Date: 201504
Location: ZZZ.ARTCC, US
Flight conditions: Mixed
Light: Daylight
Aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Brake System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Contributing factors: Company Policy; Manuals; Procedure
Primary problem: Ambiguous

Narrative: I operated flight from Airport ZZZ to ZZZ1 as Captain. In ZZZ while doing my walk-around after the flight up I noticed the left main-gear brake assembly leaking hydraulic fluid. The fluid was pooling on the asphalt. I notified MAINT control and dispatch. Local MAINT was sent out. It was determined to indeed be a brake fluid leak. MAINT isolated the left main gear brake assembly and applied MEL 32-XX.  That deferral allows us to defer the brake assembly on one wheel and requires the performance data to be adjusted for that deferred item.  I requested a new TLR (Takeoff/Landing Report) from [dispatch]. After receiving the TLR I noticed that indeed the deferred brake assembly was accounted for in the remarks section. The TLR training handbook says that applicable performance penalties are applied to the performance data as long as it is noted in the remarks section.So we departed ZZZ thinking all was ok. Halfway to ZZZ1 I started revisiting the ZZZ1 weather in order to determine which runway would be most suitable for landing. Winds preferred runway XY L and R. Knowing that the XYs are shorter than [RWY] XZ I reviewed the landing data for ZZZ1 to make sure the XYs were sufficient.The TLR indicated that all runways were suitable; yet when looking at it closer I noticed that the remarks section for the Landing data said 'none' as if there were no MEL items that might compromise or deteriorate our landing performance.  Knowing that the brake assembly of the left inboard main gear was INOP I knew that the MEL should have caused a performance penalty to be applied. However.....since the landing data remarks-section said 'none' no performance penalty was applied.  I contacted [dispatch] over commercial radio to get the landing performance data as required per FAR 121.195 with respect to the applied MEL. [Dispatch] informed me that no landing performance data was available for said MEL. Not knowing how much runway I might need I decided to [notify ATC of the situation] and requested vehicles to stand-by upon landing in ZZZ1.  The landing was uneventful and I slowed the airplane to exit.It puzzles me how we can have performance penalties for takeoff but not for landing as this MEL surely was limiting our braking-performance for landing distance calculation purposes. Obviously we did not have all the data required by FAR 121.195 incorporated into our NavTech system.  Also; knowing that we did not have the landing data available to account for this MEL I wish that the dispatcher would have told the crew before the flight and not during the flight. Just because something is not available does not mean we can ignore it.




Synopsis: MD-80 Captain reported he was dispatched with a main wheel brake deferred inoperative and was given takeoff weights that accounted for the deferral. However; the issue was not addressed in the landing data.