Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 362; Flight Crew Type 3000
Deviation / Discrepancy - Procedural Weight And Balance; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control
Human Factors
Upon departure from ZZZ; the aircraft did not want to rotate. With a reasonably light load; the [Weight and Balance Calculation] gave us flaps 15 with a trim setting of roughly 6.0. I thought it was strange that we were that light and it was commanding a flaps 15 takeoff. The First Officer and I discussed it and thought it was simply due to the [Weight and Balance] system commanding a very reduced thrust. I also thought it was kind of strange that we didn't have a Zone count; but the Operations Agent said it was not required. All bags were loaded in the front cargo and; as it turned out; about 80 of the passengers were in Zone A. We did not know about the passenger loading until climbout; when I queried the Flight Attendant about seating.He confirmed all passengers were in Zone A. I had him redistribute the passengers among the cabin. During the takeoff roll; the First Officer was Pilot Flying; I called V1 and rotate. He pulled back but nothing happened. He pulled further until the yoke was nearly at full travel and the aircraft reluctantly rotated. He proceeded to trim to nearly 10 units of nose up trim in order to relieve some of the required back pressure. During first segment climb; with high AOA; we experienced uncommanded roll and pitch reminiscent of a wake turbulence encounter; but there was no preceding aircraft. The First Officer lowered the nose and the event stopped. The rest of the flight was uneventful and I requested a loading audit while enroute. When something seems strange; there may be a reason why.A loading error of this magnitude could easily be deadly in a short airport like ZZZ. By the time we realized the problem; had we been slightly heavier and tried to reject; we would been a giant fireball in the street.A Zone count should be mandatory for all 737-800 aircraft.There MAY be a glitch in the [Weight and Balance] system with light loads. It needs to be looked at.
B737-800 Captain reported weight and balance was out of limits; resulting in aircraft control issue during takeoff.