Civil Engineering Reference
In-Depth Information
German and allied military aircraft until reunification in 1989 and the improvement
of relationships between east and west. In the 1970s and 1980s many crashes
occurred during military training flights, especially during low-level flights. In
this time frame 15-25 accidental crashes occurred per year, excluding those that
occurred during takeoff and landing manoeuvres close to airports (radius approx.
5 km). The possible scenarios and crash frequencies were discussed in detail in
context of the German risk study of nuclear power plants [
1
,
2
]. Fast flying military
aircraft often with free flight paths and flying at low levels where considered a
potential for danger.
The number of crashes, their spatial distribution, impact speed, impact angle and
the different types of aircraft with their specific mass distributions were analyzed
and probabilistically evaluated in the threat investigation. The possible armament
of the military aircraft was not considered. Figure
13.1
shows cumulative frequency
curves of different parameters.
The distribution curve of the mass shows that only few crashedmilitary aircraft had
a takeoff weight higher than 20 t. A further focal point of the distribution curve are
aircraft around 10 t. This is the result of the large number of Starfighters, weighing
about 10 t, and Phantom F4, weighing about 20 t, used in the 1970s and 1980s.
The cumulative frequency curve of the impact speed v shows that crashed
military aircraft with a speed higher than 225 m/s barely contribute to the sum.
The impact angle
is nearly equally distributed between 0
and 90
.
The endangering due to accidentally crashing large commercial aircraft is
significantly lower than with military aircraft. This is explained by the fact that
large commercial aircraft follow predetermined flight paths and do not operate in
free air traffic, in addition to not performing low-level flying with the exception of
takeoff and landing. The crash probability is much lower than with fast flying
military aircraft. The pilot of a military aircraft will in the case of a major fault leave
the plane by an ejector seat, leaving the aircraft to itself. Due to their high operating
altitude of large commercial aircraft usually maneuverability options are available
in case of a fault. The pilot and co-pilot cannot leave the aircraft and will usually
attempt a controlled emergency landing. The accidental crash of a large commercial
aircraft is seen as very unlikely and is not considered for the design of nuclear
power plants.
Civilian light aircraft are not bound to a flight path and fly at low altitudes much
like military aircraft. In comparison to large commercial aircraft they have a
considerably higher crash frequency. However, the mass and speeds are lower
than those of the military aircraft mentioned above, and the effects are therefore
covered within the scope of the military aircraft. Falling wreckage of a possible
explosion of large commercial aircraft in flight are also covered by this case.
Starting with a uniform distribution of the crash frequency over the area of the
Federal Republic of Germany of 10
10
crashes/m
2
/year yields the value of 10
6
crashes/year over the area of a nuclear power plant. This value is a conservative
estimate and means that a power plant can be hit by an accidentally crashing
military aircraft with a probability 10
6
/year, independent of the possible damages.
ϑ
