Date: 201905
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZZ
Aircraft component: Brake System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: Other Takeoff Roll
Result: Flight Crew Regained Aircraft Control; Flight Crew Rejected Takeoff; Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Aircraft pulled to left during takeoff roll. Rejected Takeoff. Returned to hardstand for maintenance to investigate. Normal taxi to Runway XL for takeoff. Wind 100/5; temperature 28C. Engine thrust was set for takeoff; with normal acceleration and stabilization. During takeoff roll; PF (Pilot Flying) needed to apply increasing right rudder pedal pressure to counteract the aircraft's tendency to pull to the left. At approximately 50 kts the PF was unable to maintain runway centerline. The PM (Pilot Monitoring) assumed control of the aircraft and rejected the takeoff. At approximately the same time the pull to the left ceased; allowing the aircraft to be realigned with the runway and track straight ahead. Maximum airspeed was approximately 70 kts. Aircraft was taxied to a hardstand. Maintenance personnel examined all tires for wear or damage; checked all four main wheels for proper rotation; and bled all brake lines numerous times; noting a significant amount of air in each system. Tire #4 was replaced. CA (Captain) and FO (First Officer) both noticed that the brakes on tire #1 were significantly warmer than those on all other tires.This rejected takeoff occurred on a relatively warm day; at a high elevation airport; after a relatively short turnaround. It is the opinion of the CA and the FO that one or more brakes on the left truck were binding during the initial takeoff roll; but then released as the takeoff was being rejected.As FO and now CA on the 737-800; I have more than X000 hours in this aircraft. I have never experienced anything like this; nor have I heard of it. If the occurrence was due to thermal issues (the combination of temperature; elevation; and short turnaround time); as in if this problem is a known issue; it would have been nice to have had the knowledge to anticipate the possibility of a problem. At a higher airspeed; with a slower reaction by the crew; or with a compounding thrust asymmetry; this event could have easily led to a runway excursion.


Second narrative: Take-off roll at ZZZZ; winds negligible; surface new and dry no grooves or wear; engine thrust symmetrical with TOGA (Takeoff Go Around) selected aircraft pulled left with increasing right rudder application with no response from drifting aircraft. At approximately 60 knots with heavy right rudder aircraft responded with more side loading than desired. Articulated to Captain that something wasn't right with nose wheel control. Captain aborted takeoff and we exited the runway with very little braking at 70 kts or less. Significant brake chatter during taxi in. Maintenance actions appear to have solved a dragging #1 brake assembly.


Synopsis: B737-800 flight crew reported experiencing a brake malfunction during takeoff roll.