Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 125; Flight Crew Total 19500; Flight Crew Type 7500
Situational Awareness; Confusion; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Aircraft; Human Factors
During preflight the First Officer (FO) informed me that we would be good to use D2 for our takeoff power setting. I asked how big a buffer that gave us and I remember figuring that to be 8000 LBs but after checking later turned out to be more like 13;000 LBs.  In any case I took a conservative approach and decided I wanted even more power so I told the FO to use a reduced off of Max setting; which would give us more power. The FO then set the thrust management computer; TMC; to a reduced setting; which I believed to be a reduced off of max setting. During taxi out; as it was my leg; I briefed that we were using a reduced off of max power for our takeoff power setting. After being cleared for takeoff and setting the autothrottles for takeoff; it seemed to me like we were not getting a normal power increase and I checked the autothrottle to make sure it had increased to the selected takeoff power setting and it had. The takeoff run seemed longer than normal but we finally reached takeoff speed and the aircraft climbed out. After clean up and an increase in speed I looked over and saw that the TMC was in the D2 mode. I asked the FO if he had changed us to the D2 mode after takeoff and the FO stated no. I asked for max power for the rest of the climb. I then understood and told the FO that we had taken off in the D2 mode.    Initially I was not too concerned as I knew we were good to use D2 for takeoff and that the takeoff had been successful; but later in cruise when I had time to reflect; I realized that we had not only used D2 for takeoff but that we had reduced off of D2; which would explain the lackluster takeoff performance. After rechecking it turned out that our power setting was for 40;000 LBs less than we needed for takeoff.  In trying to figure out how this could happen; the FO told me that he always set the TMC to D2 whenever it would work because most captains were ok with using D2 for takeoff. I told the FO that it has been my understanding that FOs do not set D2 on the TMC until after the captain approved its use.  In our case it seems that the TMC was not set back to Max power even after the reduced setting was set.  In any case we both understood that we were supposed to use a reduced off of max setting; and that we both missed that the TMC was improperly set.
Our Takeoff weight was 324.7. I told the captain we were good for D2 and selected D2. He asked me what D2 was? I informed him D2 was 338.3 for runway 26 L. Our takeoff weight was 324.7 that gave us a buffer of 13.6. The Captain decided he wanted Assumed off of Max. I assumed at 48 degrees which was good for a weight of 347.8 and I rolled the dial to 48 degrees. On takeoff he asked me to set Thrust we both noticed the thrust did not seem normal. We both verified the auto throttles were armed and I also checked for the throttle Arm notification. The takeoff roll was unusually long but we lifted off at V1 and climbed out without any problems. On climb out the captain noticed that D2 was set for climbout and asked me if I had changed anything. It was not until cruise that the Captain realized I had never deselected D2 for takeoff and we had in fact assumed off of D2 not Max. In order to stop this from happening again we discussed how we should confirm D2 before selecting it.
The crew of a B767-300 reports inadvertently taking off with a thrust setting much lower than required for the actual aircraft weight. The First Officer had set D2 in the Thrust Management Computer (TMC) and the Captain decided he preferred the assumed temperature method of de-rating thrust; but the D2 was never removed from the TMC.