B737 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Type 1832
Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury
General Physical Injury / Incapacitation
Human Factors; Aircraft
B737 systems manual clearly say that flight deck PA system overrides other communication in back. That is incorrect. When using the small black hand mike on the center console you do NOT override the flight attendants making a PA announcement. The F/As (Flight Attendants) were making a PA when the F/O (First Officer) announced 'Flight Attendants Be Seated'. Therefore; they did not hear the announcement; and were not ready for takeoff.
While on taxi out on; we were number 1; and did the final items. I used the black hand mic at the aft center console to make my announcement for the flight attendants to be seated. I did my flow and then accomplished the checklist. I heard the flight attendants using the PA to make announcements through the flight deck door. I pushed the PA button on my com console and verified they were still on the PA. I told the Captain; and he acknowledged this; and said he will slow the taxi to give them time to finish. We were shortly given takeoff clearance. I verified the flight attendants were no longer on the PA; which they weren't; and the takeoff was made. Passing through 13000 feet; the lead FA (Flight Attendant) called us and said she never heard the PA announcement to be seated for takeoff. She also stated that that there were FAs not seated for the takeoff since they didn't hear the announcement and that was a FAR violation. Another FA was injured while try to stop a rolling beverage cart with his foot. This injury may not be directly resultant from the PA announcement; but was influenced by it.
B737 flight crew reported Flight Attendants were not seated for takeoff because the flight deck PA announcement did not override the cabin PA system.