B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Troubleshooting; Human-Machine Interface; Workload; Distraction; Confusion
Aircraft Equipment Problem Critical; Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Clearance; Flight Deck / Cabin / Aircraft Event Other / Unknown
General Maintenance Action
Human Factors; Aircraft; Procedure
I was the pilot not flying on this westbound transatlantic leg. After push back we started the engines and noticed both left and right EEC INOP lights on the EICAS display. Indeed; both EEC INOP lights were illuminated on the switches with the switches in the ON position. We stopped the aircraft to consult the MEL. As per MEL instruction both EECs are crew placardable. We placarded the EECs and proceeded to the runway for takeoff. We discussed the use of autothrottles on takeoff and departure. We elected to use the autothrottles in accordance with the MEL. The takeoff was normal; LNAV was selected at 400; and the left autopilot was engaged shortly thereafter. At 1;900 FT; in accordance with the noise abatement procedure the pilot flying called for VNAV. VNAV was selected and CLB power noted on the EICAS display. However; the power levers did not retard to climb power. At 3;400 FT the aircraft did not accelerate for cleanup and the pilot flying engaged FLCH. FLCH; although illuminated and engaged; seemed to have no effect on the aircraft (Note: the VNAV light was also illuminated at the same time as FLCH; but neither system was directing autoflight performance). Next; the pilot flying selected [and was able to utilize VS to command] the aircraft to accelerate for cleanup. (Note: at this point all three climb modes were illuminated on the mode control panel: VNAV; FLCH and V/S). During our initial turn on the SID the aircraft rolled out on an approximate heading of 280 with LNAV engaged. Because of the distraction of the various climb modes and acceleration issues we began to fly wide of the SID track. Simultaneously; the pilot flying clicked off the autopilot and autothrottles and began a manual turn back; back to track as ATC called and gave us instructions to stop our climb at FL100 and then gave us a heading of 240 toward [the next waypoint]. LNAV was reengaged once on course and the flight was continued with autothrottle off. Upon arrival at our destination the engines were secured. At this point many warning horns sounded and lights began to illuminate. When the mechanic arrived at the gate he told us the EEC INOP issue; warning horns; and autothrottle problems were caused by a single switch that was activated in the cockpit. This switch is located below the right sidewall in the cockpit. He told us that the switch was a 'maintenance only' switch and that it had apparently been activated some time prior to our flight. When he closed the switch; the warning horns stopped; the EEC INOP lights extinguished and I assume the autothrottle was restored. That [position of that] one switch caused a great deal of distraction at a critical time in the flight and may have lead to a mishap. Although; the mechanic immediately knew what the problem was; no mention of that switch was made in the MEL or QRH. There should be a note in both the MEL and QRH that if BOTH EEC INOP lights are illuminated at the same time check the red guarded switch on the right sidewall.
At this point; VNAV; FLCH; and V/S all indicated engaged. The aircraft; on autopilot; began a left 180 degree turn per the SID but the aircraft rolled out 50 degrees short of the required heading to our the next waypoint. Because of the distraction stemming from the climb/auto throttle issues we were experiencing; we were late noticing we had not completed the turn. ATC called us; instructing us to stop our climb and gave us a heading towards [the next waypoint]; and from there we proceeded on course and completed the flight with the auto throttles off.
An improperly positioned 'maintenance only' switch resulted in multiple warning lights and compromised autothrottle/autoflight functionality for a B767-300ER flight crew while conducting a complex SID from an overseas airport prior to an Atlantic crossing.