Aircraft Accident Investigation
Air Asia plane exploded after hitting water? This
is a good question so far. Part of the plane's tail was broken into pieces and
a flight data recorder was thrown more than a kilometer (.62 miles as the news
show on the media)
All aircraft accidents are different; there are
certain elements that are common to aircraft impacts and wreckage distribution.
By organizing those elements, we can predict and explain most impact
situations.
Some, for various reasons, will defy any rational
explanation.
The two questions that usually need to be
answered are:
1.What was the attitude of the aircraft at
impact?
2.Was this impact survivable?
Influence of Aircraft Velocity and Impact
Angle
Crash dynamics and wreckage distribution is
influenced primarily by aircraft velocity and impact angle.
The velocity of the aircraft generally
determines the degree of breakup and destruction of the wreckage.
The impact angle determines how the wreckage will
be distributed. We will deal with each of these separately.
Water Impacts
These deserve a brief mention. What happens
when a plane hits the water?
Actually, it is primarily a function of
velocity. If the plane is going fast enough, the water is a solid object as far
as the plane is concerned. It comes apart in about as many pieces as it would
if it had crashed on land. At the other extreme, a plane that was deliberately
ditched will probably sink to the bottom in one piece.
In a water impact, there is an impact angle,
but it is related to the wave action on the surface of the water. If the water
was absolutely calm, then the impact angle may be determined by examination of
the wreckage. If there was heavy wave action, impact angle becomes meaningless
as you don’t know whether the plane impacted on the front or backside of wave.
What is the significance of the distribution of
wreckage on the bottom of the lake, ocean, or river?
In general, the wreckage distribution doesn’t
mean much unless it resulted from an inflight breakup.
The actual distribution is influenced by depth,
currents and the tendency of various parts to float (or be slightly buoyant) or
to sink in different fashions. Some parts of the plane will sink like a rock.
Others will sink like a dinner plate. Try it and you’ll see the difference.
One rule that does hold up fairly well is the
dispersed part rule. A portion of the airplane or its contents found at a significant
distance from the main wreckage probably came off inflight.
Source: Aircraft Accident Investigation
(Richard H. Wood / Robert W. Sweginnis)
