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Infant Follow Up Programs (IFUPs) provide developmental surveillance for preterm infants after hospital discharge but participation is variable. We hypothesized that infants born to Black mothers, non-English speaking mothers, and mothers who live in “Very Low” Child Opportunity Index (COI) neighborhoods would have decreased odds of IFUP participation. There were 477 infants eligible for IFUP between 1/1/2015 and 6/6/2017 from a single large academic Level III NICU. Primary outcome was at least one visit to IFUP. We used multivariable logistic regression to identify factors associated with IFUP participation. Two hundred infants (41.9%) participated in IFUP. Odds of participation was lower for Black compared to white race (aOR 0.43, p = 0.03), “Very Low” COI compared to “Very High” (aOR 0.39, p = 0.02) and primary non-English speaking (aOR 0.29, p = 0.01). We identified disparities in IFUP participation. Further study is needed to understand underlying mechanisms to develop targeted interventions for reducing inequities.

Objective The COVID-19 pandemic has altered the delivery of follow-up care for high-risk infants. We performed an audit to characterize programmatic responses in a quality improvement network. Study design We audited 43 North American-based follow-up programs of the Vermont Oxford Network Extremely Low Birth Weight Follow-up Study Group in October, 2020. Our electronic survey included yes/no, agree/disagree, and free text response items. Result The response rate was 67.4%. Most programs altered capacity and the timing, frequency, or content of clinical assessments. Most perceived practice changes compromised their ability to ascertain infants' medical and developmental needs. There was a rapid uptake of telemedicine services. Despite challenges with implementation, many endorsed improved connectedness with families. Conclusion Programs adapted rapidly to meet the needs of high-risk infants during the pandemic. Clinical operations, assessment procedures, and quality metrics will also need to evolve. Quality improvement study group collaboratives are well-positioned to coordinate such work.

Background Difficulties related to eating are often reported in children born preterm. The objective of this study was to quantitatively synthesize available data on the prevalence of problematic feeding in children under 4 years of age who were born preterm. Methods Literature was identified from PubMed, CINAHL, and PsycInfo. The search was limited to English language and publication years 2000–2020. To be included in the meta-analysis, the article had to report the prevalence of problematic oral feeding within a population of children born prematurely ( Results There were 22 studies that met inclusion criteria. Overall prevalence of problematic feeding (N = 4381) was 42% (95% CI 33–51%). Prevalence was neither significantly different across categories of gestational age nor by child age at the time of study. Few studies used psychometrically-sound assessments of feeding. Conclusion Problematic feeding is highly prevalent in prematurely-born children in the first 4 years of life regardless of degree of prematurity. Healthcare providers of children born preterm should consider screening for problematic feeding throughout early childhood as a potential complication of preterm birth. Systematic review registration number Not applicable.

Preterm infants are a population at high risk for mortality and adverse health outcomes. With recent improvements in survival to childhood, increasing attention is being paid to risk of long-term morbidity, specifically during childhood and young-adulthood. Although numerous tools for predicting the functional outcomes of preterm neonates have been developed in the past three decades, no studies have provided a comprehensive overview of these tools, along with their strengths and weaknesses. The purpose of this article is to provide an in-depth, narrative review of the current risk models available for predicting the functional outcomes of preterm neonates. A total of 32 studies describing 43 separate models were considered. We found that most studies used similar physiologic variables and standard regression techniques to develop models that primarily predict the risk of poor neurodevelopmental outcomes. With a recently expanded knowledge regarding the many factors that affect neurodevelopment and other important outcomes, as well as a better understanding of the limitations of traditional analytic methods, we argue that there is great room for improvement in creating risk prediction tools for preterm neonates. We also consider the ethical implications of utilizing these tools for clinical decision-making. Impact Based on a literature review of risk prediction models for preterm neonates predicting functional outcomes, future models should aim for more consistent outcomes definitions, standardized assessment schedules and measurement tools, and consideration of risk beyond physiologic antecedents.Our review provides a comprehensive analysis and critique of risk prediction models developed for preterm neonates, specifically predicting functional outcomes instead of mortality, to reveal areas of improvement for future studies aiming to develop risk prediction tools for this population.To our knowledge, this is the first literature review and narrative analysis of risk prediction models for preterm neonates regarding their functional outcomes.

Maternal nutrition is an important factor for infant neurodevelopment. However, prior magnetic resonance imaging (MRI) studies on maternal nutrients and infant brain have focused mostly on preterm infants or on few specific nutrients and few specific brain regions. We present a first study in term-born infants, comprehensively correlating 73 maternal nutrients with infant brain morphometry at the regional (61 regions) and voxel (over 300 000 voxel) levels. Both maternal nutrition intake diaries and infant MRI were collected at 1 month of life (0.9 ± 0.5 months) for 92 term-born infants (among them, 54 infants were purely breastfed and 19 were breastfed most of the time). Intake of nutrients was assessed via standardized food frequency questionnaire. No nutrient was significantly correlated with any of the volumes of the 61 autosegmented brain regions. However, increased volumes within subregions of the frontal cortex and corpus callosum at the voxel level were positively correlated with maternal intake of omega-3 fatty acids, retinol (vitamin A) and vitamin B12, both with and without correction for postmenstrual age and sex (P

Supplemental Digital Content is available in the text., Objectives: To establish the first regional quality improvement collaborative solely dedicated to follow-through care of high-risk infants after Neonatal intensive care unit (NICU) discharge and to characterize extremely low birth weight (ELBW) follow-up in New England. Methods: Eleven of 14 follow-up programs in New England partnered with the Vermont Oxford Network (VON) ELBW project for an initial data collection project. We collected information about the health status and developmental outcomes of infants born ≤1,000 g or younger than 28 weeks 2014–2016 at the 18–24 months corrected for gestational age (CGA) follow-up visit. VON collected and compiled the data. Results: Of 993 eligible infants, 516 (52.0%) had follow-up visits. The rehospitalization rate was 33.9%, mostly respiratory illness. Ninety-six children (19.3%) had weight less than 10th percentile and 44 (8.9%) had weight less than third percentile at 18–24 months. Only 170 (61.4%) children had recommended hearing screening after NICU discharge. Forty-six (9.1%) had cerebral palsy; 81 of the 441 infants that completed all 3 sections of the Bayley Scales of Infant Development, third edition (18.4%) had any composite score less than 70. Over half of the social and demographic data were missing. Conclusion: Most quality initiatives in neonatology stop at NICU discharge. This first project by the New England Follow-up Network showed a low rate for clinical follow-up. It demonstrated many opportunities to improve postdischarge follow-through specific to NICU-based care. Future projects will aim to improve the quality of follow-through services through collaborative learning, data sharing, and comparative outcomes.

As the technical ability for genetic diagnosis continues to improve, an increasing number of diagnoses are made in infancy or as early as the neonatal period. Many of these diagnoses are known to be associated with developmental delay and intellectual disability, features that would not be clinically detectable at the time of diagnosis. Others may be associated with cognitive impairment, but the incidence and severity are yet to be fully described. These neonates and infants with genetic diagnoses therefore represent an emerging group of patients who are at high risk for neurodevelopmental disabilities. Although there are well-established developmental supports for high-risk infants, particularly preterm infants, after discharge from the NICU, programs specifically for infants with genetic diagnoses are rare. And although previous research has demonstrated the positive effect of early developmental interventions on outcomes among preterm infants, the impact of such supports for infants with genetic disorders who may be born term, remains to be understood. We therefore review the literature regarding existing developmental assessment and intervention approaches for children with genetic disorders, evaluating these in the context of current developmental supports postdischarge for preterm infants. Further research into the role of developmental support programs for early assessment and intervention in high-risk neonates diagnosed with rare genetic disorders is needed.

The normal development of thalamocortical connections plays a critical role in shaping brain connectivity in the prenatal and postnatal periods. Recent studies using advanced magnetic resonance imaging (MRI) techniques in neonates and infants have shown that abnormal thalamocortical connectivity is associated with adverse neurodevelopmental outcomes. However, all these studies have focused on a single neuroimaging modality, overlooking the dynamic relationship between structure and function at this early stage. Here, we study the relationship between structural and functional thalamocortical connectivity patterns derived from healthy full-term infants scanned with diffusion-weighted MRI and resting-state functional MRI within the first weeks of life (mean gestational age = 39.3 ± 1.2 weeks; age at scan = 24.2 ± 7.9 days). Our results show that while there is, in general, good spatial agreement between both MRI modalities, there are regional variations that are system-specific: regions involving primary-sensory cortices exhibit greater structural/functional overlap, whereas higher-order association areas such as temporal and posterior parietal cortices show divergence in spatial patterns of each modality. This variability illustrates the complementarity of both modalities and highlights the importance of multimodal approaches.

Pregnancy and lactation can change the maternal nutrient reserve. Non-invasive, quantitative markers of maternal nutrient intake could enable personalized dietary recommendations that improve health outcomes in mothers and infants. Macular pigment optical density (MPOD) is a candidate marker, as MPOD values generally reflect carotenoid intake. We evaluated the association of MPOD with dietary and breastmilk carotenoids in postpartum women. MPOD measurements and dietary intake of five carotenoids were obtained from 80 mothers in the first three months postpartum. Breastmilk samples from a subset of mothers were analyzed to determine their nutrient composition. The association between MPOD and dietary or breastmilk carotenoids was quantitatively assessed to better understand the availability and mobilization of carotenoids. Our results showed that dietary α-carotene was positively correlated with MPOD. Of the breastmilk carotenoids, 13-cis-lutein and trans-lutein were correlated with MPOD when controlled for the total lutein in breastmilk. Other carotenoids in breastmilk were not associated with MPOD. Maternal MPOD is positively correlated with dietary intake of α-carotene in the early postpartum period, as well as with the breastmilk content of lutein. MPOD may serve as a potential marker for the intake of carotenoids, especially α-carotene, in mothers in the early postpartum period.

BACKGROUND: Extremely low birth weight (ELBW; 2500 grams) children followed to 8 years. ELBW children were more likely to have asthma (35.7% vs. 14.4%, p

Leukocyte telomere length is a biomarker of aging-related health risks. Hospitalized preterm infants frequently experience elevated oxidative stress and inflammation, both of which contribute to telomere shortening. Our aim was to examine changes in telomere length during neonatal intensive care unit (NICU) hospitalization in a cohort of preterm infants

Premature delivery and a potential Neonatal Intensive Care Unit admission may be associated with the risk of poor maternal health. We aimed to examine the mothers’ health-related quality of life (HRQoL) at the time of infant discharge. Fifty mothers completed the Medical Outcomes Study-Short Form 12. It has a Physical Component Score (PCS) and Mental Component Score (MCS), both with a mean of 50 and standard deviation of 10. Analysis included infant, maternal, and pregnancy-related characteristics. In multivariable analyses, a household income of

This paper describes an approach to creating simulations of the electric components for a hybrid electric propulsion system. The proposed modeling technique is based on power/load flow modeling and is designed to provide a modular framework that includes buses, lines, and other electrical components that can be connected together to form the electrical distribution system. The purpose of this paper is to detail an electric distribution system modeling technique and to demonstrate how these models may be integrated with turbomachinery simulations. These general modeling techniques were created to be utilized for system and control design studies. Additionally, steady-state and dynamic performance for a proposed model example is compared with data from a hardware in the loop simulation.

The family-centered medical home (FCMH) is the recommended healthcare delivery model for children. It is unknown how frequently preterm (PT) children receive care in a FCMH and how this affects health services use. We studied 18,397 children aged 0–3 years in the 2010/2011 National Survey of Children’s Health. We compared PT (

The authors take a longitudinal and intergenerational approach to studying infants born at extremely early gestational age, highlighting the extent to which a high-risk pregnancy is experienced by both mother and infant, with potentially lasting effects on the physical – and mental – health of the dyad. They focus their study on what they call positive child health outcomes at 10 years of age, measured using an index of chronic health problems. Yet concepts of positive health include attributes beyond the absence of disease, such as participation, resilience, and happiness. To study positive health outcomes – an endeavor that has much merit in light of the developmental plasticity children possess – we should use measures that explicitly and more fully encompass the many facets of well-being. Otherwise, we risk simply rebranding negative disease as positive health by providing it a new name.

The following are the objectives of this study: (1) Assess the feasibility and acceptability of emailing parent-reported measures of infant health and development after NICU discharge. (2) Examine whether post-discharge questionnaire data helps identify infants most likely to benefit from specialized follow-up care. Parents of 51 infants

In this issue of Pediatrics , Spittle et al1 provide an important follow-up report at 8 years to their randomized trial of early intervention for very preterm infants. The intervention was delivered over 9 sessions during the first year of life and was based on a strong theoretical approach. The well-defined set of services aimed to enhance caretakers’ ability to foster the development of their children and to reduce parental stress.2 At planned follow-up assessments at 2 and 4 years of age,3,4 the authors found no difference between the intervention and control groups in the children’s cognitive, language, and motor scores. They did observe a persistent effect of the intervention on decreased mental health symptoms in caretakers at both points. The current follow-up was undertaken based on the relationship between child development and parental mental health, with the expectation that the persistent advantage in the intervention group would result in better child outcomes. The authors employed an expanded test battery to go beyond intelligence to examine specific domains of child cognitive development, attention, … Address correspondence to Marie C. McCormick MD, ScD, Department of Social and Behavioral Sciences, Harvard School of Public Health, 677 Huntington Ave, Boston, MA 02115. E-mail: mmccormi{at}hsph.harvard.edu

Gas turbine compressor and turbine blade tip clearance (i.e., the radial distance between the blade tip of an axial compressor or turbine and the containment structure) is a major contributing factor to gas path sealing, and can significantly affect engine efficiency and operational temperature. This paper details the creation of a generic but realistic high pressure turbine tip clearance model that may be used to facilitate active tip clearance control system research. This model uses a first principles approach to approximate thermal and mechanical deformations of the turbine system, taking into account the rotor, shroud, and blade tip components. Validation of the tip clearance model shows that the results are realistic and reflect values found in literature. In addition, this model has been integrated with a gas turbine engine simulation, creating a platform to explore engine performance as tip clearance is adjusted. Results from the integrated model explore the effects of tip clearance on engine operation and highlight advantages of tip clearance management.

The cost and risk associated with the design and operation of gas turbine engine systems has led to an increasing dependence on mathematical models. In this paper, the fundamentals of engine simulation will be reviewed, an example performance analysis will be performed, and relationships useful for engine control system development will be highlighted. The focus will be on thermodynamic modeling utilizing techniques common in industry, such as: the Brayton cycle, component performance maps, map scaling, and design point criteria generation. In general, these topics will be viewed from the standpoint of an example turbojet engine model; however, demonstrated concepts may be adapted to other gas turbine systems, such as gas generators, marine engines, or high bypass aircraft engines. The purpose of this paper is to provide an example of gas turbine model generation and system performance analysis for educational uses, such as curriculum creation or student reference.

It is probable that no two engine companies determine the life of their engines or their components in the same way or apply the same experience and safety factors to their designs. Knowing the failure mode that is most likely to occur minimizes the amount of uncertainty and simplifies failure and life analysis. Available data regarding failure mode for aircraft engine blades, while favoring low-cycle, thermal mechanical fatigue as the controlling mode of failure, are not definitive. Sixteen high-pressure turbine (HPT) T-1 blade sets were removed from commercial aircraft engines that had been commercially flown by a single airline and inspected for damage. Each set contained 82 blades. The damage was cataloged into three categories related to their mode of failure: (1) Thermal-mechanical fatigue, (2) Oxidation/Erosion, and (3) "Other." From these field data, the turbine blade life was determined as well as the lives related to individual blade failure modes using Johnson-Weibull analysis. A simplified formula for calculating turbine blade life and reliability was formulated. The L(sub 10) blade life was calculated to be 2427 cycles (11 077 hr). The resulting blade life attributed to oxidation/erosion equaled that attributed to thermal-mechanical fatigue. The category that contributed most to blade failure was Other. If there were there no blade failures attributed to oxidation/erosion and thermal-mechanical fatigue, the overall blade L(sub 10) life would increase approximately 11 to 17 percent.

Model predictive control is a strategy well-suited to handle the highly complex, nonlinear, uncertain, and constrained dynamics involved in aircraft engine control problems. However, it has thus far been infeasible to implement model predictive control in engine control applications, because of the combination of model complexity and the time allotted for the control update calculation. In this paper, a multiplexed implementation is proposed that dramatically reduces the computational burden of the quadratic programming optimization that must be solved online as part of the model-predictive-control algorithm. Actuator updates are calculated sequentially and cyclically in a multiplexed implementation, as opposed to the simultaneous optimization taking place in conventional model predictive control. Theoretical aspects are discussed based on a nominal model, and actual computational savings are demonstrated using a realistic commercial engine model.

High-risk infants are commonly referred to Visiting Nurse Association (VNA) agencies for post-hospitalization services after discharge from the neonatal intensive care unit (NICU). Little is known about the effectiveness and perceived benefits of routine VNA services for these infants. The objective of this study was to identify factors predictive of family satisfaction with VNA services after NICU discharge. This is an observational study using data collected from routine quality assurance phone calls to families after NICU discharge. The setting is a single NICU at a large, urban academic medical center in Boston, MA, USA. We included all hospitalized infants discharged from the NICU from 1 January 2008 to 31 July 2014. Predictors included markers of infant biological and social risk and a survey measure of parent and nurse perceptions of parents’ preparedness at discharge. The outcome was parent response to the question, ‘Did you find the VNA visit helpful?’ at 2 weeks post discharge. Bivariate analyses showed perceived helpfulness of VNA visits associated with low maternal parity, lower 1-min Apgar score, lower birth weight and gestational age, diagnosis of respiratory distress syndrome and intraventricular hemorrhage and low discharge readiness scores. Only low maternal parity (odds ratio (OR) 1.82, 95% confidence interval (CI) 1.35, 2.46) and birth

The National Aeronautics and Space Administration (NASA) has developed independent airframe and engine models that have been integrated into a single real-time aircraft simulation for piloted evaluation of propulsion control algorithms. In order to have confidence in the results of these evaluations, the integrated simulation must be validated to demonstrate that its behavior is realistic and that it meets the appropriate Federal Aviation Administration (FAA) certification requirements for aircraft. The paper describes the test procedures and results, demonstrating that the integrated simulation generally meets the FAA requirements and is thus a valid testbed for evaluation of propulsion control modes.

The development of a wavelet-based feature extraction technique specifically targeting FOD-event induced vibration signal changes in gas turbine engines is described. The technique performs wavelet analysis of accelerometer signals from specified locations on the engine and is shown to be robust in the presence of significant process and sensor noise. It is envisioned that the technique will be combined with Kalman filter thermal/health parameter estimation for FOD-event detection via information fusion from these (and perhaps other) sources. Due to the lack of high-frequency FOD-event test data in the open literature, a reduced-order turbofan structural model (ROM) was synthesized from a finite-element model modal analysis to support the investigation. In addition to providing test data for algorithm development, the ROM is used to determine the optimal sensor location for FOD-event detection. In the presence of significant noise, precise location of the FOD event in time was obtained using the developed wavelet-based feature.

A Data Fusion System designed to provide a reliable assessment of the occurrence of Foreign Object Damage (FOD) in a turbofan engine is presented. The FOD-event feature level fusion scheme combines knowledge of shifts in engine gas path performance obtained using a Kalman filter., with bearing accelerometer signal features extracted via wavelet analysis, to positively identify a FOD event. A fuzzy inference system provides basic probability assignments (bpa) based on features extracted from the gas path analysis and bearing accelerometers to a fusion algorithm based on the Dempster-Shafer-Yager Theory of Evidence. Details are provided on the wavelet transforms used to extract the foreign object strike features from the noisy data and on the Kalman filter-based gas path analysis. The system is demonstrated using a turbofan engine combined-effects model (CEM), providing both gas path and rotor dynamic structural response, and is suitable for rapid-prototyping of control and diagnostic systems. The fusion of the disparate data can provide significantly more reliable detection of a FOD event than the use of either method alone. The use of fuzzy inference techniques combined with Dempster-Shafer-Yager Theory of Evidence provides a theoretical justification for drawing conclusions based on imprecise or incomplete data.

The engine control system for civil transport aircraft imposes operational limits on the propulsion system to ensure compliance with safety standards. However, during certain emergency situations, aircraft survivability may benefit from engine performance beyond its normal limits despite the increased risk of failure. Accordingly, control modes were developed to improve the maximum thrust output and responsiveness of a generic high-bypass turbofan engine. The algorithms were designed such that the enhanced performance would always constitute an elevation in failure risk to a consistent predefined likelihood. This paper presents an application of these risk-based control modes to a combined engine/aircraft model. Through computer and piloted simulation tests, the aim is to present a notional implementation of these modes, evaluate their effects on a generic airframe, and demonstrate their usefulness during emergency flight situations. Results show that minimal control effort is required to compensate for the changes in flight dynamics due to control mode activation. The benefits gained from enhanced engine performance for various runway incursion scenarios are investigated. Finally, the control modes are shown to protect against potential instabilities during propulsion-only flight where all aircraft control surfaces are inoperable.

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically.

The Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) is a tool that has been developed to allow a user to build custom models of systems governed by thermodynamic principles using a template to model each basic process. Validation of this tool in an engine model application was performed through reconstruction of the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) (v2) using the building blocks from the T-MATS (v1) library. In order to match the two engine models, it was necessary to address differences in several assumptions made in the two modeling approaches. After these modifications were made, validation of the engine model continued by integrating both a steady-state and dynamic iterative solver with the engine plant and comparing results from steady-state and transient simulation of the T-MATS and C-MAPSS models. The results show that the T-MATS engine model was accurate within 3% of the C-MAPSS model, with inaccuracy attributed to the increased dimension of the iterative solver solution space required by the engine model constructed using the T-MATS library. This demonstrates that, given an understanding of the modeling assumptions made in T-MATS and a baseline model, the T-MATS tool provides a viable option for constructing a computational model of a twin-spool turbofan engine that may be used in simulation studies.

A modular thermodynamic simulation package called the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) has been developed for the creation of dynamic simulations. The T-MATS software is designed as a plug-in for Simulink (Math Works, Inc.) and allows a developer to create system simulations of thermodynamic plants (such as gas turbines) and controllers in a single tool. Creation of such simulations can be accomplished by matching data from actual systems, or by matching data from steady state models and inserting appropriate dynamics, such as the rotor and actuator dynamics for an aircraft engine. This paper summarizes the process for creating T-MATS turbo-machinery simulations using data and input files obtained from a steady state model created in the Numerical Propulsion System Simulation (NPSS). The NPSS is a thermodynamic simulation environment that is commonly used for steady state gas turbine performance analysis. Completion of all the steps involved in the process results in a good match between T-MATS and NPSS at several steady state operating points. Additionally, the T-MATS model extended to run dynamically provides the possibility of simulating and evaluating closed loop responses.

To investigate the association between thrombocytopenia and placental lesions.Cases included singleton infants admitted to the intensive care unit (2005 to 2010) with platelet counts100 000 μl(-1). We selected a contemporaneous control group matched for gestational age: 49 cases and 63 controls. The frequency of thrombosis in fetal vessels, fetal thrombotic vasculopathy, acute chorioamnionitis, chronic villitis, infarcts, hematomas, cord insertion and increased circulating nucleated red blood cells were identified on retrospective review of placental histology. Logistic regression models were used to test for associations.Placental lesions associated with poor maternal perfusion (odds ratio (OR) 3.36, 95% confidence interval (CI) 1.38, 8.15) or affecting fetal vasculature (OR 2.75, 95% CI 1.05, 7.23), but not inflammation, were associated with thrombocytopenia. A Pearson Chi-Square Test for Independence for fetal and maternal lesions indicated that the two are independent factors.Poor maternal perfusion and fetal vascular lesions are independently associated with thrombocytopenia in the newborn.

Tests are described which, when used to augment the existing periodic maintenance and pre-flight checks of T700 engines, can greatly improve the chances of uncovering a problem compared to the current practice. These test signals can be used to expose and differentiate between faults in various components by comparing the responses of particular engine variables to the expected. The responses can be processed on-line in a variety of ways which have been shown to reveal and identify faults. The combination of specific test signals and on-line processing methods provides an ad hoc approach to the isolation of faults which might not otherwise be detected during pre-flight checkout.

A design concept is presented for developing control modes that enhance aircraft engine performance during emergency flight scenarios. The benefits of increased engine performance to overall vehicle survivability during these situations may outweigh the accompanied elevated risk of engine failure. The objective involves building control logic that can consistently increase engine performance beyond designed maximum levels based on an allowable heightened probability of failure. This concept is applied to two previously developed control modes: an overthrust mode that increases maximum engine thrust output and a faster response mode that improves thrust response to dynamic throttle commands. This paper describes the redesign of these control modes and presents simulation results demonstrating both enhanced engine performance and robust maintenance of the desired elevated risk level.

A method of investigating the effects of high angle of attack (AOA) flight on turbofan engine performance is presented. The methodology involves combining a suite of diverse simulation tools. Three-dimensional, steady-state computational fluid dynamics (CFD) software is used to model the change in performance of a commercial aircraft-type inlet and fan geometry due to various levels of AOA. Parallel compressor theory is then applied to assimilate the CFD data with a zero-dimensional, nonlinear, dynamic turbofan engine model. The combined model shows that high AOA operation degrades fan performance and, thus, negatively impacts compressor stability margins and engine thrust. In addition, the engine response to high AOA conditions is shown to be highly dependent upon the type of control system employed.

A simplified open-loop dynamic model of the T700 turboshaft engine, valid within the normal operating range of the engine, is developed. This model is obtained by linking linear state space models obtained at different engine operating points. Each linear model is developed from a detailed nonlinear engine simulation using a multivariable system identification and realization method. The simplified model may be used with a model-based real time diagnostic scheme for fault detection and diagnostics, as well as for open loop engine dynamics studies and closed loop control analysis utilizing a user generated control law.

This paper describes the implementation and evaluation of a yaw rate to throttle feedback system designed to replace a damaged rudder. It can act as a Dutch roll damper and as a means to facilitate pilot input for crosswind landings. Enhanced propulsion control modes were implemented to increase responsiveness and thrust level of the engine, which impact flight dynamics and performance. Piloted evaluations were performed to determine the capability of the engines to substitute for the rudder function under emergency conditions. The results showed that this type of implementation is beneficial, but the engines’ capability to replace the rudder is limited.

This paper describes piloted evaluation of enhanced propulsion control modes for emergency operation of aircraft. Fast Response and Overthrust modes were implemented to assess their ability to help avoid or mitigate potentially catastrophic situations, both on the ground and in flight. Tests were conducted to determine the reduction in takeoff distance achievable using the Overthrust mode. Also, improvements in Dutch roll damping, enabled by using yaw rate feedback to the engines to replace the function of a stuck rudder, were investigated. Finally, pilot workload and ability to handle the impaired aircraft on approach and landing were studied. The results showed that improvement in all aspects is possible with these enhanced propulsion control modes, but the way in which they are initiated and incorporated is important for pilot comfort and perceived benefit.

This paper studies the effect of modifying the control limits of an aircraft engine to obtain additional performance. In an emergency situation, the ability to operate an engine above its normal operating limits and thereby gain additional performance may aid in the recovery of a distressed aircraft. However, the modification of an engine’s limits is complex due to the risk of an engine failure. This paper focuses on the tradeoff between enhanced performance and risk of either incurring a mechanical engine failure or compromising engine operability. The ultimate goal is to increase the engine performance, without a large increase in risk of an engine failure, in order to increase the probability of recovering the distressed aircraft. The control limit modifications proposed are to extend the rotor speeds, temperatures, and pressures to allow more thrust to be produced by the engine, or to increase the rotor accelerations and allow the engine to follow a fast transient. These modifications do result in increased performance; however this study indicates that these modifications also lead to an increased risk of engine failure.

The integration of flight control and propulsion control has been a much discussed topic, especially for emergencies where the engines may be able to help stabilize and safely land a damaged aircraft. Previous research has shown that for the engines to be effective as flight control actuators, the response time to throttle commands must be improved. Other work has developed control modes that accept a higher risk of engine failure in exchange for improved engine response during an emergency. In this effort, a nonlinear engine model (the Commercial Modular Aero-Propulsion System Simulation 40k) has been integrated with a nonlinear airframe model (the Generic Transport Model) in order to evaluate the use of enhanced-response engines as alternative yaw rate control effectors. Tests of disturbance rejection and command tracking were used to determine the impact of the engines on the aircraft’s dynamical behavior. Three engine control enhancements that improve the response time of the engine were implemented and tested in the integrated simulation. The enhancements were shown to increase the engine’s effectiveness as a yaw rate control effector when used in an automatic feedback loop. The improvement is highly dependent upon flight condition; the airframe behavior is markedly improved at low altitude, low speed conditions, and relatively unchanged at high altitude, high speed.

Aircraft engines can be effective actuators to help pilots avert or recover from emergency situations. Emergency control modes are being developed to enhance the engines performance to increase the probability of recovery under these circumstances. This paper discusses a proposed implementation of an architecture that requests emergency propulsion control modes, allowing the engines to deliver additional performance in emergency situations while still ensuring a specified safety level. In order to determine the appropriate level of engine performance enhancement, information regarding the current emergency scenario (including severity) and current engine health must be known. This enables the engine to operate beyond its nominal range while minimizing overall risk to the aircraft. In this architecture, the flight controller is responsible for determining the severity of the event and the level of engine risk that is acceptable, while the engine controller is responsible for delivering the desired performance within the specified risk range. A control mode selector specifies an appropriate situation-specific enhanced mode, which the engine controller then implements. The enhanced control modes described in this paper provide additional engine thrust or response capabilities through the modification of gains, limits, and the control algorithm, but increase the risk of engine failure. The modifications made to the engine controller to enable the use of the enhanced control modes are described, as are the interaction between the various subsystems and importantly, the interaction between the flight controller/pilot and the propulsion control system. Simulation results demonstrate how the system responds to requests for enhanced operation and the corresponding increase in performance.

*† ‡ § Enhanced engine operation—operation that is beyond normal limits—has the potential to improve the adaptability and safety of aircraft in emergency situations. Intelligent use of enhanced engine operation to improve the handling qualities of the aircraft requires sophisticated risk estimation techniques and a risk management system that spans the flight and propulsion controllers. In this paper, an architecture that weighs the risks of the emergency and of possible engine performance enhancements to reduce overall risk to the aircraft is described. Two examples of emergency situations are presented to demonstrate the interaction between the flight and propulsion controllers to facilitate the enhanced operation. I. Introduction n emergency situations, aircraft engines can be used as actuators to improve the capability and controllability of the aircraft. There are several examples of pilots using this technique in an attempt to recover and land a severely impaired aircraft. In 1972, an American Airlines DC-10 landed safely in Detroit after suffering damage that resulted in a stuck, offset rudder as well as partial elevator loss; 1 the pilot used asymmetric thrust to maintain heading. 2 In the 1985 JAL 123 accident, the Boeing 747 lost all hydraulics as well as suffering severe vertical tail loss, which excited the dutch roll (coupled yaw and roll oscillations) and phugoid (long period pitch oscillations) modes. The pilots used asymmetric thrust to regain limited directional control but ultimately failed to recover and crashed with tremendous loss of life. 3 In the 1989 DC-10 accident in Sioux City, Iowa, the plane lost hydraulic power to all flight control surfaces, and there was some tail damage. Here, the phugoid was much more of a problem than the dutch roll, and the crew was able to maintain enough control through modulation of engine thrust to crash land the aircraft and save a majority of the passengers. 4 In 2003, a DHL cargo plane climbing out of Baghdad was hit by a missile, causing loss of all hydraulics and wing damage. The pilots were able to successfully return to the airport and land using only the throttles to control the aircraft. In the aftermath of the Sioux City accident, NASA began investigating the use of throttles-only flight control. Several airframe configurations were studied, and it was found that the severity of the dutch roll and phugoid modes depends on multiple factors, but in general the engine response is too sluggish to be used to damp out the dutch roll, and the administration of thrust pulses to damp dutch roll may actually exacerbate it. 5 As the above examples demonstrate, use of the engines to modulate the aircraft’s dynamic behavior can improve the chance of survival in an emergency; however, the engine response may need to be improved to fully realize this benefit. In this paper we consider two specific emergency scenarios: vertical tail damage and runway incursion. Damage to the vertical tail can be detrimental in two ways. First, a reduction in the area of the vertical tail will reduce the directional stability of the aircraft. Second, if the rudder is disabled, the main control surface used for active yaw damping is lost. In the event of vertical tail damage, the dutch roll mode, which involves coupled yaw and roll oscillations, becomes much harder to control and in the worst case may be unstable. The dutch roll is often the least stable lateral-directional mode, and many planes rely on an automatic yaw damper to keep it manageable. One way to help recover directional stability is to use differential engine thrust to produce yawing moments. However, flight