Date: 201506
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Takeoff / Launch
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
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
Primary problem: Human Factors

Narrative: MEL had cargo restriction ...no fwd cargo.[Computer] had 2;900 lbs showing FWD.  I called load agent to ensure no cargo would be loaded forward the agent said they could extend the Envelope to accommodate the .1 aft cg problem.  I wound up with 3;400 lbs in the aft cargo.[Computer] called for reduced power T/O.I decided to go max power 5' flaps.The aircraft was longitudinally unstable after takeoff.  It required a lot of fwd then aft trim continuously.Cruise was uneventful.During the practice CAT 111 an extraordinary amount of force and movement was required to keep the HUD presentation within the proper parameters to continue the approach.At 200 feet 'No A111' Illuminated. The approach was continued.The landing was uneventful.I did not know the CG envelope could be extended to accommodate a CG problem however I strongly recommend against this practice if what I experienced is an example of extending the envelope.


Second narrative: During aircraft pre-flight; maintenance had possession of the log book. Approximately ten minutes prior to departure; maintenance brought the logbook to the cockpit.Upon review of the logbook; the captain determined that an MEL existed deferring the forward baggage compartment. As a condition of the MEL; no baggage was allowed to be loaded in the forward compartment. The Captain then reviewed the [performance calculations] printout and informed me that load planning had showed over 2;000 pounds to be loaded in the forward baggage compartment.While I contacted the station operations to insure that the crew chief knew of the situation; the Captain contacted load planning.Operations informed me that the crew chief was aware of the limitations and would not load any baggage into the forward compartment. I relayed that information to the captain.When the captain got off the phone to load planning; he told me that they were aware of the situation and would provide a new TPS showing no baggage in the forward compartment; which they later did. At the same time; the Captain voiced his concern that the load planning agent told him that 'Due to the fact that the aircraft was within .1 to .2% of the aft operating envelope'; they were required to utilize the 'extended C.G. envelope'.The Captain then asked me if I had ever heard of something like that on the 737. I told him that I wasn't aware of anything like that; but I wasn't sure. (In hindsight; I recall certain aircraft with an extended C.G. envelope; but I don't recall the exact envelope for the 737.)Prior to pushback from the gate; the captain wanted to insure that I was comfortable with us departing with the aircraft in that configuration. After reviewing all available weight and balance information; I indicated to him that I was.We were originally planning a takeoff utilizing 'standard power'. Considering the C.G. issue and runway conditions; the captain elected to go 'maximum power' for the de-rated thrust setting. I believe it was 22k. I agreed. Additionally; when ATC asked for an intersection takeoff; I requested 'full length'. The captain indicated to me that he was fine with that thinking.During rotation; we both noted a fairly pronounced 'wallowing' of the aircraft. Upon climbout; the Captain Pilot Flying (PF) verbally noted the reaction of the aircraft during rotation. I affirmed his observations with my own. He engaged the autopilot and we proceeded uneventfully.On descent; the captain indicated that he would like to log a CAT III approach. He fully briefed the approach to 18 right and we set up the cockpit appropriately.Once on approach; the autopilot was disconnected. Immediately; I noticed a distinct difference in the feel of the aircraft. The captain (PF) indicated his concern that the airplane felt pitch sensitive. I agreed. At approximately 200 feet AGL; we got a 'NO A-III' amber warning on the annunciator panel. The captain landed the aircraft firmly; but normally.After landing; the captain asked whether we had excessive deviation from the localizer or glideslope. I told him that I didn't see any reason for the NO A-III warning. The glideslope indication in the cockpit was fluctuating; but as far as I knew; it was never out of CAT III parameters. It may have been from the aircraft being pitch sensitive. Or; it may have been an anomaly from the ground equipment. (Or both) There was no protection in the Cat III critical area during our approach and landing.Needless to say; the flight landed without incident. However; our concern was whether or not the aircraft was being inadvertently flown with the center of gravity out of limits by the flight crew.While being the pilot monitoring; I could not testify to the control feel of the aircraft. However; it was my observation thatthe airplane could have possibly been suffering from some degree of neutral dynamic instability.Obviously in this situation; there is a need forbetter communication between maintenance control and load planning. Additionally; if the forward baggage compartment is unusable; perhaps we might recommend utilizing actual bag weights rather than the estimated weights we use in normal operations.


Synopsis: B737-800 flight crew reported noticing longitudinal instability after takeoff and on approach after being advised by load planning they were loaded using 'extended CG envelope' procedures.