Narrative:

While enroute to ZZZ on aircraft X we observed an abnormal number 2 engine vibration; we contacted dispatch and were told to return to ZZZ1. The return to field occurred uneventfully. We were assigned a new aircraft and re-launched for ZZZ. On the second flight; before we started our descent into ZZZ; we obtained the WX (ASOS); visibility was reported at ¼ sm (1600 RVR equivalent) and indefinite ceiling; we discussed our options and decided to execute a CAT ii approach; we had a pretty strong tailwind; so the arrival occurred quite rapidly. To our surprise and due to our late arrival; we discovered that the control tower at ZZZ had already closed; approach control advised of low visibility at the airport as reported by another aircraft that had just landed. We set up the approach according to our established procedures (transferred control to first officer; set and briefed the approach; monitored approach; etc...). The entire area around the airport showed scattered areas of patchy fog close to the ground; we could see the airport even though there was a patch of fog on top of the airport; we could see the runway lights through the fog. The CAT ii approach was executed to the FAF and then the ca took controls and continued as a normal CAT I approach because visual conditions were adequate. We could see the approach lights and runway lights through the fog from the FAF. A safe landing was made and visibility on the ground was 1/2 sm. I failed to recognize the control tower was closed and that RVR reports are required for a CAT ii (visibility reports only are not enough; actual RVR reports are needed) in the future I will ensure that all required items needed for the execution of a CAT ii approach are operationally/available before starting this procedure.

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Original NASA ASRS Text

Title: EMB-175 Flight Crew reported non-compliance with company policy by executing a CAT II approach without available RVR reports.

Narrative: While enroute to ZZZ on Aircraft X we observed an abnormal Number 2 engine vibration; we contacted dispatch and were told to return to ZZZ1. The return to field occurred uneventfully. We were assigned a new aircraft and re-launched for ZZZ. On the second flight; before we started our descent into ZZZ; we obtained the WX (ASOS); visibility was reported at ¼ sm (1600 RVR equivalent) and indefinite ceiling; we discussed our options and decided to execute a CAT II approach; we had a pretty strong tailwind; so the arrival occurred quite rapidly. To our surprise and due to our late arrival; we discovered that the Control Tower at ZZZ had already closed; approach control advised of low visibility at the airport as reported by another aircraft that had just landed. We set up the approach according to our established procedures (transferred control to FO; set and briefed the approach; monitored approach; etc...). The entire area around the airport showed scattered areas of patchy fog close to the ground; we could see the airport even though there was a patch of fog on top of the airport; we could see the runway lights through the fog. The CAT II approach was executed to the FAF and then the CA took controls and continued as a normal CAT I approach because visual conditions were adequate. We could see the approach lights and runway lights through the fog from the FAF. A safe landing was made and visibility on the ground was 1/2 sm. I failed to recognize the control tower was closed and that RVR reports are required for a CAT II (visibility reports only are not enough; actual RVR reports are needed) In the future I will ensure that all required items needed for the execution of a CAT II approach are operationally/available before starting this procedure.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.