Thrust Reverser Research Articles

Late Paleozoic Deformation of Interior North America: The Greater Ancestral Rocky Mountains

Late Paleozoic deformation within interior North America has produced a series of north-northwest- to northwest-trending elongate basins that cover much of Oklahoma, Texas, New Mexico, Colorado, and Utah. Each basin thickens asymmetrically toward an adjacent region of coeval basement uplift from which it is separated by synsedimentary faults with great vertical relief. The remarkable coincidence in timing, geometry, and apparent structural style throughout the region of late Paleozoic deformation strongly suggests that these paired regions of basin subsidence and basement uplift form a unified system of regional deformation, the greater Ancestral Rocky Mountains. Over this region, basin subsidence and basement uplift were approximately synchronous, beginning in the Chesterian-Morrowan, continuing through the Pennsylvanian, and ending in the Wolfcampian (although minor post-Wolfcampian deformation occurs locally). The basement uplifts show evidence for folding and faulting in the Pennsylvanian and Early Permian. Reverse faults and thrust faults have been drilled over many of the uplifts, but only in the Anadarko region has thrusting of the basement uplifts over the adjacent basin been clearly documented. Extensive basement-involved thrusting also occurs along the margins of the Delaware and Midland basins, and suggests that the entire greater Ancestral Rocky Mountains region probably formed as the result of northeast-southwest-directed-intraplate shortening. Deformation within the greater Ancestral Rocky Mountains was coeval with late Paleozoic subduction along much of the North American plate margin, and has traditionally been related to emplacement of thrust sheets within the Ouachita-Marathon orogenic belt. The nature, timing, and orientation of events along the Ouachita-Marathon belt make it difficult to drive the deformation of the greater Ancestral Rocky Mountains by emplacement of the Ouachita-Marathon belt along the southern margin of North America. We speculate the deformation was driven instead by events within a late Paleozoic Andean margin along the southwestern margin of North America. Evidence for the existence of this previously unrecognized Andean margin comes from east-central Mexico, where a Pennsylvanian and Permian volcanic arc indicates that a northeast-dipping subduction boundary lay to the south and west. The interpretation that deformation throughout the greater Ancestral Rocky Mountains occurs by basement-involved overthrusting on gently to moderately dipping thrust faults suggests that potential hydrocarbon reserves beneath crystalline thrust sheets may be much greater than is generally supposed.

Inlet acoustic mode measurements using a continuously rotating rake

Comprehensive measurements of the spinning acoustic mode structure in the inlet of the advanced ducted propeller were obtained using a unique method that was first proposed by Sofrin. A continuously rotating microphone system was employed. Three inlet configurations with cut-on as well as cut-off stator vane sets were tested. The cut-off stator was designed to suppress all modes at the blade passing frequency. Rotating rake measurements indicate that several extraneous circumferential modes, possibly due to the interaction between the rotor and small interruptions in the casing tip treatment, were present. The cut-on stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cut-off stator. HE next generation of fan engines will likely employ a marriage of turbofan and propeller technologies to achieve significant noise and fuel consumption reductions. The ad- vanced ducted propeller (ADP) model used in this investi- gation was designed and built by Pratt and Whitney, a Di- vision of United Technologies, and tested in the NASA Lewis 9- by 15-ft Anechoic Wind Tunnel. Typical of propeller tech- nology, the ADP allows for the in-flight adjustment of the blade pitch angle. This provides reverse thrust and optimum performance over a wide range of conditions. The duct pro- vides the noise suppression advantage of a conventional fan engine. Since future engines are expected to use still higher bypass ratios, fan noise is likely to be the dominant engine source. One of the most important features of fan tone noise is its modal structure. Knowledge of these spinning modes helps to identify the generation mechanism, control duct propa- gation (thus, mode knowledge is needed for acoustic treat- ment design) and control far-field radiation. Previous at- tempts at direct mode measurements1'3 have faced formidable practical difficulties such as: very large axial and circumfer- ential arrays of wall microphones that are not practical for the short ducts of ultrahigh bypass engines, and radial mea- surements upstream of the fan that introduce a wake that interacts with the rotor, thus causing extraneous modes. A continuously rotating microphone technique first proposed by Sofrin4 overcomes the problem of wake-generate d modes, reduces the number of microphones and the duct length re- quired. This technique has been implemented for the first time in this investigation. Two important features of this tech- nique are as follows:

Geophysical evidence of mud diapirism on the Mediterranean Ridge accretionary complex

Mud volcanoes, mud cones, and mud ridges have been identified on the inner portion of the crestal area, and possibly on the inner escarpment, of the Mediterranean Ridge accretionary complex. Four areas containing one or more mud diapirs have been investigated through bathymetric profiling, single channel seismic reflection profiling, heat flow measurements, and coring. A sequence of events is identified in the evolution of the mud diapirs: initially the expulsion on the seafloor of gasrich mud produces a seafloor depression outlined in the seismic record by downward dip of the host sediment reflectors towards the mud conduit; subsequent eruptions of fluid mud may create a flat topped mud volcano with step-like profile; finally, the intrusion of viscous mud produces a mud cone. The origin of the diapirs is deep within the Mediterranean Ridge. Although a minimum depth of about 400 m below the seafloor has been computed from the hydrostatic balance between the diapiric sediments and the host sediments, a maximum depth, suggested by geometric considerations, ranges between 5.3 and 7 km. The presence of thermogenic gas in the diapiric sediments suggests a better constrained origin depth of at least 2.2 km. The heat flow measured within the Olimpi mud diapir field and along a transect orthogonal to the diapiric field is low, ranging between 16 ± 5 and 41 ± 6 mW m−2. Due to the presence of gas, the thermal conductivity of the diapiric sediments is lower than that of the host hemipelagic oozes (0.6–0.9 and 1.0–1.15 W m−1 K−1 respectively). We consider the distribution of mud diapirs to be controlled by the presence of tectonic features such as reverse faults or thrusts (inner escarpment) that develop where the thickness of the Late Miocene evaporites appears to be minimum. An upward migration through time of the position of the decollement within the stratigraphic column from the Upper Oligocene (diapiric sediments) to the Upper Miocene (present position) is identified.

Vought aircraft enhances thrust reverser database with CFD simulations

Costly physical experiments are normally used to evaluate the performance of thrust reverser concepts during the design process. This is because the design geometry is normally so complex that producing a computational fluid dynamics (CFD) model would take longer than running an experiment. Recently, unstructured grid CFD software packages have come onto the market that claim to greatly reduce the amount of time required to produce a grid. One of these packages. RAMPANT from Fluent, Inc., Lebanon, New Hampshire, was used to model an experimental thrust reverser design. A series of varying cascade blades were modelled in less than a day and the analysis results matched well with the experimental data.

Design Considerations of a Versatile Simulator for High-Bypass Turbofans

The continuing requirement for performance improvement of higher thrust turbofans is met by increased bypass ratios. The trend toward higher bypass ratios and relatively large-diameter low-pressure-ratio fans requires innovative design approaches, which include shorter inlets, slimmer nacelles, shorter fan ducts and exhaust systems, and possible elimination of thrust reverser. The success of this new generation of high-bypass ducted turbofans depends on understanding the acoustic impact from reduced treatment areas, inlet-fan coupling and operability, as well as overall system performance. To achieve these goals a versatile scale model propulsion simulator large enough to operate as a fan rig, yet small enough to be installed in a wind tunnel for evaluating overall acoustic, operability, and system performance, was developed. The criteria of designing such a simulator and its capabilities are discussed in this paper.

M. J. Hartmann Memorial Session Paper: NASA/GE Fan and Compressor Research Accomplishments

Fan and compressor research projects carried out at GE Aircraft Engines under NASA sponsorship are described in this paper. Four 1400-fps-tip-speed rotors designed with different airfoil shapes were found to have comparable stall lines but different efficiency trends. A stator placed behind one of these affected its performance somewhat. Adjustments of variable camber inlet guide vanes placed ahead of a 1500fps stage were found to affect its pumping capability without much affecting its stall line. For the Quiet Engine Program (QEP), two 1160-fps fans and one 1550-fps fan were tested. Development of the high-speed fan revealed the effects on performance of airfoil shape and part-span shroud blockage. The 950-fps variable-pitch fan for the Quiet Clean Short-haul Experimental Engine (QCSEE) demonstrated reverse thrust capabilities and a novel method of avoiding large core inlet pressure losses during reverse thrust operation. The 1350-fps Energy Efficient Engine (E3) fan demonstrated excellent performance with a novel quarter-stage arrangement that eliminated the need for interspool bleed while giving good dirt removal potential. The E3 compressor program employed Low Speed Research Compressor tests to identify the most appropriate blading type. High-speed rig tests and engine tests were then used to develop this 23:1-spool-pressure-ratio compressor. Research on casing boundary layer control through bleeding and blowing led to the discovery that irregular casing geometries usually give stall line enhancements even without auxiliary air circuits. Some of the resulting casing treatment research is reported herein. Instances in which NASA-sponsored research has affected GE Aircraft Engine products are pointed out.

Intratracheal Pulmonary Ventilation (ITPV)

A new mode of pulmonary ventilation called intratracheal pulmonary ventilation (ITPV) was studied. Briefly, a continuous flow of air/oxygen is introduced through a small catheter, the tip of which is positioned at the carina, with a diffuser mounted at its distal end. A timed expiration valve, when closed, provides for inspiration; when open, it provides for expiration. The system as first described had a potential for significant back pressure at the level of the carina, which was more at rapid gas flows and with smaller endotracheal tubes. We have now mounted a venturi on the tip of the catheter (reverse thrust catheter [RTC]) that avoids back pressure, and which facilitates expiration. At respiratory rates from 10 to 120/min, the ITPV system with the RTC maintained end-expiratory pressure at the level of the carina at, or near 0 cm H2O. Compared to conventional mechanical ventilation, at identical respiratory rates, this system reduced tidal volume by one half at the lowest respiratory rates, and by as much as two thirds at the highest respiratory rates, with a proportional decrease in peak inspiratory pressure. ITPV has the smallest minute volume ventilation of any conventional or nonconventional mode of pulmonary ventilation.

Intratracheal Pulmonary Ventilation and Congenital Diaphragmatic Hernia

Previous studies from our institution have shown that neonates with congenital diaphragmatic hernia (CDH), whose best postductal PaO2 (BPDPO2) was less than 100 mm Hg while on maximal conventional mechanical ventilation (CMV), had a mortality exceeding 90%. When combined with extracorporeal membrane oxygenation (ECMO), the mortality rose to 100% in those infants who developed hypercarbia following decannulation. Historically, those patients have required increasing ventilator support, leading to iatrogenic lung damage, and eventual death. Intratracheal pulmonary ventilation (ITPV) using the reverse thrust catheter (RTC) developed by Kolobow incorporates a continuous flow of humidified gas through a reverse Venturi catheter positioned at the distal end of the endotracheal tube. In animal studies, ITPV was shown to result in a reduced physiological dead-space (VD), to facilitate expiration, and to enhance CO2 elimination. In our current study, we have applied ITPV in two neonates with CDH who could not be weaned from ECMO because of uncontrollable hypercapnia, and who met above criteria for 100% mortality. In both cases, ITPV restored normal PaCO2 at low peak inspiratory pressure (PIP) with a substantial decrease in VD. We believe ITPV is suited to ventilating newborns with CDH in whom barotrauma is known to be common. Beyond its present use, ITPV may be useful to ventilate children with other forms of respiratory failure, and should be so considered along with other now available methods of mechanical pulmonary ventilation.

Intratracheal pulmonary ventilation and congenital diaphragmatic hernia: A report of two cases

Previous studies from our institution have shown that neonates with congenital diaphragmatic hernia (CDH), whose best postductal PaO 2 (BPDPO 2) was less than 100 mm Hg while on maximal conventional mechanical ventilation (CMV), had a mortality exceeding 90%. When combined with extracorporeal membrane oxygenation (ECMO), the mortality rose to 100% in those infants who developed hypercarbia following decannulation. Historically, those patients have required increasing ventilator support, leading to iatrogenic lung damage, and eventual death. Intratracheal pulmonary ventilation (ITPV) using the reverse thrust catheter (RTC) developed by Kolobow incorporates a continuous flow of humidified gas through a reverse Venturi catheter positioned at the distal end of the endotracheal tube. In animal studies, ITPV was shown to result in a reduced physiological dead-space (V D), to facilitate expiration, and to enhance CO 2 elimination. In our current study, we have applied ITPV in two neonates with CDH who could not be weaned from ECMO because of uncontrollable hypercapnia, and who met above criteria for 100% mortality. In both cases, ITPV restored normal PaCO 2 at low peak inspiratory pressure (PIP) with a substantial decrease in V D. We believe ITPV is suited to ventilating newborns with CDH in whom barotrauma is known to be common. Beyond its present use, ITPV may be useful to ventilate children with other forms of respiratory failure, and should be so considered along with other now available methods of mechanical pulmonary ventilation.

Constant reverse thrust activated reorientation of liquid hydrogen with Geyser initiation

A key objective of the cryogenic fluid management of the spacecraft propulsion system is to develop the technology necessary for acquisition or positioning of liquid outflow or vapor venting. Numerical simulation of positive liquid acquisition is attempted by introducing reverse gravity acceleration, resulting from the propulsive thrust of auxiliary engines, which exceeds critical value for the initiation of geyser. Based on the computer simulation of flowfields during the course of fluid reorientation, six dimensionless parameters resulted in this study. It shows that these parameters hold near-constant values through the entire ranges of liquid filled levels, from 30-80 percent, during the course of fluid reorientation.

The deformation behavior of ceramic crystals subjected to very low load (nano)indentations

The ultra-low load indentation response of ceramic single crystal surfaces (Al2O3, SiC, Si) has been studied with a software-controlled hardness tester (Nanoindenter) operating in the load range 2–60 mN. In all cases, scanning and transmission electron microscopy have been used to characterize the deformation structures associated with these very small-scale hardness impressions. Emphasis has been placed on correlating the deformation behavior observed for particular indentations with irregularities in recorded load-displacement curves. For carefully annealed sapphire, a threshold load (for a given indenter) was observed below which the only surface response was elastic flexure and beyond which dislocation loop nucleation occurred at, or near, the theoretical shear strength to create the indentation. This onset of plasticity was seen as a sudden displacement discontinuity in the load-displacement response. At higher loads, indentations appeared to be accommodated predominantly by dislocation activity, though microcracks were observed to form ät contact loads of only tens of milliNewtons. Possibly such cracks are the incipient slip-induced nuclei for the much larger, indentation-induced cracks usually apparent only on the surface at much higher loads and often used for estimating indentation toughness. By contrast, silicon did not show this behavior but exhibited unusually large amounts of depth recovery within indentations, resulting in a characteristic reverse thrust on the indenter during unloading. TEM studies of indentations in silicon revealed less evidence of obvious dislocation activity than in sapphire (particularly at the lowest loads used) but did show residual highly imperfect–and often amorphous–structures within the indentations, consistent with a densification transformation occurring at the very high hydrostatic stresses produced under the indenter. The reverse thrust is caused by the relaxation of densified material during unloading. Thus, it appears that the low-load hardness response of silicon is controlled by a pressure-sensitive phase transformation. Though SiC has been predicted to undergo a densification transformation similar to silicon, its load-displacement behavior was found to be similar to Al2O3suggesting that, for these contact experiments at least, the critical resolved shear stress for dislocation nucleation is exceeded before the critical hydrostatic pressure for densification is reached. In all cases, residual, plastically formed indentations were measured to be smaller than the fully loaded indentation depths would suggest, confirming that a significant portion of the deformation is elastic surface flexure. However, there is some doubt as to whether silicon displays elastic-only deformation even at very small penetration depths. The use of microstructural studies to complement nanoindentation experiments is shown to be a key route not only to interpreting the recorded load-displacement responses, but also to examining the deformation mechanisms controlling the mechanical behavior of ceramics to surface contacts at these small spatial scales.

Space-based cryogenic liquid hydrogen reorientation activated by low frequency impulsive reverse thruster of geyser initiation

The requirement to settle or to position liquid fluid over the outlet end of spacecraft propellant tank prior to main engine restart poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet without any vapor entrainment, any excessive geysering, or any other undesirable fluid motion for the space fluid management under microgravity environment. The purpose of the present study is to investigate most efficient technique for propellant resettling through the minimization of propellant usage and weight penalties. Comparison between the constant reverse gravity acceleration and impulsive reverse gravity acceleration to be used for the activation of propellant resettlement, shows that impulsive reverse gravity thrust is superior to constant reverse gravity thrust for liquid reorientation in a reduced gravity environment.

Computation of vectoring nozzle performance

As an initial step toward greater application of computational fluid dynamics to airframe/exhaust nozzle integration efforts, Euler codes were applied to numerically evaluate the internal performance of three advanced thrust vectoring nozzles developed for aircraft control. Nozzle geometry parameters included: pitch and yaw vector angles, sidewall length, sidewall deflection, and thrust reverser position. Computed pressure distributions and nozzle thrust and vectoring performance were compared to experimental data; agreement was excellent for vectoring configurations, and marginal for a reversing configuration.

Psychoacoustic benefits of aircraft noise barriers.

Annoyance is the most common reaction to aircraft noise. Over the years, residents of the communities adjacent to the Sarasota–Bradenton Airport have registered a substantial number of noise complaints. The nature of complaints suggests that community annoyance arises from three distinct sources: aircraft flying directly overhead, aircraft building up to full power immediately before and during their takeoff roll, and the thrust reversal associated with aircraft arrivals. In response to these complaints, a study was undertaken to determine the feasibility of constructing noise barriers to mitigate the impact of airport operations on the neighboring communities. The empirical decibel reductions predicted in the study may not justify the cost of constructing the recommended barriers [V. R. Desai, Wyle Res. Rep. WR 91-12, 24–25 (June 1991)]. The psychoacoustic benefits, however, may far outweigh the purely analytical conclusion. The construction of noise barriers may influence the community’s subjective response, by affecting their attitude toward the parties producing the noise. Community perception of reduced annoyance is as valuable to the Airport as any measurable reduction in noise level.

Safety Topics

ON completion of an 88 minute transit flight, a Boeing 747–436 was landed at night at Bangkok where the temperature was 29°C. The approach was made at a weight of 254 tonnes with the commander handling, a Vref of 150kt, medium autobrake selection (level three) and a tail wind component of 5kt. After touchdown at 156 kt CAS, the first officer selected partial reverse thrust on all engines but had slight problems engaging reverse thrust on the outboard pair. The thrust reversers on the inboard engines deployed 11 seconds after touchdown; those on the outboard engines deployed 1.7 seconds later. Reverse thrust was modulated during the landing rollout and maintained for a total of 33 seconds. In appreciation of the modest additional stopping distance required by the delayed onset of reverse thrust the commander decided to override the autobrakes and brake manually, leaving the runway at 16kt groundspeed at the last exit point before the runway end. While taxying‐in the crew were alerted by the EICAS to an abnormally hot brake on the number 8 wheel (left body gear, rear inboard wheel). The brake temperature had reached level five on a scale of zero to nine.

Airport noise monitoring for Boston area airports

Airport noise has been monitored at Logan International Airport since 1975. Recently, Massport decided to install a new noise monitoring system. The new system will monitor trends in noise impact by time of day, season, and on an annual basis; measure noise levels generated by aircraft taxiing, ground operations, reverse thrust, takeoffs, landings, and overflights; obtain accurate data on aircraft flight tracks and fleet mix to be used in the generation of noise contours; and assess the performance of the Logan Preferential Runway Advisory System in terms of runway utilization and noise exposure. To do this, noise data from some sites will be obtained in 1/3-octave bands as well as in the traditional A-weighting; C-weighting is available; radar tracking information is expected to be part of the system; and weather data will be obtained at about half of the sites. All data are saved in database for study of the correlation of noise with various factors. A complaint database, contour prediction mode (FAA integrated noise model), and mapping software are also part of the system. It is expected that this system will be used to evaluate different noise descriptors against actual complaints, and to suggest improvements to noise prediction models based on geography or meteorological effects.

Numerical investigation of airfoil/jet/fuselage-undersurface flowfields in ground effect

THE Euler/Reynolds-averaged compressible NavierStokes, continuity, and energy equations are solved in conjunction with a two-equation (K-e) turbulence model for two-dimensional flows related to vertical/shor t takeoff and landing (V/STOL) aircraft. Beam and Warming's implicit factored central-difference scheme with/without diagonalization is introduced. For the airfoil/jet/ground-interaction flowfields, the in viscid and laminar flows are considered. Different values of parameters (such as width, velocity, and temperature of jet; height of jet above the ground plane; and freestream Reynolds number) are employed to study the physical phenomena and aerodynamic coefficients. Also presented is information about the turbulent impinging jet with curved fuselageunder surf ace, pressure distributions on the ground plane and fuselage-under surf ace, and distributions of turbulent kinetic energy and velocity component along the center line. Contents The aerodynamic interaction caused by the flow around the airfoil, fuselage-under surf ace, and ground in the presence of lift jets is important in V/STOL aircraft design. Based on the solution of three-dimensi onal thin-layer Navier-Stokes equations, the velocity vectors and suck-down effect of laminar flow around a delta planform wing, equipped with two thrust reverser jets, in ground effect have been studied by Chawla et al.1 To describe the vortex formulation behind the jet and to include the effect of jet/ground interaction on the flowfield around the airfoil, Agarwal and Deese2 modified Jameson's Euler code (FLO-53) for computing almost incompressible flow. Agarwal and Bower3 studied the flow behaviors of the turbulent jet impingement flowfields with curved fuselage-undersurface. The governing equations, including a two-equation model, were expressed in stream function/vorticity forms and formulated by the finite-difference method. In this paper, Beam and Warming's scheme with/without diagonal form4'5 is introduced to solve the Euler/Reynolds-averaged compressible full Navier-Stokes, continuity, and energy equations in conjunction with a two-equation (K-e) turbulence model.6 The air foil/jet/fuselage-under surf ace flowfields in ground effect are investigated. For the air foil/jet/ground-inter action flowfields, the methods of characteristi c, average process, slip/no-slip, and adiabatic-wall conditions are respectively applied to the far-field boundary, trailing edge, wake cut, surface of airfoil, and ground plane. Velocity and temperature about the entering jet

Investigation of very high bypass ratio engines for subsonic transports

A study of propulsion system performance for a family of high bypass ratio turbofan engines is presented. The bypass ratio range is from 6 to 17.5, and both bare engine performance and nacelle installation performance have been considered. Geared, variable pitch/variable nozzle engines with bypass ratios of 10.6, 14, and 17.5 have been studied parametrically, and the performance of a fixed pitch, gearless engine of bypass ratio 9.6 has been estimated to represent an advanced engine with conventional mechanical complexity. Nacelle performance data for a bypass 5 engine have also been included as a baseline. Thrust reverser design for these engines is also considered. Results of this study indicate that conventional nacelle installation losses do not reverse the trend of improving engine fuel efficiency with bypass ratio out to at least bypass ratio 17.5. If innovative concepts are used, such as reverse thrust from a reverse fan pitch and a short fan cowl, the installed fuel efficiency for highbypass-ratio engines looks even better. The bypass 9.6 engine shows a lower fuel burn benefit than the bypass 17.5 engine, but it offers the potential of reduced mechanical complexity and lower maintenance cost.

Simulation of a delta wing with two jets in ground effect

Numerical simulations of the flow about a 60° delta planform wing, equipped with two thrust reverser jets, in ground effect are presented. These simulations are based on the solution of the three-dimensional thin-layer Navier-Stokes equations on a body-conforming, overset, multiple grid topology. An implicit, two-factor, numerical scheme with flux-splitting in the streamwise direction is used. The first set of simulations involves the validation of the numerical scheme by studying the impact of numerical parameters (e.g. grid refinement and dissipation levels) on the solution. The second set of simulations is performed to understand the effect of flow-field parameters (such as the height of the delta wing above the ground plane, the jet size, and the jet exit temperature) on the solution. Flow features such as jet deformation and ground vortex formation observed in experimental flow visualizations are captured. Comparisons with experimental data confirm the ability to simulate the loss of wing-borne lift, commonly referred to as “suck-down,” as the delta planform flies at slow speeds in close proximity to the ground. Detailed analysis of the numerical results has given insight into the structure of the ground vortex and the mechanisms of lift loss.

Bidirectional tapered roller thrust bearing for gas turbine engines

The paper discusses a single row, bidirectional tapered roller thrust bearing, which was developed to take advantage of increased life potential and to obtain improved performance by eliminating the thrust balance mechanism in advanced gas turbine engines. This bearing will take the full range of forward thrust without thrust balance and, in addition, will take thrust in the reverse direction caused by compressor surge. The higher load capacity of a tapered roller bearing offers improved reliability over a ball bearing. To verify this concept, a tapered roller bearing was designed, manufactured, and tested at speeds up to 24,000 rpm (2.64 million DN), at loads up to 66.7 kN (15,000 Ibf) in the major thrust direction, and for reverse thrust up to 8.9 kN (2000 Ibf) at 20,000 rpm. Bearing reliability was tested up to 10 times the calculated L10 fatigue. The bearing performed successfully in all phases of testing and proved the concept of reverse thrust load on a high-speed tapered roller bearing. The feasibility of a tapered roller bearing on a gas turbine engine mainshaft was demonstrated both for high speed as well as heavy load.