Date: 201605
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dawn
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Aircraft component: Exterior Pax/Crew Door
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Rejected Takeoff; Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: During takeoff roll; just after call of 100 kts; master caution light came on. I noted the doors light on F/O system annunciator panel was lit. At that moment it occurred to me that it could be cargo door and I had an experience many years ago where I watched a DC-8 on downwind at Miami Int'l with its cargo door open losing cargo out the door. That split second thought influenced my decision to abort as well as the fact that [our runway] was 11000 ft and we could still [easily] come to a stop in the distance remaining.


Second narrative: We were cleared for takeoff. Weight was about 163.5K; Flaps 5; reduced; V1 was 155. Normal roll through 100kts; but shortly after the '100 knot' call; probably around 110kts; I noticed the Master Caution with DOORS lit on the system annunciator light panel. I looked up to the overhead panel and noticed the FWD ENTRY door light on. As I was glancing up at the overhead panel; the Captain initiated a rejected takeoff. I then glanced at the airspeed and noted 121kts. I ensured the RTO procedures were completed by the Captain and then informed Tower that we were rejecting the takeoff. Tower did not understand my first call; so I had to repeat it to them. I then focused on our deceleration rate versus runway remaining. By the 80kt call; it was clear that there was more than enough runway remaining and were comfortably at taxi speed by the 1000 ft mark. I do not recall when the Captain began manual braking and easing our deceleration rate. After checking with the Captain; I let Tower know we would exit at the end of the runway. After clearing the runway; I made a PA asking folks to remain seated and explained that a caution light during the takeoff roll had caused us to discontinue the takeoff. I then ran through the Rejected Takeoff checklist in the QRH and completed the after landing flow as we slowly taxied on the parallel. I then referred to the brake cooling chart and noted that at our weight; and a reject speed of 120kts put us in the 'Caution' range which required the tires/fuse plugs to be inspected after a 60 min cooling time. As we returned to the gate; I talked to the FA at 1L; explained why we rejected the TO; and had her check the handle. I heard a slight clunk in the background and she informed me that the handle was not completely down. I then explained the situation to ops and maintenance on the radio as we taxied back to the gate. The Captain briefed the Maintenance Technician and entered the RTO into the maintenance logbook. Maintenance used conditioned air to aid in cooling the brakes. After about 70min; maintenance signed off the logbook and we blocked out to continue the flight with no further issues. The Captains RTO brief prior to the flight was consistent with SOP.


Synopsis: B737 flight crew reported the Captain chose to reject the takeoff at approximately 110 kts when a door warning light was illuminated.