Commuter Aircraft Research Articles

A methodology to determine pre-crash fuel quantity from post-crash fire thermal damage to an aircraft structure

The cause of engine failure that resulted in a catastrophic crash of a twin turbo-jet commuter aircraft is sought. The US National Transportation Safety Board and aircraft manufacturer contend that the engines failed because the aircraft ran out of jet fuel. The aircraft operators are confident that there was adequate fuel and that some other process caused fuel starvation. There was a post-crash fire that caused substantial thermal destruction of aircraft structure. If the majority of fire damage could be attributed to the burning of jet fuel, then it would be likely that the fuel inventory, just prior to impact with the ground, was adequate for continued flight. Thus investigators would have to conclude that some other mechanism caused the fuel starvation. In this work, a methodology is presented to determine the amount of fuel necessary to cause the observed thermal damage on the aircraft structure. The methodology is based on the determination of the heat flux and burning rates from the associated jet fuel pool fire and a heat transfer analysis to obtain the time required to melt structural parts subjected to the resulting heat fluxes. For an Aluminum alloy member, 70 mm thick, the time to reach the melting temperature of the alloy (∼500° C) is almost 4 min. Fully developed jet fuel pool fires burn at a rate of ∼0.06 kg/m2s, thus, for a pool fire of 10 m2, the fuel burned would be ∼130 kg, which is equivalent to about 151.4 L (40 US liquid gallons) of fuel. This fuel quantity would have been more than sufficient for the aircraft to reach its destination. Moreover, the actual quantity of fuel burnt would have been substantially more because of the conservative assumptions made in the analysis.

TOWARDS THE ELECTRIC PROPULSION

The paper presents benefits and drawbacks of the electric propulsion for the case of a ten seat commuter aircraft. An efficiency evaluation is made for an electric version of AEROTAXI, considered as a reference. The evaluation is projected to 2020, trying to meet the expected progresses in energy storage systems

A single heavy load airdrop and its effect on a reversible flight control system

PurposeThis paper aims to investigate the addition of airdrop capability to a commuter aircraft and its consequences on the reversible flight control system.Design/methodology/approachAirdrop was modeled to include its effect on aerodynamics and flight control system. A mathematical model was also developed for the reversible longitudinal flight control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi‐body dynamics code and validated using existing manufacturer's data which included recorded data from flight. The airdrop simulation results showed that the flight control system is affected in two steps. In the first step, the movement of the load required a forward force by the pilot. In this step, the elevator power was a key factor and had to be increased to allow the pilot to keep the aircraft in trim position during the airdrop. In the second step, a sudden forward shift of centre of gravity required an abrupt change in the direction of applied force. The maximum allowable force and control column movement had to be checked. In the case under study, they did not impose any difficulty.FindingsThe result showed that a special consideration had to be taken into account when an aircraft with reversible flight control system was to be used for airdrop mission.Originality/valueThis paper investigates the behaviour of a reversible flight control system during airdrop operation through analysis and simulation.

The influence of subjective response on the choice of measurement for aircraft arrival noise at Nantucket Airport

The Nantucket Airport in Massachusetts serves primarily turboprop commuter aircraft, and private or charter jets, with most of its operations in the summer. A seasonal homeowner was severely affected by arrival flight noise and requested noise measurements and noise control recommendations for this architect‐designed residence. Time was spent with the homeowner to understand steps already taken, and problems still causing trouble. Standard measurement procedures for aircraft operations in the United States call for the use of A‐weighted, slow response for the assessment of noise impact. Since the noise sources at this airport have strong tonal components (from the propellers), and noise control recommendations were sought, one‐second 1/3‐octave band levels were used to both document the observed problem, and to estimate the field transmission loss of the windows and doors. Measurements were made during a Friday afternoon, when arriving aircraft were mostly 1.5 to 2 min apart. A‐weighted maximum and single event levels (SELs) were also measured for each overflight, for comparison with published aircraft data. A “short circuit” was found due to an exposed vent pipe, which resulted in no transmission loss in the 100 Hz band. Appropriate recommendations were made.

Analysis of a reversible flight control system response to atmospheric turbulence

AbstractA mathematical model was developed for the reversible longitudinal control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi-body dynamics code and validated using existing manufacturer’s data as well as recorded data from several flights. Analysis of the flight data revealed light atmosphere turbulence level. To investigate the effect of higher turbulence intensity on the reversible flight control system, a sever turbulence level was generated using Von Karman model for the same flight level and velocity. The result was used as a random input to the dynamic model for computation of the frequency response of control column. It was shown that turbulence could act as a random input through the hinge moment during the flight and introduced a new mode in the lower end of power spectral density curve. The energy induced by this low frequency input resulted in large displacement of control column in simulation which surpassed the existing limits. Therefore it should be taken into account when dealing with handling quality as well as autopilot design.

Suboptimal adaptive control system for flight quality improvement

In this paper, the suboptimal algorithm of adaptive control system is presented, which is specially adjusted for automatic flight control systems of general aviation and commuter aircraft, and unmanned aircraft (UMA) that conduct flights in atmospheric turbulence. At first, the method could be applied for correcting these changes in flight dynamics parameters, which cannot be compensated with the aid of an open adaptation loop. At the same time, full identification of aircraft model in real time is not required. This method is based on the estimation of most typical parameters of the aircraft mathematical model, which are most closely related to parameters, which are unmeasurable during flight, like aircraft real mass and position of center of gravity. The structure of an adaptation algorithm of aircraft flight control laws is based on the expert knowledge in the field of flight dynamics and is the result of optimization calculations. The examples which show attaining better flight comfort of the PZL M20, “Mewa” general aviation aircraft and quality improvement of the UMA, “Vector” pitch angle automatic control, have been presented.

Aerodynamic Modeling and System Identification from Flight Data-Recent Applications at DLR

This paper provides an overview of a few selected system identification activities carried out during the last decade at DLR, the German Aerospace Center. After a brief account of parameter estimation methods and of consistency checking of recorded flight data, an emphasis is placed on: i) development of global, high-fidelity aerodynamic databases for training simulators, ii) models for in-flight simulator iii) modeling of stall hysteresis, iv) estimation of aerodynamic flow field characteristics and validation of aircraft reaction models from wake vortex encounter flights, and v) a parametric wake distortion model to improve helicopter coupling off-axis response. These examples cover a variety of flight vehicles with widely different characteristics, namely the military transport aircraft Transall C-160, commuter aircraft Dornier 328, in-flight simulator VFW-614 ATTAS, high altitude research aircraft G850 Strato 2C, Airbus type aircraft, fly-by-wire helicopter BO-105, and fly-by-light helicopter EC-135. Besides parameter estimation aspects, those related to model validation are discussed. Through succinct examples, it is brought out that system identification has become an indispensable tool to support not only research but also industry activities in various key areas such as model validation, handling qualities evaluation, control law design, and flight vehicle design and certification. Thus, it contributes significantly to risk and cost reduction.

Wind tunnel–flight correlation for laminar wings in adiabatic and heating flow conditions

The DoAL3 airfoil was designed for a laminar wing of a commuter aircraft with small leading edge sweep flying at moderate Mach numbers, M=0.45–0.6, and Reynolds numbers up to Re=14×10 6. Free transition measurements were executed in the Transonic Wind Tunnel Braunschweig (TWB) of the DLR, German Aerospace Center, at a Mach number of 0.48 and a Reynolds number of 3.2×10 6. To quantify the airfoil performance for flight Reynolds numbers a Navier–Stokes method coupled to e N transition prediction is applied. The limiting N factor for the TWB facility has been shown beforehand to achieve a value of six, in flight a mean value of twelve can be expected. The extrapolation to flight Reynolds numbers considers the aircraft flying in adiabatic and heating flow conditions. When exposed to extensive sunshine on the airfield the fuel contained in the wet wings will be heated and the aircraft is then flying a considerable time in climb and cruise with wings exposed to non negligible heat transfer. The effects of Reynolds number and heat transfer on the extent of laminar wing flow are investigated separately. The important findings of the numerical study are, firstly, that in adiabatic conditions the wing will fly with the same extent of the laminar bucket as observed in the wind tunnel. Secondly, in heating conditions laminarity is completely lost, the drag is almost doubled with respect to the minimum drag for adiabatic flows.

Aircraft configuration and flight profile optimization using simulated annealing

This paper discusses the application of simulated annealing in the conceptual design and optimization of twin-turboprop Commuter & Regional aircraft to obtain the optimum configuration and flight profile of such aircraft for operation over a given stage length. Generalized cost of travel incurred by a passenger for air travel between two cities is considered as the objective function to be minimized. Generalized cost is assumed to consist of four cost terms, viz., access cost, flight cost, time cost and airport cost. A computational methodology was developed for the estimation of these cost terms for short-haul air travel, as a function of 17 design variables and nine constraints. A simulated annealing optimization method was coupled to this methodology and a case study for short-haul business travel in India was carried out. A modified optimization strategy was adopted to reduce the overall computation time required. The results obtained in this case study are discussed in the paper.

Examination of Part 135 Controlled Flight into Terrain Accidents as a Basis for Enhanced Ground Proximity Warning Systems

In 1998 the Federal Aviation Administration (FAA) proposed the installation of Enhanced Ground Proximity Warning devices (EGPWS) in all turbine powered aircraft with six or more passenger seats, operating under Federal Aviation Regulation Part 135, to reduce “Controlled Flight Into Terrain” (CFIT). CFIT accident experience of Part 135 operations has not been evaluated by the FAA. We analyzed all commuter and charter aircraft crashes of this type using NTSB aviation accident data from 1983 to 1998. There were 15 crashes with CFIT criteria. We asked 15 experienced pilots to examine the narratives of the crashes and to estimate the probability that EGPWS would have allowed the crew to avoid these crashes. Based on the ratings, the median probability that Part 135 crashes would be avoided using EGPWS is 58%. Human factors issues associated with EGPWS are discussed.

Developments in active control of aircraft interior noise—Directions for tonal and broadband noise sources

Aircraft interior noise is a continuing problem for a wide range of aircraft types. Interior noise levels in general aviation aircraft make communication difficult, significantly impact pilot endurance, and are considered important to the reemergence of this class of aircraft. For passengers in propeller-powered commuter aircraft, conversation is difficult at best and becomes oppressive on the passengers for long periods. It is also regarded as one reason for the replacement of propeller commuter aircraft by the emerging regional jet. In business jets, the passengers are often interested in conducting meetings during flights. This calls for low SPL and SIL for which the aircraft incurs both space and weight penalties. Large commercial aircraft pay a significant weight penalty for current interior noise levels considered acceptable. With the drive for more weight-effective airframes, the challenge becomes even more difficult. This paper will show some current efforts to develop more efficient active control technologies for both tonal noise sources and broadband noise sources. These will include improvements in controller technologies, actuator implementation, optimization of transducer topology, improved coupling to the noise source, and integration of the active technology with conventional passive technology.

Developments in aircraft interior acoustics—Recent progress and directions

Aircraft interior noise is a continuing problem for a wide range of aircraft types. High interior noise levels in general aviation aircraft make any communication difficult, significantly impact pilot endurance, and are considered important to the reemergence of this class of aircraft. For passengers in propeller-powered commuter aircraft, conversation is difficult at best and becomes oppressive on the passengers for long periods. It is also regarded as one reason for the replacement of propeller commuter aircraft by the emerging regional jet. In business jets, the passengers are often interested in conducting meetings during flights. This calls for low SPL and SIL for which the aircraft incurs both space and weight penalties. Large commercial aircraft pay a significant weight penalty for current interior noise levels considered acceptable. With the drive for more weight-efficient airframes, the challenge becomes even more difficult. This paper will overview current efforts to develop both design and noise control techniques. These range from improvements in the quantification of the noise sources, to considerations in the overall structural design, and to the use of both active and passive control tools. In addition, the emerging use of predictive and measurement tools will be discussed and applications to aircraft highlighted.

RGPS - Based Automatic Landing System for Light and Commuter Aircraft

The report is devoted to the design problems of Navigation, Guidance and Flight Control of the Light and Commuter Aircraft in the landing mode using Local Area Augmentation Systems, based on the relative GPS. The integrated strapdown Inertial Navigation and Global Positioning System is used for the solution of guidance problems and robust flight control system is used for the Aircraft stabilization in landing mode. Problems of design of robust control autopilot with structured uncertainty of aircraft parameters are consider.

Do Firms' Product Lines Include Too Many Varieties?

A firm that offers an additional product can capture business from rival firms for other products when consumers prefer to concentrate their purchases at a single supplier. This may lead firms to offer excessive product variety from the social standpoint. A firm may even completely foreclose competing firms from the market by introducing a new product. Forbidding new product introductions (e.g., forbidding universal banking or forbidding a new airline route), forbidding mergers that broaden firms' product lines (e.g., as the EC forbade a merger of commuter aircraft manufacturers), and forbidding Sunday shopping may sometimes be appropriate public policies.

Meteorological Conditions Associated with the ATR72 Aircraft Accident near Roselawn, Indiana, on 31 October 1994

An ATR72 commuter aircraft crashed near Roselawn, Indiana, on 31 October 1994 killing all 68 people on board. Available weather data, including those from a Next Generation Radar, a radar wind profiler, a Geostationary Operational Environmental Satellite, and pilot reports of icing have been examined in combination with analysis fields from the Rapid Update Cycle model and forecast fields from the Pennsylvania State University/National Center for Atmospheric Research MM5 numerical model. Synthesis of this information provides a relatively complete and consistent picture of the ambient meteorological conditions in the region of the ATR72 holding pattern at ~3.1 km above mean sea level. Of particular interest is the evidence that these conditions favored the development of supercooled drizzle drops within a strong frontal zone, as indicated by cloud-top temperatures of −10° to −15°C, weak radar reflectivity, and strong, vertical wind shear within the cloud and warm front.

Do Firms' Product Lines Include Too Many Varieties?

A firm that offers an additional product can capture business from rival firms for other products when consumers prefer to concentrate their purchases at a single supplier. This may lead firms to offer excessive product variety from the social standpoint. A firm may even completely foreclose competing firms from the market by introducing a new product. Forbidding new product introductions (e.g., forbidding universal banking or forbidding a new airline route), forbidding mergers that broaden firms' product lines (as, e.g., the EC forbade a merger of commuter aircraft manufacturers), and forbidding Sunday shopping may sometimes be appropriate public policies.

Accuracy, Integrity, and Availability of GLS-Based Autopilot-Coupled Aircraft Landings

The project Integrity of Satellite Navigation (ISAN) investigates the potential of GNSS (GPS and/or GLONASS) as part of a hybrid GNSS Landing System (GLS) for precision approach and landing down to Category (CAT) III. Specifically, accuracy, integrity, continuity of function, and availability are considered. The accuracy and continuity of function of the GLS were demonstrated in more than 400 flight tests in a commuter aircraft, and landing trials with a Boeing 757 aircraft during the Boeing Autoland Program. These flight tests demonstrated that the navigation system provides sufficient accuracy to perform landings according to suggested FAA requirements of CAT I to III. The present objectives of ISAN are the analysis and improvement of the system availability and establishment of a method to approve system integrity standards. A combination of GPS/GLONASS is considered for the GLS availability improvement. For reasons of integrity monitoring, satellite anomalies, atmospheric effects, and multipath problems on the signal-in-space, as well as GPS receiver failures, are taken into account in a GLS Closed Loop Simulation Test Bed installation, including a GPS Simulator to validate the system integrity in defined test scenarios.

Aerospace and military

The paper describes how "smaller, faster, cheaper" were the watchwords in 1995 as aerospace and military program managers tried to cut the cost of doing business-without cutting the missions or goals of their programs. One of the most ambitious of these efforts took place at the US National Aeronautics and Space Administration, Washington, DC, which moved to slash its workforce and to develop new lines of spacecraft that would be smaller and more autonomous than the Galileo vehicle, which limped to Jupiter with the assistance of a legion of ground controllers. Civilian aircraft companies expected to sell more commuter aircraft than jumbo jets. And the military found that defending itself against battlefield missiles is still as difficult as it was in Desert Storm.

Human factors in crashes of commuter airplanes : S.P. Baker, M.W. Lamb, G. Li, and R.S. Dodd. Aviation, Space, and Environmental Medicine, 64(1).

Pilots and frequent travelers on commuter aircraft are exposed to higher risks of death or injury than those on major air carriers. To provide a better understanding of the circumstances of crashes of scheduled commuter airplanes, National Transportation Safety Board data were analyzed for all cases of death, serious injury, or major damage involving commuter airplanes during 1983-88, when 172 people were killed and 207 injured in 118 events. Three-fourths of cases involved inadequate pilot performance, notably poor handling of emergencies and improper instrument flying procedures. Pilot errors occurred disproportionately in bad weather, which played a role in 30% of crashes. Aircraft malfunctions were involved in 42% of crashes. Certain airplanes were overinvolved in gear-up landings or in crashes due to fuel mismanagement. Greater priority should be given to applying known preventive measures to the problem of commuter crashes.

Learning and technical progress in the commuter aircraft industry: an analysis of Embraer's experience

Companies in industrializing nations face major hurdles when moving into complex and highly competitive manufacturing industries. This paper examines the example of such an entrant: the Brazilian aircraft company, Enbraer. The paper is concerned with the technological strategy pursued by Embraer, and its learning experience with the Brasilia commuter turboprop, which achieved a 25% world-market share in its seat category, due in no small measure to its cost competitiveness and technological proficiency. The paper presents econometric evidence of substantial learning effects, as captured by the learning curve elasticities of the Brasilia, which conforms to frontier parameters. Although Embraer was successful in its early product offerings aimed at a narrow niche, its subsequent difficulties in moving to a broader product line and sustaining its technological development, illustrate some of the problems that industrializing nations' enterprises may encounter in building on a successful entry in technology-intensive industries at a time of growing competition, without crafting alliances to share the large associated technological and commercial risks.