Simulator experiment and real world implementation of reduced climb thrust fuel saving procedure

The current aircraft climb to the cruise altitude by using maximum climb thrust, which is so-called the maximum thrust. This maximum-thrust climb (full-thrust climb) has been considered as an optimal climb trajectory, and is therefore widely used in the real-world. However, the author previously found a new optimal climb trajectory by reducing the thrust near top of climb to save fuel. To realize the reduced-thrust optimal trajectory, the author proposes a new climb method (MCR climb), which is applicable in the current flight management system (FMS). The author argues that the thrust reduction is achieved by setting Maximum Cruise Thrust (MCR) at an appropriate timing during the climb. MCR limits the maximum thrust lower than full-thrust, which enables the fuel saving. This paper evaluates the real-world implementation of the proposed MCR climb. First, the possible fuel benefit by the MCR climb is calculated in the simulation, and about 50 lb of fuel saving per flight for B777-300ER is expected compared to full-thrust climb regardless of the wind condition. Next, to evaluate the MCR climb from the operational perspective, the full flight simulator experiment is conducted, and the proposed MCR climb is conducted by an airline pilot. There are only two pilot actions required to complete MCR climb, and no serious concerns of workload have been raised by the pilot. In addition, more than 100 lb fuel saving per flight is confirmed by the full flight simulator experiment. The obtained fuel benefit is larger than expected, which seems to come from the difference of aircraft performance model. More than 100 lb fuel saving will be sufficient to motivate the use of MCR climb, because the proposed MCR climb is applicable for all departure aircraft and the cumulative effect will be significant. The proposed MCR climb has a large potential to be used in the real world in the future for a new fuel saving method.