Date: 201212
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Horizontal Stabilizer Trim
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Other / Unknown; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Human Factors

Narrative: The event began as a scheduled aircraft swap with numerous other connecting flight delays. When the aircraft was ready for departure; it was determined that 28 connecting passengers would miss our already late flight. At that time; the Agents realized that the flight wasn't properly loaded for departure without those 28 passengers; so Ramp was directed to redistribute our bags to accommodate CG considerations since this was an -800 series aircraft. By the time that had been completed and paperwork was complete; it was determined by the Agents that we would then wait for the connecting passengers from two other inbound flights after all. Once those passengers and bags arrived (27 additional passengers with baggage); a new load closeout sheet was sent to the flightdeck and the performance was calculated. We set stabilizer trim as calculated and proceeded to start engines; taxi; and takeoff. At the rotate call; I applied aft stick pressure to the yoke and noted that forces were considerably higher than anticipated; especially as I neared the aft stop. At nearly full aft stick travel of the yoke I was about to call for emergency thrust when nose strut extension finally occurred. I estimate that several hundred feet of additional takeoff roll was required to unstick from the runway. Aircraft loading and CG was clearly not what the paperwork reflected as the stick forces and elevator displacement were unacceptably high and the rotation significantly delayed as a result. I doubt the aircraft would have been flyable if an engine failure had occurred after V1 in this case. We may want to consider return to the [original] loading schedule on -800 aircraft to more clearly articulate to all parties how the aircraft is actually loaded. Additional oversight should be instituted when multiple changes to passengers; baggage; or cargo configuration have been performed on -800 series aircraft. Stabilizer trim setting incorrect due to aircraft weight and balance issue.


Second narrative: The aircraft was loaded using recently instituted loading procedures. During the loading process; the first Agent told me he had directed the ramp to move bags from one cargo bin to another. I wasn't told how many bags or how they were moved. I was then told by the Agent that since we were delayed by bag loading; the Company decided to have us wait for connecting Passengers. We originally had approximately 80 Passengers onboard; and we finally took off with 107. During the wait; a new Agent took over the flight. After the plane was boarded; the Agent determined that approximately 20 bags needed to be moved from the forward cargo compartment to the aft compartment. We recomputed the takeoff data using the new weight and balance sheet and conducted the Checklist. The aircraft trim was set in accordance with the calculations. This flight was the First Officer's leg. When I called rotation; I noticed the nose of the aircraft did not rotate normally. The aircraft was late to rotate and the First Officer was unable to establish the normal takeoff pitch. I told the First Officer to get the nose up; to which he replied that he was trying. He was able to establish a normal takeoff/climbout pitch as the airspeed increased and he added nose up trim. The aircraft loading and weight and balance computations for this flight resulted in a takeoff configuration that had less than desired controllability for rotation and takeoff. The loading computations should be reviewed to determine if there were any errors made. If there were no errors made; it may be prudent to return to the [original] boarding procedure. If I were to fly a partially loaded -800 again using single-zone loading; I will ask the Flight Attendants to provide me with a zone-by-zone passenger count. I would use this count to determine whether or not to direct the Agent to use the [original] procedure.


Synopsis: B737-800 flight crew describe last minute changes to the passenger count and bag loading that results in an inaccurate load sheet and an incorrect takeoff trim setting.