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Vehicle design considerations for active control applications to subsonic transports are examined. Active control is defined along with those functions which are considered in the study of design criteria. The FAA regulations governing transport aircraft design are briefly discussed.
The flight service experience of 108 graphite-epoxy spoilers on 737 transport aircraft, and related ground-based environmental exposure of graphite-epoxy material specimens were evaluated. Four spoilers were installed on each of 27 aircraft for a 5-year study. As of February 28, 1975, a total of 294,280 spoiler flight-hours and 460,686 spoiler landings were accumulated. Based on visual, ultrasonic, and destructive testing, no moisture migration into the honeycomb core and no core corrosion has occurred. Tests of removed spoilers and of ground-based exposure specimens after the first year of service indicate no significant changes in composite strength.
The design, fabrication, static test, and fatigue test of both tension and compression graphite-epoxy candidates for a wing splice representative of a next-generation transport aircraft was the objective of the reported research program. A single-scarf bolted joint was selected as the design concept. Test specimens were designed and fabricated to represent an upper-surface and a lower-surface panel containing the splice. The load spectrum was a flight-by-flight random-load history including ground-air-ground loads. The results of the fatigue testing indicate that, for this type of joint, the inherent fatigue resistance of the laminate is reflected in the joint behavior and, consequently, the rate of damage accumulation is very slow under realistic fatigue loadings.
Piloted six-degrees-of-freedom motion simulator investigations were conducted at the NASA Ames Research Center to determine criteria relating the hazard posed by a wake vortex encounter to the response of the encountering airplane. These investigations demonstrated that wake vortex encounters can be realistically reproduced on a simulator, established that the maximum bank angle due to the encounter provides the best correlation with the pilot's subjective assessment of the hazard, and determined hazard boundaries in terms of maximum bank angle for two classes of jet transport aircraft.
Results are presented for an airframe noise experiment intended to obtain airframe noise data of a 0.03-scale model of a large transport aircraft in a flow facility for comparison with similar airframe noise data from full-scale flyover tests of the same aircraft. The test model simulated the landing and cruise configuration, including individual flap systems. Considerable noise is found to be associated with the extension of the model's leading edge flap system and to be reduced across the noise spectra when the gaps between the leading-edge flaps and the leading edge of the wing are sealed. Amplitude and frequency scaling relationships are developed which correlate respective data for a variety of aircraft configurations. Normalized model landing gear noise failed to simulate full-scale data.
Recent transport aircraft system studies have shown that the Prop-Fan propulsion system offers the potential for significant fuel savings over high bypass turbofans employing the same core engine technology for each. This important finding has encouraged more detailed study of the Prop-Fan aerodynamics and has led to NASA sponsorship of a wind tunnel research program to explore the projected high efficiency levels of advanced propeller configurations for 0.80 Mach number, high-altitude cruise operation. The aerodynamic design philosophy for the Prop-Fan model is discussed. The geometric characteristics and predicted performance of the wind tunnel model are presented. Finally, the preliminary test results are reviewed and compared to the performance goals originally projected.
The paper describes techniques for testing and validating software for the TCV (Terminal Configured Vehicle) program which is intended to solve problems associated with operating a commercial transport aircraft in the terminal area. The TCV research test bed is a Boeing 737 specially configured with digital computer systems to carry out automatic navigation, guidance, flight controls, and electronic displays research. The techniques developed for time and cost reduction include automatic documentation aids, an automatic software configuration, and an all software generation and validation system.
A preliminary assessment of the facilities and equipment which will be required at a representative airport is provided so liquid hydrogen LH2 can be used as fuel in long range transport aircraft in 1995-2000. A complete facility was conceptually designed, sized to meet the projected air traffic requirement. The facility includes the liquefaction plant, LH2, storage capability, and LH2 fuel handling system. The requirements for ground support and maintenance for the LH2 fueled aircraft were analyzed. An estimate was made of capital and operating costs which might be expected for the facility. Recommendations were made for design modifications to the reference aircraft, reflecting results of the analysis of airport fuel handling requirements, and for a program of additional technology development for air terminal related items.
Results from a number of studies concerned with the cost and benefits of applying advanced composite materials to commercial turbofan engines are summarized. For each application area the optimistic and pessimistic benefit projections were averaged to arrive at a projected yearly percentage fuel savings for a commercial fleet of advanced technology transport aircraft. Engine components included in the summary are the fan section which includes fan blades, fan frame/case, and the blade containment ring; the nacelle; and the high pressure turbine blades and vanes. The projected fuel savings resulting from the application of composites are 1.85 percent for the fan section, 1.75 percent for the nacelle, and 2.35 percent for the high pressure turbine.
Studies of transport aircraft designed for boom-free supersonic flight show the variable sweep oblique wing to be the most efficient configuration for flight at low supersonic speeds. Use of this concept leads to a configuration that is lighter, quieter, and more fuel efficient than symmetric aircraft designed for the same mission. Aerodynamic structural, weight, aeroelastic and flight control studies show the oblique wing concept to be technically feasible. Investigations are reported for wing planform and thickness, pivot design and weight estimation, engine cycle (bypass ratio), and climb, descent and reserve fuel. Results are incorporated into a final configuration. Performance, weight, and balance characteristics are evaluated. Flight control requirements are reviewed, and areas in which further research is needed are identified.
The raw-acoustic data corrected to standard day, from acoustic tests performed on a 0.508-scale fan vehicle of a 111,300 newton thrust, full-size engine, which has application on an advanced transport aircraft, are presented. The single-stage advanced technology fan was designed to a pressure ratio of 1.8 at a tip speed of 503 m/sec to achieve the desired pressure ratio in a single-stage fan with low radius ratio, and to maintain adequate stall margin. The two basic approaches taken in the acoustic design were: (1) minimization of noise at the source, and (2) suppression of the generated noise in the inlet and bypass exhaust duct. Suppression of the generated noise was accomplished in the inlet through use of the hybrid concept (wall acoustic treatment plus airflow acceleration suppression) and in the exhaust duct with extensive acoustic treatment including a splitter. The goal of the design was attainment of twenty effective perceived noise decibels. The suppression goal of FAR 36-20 was not reached, but improvements in the technology of both front and aft fan-noise suppression were realized.
Potential relationships between eye behavior and pilot workload are discussed. A Honeywell Mark IIA oculometer was used to obtain the eye data in a fixed base transport aircraft simulation facility. The data were analyzed to determine those parameters of eye behavior which were related to changes in level of task difficulty of the simulated manual approach and landing on instruments. A number of trends and relationships between eye variables and pilot ratings were found. A preliminary equation was written based on the results of a stepwise linear regression. High variability in time spent on various instruments was related to differences in scanning strategy among pilots. A more detailed analysis of individual runs by individual pilots was performed to investigate the source of this variability more closely. Results indicated a high degree of intra-pilot variability in instrument scanning. No consistent workload related trends were found. Pupil diameter which had demonstrated a strong relationship to task difficulty was extensively re-exmained.
A wind tunnel test was conducted to obtain power on low speed characteristics of a twin fan vectored thrust V/STOL transport aircraft. Longitudinal, as well as some lateral directional data, were analyzed. Hover, STOL, and conventional flight modes were investigated. Determination of STOL characteristics, hover characteristics, roll control effectiveness and aircraft attitude were evaluated. The study also included various means to improve the lifting capability of the aircraft such as by application of fuselage strakes, exhaust vanes capable of shifting the thrust vector aft, and external flap blowing for STOL performance.
Requirements for a strategic air cargo capability are considered. Practical national resource investment considerations dictate that future military strategic airlift planners regard civil capabilities as an integral part of the solution. Attention is given to the military needs for airlift, the civil-military airlift commonality, the present air cargo business, growth projections for civil air cargo, future air cargo business, the introduction date for a dedicated airfreighter, and the demands for transport aircraft.
The design of advanced composite aileron suitable for long-term service on transport aircraft includes Kevlar 49 fabric skins on honeycomb sandwich covers, hybrid graphite/Kevlar 49 ribs and spars, and graphite/epoxy fittings. Weight and cost savings of 28 and 20 percent, respectively, are predicted by comparison with the production metallic aileron. The structural integrity of the design has been substantiated by analysis and static tests of subcomponents. The producibility considerations played a key role in the selection of design concepts with potential for low-cost production. Simplicity in fabrication is a major factor in achieving low cost using advanced tooling and manufacturing methods such as net molding to size, draping, forming broadgoods, and cocuring components. A broadgoods dispensing machine capable of handling unidirectional and bidirectional prepreg materials in widths ranging from 12 to 42 inches is used for rapid layup of component kits and covers. Existing large autoclaves, platen presses, and shop facilities are fully exploited.
The flight service experience of 110 graphite epoxy spoilers on 737 transport aircraft was reviewed as well as ground based environmental exposure of graphite epoxy material specimens for the period from April 1976 through April 1977. Several spoilers were installed on each of 27 aircraft representing seven major airlines operating throughout the world. A flight service evaluation program of at least 5 years is under way. As of April 30, 1977, a total of 766,938 spoiler flight hours and 1,168,090 spoiler landings were accumulated by the fleet. Based on visual ultrasonic, and destructive testing, there was no evidence of moisture migration into the honeycomb core and no core corrosion. Tests of removed spoilers and of ground based exposure specimens after the third year of service continue to indicate modest changes in composite strength properties.
The flight-service experience of 110 graphite-epoxy spoilers on 737 transport aircraft and related ground-based environmental exposure of graphite-epoxy material specimens is reported. Spoilers were installed on each of 27 aircraft representing seven major airlines operating throughout the world. Based on visual, ultrasonic, and destructive testing, there is no evidence of moisture migration into the honeycomb core and no core corrosion. Tests of removed spoilers and of ground-based exposure specimens after the second year of service indicate modest changes in composite strength.
An experimental investigation was conducted to determine the vortex attenuating effect of engine thrust. Tests were made using a 0.03-scale model of the Boeing 747 transport aircraft as a vortex generating model. A Learjet-class probe model was used to measure the vortex induced rolling moment at a scale separation distance of 1.63 km. These tests were conducted at a lift coefficient of 1.4 at a model velocity of 30.48 m/s. The data presented indicate that engine thrust is effective as a vortex attenuating device when the engines are operated at high thrust levels and are positioned to direct the high energy engine wake into the core of the vortex. The greatest thrust vortex attenuation was obtained by operating the inboard engine thrust reversers at one-quarter thrust and the outboard engines at maximum forward thrust.