Why are weights hung from engine mounts on empty a/c?
 

So I'm browsing flickr and airliners net and I found 2 recent pictures of boeings 787 with the engines off, and what's described as a large concrete block hanging from the engine mounts.

http://www.flickr.com/photos/moonm/3844186126/sizes/o/

http://www.airliners.net/photo/Boein...ner/1570859/L/


Does anyone know why they hang these "weights" from the engine mounts? What purpose does it serve?

thanks,
Jen

[Moderator note: Thread title was edited to better reflect OP's inquiry.]

It's a matter of weight and balance. Take the engines off the empty airplane and it will settle on its tail.