newbie question about minimum gross gradients by engine failure

[quiquehsu]

Hello,

I'm a engineering student in germany having his first exam about aircrafts, so please apologise if the question is too stupid.

I have the table for minimum gross gradients by engine failure and it says

engines .........2............3........... 4
1.Segment.....0%........0.3%.......0.5%
2.Segment....2.4%.......2.7%.......3.0%
3.Segment....1.2%......1.5%........1.7%

I don't understand this table. Why is it, that with more engines you need a higher climb rate?

thanks in advance

[Rainboe]

Interesting! I would say that with 4 engines, you are twice as likely to have an engine failure, and you will be heavier as you are a longhaul aeroplane, therefore the minimum margin is increased. Think: 2 engined A330 and 4 engined A340, much heavier.
In practice, better to have an engine failure on a twin than a 4 engined aeroplane as the thrust/weight ratio is higher. Therefore twins climb out more steeply than 4 engined heavy aeroplanes.