On a Tuesday that saw Fox dominate as usual with “American Idol” and “House,” CBS drama “The Unit” got off to an excellent start with its premiere. Also, ABC did OK with the bow of laffer “Sons & Daughters.”

According to preliminary nationals from Nielsen, “The Unit” averaged a 5.1 rating/12 share in adults 18-49 and 18.2 million viewers overall, the second best demo debut and the largest overall aud for a drama this season. CBS hasn’t done better in the time period in 18-49 since last May’s “Amazing Race” finale. It grew impressively on its lead-in from “NCIS” (3.8/10 in 18-49, 17.3 million viewers overall).

In both hours, CBS ran second to Fox: “American Idol” opened with typically huge numbers (11.6/30 in 18-49, 28.3 million viewers overall), and “House” led at 9 with its second-best scores to date (8.4/20 in 18-49, 20.6 million viewers overall).

ABC comedy “Sons & Daughters” averaged a 3.4/8 in 18-49 and 8.4 million viewers overall with its 9 o’clock episode, the net’s best showing in the time period in four months. A second seg at 9:30 fell off a bit but kept the net in third place (3.0/7 in 18-49, 7.5 million viewers overall).

NBC brought back “Joey” at 8 (1.4/4 in 18-49, 4.1 million viewers overall) but probably wishes it didn’t after anemic scores on its new night. “Scrubs” picked up at 9 but placed fourth (2.8/7 in 18-49, 5.7 million viewers overall).

At 10, CBS’ “Amazing Race 9” (3.7/10 in 18-49, 9.4 million viewers overall) won in key demos over ABC’s “Boston Legal” (3.4/9 in 18-49, 11.3 million viewers overall) and NBC’s repeat “Law & Order: SVU” (3.4/9, 10.2 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 10.0/25; CBS, 4.2/11; ABC, 2.9/8; NBC, 2.6/7; WB, 1.0/3; UPN, 0.7/2.

In total viewers: Fox, 24.4 million; CBS, 14.9 million; ABC, 8.4 million; NBC, 6.6 million; WB, 2.4 million; UPN, 1.7 million.