Everything you ever wanted to know about FDMS

If you want or need to understand the basic concepts underlying Flight Deck-based Merging and Spacing  (FDMS), you can’t do better than this document written by John Marksteiner and Randall Bone from the FAA’s FDMS development group. It’s comprehensive, clearly formulated, and really just plain fascinating. There’s too much good material to excerpt properly, but for anyone who hasn’t yet joined the FDMS gospel choir, here’s a few graphs that summarizes some fundamental goals:

The main objective of FDMS is to achieve consistent, low variance spacing between paired aircraft at the entry to an arrival procedure (e.g., Continuous Descent Arrival) and on final approach […]

Achieving the consistent, low variance spacing is expected to reduce the time interval between the first and last aircraft in the overall arrival flow which results in increased capacity. Overall efficiency should be increased through the avoidance of costly, low altitude maneuvering.

Other benefits may be realized through FDMS. Those include the following:

• Reduction in radio frequency congestion;
• Increased predictability of arrival traffic;
• Increased ability to conduct CDA operations due to consistent, accurate spacing;
• Sustained capacity during CDA operations;
• Reduction in the number of controller issued maneuvering instructions;
• Reduction in ATC workload, and potentially increased sector capacity, by allowing flight crews to conduct the spacing task;
• Reduction in the number of go-arounds caused by less than desirable spacing.

What is not fully expressed in this graph is the long-term cost, noise and environmental savings that could be achieved if the majority (vast majority?) of scheduled flights were operated using CDA. At this month’s AAAE NextGen conference in Louisville, Capt. Christian Kast from UPS told us that in their initial FDMS trials, they found that they could reduce fuel consumption in the last 25 minutes of flight by an average of 21% for B757s and 31% for B767s.