Problem with ddrescue

I have Ubuntu 11.04 on a 40 gig HD. I am trying to clone it to another 40 HD. I have installed ddrescue and it says it installed ok. But when I try to use it using the codes:
sudo ddrescue -v /dev/sda /dev/sdc or sudo ddrescue -v if=/dev/sda of=/dev/sdc
it says ddrescue command not found.
Anybody got any ideas how to fix this problem?
I don't have any trouble using it in 10.10.
Thanks.

 

I think my problem was a bad HD. I can clone from one ubuntu 10.10 20 gig to another 20 gig. I can clone from one 20 gig to a 40 gig alright. I updated the ubuntu 10.10 40 gig to 11.04 using the internal updater. However cloning to the other 40 would not work. Have determined that HD is bad.