Controller Question-two planes and a runway

[stevekirks]

Heard this on LiveATC today:

KSNA Tower: ExecJet123 cross runway 20L, hold short runway 20R
(readback by ExecJet)
KSNA Tower's next call within two seconds: Cessna 2SP runway 20L cleared for the option
(readback by Cessna)

In my head, this means that the ExecJet could be in conflict with runway 20L and the Cessna was given clearance (with pilot option full stop landing) on 20L. How is that possible?

[Kevin_atc]

Just because someone is cleared for the option doesn't mean they're on short final. Anticipated separation is a controller's best friend in the terminal environment. As long as the controller anticipated that the aircraft crossing the runway would be clear before the landing aircraft crossed the threshold, then the aircraft are considered separated using anticipated separation.

EDIT: To add to that and go a bit more in depth, runway crossings are different than line up and wait (LUAW) as far as rules with landing aircraft. If an aircraft is LUAW on a runway, then there cannot be an aircraft cleared to land (or the option) for that same runway. It is for this reason that you'll hear things like "Runway 20L, continue, traffic holding in position." However, there are ways around this with safety logic systems that most large airports in the RW have therefore you'll typically only see controllers withholding landing clearance for the reasons stated above at small airports or at larger airports when ATC has minimal staffing or the safety logic system is inop.

[stevekirks]

Just because someone is cleared for the option doesn't mean they're on short final. Anticipated separation is a controller's best friend in the terminal environment. As long as the controller anticipated that the aircraft crossing the runway would be clear before the landing aircraft crossed the threshold, then the aircraft are considered separated using anticipated separation.

EDIT: To add to that and go a bit more in depth, runway crossings are different than line up and wait (LUAW) as far as rules with landing aircraft. If an aircraft is LUAW on a runway, then there cannot be an aircraft cleared to land (or the option) for that same runway. It is for this reason that you'll hear things like "Runway 20L, continue, traffic holding in position." However, there are ways around this with safety logic systems that most large airports in the RW have therefore you'll typically only see controllers withholding landing clearance for the reasons stated above at small airports or at larger airports when ATC has minimal staffing or the safety logic system is inop.

Thanks. That seems like the common sense thing (separation) and you answered the other question in my head that I couldn't figure out how to ask...

By the way, just listened to real pilot make the same mistake I've made on the I-3 exam, not joining V23 the right way....

[Keith Smith]

This might be an interesting aside, I was flying out of Teterboro yesterday, holding short of rwy 19. A jet had taken off before, and another one had just been cleared to land.

The controller then canceled the landing clearance of the inbound and gave us a line up and wait, "be ready to go..." This is an example of Kevin's point that you can't have someone cleared to land while someone else has been told to line up and wait. Once we were given the takeoff clearance, the guy on final was then cleared to land.