FLY777UAL From United States of America, joined May 1999, 4510 posts, RR: 3 Reply 2, posted (14 years 1 month 1 day 5 hours ago) and read 1931 times:
Well, other than the obvious "Concorde" answer (thank you Iain!), I believe that the fastest SUB-sonic airliner during commercial service is the 747SP, this due to the power to weight ratio with the PW's, and the reduced weight and drag from the fuselage shortening (among other modifications).
Airbus Industries, however, claims that the A340-200 has set the speed record--not flight time, but MPH (I believe they were flying AKL-Europe non-stop on that one...).
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 6, posted (14 years 1 month 14 hours ago) and read 1859 times:
Ummm, 660 mph is 574 knots. The speed of sound at -60C is 573 knots. I'm having a little difficulty with the declared speed of either a CV880 or 990. Not the posters who have these handles, but the airplanes mentioned above.
There are a couple of determining factors about how fast an "airliner" can safely go. By airliner, I understand something the size of an F-28 or above, and a jet powered aircraft. In the old days, a DC-4 was an airliner, as was a DC-3...
Jet powered aircraft are usually far less efficient in design than the engines strapped onto them. What I mean by this is that the airliner can only go so fast before it approaches the speed of sound. Approaching the speed of sound, drag increases logarithmically, hence very efficient "streamlining" is required in the airframe design to minimize that extra drag.
The drag phenomenon makes itself known though prior to the aircraft going M1.0. Due to various curvatures on and around the airframe, certain airflows over the plane may reach local M1.0 even though the airplane itself is only doing, say M0.85. This becomes the Critical Mach number of the airframe.
Modern jetliners are now routinely flying at M0.86 (B747-400, MD11) to name two. Some (G-IV and Citation X) can achieve M0.90 or slightly more. Mind you, they might not be considered to be jetliners by some. I'm just using them to illustrate the discussion.
Having said all this, even when the airplane is cruising at it's fastest cruise speed, the engines are more than capable of providing more thrust. Most modern jet aircraft can easily exceed their MMO's in level flight, but at great cost and great danger.
So the best way to improve the cruising speed, i.e. obtain the highest MMO possible, is to improve the airframe design. Two noticeable means of achieving this are the incorporation of area rule (DC-10, MDll center engine nacelle design, B747-200 upper deck design) to delay onset of supersonic airflow, and drag reduction (winglets, optimum airfoil design/sweep). I say drag reduction because no operator is going to operate their jet aircraft above its best lift/drag configuration for long if they want to make any money at it.
There is a lot more to this subject, and I apologize in advance for not expounding each point in more detail. But I suspect some haven't even made it down this far...
In closing, other than the Concorde and the Russian TU-144, I would offer the two I mentioned above (747-400,MD11) as my answer to the posed question.
David L From United Kingdom, joined May 1999, 9297 posts, RR: 42 Reply 8, posted (14 years 1 month 12 hours ago) and read 1840 times:
Of course you're right about the CV-990, Buff but, from a Big Book I have, the CV-990 still managed a maximum level speed of 615 mph with the 747-200B at 602 mph and the MD-11 at 597 mph. I'm sure it depends how you measure it, though. What a pity Convair didn't get the CV-880 quite right from a marketing point of view.
I believe Convair's '880' and '990' referred loosely to their speed in feet per second though I've never bothered to check the numbers to see how well they succeded. That would make the 990 10% faster than the 880. Maybe it was just the '880' and '990' was a logical number for the follow-on.
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 9, posted (14 years 1 month 10 hours ago) and read 1830 times:
Thanks DavidL. I'm not as big a "buff" on some of the finer points as you've posted, historically speaking. Your observation makes a lot more sense, although with those older generation airframes (CV), I doubt it was an economical cruise speed!
With regards my posting above, I was responding to the statement "The Convair 880 and 990's routinely turned 5 hour flights into 3.5 hour flights or less....They cruised at over 660mph....cruised mind you." Perhaps I overreacted to poetic license!
Interesting topic though - thanks DavidL for putting some real numbers into the discussion!
D L X From United States of America, joined May 1999, 10795 posts, RR: 52 Reply 12, posted (14 years 1 month 3 hours ago) and read 1810 times:
yes, the 777 is pretty quick, but still is not as quick as the 747 and i guess MD11. Surprised to hear that it was so quick, but I guess since its based on the DC10, which was also designed around the time of the 747 when fuel costed less than water practically. (As an aside, fuel still cost less than Coke. )
An interesting note is that the 767 and 757 are both rather slow in comparison to other jets. They were designed during a fuel crisis, and emphasis was put on incredible efficiency which inherently limits speed. (That's probably why 767s make such good gliders ) I don't know if the new 764 is any faster with its new wing. I know the new wings of the 737 series made them faster and more efficient. Completely a function of the cost of fuel at the time of design...
David L From United Kingdom, joined May 1999, 9297 posts, RR: 42 Reply 14, posted (14 years 4 weeks 20 hours ago) and read 1798 times:
Buff, I hope I didn't come over as a know-all. I just looked it up! The reason I looked it up was because I was as surprised as you were by the 660mph figure (sorry to go on about it, DC-10 - you were right to bring up the CV-990) but thought the 990 was faster than your average airliner. Of course, it no longer enters the equation for current aircraft.
As for the economies of flying at 615 mph, the point here may be that it's a maximum speed. I have no idea what speed they were typically operated at.
But I also heard, on a documentary about the 747 on Discovery last night, a 747-400 captain from Virgin saying one of the things he liked about the 400 was that "other than Concorde, it's the fastest commercial aircraft". It was on TV so you must be right, Buff!
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 15, posted (14 years 4 weeks 16 hours ago) and read 1795 times:
If it's on TV, then it has to be right, eh?! Again, I was only referring to the original question of cruising speeds. I remember hearing a 747 call in his speed as M0.86, a G-IV M0.87, and Cessna advertises their C-X to "cruise" at M0.91.
And it is me who should apologize David L for getting so carried away with this topic!