Editing Boeing 747 (section)

=== Proposed variants ===
Boeing studied a number of 747 variants that did not advance beyond the concept stage.

==== 747 trijet ====
During the late 1960s and early 1970s, Boeing studied the development of a shorter 747 with [[trijet|three engines]], to compete with the smaller Lockheed L-1011 TriStar and McDonnell Douglas DC-10. The center engine would have been fitted in the tail with an [[S-duct]] intake similar to the L-1011's. Overall, the 747 trijet would have had more payload, range, and passenger capacity than either of the two other aircraft. However, engineering studies showed that a major redesign of the 747 wing would be necessary. Maintaining the same 747 handling characteristics would be important to minimize pilot retraining. Boeing decided instead to pursue a shortened four-engine 747, resulting in the 747SP.<ref>Jenkins 2000, pp. 69–71.</ref>

==== 747-500 ====
In January 1986, Boeing outlined preliminary studies to build a larger, ultra-long haul version named the {{not a typo|747-500}}, which would enter service in the mid- to late-1990s. The aircraft derivative would use engines evolved from unducted fan (UDF) ([[propfan]]) technology by [[General Electric]], but the engines would have shrouds, sport a [[bypass ratio]] of 15–20, and have a propfan diameter of {{Convert|10–12|ft|abbr=out}}.<ref name="BiggerJumbos">{{Cite news |date=January 15, 1986 |title=Boeing plans propfan engines for bigger jumbos in 1990s |page=1 |work=[[Financial Times]] |issue=29829 |location=Singapore |format=PDF |url=https://archive.org/stream/FinancialTimes1986UKEnglish/Jan%2015%201986%2C%20Financial%20Times%2C%20%2329829%2C%20UK%20%28en%29#page/n0 |given=Chris |surname=Sherwell}}</ref> The aircraft would be stretched (including the upper deck section) to a capacity of 500 seats, have a new wing to reduce drag, cruise at a faster speed to reduce flight times, and have a range of at least {{convert|10000|mi|nmi km|abbr=on|disp=out}}, which would allow airlines to fly nonstop between [[Heathrow Airport|London, UK]] and [[Sydney Airport|Sydney, Australia]].<ref name="LondonSydney">{{Cite news |date=January 20, 1986 |title=Fly London to Sydney...non-stop |page=5 |work=[[Financial Times]] |issue=29833 |department=Technology |format=PDF |url=https://archive.org/stream/FinancialTimes1986UKEnglish/Jan%2020%201986,%20Financial%20Times,%20%2329833,%20UK%20(en)#page/n4 |given=Michael |surname=Donne}}</ref> <!-- The Propfan powered Boeing 747 never made it to the production stage. -->

==== 747 ASB ====
Boeing announced the 747 ASB (''Advanced Short Body'') in 1986 as a response to the Airbus A340 and the [[McDonnell Douglas MD-11]]. This aircraft design would have combined the advanced technology used on the 747-400 with the foreshortened 747SP fuselage. The aircraft was to carry 295 passengers over a range of {{Convert|8000|nmi|abbr=on}}.<ref>{{Cite news |date=June 7, 1986 |title=Boeing offers 747ASB |work=Flight International |url=http://www.flightglobal.com/FlightPDFArchive/1986/1986%20-%201260.PDF |url-status=live |access-date=October 6, 2012 |archive-url=https://ghostarchive.org/archive/20221009/http://www.flightglobal.com/FlightPDFArchive/1986/1986%20-%201260.PDF |archive-date=October 9, 2022}}</ref> However, airlines were not interested in the project and it was canceled later that year.

==== 747-500X, -600X, and -700X ====
[[File:Boeing 747-500X and 747-600X comparison line drawing.jpg|thumb|The proposed 747-500X and -600X as depicted in a 1998 [[Federal Aviation Administration|FAA]] illustration|alt=Aircraft comparison diagram.]]

Boeing announced the 747-500X and -600X at the 1996 [[Farnborough Airshow]].<ref name="boe_1996" /> The proposed models would have combined the 747's fuselage with a new wing spanning {{Convert|251|ft|m|abbr=out}} derived from the 777. Other changes included adding more powerful engines and increasing the number of tires from two to four on the nose landing gear and from 16 to 20 on the main landing gear.<ref name="faa_nla">Patterson, James W. [http://www.tc.faa.gov/its/worldpac/techrpt/ar97-26.pdf "Impact of New Large Aircraft on Airport Design (PDF)"]. ''[[Federal Aviation Administration]]'', March 1998. Retrieved: December 17, 2007.</ref>

The 747-500X concept featured a fuselage length increased by {{Convert|18|ft|m|abbr=out}} to {{Convert|250|ft|m|abbr=out}}, and the aircraft was to carry 462 passengers over a range up to {{Convert|8700|nmi|abbr=out}}, with a gross weight of over 1.0&nbsp;[[Mega-|Mlb]] (450&nbsp;tonnes).<ref name="faa_nla" /> The 747-600X concept featured a greater stretch to {{Convert|279|ft|m|abbr=out}} with seating for 548 passengers, a range of up to {{Convert|7700|nmi|abbr=on}}, and a gross weight of 1.2&nbsp;Mlb (540&nbsp;tonnes).<ref name="faa_nla" /> A third study concept, the 747-700X, would have combined the wing of the 747-600X with a widened fuselage, allowing it to carry 650 passengers over the same range as a {{not a typo|747-400}}.<ref name="boe_1996" /> The cost of the changes from previous 747 models, in particular the new wing for the 747-500X and -600X, was estimated to be more than US$5&nbsp;billion.<ref name="boe_1996" /> Boeing was not able to attract enough interest to launch the aircraft.<ref name="FI_500X" />

==== 747X and 747X Stretch ====
As Airbus progressed with its [[Airbus A380|A3XX]] study, Boeing offered a 747 derivative as an alternative in 2000; a more modest proposal than the previous -500X and -600X with the 747's overall wing design and a new segment at the root, increasing the span to {{convert|229|ft|m|sigfig=3|abbr=on}}.<ref name="boe_747X">{{cite press release |archive-url=https://web.archive.org/web/20130606052449/http://www.boeing.com/news/releases/2000/news_release_000121a.html |url=http://www.boeing.com/news/releases/2000/news_release_000121a.html |title=Boeing 747 Celebrates 30 Years in Service |work=The Boeing Company |date=September 2, 1996 |access-date=December 17, 2007 |archive-date=June 6, 2013 |url-status=dead}}</ref> Power would have been supplied by either the [[Engine Alliance GP7000|Engine Alliance GP7172]] or the [[Rolls-Royce Trent#Trent 600 – First proposal|Rolls-Royce Trent 600]], which were also proposed for the [[Boeing 767#767-400ERX|767-400ERX]].<ref>{{cite press release |archive-url=https://web.archive.org/web/20120812162427/http://www.boeing.com/news/releases/2000/news_release_000913a.html |archive-date=August 12, 2012 |url=http://www.boeing.com/news/releases/2000/news_release_000913a.html |title=Boeing Commits To Produce New Longer-Range 767-400ER |work=The Boeing Company |date=September 13, 2000 |access-date=December 17, 2007 |url-status=dead}}</ref> A new flight deck based on the 777's would be used. The 747X aircraft was to carry 430 passengers over ranges of up to {{Convert|8700|nmi|abbr=on}}. The 747X Stretch would be extended to {{convert|263|ft|m|sigfig=3|abbr=on}} long, allowing it to carry 500 passengers over ranges of up to {{Convert|7800|nmi|abbr=on}}.<ref name="boe_747X" /> Both would feature an interior based on the 777.<ref>{{cite press release |archive-url=https://web.archive.org/web/20121011162115/http://www.boeing.com/news/releases/2000/news_release_000629b.html |url=http://www.boeing.com/news/releases/2000/news_release_000629b.html |title=Customer Symposium Highlights Future Boeing 747 Models |work=The Boeing Company |date=June 29, 2000 |access-date=December 17, 2007 |archive-date=October 11, 2012 |url-status=dead}}</ref> Freighter versions of the 747X and 747X Stretch were also studied.<ref>{{cite web |last=Morris |first=John |date=July 24, 2000 |title=Boeing in No Hurry to Launch 747X |url=http://www.aviationnow.com/shownews/00farn1/topsto31.htm |url-status=dead |archive-url=https://web.archive.org/web/20110812011727/http://www.aviationweek.com/shownews/00farn1/topsto31.htm |archive-date=August 12, 2011 |access-date=December 18, 2007 |work=Aviation Week}}</ref>

[[File:Qantas Boeing 747-438ER VH-OEI at LAX.jpg|thumb|The 747-400ER was derived from the 747-400X study.|alt=Side view of quadjet in flight]]
Like its predecessor, the 747X family was unable to garner enough interest to justify production, and it was shelved along with the 767-400ERX in March 2001, when Boeing announced the [[Boeing Sonic Cruiser|Sonic Cruiser]] concept.<ref name="shelv_747X" /> Though the 747X design was less costly than the 747-500X and -600X, it was criticized for not offering a sufficient advance from the existing {{not a typo|747-400}}. The 747X did not make it beyond the drawing board, but the 747-400X being developed concurrently moved into production to become the 747-400ER.<ref>{{Cite press release |title=Boeing Launches New, Longer-Range 747-400 |url=http://www.boeing.com/news/releases/2000/news_release_001128c.html |url-status=dead |archive-url=http://arquivo.pt/wayback/20090706141448/http://www.boeing.com/news/releases/2000/news_release_001128c.html |archive-date=July 6, 2009 |access-date=December 17, 2007 |work=The Boeing Company}}</ref>

==== 747-400XQLR ====
After the end of the 747X program, Boeing continued to study improvements that could be made to the 747. The 747-400XQLR (Quiet Long Range) was meant to have an increased range of {{Convert|7980|nmi|abbr=on}}, with improvements to boost efficiency and reduce noise.<ref name="Boe_747-400XQLR">[https://web.archive.org/web/20020306000939/http://www.boeing.com/news/releases/2002/q1/nr_020225h.html "Boeing Offers New 747-400X Quiet Longer Range Jetliner"]. ''The Boeing Company'', February 26, 2002. Retrieved: December 17, 2007.</ref><ref>[http://www.geae.com/aboutgeae/presscenter/cf6/cf6_20020325.html "GE's CF6 Engine Models Tailored For Boeing's 747-400XQLR Wide-Body."] {{webarchive|url=https://web.archive.org/web/20090611140416/http://www.geae.com/aboutgeae/presscenter/cf6/cf6_20020325.html|date=June 11, 2009}} GE Aviation, March 25, 2002.</ref> Improvements studied included raked wingtips similar to those used on the 767-400ER and a sawtooth engine nacelle for noise reduction.<ref>Steinke, Sebastian. [https://web.archive.org/web/20090410050853/http://www.flug-revue.rotor.com/frheft/FRH0205/FR0205c.htm "Boeing Proposes 747-400X Quiet Longer Range"]. ''Flug Revue Online'', May 2002. Retrieved: July 15, 2011.</ref> Although the 747-400XQLR did not move to production, many of its features were used for the 747 Advanced, which was launched as the [[Boeing 747-8|747-8]] in 2005.<ref>Kingsley-Jones, Max. [https://www.flightglobal.com/in-focus-boeing-747-8-technical-description-and-cutaway/107801.article "IN FOCUS: Boeing 747-8 technical description & cutaway"]. Flight Global, November 13, 2012.</ref>