B737 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 19500
Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Departure Airport; Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
On arrival at the gate; the inbound crew (from 2243-12) informed us that they had experienced a DISPLAY SOURCE 2 indication during their flight. They made an ELB entry documenting this failure. They briefed us further on several details. First; the DISPLAY SOURCE 2 indication had come on early in the flight; then disappeared; and then re-occurred about midway into their flight. For the remainder of their flight (approx. 2 hours); the B autopilot was failed; and the FO (First Officer's) Airspeed and Altitude indications were blank. (These potential flight deck effects are referred to in the DISPLAY SOURCE non-normal procedure. FM 2.100.28) The B Autopilot; FO Airspeed; and FO Altitude indications remained failed until after landing; at which time indications returned to normal. I do not know if the inbound crew provided these details to SFOMM or not.We delayed boarding our outbound flight to allow Maintenance to assess the problem. We advised ZZZ Maintenance of the additional details (autopilot B; airspeed and altitude indicator failures) that the inbound crew had provided to us. ZZZ Maintenance reviewed the fault history in the Maintenance function accessible via the FMC keyboard. The historical information did show an intermittent fault on the inbound leg. After consultations within ZZZ Maintenance and between ZZZ Maintenance and [Technical Support Maintenance Control]; ZZZ Maintenance did several Built-in-Test procedures on the #2 DEU; the display units (DUs); and other related systems. All of these BITE tests conducted on the ground in ZZZ showed a PASS. I initiated a phone call with Dispatch and [Technical Support Maintenance Control]. [Technical Support Maintenance Control] indicated that; with all of the Maintenance procedures that they had followed; that they would determine that the airplane was OK for service. These tests were not showing any current faults; all tests were showing a PASS. [Technical Support Maintenance Control] further offered that single (non-repeating) occurrences of such faults were; in his experience; relatively common; and that a re-occurrence after passing all BITE testing was; in his opinion; very unlikely. I had previously discussed a contingency plan with my FO. I felt that; in the unlikely event that the failure re-occurred in the early portion of the flight; I would be strongly inclined to return to ZZZ; given the effects of such a failure on our instruments and autopilots. The first officer agreed. I now had the same discussion with Dispatch and [Technical Support Maintenance Control]; namely; that if (considered unlikely by [Technical Support Maintenance Control]) the failure re-occurred early in the flight; we would likely return to ZZZ. This was a Class 2; ETOPS flight at night. Dispatch and [Technical Support Maintenance Control] indicated that they understood. Both Dispatch and [Technical Support Maintenance Control] indicated that they were comfortable with operating the flight with this aircraft. Maintenance released the airplane for service; we boarded and departed.On takeoff at approximately 2000 ft.; the FO altitude and airspeed indicators went blank with failure flags. While I am not certain about this (it was a high workload time in the flight); I believe I also saw that his FMAs were blank. After about 20 seconds; the FO indications returned to normal.It was now apparent to me that whatever failure had occurred on the previous leg was present on our flight. Thus; as I had discussed with the FO; Dispatch; and [Technical Support Maintenance Control]; I felt that the prudent course of action was to return to ZZZ rather than risk losing the FO instruments after entering oceanic airspace. We initiated a phone patch with Dispatch and [Technical Support Maintenance Control]; and advised them of the repeat failure. We added the [Chief Pilot] to the conversation for consultation. We determined that we would return to ZZZ. We consulted the flight manual and FOM regarding the overweight landing. We decided to declare an emergency due to the overweight landing and the slight risk of hot brakes. Dispatch provided the necessary landing data. We briefed the Flight Attendants and then the passengers. Landing was uneventful. We used minimum braking and maximum reverser thrust. After landing; the ZZZ Fire Department measured our brake temps; they were normal. We taxied to the gate.
The previous crew stated that the FO (First Officer's) airspeed and altitude went away during flight and the SPD and ALT flags appeared during the last part of their flight. Our Captain called Maintenance to check the displays. The technician ran a BITE test and the system checked OK and the error could not be duplicated. The test did show the indications of the intermittent failure from the previous flight. The Captain called [Technical Support Maintenance Control] and to discuss a better solution. The Technician came back and tried a different procedure. He restarted the IRS and ran another BITE test. The system passed the test again and [Technical Support Maintenance Control] said that we were cleared to take the aircraft. The Captain and I discussed this and decided to take the aircraft; but both agreed if we got the same indications that we would air return to ZZZ; since we were not comfortable taking that over oceanic airspace. Shortly after takeoff; at approximately 2;000 ft. MSL; the FO airspeed and altitude display went blank and the SPD and ALT flags appeared for approximately 20 seconds. We coordinated a hold and a climb to FL240 to discuss with [Technical Support Maintenance Control]; Dispatch; and the [Chief Pilot]. We decided to return to ZZZ. Our landing weight was going to be 173K lbs.; so we read through the OVERWEIGHT LANDING section in Ch. 5 of the FM. The Captain decided to [Request Priority Handling] because we were landing heavy and to have the crash crew available if needed. We requested landing data for Runway XXL for 173K lbs. and Flaps 30. The Captain landing the aircraft normally. After exiting the runway; we requested the crash truck to check for hot brakes. They checked and said brake temperature was OK. We taxied back to the gate for a normal shutdown.
B737 flight crew reported an air turn back after multiple instrument failures on takeoff.