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NASA NTRS1961

Applications of Power Spectral Analysis Methods to Maneuver Loads Obtained on Jet Fighter Airplanes During Service Operations

Power spectral densities of normal load factor have been obtained for two service operational training flights of a Republic F-84G airplane and three service operational training flights of a North American F-86A airplane in order to indicate the load-factor frequency content and possible uses of power spectral methods in analyzing maneuver load data. It was determined that the maneuvering load-factor time histories appeared to be described by a truncated normal distribution. The power spectral densities obtained were relatively level at frequencies below 0.03 cycle per second and varied inversely with approximately the cube of the frequency at the higher frequencies. In general, the frequency content was very low above 0.2 cycle per second. The load-factor peak distributions were estimated fairly well from the spectrum analysis. In addition, peak load data obtained during service operations of fighter-type airplanes with flight time totaling about 24,000 hours were examined and appeared to agree reasonably well with the type of equations obtained from spectrum peak-load distributions.

Mayer, John P.↗

NASA NTRS1981

Analytic study of orbiter landing profiles

A broad survey of possible orbiter landing configurations was made with specific goals of defining boundaries for the landing task. The results suggest that the center of the corridors between marginal and routine represents a more or less optimal preflare condition for regular operations. Various constraints used to define the boundaries are based largely on qualitative judgements from earlier flight experience with the X-15 and lifting body research aircraft. The results should serve as useful background for expanding and validating landing simulation programs. The analytic approach offers a particular advantage in identifying trends due to the systematic variation of factors such as vehicle weight, load factor, approach speed, and aim point. Limitations such as a constant load factor during the flare and using a fixed gear deployment time interval, can be removed by increasing the flexibility of the computer program. This analytic definition of landing profiles of the orbiter may suggest additional studies, includin more configurations or more comparisons of landing profiles within and beyond the corridor boundaries.

Walker, H. J.↗

NASA NTRS1921

Loads and calculations of army airplanes

By comparing airplanes of known strength that have resisted all the usual and even extreme air loads with those that under like conditions were found to be insufficiently strong, the researchers, aided by scientific investigations, developed standards which are satisfactory for the calculation of airplane structures. Given here are standards applicable to loads on wing trusses, load factors for use in stress analysis, load factors required in sand testing, loads on control surfaces, loads on wing ribs, loads on landing gear, and rigidity of materials.

Stelmachowski, Ing↗

NASA NTRS1981

Kinematic properties of the helicopter in coordinated turns

A study on the kinematic relationship of the variables of helicopter motion in steady, coordinated turns involving inherent sideslip is described. A set of exact kinematic equations which govern a steady coordinated helical turn about an Earth referenced vertical axis is developed. A precise definition for the load factor parameter that best characterizes a coordinated turn is proposed. Formulas are developed which relate the aircraft angular rates and pitch and roll attitudes to the turn parameters, angle of attack, and inherent sideslip. A steep, coordinated helical turn at extreme angles of attack with inherent sideslip is of primary interest. The bank angle of the aircraft can differ markedly from the tilt angle of the normal load factor. The normal load factor can also differ substantially from the accelerometer reading along the vertical body axis of the aircraft. Sideslip has a strong influence on the pitch attitude and roll rate of the helicopter. Pitch rate is independent of angle of attack in a coordinated turn and in the absence of sideslip, angular rates about the stability axes are independent of the aerodynamic characteristics of the aircraft.

Chen, R. T. N.↗

NASA NTRS1990

Random vibration analysis of space flight hardware using NASTRAN

During liftoff and ascent flight phases, the Space Transportation System (STS) and payloads are exposed to the random acoustic environment produced by engine exhaust plumes and aerodynamic disturbances. The analysis of payloads for randomly fluctuating loads is usually carried out using the Miles' relationship. This approximation technique computes an equivalent load factor as a function of the natural frequency of the structure, the power spectral density of the excitation, and the magnification factor at resonance. Due to the assumptions inherent in Miles' equation, random load factors are often over-estimated by this approach. In such cases, the estimates can be refined using alternate techniques such as time domain simulations or frequency domain spectral analysis. Described here is the use of NASTRAN to compute more realistic random load factors through spectral analysis. The procedure is illustrated using Spacelab Life Sciences (SLS-1) payloads and certain unique features of this problem are described. The solutions are compared with Miles' results in order to establish trends at over or under prediction.

Thampi, S. K.↗

NASA NTRS1995

Improved Selection Of Structural-Load Safety Factors

More rational approach offers potential for optimization of design. Improvement in deterministic method of selection of structural-load safety factors makes possible to design structures more nearly optimum with respect to competing demands for both reliability and attributes detracting from reliability (principally lighter weight, smaller size, and lower cost).

Verderaime, Vincent↗

NASA NTRS1981

Influence of sideslip on the kinematics of the helicopter in steady coordinated turns

A steep coordinated helical turn at extreme angles of attack with inherent sideslip is of primary interest in this study. Unlike fixed-wing aircraft, the helicopter in a steady coordinated turn will inherently sideslip. A set of exact kinematic equations describing this motion in steady helical turns has been developed, and a rational definition for the load factor that best characterizes a coordinated turn for a helicopter has been proposed. An analysis has also been completed on the effects of sideslip on the kinematic relationships in a coordinated turn which is based on new closed-form solutions which relate the aircraft angular rates and pitch and roll attitudes to the turn parameters, angle of attack, and sideslip. The results show that the bank angle of the aircraft can differ markedly from the tilt angle of the normal load factor and that the normal load factor can also differ substantially from the accelerometer reading along the vertical body axis of the aircraft. Generally, sideslip has a strong influence on the pitch attitude and roll rate of the helicopter. The study also indicates that pitch rate is independent of angle of attack in a coordinated turn and that in the absence of sideslip, angular rates about the stability axes are independent of the aerodynamic characteristics of the aircraft.

Chen, R. T. N.↗

NASA NTRS1973

Analytical study of pressure balancing in gas film seals

The load factor is investigated for subsonic and choked flow conditions, laminar and turbulent flows, and various seal entrance conditions. Both parallel sealing surfaces and surfaces with small linear deformation were investigated. The load factor for subsonic flow depends strongly on pressure ratio; under choked flow conditions, however the load factor is found to depend more strongly on film thickness and flow entrance conditions rather than pressure ratio. The importance of generating hydrodynamic forces to keep the seal balanced under severe and multipoint operation is also discussed.

Zuk, J.↗

NASA NTRS1951

Horizontal tail loads in maneuvering flight

A method is given for determining the horizontal tail loads in maneuvering flight. The method is based upon the assignment of a load-factor variation with time and the determination of a minimum time to reach peak load factor. The tail load is separated into various components. Examination of these components indicated that one of the components was so small that it could be neglected for most conventional airplanes; therefore, the number of aerodynamic parameters needed in this computation of tail loads was reduced to a minimum. In order to illustrate the method, as well as to show the effect of the main variables, a number of examples are given. Some discussion is given regarding the determination of maximum tail loads, maximum pitching accelerations, and maximum pitching velocities obtainable.

Pearson, Henry A↗

NASA NTRS2000

Flying Lessons: Learning from Ryanair's Cost Reduction Culture

Through radically improving the value equation for airline customers, Ryanair has served to shake-up established norms and practices in European aviation. Underpinning its price leadership and market success is a vigorous and relentless cost reduction ethos and resultant low break-even load factor. Ryanair has lowered European airline cost structures considerably, shattering existing cost floors. Few competitors are able to follow, either because they do not know how or they are unable due to social settlement obligations or service commitments. At the same time, the company has maintained high average load factors on its flights. Taken in conjunction with its low break-even load factor, this results in consistently high overall profit margins. On this basis, Ryanair is likely to remain a significant competitor and increase its market presence and success across Europe.

Lawton, Thomas C.↗

NASA NTRS1990

Feasibility study for a microwave-powered ozone sniffer aircraft

The preliminary design of a high-altitude, remotely-piloted, atmospheric-sampling aircraft powered by microwave energy beamed from ground-based antenna was completed. The vehicle has a gross weight of 6720 pounds and is sized to carry a 1000 pound payload at an altitude of 100,000 feet. The underside of the wing serves as the surface of a rectenna designed to receive microwave energy at a power density of 700 watts per square meter and the wing has a planform area of 3634 square feet to absorb the required power at an optimum Mach number M = 0.44. The aircraft utilizes a horizontal tail and a canard for longitudinal control and to enhance the structural rigidity of the twin fuselage configuration. The wing structure is designed to withstand a gust-induced load factor n = 3 at cruise altitude but the low-wing loading of the aircraft makes it very sensitive to gusts at low altitudes, which may induce load factors in excess of 20. A structural load alleviation system is therefore proposed to limit actual loads to the designed structural limit. Losses will require transmitted power on the order of megawatts to be radiated to the aircraft from the ground station, presenting environmental problems. Since the transmitting antenna would have a diameter of several hundred feet, it would not be readily transportable, so we propose that a single antenna be constructed at a site from which the aircraft is flown. The aircraft would be towed aloft to an initial altitude at which the microwave power would be utilized. The aircraft would climb to cruise altitude in a spiral flight path and orbit the transmitter in a gentle turn.

Botros, David F.↗

DOE OSTI2020

Observational constraints on the multiphase nature of outflows using large spectroscopic surveys at z ∼ 0

ABSTRACT Mass outflow rates and loading factors are typically used to infer the quenching potential of galactic-scale outflows. However, these generally rely on observations of a single gas phase that can severely underestimate the total ejected gas mass. To address this, we use observations of high mass (≥1010 M⊙), normal star-forming galaxies at z ∼ 0 from the MaNGA, xCOLD GASS, xGASS, and ALFALFA surveys and a stacking of Na d, Hα, CO(1–0), and H i 21 cm tracers with the aim of placing constraints on an average, total mass outflow rate, and loading factor. We find detections of outflows in both neutral and ionized gas tracers, with no detections in stacks of molecular or atomic gas emission. Modelling of the outflow components reveals velocities of |vNa d| = 131 km s−1 and |vHα| = 439 km s−1 and outflow rates of $\dot{M}_{\rm {Na\,\small{D}}}$ = 7.55 M⊙ yr−1 and $\dot{M}_{\text{H}\alpha }$ = 0.10 M⊙ yr−1 for neutral and ionized gas, respectively. Assuming a molecular/atomic outflow velocity of 200 km s−1, we derive upper limits of $\dot{M}_{\text{CO}}\lt 19.43$ M⊙ yr−1 and $\dot{M}_{\rm {H\,\small {I}}}\lt $ 26.72 M⊙ yr−1 for the molecular and atomic gas, respectively. Combining the detections and upper limits, we find average total outflow rates of $\dot{M}_{\text{tot}}\lesssim$27 M⊙ yr−1 and a loading factor of ηtot ≲ 6.39, with molecular gas likely contributing ≲72 per cent of the total mass outflow rate, and neutral and ionized gas contributing ∼28 and <1 per cent, respectively. Our results suggest that, to first order, a degree of quenching via ejective feedback could occur in normal galaxies when considering all gas phases, even in the absence of an active galactic nucleus.

Roberts-Borsani, G. W.↗

NASA NTRS2001

Selected Contribution: Skeletal muscle focal adhesion kinase, paxillin, and serum response factor are loading dependent

This investigation examined the effect of mechanical loading state on focal adhesion kinase (FAK), paxillin, and serum response factor (SRF) in rat skeletal muscle. We found that FAK concentration and tyrosine phosphorylation, paxillin concentration, and SRF concentration are all lower in the lesser load-bearing fast-twitch plantaris and gastrocnemius muscles compared with the greater load-bearing slow-twitch soleus muscle. Of these three muscles, 7 days of mechanical unloading via tail suspension elicited a decrease in FAK tyrosine phosphorylation only in the soleus muscle and decreases in FAK and paxillin concentrations only in the plantaris and gastrocnemius muscles. Unloading decreased SRF concentration in all three muscles. Mechanical overloading (via bilateral gastrocnemius ablation) for 1 or 8 days increased FAK and paxillin concentrations in the soleus and plantaris muscles. Additionally, whereas FAK tyrosine phosphorylation and SRF concentration were increased by < or =1 day of overloading in the soleus muscle, these increases did not occur until somewhere between 1 and 8 days of overloading in the plantaris muscle. These data indicate that, in the skeletal muscles of rats, the focal adhesion complex proteins FAK and paxillin and the transcription factor SRF are generally modulated in association with the mechanical loading state of the muscle. However, the somewhat different patterns of adaptation of these proteins to altered loading in slow- vs. fast-twitch skeletal muscles indicate that the mechanisms and time course of adaptation may partly depend on the prior loading state of the muscle.

NASA Discipline Musculoskeletal↗

NASA NTRS1990

High altitude, microwave-powered atmospheric sampling aircraft

The preliminary design af a high altitude, remotely piloted, atmospheric sampling aircraft powered by microwave energy beamed from a ground based antenna has been completed. The aircraft utilizes a horizontal tail and a canard for longitudinal control and to enhance the structural rigidity of the twin fuselage configuration. The wing structure is designed to withstand a gust induced load factor of n equals 3 at cruise altitude, but the low wing loading of the aircraft makes it very sensitive to gusts at lower altitudes, where induced load factors may be in excess of 20. Therefore, a structural load alleviation system is proposed to limit actual loads to the designed structural limit. Since the transmitting antenna would have a diameter of several hundred feet, it would not be readily transportable; so, it is proposed that a single antenna be constructed at a site from which the aircraft is to be flown. The aircraft would be towed aloft to an initial altitude at which the microwave power would be utilized. The aircraft would climb to cruise altitude in a spiral flight path and then orbit the transmitter in a gentle turn.

Source record↗

NASA NTRS1975

RTLS entry load relief parameter optimization

The results are presented of a study of a candidate load relief control law for use during the pullup phase of Return-to-Launch-Site (RTLS) abort entries. The control law parameters and cycle time which optimized performance of the normal load factor limiting phase (load relief phase) of an RTLS entry are examined. A set of control law gains, a smoothing parameter, and a normal force coefficient curve fit are established which resulted in good load relief performance considering the possible aerodynamic coefficient uncertainties defined. Also, the examination of various guidance cycle times revealed improved load relief performance with decreasing cycle time. A .5 second cycle provided smooth and adequate load relief in the presence of all the aerodynamic uncertainties examined.

Crull, T. J.↗

NASA NTRS1946

Analysis of V-G Records from the SNB-1 Airplane

Availability data obtained on SNB-1 trainer-class airplanes were analyzed and results presented as flight envelopes which predict occurrences of large values of air speed and acceleration. Comparison is made with SNJ-4 trainer-class airplane data analyzed by the same method. It is concluded that flight envelopes are satisfactory; that the two types show large differences in flight loads and speeds experience; and that SNB-1 will seldom, if ever, exceed design limit load factor and restricted speed, which SNJ-4 can be expected to exceed design-limit load factor and restricted speed in a very small number of flight hours.

Meadows, May T.↗

NASA NTRS2003

Airport Pricing Strategies

Conventional economic wisdom suggests that congestion pricing would be an appropriate response to cope with the growing congestion levels currently experienced at many airports. Several characteristics of aviation markets, however, may make naive congestion prices equal to the value of marginal travel delays a non-optimal response. This paper has developed a model of airport pricing that captures a number of these features. The model in particular reflects that airlines typically have market power and are engaged in oligopolistic competition at different sub-markets; that part of external travel delays that aircraft impose are internal to an operator and hence should not be accounted for in congestion tolls. We presented an analytical treatment for a simple bi-nodal symmetric network, which through the use of 'hyper-networks' would be readily applicable to dynamic problems (in discrete time) such as peak - off-peak differences, and some numerical exercises for the same symmetric network, which was only designed to illustrate the possible comparative static impacts of tolling, in addition to marginal equilibrium conditions as could be derived for the general model specification. Some main conclusions are that second-best optimal tolls are typically lower than what would be suggested by congestion costs alone and may even be negative, and that the toll as derived by Brueckner (2002) may not lead to an increase in total welfare. While Brueckner (2002) has made clear that congestion tolls on airports may be smaller than expected when congestion costs among aircraft are internal for a firm, our analysis adds to this that a further downward adjustment may be in order due to market power. The presence of market power (which causes prices to exceed marginal costs) may cause the pure congestion toll to be suboptimal, because the resulting decrease in demand is too high (the pure congestion tall does not take into account the decrease in consumer surplus). The various downward adjustments in welfare maximizing tolls may well cause the optimal values of these to be negative. Insofar as subsidization is considered unacceptable for whichever reason, our results warn that the most efficient among the non-negative tolls may actually be a zero toll; the pure congestion toll may actually decrease welfare compared to the base case. The model in this paper contains a few simplifying assumptions that may be relaxed in future work. Load factors and aircraft capacity are fixed in this model for simplicity. In a more advanced version of this model, load factors and aircraft capacity can be endogenized. This makes the derivation of the optimality conditions far more complicated, but it should be feasible in a numerical experiment. One can also add a fourth layer to the model, describing the airport's optimization problem. For example, the airport can maximize profits under a cost recovery constraint. The model then deals with interactions between four types of agents. No distinction is made between peak and off-peak traffic in this paper. Finally, the results of the numerical exercise in this paper need to be checked against an asymmetric equilibrium.

Pels, Eric↗

NASA NTRS2011

Capability Extension to the Turbine Off-Design Computer Program AXOD With Applications to the Highly Loaded Fan-Drive Turbines

The axial flow turbine off-design computer program AXOD has been upgraded to include the outlet guide vane (OGV) into its acceptable turbine configurations. The mathematical bases and the techniques used for the code implementation are described and discussed in lengths in this paper. This extended capability is verified and validated with two cases of highly loaded fan-drive turbines, designed and tested in the V/STOL Program of NASA. The first case is a 4 1/2-stage turbine with an average stage loading factor of 4.66, designed by Pratt & Whitney Aircraft. The second case is a 3 1/2-stage turbine with an average loading factor of 4.0, designed in-house by the NASA Lewis Research Center (now the NASA Glenn Research Center). Both cases were experimentally tested in the turbine facility located at the Glenn Research Center. The processes conducted in these studies are described in detail in this paper, and the results in comparison with the experimental data are presented and discussed. The comparisons between the AXOD results and the experimental data are in excellent agreement.

Chen, Shu-cheng S.↗