I have read a crash report of a new Mercedes-Benz C250 which hit a Palm tree in Los Angeles, tragically killing journalist Michael Hastings. What was shocking to me is that, apparently, the engine flew out of the vehicle during impact and landed almost 50 metres away. Is this normal or is Mercedes-Benz cutting corners when it comes to vehicle safety as its response to the incident left a lot unanswered? I am now scared to buy a Mercedes-Benz owing to the fact that the engine might fly out on impact.
MARK VIDAL, Somerset West
Answer: Unfortunately, there is very little information about the tragic incident, including vehicle speed, angle of impact and so on, so we can comment only in general. The response from Mercedes-Benz was fair because no two accidents are the same and, without knowing all the details, it is impossible to offer an explanation.
From a physics point of view, the engine of a vehicle constitutes a large mass concentrated in a small area that carries a lot of kinetic energy (momentum) at speed. The engine and gearbox are fixed to the body via powertrain mounts. In case of an accident with massive deceleration (like hitting a palm tree), the force on the engine mounts might very well be enough to snap them and send the engine flying. We have seen many pictures of high-speed accidents involving supercars in which the engines separated from
the bodies.
When a front-engined car hits a wall (or another vehicle) as in NCAP testing, the engine is designed to be pushed downwards and toward the rear of the vehicle so as not to infringe on the cabin (survival) space. When hitting a narrow object like a palm tree, the impact force may miss the engine and then the momentum of the engine might snap the engine mounts if the deceleration is severe enough (such as coming to an abrupt stop from high speed, for example).