Civil Engineering Reference
In-Depth Information
the center tank is situated which has a capacity of up to 52 t of aviation fuel. The
terrorists responsible for the attacks on September 11, 2001 specifically chose long
routes airplanes to maximize the damage caused by the largest possible amount of
aviation fuel. The center and stabilizing tanks are only filled when necessary, i.e. for
long distances. The reason for this is the significantly better relationship between
the buoyancy and the dead weight of the wings. Due to this the center tank is usually
the first to be emptied. This means that for a long-distance flight it might be
assumed that the center tank is initially full when considering the mass distribution.
Take-off and the approach to the target can be assumed to require approx. 20 t of
aviation fuel. The “Jumbo-Jet” uses about 8 t of fuel per hour and about 10 t are
required for take-off and climbing flight. Since only some airplanes have a tank in
the rear only a partially filled rear tank can be assumed with respect to the mass
distribution.
The wings are connected to the fuselage in the central part of the aircraft laterally
to the center tank. Due to the necessity of transporting the above mentioned airplane
to Speyer via the Rhine the wings had to be separated from the fuselage. As a result
a relatively detailed inspection of the design of the wing including the internal
structure was possible (cf. Fig.
14.14
). The main load carrying action of the wing
occurs in the central section where the tanks are also located. This section is
reinforced with numerous longitudinal and transverse girders.
The connection between the wing and the fuselage, called the wing root, consists
of a two-celled box girder cross section and is only connected to the fuselage as a
load-bearing cross section around the tank. The rear edges of the wings show a bent
close to the fuselage at which point the wing widens towards the fuselage. A solid
girder is installed here to decrease the force on the outer landing gear and to stiffen
the wing. In addition to the outer shell longitudinal girders are arranged on the
upper and lower surfaces of the wing. When considering the distribution of the wing
mass it is important to keep in mind that the structural and fuel distributions need to
be known not only in the direction of the wing, but also the longitudinal direction of
the airplane. The jet engines connected to the wings also contribute significantly to
the distribution of the mass of the wings.
The landing gears represent fairly large individual masses. The nose landing
gear (cf. Figs.
14.15
and
14.16
) has a width of approx. 1.20 m when measuring the
wheels and is connected to a hydraulic cylinder of approx. 2 m in length which
points in the direction of flight when retracted. When viewing the landing gear the
important additional function of damper for the landing process also becomes clear.
The vertical hydraulic cylinder has a diameter of around 30 cm and a length of
about 2 m. Since the landing gear has to be assumed to be retracted in the case of a
deliberate forced crash, its mass has to be distributed over a length of just over 2 m.
In addition to the wheels and the axle the mass of the suspension assembly in the
aircraft fuselage must be taken into account.
The main landing gear consists of four landing gear groups, one pair of which is
arranged slightly behind the other directly in the fuselage. These inner landing gears
are retracted forward such that the approx. 2.5 m long hydraulic cylinder faces in
the direction of flight.
