[ceejayoz]

Cars and planes have significantly different impacts on the engine.

https://www.flyingmag.com/aircraft-do-car-engines-make-good-...

> Car engines are designed to provide quick bursts of relatively high power output for acceleration, and then only modest power output for steady-state cruising. It’s unusual for an auto engine to operate anywhere near its redline rpm or max-rated power output. Airplanes, on the other hand, usually take off and climb near 100 percent power output, followed by steady-state cruise often at 75 percent power. Aircraft engines are designed to sustain this punishment reliably over a typical 2,000-hour service life. Try running your car’s engine at or near redline rpm all the time and see what happens. Of course, we don’t know what will happen, and in an airplane we can’t pull over to the side of the road when it does.

[cduzz]

The story suggests they used a marine engine, which in turn is an automotive engine modified to run under marine conditions, which among other things includes "run at full load for hours" or "run at partial load for hours".

Typically, of course, you're not seeing a lot of elevation changes in a marine application, but with modern fuel injection that's probably not such a big deal.

[dsfyu404ed]

So de-rate and conservatively tune the engine to a peak HP that can be sustained indefinitely. This is SOP when putting automotive engines in industrial uses. Just because you don't know of it doesn't mean it's not dirt common and well practiced in industry.

2000hr equates to, generously, like really generously, a 150-200k service life. It really drives me up the wall to see you acting like this is a big number when in any other context you'd be happy to pop in and tell us about how your you're so smart because you bought a Toyota and it's guaranteed to make it that far.

[ceejayoz]

> So de-rate and conservatively tune the engine to a peak HP that can be sustained indefinitely. This is SOP when putting automotive engines in industrial uses.

Those industrial uses don't crash into a random person's house if they fail, and "conservatively tune" means you've changed the engine's behavior. The FAA likes you to demonstrate safety when you change safety-critical things.

> 2000hr equates to, generously, a 150-200k service life.

At a much higher cruising RPM, which is the entire point of the article.

[xyzzyz]

> Those industrial uses don't crash into a random person's house if they fail,

It is highly unlikely to crash into a random person’s home due to engine failure. Planes don’t drop out of the sky like stones when their engines fail. You can still fly them and pick a spot to attempt emergency landing or controlled crash.

For comparison, cars crash into people’s homes all the time, but i don’t believe it is ever a result of car engine failure. No reason to expect plane engine failures to cause these.

[p_l]

Considerable amount of plane crashes, including deadly ones, involve engine failure - often due to things that aren't present at all in automotive (or marine or industrial) use.

[xyzzyz]

Sure, but this doesn’t mean that private pilots need or want FAA to “helpfully” force them to use older tech.

The argument I responded to was about negative externalities of potentially less safe new levels plane engines for third parties. I claim that these are negligible, because the risk of the worse engines is entirely internalized among the plane occupants: with less safe engines, more people will die, but these will almost certainly be plane occupants, not third parties. Third parties do die in plane crashes sometimes, but this is either caused by pilot error, or technical failure causing the plane to be uncontrollable, not failure of the engine. On piston GA planes, control is entirely independent of the engine.

[p_l]

Ability to safely bring down a plane does depend on availability of engine power, however, as lack of it can greatly cut off possible options not to mention engine can fail in such a way that you won't be able to recover before stalling.

FAA doesn't force them to use older tech, anyway. It's just that a lot of smaller planes coast on grandfathering of older engines. Believe me, a lot of CAAs would simply love it if they could force removal of carburator-based engines outside of museum planes, because carburators are one of the core causes for engine-related crashes in GA, and requiring injection based systems would reduce a whole subcategory of accidents.

Thing is, FAA and other CAA are only requiring that you do follow through sometimes ornerous but generally sane testing requirements if you want to bring a new design. This causes considerable up front issues for new designs, but there's a reason why there's much less complaint about it than one would imagine - the ornerous rules are for when you want full certification for the plane, not any of the lower classes. TFA author was trying for full certification, so that the resulting plane would be fully usable without special allowances for flight training for PPL(A), not any of the lower-category licenses. For just flying once you have a license, the requirements are less steep. [1]

[1] My father is currently rebuilding a crashed Cessna 152, question of how deeply tested the engine will be (and thus whether the resulting type certificate would allow PPL(A) training) were discussed a lot

[Sebb767]

> At a much higher cruising RPM, which is the entire point of the article.

Looking at their demo videos, they seem to be running the engine at something like 3000 RPM, which is not that far from cruising RPM on a car.

[aeternum]

This is often achieve by simply derating the engine. You redefine redline to be 75% of what the engine was designed to produce. Then your takeoff becomes 75% power and cruise is more like 56%.

[bischofs]

the 24 hours of Le Mans, and tens of thousands of runabout marine applications with automotive engines disagree with you. The real question is would you prefer a 1950s Lycoming engine with a mechanical fueling system, or a modern car engine that has been proven in millions of vehicles?

[ceejayoz]

https://en.wikipedia.org/wiki/24_Hours_of_Le_Mans says "Racing teams must balance the demands of speed with the cars' ability to run for 24 hours without mechanical failure", which implies a slightly shorter lifespan than you'd want in a plane.

[aredox]

As if running an engine for 24 hours was good enough for a plane!

And le Mans is not an oval track: engines don't run at 100% all the time.

And how many le Mans cars break down during the race?

[voldacar]

Hence why they used a marine engine.

[moremetadata]

Its a little more complex than that. Vehicles (cars, trucks) can rely on the engine power being transferred to a high friction surface (the road) with help from gravity with immediate effect. Where as boats and aircraft are transferring engine power to a low friction medium (air and water) where gravity is important for aircraft otherwise you die when you hit the ground unless you can auto rotate in a helicopter or glide in a plane, but where gravity is not so important in the scheme of things, if those extreme risk situations are catered for.

I bet they could have got the costs down more if they had used a Toroidal Propeller.

Here (already cued for you) https://youtu.be/s_J1OYcCPms?t=23 the footage shows less vortices generated with the Toroidal propeller seen in the top half of the frame of the two boat propeller underwater.

Its these vortices in water which generate cavitation on a traditional style propeller, which leave little pits on the surface of the propeller eventually leading to its replacement as its surface contributes to more friction and thus less fuel economy.

If the friction from the pitted surface is ignored, then it can lead to parts of a blade becoming more like swiss cheese with holes that results in parts of the blade breaking off.

Wind Turbines could generate more electricity if they used toroidal blades, but currently the engineering skill does not exists to scale these blades up in size, and have the ability to "detune" a blade in gale force/storm force winds to minimise damage to the generators and the unit itself.

However the use of these wind turbines also means, the state have a stealth population control mechanism as these wind turbine blades can also be altered to generate plenty of infrasound which can be used to make large parts of the population in the vicinity feel anxious, something that's documented in the Disney sound engineering labs in the 40's/50's when the sound engineers inadvertently made themselves all feel very ill for a few days. Ergo you will probably see less people striking in future!

[stenius]

I personally don't know what will happen, but I figure that type of test is easy to do in a lab environment.

[ceejayoz]

Easy, but quite expensive to have a meaningful sample size.