Samantha Novacek and sister, Patty the Planker, on Thursday’s auditions. (Michael Becker/Fox)

The second night of the Fox singing competition’s 11th season scored 17.7 million viewers and 5.6 percent of the country’s 18-49 year old viewers — the age bracket Fox sells to advertisers.

One year ago, the first Thursday broadcast of the season had scored about 23 million viewers and 7.8 percent of viewers in the important age bracket.

This is the first season “Idol” has debuted just weeks after Fox wrapped a fall singing show starring former “Idol” star Simon Cowell and the worry was it might lead to viewer “singing show fatigue” among “Idol” viewers.

The only time “Idol” has pulled in a smaller second-night number was its first season, when Fox unveiled the new franchise during the summer of ’02. That week — back when “Idol” aired on Mondays and Tuesdays — the very first Tuesday telecast averaged 11.2 million viewers, and 5.2 percent of 18-49 year olds.

In other words, this past Thursday, “Idol” approached its summer season opening numbers in the age category that’s considered the Holy Grail of broadcast TV. In Thursday night’s episode, judges Randy Jackson, Jennifer Lopez and Steven Tyler went with host Ryan Seacrest to cull auditioners in Pittsburgh. Now, “Idol’s” been beaten in the past by specials — Olympics and such — but, if the numbers wash out the same way when final national stats arrive this afternoon, it could be the first time a regular series has beat “Idol” in the Golden Age Group.