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Precision Distance Measuring Equipment Research Information

Regarding the Microwave Landing System (MLS) the research performed involved activities associated with MLS evaluation, implementation and operation. In addition, engineering support activities included the Mobile Microwave Landing System (MMLS) and the AN/TPN-30 landing system, although this work had a narrower scope than the MLS work.

A major effort undertaken was the continued development, refinement and validation of MLS siting criteria. Guidance material was developed for collocation of the MLS equipment, Approach Lighting System (ALS), and Instrument Landing System (ILS) equipment. In addition, MLS critical area definitions were developed and validated for various levels of MLS operations (e.g., straight-in, computed-centerline). In addition to specific criteria validation activities, the siting criteria were exercised during the performance of MLS and AN/TPN-30 site surveys. The resulting criteria have been published in the appropriate national and international documents.

Computer-based models were developed, refined, validated and applied during the course of the MLS activity. The MLS Mathematical Model (MIT and baseline versions) provides the capability to assess the effect on the MLS signal accuracy due to multipath arising from various sources within the airport environment. Subsequent to various refinement and validation activities, this model was used extensively to aid the development of MLS siting criteria. The modeling work was augmented by the development of a DME(N/P) signal model, which includes the modeling of deterministic and non-deterministic error sources. The signal model work concluded with the refinement of the existing MLS angle (AZ/EL) model and integration of the angle and DME signal models.

Assement activities included characterization of typical MLS guidance accuracy and coverage volume limits, and the evaluation of the US Navy Multimode (AN/ARN-138) receiver. In addition, support was provided for the demonstration of MLS advanced procedures through participation in the MLS Demonstration Program and the performance of MLS advanced approach procedures using General-Aviation aircraft. Technical and operator's manuals were generated for the MLS Database System, which stores data for facility performance, maintainability and reliability assessments.

In addition to the AN/TPN-30 site sureveys, auxiliary activities included support of the USAF Mobile MLS program through participation in the User's, Siting Criteria and Test Plan Working groups, and the preparation of data collection and aircraft tracking system for support of the USAF Initial Operational Test and Evaluation (IOT&E) Program.


Avionics Engineering Center
Russ College of Engineering and Technology
131 McFarland Avionics Building
Ohio University
Athens, OH 45701
Tel: (740) 593-1515

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