Boeing fuselage Section 41

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Section 41 on a Boeing 777.

Section 41 is the forward portion of a Boeing aircraft, from the nose to aft of the cockpit^[1]. In some models it includes the forward door and may extend to the first class cabin. Along with the wings, it is one of the most complex parts of an aircraft, and includes the largest share (around 40%) of an aircraft's avionics and control systems.

Other portions of the aircraft are numbered as well, but those numbers often vary, and Section 41 plays a particularly important role.

As Section 41 is a complex component, identical models are shared within two groups of Boeing aircraft:

The 707/720, 727, and 737 have a common Section 41. Newer versions of the 737 have a different avionics package while retaining structural commonality.
The 767 and 777 also share the frontal portion. These aircraft have vastly different avionics, however.
The forward-most section of the 787 encompasses more of the aircraft than in past models. This is due to the aircraft's modular design and Carbon Fiber Reinforced Plastic (CFRP) construction (the first such design of its type)^[1]

The identity of this portion of Boeing aircraft came to higher prominence during the investigation of the Pan Am Flight 103 incident in 1988. Section 41s for all Boeing 7xx-series airliners, with the exception of the 717, are constructed at what was formerly Boeing's Wichita, Kansas facility (now Spirit AeroSystems).

The phenomenon of sharing cockpit sections across models is not exclusive to Boeing. Indeed, the de Havilland Comet and Sud Aviation SE 210 Caravelle shared their frontal section in much the same manner. This is also true for the Tupolev Tu-204/-214 and Tu-334.