Date: 201703
Local time of day: 1201-1800
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: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Pneumatic Ducting
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: [After departure] Tail Compartment Overheat Light illuminated passing FL250; while I was giving the PA concerning seatbelt protocol; arrival time; and destination weather. It was the FO's leg. He accomplished the memory items and light extinguished. We [advised ATC] and requested clearance to return to [departure airport] for a visual approach. First Officer has 10;000 Hours in the MD-80; had him continue to fly and talk to ATC while I completed the QRH procedures; briefed the Flight Attendants; coordinated with Dispatch; and obtained a Landing Data Performance Assessment for an Overweight Landing. Started the Before Landing Checklist passing 16;000 feet and asked the FO what he had for the current altimeter setting thinking he had obtained one from ATC. However; he inadvertently gave the setting from the ACARS ATIS print out for [destination] that had already been put on the center pedestal. The erroneous setting resulted in a subsequent momentary deviation from an assigned ATC altitude. ATC advised they showed us below our assigned altitude of 3000 feet and told us check our altimeter setting. We were at 2600 feet with the correct altimeter setting; and immediately corrected back to 3000 feet. Coordinated for Single Frequency Approach and CRF to thermal scan aircraft after landing. FO executed excellent approach and landing. Continued to the gate after CFR inspection. Entered Overweight Landing entry and Tail Comp Overheat discrepancy in the AML. Contributing factors to this event include human error regarding the source of the correct altimeter setting. I thought the FO had obtained the correct altimeter setting from ATC while I was accomplishing other tasks. The FO thought he had the correct altimeter setting from the ACARS ATIS print out.I would avoid this event by not allowing the non-normal events of an inflight anomaly detract from normal procedures. I would get another current ACARS ATIS print out; and ensure receipt of the ATIS information was coordinated with ATC; like I do on every flight.


Second narrative: [Report narrative contained no additional information.]


Synopsis: MD-80 flight crew reported returning to the departure airport after receiving a tail compartment overheat light. They mistakenly descended below their assigned altitude due to using the destination altimeter setting.