I frequently rent Piper Seminoles from my FBO. As part of their rental agreement for the Seminole, I'm required to undergo an annual proficiency check.
The Piper Seminole is small two-engine airplane with constant speed propellers and retractable landing gear. (Such airplanes are commonly called a "twin".) Airplanes like the Seminole are more complicated to fly than a simple single-engine airplane like the Cessna 172 or the Diamond DA40. Although most small airplanes fly the same, differences becomes apparent when an emergency arises. And the most challenging emergency a pilot can face is an engine failure.
Engine Failure: Single Engine versus Twin Engine
If an engine fails in a single-engine airplane, it becomes a glider. You don't have a choice in the matter. Simply pitch the nose down to maintain the best glide speed land in an open area. It's no surprise that simulated engine failures are a common component of private pilot training and certification.
In a two-engine airplane, a single engine failure means only half the thrust is lost. But think about situation some more and you can appreciate why twins are harder to fly: the working engine must now contend with the weight and drag of the dead engine. Thrust is asymmetric, which adds to challenge, because if you fly too slow with a failed engine the plane can flip over. Scary!
Unlike a single-engine airplane, a twin with a failed engine is not a glider. Having one functioning engine can give a poorly trained pilot a false sense of security. In reality, an engine failure (50% power loss) results in a performance loss of about 80%! The plane is still capable of flight, but with significantly degraded performance.
A good pilot knows how to fly any airplane not only when all is well, but when an emergency arises. To see an emergency situation through to a safe outcome requires practice. And it's a good idea to undergo routine training flights, such as a proficiency check, to practice emergency situations. Preparation makes for safe aviation.
Here's a picture of a Seminole I rent.