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Why Is 747 Fastest Commercial Jet?  
User currently offlinePkone From Ireland, joined Dec 2003, 25 posts, RR: 0
Posted (10 years 7 months 2 weeks 4 days 19 hours ago) and read 16089 times:

If this has been answered separately I couldn't find it. Just curious as to why the 747 is faster than any other commerical airliner...thought that 777 or newer jets should be...as they are not, why not?

Tks.

53 replies: All unread, showing first 25:
 
User currently offlineTomgib From United States of America, joined Nov 2003, 92 posts, RR: 0
Reply 1, posted (10 years 7 months 2 weeks 4 days 19 hours ago) and read 16026 times:

good question... I´ve always been wondering about the same thing. I guess it all comes down to shear engine power. Or is it the same with airplanes as it is with boats. The longer it is the faster it will go ...??

Can´t wait to hear some good answers !


User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 2, posted (10 years 7 months 2 weeks 4 days 19 hours ago) and read 15802 times:

It definetly doesnt have anything to do with the engine power. The 777 would win there!

I am thinking it has to do with the aerodynamics of the wing.

You usually fly at the speed that is the most efficient for the current altitude.

Edit: IIRC, then one of the convair jets (990?) could cruise at M0.90 or above.

PS, the Concorde and TU 144 were a wee bit faster than the 747. Big grin

[Edited 2004-01-08 13:20:08]

User currently offlineKLM777 From Netherlands, joined Dec 2003, 372 posts, RR: 0
Reply 3, posted (10 years 7 months 2 weeks 4 days 18 hours ago) and read 15734 times:

Hi guys,

It has to do with the upper deck of the 747 (as you probably expected). When flying closer to Mach 1, the smoother cross-section (wing and fuselage) results in less shock waves over the surface of the aircraft (because there is less possibility of small local flows of air reaching speeds of Mach 1 and above).

Because these shock waves create drag, you want to have the least possible amount of shockwaves at your cruise speed. The 747's has less shockwaves at a certain speed than any other airliner, and thus it can cruise faster while not being less economical.

For some more information, see this link:

http://www.aerospaceweb.org/question/performance/q0150a.shtml

Kind regards,

Jeroen

[Edited 2004-01-08 13:32:09]


Every landing is a controlled crash
User currently offlineKilavoud From , joined Dec 1969, posts, RR:
Reply 4, posted (10 years 7 months 2 weeks 4 days 18 hours ago) and read 15656 times:

Tail or head winds are playing a big part in the speed of 747. When I flew Singapore-Zurich end of December, it took this time about 13 hours to cover approx. 10350 km. Over Iran and Turkey we had stron head winds at about 200 km/hour. The speed of our SQ 747-400 was during a while not exceeding 720-740 km/hour.

Cheers. Kilavoud.


User currently offlineUTA_FLYinghigh From Tunisia, joined Oct 2001, 6495 posts, RR: 50
Reply 5, posted (10 years 7 months 2 weeks 4 days 18 hours ago) and read 15640 times:

IMHO the fastest subsonic commercial jet is not the 747 but the Tupolev TU-154, due to its military aircraft wing design :

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Photo © William Ronciere
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Photo © William Ronciere


UTA



Fly to live, live to fly - Air France/KLM Flying Blue Platinum, BMI Diamond Club Gold, Emirates Skywards
User currently offlineKLM777 From Netherlands, joined Dec 2003, 372 posts, RR: 0
Reply 6, posted (10 years 7 months 2 weeks 4 days 18 hours ago) and read 15598 times:

Tail or head winds are playing a big part in the speed of 747.

This is not something unique to the 747 I think. You can add or extract the winds from the airspeed. The 777 will generally fly slower in the same circumstances.

Kind regards,

Jeroen



Every landing is a controlled crash
User currently offlineCedarjet From United Kingdom, joined May 1999, 8086 posts, RR: 54
Reply 7, posted (10 years 7 months 2 weeks 4 days 18 hours ago) and read 15353 times:

The 747 actually used to go faster, until the oil shock in 73. Then they worked out the most efficient cruising speed and flight times got a bit longer.

Headwinds make no difference, it's not as though some planes have a connection to the earth that makes them less affected than other planes.



fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
User currently offlineSllevin From United States of America, joined Jan 2002, 3376 posts, RR: 6
Reply 8, posted (10 years 7 months 2 weeks 4 days 17 hours ago) and read 15250 times:

The 747 goes fast because it was designed to go fast. Actually, Pan Am wanted a Mach .90 cruise, but Boeing argued them down to a .87 compromise -- which certainly contributed the the 747's longevity as gas suddenly because VERY expensive in the 1970s!

Flying an aircraft significantly below its design cruise speed can bring problems of its own. The DC-10, for example, now classically flown at M.82 instead or .84, takes a decided nose-up attitude in cruise flight that makes moving service carts much tougher on the flight attendants (the MD-11 was specifically designed with a low angle of incidence to address this problem, and, having ridden in both planes back-to-back, I can tell you, that 3 degrees nose up makes a BIG difference). There's also drag considerations at some point of flying pitched up that negate the slower speed advantages as well.

In short, modern airliners fly slower because it's more fuel efficient. So the standard for cruise speed has hovered around Mach .82-83 these days.

Steve


User currently offlinePkone From Ireland, joined Dec 2003, 25 posts, RR: 0
Reply 9, posted (10 years 7 months 2 weeks 4 days 17 hours ago) and read 15221 times:

Interesting replies folks...keep'em coming

User currently offlineJustplanesmart From United States of America, joined Mar 2001, 720 posts, RR: 2
Reply 10, posted (10 years 7 months 2 weeks 4 days 17 hours ago) and read 15170 times:

Why is the 747 the fastest (subsonic, or currently in service) commercial jet? Because it was designed to be. The 707 has a wing with 35 degrees sweep back, as does the Convair 880/990, IIRC. The sweep of the 747 wing is 37.5 degrees, and the upper deck creates a bit of area-ruling, as KLM777 explained. In fact, both the 747SP and all 747's with the stretched upper deck have a higher maximum cruising speed than the original due to the area-ruling effect. Of course, none of them fly that fast these days - it's all about fuel economy.


"So many planes; so little time..."
User currently offlinePositive rate From Australia, joined Sep 2001, 2143 posts, RR: 1
Reply 11, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14869 times:

The 727 was also a fast cruiser. It cruised a fair bit faster than the 737, probably more due to its extremely efficient wing than the extra engine. I would say the same for the 747.

User currently offlineDw747400 From United States of America, joined Aug 2001, 1258 posts, RR: 1
Reply 12, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14729 times:

Remember, when the 747 was coming out, the world was thinking fast. SSTs were in development, and everyone figured that they would represent the future. Though the 747 could never really compete for them with speed, it was figured that a faster aircraft could at least contribute to the longevity of the 747 program.

As fuel economy became a greater concern, the speed of aircraft dropped. The 757 and 767 cruise at mach .80, and most of the Airbus wide-bodies fly in a similar speed envelope. With the 777, the speed went back up to .84 (the -300 can cruise at .85) due in large part to more efficient aerodynamics, particularly in the form of advancements in the supercritical wing. Though I haven't seen much recently, I believe Airbus was aiming for .86 with the A380 (they don't like the fact the 777 is faster than their wide-bodies).

The new 7E7 will cruise around .85, though I've heard speculation Boeing might try to push this up a tad to about .87 (just speculation!).

As for the 727 vs. 737, the main reason for the former being faster is that it was intended for longer stage lengths. Engine number is rarely used to increase the speed of an aircraft, especially today with engines able to produce more thrust then a Mercury-Redstone Rocket.



CFI--Certfied Freakin Idiot
User currently offlineStefandotde From , joined Dec 1969, posts, RR:
Reply 13, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14648 times:

So is the 747 the fastest commercial jet or is it the TU 154.
I know that everything from the US is the biggest, fastest, most beautiful and best, etc. but what about the 154 now?


User currently offlineSandiaman From United States of America, joined Nov 2003, 88 posts, RR: 0
Reply 14, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14637 times:

The use of computational fluid dynamics (CFD) has increased our understanding of airfoil performance. Modern day supercritical airfoils offer reduced drag at optimum speeds. Here are some interesting tidbits I've read over time:

-The 777 wing was designed to be as efficient as the 767 wing, but the 777 wing provides a higher optimum cruising speed (M. 0.84 vs M 0.80 for the 767).
-The A380 wing allows the plane to achieve the same optimum cruising speed as the 747 (M. 0.85), but does so with less sweep.
-The 747X planes were design to offer cruising speeds of M0.86-0.87 with minor modifications to the existing wing (note: modern day supercritical airfoils exhibit significant drag increases if they are pushed beyond their optimum speed. So you couldn't "push" the 777 wing like you can the 747 wing)

The ability to achieve higher economic cruising speeds is not only dependent on the wing, but also on the wing-body combination. For example, as JustPlaneSmart stated in Reply #10, part of the reason that the 747 can cruise at higher speeds is that the aircraft’s total cross-sectional area varies less as you move from the front to the back of the plane. This is due in large part to the hump at the front. If the upper deck were extended over the wing, the aircraft’s drag would increase significantly in the transonic regime. In a way, the 747 has a built-in speed advantage with its distinctive hump.

-M


User currently offlineRayChuang From United States of America, joined Jun 2000, 8002 posts, RR: 5
Reply 15, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14627 times:

I believe that the 747-400 nowadays cruises at around Mach 0.85-0.86 for long range cruise. The 777-200 series cruise at around the same speed on longer flights.

This has caused problems with ATC spacing over the north Atlantic routes, where 744's easily outpace 767's, A330's and A340-200/300's flying these routes at around Mach 0.80-0.81. Is it small wonder why the A340-500/600 cruises at around Mach 0.84, and Airbus wants Mach 0.86 cruise speed for the A380-800? This is also the reason why the upcoming Boeing 7E7 will cruise at around Mach 0.85-0.86.


User currently offlineBuslover From Germany, joined Jan 2004, 109 posts, RR: 0
Reply 16, posted (10 years 7 months 2 weeks 4 days 16 hours ago) and read 14536 times:

DW747400 explained it pretty well!

Whenever an airplane is designed, one also has to define the cruise speed and build the wing etc accordingly. On a 737 with - at that time - pretty many short legs and therefore low cruise time the CRZ speed does not matter as much. Meanwhile it also flies on longer legs and the CRZ SPD is a limiting factor concerning flight crew productivity.
E.g. the 340 and 330 were originally designed for fuel conservation and the resulting CRZ SPD was M 0.83, meanwhile the -600 and -500 models have such a long range capability, that a higher CRZ SPD of M .84 makes it possible to fly distance wise longer legs with a 3 men (women) crew, where the use of M .83 might have caused the neccessity of an additional crew member and higher cost.

Different to the 747 (both 200 and 400) a reduction of CRZ SPD when still able to arrive on time is saving considerable amount of fuel. This is practised by all LH crews and saves on the FRA EZE flight using M.83 iso M .84 approximately 4 to 5 tons of fuel! The same procedure on a 747 saves only a negligible amount of fuel.

Dpon't forget it was designed in the late 60ies and the A340 in the very late 80ies.



The best airplane is the one you fly
User currently offlineConcordeBOAC From United Kingdom, joined Nov 2003, 71 posts, RR: 0
Reply 17, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14454 times:

Wasn't the VC-10 the fastest, although not commercialy any more, it still flys.

User currently offlineATA L1011 From United States of America, joined Feb 2001, 1379 posts, RR: 6
Reply 18, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14418 times:

Some things I've seen and heard say the DC-8 and L1011 are faster than the 747, who knows.


Treat others as you expect to be treated!
User currently offlineTomgib From United States of America, joined Nov 2003, 92 posts, RR: 0
Reply 19, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14361 times:

This is one of the most interesting threads I´ve read so far...

If the 747 "hump" makes such a difference, then why don´t other planes have it ?


User currently offlineTavve From Sweden, joined Sep 2003, 172 posts, RR: 0
Reply 20, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14235 times:

Or is it the same with airplanes as it is with boats. The longer it is the faster it will go ...??

No one seems to respond to this question. Does anyone know? For boats it's true (yes, yes, under a thousand restrictions and so on). Can it be that the relationship size/air density is out way wrong?



GOT, that's where I live
User currently offlineOerk From United Kingdom, joined Sep 2003, 162 posts, RR: 0
Reply 21, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14144 times:

Well, just looking at max speeds (not actual speeds) the DC-10 looks pretty nippy!

Tu-154 - Max cruising speed 975km/h, economical cruising speed 900km/h
747-400 - Max cruising speed 939km/h, long range cruising speed 907km/h
DC-10-30 - Max speed 982km/h, cruising speed 908km/h

The terminology and phrases changes here, could someone explain the differences? Especially considering the massively overpowered 757 is slapped down by the lightning like DC-10:

757-200 - Max cruising speed 914km/h, economical cruising speed 850km/h.

I refuse to believe the DC-10 is faster than all these jets - it just doesnt LOOK like a speedy character! Clarification please!


User currently offlineBuslover From Germany, joined Jan 2004, 109 posts, RR: 0
Reply 22, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14022 times:

To Tawe:

Yes it is answered: At the time the 747 was designed speed counted fuel cost was not a factor, every airplane thereafter had to compromise between speed and fuel burn, and therefore was designed for a lower speed.

To Oerk:

Don't take the postcard information, look for the cruise speed published in official documentation, it is always in M - number or IAS, resp. TAS

The 744 is even heavier and if you all remember you aerodynamic lesson right, the heavier an airplane is the faster it has to fly in order to receive the best specific fuel flow.
Also the more headwind --> the faster and vv.



The best airplane is the one you fly
User currently offlineSlamclick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 23, posted (10 years 7 months 2 weeks 4 days 15 hours ago) and read 14018 times:

No quarrel regarding the 747 being the fastest currently carrying passengers. And fastest means highest mach number cruise.

But it needs to be mentioned that the DC-8 actually went supersonic in controlled flight. In 1961 a DC-8 achieved mach 1.012 over Edwards AFB, with an F-104 chase plane confirming the data. The actual plane was subsequently sold to a customer and entered passenger service.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineTeva From France, joined Jan 2001, 1871 posts, RR: 16
Reply 24, posted (10 years 7 months 2 weeks 4 days 14 hours ago) and read 13882 times:

Why is 747 fastest commercial jet?
... Because Concorde is not flying anymore....  Big thumbs up

Teva  Nuts



Ecoute les orgues, Elles jouent pour toi...C'est le requiem pour un con
25 Bahadir : Correct me if I am wrong but 727 is faster than 747 if we are covering only Western built ones.
26 EGGD : I'm pretty sure with the exception of Supersonic Airliners, the CV990 was the fastest commercial aircraft built..
27 Buslover : To EGGD: You are right, the CV 990's design CRZ Mach no was .88 To Bahdir: The 727's speed was .82, the 742 has .84 the 744 has .86
28 Dasheighty : As of right now 1:12 est the history channel is runnning a program on the 747 if you can see it it may answer your questions.
29 RAAFController : Hi All, Putting it simply, design speed is influenced by many factors, one of the most significant being the sweep back angle of the wing. As previous
30 AvObserver : "If the 747 "hump" makes such a difference, then why don´t other planes have it?" The 747's hump wasn't designed to make it go faster; it's there bec
31 Post contains images Mir : Fastest civilian aircarft built these days is Cessna's Citation X, crusies at Mach .92!!!
32 MD-90 : I'm surprised no one mention the Citation X before now, just goes to show how airliner-centric this site is. When I think of area ruling, I think of t
33 Mir : Could someone please explain the concept of area ruling? I'm not exactly sure what it is and what effect it has on the plane.
34 Slamclick : Mir Area rule, oversimplified says that the whole thing should not get thick at the same time. If you could pass a plane (geometry plane not airplane)
35 Mir : Slamclick, thanks very much for the explanation! So, if I understand correctly, the fact that the drop in fuselage area caused by the hump tapering of
36 MD-90 : Here are some cruise speeds from the reference, The International Directory of Civil Aircraft 2001/2002 edition that airliners.net uses for its own ai
37 Skydrol : Interesting data, MD-90. I have heard over and over that Airbus aircraft are 'slow', but never took the time to collect and compare the data as you ha
38 AvObserver : Airbus's designs are not dramatically slower than Boeing's, only slightly so. In the case of the A340, the fact that it shares a common wing design wi
39 Slamclick : Mir You are welcome. But as for the hump on the seven-four, I just don't know that. I'd never before heard that the hump had any effect on the speed o
40 MD-90 : The data for older airplanes tends to emphasize knots, while the newer ones show Mach percentages. I know what you mean about mach being the limiting
41 Mir : As far as I know, there are the typical cruise speeds: 0.92 Citation X (test-flown to .98! WOW!) 0.85 744 0.84 777 0.82 A330/340 0.80 767/757 (sometim
42 L-188 : To get a true answer you would have to find the guy that designed the wing. I suspect that is is the combination of a lot of power and the fact that i
43 Sandiaman : There should be a distinction made between maximum speed and the cruise speed at which the plane can fly most efficiently. The use of area ruling and
44 BOEING747400 : Is the max. speed the same for 744 regardless of engine type or it may vary depending on what engine it has (GE or PW or RR)? What about the 744ER (GE
45 GE : BOEING747400: The max speed of an airliner is the same regardless of engine type (as the wing remains the same). Russell
46 Dw747400 : the fact that it has a 45 degree wing sweep If your talking about the 747, then the sweep at the quarter-chord is actually 37.5 degrees.
47 Ramme : Slamclick: you're correct, the DC8 went past Mach1. Keep in mind that this was reached while the airplane was in a shallow dive.
48 RAAFController : Some further info in response to some posts: Engine power: Remember that one of the basic laws of flight is that thrust = drag, lift equals weight for
49 Thrust : Engine thrust is obviously not a factor, because the 747-100 uses less overall thrust than a 777-300ER, yet was still faster. I will tell you exactly
50 Slamclick : MD90 That is an interesting number, 0.73 for a BAe-146. The ones I flew did not even have a mach meter. We also joked about them getting a descend-onl
51 Dw747400 : Engine thrust is obviously not a factor, because the 747-100 uses less overall thrust than a 777-300ER, yet was still faster. I don't recall the 777-3
52 Slamclick : Okay class, for the last time, forget knots, forget miles per hour, kilometers per hour and furlongs per fortnight. Above all get Groundspeed all the
53 Cicadajet : I believe EL AL took the 747 "supersonic" as well during test flights after the crash in Europe. - Tom
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