From: Chuanga@cris.com (H Andrew Chuang) Organization: Concentric Internet Services Date: 05 Aug 96 04:21:20 References: 1 2
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In article <airliners.1996.1555@ohare.Chicago.COM>, Steven Foister <email@example.com> wrote: >One of the certification tests required for all turbofans involves >blowing a small charge near the root of a fan blade whilst the engine is >in operation, causing it to detach. >For the engine to pass the test, the blade needs to be fully contained. >For the new large turbofans, this is an extremely demanding test. Kevlar >is used as part of the containment because of its high tensile strength >and low weight, and Rolls-Royce and Pratt&Witney have both used plenty >of it on their engines to pass this test. >GE however have a much heavier fan blade, which is more difficult to >contain. In order not to confuse some less knowledgeable readers, I would like to point out that Mr. Foister are talking about the PW4084, Trent 800, and GE90. I don't know if the Trent 700 uses Kevlar or not, I'm pretty sure that the PW4168 does not, neither does the CF6. To the best of my knowledge, In spite of the lighter material used in the composite GE90 fan blade, it's heavier than either the PW4084 or the Trent 800 fan blades because of the much larger fan diameter. However, I don't believe it's *much* heavier. >Last I heard (January) their engine for the B777 had still not >passed this test. This one shouldn't be too hard to figure it out, right? The B777 with the GE90 engine has been in service since last November. I believe they passed the containment and bird-strike tests in July, 1995. >They were trying to get a test which involved >detonation half way up the blade (much less demanding) accepted instead. The standard test is to detonate at the root. For the GE90, I believe it's in the flow path, but not half way up the blade. >I believe that the GE90 engine is actually only operating at present on >several such temporary waivers. Misinformation. >Which would make me think twice about getting on a (GE-powered) BA 777. It's reported that China Southern may soon start B777 trans-Pacific services (coincidentally, with the GE90). Initially, they will make a techinical stop in Alaska, but will switch to non-stop when the IGW version is available. I think it'll be very interesting to take a 12-to-13-hour flight across the Pacific on a twin. Irrespective of powerplants, I personally don't feel that comfortable of doing so.