Short Take-off And Landing Aircraft Research Articles

Mass, primary energy, and cost: the impact of optimization objectives on the initial sizing of hybrid-electric general aviation aircraft

For short take-off and landing (STOL) aircraft, a parallel hybrid-electric propulsion system potentially offers superior performance compared to a conventional propulsion system, because the short-take-off power requirement is much higher than the cruise power requirement. This power-matching problem can be solved with a balanced hybrid propulsion system. However, there is a trade-off between wing loading, power loading, the level of hybridization, as well as range and take-off distance. An optimization method can vary design variables in such a way that a minimum of a particular objective is attained. In this paper, a comparison between the optimization results for minimum mass, minimum consumed primary energy, and minimum cost is conducted. A new initial sizing algorithm for general aviation aircraft with hybrid-electric propulsion systems is applied. This initial sizing methodology covers point performance, mission performance analysis, the weight estimation process, and cost estimation. The methodology is applied to the design of a STOL general aviation aircraft, intended for on-demand air mobility operations. The aircraft is sized to carry eight passengers over a distance of 500 km, while able to take off and land from short airstrips. Results indicate that parallel hybrid-electric propulsion systems must be considered for future STOL aircraft.

Hybrid Buoyant Aircraft: Future STOL Aircraft for Interconnectivity of the Malaysian Islands

Hybrid buoyant aircraft are new to the arena of air travel. They have the potential to boost the industry by leveraging new emerging lighter-than-air (LTA) and heavier-than-air (HTA) technologies. Hybrid buoyant aircraft are possible substitutes for jet and turbo-propeller aircraft currently utilized in aviation, and this manuscript is a country-specific (Malaysia) analysis to determine their potential market, assessing the tourism, business, agricultural, and airport transfer needs of such vehicles. A political, economic, social, and technological factors (PEST) analysis was also conducted to determine the impact of PEST parameters on the development of buoyant aircraft and to assess all existing problems of short takeoff and landing (STOL) aircraft. Hybrid buoyant aircraft will not only result in reduction of transportation costs, but will also improve the economic conditions of the region. New airworthiness regulations can lead to greater levels of competition in the development of hybrid buoyant aircraft.

Modeling and Approximation of STOL Aircraft Longitudinal Aerodynamic Characteristics

Flight dynamics deals principally with the natural response of the aircraft to longitudinal perturbations that typically consist of two underdamped oscillatory modes having rather different time scales. One of the modes has a relatively short period and is usually quite heavily damped. This is called the short period mode. The other mode has a much longer period and is rather lightly damped. This is called the phugoid mode. The required degree of dynamic stability is specified by the time it takes the motion to damp to half of its initial amplitude. The dynamic characteristics of an airplane is important in assessing its handling or flying qualities and for designing autopilots. This paper investigates the dynamic characteristics of short take off and landing (STOL) airplanes employing root locus technique and state space approach. The nonlinear differential equation of motion of an airplane developed from Newton’s second law of motion was linearized using the small disturbance theory. Different phugoid approximations for longitudinal modes were developed and compared with the exact solution formulated using statistical software. Further research work about active control technology to improve aerodynamic efficiency which results in potential fuel savings should be carried out.

Application of nonlinear inverse methods to the control of powered-lift aircraft over the low-speed flight envelope

This paper presents a summary of experience in the design of velocity vector control systems for operation of short take-off and landing (STOL) and short take-off and vertical landing (STOVL) aircraft over their low-speed flight envelopes. A nonlinear inverse control method developed at NASA Ames Research Center was employed to deal with the highly nonlinear, multi-dimensional aerodynamic and propulsion system characteristics that are inherent in these aircraft. The method partitions the control system into a command element that is defined solely by the dynamic response to achieve good flying qualities, and a nonlinear inverse element that computes the aerodynamic and propulsion control effector positions required to satisfy the pilot's commands and to regulate against disturbances. Experience gained at flight evaluations with a powered-lift STOL aircraft and in piloted simulation with a STOVL aircraft design indicates that this system design approach produces the desired flying qualities over the low-sp...

Fuel conservative guidance for shipboard landing of powered-lift STOL aircraft

A computer-simulation study was undertaken to investigate the application of Fuel Conservative Guidance (FCG) techniques, developed at NASA Ames Research Center, to improve the fuel efficiency and minimize recovery time of powered-lift short-takeoff-and-landing (STOL) airplanes operating from aircraft carriers at sea. The FCG system consists of a set of algorithms whose coefficients and parameters limits match those of the Quiet Short-Haul Research Aircraft. When a flightpath is specified by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the FCG synthesizes the necessary guidance commands to capture the specified path at any specified waypoint and to optimize fuel consumption and time fo fly along the path. Closed-form expressions are developed for calculating the altitude profile synthesized by the algorithm. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 38 percent (434 lb of fuel) and the time required to fly the flightpath was reduced by as much as 28 percent (209 sec). Savings because of FCG were produced by: (1) shortening the total flight time and distance, and (2) keeping the airspeed high as long as possible to minimize time spent flying in a powered-lift mode.

On the sonic fatigue life estimation of skin structures at room and elevated temperatures

Fighter/trainer empennages and STOL (Short Take-Off and Landing) aircraft flap systems are subjected to severe acoustic pressure levels as high as 150–170 dB. As a result, acoustic fatigue has become one of the major factors in design. Empennages and flap systems are also subject to high temperatures and thus the influence of thermal buckling on fatigue life must be taken into consideration. To estimate the sonic fatigue life of skin structures, combined use is made of the Monte Carlo method of non-linear panel response analysis and local stress-strain simulations with rheological models. Calculations were conducted and comparison of the results with experimental data shows that the method estimates the sonic fatigue life accurately when adequate values of fatigue notch factors are chosen. Example calculations with thermal as well as static pressure effects were also carried out and the effect of thermal buckling on sonic fatigue life is clarified.

STOL Aircraft Flight and Landing Area Considerations

Current research to achieve a technically and socially acceptable short take-off and landing (STOL) aircraft system to help alleviate present air transportation congestion is outlined considering both flight and runway elements. The aerodynamic jet-flap propulsive-lift concept is briefly reviewed with proposed turbofan powered-lift aircraft. Short, single direction, and possibly elevated runways are considered for use in high-land-cost urban areas. Aircraft capability is being developed to enable operations under high crosswind conditions, possibly through the use of crosswind landing gears or crosswind-reducing fences erected along the sides of the runway. Techniques are being developed to insure smooth wind flow over elevated STOL ports, such as on the roofs of buildings; and emergency arresting systems are under study to contain the aircraft on the runway. Heating and grooving of the runway has been explored analytically as a method of keeping the required runway length short by guaranteeing runway friction even under ice and snow conditions.

Operational Constraints for STOL Aircraft

The Short Takeoff and Landing (STOL) transportation system has been proposed as a solution to short-haul transportation congestion, because it 1) operates independently of the existing Conventional Takeoff and Landing (CTOL) system; 2) offers more convenience to short haul travelers; and 3) relieves congestion at major airports. However, the STOL transportation system encounters operational constraints which differ from current CTOL aircraft. These constraints are: economics, short-haul market characteristics, operating environment, and community acceptance. This paper discusses how these constraints influence the STOL aircraft's size, speed, propulsion system, takeoff/landing performance, and maneuverability.

STOL Aircraft for the Late 1970's

There is little argument the nation's transportation systems resemble a labyrinthian jungle. The problem is overwhelming. It involves systems developed independently of each other and are seemingly unable to accommodate new technology without major upheavals in cost and service. Supplanting old systems with new ones appears to be equally difficult, involving long lead times and conflicts between and national factions. One of the greatest transportation needs is for an effective short-distance (up to 500 miles) travel service. Although the transportation system has proven an ideal mode for longdistance travel, it has been costly, cumbersome and ineffective in meeting the daily needs of the millions of short-distant travelers. For this, says the Civil Aeronautics Board, after a two-year study of the present situation in the populated Northeast corridor, a properly implemented Short Take-Off and Landing (STOL) system is needed. Ten billion short-haul passenger miles were flown in the nation during 1970 alone. We estimate, says Dr. George Low, Acting Administrator for the National Aeronautics and Space Administration, that the market for short-haul transportation will approach 40 billion passenger miles by 1980 and may well be between 100 billion and 300 billion passenger miles by 1995. In addition, increasing demands large airports be built away from heavily populated areas necessitate an efficient city-to-airport service. Pressures from the public to do something about door-to-door travel time are another factor. The market seems wide open. In light of this, one might ask why private industry has not capitalized on the need. The reasons are legion. They include both operating problems such as traffic control systems and the aircraft development In recent Congressional testimony, Roy P. Jackson, Associate Administrator for Advanced Research and Technology at NASA, explained the lack of STOL progress as the result of a of inaction. Providing the aircraft itselfone can take off and land in a small area, quietly, economically, and in all kinds of weather-is one element. The nature of the service, however, requires many small, convenient airports. Aircraft manufacturers are reluctant to assume the risk of developing the special type of transport needed for short-haul use without carrier orders and some assurance of Government certifications, says Jackson. And air carriers are reluctant to place orders for aircraft without some assurance of routes, suitable airports and a suitable traffic control system. And finally, local communities are reluctant to provide new airports or allow the use of existing ones because of the anticipated noise and pollution or because the advantages of the service are not apparent, he concludes. This particular cycle is relatively new. The increasingly divergent paths of military and civilian aircraft needs in recent years have left the aviation industry with much of the research and development work used to be a spin-off from military aircraft development. It is this void has led some Congressmen to urge NASA expand its aeronautical research into more direct applications. Thus NASA iS proposing in its 1972 budget requests $15 million for initial steps in a joint Government-industry program for research and development of a STOL system (SN: 11/28/70, p. 413). The system development is a joint NASA-Department of Transportation venture with NASA assuming the responsibility for the aircraft development. The DOT'S over-all responsibility is to organize an system can accommodate such a craft. According to Congressional testimony, much of the necessary wind tunnel testing, quiet engine, pollution and noise abatement research has already been done at NASA research centers as a natural function of the agency's charter. The new program, however, proposes to go one step further: NASA will go to industry with the requirements for the vehicle and award the contracts for building of two research craft. When NASA announces the opportunity for contract competition, says one NASA official, there will be open the opportunity for cost-sharing by the contract industry itself. If the aerospace industry is not willing to assume some of the cost, NASA will pay for it

Subjective Evaluation of General Aviation and STOL Aircraft

Experiments were conducted in a progressive wavefield, in which a group of subjects evaluated the noisiness of more than 70 general aviation, short take-off and landing (STOL), and conventional commercial aircraft sound recordings. A paired-comparison technique was employed and the experimental procedure was automated as far as possible to minimize errors. All signals were subjected to “real time” 13-oct analysis in order to calculate a number of time-integrated rating scales. Comparisons calculated and judged noisiness values are presented and the effects of tonal content, during, and other factors are discussed. [Work supported by the Federal Aviation Administration under contract.]

Takeoff performance of jet-propelled conventional and vectored-thrust STOL aircraft.

An analytical method for the determination of the air distance of jet-propelled conventional (CTOL) and vectored-thrust short takeoff and landing (STOL) aircraft has been developed. The method assumes constant lift and drag coefficients during the climb and a constant value of the horizontal acceleration based on the aircraft's average velocity from touchoff to the 35- or 50-ft obstacle. It is indicated by this method that some classical or specification methods for computing CTOL air distances are not generally applicable. Design charts are developed for determining the ground, air, and total takeoff distance in terms of: an STOL thrust-to-weight ratio, (Tx/W)/( - TV/W) an effective wing loading (W/S)(l/aCLo)', and the L/D ratio. A parametric study of approximately 100 hypothetical CTOL and STOL aircraft was made, and graphs of the takeoff performance presented. It is shown that thrustto-weight ratios greater than approximately 0.6 are required in order to show performance gains by thrust vectoring, that the major improvement in takeoff distance derives from the reduction in ground roll while air distance is relatively unaffected, and that reduced wing loadings or improved high-lift capabilities are equally as beneficial.

STOL Aircraft—A Perspective

SummaryThe interest in Canada in the design and manufacture of utility aircraft with a short take-off and landing (STOL) performance may be traced back to the difficulties of surface transport in the early development of the country and the widespread use of bush aircraft.The leading characteristics of the STOL aircraft are examined with particular reference to design features essential to a short take-off and landing. The choice of powerplants and lifting systems is discussed with emphasis on the requirements for powered lift in the larger sizes of aircraft. The augmentor-wing is described as an example of an integrated propulsion lifting system with promise of a high performance.The phases of the take-off, transition, climb and landing manoeuvre are reviewed to illustrate the relative importance of various parameters in design and operation. The importance is stressed of good stability characteristics and effective controls for manoeuvring in a confined air space and a consistent landing performance.The requirements of a para-military mobile force tor a rapid response, deployment overseas and transportation in an area are examined. Some estimates are given of the probability of finding suitable airstrips in a particular region and the cost of constructing new airfields in a dynamic situation. The operating environment in potentially troubled areas of the world is examined briefly to provide guidance in design. The costs of a military supply system are discussed using various modes of transport which include trucks, helicopters, STOL and conventional transport aircraft with results which suggest that the system employing STOL aircraft in the tactical theatre has advantages in cost and effectiveness.Attention is drawn to the growing requirement for shorthaul, commuter and air taxi aircraft with STOL characteristics. Reference is made to the increases in air travel and the widespread use of large transport aircraft which have encouraged the movement of airports from urban centres at a time when city growth and congestion render surface transport increasingly difficult. The relative costs of commercial systems using the helicopter and STOL aircraft are examined. It is shown that the cost of STOL ports is not an excessive portion of total system costs when all factors are taken into account. Some forecasts are made as to future development trends in transport systems using STOL aircraft.