-BUKrs6KvjrYySLBj1HwytQ-coYDxRczNsUUhGzBPYWcHg&region_id=100001

Hi All, I was wondering what the general consensus was with knock detection on lycoming engines was. Knock detection is standard fare in auto engines, allowing advancing and retarding ignition based upon knock. The cylinders ring like a bell with the sound be loudest at the fundamental or harmonic frequency based around the diameter of the cylinder, knock detection is largely a microphone. Another approach is to test current using the sparkplug post ignition. This is used by Mazda amongst others and would provide a non-accoustic approach. From what I've read there seems to be a view that aircooled engines are too noisy to detect knock but I haven't actually come any actual source material where someone states this outright. Lycoming has done laboratory testing where they are detecting knock under various load conditions. If this is acoustic based it might be a reasonable approach. From what I've seen none of the electronic ignition kits for experimental aircraft offer knock detection as a feature, however I could be wrong. Given how destructive knock is to aircraft engines it seem to be quite a desirable feature. Thoughts welcome.

Apparently aspects of it were enforceable, it went to court on a couple of occasions and the findings were not in John's favour.

Just a bit of a correction in relation to the Goulburn Airport. My understanding is as follows. It was originally privately owned by an aviation enthusiast. It was donated to the Goulburn council on the basis it remains an airport. The council was convinced somehow that selling it to John Ferrara would be a good idea. The sale proceeded on the basis it remained an airport and the existing leases were honoured. This has been a point of significant contention over the past few years as attempts to charge fees on the existing leaseholders were taken to court. It's a pity really as the effective closure of Canberra airport to GA activities has created significant demand. With a little foresight, a large GA fleet and associated industry could have been established in Goulburn.

Freecad can provide the functionality your need without the licensing shenanigans of products like fusion 360. There are also tutorials online which can provide basic instruction for those without a background in this space or for those with more advanced skills there more advanced tutorials. There's also a comparison between Freecad and Plasticity.

Not that it relates to flying except as obstacles. Putting power lines underground is about an order of magnitude more expensive, and transmission lines are expensive enough that you've zero hope of getting the capital back. The only reason it is every done is to appease local voters with lots of government subsidies. Transmission and distribution already make up about 40% of your power bill. Image multiplying this by 10. Humelink costs have gone from the initial estimate of $1B to $5B for 365km of transmission. It's also worth noting that this is a regulated asset, so returns are guaranteed to the builder. https://www.afr.com/policy/energy-and-climate/transgrid-inflated-cost-of-running-power-line-underground-farmers-20230718-p5dp2o

Actually not sure if this definition is quite correct. Technically windshear is a change in wind velocity over a relatively short distance, it can occur at height or can be in the vertical or horizontal direction. It's most dangerous when landing or taking off because the plane is already marginal and it results in a net loss of airspeed. Wind shear can provide additional lift depending upon direction. https://en.wikipedia.org/wiki/Wind_shear Interestingly enough dynamic soaring uses wind shear to gain energy and there's a lot of energy to gain.

The only way to change this is to Effectively lobby an MP. Offer to fly one to and from parliment to save on their travel time. At least write to them so they're aware of the issue. Get elected. Fly over towns with a big arsed sign trailing out behind. Moaning on a forum will achieve very little. ps I think that the ASIC card is required to do the navigation exercises of the PPL

T Rule #1 isn't a truism, all security strategies have costs and benefits. If a control leaks information it still may be beneficial. ASIC's are denied for multiple reasons. Mostly because people are arseclowns with a history of violence or drug associations. ASIC cards, as they stand are security theatre, they are highly visible, costly and provide little actual benefit. Their main role is to stop GA pilots from using the airports that RPT uses. That is their main benefit from a Government perspective. The ASIC card could provide some actual security benefits which are currently unrealised. It be used to provide access control to airports rather than the half arsed pin codes which are all just inside the gates/birth years etc. It could be used to dynamically pull access to airports should a risk be associated with an individual. It could be used to assess the security controls of an airport by making them electronically readable so a log of the efficacy of you security staff was assessable. It could be rolled into a national identity card so you only have to carry one piece of crap. Instead it's a waste of time and effort. It costs millions each year with virtually zero actual benefit. It relies on a sticker for it's security, it's a joke. If you want to learn about security reads the musings of Bruce Schneier, he's a clever guy who's also interested in the US attempts at airline security through the TSA https://www.schneier.com/tag/security-theater/ If you want this to change, write to your local member and explain to him that you won't vote for him unless he promises to fix it. Stop voting for team red or team blue and actually vote on a single issue. There probably aren't enough pilots to make them care but it's worth a shot.

It's dumb having a distinction between GA and RAAus. They're all planes and the skills required are virtually identical. It purely bureaucratic nonsense. Either farm out General Aviation in it's entirety or kill off RAAus. ATSB should investigate all accidents to some degree to identify likely causes. The current state allow innuendo and game playing to run rampant.

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