Narrative:

Starting the takeoff roll the first officer pushed up the thrust levers to about 40% N1. The engines looked good so he pushed the thrust levers further up; selected to/GA (engaging the autothrottles); and said: 'set takeoff thrust.' I monitored the thrust levers advancing to only about 85% N1 and computed takeoff thrust was 87% N1. So; I pushed the thrust levers up just a little to get the needed 87%; but the N1s did not increase. I then pushed the thrust levers even further up (N1 gauge showed requested power in the low to mid 90% N1 range); but actual N1 was still at about 85% on both engines. I decided to reject the takeoff at this point; as I didn't know why the N1s would not increase past 85% or if I even had enough thrust/runway to takeoff; as we were not very far down the runway and still below V1. But; I did know that the computed numbers were now invalid with not achieving required N1s.although we were not very far down the runway when I decided to reject the takeoff; we were already above 90 knots because the autobrakes did engage. We estimated our speed at the abort to be about 100 knots. By the time I looked at the airspeed during the reject; we were already below 80 knots and decreasing. When the autobrakes engaged during the reject; they go to max braking and I know that got everyone's attention. It was amazing how quickly they stopped us. By the time the thrust reversers were spooling up; we were just about stopped. I stopped the aircraft straight ahead on the runway; told the passengers to remain seated; and that we had just aborted our takeoff due to engine indications. We then cleared the runway and checked the brake energy tables before going back to a gate. This was an insidious malfunction; as everything was looking normal and we never got any indications or lights of an engine malfunction; other than not being able to achieve a thrust setting above about 85% N1. Because it was not a classic reject condition; like what we practice for in the simulator; after it was all over; back at the gate; flows and checklists completed; I started thinking about the event and I honestly can't remember if I raised the speedbrake lever during the reject. My first officer was obviously doing the same thing because he asked me later if I raised it and I told him; 'not sure.' I hope I did; but I'm sure someone will let us know if I didn't. I definitely need to do a better personal job of running through reject procedures before every takeoff to make sure it is second nature. It was not a factor this time as we were not that fast yet and we had lots of runway left; but on a true high speed reject it is critical.since I don't know what caused the engines to not accelerate past 85% N1; I don't have any input for that. But what would have been nice; if one could from the cockpit actually look up someway in the FMC what the max airspeed you achieved during a rejected takeoff to make sure we have accurate brake energy data. I know the aircraft recorders have it; but that doesn't help us in the cockpit when we are trying to figure it brake energy and brake cooling requirements following a reject.'

Google
 

Original NASA ASRS Text

Title: A B737-700 flight crew rejected their takeoff when neither engine N1 reached the calculated takeoff thrust either via autothrottle or manual input.

Narrative: Starting the takeoff roll the First Officer pushed up the thrust levers to about 40% N1. The engines looked good so he pushed the thrust levers further up; selected TO/GA (engaging the autothrottles); and said: 'Set takeoff thrust.' I monitored the thrust levers advancing to only about 85% N1 and computed takeoff thrust was 87% N1. So; I pushed the thrust levers up just a little to get the needed 87%; but the N1s did not increase. I then pushed the thrust levers even further up (N1 gauge showed requested power in the low to mid 90% N1 range); but actual N1 was still at about 85% on both engines. I decided to reject the takeoff at this point; as I didn't know why the N1s would not increase past 85% or if I even had enough thrust/runway to takeoff; as we were not very far down the runway and still below V1. But; I did know that the computed numbers were now invalid with not achieving required N1s.Although we were not very far down the runway when I decided to reject the takeoff; we were already above 90 knots because the autobrakes did engage. We estimated our speed at the abort to be about 100 knots. By the time I looked at the airspeed during the reject; we were already below 80 knots and decreasing. When the autobrakes engaged during the reject; they go to max braking and I know that got everyone's attention. It was amazing how quickly they stopped us. By the time the thrust reversers were spooling up; we were just about stopped. I stopped the aircraft straight ahead on the runway; told the passengers to remain seated; and that we had just aborted our takeoff due to engine indications. We then cleared the runway and checked the brake energy tables before going back to a gate. This was an insidious malfunction; as everything was looking normal and we never got any indications or lights of an engine malfunction; other than not being able to achieve a thrust setting above about 85% N1. Because it was not a classic reject condition; like what we practice for in the simulator; after it was all over; back at the gate; flows and checklists completed; I started thinking about the event and I honestly can't remember if I raised the speedbrake lever during the reject. My First Officer was obviously doing the same thing because he asked me later if I raised it and I told him; 'Not sure.' I hope I did; but I'm sure someone will let us know if I didn't. I definitely need to do a better personal job of running through reject procedures before every takeoff to make sure it is second nature. It was not a factor this time as we were not that fast yet and we had lots of runway left; but on a true high speed reject it is critical.Since I don't know what caused the engines to not accelerate past 85% N1; I don't have any input for that. But what would have been nice; if one could from the cockpit actually look up someway in the FMC what the max airspeed you achieved during a rejected takeoff to make sure we have accurate brake energy data. I know the aircraft recorders have it; but that doesn't help us in the cockpit when we are trying to figure it brake energy and brake cooling requirements following a reject.'

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.