B737-800
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Aircraft; Human Factors
I was assigned [a] flight to LGA. This was the first leg of a two-day trip for me. For the First Officer; this particular flight was the last leg on the second day of a three-day trip. As I pulled up the flight plan I saw that there were five potential MEL items to review. When I arrived at the aircraft; the log book was not on the flight deck or on the jet bridge. I called maintenance and was informed that items were being looked at prior to departure and the log book would be returned when complete. While waiting; I began to review MEL items listed on the flight plan ... auto throttles; two Proximity Switch Electronic Unit (PSEU) related items; HUD/restriction to Cat 1; and First Officer radio altimeter. I focused initially on the PSEU having just had a PSEU related issue a few days prior. When the log book arrived at the airplane I saw that the procedures for the two PSEU items that were required before each flight had been documented in the log book. As I continued to review the other active MEL items; the First Officer arrived and began setting up the flight deck. He noted a #2 thrust reverser light on. I made a new entry in the log book and contacted maintenance. Additionally; it was discovered that the brake pressure indication on the instrument panel was bleeding down at an excessive rate. At this time; maintenance arrived and my focus on the existing MEL items changed to a focus on the newly discovered discrepancies. For the next 40-50 minutes we worked with two maintenance technicians doing multiple cycles of the thrust reversers and manually applying brakes with hydraulic pumps on and off.  Both new discrepancies were corrected and the flight departed about one hour late. The First Officer had not flown that day so he preferred to fly the leg to LGA. Taxi; takeoff and cruise to LGA were all uneventful. Upon arrival at LGA we were assigned the ILS CAT 1 to Runway 4. The aircraft was MEL restricted to CAT 1. We were given a vector to intercept the localizer at a point above glide path. We were then cleared for the approach. After localizer capture; the First Officer noted that he no longer had the roll command portion of his flight director. He still had the pitch command bar and the glideslope and localizer diamonds on the PFD. The Captain's FD continued to function normally. We briefly discussed what we were seeing and we both examined possible options with the approach. As we were doing so; we confirmed through the captains PFD; the standby indicator; and the localizer diamond on the FO's PFD that we were right on the localizer. As we continued to assess the approach; the aircraft broke out around 800 feet AGL and the First Officer flew the remainder of the approach visually to an uneventful landing. After landing; we discussed what we encountered during the approach but did not come up with a suitable explanation. It was later that evening and the next morning as we discussed the event further; dug deeper into the MEL and the Operations Manual 1 and 2 and retraced our actions from the day prior that we discovered what had occurred. While reviewing the five active MEL items; we were distracted by two new maintenance items and failed to review the final item; the FO radio altimeter. Had we reviewed this item we would have discovered pretty much what had occurred. At localizer and glideslope capture the flight director would go away on the side with the inoperative radio altimeter. On our approach the roll portion of the command bars went away. The pitch bar may have eventually gone away but at that point we were focused outside for the visual portion of the approach. Being a CAT 1 approach; we did not discuss the loss of aircraft or ground based equipment; just go-around procedures in general.With five MEL items to review; once the detractors started entering into the equation; it may have proved helpful to physically check off the MEL items on the flight plan as they were reviewed. It couldhave helped to remind me that I hadn't made it to the last item on the list once the new items were resolved. Also; in the future; I plan to begin making notes on the flight plan next to the MEL items. The notes would be a synopsis and quick reference of systems/procedures impacted by each MEL item.
I was unable to review the logbook and MEL personally before departure and felt that the Captain's and Maintenance briefs were extensive. And that is where the error occured. Captain feels that he either misread or missed the part about flight directors and autothrottles (they were broken anyway) under the MEL for Radio Altimeter; and I did not crosscheck all this work (granted - it was a lot). This led to the event.
B737-800 flight crew reported the loss of the First Officer's roll command on the flight director during an approach. Later they discovered that they had failed to note equipment limitations during the preflight MEL review.