A Multi-Engine Rating can be added to either a Private Pilot License or a Commercial Pilot License. Even though a twin engine aircraft is much more challenging to operate, it will add a dimension of utility for the pilot who is experienced in this type of aircraft. If you like to plan long, extended trips or carry more weight, then two engines will give you that utility.
A multi-engine rating is almost a necessity if you are working towards a career in flying. Because of their faster cruising speeds and better hauling capabilities, twin-engine aircraft are widely used for passenger or cargo carrying operations. Furthermore, a pilot must have a relatively high amount of "multi-time" before he/she will be considered for a flight position with a major airline.
F.A.R. Part 61 does not set forth a specific number of instruction hours necessary to receive this rating. However, the applicant will have to pass a practical test, which consists of an oral exam and flight evaluation.
Typically, training for this rating can be accomplished in approximately 10 hours. However, most aircraft insurance companies require that you obtain a significant amount of "multi-time" before operating the aircraft as the pilot-in-command. Consequently, certain restrictions apply to renting our multi-engine aircraft.
To earn a multi-engine rating, you must take instructions from an appropriately certified instructor. There is no hourly requirement or a written examination, but an FAA checkride, after which you'll be licensed to fly airplanes with two or more engines. You may hold either a private or commercial certificate.