Narrative:

I was flying pilot departing mmlo on runway 31; clearance was to fly the MANTA2 departure and climb to 18;000 feet. The captain and I briefed LNAV and flch settings for the departure and I would use manual speeds once airborne to ensure we would not exceed the 200 kt airspeed limitation in mexico airspace. The previous crew had brought 500 lbs of ballast in the forward cargo compartment. We put the information in the FMS and followed company procedures to the runway. The takeoff was routine and at 1;000 ft AGL captain called 'acceleration altitude' and I called 'climb sequence'. FMS speed indicated 210 kts; then I switched to manual speed and dialed it back to 200 kts. I then noticed that the f-bug was still above our indicated speed and the stall tape was coming from the bottom of the airspeed tape towards our indicated speed. My first thought was that the captain had brought the flaps up prematurely. As the stall line approached close to the indicated speed I looked at the flap lever. The captain's hand was there but he had not moved it. The flaps were still set at 2 for takeoff. Realizing something was wrong I disengaged the autopilot and pitched slightly below the horizon and waited for the airplane to accelerate. It seemed to accelerate slowly and a moment later the autothrottles commanded the throttles reduce power. The captain and I both pushed them forward to override the auto throttles and then I disconnected the at.my immediate concern was that ground crew had moved the ballast to the aft compartment and conveyed this to the captain. The captain then called the flight attendant and had her move ten passengers to the front as soon as possible. Suspecting we may have an aft cg I did not want to fly at slower speeds and kept the climb to a shallow pitch. We were vectored around for a visual approach and a safe landing. Upon visual inspection we discovered that the ballast were in the front compartment where they belonged and all data was entered correctly. I now suspect the FMS somehow malfunctioned and would have flown us into a stall using the autopilot.

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Original NASA ASRS Text

Title: EMB-175 First Officer reported the FMS was commanding an unsafe (low) airspeed departing MMLO.

Narrative: I was flying pilot departing MMLO on Runway 31; clearance was to fly the MANTA2 departure and climb to 18;000 feet. The Captain and I briefed LNAV and FLCH settings for the departure and I would use manual speeds once airborne to ensure we would not exceed the 200 kt airspeed limitation in Mexico airspace. The previous crew had brought 500 lbs of ballast in the forward cargo compartment. We put the information in the FMS and followed company procedures to the runway. The takeoff was routine and at 1;000 ft AGL Captain called 'Acceleration Altitude' and I called 'Climb Sequence'. FMS speed indicated 210 kts; then I switched to manual speed and dialed it back to 200 kts. I then noticed that the F-bug was still above our indicated speed and the stall tape was coming from the bottom of the airspeed tape towards our indicated speed. My first thought was that the Captain had brought the flaps up prematurely. As the stall line approached close to the indicated speed I looked at the flap lever. The Captain's hand was there but he had not moved it. The flaps were still set at 2 for takeoff. Realizing something was wrong I disengaged the autopilot and pitched slightly below the horizon and waited for the airplane to accelerate. It seemed to accelerate slowly and a moment later the autothrottles commanded the throttles reduce power. The Captain and I both pushed them forward to override the auto throttles and then I disconnected the AT.My immediate concern was that ground crew had moved the ballast to the aft compartment and conveyed this to the Captain. The Captain then called the FA and had her move ten passengers to the front ASAP. Suspecting we may have an aft CG I did not want to fly at slower speeds and kept the climb to a shallow pitch. We were vectored around for a visual approach and a safe landing. Upon visual inspection we discovered that the ballast were in the front compartment where they belonged and all data was entered correctly. I now suspect the FMS somehow malfunctioned and would have flown us into a stall using the autopilot.

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.