B747-400
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Confusion; Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Weight And Balance
Flight Crew Rejected Takeoff; Flight Crew Returned To Gate
Aircraft
During preflight cockpit setup everything was normal with the exception of the FMC appearing slow and fix page missing the time and altitude prediction entry line; 6R key. The Technician was onboard and thought it was a cache issue; did an FMC reset; and it worked normally. During the before start procedure I noted that 25.3% CG gave us 3.6 units of trim and this was close to the forward limit of the green band. I left a slight bias toward the green so I set maybe 3.7 units. I called this to the Captain's attention; told him I didn't have the expanded green band and asked if he had one on his trim indication. He did not. We were in the greed band but near the forward limit. Taxi from SE Cargo to Runway 28R was normal. The start of the takeoff roll was normal; thrust set by 80 kts. Shortly after 80 as I was scanning EICAS I noticed the STAB TRIM CONFIG warning flash a couple times and clear. The Captain gestured that he saw it too. This was followed by a steady STAB TRIM CONFIG; Master Warning Light and aural warning. The Captain executed the [Rejected Takeoff] procedure and we stopped on the runway. The speed was in the 100 to 120 range.I didn't get the exact speed because I glanced at the EICAS Warning message and the Captain initiated the [Rejected Takeoff] at the same time. The FMC Speeds were 143-148-158. We stopped just past taxiway T and taxied clear of the runway on P4 as instructed by the Tower. During taxi to gate the highest Brake Temperature Monitoring System indication was a 5 on the number 2 brake. During taxi to parking we also observed that a CG of 25.3% was now giving 4.5 units of trim. The Captain and I discussed this and thought it was strange. While parked at the stand we reentered the performance and it was now calculating 4.5 units of trim with 25.3% CG. I entered both 71 tons and 68 tons; the block out fuel and return fuel to see if it made a difference on the trim and it did not.Duty pilot had a recollection of this happening before but I don't know any details. Maintenance could not find any discrepancy and cleared the airplane to return to service.
B747-400 First Officer reported a CG% out of limits warning during the takeoff roll and a resulting rejected takeoff.