Very High Frequency Omnidirectional Range Research Articles

Aviation Organization Strategy Development in National Airspace Modernization

The purpose of this qualitative study was to determine how small sub-directorates within larger organizations develop strategy to accomplish expansive legacy infrastructure re-engineering. There is significant, historical academic inquiry on Technological Transitions (TT)s with respect to infrastructure modernization; the conversion of the National Airspace System from ground-based to space-based navigation is an example of a TT. There are also studies on how to re-engineer legacy software systems to continue supporting organizational needs. This study is intended to explore a case of re-engineering the expansive legacy ground-based navigation system in the United States by efficiently reducing the size of the network and expanding then verifying signal coverage on over 4.5 million square miles. It is not a pure TT, nor a pure software re-engineering, but rather a large-scale re-engineering of a pre-existing hardware and software infrastructure. It constitutes a nationwide effort to re-design and expand the legacy ground-based navigation system developed over 70 years. The Federal Aviation Administration (FAA) advised the public in 2011 that it intended to re-engineer and reduce the Very High Frequency Omnidirectional Range (VOR) network from 896 stations down to 593 stations - to be defined as the Minimum Operational Network (MON). This reduction was based on the premise that two-thirds of the legacy VORs would be retained but their coverage expanded to cover twice the airspace within the US than the previous network. The FAA Flight Program Operations (FPO) is a small sub-directorate within the larger organization that is now responsible to validate signal coverage on several million square miles of additional airspace. Understanding how the FPO develops strategy and leverages technology to support this endeavor can provide a repeatable template for future, expansive, legacy infrastructure re-engineering efforts. This study discovered that the FPO developed and iteratively evolved strategy to accomplish the VOR MON using tribal knowledge, subject matter expertise and accepted business re-engineering practices. The template can be applied to other legacy infrastructure re-engineering efforts to support forthcoming TTs.

Assessment of Health Monitoring Trustworthiness of Avionics Systems

The article provides a methodology for assessing the trustworthiness of health monitoring the dismounted avionics systems with automated test equipment (ATE). The indicators include the probabilities of false-positive, false-negative, true-positive, and true-negative. For the first time, we introduced into consideration the instability of the source of stimulus signal (SSS), the random and systematic component of the measuring channel error, and the reliability characteristics of the systems themselves. We consider a specific case of an exponential distribution of permanent failures and intermittent faults and derive formulas for calculating the trustworthiness indicators. Numerical calculations illustrate how the probabilities of correct and incorrect decisions depend on accuracy parameters. We show that the probabilities of false-positive and false-negative increase much faster than the probabilities of true-positive and true-negative decrease when the standard deviation of stimulus signal increases. For a Very High-Frequency Omni-Directional Range (VOR) receiver, we demonstrate that even with a zero random error generated by the source of the stimulus signal, the probabilities of false-positive and false-negative are different from zero.

Deep learning for aircraft classification from VHF radar signatures

Radio sources in the Very High Frequency (VHF) band can be seized as opportunity donors in a passive radar configuration such as FM radio stations and VHF omnidirectional range (VOR). A full-wave simulation of three size classes of aeroplanes shows that their bistatic radar cross-section (RCS) are statistically comparable, albeit perform differently in time while the plane is flying. This difference can be exploited to recognize the size of the aeroplanes with respect to these classes. Measurements confirm this possible differentiation between the aeroplanes within the same class. Encouraging initial results were obtained using convolutional or recurrent neural networks to classify aircraft classes, combining simulated bistatic RCS results and real trajectories (collected from automatic dependent surveillance-broadcast data).

Assessment of Training Aircraft Crew Exposure to Electromagnetic Fields Caused by Radio Navigation Devices

The paper depicts research concerning the value of the electric component of the electromagnetic (EM) energy determined by the NHT3DL meter by Microrad with the 01E measuring probe during a number of flights made by Aero AT-3 R100, Cessna C172, and Tecnam P2006T fixed wing aircrafts and a Robinson R44 Raven helicopter. The point of reference for the recorded measurement was the normative limits of the electromagnetic field (EMF), which can influence a pilot in the course of a flight. Selected studies of the maximum value recorded by the meter was E = 10.66 V/m when landing at an airfield equipped with the VHF (Very High Frequency) omnidirectional radio range (VOR) approach system. Particular attention has been paid to changes in electric field intensity during the operation and their effects on the type of radio navigation systems as well as communication with the airfield control tower. The obtained results were validated in the Statistica 13.3 software for the purpose of a detailed stochastic analysis of the tested values. Results obtained are subject to the mandatory requirements of Directive 2013/35/EU as well as to the relevant regulations in Poland.

The Feasibility of Remotely Piloted Aircrafts for VOR Flight Inspection.

This article analyzes the use of Remotely Piloted Aircrafts (RPA) in VOR (Very High Frequency Omnidirectional Range) flight inspection. Initially, tests were performed to check whether the Autopilot Positioning System (APS) met the regulatory requirements. The results of these tests indicated that the APS provided information within the standard regulations. A Hardware in the Loop (HIL) platform was implemented to perform flight tests following the waypoints generated by a mission automation routine. One test was performed without introducing disturbance into the proposed test platform. The other four tests were performed introducing errors in latitude and longitude in the APS into the platform. The errors introduced had the same characteristics as those measured in the initial tests, in order for the simulation tests to be as similar as possible to the real situation. The tests performed with positioning errors only did not lead to false misalignment detection. However, introducing positioning errors and a 4° VOR misalignment error, a misalignment of 3.99° was observed during the flight test. This is a value greater than the maximum one allowed by the regulations, and the system indicates the VOR misalignment. Five flight inspection tests were performed. In addition to the APS errors, tests with a modulation error were also conducted. Introducing a 4° VOR misalignment in conjunction with modulation error, a misalignment of 4.02° was observed, resulting in successful misalignment detection.

Present and Future of Air Navigation: PBN Operations and Supporting Technologies

The present work reviews the new concept of operation that will be soon implemented in SESAR and NextGen (January 2020) using new state-of-the-art technology mainly based on onboard avionics: data link equipment, broadcast and surveillance systems, and Global Navigation Satellite System (GNSS) area augmentation. One of the main improvements of Performance-Based Navigation (PBN) is the use of satellites and more precise and accurate onboard instruments than current standard avionics related to ground-based navigation aids (VOR, NDB, DME, etc.). Air navigation systems have been without mayor updates for nearly 40 years, when most Very High Frequency Omnidirectional Range (VOR) and Tactical Air Navigation (TACAN) systems were implemented worldwide in the civil and military fields, respectively. These standard navigation systems lack new required performance navigation and required big deal of maintenance, especially in redundant systems. Recently, the development of new and precise GNSS and communication systems has allowed their use on different scenarios: Instrumental Flight Rules (IFR) departures, initial and final approaches, etc. Additionally, in several international airports, Ground Based Augmentation System (GBAS) approaches have been already successfully tested and implemented. Related to GBAS, the Automatic Dependent Surveillance Broadcast (ADS-B) is a cooperative technology that enhances pilots and controllers’ situation awareness, since ADS-B broadcasts own and other aircraft position. Controller Pilot Data Link Communications (CPDLC) may be another key element of the PBN concept of operations (CONOPS), since it provides air–ground data communications for the air traffic control (ATC) service and the aircrew, reducing risks associated to human factor: poor speaking, radio congestion, message confusion, standardization, etc. The main goal of this review is to present the PBN concept and the potentially supporting Communication, Navigation and Surveillance (CNS) systems, in the context of the NextGen and SESAR Air Traffic Management (ATM) modernization programmes.

High-resolution signal-in-space measurements of VHF omnidirectional ranges using UAS

Abstract. In this paper, we describe measurement results of the signal-in-space of very high frequency (VHF) omnidirectional range (VOR) facilities. In aviation VOR are used to display the current course of the aircraft in the cockpit. To understand the influence of wind turbines (WT) on the signal integrity of terrestrial navigation and radar signals, the signal content and its changes, respectively, must be investigated. So far, only numerical simulations have been carried out on the frequency-modulation (FM) part of the Doppler-VOR (DVOR) signal to estimate the influence of WT on DVOR. Up to now, the amplitude-modulated (AM) part of the DVOR was not assessed at all. In 2016, we presented an unmanned aerial system (UAS) as a carrier for state-of-the-art radio-frequency (RF) measurement instrumentation (Schrader et al., 2016a, c; Bredemeyer et al., 2016), to measure and to record the true signal-in-space (both FM and AM signal) during the flight. The signal-in-space (which refers to time-resolved signal content and field strength, respectively) is measured and sampled without loss of information and, furthermore, synchronously stored with time stamp and with precise position in space, where the measurements were taken.

Procedural and Operational Consequences of Navigational Equipment Outages: Exploration of Airport Performance

This paper explores the impact of unscheduled navigational and surveillance equipment outages on airport performance during visual flight rules and instrument flight rules at San Francisco International Airport and Phoenix Sky Harbor International Airport. The following most common unscheduled short outages, which occurred during January 2000-December 2002, are analyzed in detail: very high frequency omnidirectional range (VOR), approach lighting system type 2 (ALSF-2), the secondary radar Mode S, and air traffic control radio beacon system (ATCRBS). We explore the air traffic control procedures and responses to unscheduled outages, and develop a methodology to examine the effects of unscheduled outages on airport performance. Two Federal Aviation Administration databases, maintenance management system and aviation system performance metrics, are used to construct censored regression models (i.e., Tobit models) to assess the airport throughput performance during such unscheduled outages. It is found that airport arrival and departure throughputs do not deteriorate with VOR and ALSF-2 outages due to availability of air traffic procedures that allow alternative approaches into the airport. However, the unscheduled outages of secondary radar Mode S and ATCRBS do cause airport throughput degradations.

Investigation of spurious emissions from cellular phones and the possible effect on aircraft navigation equipment

The study described in this paper investigated the possible interference of spurious emissions from cellular phones on aircraft navigation and communication equipment. Six wireless phone technologies were investigated over three frequency ranges, which covered the receiving ranges of five aircraft systems. The aircraft systems examined were very-high frequency omnidirectional range (VOR), localizer (LOC), very high frequency communication (VHF), glide slope (GS), and global positioning system (GPS). Research was performed in a semi-anechoic chamber (SAC) and a reverberation chamber (RC), with the phone at a distance of 1 m from the receiving antenna. Two antenna orientations were tested in the SAC. Initial tests yielded the appropriate height from the receiving antenna above the ground plane that would produce a maximum field measurement. Keypad programming was used to simulate worst-case phone transmissions. Radiated power measurements were performed and analyzed taking into consideration path loss results from the RTCA/DO-233 study. None of the six phone technologies investigated exhibited a power level greater than a 38-dBm path loss level above the maximum sensitivity of the aircraft system antennae when tested 1 m away from the antenna. These results indicate that, for the aircraft systems tested (VOR, LOC, VHF, GS, and GPS), the antenna of these systems would not have detected the emissions of the phones used in this study (CDMA-cellular, TDMA-11 Hz, TDMA-50 Hz cellular and PCS, GSM, and DCS-1800).

Analysis of Fix Displacement Tolerances for the Development of Instrument Procedures Criteria for GPS

The current airway structure is based on conventional ground-based navigational aids (navaids), such as very high frequency (VHF) Omnidirectional Range (VOR) and Distance Measuring Equipment (DME). In this structure, various fixes are defined along with their associated fix displacement tolerances (FDTs), from which obstacle clearance areas are designed. While FDTs are formulated using 95 percent accuracy values in the existing system, the error with conventional navaids is rather tightly bounded by a local ground monitor. On the other hand, GPS does not have a local monitor, and therefore, direct application of a 95 percent GPS accuracy value is not appropriate for an FDT. This paper analyzes the problem and derives the FDTs for GPS users equipped with Technical Standard Order (TSO)-C129 or GPS/Wide Area Augmentation System (WAAS) receivers. This analysis was performed in support of the Federal Aviation Administration's (FAA) development of fix tolerance areas and is part of the effort to develop area widths and other parameters for instrument procedures criteria.

VHF propagation over hilly, forested terrain

Propagation measurements at low altitudes over hilly, forested terrain made with the objective of developing a computer-based propagation model capable of predicting path loss over similar terrain given the terrain profile between transmitter and receiver are reported. The measurements were made at a frequency of 110.6 MHz with the very high frequency omnidirectional range (VOR) station at Gardner, MA, as a transmitter. The received signals were measured at distances between 7 and 15 km by making vertical descents with a helicopter from altitudes of roughly 600 m down to 10 m above ground. Negligible specular ground reflection was observed from this terrain, and no reflection is included in the model. We found good agreement between the measurements and a multiple-diffraction model based on an extension of the Deygout approximation. Use of two knife edges was sufficient to characterize the terrain diffraction. Predictions of the Longley-Rice computer model are included for comparison.

Wide-Aperture Digital VOR

The very high frequency (VHF) omnirange has undergone a number of evolutionary changes in the past 30 years. Early measurements of large errors led to the development of the Doppler VHF omnidirectional irectioal range (VOR) and its use. Further developments have been the precision multilobe VOR and the precision Doppler VOR. Interest in area navigation has led to the desire for a VOR greatly superior to any so far developed. Specifically, the objectives of the improved VOR would be a system that would significantly reduce magnitude of siting errors, provide greater accuracy and use digital techniques to simplify processing. ssing. The wide-aperture digital VOR described herein has been developed to meet these objectives. Its design is based on the crossed-pair interferometer principle where eight such pairs are energized successively by a set of pulses and phase shifts. The time multiplexed signal, detected by the aircraft receiver, is processed and simple digital computations are performedto determine the angular coordinates. The performance improvements have been achieved by the combination of using a 275-ft antenna aperture, and the use of digital techniques to generate the ground-radiated navigational signals and to process them in the airborne processor. Field tests of the feasibility model indicate it is a high performance ance system, capable of achieving an order of magnitude improvement in both site error reduction and in accuracy compared to present VOR systems. The measured accuracies were 0.11-degree standard deviation.

Incidence of Low Clouds at Bombay airport (Santacruz) with reference to Jet landings with the help of the Instrument Landing System (ILS)

Santacruz airport constitutes a high traffic density area, with a- substantial number of jet aircraft movements. Aviation hazards at this airport get particularly accentuated during the monsoon season on account of the occurrence of very low clouds, strong gusty winds and poor visibility conditions in mist or haze, or showers. There are a- few important hill features a-round the airport, not far from the landing area.
 
 The airport is equipped with standard radio navigational aids, namely, very high frequency omnidirectional range (VOR), Instrument Landing System (ILS), the Aerodrome Surveillance Radar (ASR). A precision approach radar (PAR) will become operational at this airport shortly. On the ILS the glide path angle has recently been reduced from 4 degrees to 3.3 degrees above the horizon, necessitating the approach of the aircraft generally at a lower altitude, the altitude above the middle marker being of the order of 561 ft only. The distance of the middle marker from ARP is 2972 m (1.6 n.m.). Fig. 1 is the instrument approach chart for the Bombay airport.
 
 The aviation hazards that may be encountered by the jet aircraft especially in the monsoon season, on the phase of the final approach, have been discussed in this note with reference to climatological statistics and the synoptic climatology of this airport. It is hoped that the result arrived at will be of some practical value to pilots operating jet aircraft and to air traffic controllers.

Background and Principles of Tacan Data Link

The integration of Tacan with very-high-frequency omnidirectional range (VOR) to provide one common air-navigation and air-traffic-control system requires, for full usefulness, a method of automatic air-surface communication. Such a method, called the Tacan data link, has been devised, and is being flight-tested. Using this data link, messages can be received and sent to each of 120 aircraft every 2.67 seconds. Such messages would consist of navigational, aircraft-status, and traffic-control information. The data link employs the Tacan Surface Beacon to carry both analog and digitallycoded messages, interpolating the coded pulse bursts, which last approximately 3 msec, 45 times every second. No additional transmitters or receivers are needed.