Contra rotating propellers for the A400M

liebensd · Post by **liebensd** » 21 Jul 2004, 14:41

When I was watching a movie about the current Farnborough air show I saw a A400M with contra rotating propellers. I went the official web side of it and pictures of the A400M confirmed it. http://www.airbusmilitary.com/images/oblique.gif
When you look closely to the picture you can see that the inner ant outer propellers have a different shape. I asked this question already on Luchtzak but I didn’t get a good reason for it, When an aircraft builder chooses to use contra rotating engines is this because of the reduction of torque that is produced by the engines?

Greetz,

Dave

Lyulka · Post by **Lyulka** » 21 Jul 2004, 15:18

Are you sure it uses those contra-rotating propellers? I can't find any confirmation of this..
The reason why to choose for contra-rotating propellers is most of the time the higher speed which can be attained. I don't know what's the raeson for this, but perhaps it has something to do with the extra low pressure-zone you create in between the two propellers, like with a jet engine. The major reaon not to use it is the fact that their are a lot of technical difficulties accompanied with this (cfr An70).

Lyulka · Post by **Lyulka** » 21 Jul 2004, 15:27

Oops I misunderstood. You mean the different propellers on the wing turn in a different direction.
Indeed, it seems to be like this, but let's wait to see when it flies. This will indeed reduce torque, but it also means they need to produce two different engines: one turning clockwise, one anti-clockwise.

liebensd · Post by **liebensd** » 21 Jul 2004, 16:13

Lyulka,

It are turboprop engines, so they have a gearbox. It also possible that the engines turn in the same direction but that the gears switsh the direction.

Greetz,

Dave