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747-200 Cruise Speed  
User currently offlinelexkid12300 From United States of America, joined Mar 2011, 89 posts, RR: 0
Posted (2 years 6 months 4 weeks 10 hours ago) and read 14131 times:

Hey guys,

I monitor flightaware quite often and seem to notice that the 747-200 (although quite rare) seems to always be the fastest airliner on there, often pushing a ground speed of 780mph!

I monitor the Northeast Region of the USA, watching planes heading east towards Europe. I know planes heading in this direction have a higher ground speed due to the winds, but why is it that at any given time, if there's a 747-200 (usually with Kalitta Air) in this area, it's always going QUITE faster than anything on the same route.

Just to make sure i wasn't crazy, i tracked many 747-400 Cargo flights traveling the same routes and they never seem to reach speeds as high as when the flights are operated by a 747-200.

Is there something about the 747-200 that makes it faster than the 747-400 counterpart? Is a ground speed of 780mph normal for this plane? I swear, when there's a 747-200 in flight, there isn't a single plane around it reaching the same speed.

Thanks for the input!

21 replies: All unread, jump to last
 
User currently offlineCitationJet From United States of America, joined Mar 2003, 2439 posts, RR: 3
Reply 1, posted (2 years 6 months 4 weeks 7 hours ago) and read 14072 times:

Quoting lexkid12300 (Thread starter):
Is a ground speed of 780mph normal for this plane?

The highest ground speed for a 747-200 documented by photo is 701 kts.
http://www.groundspeedrecords.com/records/record%20B742%20701kts.html

The highest ground speed for a 747-400 documented by photo is 752 kts. This is the highest ground speed of all commercial and business aircraft listed, with the exception of Concorde.
http://www.groundspeedrecords.com/records/record%20B744%20752kts.htm

.



Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
User currently offlineMax Q From United States of America, joined May 2001, 4550 posts, RR: 19
Reply 2, posted (2 years 6 months 4 weeks 5 hours ago) and read 14022 times:

Well, I had a groundspeed of 701 knots in my B757 eastbound over the Atlantic one night. 230 knot plus tailwind.



As for the 742 being so fast, you would be better off talking to B747FE as he is the expert on the subject but I don't think it's cruise mach is higher than the -400's.


What you may be seeing (in conjunction with a strong tailwind) is this operator cruising faster than normal to get 'the goods to market on time'



The best contribution to safety is a competent Pilot.
User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 3, posted (2 years 6 months 4 weeks 3 hours ago) and read 14004 times:

Your observed (probably not economical) speeds are probably flown, because the aircraft is running behind schedule , to catch up or it has to arrive before a certain time (airport closure or airport noise restictions).

Theoretically the 747 classic series can be flown with the fastest (cruise) speed (VMO). Max. mach number (MMO) is the same on the classic and -400 series, but lower on the new 747-8 series.
However, each individual airframe has a different actual speed limit, caused by the difference in activation of the max. airspeed clicker.

The max. certified speed (VMO) is at the 747 classic series (incl. -SP) is 375 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747- 400 series (incl. -400D) is 365 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747-8 series is 365 kts, MMO is 0.90

I also have past the 700 kts GS mark actually at the 747 classic series a few times, at the Tokyo - Anchorage run, an area known for very high wind velocities.

[Edited 2012-03-05 23:47:56]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineMax Q From United States of America, joined May 2001, 4550 posts, RR: 19
Reply 4, posted (2 years 6 months 4 weeks 3 hours ago) and read 13985 times:

Quoting 747classic (Reply 3):


Your observed (probably not economical) speeds are probably flown, because the aircraft is running behind schedule , to catch up or it has to arrive before a certain time (airport closure or airport noise restictions).

Theoretically the 747 classic series can be flown with the fastest (cruise) speed (VMO). Max. mach number (MMO) is the same on the classic and -400 series, but lower on the new 747-8 series.
However, each individual airframe has a different actual speed limit, caused by the difference in activation of the max. airspeed clicker.

The max. certified speed (VMO) is at the 747 classic series (incl. -SP) is 375 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747- 400 series (incl. -400D) is 365 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747-8 series is 365 kts, MMO is 0.90

I also have past the 700 kts GS mark actually at the 747 classic series a few times, at the Tokyo - Anchorage run, an area known for very high wind velocities.



I meant to include your expertise as well 747Classic.

Just curious as to why MMO on the 747-8 is lower ?



Cheers

[Edited 2012-03-06 00:25:20]


The best contribution to safety is a competent Pilot.
User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 5, posted (2 years 6 months 3 weeks 6 days 23 hours ago) and read 13939 times:

Quoting Max Q (Reply 4):
Just curious as to why MMO on the 747-8 is lower ?

Re-lofted wing, to obtain a L/D (lift drag ) improvement to obtain a payload/range increase for the 747-8 series, despite the increased drag of the (larger) GEnx-2B engines.

Only the structural arrangement of the wing box stayed the same, to avoid new certification tests. (the 747-8 is still a derivative aircraft - no new static/fatique tests necessary).

Aerodynamically the 747-8 wing is however a complete different wing than the one installed at the previous 747 series.



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offline113312 From United States of America, joined Apr 2005, 572 posts, RR: 1
Reply 6, posted (2 years 6 months 3 weeks 6 days 17 hours ago) and read 13786 times:

At typical weights for a freighter, an economical cruise speed for a Classic 747 is Mach .85. B777 and A380 also can cruise at this speed. Mach .86 or .87 would not be unreasonable for the 747 although some operators might make a case for slower. On oceanic tracks, constant Mach clearances of Mach .82 to .84 might be assigned to most widebody traffic.

User currently offlinelexkid12300 From United States of America, joined Mar 2011, 89 posts, RR: 0
Reply 7, posted (2 years 6 months 3 weeks 6 days 7 hours ago) and read 13622 times:

747classic- why is it that the 747 classics have a faster cruise speed? Is it due to the engines or aerodynamics? Or simply by operator choice?

Here's a Kalitta 747-200 that flew EWR-LGG on March 4th.

http://flightaware.com/live/flight/C...9/history/20120304/2300Z/KEWR/EBLG

According to flightaware, the ground speed reached 783mph for several minutes (7:28pm), reached 794mph (8:09pm) and settled at 771mph for over an hour. I know some of these "spikes" might be errors, but if you look at the time from takeoff to landing, it's a good 1/2 hour quicker than many other days for that flight. This flight did leave a half hour late, and it arrived a minute early!

I suppose it could be from operators trying to make it on time, but it still doesn't explain why none of the 747-400 cargo flights reach the same speeds...


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17054 posts, RR: 67
Reply 8, posted (2 years 6 months 3 weeks 6 days 7 hours ago) and read 13610 times:

Quoting lexkid12300 (Reply 7):
747classic- why is it that the 747 classics have a faster cruise speed? Is it due to the engines or aerodynamics? Or simply by operator choice?

Answered in reply 5.

Quoting lexkid12300 (Reply 7):
According to flightaware, the ground speed reached 783mph for several minutes (7:28pm), reached 794mph (8:09pm) and settled at 771mph for over an hour. I know some of these "spikes" might be errors, but if you look at the time from takeoff to landing, it's a good 1/2 hour quicker than many other days for that flight. This flight did leave a half hour late, and it arrived a minute early!

Groundspeed is highly dependent on winds and is not a true measure of cruising airspeeds.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinelexkid12300 From United States of America, joined Mar 2011, 89 posts, RR: 0
Reply 9, posted (2 years 6 months 3 weeks 6 days 7 hours ago) and read 13607 times:

Quoting Starlionblue (Reply 8):
Quoting lexkid12300 (Reply 7):
747classic- why is it that the 747 classics have a faster cruise speed? Is it due to the engines or aerodynamics? Or simply by operator choice?

Answered in reply 5.

Quoting lexkid12300 (Reply 7):
According to flightaware, the ground speed reached 783mph for several minutes (7:28pm), reached 794mph (8:09pm) and settled at 771mph for over an hour. I know some of these "spikes" might be errors, but if you look at the time from takeoff to landing, it's a good 1/2 hour quicker than many other days for that flight. This flight did leave a half hour late, and it arrived a minute early!

Groundspeed is highly dependent on winds and is not a true measure of cruising airspeeds.

I don't see anything stating why the -200 would have a faster cruise speed compared to the -400. I did hear however that the -8 was supposed to be the fastest 747...
http://www.prnewswire.com/news-relea...nental-vip-airplane-140752403.html

And i know the ground speed depends on the winds, but it still doesn't explain why whenever there's a 747-200 heading NE off the New England coast, adjacent planes have a much smaller ground speed. There is definitely something inherent about the -200 that allows it to go faster.


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6895 posts, RR: 76
Reply 10, posted (2 years 6 months 3 weeks 6 days 6 hours ago) and read 13598 times:

Quoting lexkid12300 (Reply 9):
And i know the ground speed depends on the winds, but it still doesn't explain why whenever there's a 747-200 heading NE off the New England coast, adjacent planes have a much smaller ground speed. There is definitely something inherent about the -200 that allows it to go faster.

True Airspeed depends on temperature and altitude for a given mach number. Generally, the lower you go the faster the true airspeed is for the same mach number.
Winds also vary with altitude... it's not always faster the higher you go, especially in a jetstream.
Now, It goes to EBLG? Hmmm...

Quoting lexkid12300 (Reply 7):
but if you look at the time from takeoff to landing, it's a good 1/2 hour quicker than many other days for that flight.

Reading that, makes me ask, did you compare that flight with 747-400 flights (freighters? or any?) on EWR-LGG?
Airport congestion anyone? I think one can leave EWR at the same time and land in LGG before you do on LHR or LGW!

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinedon From Japan, joined Jun 2003, 274 posts, RR: 0
Reply 11, posted (2 years 6 months 3 weeks 6 days 6 hours ago) and read 13596 times:

The usual cruising mach speeds for 747 family at JAL (when they used to operate 747s):

-200 : .84
-300 : .85
-400 : .86

But sometimes the cruising speed is dependent on the happy hour schedule of the post-flight debriefing location at the destination 


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17054 posts, RR: 67
Reply 12, posted (2 years 6 months 3 weeks 6 days 6 hours ago) and read 13595 times:

Quoting lexkid12300 (Reply 9):
I don't see anything stating why the -200 would have a faster cruise speed compared to the -400. I did hear however that the -8 was supposed to be the fastest 747...

Ah sorry. Reply 3 does state that the max certified speeds are the same though. Then again perhaps cruise is different.

Quoting 747classic (Reply 3):
The max. certified speed (VMO) is at the 747 classic series (incl. -SP) is 375 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747- 400 series (incl. -400D) is 365 kts, MMO = 0.92
The max. certified speed (VMO) is at all 747-8 series is 365 kts, MMO is 0.90



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 13, posted (2 years 6 months 1 week 2 days 22 hours ago) and read 12729 times:

As stated before the Indicated airspeed (IAS) limit for the 747 classic series is the highest available (375 kts). For the 744 this speed is slightly lower (365 kts), the probable cause of the lower limiting speed is the (slightly) increased wingspan plus the installed winglets.

This limiting IAS can only be flown at relative low altitudes and will translate in the highest possible True Airspeed (corrected for temp. and altitude).
At the usable cruising flight levels the mach number is the limiting factor (MMO) and this limit is exactly the same for the classic and 400 series.

The only cause I can give for the observed higher speeds flown by the classic 747's is the fact that they are actually operated manually (no Auto Throttle) just below the mach/airspeed warning. (triggered just below VMO/MMO)

This is possible when operating with (PMS) A/T off (fixed PWR lever position) and alt hold on. This is possible due the increased drag at that high speed and conseq. very high speed stability. No frequent pwr lever changes are needed. In fact it's the old way of 747 cruise flight, without full flight regime auto throttle systems(FFRATS), before the PMS and FMC were available.

At the newer 747-400 (and also the -8) series, always the FFRATS is active (SOP) and the FMC doesn't allow flying that close to the speed limit.



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlinegeorgiaame From United States of America, joined Aug 2005, 982 posts, RR: 6
Reply 14, posted (2 years 6 months 5 days 21 hours ago) and read 12392 times:

Quoting 747classic (Reply 5):
Aerodynamically the 747-8 wing is however a complete different wing than the one installed at the previous 747 series.

Is there any way that you can begin to explain to a complete, non engineer layman, what make this new wing "completely different" from the one on the -400? How does the airfoil change, and where, thickness/depth/length changes. (Obviously, I don't seem to know a cord from a span, and so on). Much appreciated, this has been bugging me for ages!



"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 15, posted (2 years 6 months 5 days 14 hours ago) and read 12315 times:

Is it possible, that 747 classics do have a higher "best economy" speed? That is, it takes the least amount of fuel per airmile flown.
It might be then better in terms of economy to let 742s fly faster.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 16, posted (2 years 6 months 5 days 6 hours ago) and read 12237 times:

Quoting georgiaame (Reply 14):
Is there any way that you can begin to explain to a complete, non engineer layman, what make this new wing "completely different" from the one on the -400?

The 747-400 uses the same set of airfoils as the original 747, which predated the adoption of the supercritical airfoil.

The original 747 airfoil looks something like this:


The 747-8 uses a supercritical airfoil...it's deeper (thicker) and flatter on top:


Other changes include:
-The loft (the way the wing twists and how the airfoil sections blend together is different)
-The gauge (the thickness and material of the wing parts changed)
-The flaps are simpler (one less slot for each flap) and have a different movement path
-The Krueger flaps along the leading edge have a different profile
-The outboard spoilers and ailerons are fly-by-wire rather than cable controlled, which allows the ailerons to droop for improved flap-like performance (along with other functions)
-The winglet was replaced by a raked wingtip

http://worldofaircraftdesign.files.wordpress.com/2011/08/747-8-wing-design.jpg

Tom.


User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 17, posted (2 years 6 months 5 days 3 hours ago) and read 12199 times:

Tdscanuck reply covered the highlights of the wing changes of the 747-8 series.

The benefits of the new (super-critical) 747-8 wing are :

- Lift/drag improvement.
- The thicker wing addressed the fuel volume limit on the earlier 747 series (more fuel can be carried inside the wing.)

Additional the winglets of the 400 series are replaced by more efficient raked wingtips, already installed at the 764, later 777 series and the 787.

To keep the costs within limits the following criteria had also to be satisfied :
- structural wing box/center wing box arrangement stayed the same (except for increased gauge), to avoid new static and fatigue wing testing - derivative aircraft)
- existing wing tooling had to be used (after small modifications),

Most of the other changes at the secondary flight controls are necessary to lower the community noise :
- dual inboard flaps and single outboard flaps iso the original triple slotted TE flaps.

The new gapped krueger LE flaps are installed to offset the loss in low speed handling caused by the single outboard flap arrangement)

In fact the 747-8 wing has a structural identical, beefed up, internal wing structure. The outer structure (wing profile) has been changed into a new super crititical airfoil to address the shortcomings of the wing of the 747 series up to and incl. the -400 series, designed in the sixties.

[Edited 2012-03-29 01:39:04]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlinegeorgiaame From United States of America, joined Aug 2005, 982 posts, RR: 6
Reply 18, posted (2 years 6 months 4 days 21 hours ago) and read 12146 times:

Believe it or not, I do (sort-of) understand the concept of the super-critical wing, and have actually had the pleasure of watching supersonic shock waves forming on the winds of 757 aircraft. (I'm still getting heartburn trying to understand the entire concept of a shock wave, much less the visual distortion they produce when light passes through it...) So basically, the new wing is thinner, flatter on top, deeper curve on the underside toward the trailing edge, somewhat different vertical cross sections moving out from the fuselage toward the wingtips when compared to the old wing, and some fancy new stuff leading and trailing edges. If my understanding is wrong, take faith that I'm not looking for job in aeronautical engineering anyway. Thanks for the info!


"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 19, posted (2 years 6 months 4 days 19 hours ago) and read 12119 times:

Quoting georgiaame (Reply 18):

Correct summary, only the new super-critical wing is thicker, not thinner.

[Edited 2012-03-29 08:56:16]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently online747classic From Netherlands, joined Aug 2009, 2153 posts, RR: 14
Reply 20, posted (2 years 6 months 3 days 21 hours ago) and read 11970 times:

Here the actual 747-8 supercritical wing profile is clearly shown.
Looking at the outerwing section, where the connection to the raked wingtip is made.

Original uploaded by flightblogger, see for other sizes : http://www.flickr.com/photos/flightb...502664585/in/set-72157617712427170

More interesting pictures of the actual 747-8 wing assembly can be seen here :
http://www.flickr.com/photos/flightblogger/sets/72157617712427170/



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlinegeorgiaame From United States of America, joined Aug 2005, 982 posts, RR: 6
Reply 21, posted (2 years 5 months 4 weeks 22 hours ago) and read 11644 times:

Great picture - the only thing that would make it better would be to have the equivalent section of say, a 707 wing juxtaposed with this view. I suspect the leading edge would be "blunter", and the "indentation" on the trailing underside would be missing. Big surprise was to learn that the s.c. wing is actually thicker than the "standard". Looking at diagrams and pictures of the newer planes, esp. the 787, it really looks like just the opposite. Nice teaching model, however! Once again, thanks!


"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
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