Date: 201410
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; General Declared Emergency
Contributing factors: Aircraft; Manuals
Primary problem: Manuals

Narrative: After departure I heard the Lavatory Smoke Alarm going off through the closed door. Shortly thereafter the Lead flight attendant called up and said that they had a Aft Lav Smoke Alarm on both sides. As the pilot not flying (PNF) I [advised] ATC and requested radar vectors back to the field. Then I grabbed the QRH. The Captain then confirmed that he had the plane and the radios and instructed me to run the QRH checklist. I ran checklist for the Lavatory Smoke Alarm. After I completed the checklist I returned to my duties as PNF ran the descent/approach/landing checklist and we landed uneventfully. The Captain decided to return to the gate for deplaning since the flight attendants could not verify a fire and an evacuation on the runway might have caused more injuries than deplaning at the gate. I agreed with that assessment. Mechanical malfunctions happen so there is not much that can be done preemptively to avoid that. What caused the Lav Smoke alarm to go off is presently unclear. The flight attendants and some passengers confirmed that they saw smoke/haze in the area concerned; yet an active fire could not be confirmed. Also; it did not get worse; but rather dissipated slowly. The Lav Smoke alarm remained on until we got to the gate though. I applaud the flight attendants for staying calm and relaying that to the passengers. As far as I know no injuries were reported. What I am a little concerned about is the QRH checklist that deals with the Lavatory Smoke Alarm. It directs the crew to pull a lot of CB's. Those CB's are located behind the Captains seat. I could not reach those breakers from my seat (due to phase of flight and impending landing); so the Captain had to pull them; despite him being the pilot flying and operating the radios. For this checklist it would be better to have the controls transferred to the First Officer so that the Captain can locate and pull the CB's without having to fly and call at the same time. In addition; the checklist directed us to pull CB for the Call System. I do not know how that CB interacts with the Lavatory Smoke Alarm; but what it did do is disable our communication with the flight attendants as our call-button was rendered inop after pulling that breaker. All communication with the flight attendants was done by knocking and yelling through the door once those CB's were pulled. Though possible it was not the best solution. But since it was part of the checklist we did not undo that step.




Synopsis: MD-80 First Officer reported that when they ran the QRH for Lavatory Smoke Alarm; one of the steps called for pulling circuit breakers that disabled communication with the cabin.