Masters Theses

Date of Award

12-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Aviation Systems

Major Professor

Frank Collins

Abstract

The United States Air Force Headquarters Air Education and Training Command (HQAETC) desired the capability to accomplish limited cell formation training with the T-1A Jayhawk jet transport aircraft in instrument meteorological conditions (IMC), using the Traffic Alert and Collision Avoidance System (TCAS). Traffic Alert and Collision Avoidance System is a family of airborne devices that function independently of the ground-based air traffic control system, and provide collision avoidance for a broad spectrum of aircraft types.

Testing was conducted using two T-1A Jayhawks, provided by AETC. The general test objective was to evaluate the feasibility of using the TCAS to execute IMC trail formation procedures. Instrument meteorological conditions are defined when the prevailing visibility is less than three statute miles or the ceiling is observed to be less than one thousand feet. The ceiling is normally identified as the base of a cloud layer cover of more than fifty percent coverage of the sky. Cell formation stationkeeping is an maneuver where multiple aircraft fly in formation with each other while maintaining a set distance apart. For the purposes of this evaluation, cell formation required the aircraft to maintain a position one mile in trail of the lead aircraft and 500 feet below the lead aircraft's altitude. The TCAS system was evaluated during takeoff, climb, cruise, and descent. Seven formation sorties, totaling 25.5 flight hours, were flown during this evaluation. Overall, the TCAS system was satisfactory for use during IMC cell formation procedures in the T-1A Jayhawk.

System performance characteristics during cell formation procedures were satisfactory. The TCAS position accuracy was satisfactory, and there were no antenna blanking problems which would impact normal cell formation operations. Antenna blanking results from signal interference and precludes the receiver from receiving and processing the signal from the transmitter. A safe operational envelope, compatible with current cell formation procedures, was determined. The TCAS operation in a high density traffic environment was satisfactory. Workload during simulated and actual IMC ranged from light, during straight and level flight, to high during unannounced maneuvering. Unannounced maneuvering was defined as any maneuvering performed by the lead aircraft without broadcasting the intent of his impending maneuver.

It is recommend that the TCAS be incorporated into current AETC cell procedures for IMC operations. No evaluation of operational cell formation procedures was performed due to the lack of established AETC TCAS cell formation procedures. A published set of procedures is necessary for operational use of the TCAS system for cell formation in actual IMC and should be established prior to operational employment of the system. To minimize pilot workload, inter-aircraft communications should be established and maintained during IMC operations. In addition, several recommendations to improve the TCAS display, warnings and cues were made.

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