Date: 201905
Location: DEN.Airport, CO
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Other Parked pre-departure
Airspace: Class B DEN
Aircraft component: Engine Indications
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Communication Breakdown; Troubleshooting; Confusion; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft; MEL
Primary problem: MEL

Narrative: We were late arriving for what was already a tight connection and aircraft swap in DEN. Upon reviewing the release; I realized MELs were applied. After reviewing them; I was concerned about how to comply with two provisions of one; specifically how we would comply with the reduced thrust provision during climb out. I contacted the Dispatch and delayed the departure. Dispatch initially conferenced Maintenance Control; who said 'we should just use the MCP'; which was obviously not correct. Another pilot suggested manually setting the N1 bugs; but that only changes the display; not the commanded thrust. Another conferenced pilot said we wouldn't be anywhere close to max continuous on climb out; which is also not true - CON and CLB are substantially different at low altitudes; but climbing through the twenties they converge and become the same. Finally after consulting with multiple management and test pilots; it was agreed that we could use manual thrust settings to accomplish the MEL. Once we became airborne; it was obvious that this MEL was a substantial distraction. In addition to manually setting the thrust during climb so as to stay 1.1% below the N1 limit; one has to continually do math as the limit changes and reset the thrust levers; adding another task to monitor. At cruise; FMC max altitude predictions are also off; since the full rated thrust of engines is not available. This was accounted for in the flight plan weight penalties; but could catch a crew off guard if tempted to climb higher for any reason. There is no mention of this in the MEL. Later; the Chief Pilot contacted me and told me Boeing engineers said the Auto-throttles automatically compensate for this issue and there's no problem as long as Auto-throttles are engaged. We tried turning on the anti-ice in flight and it was obvious that the N1 (and therefore the Auto-throttles) adjust Max N1 for engine anti ice based on SWITCH POSITION; not the fact that the valve is locked open. I feel this MEL is at best poorly worded if it took me 25 minutes to get a verdict from the Dispatch about how to comply with it. At worst it invites multiple distractions. The airplane sat overnight at DEN with this malfunction but was not repaired. In the future; I would think twice about accepting this MEL with any challenging weather or other circumstances.Additionally; if a max thrust T/O is required above 10C; how do we know performance is assured with manually reducing T/O thrust 1.4% below what's shown on the Operations Manual?




Synopsis: B-737 Captain reported confusing instructions and procedures in a MEL.