Quantifying Delay Reduction Benefits for Aviation Convective Weather Decision Support Systems

In an era of significant federal government and airline budget austerity for civil aviation investments, it has become essential to quantitatively demonstrate delay reduction benefits of improved convective weather decision support systems. The new FAA Air Traffic Organization (ATO) and the FAA Flight Plan 2004-08 have quantitative performance metrics that are closely related to reducing convective weather delays. However, these metrics currently do not have an adequate means to account for the differences in convective weather severity and changes in the National Airspace System (NAS). In this paper, we summarize contemporary approaches to convective weather delay reduction benefits quantification and outline a program to develop a significantly improved capability that can be used to assess benefits of specific systems and accomplish weather impact normalization for studies of NAS performance.

First, we consider benefits quantification based on feedback from experienced users of a system. Feedback on “average” benefits from a system at the end of a test period was used to generate delay reduction estimates for the Integrated Terminal Weather System (ITWS), the ASR-9 Weather System Processor (WSP), and the Weather and Radar Processor (WARP). A new refinement to that procedure augments the approach by analyzing flight tracks during convective weather before and after the system under testing was deployed. This end-of-season interview approach was found not to be viable in highly congested en route airspace. Hence, a new approach was developed for Corridor Integrated Weather System (CIWS) benefits assessment that uses real time observations of product usage during convective weather events, coupled with in depth analysis of specific cases.

Several recent initiatives that attempted to quantify delay reduction benefits by comparing flight delays before and after a system deployment are discussed. This seemingly simple approach has proven very difficult in practice because the convective weather events in the different time periods are virtually never identical , and because other aspects of the NAS may also have changed (e.g., user demand, fleet mix, and other systems that impact convective weather delays). It has become clear that one needs a quantitative model for the NAS that permits adjustment of measured delay data to account at least for the differences in convective weather and changes in user demand (i.e., flight scheduling).

We describe a model under development for estimating NAS delays in the presence of convective weather that can be used as a tool for assessing delay reduction benefits of specific systems, estimating the available “pool” for convective weather delay reduction, and determining if the overall NAS is performing better in management of convective weather over time. This model considers:

• both en route and terminal capacity loss due to convective weather,

• the non linear dependence of queue delays on demand and capacity, and

• detailed knowledge of the NAS route structure.

The paper concludes with recommendations for measuring near term benefits of various classes of convective weather decision support systems.