Two Engines are Safer than one?  

At first, adoption of Single Engine operations appears to break the “Golden Rule of Redundancy”. For the last hundred years, the technique to overcome component failure in aircraft has been to duplicate. This has proved very successful for systems, such as avionics and controls, where the redundant systems can be designed to fail to a safe state and without adverse interaction with each other.Though it may come as  

a surprise to some, the propulsion system of a twin-engine propeller driven aircraft does not have these essential c haracteristics.  The engines strongly interact through asymmetry of thrust and do not inherently fail-safe.  As a consequence a failure requires correct identification and time critical management (indeed for some types, skill) to make a successful transition to single engine flight.  The air disaster  at Kegworth in a Boeing 373-400 where the crew misidentified the failed engine and shut down the correctly functioning unit demonstrates clearly that there is no inherent fail safe. The crash landing of an Air Transat A330-200 at Lajes  (Azores) in 2001, which ran out of fuel due to a fracture in a supply line on     

one engine clearly demonstrates the difficulties in managing duplicated and complex systems.  Even a low probability of loss of control following an engine failure largely negates the protection afforded by the second engine because the chance of an engine failure is doubled. There have been many fatal accidents when training pilots in single engine approaches and go around on ME engine aircraft.

The accidents are not included in the statistics as they are Training not Charter operations.
In addition, twin propeller aircraft only offer the possibility of partial redundancy.  This is because the major sub-systems in the propulsion system are the two propellers as well as the two engines. A failure in either propeller pitch control mechanism that leads to asymmetric thrust or drag results in a high probability of a fatal loss of control.

Given these factors, the risk of a duplicated asymmetric system is more than double than that of a single system.  This may help to understand why the statistics show that single engine aircraft with ultra reliable turbine engines are now safer than twin-engine piston aircraft and as safe as light twin-engine turbine aircraft.

As these pictures illustrate propellers can fail as well as power plants. Row 30 is perhaps not the best place to sit.
The propeller entered on the starboard side and exited on the port side.