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Should Boeing Had Kept The 747 Wing At 40 Degrees?  
User currently online747400sp From United States of America, joined Aug 2003, 3662 posts, RR: 2
Posted (7 years 6 months 1 week 2 days 19 hours ago) and read 9151 times:

I read some where that Juan Tripp wanted the 747 wing to be swept at 40 degrees, but Boeing talk him into 37 degrees. It was said, that if Boeing did use the 40 degrees wing, the 747 cruising speed would have been around mach 0.87 to 0.88. With a cruising speed like that, the 747 would have been hard to beat. So do you think Boeing should have kept the 40 degrees wings?

39 replies: All unread, showing first 25:
 
User currently offlineCptSpeaking From United States of America, joined Apr 2006, 639 posts, RR: 1
Reply 1, posted (7 years 6 months 1 week 2 days 18 hours ago) and read 9127 times:

Depends...there are pros and cons to everything. Does your source mention why Boeing wanted the 37 degrees? It seems to me that if the pros outweighed the cons, then Boeing wouldn't have made the choice they did. I'm curious myself, I just don't think we've heard the whole story...

Your CptSpeaking



...and don't call me Shirley!!
User currently offlineArniePie From Belgium, joined Aug 2005, 1265 posts, RR: 1
Reply 2, posted (7 years 6 months 1 week 2 days 5 hours ago) and read 9006 times:

Isn't a wing with 40° sweep more unstable specifically on approach (CitationX comes to mind as an example)?
Also you might need a higher Approach and landing speed combined with a higher TO speed which can than lead to reaching max ground speed for the tyres too quickly etc... .

As stated in previous answer probably just a compromise



[edit post]
User currently offlineKeta From Germany, joined Mar 2005, 448 posts, RR: 0
Reply 3, posted (7 years 6 months 1 week 2 days 5 hours ago) and read 8973 times:

The 40º sweep would have meant more cruise speed, but it would have introduced problems too, as stated, like more weight, etc. I'm afraid fuel consumption would be somewhat higher too, and with the increase of oil prices that happened on the decade of the 70's, I would say it was actually a luck for Boeing to have chosen the 37 degree sweep. The 747 would have been hard to beat, but only speed-wise, which is not the most important part for an airliner.


Where there's a will, there's a way
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 4, posted (7 years 6 months 1 week 2 days 4 hours ago) and read 8939 times:

Quoting 747400sp (Thread starter):
With a cruising speed like that, the 747 would have been hard to beat.

Instead of the commercial failure it turned out to be?



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 5, posted (7 years 6 months 1 week 2 days 3 hours ago) and read 8894 times:

From what I read about Juan Tripp, he was a business man, not and aeronautical engineer. His input into the 747 was to say he would buy them if Boeing would design and built them.

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6480 posts, RR: 54
Reply 6, posted (7 years 6 months 1 week 2 days ago) and read 8804 times:

The advantages of reduced wing sweep are:
- reduced structure weight
- improved fuel efficiency
- improved runway performance
- improved payload capability at hot and high ops.

The disadvantage is lower maximum cruise speed.

It's a trade off, a compromise. Everything on airliners are compromises.

Reducing the 747 wing sweep is totally in line with the current trend. Airlines don't sell speed any longer. They did that fifty years ago when airliners changed name from DC-4 over DC-6, DC-7 to DC-8. But those days are long time gone.

One decimal point on the cruise Mach number doesn't impress an airline manager these days if it means 100nm reduced range and five dollars extra fuel burn per pax on a long range flight. Plus slightly increased wear on wheels and brakes.

If airlines were selling speed, then the first thing they would do would be to reduce the rediculous check-in queues and demand (and pay for) their major hub airports to reduce the similar security queues. That way they could reduce total travel time to the same level as passengers were used to back in the 70'es and 80'es.

But that won't happen. Travel times seem to continue to increase year by year.



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineZeke From Hong Kong, joined Dec 2006, 9149 posts, RR: 76
Reply 7, posted (7 years 6 months 1 week 1 day 23 hours ago) and read 8771 times:

Quoting Prebennorholm (Reply 6):
The advantages of reduced wing sweep are:
- reduced structure weight
- improved fuel efficiency
- improved runway performance
- improved payload capability at hot and high ops.

With the supercritical aerofoils like used on the 777 and 380, one does not need as much sweep as on the 744 to avoid a large wave drag increase.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 6 months 1 week 18 hours ago) and read 8529 times:

Actually even with the 37.5 degree sweep the 747 is able to do mach 0.88 during a high-speed cruise despite the fact that it often flies slower. The reason lower speeds are selected is to reduce fuel-consumption.

Andrea Kent


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 9, posted (7 years 6 months 1 week 18 hours ago) and read 8516 times:

Great point, Zeke.

All things equal, CFD (computational fluid dynamics) has produced consistent Mach .80-.86 range across the spectrum of current airliners, with less wing sweep, which provides advantages mentioned such as increased runway performance, less wing structure/build cost, and bending moments... at about the same Mach #s. The trend, until we have a quantum leap above even the Genx/Trent 1000 motors, is for wing sweep to decrease...


User currently online747400sp From United States of America, joined Aug 2003, 3662 posts, RR: 2
Reply 10, posted (7 years 6 months 1 week 17 hours ago) and read 8509 times:

Quoting Zeke (Reply 7):
With the supercritical aerofoils like used on the 777 and 380, one does not need as much sweep as on the 744 to avoid a large wave drag increase.

Is the 747-8 going to have it's wing sweep less that earlier model of 747?


User currently offlineSCAT15F From United States of America, joined Feb 2007, 402 posts, RR: 0
Reply 11, posted (7 years 6 months 1 week 16 hours ago) and read 8488 times:

Quoting 747400sp (Reply 10):
Is the 747-8 going to have it's wing sweep less that earlier model of 747?

The 748 wing is going to be the same 37.5 degree sweep as far as I know (the wing will be re-lofted to make it supercritical but the planform will be the same)


User currently offlineDw747400 From United States of America, joined Aug 2001, 1260 posts, RR: 1
Reply 12, posted (7 years 6 months 1 week 7 hours ago) and read 8411 times:

Quoting Blackbird (Reply 8):
Actually even with the 37.5 degree sweep the 747 is able to do mach 0.88 during a high-speed cruise

VC-25As routinely cruise at mach 0.90, so form a purely aerodynamic standpoint the wing isn't the limiting factor. As you said, the fuel consumption is the major issue.



CFI--Certfied Freakin Idiot
User currently offlineMax Q From United States of America, joined May 2001, 4643 posts, RR: 19
Reply 13, posted (7 years 6 months 1 week 3 hours ago) and read 8373 times:

Actually, Trippe wanted a sweep of 40 Degrees for the 747 and Boeing wanted 35, they compromised exactly in the middle at 37.5 degrees !


The best contribution to safety is a competent Pilot.
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 14, posted (7 years 6 months 1 week 2 hours ago) and read 8329 times:

To Dw747400,

Technically the 747 can fly safely up to Mach 0.92 (barber pole), of course fuel consumption would be rather high. The 747-SP occasionally did this, but it was a lighter design with nearly the same thrust so it wasn't as fuel thirsty.


Max Q, that is actually correct.

You have to keep in mind, PanAm had engineers of their own on staff for consulting should they need a new airplane from what I remember. And for a Mach 0.88 cruise, they felt a 40-degree sweep would be necessary to get the job done. Boeing wanted a 35-degree sweep because it would enable a greater span for the same area (aspect ratio), better low-speed performance, lighter structural weight, less extreme dutch-roll tendencies. So they compromised at 37.5 degrees sweepback.

As an interesting note... the DC-8 selected a 30-degree sweepback even though they knew 35-degrees would get them superior performance for high-speed according to their estimates, but because they wanted low-speed handling traits that would be closer to the DC-7's, particularly at high-flap settings for approach, I'm not sure if dutch roll was a factor, although a 30-degree sweepback would almost certainly have a lower-dutch roll tendency than a 35-degree wing. Ultimately they managed to get a airfoil-design that would achieve virtually the same high-speed performance of the 35-degree sweep, and provide the same performance of a 30-degree wing at low-speed, and probably the dutch roll characteristics of a 30-degree sweepback. Luckily they managed to get the best of both worlds. When Douglas scaled up it's design to meet Juan Trippe's desire for a 6-abreast plane, the tail was swept back 35-degrees to reduce drag, and wing area was increased substantially to hold the longer, wider fuselage, although the wing-sweep stayed about the same. The DC-8 was capable of virtually the same cruise speeds as the 707.


Andrea Kent


User currently offlineZBBYLW From Canada, joined Nov 2006, 1986 posts, RR: 6
Reply 15, posted (7 years 6 months 1 week 2 hours ago) and read 8324 times:

Quoting Dw747400 (Reply 12):
VC-25As routinely cruise at mach 0.90, so form a purely aerodynamic standpoint the wing isn't the limiting factor. As you said, the fuel consumption is the major issue.

When I flew on the last AC 744 flight FRA-YYZ in 2004, I remember the Captain telling me that occasionally they flew mach 0.91 when late on an inbound flight. They figured that the additional costs of trying to find new flights/hotels and what not for those inconvenienced outweighed the extra fuel costs. On a side note we were 1h30 mins late leaving FRA and arrived a few minutes early in YYZ, after talking to the pilot her was cruising around for a good majority of the flight in the .88-.90 range. One down side however he explained that the air was actually supersonic over parts of the wing, leaving a slightly rougher ride.



Keep the shinny side up!
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 6 months 1 week 2 hours ago) and read 8313 times:

Many good points and information here. However, don't forget that in the 1960s, speed was everything, so it made sense to design the 747 wing for high speed operations.

But then October 1973 came around, and things began to change...


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 17, posted (7 years 6 months 1 week 1 hour ago) and read 8293 times:

Quoting N231YE (Reply 16):
However, don't forget that in the 1960s, speed was everything, so it made sense to design the 747 wing for high speed operations.

The point being that CFD allows contemporary designs to have the same speeds with less sweep...


User currently offlineSilverComet From Mauritius, joined Apr 2007, 85 posts, RR: 0
Reply 18, posted (7 years 6 months 1 week ago) and read 8289 times:

How hard would it be to have a swing wing design on an airliner?

User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 19, posted (7 years 6 months 6 days 23 hours ago) and read 8268 times:

Quoting EssentialPowr (Reply 17):
The point being that CFD allows contemporary designs to have the same speeds with less sweep...

My apologies...did not realize that. I was thinking that newer airliners have less sweep at a cost of less speed (efficiency matters more than speed, contrary to the 1960s).

I think I remember reading the 777 is actually one of the fastest, if not the fastest civilian aircraft today, thanks to a well-engineered wing...if that is true, then I see the connection: CFD would allow the 777 to be extremely cost efficient, one of the 777 program's driving forces, yet also have a high speed.


User currently offlineZkpilot From New Zealand, joined Mar 2006, 4840 posts, RR: 9
Reply 20, posted (7 years 6 months 6 days 23 hours ago) and read 8241 times:

Quoting N231YE (Reply 19):
I think I remember reading the 777 is actually one of the fastest, if not the fastest civilian aircraft today, thanks to a well-engineered wing...if that is true, then I see the connection: CFD would allow the 777 to be extremely cost efficient, one of the 777 program's driving forces, yet also have a high speed.

The Queen of the Skies - 747 still holds that title, but the 777 is very close and uses less fuel at the same time. On a long flight 12hours+ (eg LAX-MEL, LAX-AKL etc) the difference can add up to a small but substantial amount of time.
My understanding of the 748I is that it will infact be M0.01 slower than the 744... anyone else out there know about/care to comment about this?  Smile



56 types. 38 countries. 24 airlines.
User currently offlineLTU932 From Germany, joined Jan 2006, 13864 posts, RR: 50
Reply 21, posted (7 years 6 months 6 days 20 hours ago) and read 8212 times:

Quoting Zkpilot (Reply 20):
The Queen of the Skies - 747 still holds that title, but the 777 is very close and uses less fuel at the same time. On a long flight 12hours+ (eg LAX-MEL, LAX-AKL etc) the difference can add up to a small but substantial amount of time.
My understanding of the 748I is that it will infact be M0.01 slower than the 744... anyone else out there know about/care to comment about this?

I thought the 747-8 will actually be Mach 0.01 faster than the 744.


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 22, posted (7 years 6 months 6 days 19 hours ago) and read 8193 times:

You know Mach 0.01 is only about 6.6 miles an hour @ 35,000 feet. It's not a major difference unless you're flying over an obsecene distance.

Andrea Kent


User currently online747400sp From United States of America, joined Aug 2003, 3662 posts, RR: 2
Reply 23, posted (7 years 6 months 6 days 17 hours ago) and read 8174 times:

Quoting ZBBYLW (Reply 15):
One down side however he explained that the air was actually supersonic over parts of the wing, leaving a slightly rougher ride.

My father was told, that during alot of there military charter flight, Flying Tiger would fly there 747s at full speed and they were pretty bumply ride.


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 24, posted (7 years 6 months 6 days 17 hours ago) and read 8172 times:

Quoting N231YE (Reply 19):
...if that is true, then I see the connection: CFD would allow the 777 to be extremely cost efficient, one of the 777 program's driving forces, yet also have a high speed.

That is exactly right. The 777 is almost as fast as the 747 with less wing sweep, but has the aforementioned benefits of a "straighter" wing as well...


25 BAe146QT : I doubt it would be impossible, (though imagine rotating engine pylons!!!), but think about the problems that a swing-wing* is designed to solve. Com
26 Speedracer1407 : To add to BA3-146QT's response, consider the fact that everything on a modern airliner is optimised for greatest efficiency within fairly narrow rang
27 Post contains images SilverComet : Yes I can easily imagine the complexity and weight penalty involved in rotating engine pylons for wing mounted engines. But I was thinking more along
28 Legoguy : Out of interest, what are the wing sweep of the following aircraft... Boeing 757 / 757 / 747 and the Airbus A330 / (A345 + A346) I know Airbus prefers
29 SCAT15F : Doesn't the MD-11/DC-10 have a really sharp sweepback? almost the same (if not the same) as the 747?
30 Blackbird : At Mach 0.88 the 747 has supersonic flow over parts of the wing? Or is that above Mach 0.88? Regarding the MD-11 and DC-10, they have 35-degree sweepb
31 Starlionblue : Huge weight and space penalties. Even military designers abandoned the concept years ago due to this. Wing technology which negated the need for vari
32 SEPilot : I was under the impression that the high-speed aerodynamics of the DC-8 were never as good as the 707, which is why Juan Trippe never ordered another
33 EssentialPowr : What you are referring to is called "supercriticality" and it is common on contemporary jet wing designs for some local flow to be supersonic even at
34 Starlionblue : Of course in some cases the cost and complexity is justified. But a new F-14 (F/A-18 and F-35 for example) does not have a swing wing. Agreed. It's a
35 EssentialPowr : And neither do those a/c have the range/MGTOW/top speed combination of the F14, to include the -18E/F. In fact, one of the many gripes about the F18
36 Blackbird : Actually, I said "virtually the same" not "the same" regarding the DC-8's speed. I think the DC-8's problems weren't because it was slightly slower, i
37 SEPilot : It was my understanding (much of which comes from "The Road to the 707" written by one of the engineers involved) that because of the fact that Boein
38 Blackbird : I did not know that Douglas did not have a high-subsonic/transonic tunnel of it's own. Andrea Kent
39 SEPilot : They didn't in the 50's; they had to rent time in the NACA tunnel. I don't know if they built one later; I doubt it due to the financial uncertaintie
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