The correct answer is (D), 80% of you got it right. 👍
(A) is incorrect because an aircraft should not be removed from the pattern unless traffic overwhelms the airport and the controller’s abilities to also accommodate patterns. In this case, with two runways, a controller should be more than able to accommodate two aircraft. Keep in mind that aircraft control is at the discretion of the controller, and a controller can deny a runway change at any time they wish.
(B) is incorrect because a go around is not the proper response to a runway change request. Following that, spacing after sequencing is the responsibility of the pilot, and using speed commands for this matter can be seen as overcontrolling. Proper use of these commands on a tower frequency would be for timing departures in between arrivals, and is rarely used for spacing sequenced aircraft.
© is incorrect because a sequencing command is also not a proper response to a runway change request. (See reason in explanation for D) Along with this, 123A is still in the pattern, meaning he should be cleared for the option, not to land.
(D) is correct because a proper response to a pattern entry request will either by a denial, or a pattern entry. This is because each runway has its own pattern. This means the simple task of switching runways requires switching patterns, and entering a new in. To shorten commands, a sequencing command can be added in conjunction to make one, overall shorter message. Following that up, and a later time possibly, a clearance command can be given. This should be done later, around downwind or base, to ensure that no re-sequencing is required, and if so, re-sequencing is much easier.
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