Date: 07 Aug 99 01:22:38 From: "Tim Lee" <email@example.com> Organization: BT Internet References: 1 2 3 Followups: 1
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Matt727 wrote in message ... >Tim Lee wrote in message ... >>Hang on a minute, James! >> >>Frankly, 6.5 tons is not a huge amount - not at this stage of >>development, anyway......... > >Not a huge amount? If you say so.... Not particularly, no. Have a look at the weight of seat back video systems (Virgin are even looking at gyms, for god's sake!), and this puts a slightly heavy airframe in perspective. In any case, have a look at Airbus' press release on this subject. >>>The run to Europe from Singapore in an A340 is nearly an hour longer >>>than it is in a 747, or a 777. It is extra travel time, and it >>>complicates connections within Europe. >> >>The 747 is a quick aircraft, but I doubt this is true for the 777, which >>has a stated cruise of 30kts less than A340. > >747 Mach .85 >777 Mach .84 >A340 Mach .82, but it has to go slower for the long range. Since I wrote this, I checked up. Compare the BA flight time LHR-LAX by 744 with the VS time on the same route (340). >>Prove this one, please! AI aircraft have a similar climb rate to the >>777, and the 747 climb performance can be dismal... Also, no-one can >>convince me that any aircraft in commercial use can climb over a cu-nim >>cloud - they can peak at over 60,000ft..... > >It has nothing to do with how fast it can climb... it is about wing loading. >As you go higher the air gets thinner. So if you are at MTOW in a A340 you >cant climb way up high because the thin air wont support the aircraft. Now, >if you have a big Boeing wing you can go right on up. That is how it works. >Wing loading and air density at altitude. I still refer to the original mailing - the original comment implied that the Airbus would have to either fly around a cu-nim, or not fly, because it couldn't climb over the top. I repeat that since cu-nims top out at 60k +, nothing on the civil market could overfly it, so rate of climb is academic in this case. I think you'll find in any case that most aircraft finish the cruise at a higher altitude than they started it for the reason you quote, Boeing included. >>AI products do this without problem - VS toc is typically 39,000 on the >>HKG-LHR with a 340. > >Sure, maybe at a LOW aircraft weight. So how heavy is a 744 after the run from HKG to LHR? >The A340 has the same wingspan as the 777, but the mean chord is way less >therefore creating a wing with less area. (I hope no one at Airbus reads >this... then they would know how to make a good airplane! (a bigger wing >also adds fuel capacity!) But the AI wing has a higher aerodynamic efficiency (l/d ratio). The Boeing wing is hardly SOTA - it was orginally put together for 707, and has changed little, except in size, since. >>Do we work for Boeing by any chance? > >........and where do you work? I work in consultancy - not with AI. By profession, I am a Chartered Engineer, and a member of the Royal Aeronautical Society. Tim.