Aircraft Size Research Articles

Raman lidar measurements of aerosol extinction and backscattering: 2. Derivation of aerosol real refractive index, single‐scattering albedo, and humidification factor using Raman lidar and aircraft size distribution measurements

Aerosol backscattering and extinction profiles measured by the NASA Goddard Space Flight Center Scanning Raman Lidar (SRL) during the remote cloud sensing (RCS) intensive operations period (IOP) at the Department of Energy Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) site during two nights in April 1994 are discussed. These profiles are shown to be consistent with the simultaneous aerosol size distribution measurements made by a PCASP (Passive Cavity Aerosol Spectrometer Probe) optical particle counter flown on the University of North Dakota Citation aircraft. We describe a technique which uses both lidar and PCASP measurements to derive the dependence of particle size on relative humidity, the aerosol real refractive index n, and estimate the effective single‐scattering albedo ω0. Values of n ranged between 1.4–1.5 (dry) and 1.37–1.47 (wet); ω0 varied between 0.7 and 1.0. The single‐scattering albedo derived from this technique is sensitive to the manner in which absorbing particles are represented in the aerosol mixture; representing the absorbing particles as an internal mixture rather than the external mixture assumed here results in generally higher values of ω0. The lidar measurements indicate that the change in particle size with relative humidity as measured by the PCASP can be represented in the form discussed by Hanel [1976] with the exponent γ = 0.3 ± 0.05. The variations in aerosol optical and physical characteristics captured in the lidar and aircraft size distribution measurements are discussed in the context of the meteorological conditions observed during the experiment.

Numerical Simulations of Commercial Aircraft Wakes Subjected to Airport Surface Weather Conditions

Using tower e yby data for validation, we have developed a two-dimensional numerical simulation of the ine uence of surface weather conditions on wake vortex motion and decay for representative commercial aircraft. Our simulations support the conjecture that the ratio of eddy viscosity to kinematic viscosity, appropriate for modeling aircraft wakes, scales linearly with circulation, which yields a nominally constant equivalent Reynolds number for all commercial aircraft sizes. We have tested the constant eddy viscosity approximation for three different aircraft types and six surface weather states, showing the utility of the approach in predicting wake vortex motion and decay. Subsequently, we have shown how data from one aircraft e ight test can be used to infer the decay behavior of another, and we have examined the ine uence of the six surface weather states on the vortex decay behavior predicted for a large commercial aircraft. Based upon these simulations, we have determined that the two-dimensional, constant eddy viscosity approach can be useful in assessing the ine uence of surface weather conditions on wake vortex decay.

Expert system for scheduling in an airline gate allocation

Scheduling is an important technique encompassing a wide application area. Because of the complex interrelations among the resources, knowledge, and various other constraints, scheduling has many difficulties. Artificial Intelligence technology has been applied to solve the scheduling problem. As AI techniques are efficient in representing knowledge and dealing with heuristics, it is an adequate approach to model and to solve scheduling problems. We have implemented the ramp scheduling system, called RACES (Ramp Activity Coordination Expert System), to solve complex and dynamic aircraft parking problems. RACES was developed from the domain knowledge and experience which were acquired from the domain experts. Domain knowledge and experience are important factors in controlling the scheduling procedure. RACES divides the problem into sub-problems and experimental heuristics in the knowledge acquisition process. The system independently processes scheduling for the divided sub-problems and shares variables and domains. During the scheduling, the system selects or confines the search space with domain filtering techniques by exploiting the characteristics of various constraints and knowledge. RACES produces a user-driven near-optimal solution by means of a trade-off scheduling method using heuristics between the size of aircraft and the best-fit time. For 400 daily flights, RACES made parking schedules for aircraft in about 20 s compared with 4–5 h by human experts.

Airline competition on the route between Amsterdam and London

Although liberalization in European air transport business was formally completed with the implementation of the third package of the EU, today the free market effects of abandoning the bilateral system are not yet very manifest. The experiences in the United States indicate that it can last for over a decade before more or less stable competitive positions are set according to liberalized market conditions. The Amsterdam-London route was among the first routes which was liberalized on a bilateral basis. The development of airline competition on this route gives a rather good insight in what might be expected on other European routes the following years. In the ATRG paper, emphasis is laid upon the following competition characteristics: the number of airlines serving the London routes; the frequency offered by these airlines; the average aircraft size; the air fares charged. Special attention is paid to the relative attractiveness of the various airports in the Londen Area. Also the entrance of start-up carriers that offer no frills, no thrills services is covered.

Estimating runway capacities of German airports

This paper deals with two problem areas: How to make forecasts of demand for air transport services compatible with those for airport capacity, when estimating capacity surpluses or deficits; and second, an empirical method for estimating functions of runway capacities for German airports. The first part of the paper describes the demand and capacity characteristics of the German air transport system and methodological questions of estimating capacity reserves are also discussed, regarding the definition of capacity, the selection of the time unit of volume and capacity for comparison purposes, and the estimation of comparable volume and capacity values. The second part deals with empirically derived functions of take‐off, landing and mixed mode runway capacity. It has been found that the hourly movement rate is mainly determined by the sequence pattern and the size and mix of aircraft in the landing and take‐off process.

Reply by the Authors to D. H. Chester

T HE cases of damage caused by nose-first landings that have recently been reported in Ref. 1 are a clear indication that this subject deserves serious attention and that it is not merely a theoretical exercise. However, while being of interest to the landing-gear designer, the Engineering Note lacks an explanation of why the value of /* should be taken as equal to 0.8/2 or less (and as a consequence, why the vertical energy ratio of 1.25 or more is to be used at the nose gear). The reason may be found in Ref. 2. In the example for nose-gear landing-impact given there, the polar moment of inertia in pitch about the e.g. used a radius of gyration kcg of 44.7% of the spacing between the gears /, compared to the value of A:cg of 28.7% that is actually used in the Engineering Note. Reference 2 also showed that the equivalent at the nose gear was 2.20 times the mass there, and that this ratio is roughly proportional to the relative size of the moment of inertia in pitch. Then, by taking proportions for the example in the Engineering Note. Equivalent 2.20 x (0.287/0.447) 1.40 of the static mass. With the design sinking speed ]/sink this will directly affect the vertical energy that is absorbed by the nose gear. It is close to the value of 1.50 times the normal sinking energy that is suggested in the Engineering Note. In general, these values for equivalent at the nose gear exceed the ones that are specified in FAR 25.725 Airworthiness Regulations. A more exact method of analysis is provided in Ref. 2, however, it should be further noted that the effect of fuselage flexibility will reduce this ratio, particularly on the larger sizes of aircraft.

Comment on 'Aircraft landing gear positioning concerning abnormal landing cases'

HE cases of damage caused by nose-first landings that have recently been reported in Ref. 1 are a clear indication that this subject deserves serious attention and that it is not merely a theoretical exercise. However, while being of interest to the landing-gear designer, the Engineering Note lacks an explanation of why the value of /* should be taken as equal to 0.8/2 or less (and as a consequence, why the vertical energy ratio of 1.25 or more is to be used at the nose gear). The reason may be found in Ref. 2. In the example for nose-gear landing-impact given there, the polar moment of inertia in pitch about the e.g. used a radius of gyration kcg of 44.7% of the spacing between the gears /, compared to the value of A: cg of 28.7% that is actually used in the Engineering Note. Reference 2 also showed that the equivalent at the nose gear was 2.20 times the mass there, and that this ratio is roughly proportional to the relative size of the moment of inertia in pitch. Then, by taking proportions for the example in the Engineering Note. Equivalent - 2.20 x (0.287/0.447) - 1.40 of the static mass. With the design sinking speed ]/sink this will directly affect the vertical energy that is absorbed by the nose gear. It is close to the value of 1.50 times the normal sinking energy that is suggested in the Engineering Note. In general, these values for equivalent at the nose gear exceed the ones that are specified in FAR 25.725 Airworthiness Regulations. A more exact method of analysis is provided in Ref. 2, however, it should be further noted that the effect of fuselage flexibility will reduce this ratio, particularly on the larger sizes of aircraft.

Quality-of-Service Model of Intercity Air-Travel Demand

An econometric model is estimated for intercity passenger demand using postderegulation data. The model incorporates some quality-of-service measures as explanatory variables. These include flight frequency during peak and off-peak periods, aircraft size (i.e., number of seats), and travel time. The results suggest that demand is elastic with respect to airfare, and is highly dependent on flight schedule and travel time. It seems that frequency and route planning will continue to be challenges for the airlines, and that the solutions are very much market specific. They will depend on, among other things, the predominant trip purpose (business or nonbusiness), and the capacity constraints that affect the utilization of specific airports.

Future of Airline Hubbed Networks: Some Policy Implications

By hubbing at a few airports, airlines can maintain high levels of aircraft utilization and take advantage of the economies of aircraft size. Passengers also benefit in the form of increased frequency of service. However, increased aircraft operations at major hubs imply certain diseconomies that include congestion delay, increased workload on air-traffic controllers, noise, and pollution. Using a network equilibrium model, this study attempts to project the future structure of domestic networks and to discuss some policy implications. The results suggest that network hubbing will continue to persist as an important feature of air transportation, but in a multihub system. Unless expanded substantially, major hubs will suffer from escalated levels of delays and will become mostly traffic-generator airports instead of connecting and transfer points. Some implications to the concept of wayports, hub pricing, and the role of aircraft technology in relieving delays at major hubs are also discussed.

RCS of resonant scatterers with attached wires

The effects of wire antennas carried on aircraft for HF communication on the radar cross section (RCS) at HF frequencies are studied by comparing the RCSs of a strip, a cylinder, and a rod with and without an attached wire. The RCS is found for broadside incidence and for end-on incidence of the plane wave for scatterer lengths from 0.4 to 3.8 wavelengths, typical of aircraft size at HF frequencies. It is shown that the RCS of such fuselage-like targets with a wire antenna is quite different from that of the targets without the wire. For broadside incidence, the wire contributes a sharp peak-and-trough to the RCS are the wire's fundamental resonant frequency. For end-on incidence the wire considerably enhances the RCS at frequencies making its length odd multiples of the quarter-wave. >

The Projected Market Share for a New Small Airport in the North of England∗

THOMPSON A. and CAVES R. (1993) The projected market share for a new small airport in the North of England, Reg. Studies 27, 137–147. Sheffield is hoping to have a short take-off and landing airport open for business by 1993. Its use will depend on its ability to recapture local traffic which currently uses other existing airports. A behavioural choice model has been calibrated on the actual airport choice made in 1983 by travellers who started their trips within an hour of Sheffield's airport site. This model has been used to predict Sheffield's market share for a range of frequencies and fares. It is shown that comparable frequencies need to be offered to those at the competitive airports if the new airport is to recapture the majority of the traffic generated in its own hinterland. Fare and aircraft size are much less important, at least for business traffic. THOMPSON A. et CAVES R. (1993) La part de marche prevue d'un nouvel aeroport local dans le Nord d'Angleterre, Reg. Studies 27, 137–147. Sheffield...

Proposed modifications to ice accretion/icing scaling theory

The difficulty of conducting full-scale icing tests has long been appreciated. Testing in an icing wind tunnel has been undertaken for decades. While aircraft size and speeds have increased, tunnel facilities have not, thus making subscale geometric tests a necessity. Scaling laws governing these tests are almost exclusively based on analysis performed over 30 years ago and have not been rigorously validated. The following work reviews past scaling analyses and suggests revision to these analyses based on recent experimental observation. It is also suggested, based on the analysis contained herein, that current ice accretion predictive technologies, such as LEWICE when utilized in the glaze ice accretion regime, may need upgrading to more accurately estimate the rate of ice build-up on aerodynamic surfaces.

Divisibility, Technology, and the Competitive Potential of Regional Airlines

During the 12 years following deregulation of,the airline industry, tremendous change has taken place involving both industry structure and industry competition. Much of the discussion concerning these changes has not fully considered the factor supply side of the industry, especially with respect to emerging technology and factor indivisibility. However, new technology airframe and engine design (turboprop and turbofan) and the use of new materials promises to mitigate the problems associated with aircraft size. The availability of this new technology will enable regional air carriers to implement new competitive strategies such as regional hubbing and hub bypassing. This paper discusses the impact of technology on the competitive potential of regional airlines, looking at the benefits of and impediments to such competition.

Efficient sizing of a cargo rotorcraft

A new cargo rotorcraft sized to meet the most demanding of the future combat airlift requirements being postulated by the U. S. Army could be unnecessarily large and expensive. Overall requirements could be satisfied more efficiently with a smaller aircraft by using multilift for infrequent peak demands. This paper describes a methodology for assessing the benefit of multilift and the influence of usage spectrum on required aircraft size and achievable overall productivity. For characteristic distributions of mission payload, radius of action, and ambients, it is shown that aircraft design gross weight could be reduced as much as 40% and overall productivity improved as much as 50% by using multilift for less than 5% of the missions.

Multiattribute Aircraft Choice for Airline Network

Multiattribute decision-making methods were used to solve the problem of choosing aircraft size and the corresponding network composition. Prior to ranking, a model was developed to calculate flight frequencies offered to passengers according to available capacities at the highest possible level of service. Flight frequencies thus obtained were used as input data for the calculation of parameters on which the ranking was based. Aircraft of different capacities were ranked based on the following criteria: investments in fleet, average operating costs per passenger carried, percentage of airline services with one flight daily, average schedule delay per passenger, and the number of aircraft in the fleet. The considered alternatives were ranked using the permutational method taking into account only the order of importance of the previously mentioned criteria.

Shaping the technology of aircraft propulsion

The following papers describe developments which are projected in the various areas of the aero-engine scene. I do not wish to pre-empt or overlap these papers but instead propose to attempt to paint a general strategic picture.Both commercial and military aviation have been transformed by the emergence of the jet engine in the early 1940s. On the civil side, aircraft have become larger, more economical, faster, more comfortable, more reliable and safer. On the military side, the jet engine has made supersonic operation possible and has enabled aircraft size to be reduced even with enhanced mission capability. Also, the small turboshaft engine has enabled the helicopter to be developed to be an integral part of any defence system.Until the mid-1960s, the civil engines were determined by a need to progressively improve SFC, reduce noise, increase reliability and, at the same time, increase thrust (Fig. 1). We saw only minor changes in cycle and configuration up to the low bypass ratios of JT3D, JT8, Conway and Spey. In more recent times, the large fan engines, JT9, CF6 and RB 211, led to a step-change in both SFC and noise level and the subsequent 10-15 years has yielded progressive refinements of these engines.

Respiratory symptoms of flight attendants during high-altitude flight: possible relation to cabin ozone exposure.

The smaller size and lighter weight of the Boeing 747SP aircraft, introduced into passenger service in 1976, permitted higher-altitude flight than older commercial aircraft and thus potentially greater ozone exposure for those of board. Concerned flight attendants distributed questionnaires relating to symptoms experienced on the Boeing 747SP and/or conventional 747 aircraft to Los Angeles- and New York-based flight attendants. Respondents reported symptoms by frequency and severity and by in-flight and after-flight occurrence. Based on the assessment of three health scientists as to ozone-relatedness, the frequency of "definite" and "probable" ozone-related symptoms of any severity reported by both groups of attendants was significantly associated with 747SP flights (chi-squares: P less than 0.05). After-flight symptoms significantly associated with 747SP experience, although fewer in number than in-flight symptoms, were all in the scientists' "definite" category. In 21 flight attendants who complained of moderate to severe symptoms during 747SP flights, a battery of pulmonary function tests performed approximately two weeks after their last 747SP flight failed to reveal abnormalities. The symptom questionnaire results are consistent with possible exposure of cabin attendants to toxic levels of ozone during the higher-altitude flights of the Boeing 747SP compared to conventional 747 aircraft.

Baggage Claim Area Congestion at Airports: An Empirical Model of Mechanized Claim Device Performance

Although baggage handling is a major airport expense and congestion of luggage claim areas is quite common, knowledge of how baggage claim devices perform their task under congested conditions is virtually nonexistent. In order to bridge this gap this paper describes a model that, for different demand conditions, can predict the performance of a claim device depending on its characteristics. The demand conditions considered include aircraft size, lag between arrival of passengers and bags, and the fraction of passengers that transfer. The characteristics of the claim device that affect performance are frontage length, cycle time, and maximum throughput. The proposed model can predict the accumulation of passengers around the claim device, the time it takes to handle a planeload, and the average passenger service time as the demand conditions and claim device characteristics change. Although the model is deterministic and makes a number of simplifying assumptions, it is also easy to apply if the arrival pattern of bags and people to the claim area is known. Thus, if predictive and/or normative models for these arrivals become available, fairly simple and realistic procedures to study a number of baggage claim area design and operation issues could be developed around the model. The model, which is based on data gathered at the American Airline, National Airline, and Western Airline terminals at San Francisco International Airport, was able to reproduce the observed light congestion phenomena quite well; especially in the case that consisted of a rather large planeload. Unfortunately, lack of resources prevented us to observe a variety of terminals, including situations with much congestion and many bags per passenger. Because of this, further refinements and/or fine tuning of the formulas is definitely recommended.

A Working Environment for Aircraft Maintenance

The past fifty years have produced a remarkable growth and improvement in aircraft size and performance which in turn has resulted in benefits to users, operators and aircrew. However, on the debit side, the servicing and maintenance of these aircraft has produced a proportionate deterioration in the working environment of engineers engaged in this activity.

The influence of aircraft size on airline operating costs

Many previous studies have shown that there are probably no economies of scale in the airline industry directly attributable to firm size. Scale effects within the firm, however, have often been suggested, particularly for example with regard to such firm-size independent factors as market density, route length, or aircraft size. The focus of this paper is the effect of aircraft size on an airline's unit cost. Though much of the previous evidence appears to be at variance with a priori expectations, the empirical results presented here suggest that most of the divergence is probably due to a conceptually inadequate basis of comparison. Appropriately compared, actual unit costs were generally found to decrease at a decreasing rate with aircraft size, though as the route length parameter is reduced some mild diseconomies appeared. Of further interest, the behavior with size of the underlying cost components was found to be quite diverse, the (far from uniform) decreases with size in unit crew, fuel, and maintenance costs being offset somewhat by increases in unit capital costs, insurance plus other costs, and landing fees.