Instrument Flight Rules Research Articles

Steeper Approach Procedure for Increasing Ultimate Capacity of Closely Spaced Parallel Runways

The steeper approach procedure (SAP) is investigated as an innovative option for increasing the ultimate arrival capacity of closely spaced parallel runways under the instrument metrological conditions and instrumental flight rules. SAP is based on the two pairs of instrumental landing systems, each enabling the certified aircraft to approach a given parallel runway at either the standard (3°) or steeper (5° to 7°) glide slope (GS) angle. The difference in the GS angles allows application of the air traffic control (ATC) vertical separation rules between the arriving aircraft; this can mitigate the impact of wake vortices on the aircraft in trail separation while on the same or different approach trajectories. A combination of these with the ATC longitudinal and horizontal–diagonal separation rules has the potential to increase the ultimate arrival capacity of closely spaced parallel runways. An analytical model was developed for calculating the arrival ultimate capacity of closely spaced parallel runways. The model inputs are the geometry of given parallel runways, the ATC minimum separation rules, and the aircraft fleets mix characterized by the aircraft wake vortex types and categories, capability of using different GS angles, final approach speeds, and the arrival runway occupancy time. The model output consists of the ultimate capacity of closely spaced parallel runways and its variations in dependence on the mixture of arrivals and departures for a large U.S. airport.

Comparison of passive versus active noise reduction headsets in light aircraft cockpit noise: Communications intelligibility and workload

Under instrument flight rules (IFR) conditions in Cessna 172R (95 dBA) cockpit noise, eight IFR-licensed pilots flew four 3.5-h nonstop flights in an FAA-certified, single-engine flight simulator, while wearing one of four communications headsets in each flight. All flights imposed an equivalently high level of air traffic control communications, at three Speech Transmission Index (STI) values: 0.30, 0.50, and 0.70. Perceptual and psychomotor workload were also controlled. In addition to a battery of flight-related metrics (some reported elsewhere), an objective, flight-embedded measure of communications intelligibility was obtained—the number of readbacks required of the pilot to attain 100% intelligibility on each command. An ANOVA revealed that as a group, the ANR headsets (Sennheiser HMEC300, Bose Aviation X, LightSPEED Thirty3G) required significantly fewer readbacks (averaging 1.2–1.3) than did the passive David Clark H-10-13.4 (averaging 1.5). Flight control performance, as reflected by deviations in assigned magnetic heading, altitude, and airspeed, was highest during flights with the Bose headset. Pilots’ workload estimates were measured using the modified Cooper-Harper scale, with 1 representing lowest workload and 9 representing highest. The three ANR headsets were associated with average workload ratings of 3.4–3.5, while the passive headset yielded a higher average workload of 4.4.

Improving Aircraft Sequencing and Separation at a Small Aircraft Transportation System Airport

Ever-increasing traffic levels at the nation’s major airports have led to traffic congestion and flight delays. Capacity must be increased by building more airports at a great cost or by expanding services to some of the 4,500 airports not currently served by scheduled air carriers. A system must be developed to handle the increased traffic at these non-controlled airports, especially when instrument meteorological conditions prevail. Much work has been performed under the NASA Small Aircraft Transportation System program to determine the feasibility of aircraft operation under instrument flight rules in an air-traffic control free environment. This paper presents research, performed as an extension of the SATS program, into self-separation of general aviation aircraft in a self-controlled airport environment. The research focused on two specific areas: (1) improving automatic sequencing of aircraft of different speeds to make the airspace more efficient, saving time, fuel, and money, and (2) assisting the pilot with approach timing decisions to assure safe aircraft spacing while proceeding in an efficient manner. The primary evaluation method was a real-time distributed simulation with test cases performed by multiple pilots flying simultaneously in the simulation environment. Simulations and test scenarios were performed in the Engineering Flight Simulator, a modular, real-time, nonlinear, six degreeof-freedom fixed base simulator, at Texas A&M University. The pilots flew various general aviation aircraft with differing approach speeds under instrument meteorological conditions. Approach speeds ranged from 80 kts. to 140kts. to encompass the majority of aircraft from small trainers up to light jets that will use the potential SATS airports. New spacing rules were implemented to reduce holding times, and Total Holding Time was used as a metric to validate these new rules. Simulations were performed both with and without automated sequencing to validate the new spacing rules and compare the effects of automated sequencing. A human factors analysis was performed to determine the benefits of shifting some spacing functions from the pilot to the onboard systems, and reductions in pilot workload and improvements in pilot performance were measured to assess the safety improvements due to the increased automation. Based on the results presented in the paper, it was concluded that by changing the sequencing procedure to assign airspace entries once the aircraft are closer to the airport, potential bottlenecks can be avoided and holding times reduced. Furthermore, as a result of the increased avionics functionality and a change in approach spacing guidelines, safety is improved, and holding times are reduced. With these two improvements combined, significant holding time reductions are achieved resulting in fuel and cost savings and further make the self-controlled airport a safe and viable transportation alternative.

Effectiveness of the Ground-Based Transceiver (GBT) Parrot System for Monitoring GPS Integrity for Alaska ATC “Radar-Like Services” Using ADS-B

In January of 2001, the Federal Aviation Administration (FAA) commissioned the first use of Automatic Dependent Surveillance Broadcast (ADS-B) based on the Global Positioning System (GPS) to support Air Traffic Control (ATC) “radar-like services (RLS).” These services are available via ATC to nearly 200 equipped aircraft operating in the vicinity of Bethel, Alaska as part of the FAA’s Capstone program to improve aviation safety in Alaska. RLS allow ATC to support Instrument Flight Rules (IFR) separation of 5 nautical miles (nmi) based only on ADS-B surveillance. Since ADS-B information is being used by ATC for aircraft separation, some method to verify the integrity of the GPS/ADS-B data must be continuously provided. The ADS-B concept, as defined in RTCA standards, relies on air-craft to “self-report” the integrity of the navigation data reported in the ADS-B message. System evaluations leading to commissioning of RLS showed the ADS-B data to be easily equivalent to radar surveillance in terms of accuracy, latency, and update rate. However, it highlighted some difficulties with the self-reported integrity concept for this “first generation” of ADS-B avionics, due mainly to excessive Receiver Autonomous Integrity Monitoring (RAIM) holes—from the ATC perspective. The resulting excessive number of false integrity alerts led to an FAA decision to disregard ADS-B self-reported integrity in the Bethel area and, instead, to monitor GPS integrity through a network of new ground position “parrot” monitors implemented along with the existing ADS-B receiving stations. The objective of this paper is to determine how effective this monitor system is at detecting integrity failures of the GPS satellites that could cause Hazardously Misleading Information (HMI) over the Bethel, Alaska area. Although our results show that the existing parrot system is generally effective for conducting RLS in the Bethel area, we offer recommendations to the FAA to improve the performance of integrity monitoring in the area.

Institutionalized Model-Making and ecosystem-based management of exploited resource populations: a comparison with instrument flight

Ecosystem-based management of resource populations is not a reality but a vision for the future. We liken it to instrument flight of an aircraft. An aircraft cannot be controlled without visual reference to the ground (VFR—Visual Flight Rules) or a cluster of flight instruments (IFR—Instrument Flight Rules). Instrument pilots are trained to develop a rhythmic scan of the cluster to obtain information about flight path and attitude. The untrained tendency is to fixate on a single gauge. When this occurs, the aircraft deviates from its desired attitude and trajectory, and control may be lost. This is analogous to single-factor management in which variables, like habitat quality, recruitment, predator control, or harvest rates, are singled out for manipulation without regard to the others. Exploited populations are no less complex than an aircraft in flight. They move through time and space, and can only be effectively managed using the multiplicity of instruments nature has provided. These include distal as well as proximate variables because populations are embedded in ecosystems that holistically propagate indirect effects to them. Therefore, whole-ecosystem-based management is needed, giving attention to multiple control variables as in the case of instrument flight. Only modeling can identify a suite of sufficient controls, both direct and indirect, and place them in a coherent, operational framework. “Flying the resource”, then, is what we conceive as modeling-assisted, ecosystem-based management. We advocate that management institutions should employ ecosystem-based modeling as an ongoing organizational activity in which scientists, managers, and others cooperate in framing conceptual models from which further steps in modeling can proceed. We call this Institutionalized Model-Making (IMM), with two purposes: (1) building teams from indigenous expertise, and (2) producing models to serve in the same relation to nature as flight simulators do to actual aircraft. The models mimic responses to control actions, simulating multifactorial management analogous to the instrument scans and control manipulations of instrument flying. We illustrate our ideas with a STELLA simulation model of the North American white-tailed deer ( Odocoileus virginianus Miller) in the Adirondack Mountains of New York State, USA. Sensitivities of control parameters are ranked, and use of the model in the instrument flight sense is demonstrated. The results reflect on current styles and fashions in ecological modeling.

Simulation of IFR Helicopter Operations in the Gulf of Mexico Low-Altitude Airspace

This paper describes a model and simulation of offshore Instrument Flight Rules (IFR) helicopter operations originating from Intracoastal City, Louisiana, into the Gulf of Mexico. The existing en route airspace structure of Houston Center’s Offshore Sector below 7,000 ft, and the instrument approaches at Intracoastal City, both based on Global Positioning System navigation, were modeled in detail. The established Air Traffic Control (ATC) procedures of Lafayette Approach Control (LFT) and Houston Center were modeled to ensure that the simulated traffic flows reflected those that are followed in actual IFR operations. Three scenarios were simulated, one scenario in the existing, predominantly non-radar environment, and two in hypothetical radar environments. The results of these simulations were used to evaluate the capacity improvements gained through introduction of radar and direct pilot/controller communication into the terminal and the en route areas of the Gulf of Mexico. The baseline scenario results indicate that there were significant delays attributable to capacity constraints at Intracoastal City. A large delay reduction was obtained by adding the terminal-area radar and a further reduction in delays was obtained by adding the en route radar.

実機を用いた単独計器飛行時のパイロットの視線移動計測

Operations under single pilot instrument flight rules for general aviation aircraft is known to be one of the most demanding pilot tasks. Scanning numerous instruments plays a key role for perception and decision-making during flight. Flight experiments have been done by a single engine light airplane to investigate the pilot eye scanning technique for IFR flights. Comparisons between the results by an actual flight and those by a PC-based flight simulator are made. The experimental difficulties of pilot eye scanning measurements during the actual IFR flight are discussed.

Two-Dimensional Simulations of Wake Vortex Detection Using Radio Acoustic Sounding Systems

Aparallelcodeisdevelopedtosimulatenumericallywakevortexdetectionusingaradioacousticsoundingsystem (RASS). The code is written in FORTRAN 90 with the message passing interface for parallel implementation. The numerical simulation solves simultaneously the linearized Euler equations for a nonuniform mean e ow and the Maxwellequationsforanonhomogeneousmedium.Theradartransmitterandreceiverantennasaremodeledusing an array of point sources and a beam-forming technique, respectively. Many features of the RASS are explored using thenumericalsimulation.First,a uniformmeane owisconsidered,and theRASSsimulation isperformedfor two different types of incident acoustic e eld: a short single-frequency acoustic pulse and a continuous broadband acoustic source. Both monostatic and bistatic cone gurations are examined, and their results are compared. Taylor and Oseen vortex velocity proe les are used as samplemodels, and their mean e owe eldsare reconstructed from the backscattered electromagnetic signal using the Abel transform. The effect of radar beam width is also considered, as are the issues of nonaxisymmetric and interacting vortices. I. Introduction T HEcapacity of airports is constrainedseverelyby the airtrafe c control system’ s consideration of aircraft wake vortices. The present Instrument Flight Rules (IFR) restrictions are based on aircraft weight. The “ 3‐ 4‐ 5‐ 6 rule” sets the separation distances of aircraft by categories from small, less than 41,000 lb (18,600 kg), to heavy, greater than 255,000 lb (116,000 kg). These separations are viewed as very conservative. However, because there remains signie cant uncertainty about wake vortex behavior under different atmospheric conditions, there are considerable technological barriers to improvements in terminal area productivity. In an attempt to enhance airport capacity, an aircraft vortex spacing system (AVOSS) has been under development at NASA Langley Research Center. The AVOSS will provide the means to allow air trafe c control to reduce spacing safely in instrument operations when the appropriate weather conditions exist. A key element in AVOSS is the development of a real-time reliable wake vortex detection system (WVDS). A radio acoustic sounding system (RASS) is a promising candidate for a WVDS. The basic concept of RASS is based on the tracking of sound waves with radar. When acoustic waves are transmitted, they produce pressure perturbations, which lead to e uctuations in the atmospheric permittivity. An incident electromagnetic e eldisthenscatteredduetothepermittivityvariationsandgenerates an echo that can be detected by a receiver antenna. The spectrum of this echo shows a Doppler shift proportional to the local speed of sound. However, the backscattered signals are so weak that no measurable signal would be received unless the Bragg condition is satise ed.The Bragg condition is a relationshipbetween the incident electromagnetic and acoustic wavelengths that ensures a constructive interference between the two waves. The Bragg condition may be written as ¸e D 2¸a sin®

NASA/Army/Bell XV-15 Tiltrotor Low Noise Terminal Area Operations Flight Research Program

To evaluate the noise reduction potential for tiltrotor aircraft, a series of three XV- 15 acoustic flight tests were conducted over a five-year period by a NASA/Army/Bell Helicopter team. Lower hemispherical noise characteristics for a wide range of steady-state terminal area type operating conditions were measured during the Phase I test and indicated that the takeoff and level flight conditions were not significant contributors to the total noise of tiltrotor operations. Phase I results were also used to design low-noise approach profiles that were tested later during the Phase 2 and Phase 3 tests. These latter phases used large area microphone arrays to directly measure ground noise footprints. Approach profiles emphasized noise reduction while maintaining handling qualities sufficient for tiltrotor commercial passenger ride comfort and flight safety under Instrument Flight Rules (IFR) conditions. This paper will discuss the weather, aircraft, tracking, guidance, and acoustic instrumentation systems, as well as the approach profile design philosophy, and the overall test program philosophy. Acoustic results are presented to document the variation in tiltrotor noise due to changes in operating condition, indicating the potential for significant noise reduction using the unique tiltrotor capability of nacelle tilt. Recommendations are made for a final XV-15 test to define the acoustic benefits of the automated approach capability which has recently been added to this testbed aircraft.

Airborne turbulence measurements in the lower troposphere onboard the research aircraft Dornier 128-6, D-IBUF

The research aircraft Dormer (DO) 128-6, call-sign D-IBUF, operated by the Institute of Flight Guidance and Control of the Technical University of Braunschweig and its scientific equipment is presented. The aircraft's operational capabilities and the quality of measurements of meteorological parameters and trace constituents in the lower troposphere are discussed. Besides avionic instrumentation for VFR-flights (Visual Flight Rules) and IFR-flights (Instrument Flight Rules) at low altitudes over complex terrain, there are redundant sensors for the measurement of wind, temperature and humidity. Together with INS- (Inertial Navigation System) and GPS- (Global Positioning System) navigation a sample frequency of 25 Hz (soon 100 Hz) is realised. Using a mean ground speed of 65 m s -1 , the resolution of the measurements is less than 3 m. Since 1998, the Institute of Meteorology and Climate Research at the Forschungszentrum Karlsruhe has enlarged the aircraft's research capabilities by the integration of a sensor package for the measurement of CO, NO, NO 2 . CO 2 and O 3 with frequencies between 1 Hz and 20 Hz, and detection limits of 1 ppb. The equipment does not only allow to detect mean quantities, but also, using the eddy-correlation technique, to calculate small-scale turbulent trace gas fluxes, e.g. caused by secondary circulation systems, mountain venting, convective cells and other mass transport processes between the boundary layer and the free troposphere (handover). Such data are of great importance to many aspects of air pollution dispersion and air pollution modelling. Process studies of the small-scale vertical transport of heat, moisture and trace gases and their parametrisation are some of these aspects. The function of the sensor package is shown by calibration results, intercomparison of the measurements of redundant sensors and spectral analysis of the wind components. Examples of the detection of secondary circulation systems, of the micro structure of trace gases in urban plumes and the calculation of ozone flux profiles are given.

Radar–Acoustic Detection of Aircraft Wake Vortices

All aircraft produce trailing wake vortices as a direct consequence of generating lift. Vortices may be dangerous to following aircraft during takeoff and landing. An all-weather airport wake vortex sensor has been sought for more than 25 years as part of a ground-based wake vortex avoidance system that would enable current U.S. Federal Aviation Administration separation standards to be safely reduced under instrument and visual flight rule conditions. A sensitive all-weather radar–acoustic wake vortex sensor is described that satisfies wake vortex avoidance system requirements. Samples of recent vortex data gathered at New York’s Kennedy International Airport are presented.

Why IFR?

Introduction: Air medical services can use aircraft equipped to fly under visual flight rules (VFR) or instrument flight rules (IFR). IFR allows the pilot to fly safely into lower weather minimums, potentially increasing the number of EMS flights that can be completed. We examined the advantages and disadvantages of both methods of helicopter flight, the potential service gain with IFR capability, and the financial feasibility of using IFR in an urban air medical program. Methods: Retrospective data were collected on the number of missed flights for Vanderbilt LifeFlight during a 6-year period. Focusing on 2 recent years, we examined the number of flights missed because of weather. Data were prospectively obtained on missed flights that could have been completed with IFR from April 1997 to March 1998. Financial estimates were calculated to determine the revenue potential of an IFR program. Results: An average of 24% of flights were missed from 1991 to 1997. In 1996–97, primary reasons for missed flights included poor visibility and low clouds, conditions in which IFR capable helicopters could fly. Prospective data from 1997–98 indicated an average of 6.7 missed flights per month potentially could have been completed with IFR. Analysis of expenses and revenue suggest that converting a ship from VFR to IFR, which involves both equipment purchases and pilot training, is economically feasible given the potential revenue gained by the number of flights completed during marginal weather conditions. Conclusion: Implementing an IFR program increases the safety margin and allows better EMS service to the community.

単独計器飛行時のワークロード評価法に関する研究

Operations under single pilot instrument flight rules for general aviation aircraft are known to be one of the most demanding pilot tasks. Pilot workload measurements using a PC-based flight simulator have been done to investigate pilot skills and the pilot workload. A pilot workload evaluation method has been established that is partly based on the time and motion studies and that mainly concentrates on the pilot's information processing. The time-record of pilot's eye movement has been used for the evaluation. Pilots who have different flight experiences attended the tests. Comparisons between the results by experienced pilots and those by novice pilots were made. It was shown that the relatively correct pilot workload has been evaluated by the present method. Results for the VOR tracking flight showed that the workload of the experienced pilots increases only when the airplane attitude has been changed, while results of the novice pilots show high workload continuously during the whole flight.

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Symposium: Decision Making in Free Flight

In its web-page introduction to free flight, the Federal Aviation Administration (FAA) describes free flight as “an innovative concept to improve the efficiency of the National Airspace System [in which] pilots operating under instrument flight rules will be able to select the aircraft's course, speed, and altitude in real time” (FAA, 1996). This symposium presents the results of experimental and theoretic investigations on (1) the ability of pilots and air traffic managers to master the demands of free flight and (2) the design of technology and decision aids tailored to need those demands.

Effectiveness of PC-Based Flight Simulation

PC-based flight-simulation effectiveness was analyzed through a transfer-of-learning study. Sixty college students with no previous flight experience performed a designated-aircraft maneuver. Thirty of the subjects were trained in a computer-based training device (CBTD) before flying; the remaining 30 were taken directly to the aircraft. Chi-square and t test analyses on the data revealed a statistical advantage at the .01 level of confidence for the CBTD-trained experimental group, which performed significantly better than the control group. The CBTD chosen for this study was AzureSoft's Electronic Instrument Flight Rules Environment (ELITE™), run on a Zenith personal computer. Cessna 150 and 152 aircraft were used for the flight portion of the study. The incorporation of CBTDs in flight training is recommended because they have the potential for reducing the amount of hours spent in the airplane.

Preventing and controlling inadvertent IFR

Inadvertent instrument flight rules (IFR) encounters are some of the most harrying conditions a pilot can experience. They also result in the highest percentage of death from helicopter crashes. Yet, inadvertent IFR can be prevented to some degree, and if encountered, it can be conquered and survived. Pilots must have strong identities but also must follow strict rules as to when they can and cannot fly. Training, such as following the "four Cs"--control, climb, course and confess--and instruments can bring pilots through inadvertent IFR successfully, but legal questions remain.

RAIM Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting1

In late 1991, the FAA formed a group called the Satellite Operational Implementation Team to accelerate the introduction of satellite navigation and communications into the National Airspace System (NAS). Since then, the team has been addressing major technical and operational issues that need to be resolved before GPS is used in instrument flight rules (IFR) operations in the NAS. One of the most critical criteria for the operational approval of near-term use of GPS in the NAS is availability of receiver autonomous integrity monitoring (RAIM) detection and identification functions. To improve RAIM availability, SOFT members suggested that relatively simple GPS augmentations in the form of barometric altimeter aiding and clock coasting be considered. This paper analyzes GPS RAIM availability with these augmentations and presents the technical analyses used by the team to support its recommendations.

Knowledge Based Cockpit Assistant for Controlled Airspace Flight Operation

Abstract A knowledge based cockpit assistant for flight operation under Instrument Flight Rules (IFR) is presented. The system is aimed at improvement of situation assessment including monitoring of the pilot crew activities and performance increase by computer aids for flight planning and plan execution. The modular system structure is described as well as the individual system modules. A first prototype of this Cockpit Assistant was tested about two years ago in a flight simulator at the University of the German Armed Forces in Munich by professional pilots under realistic IFR-scenarios. The results of these test runs proving enhancements in overall system performance are presented.

Factors associated with the safety of EMS helicopters

The accident rate for emergency medical service (EMS) helicopters is thought to be approximately twice the rate for other commercial (Part 135) helicopters. This observation has led to numerous news reports and to the publication of conclusions of a National Transportation Safety Board investigation. The data for these reports come from investigations of EMS helicopter accidents and incidents. The authors surveyed all listed civilian EMS helicopter programs to examine both helicopter ambulance mishaps and the number of safely completed missions. Epidemiological methods were then used to compare the safety records of different groups of EMS helicopters. The single most important factor identified was the number of flights made by the program during the study period: busy programs had an eightfold lower accident rate ( P < .0005) and a three-fold lower total mishap (accidents + incidents) rate ( P < .0005) than less active programs. Programs with the ability to fly under instrument flight rules (IFR) at the pilots discretion had no mishaps ( P = .044) during the study period. Multivariate analysis shows this IFR capability to be marginally significant as an independent factor ( P = .099).