Although as we start a new decade, I recall some of the year 2K hubbub- which leaves me mindful of the debate over exactly when a new century starts, and presumably, how to designate decades...BTW, the Royal Observatory also says Jan 1, 2001- but what the heck, we have other things to worry about, so I'll stick with Jan 01, 2010. (Now about Tiger Woods...).
I have to admit some satisfaction with our last thread, in examining why the 787 wings appeared to flex so much (incorrect aspect ratio in some videos resulted in an exaggerated depiction of the radius of curvature), and why they really DO flex so much (higher yield strength x4 aluminum, so only 1/4 as much as used; so despite the fact it is x2 as stiff, structures deflect twice as much (1/4 x 2), roughly (very!) speaking.
What I have less satisfaction with, whether composite airplanes are (or are not) lighter than aluminum airplanes. Which, of course, as an aviation "critic", and "enthusiast", prompted a simple comparison of the 787's nearest stablemates in the Boeing barn, the 767 on the smaller side, and the 777 on the larger side. I have always considered structural efficiency to be measured by empty weight to maximum weight, given other factors being about the same:
* Commercial service (not ruggedized for military operations)
* Pressurized (significant structural stresses involved)
* Jet powered (Similar systems)
* Operating environment (all more or less 35K feet and Mach 0.8-ish)
I had three expectations:
1) A "scaling" effect, that the larger (At least, higher MTOW) an airplane was, the "better" it's structural efficiency would be (empty/MTWO)
2) Newer aircraft would benefit from CAD analysis and be tailored for ultimate structural efficiency, and have superior empty/MTOW ratios
3) Composite airplanes (well, as Baron pointed out, -partially composite) would have better ratios than all aluminum airplanes.
The first expectation was reasonably well met, but the other two pointed to decidedly "disruptive" conclusions! (Now, there is probably a reason for this, but dang if I know what it is...)
Of course, this led to that, and after looking at the 787's nearest family members, I remembered what I have been told about the Boeing 757- that a) it was designed during the energy crunch of the 1970's, and as such, was designed to be unusually light, an as such, included some unusually expensive structural innovations, such as extra lightening holes, etc- whether or not this is true, I'm not sure, but when the 757 was discontinued in favor of the latest and longest versions of the 737, I wondered how much of the purported manufacturing expense savings of going to a "one (737) family" product came from commonality, and how much came from the 757 design itself. So I included the 737 lineup to compare to the 757 versions.
And the 757 was designed to replace the 727, so I looked at it too. Okay, that's a pretty old jet, so how about the other icon-ic (thank you very much!) jet of that era, the 707? How about the extreme of the Boeing product line, the 747, and if that "heavy", how about it's contemporaries, the DC-10 (and MD-11 derivative) and L-1011. How about the other Douglas jets, the DC-9 (and MD-xx derivatives). Not to offend our European friends, how about the Airbus lineup?
And neither would I want to offend our Canadian nor Brazilian friends, especially if the smaller DC-9/MD-95 and 737's are mentioned, the Bombardier CRJ-series and Embraer ERJ-series were included. And then other (original) "regional jet" aircraft were considered- the Fokker 70 and 100, the Dornier 328Jet.
And what the heck, if I looked at DC-9's, why not DC-8's? And how about it's contemporary, the Consolidated Vultee/General Dynamics/Convair series. And if I'm going back to the older jet airliners, why not go ALL the way back, to the Comet?
If considering "unusual" (rare in the US, nowadays, anyway) airliners such as the Convairs, how about the Russian Ilyushins? At this point, I decided just to include every main-stream (even if non-USA) jetliner that I could think (and find in Wikipedia or Airliners.net): the French SUD Caravelle, the British Vickers VC-10 (I've actually seen these in military guise); the Russian Tupolev and Yakovlev, and the British "regional-ish" jet the BAC-111.
And for fun, I included the British/French Concorde and Russian Tu-144 SST's, and the Russian Antonov STOL jet transport. (The STOL outcome was expected, the SST was not).
Anyway, that's the train of thought that led to this compilation.
The weights are pounds, and the the "empty" weight is "operating empty", if I could find it (but the differences usually weren't too great). The radio is Empty/MTOW.
Aviation enthusiasts will recognize the names of these- but just in case we no longer recognize the airplane, Airliners.net/Aircraft-data has a listing of most of these, and there are also generally Wikipedia entries available.
Here's the initial comparison I was curious about, regarding the 767-787-777 comparison:
That was a tasty appetizer, but here's the "main course". The "Top 10" contained some surprises to me- half of them are freighters. (I thought the floor reinforcements, cargo handling equipment, and beef up around the large cargo door cutouts might "outweigh" weight savings obtained from the removal of passenger accommodations and accouterments- but it looks like that is not the case: the "stripped down" freighters are a bit lighter).
The other five "Top 10" finishers included some real surprises too:
The venerable DC-8, grand-daddy of more modern jet "freight dogs", is still showing the kids how it's done. (Well, it did really well in our comparison anyway). First flight of the original DC-8 was on May 30, 1958.
The Concorde SST was certainly not one I would have expected near the top. The rival Tupolev Tu-144 SST did well also, at 0.472 (versus 0.425). The Concorde first flew on March 2, 1969; the Tu-144 first flew on December 31, 1968.
The Boeing 777-200LR was in the top 10 also (as was the 777-Freighter, largely based on the -200LR). I expected the 777 to do well in this comparison- and this is even better than I expected. The first flight of the original 777 was on June 12, 1994.
The Russian Ilyushin IL-62 was a bit of a surprise- firstly, it is Russian, and I think of the stereotype of "rugged" (read: heavy) construction methods. Apparently, this is not (always, anyway) the case- it matched the Airbus A380-800 freighter. It features the funky twin-pod aft-mounted engines (total of 4), similar to the Vickers VC-10 Super of that era, which did well itself (0.468 versus .428). The Ilyushin original version flew in September 1963, the Vickers original version flew on June 29, 1962.
And, the upcoming A350 rounds out this list- although it is still a "paper airplane" (or "paperless airplane", as it is designed with CATIA). And it still hasn't been rolled across a scale- first flight is scheduled for 2012.
|Douglas||MD-95 (717-200) HGW||70790||121000||0.585|