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#12
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On Tue, 29 Jun 2004 21:10:02 +0200 (CEST), Nomen Nescio
] wrote: We're only talking a 400 rpm difference, here, but unless the power curve goes flat from 5600 to 6000, it ain't "pulling 215 HP'. I doubt a competent engineer would write it like that since any engineering student who wrote that would be torn to shreads. To paraphrase: "never ascribe to malice that which can be explained by stupidity". It could be a typo. Corky Scott |
#13
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Tell us what happened when you had an engine failure. I am interested to
know. Tien. "Michael" wrote in message om... Dylan Smith wrote The accepted wisdom is that aviation engines are tough, because they can be run at full rated power for hours on end, and auto engines are fragile, and must not be thrashed or they won't last very long. It was even mentioned in a thread in the last couple of weeks - I don't remember who said it, but they said "operate your car engine like that and it wouldn't last half an hour". In reality, that's nonsense and everyone knows it. The standards of testing used by Detroit (never mind the Japanese) are way tougher than anything the FAA ever thought about doing. This has been discussed extensively on rec.aviation groups. Check out this link, or just google it yourself: http://groups.google.com/groups?hl=e...lur%24mg8%242% 40merrimack.Dartmouth.EDU&rnum=1&prev=/groups%3Fas_q%3Dauto%2520engine%2520t est%26safe%3Dimages%26ie%3DUTF-8%26as_ugroup%3Drec.aviation.*%26lr%3D%26num% 3D30%26hl%3Den I've never really thought about it, but this weekend I learned how to drive the winch at the glider club. After a few launches it got me thinking - this thing about aero engines vs car engines is probably an old wives tale, possibly promulgated so people don't feel so bad about spending so much money on aircraft engine parts when yet another cylinder is cracked. That's basically it. The aviation engines we use are obsolete. Sure, they're more reliable and have better power-to-weight ratios than auto engines - as long as you compare them to contemporary auto engines. That's contemporary to the design age - meaning somewhere in the 1950's-1960's. At that point, real aviation went to gas turbines, the designs of aviation piston engines were basically frozen, the engineering talent went away, and no further progress was made. When was the last time you heard of a modern (made in the last 10 years) auto engine that just died without giving weeks (or months, or years) of warning? Not got stalled by a ham-fisted shifter or run out of gas, but actually died? I'm sure it's happened, but it's a huge rarity (whereas in 1955 it wasn't). On the other hand, I don't know ANYONE with more than 2000 hours in piston GA who hasn't had an engine failure. These things eat valves, they crack jugs, they throw rods, their carb floats sink - you name it. The truth is that aviation and auomotive use are very, very different. They have very different duty cycles, cooling requirements, and performance requirements. It really should not be a viable proposition to adapt automotive engines to airplanes - you will wind up with engines that are overdesigned in some areas and underdesigned in others. However, automotive engines have advanced tremendously in the past half century; piston aviation engines have not. Now we even have manufacturers actually using autmotive cores (which are optimized for a completely difference application), dressing them up for aviation, and selling them - that's how Thielert works. It's very much suboptimal - but the existing engines from Lycoming and Continental are such disasters that even this is a viable business plan. Homebuilders have been adapting automotive engines for years. The safety record has been abysmal. Oddly enough, it's never the engine core that fails. It's always fuel systems, ignition systems, reduction drives - all the stuff it takes to make the conversion. In other words, all the stuff that is amateur-designed rather than professionally engineered. That's why I'm not a great fan of auto conversions. It's not that there's anything wrong with the engines - despite being suboptimal for aviation, they're way out in front of the crap Lycoming and Continental are selling, even for aviation applications. The problem is that adapting the engine for aviation use is a major task, and not something to be done by a garage mechanic on the cheap. Michael |
#14
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"TD" wrote
Tell us what happened when you had an engine failure. I am interested to know. My engines use RSA fuel injection assemblies. These assemblies are mostly Aluminum - but the plug that you unscrew to remove and inspect/clean the fuel strainer is steel. There is also a spring of some other sort of steel that keeps the filter in place - one end of it pushes against this plug. This is a godawful design. You see, steel eventually rusts. The rust eventually flakes off, especially with engine vibration and a spring rubbing the area to help. The plug is installed AFTER the filter - meaning that there is nothing to filter out this rust. So the rust goes into the fuel system. I got unlucky. A large chunk of rust let go and clogged my fuel injectors (two of them, but on the same side of the engine). The vibration was horrible. I had to pull the power way back, and was only able to get about 20% power out of the engine. I was in visual conditions, but only about 500 ft above a solid overcase (I was IFR). Fortunately, I was in a twin. The other engine carried me to the airport, where I was able to land and repair the damage. Were it up to me, I would replace the steel plug with brass, and install a disposable inline automotive fuel filter. But of course that would not be legal. Michael |
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