1987-10-01

FMCS/TNAV Application in the FAA ATC System 871811

Flight management computer systems provide a Health of information which is presently available to and utilized by flight crews only. The use of FMCS with TNAV/4D capabilities, jointly by flight crews and ATC) could significantly contribute to accomplishing all system users goals; decrease delays, decrease pilot/controller workload, and enhance safety. TNAV is defined as the capability to arrive at a designated point at a required time (RTA). The term “TNAV” encompasses various means for assisting the pilot and/or ATC controller in meeting an RTA. and does not necessarily require a pre-defined FMC 3D flight path. The term 114D ll implies implementation of TNAV capability by means of an FNC-computed 4D profile. A 4D profile consists of a lateral flight plan (2D) with associated vertical and speed (3D), with the 3D profile defined so as to arrive at a designated point at a required time (4D).
THE PURPOSE OF THIS PAPER is to outline the ATC System and its affect on FNCS operations. It will also outline potential applications of TNAV/4D related features to help alleviate operational congestion and workloads.
FMCS enables the flight crew to pre-program their flight “in the box” within pre-designated company and aircraft performance parameters. These allow the aircraft to be flown from departure to destination efficiently, timely, and economically. However, once this pre-programmed flight is introduced into the present ATC system, these best laid plans are often destroyed by a different route assignment prior to departure or a control instruction (speed assignment or vector) after departure.
Naturally the intent of ATC was not to destroy the efficient operation of this one aircraft. However, once this flight is introduced into the ATC system, it must be blended with and constrained by the other system participants. The priority now switches from efficiency to safety and separation.
Flow Control and associated Netering programs have been initiated by the FAA with the intention of relieving congestion and decreasing airbourne delays at all major terminal areas within their jurisdiction. This naturally reduces controller workload and increases safety. However this often times has the reverse effect on pilot workload. Unplanned ground delays, re-routes, speed assignments, and vectors off assigned routes increases pilot workload.
The sharing of available FNCS data by flight crews and ATC could reduce all our workloads and increase safety and efficiency in the following three areas:

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