The fuselage aft is the back area of an aircraft, the rear portion of the central body opposite the nose. This afterbody continues the fully metallic monocoque structure and encloses the aft baggage compartments, aft service compartments, and the aft pressure bulkhead - the rear part of the pressure seal that keeps cabin air contained.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the definition of aft fuselage?
The aft fuselage extends from the wing's trailing edge to the rear end of the aircraft; it is the rear section of the fuselage. The aft pressure bulkhead is the rear part of the pressure seal in all aircraft.
The aft fuselage is the rear portion of the main body of an airplane. Aft means the back area of the aircraft, opposite the front or nose. This section begins behind the wing and extends to the tail, housing the empennage with its vertical and horizontal stabilizers. Engineers plan distribution of weight and space within the aircraft so that the curved or flat aft pressure bulkhead forms the rear part of the pressure seal, while still offering the cargo volume needed when the center of gravity moves aft.
What is the function of the aft end of the fuselage?
The aft end of the fuselage closes the pressure cabin with an aft pressure bulkhead that protects the aircraft from bursting due to the higher internal pressure when stratocruising. Usually a spherical bulkhead is located at the aft end to absorb pressure while keeping the skins of the bulkhead mostly in tension. Bulkheads are curved or flat, with flat bulkheads providing more internal space but adding more weight, while curved bulkheads reduce the amount of metal needed at the cost of reducing usable space in the airliner. The aft cargo hold stores luggage and freight, and careful weight management is vital because the aft section is pivotal in achieving optimal balance. Pilots receive instructions regarding shifting cargo or fuel to or from the aft section to maintain the center of gravity. Galley and lavatory are often situated in the aft section, and their locations influence passenger flow and comfort during flight. Pressure bulkheads carry loads imposed by pressurization, and inspection routines include detailed checks of the aft section for structural integrity, system functionality, and potential damage to guarantee the aircraft remains airworthy.
What is the aft fuselage structure?
The aft fuselage structure is the rear section of the aircraft that supports both engines, the APU, and the empennage. It is a semi-monocoque shell built from frames, stringers, and skin. At Fuselage Station 287 a single frame redistributes the heavy loads coming from the center section truss structure into this lighter aft shell. The aft pressure bulkhead seals the rear end of the pressurized cabin. On the double-deck A380 airliner this bulkhead is the largest resin film infusion part. Behind the bulkhead, the tail cone passes through the pressure shell as a rectangular opening not less than 20 inches (50.8 cm) wide by 36 inches (91.44 cm) high. This opening is closed by removable access panels for inspection and maintenance of systems routed to the empennage. Beneath the shell, a fairing structure extends to carry the thrust spoilers - two doors located aft of the engine tailpipe nozzles that help modulate jet efflux.
The lower aft fuselage is the belly region of this same rear shell. Here the skin is locally replaced by a lower shear web so that space is created for the M-shaped auxiliary spar that carries additional bending loads from the wing root. The aft baggage and service compartments are built into this lower shell, but the aft main fuel tank is kept as a separate sealed structure aided by the fuselage rather than being integral with it. Aft pressure bulkheads are flat, giving more internal space at the price of extra weight, or curved, reducing the amount of metal (or composite) required while slightly decreasing usable cabin volume.
Where is the right aft fuselage located?
The right aft fuselage lies behind the center wing box and to the pilot's right as seen from the cockpit at the front of the airplane. The appropriate astern fuselage is an area situated behind the commuter compartment. .
Where is the engine located on the aft fuselage?
Most corporate jets feature two engines fitted on the rear fuselage. Embraer ERJ family and COMAC ARJ21 regional jets have engines mounted on the fuselage tail. Some Dassault aircraft, like the Falcon 900, comprise three rear-mounted engines.
What are the effects of aft fuselage mounted engines on aircraft stability?
Aft fuselage-mounted engines produce several noticeable changes to trim and stability. They move a considerable amount of weight aft, and rearward centre-of-gravity decreases stability but increases manoeuvrability. With the aerodynamic centre near 25% mean aerodynamic chord, the aeroplane is normally nose-heavy. Weight at the aft mitigates some required downward tail load, yet an aft CG reduces pitch stability and increases the risk of uncontrollable pitch oscillations. Because the stabilizer must be mounted above the slipstream, aft-mounted engines result in a T-tail configuration. This arrangement enters a deep stall because the horizontal stabilizer sits within the wing wake at high angles of attack, producing buffet and a tendency against nose-down recovery. Engine placement, therefore, affects both longitudinal trim and static pitch stability negatively.
From a directional standpoint, the fuselage and engine nacelles create a destabilising contribution to directional stability, but engine placement is still preferable when compared with under-wing installations. Aft-mounted engines are much closer to the aircraft's centreline. Thus, when an engine fails, they generate less yawing moment, require a smaller vertical tail, and make rudder control easier, especially when the pilot counters remaining asymmetric thrust with the rudder. An aft-fuselage engine failure produces far less undesirable yaw than under-wing engines which are farther away from the CG.
Why are nacelles of aft fuselage-mounted engines positioned that way? They are located at the aft fuselage primarily to offer cleaner wings and reduce wing bending moments, thereby enabling a lighter wing structure. The weight aft also moves part of the useful-load range downward, counterbalancing the naturally nose-down moment and permitting smaller elevator deflections. The arrangement provides quieter cabins because engines sit behind the passenger cabin, and on multiple-engine aeroplanes it demands a smaller fin and rudder because it produces less asymmetric thrust when one engine fails. Although an aft CG lessens stability, the advantages - reduced asymmetric-thrust yaw, cleaner wings, smaller main-wing structural weight, and simplified directional control - explain why those nacelles are placed at the aft region of the fuselage.
What are aft fuselage strakes?
Aft fuselage strakes are strakes mounted on the fuselage of aircraft, positioned under the rear fuselage, and they channel airflow. Raisbeck Dual Aft Body Strakes boost directional stability, aircraft control, and handling by eliminating wing/body vortices, which disrupt airflow.
Aft fuselage strakes are sharp-edged, low-aspect-ratio aerodynamic surfaces that protrude from the rear fuselage. One or two large fins or horizontal strakes are sometimes positioned under or high on the aft fuselage. Strakes act as end plates to prevent air from spilling around the bottom of the fuselage. They keep airflow attached underneath the aft fuselage and channel it smoothly aft.
Dual Aft Body Strakes (DABS) shed wing-to-body vortices captured under the aft fuselage, eliminating these vortices and reducing aft body drag. By tucking the flow closer to the fuselage, they reduce form drag in all phases of flight, create better climb and cruise performance, and reduce noise for a quieter cabin and cockpit.
Strakes increase side force when the airplane is yawed, boosting directional stability and working to limit Dutch roll. Dual Aft Body Strakes add 10% more vertical surface area to stabilize the aircraft without increasing empty weight. They refine pilot control during takeoff, climb, landing, and eliminate or increase OEM yaw damper inoperative altitude limitation.
On the Hawk aircraft, a strake placed on the fuselage in front of the tailplane solves tailplane under-surface stall at high negative angles. These Tailplane Canard Vanes (TCV), called side-mounted rear fins (smurfs), act as large vortex generators to prevent uncontrollable nose-down pitch.
Raisbeck Dual Aft Body Strakes are the most popular performance system in the Raisbeck arsenal and are OEM standard on all new King Air 350, 360, and C90GTx aircraft. They are compatible with a wide range of King Air and Cessna Caravan 208B models, offering an unmatched benefit-to-cost ratio.
What are locations fore and aft along the fuselage known as?
Fuselage stations (FS) are the numbered lines that define location fore and aft on an airplane. A station is usually described as inches aft or forward of the datum and the reference point set near the nose. The distance from this datum to any object loaded is called the arm. These stations mark every frame and every point along the longitudinal axis, so the exact position of doors, bulkheads, seats, or baggage compartments is fixed by a single FS number.
On the same scale the fore-and-aft limits of the permissible center-of-gravity range are given as stations, assuring the CG remains within the certified envelope for flight. Thus, whether the task is to place a cabinet on a butt-line left or right of the center-line, or to check that an added load keeps the CG inside its aft limit, the mechanic reads the same station numbers painted on the fuselage skin.
Is the fuselage diameter the same forward and aft?
The fuselage diameter is not the same forward and aft. The Boeing design has a fuselage whose diameter varies over the cabin section, so the diameter measured forward is not identical to the diameter measured aft. Today's passenger aircraft have constant fuselage cross-section in the central section, yet ahead of this constant section the nose section is defined as the section that extends from the forwardmost point on the aircraft to the maximum diameter section, and behind it the tail cone is mildly tapered. Therefore, the contour grows then shrinks along the longitudinal axis. Because the maximum fuselage diameter is 117 cm (46.06 in), the local diameter forward of the constant cabin is less than 117 cm (46.06 in) while the diameter aft diminishes below 117 cm (46.06 in), confirming that the forward and aft diameters differ from each other and from the peak.
