Whats the purpose of multi motor, or engined, aircraft?

[Bythebookie2]

Why cant their just be one large engine, and one large propeller?

[cmhshh]

The propellor hits the ground unless you have 50ft high landing gear and the engine is so heavy it can't lift itself off the ground.
Well you could mount the prop pointing up - but that's a helicopter and they only fly 'cos they are so ugly the earth repels them :)

SH

[BMatthews]

Because engines are only so big so if you want a bigger airplane you need more than one of them.

There is also the issue of one engine outage. If you only have one and the fire goes out you're in big trouble. If there's more than one you can limp to safety. Back in the 30's single engine passenger transports were common. But then the regs were changed to disallow them in favour of the safety of twin engines. So it's not ALL just because folks don't want to make singles.