Like many comparisons between Airbus and Boeing – there is more variation between different models within each company than there are differences between the models of the other companies – especially when comparing designs of similar era’s.
The major differences in the assembly process at a high level comes down to two major factors: 1. How the airplane is divided up into “sections” and where the joints between sections are. 2) The sequence these different sections are put together. Both of these are determined early in the design and it is uncommon to change this significantly once a Program is in production. Each variation has certain advantages and disadvantages. Different philosophies of alignment and tooling methods, production rates, transportation considerations, as well as partner worksharing affects what joining sequencing is preferable.
The major part of aircraft assembly can be broken into four parts:
- Fuselage and Wing section assembly – how the wing or fuselage pieces are built up to complete sections.
- Systems Installation – How wiring, hydraulics and other components are stuffed into the airplane or sections.
- Final Section Joins – how the wing and fuselage sections come together to complete the airplane structure.
- Final Assembly – completing the airplane by installing the remaining systems, interior, engines, and testing.
Fuselage Assembly – Most fuselages are built up from “panels”. These can be assembled into full “barrel sections”, or assembled partially with the crown panels going on later.
Typical Fuselage Panel Assembly
747 Fuselage Panel Assemblies [photo: aviation.stackexchange.com]
Typical barrel section, in this case for a Russian Aircraft. [photo: Flight Global]
737 Fuselage Assembly at Spirit Aerosystems [photo: Wichita Business Journal]
One exception to panel buildup are the 787 fuselage sections which is continuously wound in a single piece barrel.
787 Forward Fuselage Section at Spirit AeroSystems [photo: sabaeroline.blogspot.com]
Fuselage Sections – Fuselages are built up into one, three, or more sections before going into the final join positions. These are typically the forward, mid, and aft fuselage sections. Often the forward and aft sections consist of two sections – one containing the rounded portion and one with the more cylindrical section.
Typical forward, mid, aft fuselage section design. [photo: Courtval.com]
Forward Fuselage of the 747 [photo: aero-news.net]
The 737 and A320 fuselage are built into a complete fuselage, with the wing center section attached.
A320 Fuselage [photo: www.solving.com] – wing center section between lifting hooks.
Boeing 737 Fuselage on its way to the Renton, WA plant. Note the wing center box wrapped in white plastic. [photo: aeronef.net]
The A400 and 787 Attach the straight cylindrical portions of the forward and aft fuselage to the mid section first, then add the curved end sections in Final Body join.
A400 Mid Body [photo: Researchgate.net]
787 Mid-Body [photo: Hubtex.com]
The A220(?) with a unique fuselage build with both horizontal and vertical section joins. [photo Global Business Press]
Typically wide body fuselages are assembled into three sections – Forward Body, Center Body, and Aft Body before going into the final join position. The mid-body may or may not have the Center Wing Box attached to the mid-body.
Wing Sections
On almost all models, the wing is broken into three sections: Center, Left, and Right.
A320 Left (front) and Right (rear) Wing. In the foreground you can see the fittings that will attach to the Center Box, shown on the fuselage in an earlier photo.
A notable exception is the A350 with two-piece wing:
The A350 with a two section wing with a center join. Wing structure is completed before attaching to the fuselage [photo:Airbus]. A center join is often used for Horizontal Stabilizers.
Final Join – Final Joins fall into two general categories: 1. Wing Center section is joined to the fuselage first, then the left and right wings are joined to the fuselage (737, A320, A330, 787,…). 2. The sections of the wings are joined first and the fuselage is integrated onto a complete wing (747, 767, 777, A350,…).
Boeing 777 Freighter Join Positions: (foreground) Fwd and Aft Fuselage Systems Installation; (top right in distance) Wing Join Positions; (top left) Final Body Join Position. [photo aviation24.be]
Left and Right Wing are attached to the center box and mid-body fuselage section on the A330.
747 Wing Join positions [photo SeattlePI]. Wing is joined complete first, then fuselage is attached.
Systems Installations – Traditionally the airplane structure and joins were more or less complete before Systems Installations are done. The trend in more recently is to put more of the systems before joins are complete, leaving only a “stay-out zone” without systems installed where final join fastening is done. The trend has been in recent years to put more of the systems in before final joins so the completed airplane can roll out of the factory faster.
Final Assembly –
Until all the wing and fuselage sections are joined, and the landing gear is attached, the airplane sections must be supported with tooling. Once the landing gear is installed, and the airplane is “weight on wheels”, and the airplane can then be pushed or towed through Final Assembly.
Traditionally in Final Assembly the airplane is towed into a stall, or “slant position” (similar to diagonal parking in a car lot) and the airplane would stay in that position until all the work was complete. Since the 1990’s, the trend was to go from this slant position layout to an in-line layout where the airplane would move through the building nose-to-tail with the same work done in the same position in the the factory. This is similar to an automobile assembly line. This could be done where the aircraft would “pulse” from one position to the next on the line, or moved continuously through the final assembly line.
Boeing Renton 737 Final Assembly lines in 2002 showing traditional “slant position” (right) and moving in-line (left). [photo airlinereporter.com]
Current 737 Final Assembly Layout showing two moving lines capable of producing more than two airplanes per day. [photo: aviationweek.com]
There are also differences in how many positions a line uses, what work is done in each position, and the level of automation that is used for fastening and section alignment.
Both companies use some of the same suppliers to build tooling, such as mTorres and Electroimpact. Typically Boeing or Airbus will adopt a new production technology on a specific program, and the other company will adopt a similar or slightly better version on a later program.
Author – Glenn Tomchik
