Once you've studied aircraft systems you'll get into aerodynamics peculiar to single-engine operations in a twin and the speeds you'll need to know for the particular airplane and their significance:
minimum control speed (Vmc), single-engine best rate of climb speed (Vyse), single-engine best angle of climb speed (Vxse) and safe single-engine speed (Vsse).
First of all, let's define what we mean by "flight at minimum controllable airspeed." Importantly, this is not the same as a conventional twin's VMC, or
minimum control speed with the critical engine inoperative.
These factors include
minimum control speed, refusal speed, rotation speed, lift-off speed, climb-out speed, three-engine rate of climb, decision speed, flap-retraction speeds, and center-of-gravity limits.
Testing includes Vmcg (ground
minimum control speed), trimmed and mis-trimmed takeoff characteristics.
The aircraft was being flown below its
minimum control speed for flight on one engine and therefore crashed.