Possible causes of disaster (4) – The aircraft abruptly lost altitude

On 10 April 2010, Polish military plane Tupolev 154M-101 crashed under Smolensk (Russia), killing all passengers and crew. The immediate origin of the accident was that erstwhile approaching landing, the plane was flying besides low. Why was the plane flying besides low in this phase of flight? It is very likely that the plane was on a good course and good tallness until [...]