Hi Pavan,
you have me totally confused: If you write your log backups to tapes, how can they be in ${DIR_INSTANCE}/backup/log?
Any log backup that gets created on the file system (the actual directory doesn't matter) can be deleted via the BACKUP CATALOG DELETE statement, as long as it is maintained in the backup catalog - unless you manually move the backup to some other location. If you have managed your log backups incorrectly, it can be that a deletion fails (e.g.: moved log backups away from original location; then deleted from catalog; then put log backups back into original location and try to clean up using BACKUP CATALOG DELETE).
If you have not messed up your system yet, and if now log backup deletion is not working on your system, it would be a bug and you would have to open a ticket with SAP support, and in this ticket describe with as much detail as you can provide the situation. Parameter values and screenshots might be helpful, or providing system access.
Scheduling of backup deletion would be a feature request - for those SAP customer messages would be the wrong forum.
I believe you are either not describing your situation correctly, or you testing wrongly, or there is a bug in the software version you are using.
Best,
Richard