Feasibility study on applying continuous descent operations in congested airspace with speed control functionality: Fixed flight-path angle descent

Continuous descent operations (CDO) are an efficient descent operation for passenger/cargo aircraft and implemented at various airports worldwide. However, it is difficult for air traffic controller (ATCo) to predict the CDO trajectory and control the CDO aircraft, therefore limiting the applicable window only during the low traffic periods. To maximize potential benefits by introducing the CDO, it is required to implement the CDO into congested airspace and time window. This study introduces an augmentation to CDO application in the congested airspace, called fixed flight-path angle (Fixed-FPA) descent. The fixed-FPA descent was originally proposed and investigated only for small passenger jet aircraft; thereafter the fixed-FPA descent was introduced to large passenger jet aircraft. This proposed procedure consists of several altitude restrictions along the arrival route. By following the altitude restrictions, the aircraft flies with a specified flight-path angle. Additionally, specifying the flight-path angle facilitates the prediction of the CDO trajectory by ATCo. Moreover, by setting a shallower flight-path angle compared with the conventional CDO, the fixed-FPA descent is capable of speed control. The preceding studies conducted only the preliminary feasibility study of the fixed-FPA descent on large jet aircraft. In this study, a series of full-flight simulator experiments and Monte Carlo simulations were conducted to assess the operational feasibility and demonstrate the capabilities of fixed-FPA descent. Experimental results demonstrated that the fixed-FPA descent meets the requirements for integrating the CDO into congested airspace, such that the vertical path of the CDO can be predicted by the ATCo, and the speed of the CDO aircraft is controllable. Additionally, the simulation results revealed that the fixed-FPA descent has better fuel efficiency than the conventional when the descending aircraft is required to delay its arrival time.