Dissertations / Theses on the topic 'Helicopter flight operations'

Thesis (M.S. in Computer Science) Naval Postgraduate School, September 1995.
"September 1995." Thesis advisor(s): Michael J. Zyda, John S. Falby. Includes bibliographical references (p. 107). Also available online.

This dissertation focuses on constrained control of two applications: helicopter and ocean current turbines (OCT). A major contribution in the helicopter application is a novel model predictive control (MPC) framework for helicopter shipboard operations in high demanding sea-based conditions. A complex helicopter-ship dynamics interface has been developed as a system of implicit nonlinear ordinary differential equations to capture essential characteristics of the nonlinear helicopter dynamics, the ship dynamics, and the ship airwake interactions. Various airwake models such as Control Equivalent Turbulence Inputs (CETI) model and Computation Fluid Dynamics (CFD) data of the airwake are incorporated in the interface to describe a realistic model of the shipborne helicopter. The feasibility of the MPC design is investigated using two case studies: automatic deck landing during the ship quiescent period in sea state 5, and lateral reposition toward the ship in different wind-over-deck conditions. To improve the overall MPC performance, an updating scheme for the internal model of the MPC is proposed using linearization around operating points. A mixed-integer MPC algorithm is also developed for helicopter precision landing on moving decks. The performance of this control structure is evaluated via numerical simulations of the automatic deck landing in adverse conditions such as landing on up-stroke, and down-stroke moving decks with high energy indices. Kino-dynamic motion planning for coordinated maneuvers to satisfy the helicopter-ship rendezvous conditions is implemented via mixed integer quadratic programming. In the OCT application, the major contribution is that a new idea is leveraged from helicopter blade control by introducing cyclic blade pitch control in OCT. A minimum energy, constrained control method, namely Output Variance Constrained (OVC) control is studied for OCT flight control in the presence of external disturbances. The minimum achievable output variance bounds are also computed and a parametric study of design parameters is conducted to evaluate their influence on the OVC performance. The performance of the OVC control method is evaluated both on the linear and nonlinear OCT models. Furthermore, control design for the OCT with sensor failures is also examined. Lastly, the MPC strategy is also investigated to improve the OCT flight control performance in simultaneous satisfaction of multiple constraints and to avoid blade stall.
Ph. D.

Helicopter operations in the vicinity of small naval surface vessels often require excessive pilot workload. Because of the unsteady flow field and large mean velocity gradients, the envelope for flight operations is limited. This experimental investigation uses a 1:144 scale model of the U.S. Navy destroyer DDG-81 to explore the problem. Both active and passive flow control techniques were used to improve the flow field in the helicopterâ s final decent onto the flight deck. Wind tunnel data was collected at a set of grid points over the shipâ s flight deck using a single component hotwire. Results show that the use of porous surfaces decreases the unsteadiness of the flow field. Further improvements are found by injecting air through these porous surfaces, causing a reduction in unsteadiness in the landing region of 6.6% at 0 degrees wind-over-deck (WOD) and 8.3% at 20 degrees WOD. Other passive configurations tested include fences placed around the hangar deck edges which move the unsteady shear layer away from the flight deck. Although these devices cause an increase in unsteadiness downstream of the edge of the fence when compared to the baseline, the reticulated foam fence caused an overall decrease in unsteadiness in the landing region of 12.1% at 20 degrees WOD.
Master of Science

Les limitations d’atterrissage des hélicoptères ne sont pas valables dans l'environnement à bord d’un navire. Il n'existe aucune méthodologie approuvée de l'analyse ou de la simulation pour évaluer la compatibilité des hélicoptères-navires et préparer les essais de qualification hélicoptères-navires. Dans ce contexte, le présent travail présente le développement et l'analyse d'une méthodologie hors ligne pour déterminer les limites opérationnelles hélicoptères-navires, SHOLs, en fonction des prédictions d’un modèle de pilote humain. Pour cela, des essais pilotés par des humains sont effectués au simulateur de l’ONERA, Salon de Provence. Sur la base des résultats de ces tests, une méthodologie innovante est validée pour déterminer la limitation de la charge de travail de pilotage, à partir des mesures des déplacements des contrôles d'hélicoptère. En outre, sont validés des modifications innovantes sur un modèle de pilote humain pour pouvoir suivre les trajectoires souhaitées et fournir le même niveau d'activité aux contrôles qu'un véritable pilote. Un ensemble de critères objectifs, correspondant aux marges de sécurité, s'ajoute aux critères subjectifs, correspondant aux limitations de la charge de travail du pilote. Une routine de simulation hors ligne, appelée SholSim, est programmée pour réaliser des simulations avec le modèle pilote et vérifier l'acceptabilité des conditions de vol, selon les critères subjectifs et objectifs. Par conséquent, le présent travail présente la première estimation, dans la littérature, des SHOLs entièrement obtenus à partir d'outils hors ligne, basés uniquement sur les prédictions de modèle pilote
Helicopter land-based limitations are not valid in the shipboard environment. There is no analytical or simulated approved methodology for evaluating shipboard helicopter compatibility issues and preparing for at-sea flight tests. In this context, the present work presents the development and analysis of an offline methodology to determine the Ship-Helicopter Operating Limitations, SHOLs, based on pilot model predictions. For this, pilot-in-the-loop simulation trials are performed at the engineering fixed-base simulation facility of ONERA, Salon de Provence. Based on these test results, an innovative methodology is proposed and validated to determine the safe pilot workload limitation, from the measurements of the helicopter control displacements. In addition, it is proposed and validated innovative modifications on a classical pilot model enabling to follow complex predefined desired trajectories and provide the same level of control activity of a real pilot. A set of objective criteria, corresponding to the safety margins, is established in addition to the subjective criteria, corresponding to the safe pilot workload limitations. An offline simulation routine, so-called SholSim, is coded to run all models and verify the acceptability of the flight conditions, according to the subjective and objective criteria. Therefore, the present work presents the first estimation, in the literature, of the SHOLs fully obtained from offline tools, based only on pilot model predictions. The proposed methodology is promising, confirmed by predicting coherent limits when compared to the ones defined by the pilot-in-the-loop simulation trials

Approved for public release; distribution is unlimited
Usage Monitoring requires accurate regime recognition. For each regime, there is a usage assigned for each component. For example, the damage accumulated at a component is higher if the aircraft is undergoing a high G maneuver than in level flight. The objective of this research is to establish regime recognition models using classification algorithms. The data used in the analysis are the parametric data collected by the onboard system and the actual data, consisting of the correct regime collected from the flight cards. This study uses Rpart (with a tree output) and C5.0 (with a ruleset output) to establish two different models. Before model fitting, the data was divided into smaller datasets that represent regime families by subsetting using important flight parameters. Nonnormal tolerance intervals are constructed on the uninteresting values; then these values in the interval are set to zero to be muted (e.g. excluded). These processes help reduce the effect of noise on classification. The final models had correct classification rates over 95%. The number of bad misclassifications were minimized (e.g. the number of bad misclassifications of a level flight regime as a hover regime was minimized), but the models were not as powerful in classifying the low-speed regimes as in classifying high-speed regimes.
Outstanding Thesis

Military helicopter operations require precise maneuverability characteristics for performance to be determined for the entire helicopter flight envelope. Historically, these maneuverability analyses are combinatorial in nature and involve human-interaction, which hinders their integration into conceptual design. A model formulation that includes the necessary quantitative measures and captures the impact of changing requirements real-time is presented. The formulation is shown to offer a more conservative estimate of maneuverability than traditional energy-based formulations through quantitative analysis of a typical pop-up maneuver. Although the control system design is not directly integrated, two control constraint measures are deemed essential in this work: control deflection rate and trajectory divergence rate. Both of these measures are general enough to be applied to any control architecture, while at the same time enable quantitative trades that relate overall vehicle maneuverability to control system requirements. The dimensionality issues stemming from the immense maneuver space are mitigated through systematic development of a maneuver taxonomy that enables the operational envelope to be decomposed into a minimal set of fundamental maneuvers. The taxonomy approach is applied to a helicopter canonical example that requires maneuverability and design to be assessed simultaneously. The end result is a methodology that enables the impact of design choices on maneuverability to be assessed for the entire helicopter operational envelope, while enabling constraints from control system design to be assessed real-time.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, June 2004.
Thesis advisor(s): Lyn R. Whitaker, Arnold H. Buss. Includes bibliographical references (p. 77-78). Also available online.

Carefree handling refers to the ability of a pilot to operate an aircraft without the need to continuously monitor aircraft operating limits. At the heart of all carefree handling or maneuvering systems, also referred to as envelope protection systems, are algorithms and methods for predicting future limit violations. Recently, envelope protection methods that have gained more acceptance, translate limit proximity information to its equivalent in the control channel. Envelope protection algorithms either use very small prediction horizon or are static methods with no capability to adapt to changes in system configurations. Adaptive approaches maximizing prediction horizon such as dynamic trim, are only applicable to steady-state-response critical limit parameters. In this thesis, a new adaptive envelope protection method is developed that is applicable to steady-state and transient response critical limit parameters. The approach is based upon devising the most aggressive optimal control profile to the limit boundary and using it to compute control limits. Pilot-in-the-loop evaluations of the proposed approach are conducted at the Georgia Tech Carefree Maneuver lab for transient longitudinal hub moment limit protection. Carefree maneuvering is the dual of carefree handling in the realm of autonomous Uninhabited Aerial Vehicles (UAVs). Designing a flight control system to fully and effectively utilize the operational flight envelope is very difficult. With the increasing role and demands for extreme maneuverability there is a need for developing envelope protection methods for autonomous UAVs. In this thesis, a full-authority automatic envelope protection method is proposed for limit protection in UAVs. The approach uses adaptive estimate of limit parameter dynamics and finite-time horizon predictions to detect impending limit boundary violations. Limit violations are prevented by treating the limit boundary as an obstacle and by correcting nominal control/command inputs to track a limit parameter safe-response profile near the limit boundary. The method is evaluated using software-in-the-loop and flight evaluations on the Georgia Tech unmanned rotorcraft platform- GTMax. The thesis also develops and evaluates an extension for calculating control margins based on restricting limit parameter response aggressiveness near the limit boundary.

碩士
崑山科技大學
資訊管理研究所
107
With the modernization of the Armed Forces in China, the CCP's technology is developing rapidly by the along of economic growth recently. Consequently, its weapons and equipments were evolving with each passing day. No matter from information, missiles, and space technology, it is far superior compared to the armed force. Especially, the CCP accelerated the missile's ability to project capability with the high precision after the Gulf War. The ability to anti-missile is an important part of high-tech for long-distance missile projection. In response to the military threats, this studt focuses on using the AH-64E attack helicopter combined with the UAS system to perform an anti-armor attack as follows: 1. How to preserve the combat power under the threat of enemy forces, missiles, air forces and other threats, by incorpotating AH-64E attack helicopter with unmanned aerial vehicle (UAV) system, to assist the commander recognize the whole battlefield. The solution makes it play an important role in defeating the enemy, which means first seeking the whole army and then defeating the enemy. 2. The army continuly gains the AH-64E attack helicopter and UH-60M universal. By incorporating helicopter with UAV information, communication advantages, and the AH-64E attack helicopter, it will expand the battlefield intelligence integration function, speed up the target timeliness and enhance the target strike capability, and make the land navigation operations more effective.

碩士
國立成功大學
高階管理碩士在職專班
94
In the passed decade, the average accident rate is approximately 1.66 mishaps per million flight hours for the Republic of China (ROC) civil aircraft and it is 3.07 times of the World's average --- 0.54 mishaps per million flight hours. In addition, the average accident rate is 34.08 mishaps per 100,000 flight hours for the ROC rotor-wing aircraft while it is 8.74 for the USA rotor-wing aircraft. The ROC helicopter accident rate is almost 4 times of the USA accident rate. According to the data I mentioned above, the ROC flight safety is a concern when it is compared to the current world's flight safety level, especially the flight safety for helicopters. However, there are few exclusive researches for helicopter flight safety among the countless researches related to aviation/flight safety. As we know, flight safety is affected by many factors. The accident statistics tell us that the 70% flight accidents are caused by human factors. The purpose of this study is to determine the critical human factors that affect helicopter flight safety most and figure out a way to improve the flight safety level in our country. We include "Organization" among the SHEL model (Software, Hardware, Environment, and Liveware) to establish the HELLOS model which is emphasized on "liveware and liveware(s)" because we found that the human factors in accident were evolving from "individual" to "group". We hope the HELLOS could be more completed for analyzing the human factors. In this study, we received diverse data from government, civilian airlines, and militarizes and used quantitative methods for research. After factor screening and priority sorting, we draw a chart with quantitative scale called "Human Risk Factor for Helicopter Flight Safety", including 5 topical subjects and 17 factors. The priority order of topical subjects is: 1. Liveware and liveware. 2. Liveware and software. 3. Liveware and organization. 4. Liveware and environment. 5. Liveware and hardware.The 17 factors discussed in each topical subject are(Selections of first 10 item in 17): 1. Follow the Crew Resource Management (CRM) principles or not? 2. Flight safety cognition. 3. Environment or the vibration caused by aircraft. 4. The unhealthy equipment. 5. Pilot self-discipline. 6. Standard Operating Procedure (SOP) or regulations are feasible or not? 7. Familiar with the upcoming mission or not? 8. Training is valid or not? 9. Follow SOP exactly?10. Pilots' physiological functions. According to the affections and feasibilities of factors, we create the "Policy Schema" and divide those factors into the first priority group, priority planning group, flexible integration group, and long-term planning group. Policymakers refer to the distributions of those factors in Policy Schema and resources available for decision-making. A remarkable and effective flight safety improvement with minimum investment should be expected.

碩士
國防大學理工學院
造船及海洋工程碩士班
99
The exhausted gases from ships upper smoke are corrosive. They will erode and pollute the equipments on the deck, harm the people’s health on the ship deck, even threat the flight crew’s safety. So, predicting the plume trajectory is necessary and helpful. The factors influent the plume flow are numerous and complicated, such as wind velocity, exhausted gases velocity from the plume, the plume temperature, the plume height, the front structures, and so on, all of them will affect the gases flow. For preventing the gases create damage, we need to make design to change its path for decreasing the possibility to hurt the people and machine, the more important is to ensure the flight crew’s safety. This paper will use CFD(Computational Fluid Dynamics) to simulate the ship plume flow and helicopter’s motion, and will analysis the Perry Class vessel and the helicopter S70-C. The purpose is to discuss the influent from superstructures, the shape of the plume, the wind deflectors, and the helicopter’s motion. In the helicopters part, we will use the sliding mesh technique to simulate the flow when the helicopter is hovering, and establish the ship model to provide the ship design and development.

碩士
國立成功大學
航空太空工程學系專班
101
In the process of aviation evolution, the structure of airframe, composite materials and the power technology improve persistently. The primary goal of all these improvement was to speed up the aircraft, increase the flight altitude, extend travel distance, and expand the carrying capacity. Nevertheless, the complexity of aviation system has been influencing pilot's aircraft manipulation. Statistics showed, according to ICAO, that more than 70 percent of aircraft accidents directly or indirectly related to incorrect pilot manipulation. Therefore, the modern aviation system has introduced the concept of human factors engineering to interface of flight instruments cockpit and integrated them into the digital avionics system. This research probes the influence of digital avionics upon pilot's ability training. In the flight of pilot's training and achievement, both of the TH-67 helicopter simulator equipped with analogical flight instruments and CH-47SD full digital flight instruments cockpit are applied to sample and analyze pilot operation margin verity and emergency manipulation procedures. This research also deeply proves that digital avionics do improve pilot's flight manipulation and aviation security efficiency. 645 items of flight emergency procedures are exercised with 396 effective sampling adopted (including 216 of helicopter simulator and 180 of actual aircraft). Under deliberate analysis, the quantification data has verified that the digital avionics can provide pilots with a larger operation margin and shorten the judgment time under emergency situation. It is very obvious to see that the digital avionics can not only alleviate pilot's pressure but also enhance the aviation security.

碩士
國防大學中正理工學院
兵器系統工程研究所
94
In this thesis, the investigation of onboard helicopter flight safe operating envelopes in different kinds of sea conditions set by flying qualities during landing are of particular interest. This thesis includes five key steps: Firstly, incorporating the six degree-of-freedom equations of motion and the steady-state airwake on the flight deck, the helicopter/ship recovery model is established. Second, we analyse the influence of ship speed and wave cycle to the ship motions in different kinds of sea conditions. Third, three kinds of controller are designed by flight quality to simulate the driving technologies and experiences of the three levels of pilot. The Quickness Criteria flight qualities in ADS-33 are introduced to determine the closed loop poles. Fourth, we define the theoretical flight safe operating envelope of onboard helicopter and the simulation processes to determine the theoretical flight safe operating envelope for helicopter landing on a ship. Fifth, the differences of the theoretical flight safe operating envelopes in different kinds of sea conditions and controllers are studied. Finally, we use of Matlab in Virtual reality Toolbox to simulate the scene when a helicopter lands on a ship. This thesis is expected to be helpful to the pilot training, flight safety and analysis of the margin of the helicopter/ship flight safe operating envelope.