Browse Topic: Business and general aviation aircraft
Fuel cell systems have achieved a significant level of technological maturity in ground-based mobility over the past two decades. In particular, commercially available fuel cell propulsion systems are now in serial production for passenger cars and city buses, and are already in regular commercial operation. In the segment of heavy-duty vehicles - such as trucks and other long-haul applications - small-series production and technology demonstrators are currently available and are on the verge of entering the mainstream market. These developments have resulted in well-proven system architectures, sophisticated balance-of-plant components, and established supply chains. In contrast, the utilization of fuel cell propulsion in aviation is still at a very early stage. At present, only a handful of individual prototypes and technology demonstrators - mostly for small aircraft - exist, while serial production remains far in the future. Particularly in the field of lightweight, small, electrical vertical take-off and landing (eVTOL) aircraft there is a unique opportunity to leverage the proven fuel cell systems developed for ground vehicles, adapt them, and further develop them to meet aviation-specific requirements. Such an approach can shorten development timelines and reduce technical risks. Transferring existing fuel cell technologies into aviation, however, is far from a straightforward process. One decisive difference lies in the required specific power density. Aircraft - especially eVTOL - demand significantly higher power densities than those delivered by current commercial fuel cell systems from the automotive sector. This requires a direct adjustment of the stack design and system architecture. Likewise, thermal management poses particular challenges. Whereas piston engines and gas turbines discharge a large portion of their waste heat via exhaust gases, fuel cells must remove all waste heat directly through their cooling systems. This requires efficient radiators capable of transferring heat from the coolant to ambient air. Larger radiator surfaces, however, increase both total aircraft mass and aerodynamic drag, making compact radiator designs essential for aviation applications.
Aircraft icing is a serious problem. There is a need for a passive durable solution for both commercial and general aviation aircraft. Scientists at NASA Langley have been developing passive solutions to this problem focusing on coatings for aircraft surfaces that will reduce the adhesion of impact ice.
This SAE Aerospace Recommended Practice (ARP) provides design guidelines for aircraft mechanical control systems and components. Topics contained in this document include design requirements, system design and installation guidelines, and component design practices for primary flight controls, secondary flight controls, and utility controls.
This document contains minimum operational performance specification (MOPS) of active on-board INFLIGHT ICING DETECTION SYSTEMS (FIDS). This MOPS specifies FIDS operational performance which is the minimum necessary to satisfy regulatory requirements for the design and manufacture of the equipment to a minimum standard and guidance towards acceptable means of compliance when installed on an AIRCRAFT. Detection of ICE accreted on the AIRCRAFT during ground operations is not considered in this document. This MOPS was written for the use of FIDS on AIRCRAFT as defined in 1.3 and 2.3. Expected minimum performance specifications for FIDS and their functions are provided in Section 3. The minimum performance requirements as defined in Section 3 do not consider SYSTEM performance as installed on the AIRCRAFT. Performance in excess of the minimum performance may be required by the SYSTEM installed on an AIRCRAFT in order to meet regulatory or operational requirements. This topic is considered in Section 6. This MOPS document is structured as follows: Operational performance specifications for functions or COMPONENTS that refer to equipment capabilities that exceed the stated minimum requirements are identified as optional features. The word “equipment” as used in this document includes all COMPONENTS and units necessary for the SYSTEM to properly perform its intended function(s). For example, the “equipment” may include all of the COMPONENTS listed in 1.4. It should not be inferred that each FIDS design will necessarily include all of the COMPONENTS or units listed in that Section. This will depend on the specific design chosen by the FIDS manufacturer.
The trend of powertrain electrification is quickly spreading from the automotive field into many other sectors. For ultra-light aircraft, needing a total installed propulsion power up to 150 kW, the combination of a specifically developed internal combustion engine (ICE) integrated with a state-of-the-art electric system (electric motor, inverter and battery) appears particularly promising. The dimensions and weight of ICE can be strongly reduced (downsizing), so that it can operate at higher efficiency at typical cruise conditions; a large power reserve is available for emergency maneuvers; in comparison to a full electric airplane, the hybrid powertrain makes possible to fly at zero emissions for a much longer time, or with a much heavier payload. On the other hand, the packaging of a hybrid powertrain into existing aircraft requires a specific design of the thermal engine, that must be light, compact, highly reliable and fuel efficient. The last aspect has a direct impact on the performance of the aircraft, since the mission range depends on the capacity of the fuel tanks, which, in turn, is limited by the aircraft total weight. The two-stroke cycle engine is far from a novelty for ultra-light aircraft; unfortunately, the specific fuel consumption and pollutant emissions of the conventional engines is quite high, in comparison to their 4-Stroke (4S) counterparts. The aim of the project presented in this paper is to develop a new type of 2-Stroke SI engine, able to match lightness, fuel efficiency and low pollutant emissions at a reasonable cost. The proposed ICE weights less than 60 kg, it delivers 110 kW@6000 rpm, along with a brake specific fuel consumption lower than 260 g/kWh in all the most relevant operating conditions. The paper describes the design of the new engine, with particular attention to the optimization of the scavenging system (without poppet valves) and the design of a low pressure direct injection system. The process is supported by CFD 1D and 3D simulations. As far as the design of the injection system is concerned, the main goal was to obtain a fuel trapping ratio higher than 95%, along with a properly stratified charge at combustion onset, when considering the most critical operating condition (maximum engine speed and load). The main optimized parameters include the number of injectors, their locations, the injection timing and duration.
The purpose of this document is to give the reader an overview of the document package which makes up AIR825, Introduction to Oxygen Equipment for Aircraft, and a basic overview (see Section 4) of the operational concerns driven by human physiology during altitude exposure.
This section presents the basic equations for computing ice protection requirements for nontransparent and transparent surfaces and for fog and frost protection of windshields. Simplified graphical presentations suitable for preliminary design and a description of various types of ice, fog, frost, and rain protection systems are also presented.
The scope of this ARP embraces the description of a configuration for a ground-plane microphone installation that may be used to determine sound pressure levels equivalent to those which would have been measured in an acoustic freefield at the microphone location. The one-third - octave-band center-frequency range over which equivalent freefield sound pressure levels may be obtained is from as low as 50 Hz to at least as high as 10,000 Hz. The specific application of the measurement technique described in this ARP is the determination of the equivalent freefield sound pressure levels of the noise produced by propeller-driven light aircraft, in flight, for sound incidence angles within 30 degrees of the normal to the ground. For larger angles to the normal, additional adjustments may be necessary which are outside the scope of this ARP. Caution needs to be exercised, therefore, if the recommended configuration is used to measure the noise from aircraft other than those driven by propeller powerplants, in particular, when full spectral information is required (especially outside the range of 30 degrees to the normal to the ground surface), or when measurements of time-integrated noise descriptors are required.
Many electric vertical take-off and landing (eVTOL) aircraft intended for the urban air mobility (UAM) market are currently being designed with multirotor configurations using variable speed fixed-pitch, rigid rotors for lift. These types of rotors, which are similar in construction to general aviation airplane propellers, are simpler than helicopter rotors and have no moving parts in the rotating frame. This paper discusses wind-tunnel testing of a full-scale, UAM multirotor size, fixed-pitch, rigid rotor with a focus on vibratory blade loads and on the ability to predict these loads with comprehensive analysis. Test results show that vibratory loads are very high, with peak-to-peak magnitudes up to three times greater than the steady component. Correlation of test data to comprehensive analysis using geometrically exact composite beam structural elements and dynamic inflow wake modeling captures the trends in the steady and vibratory loads, but under-predicts the magnitudes by up to 50%. The paper also discusses the physical sources of the observed vibratory loads and suggests potential options for mitigating their magnitude.
This work aims to present a methodology for the design of conventional control surfaces for light aircraft. Based on renowned aeronautical engineering references and standards, the theoretical framework presents the concepts of calculation for each flight phase particularity for each control surface in addition to a database with intervals of surfaces and their respective deflections of various aircraft. The methodology used takes into account the suggested steps for the aircraft design, where the dimensions are present in the preliminary design, according to the characteristics intended in the conceptual stage to develop conventional control surfaces aiming at the simplicity of design and the optimal response of control. The use of MATLAB and CFD software for data calculation and iterations are essential for the correct observance and evaluation of the obtained results. A comparative table and graphs will be elaborated for better visualization of the efficiency and behavior of each dimensioned model aiming at the best levels of acceptability according to the norms used in the design of aircraft, observing their occurrence through flight analysis and direct feedback of the pilot. Finally, the optimally sized surface will be used.
Currently automotive engines are reciprocating or Wankel rotary engine types. Reciprocating engines are bulky, heavy and complex, mainly due to the intake and exhaust valves and their associated cam-train. Wankel engines have a low rotor rev limit, and have inefficient sealing of the apex seals leading to poor economy and undesirable emission gases. The Rotary Engine Development Agency (REDA) has designed a new three-chamber rotary internal combustion engine concept using an adaptation of the patented Szorenyi Curve. The new design is an evolution of the design which was the subject of SAE Technical Paper 2017-01-2413 and SAE publication ‘So You Want to Design Engines: UAV Propulsion Systems’. This paper describes the features of the new three-chamber engine concept and includes an analysis of the major shortcomings of the Wankel engine. The Wankel engine’s geometry results in excessive crankshaft deflection at high engine revs due to the centrifugal force of the rotor which is eccentric to the crankshaft. This results in a low rotational speed limit. Analysis of the Wankel design reveals that the rotational speed limit cannot be increased by increasing the diameter of the crankshaft. Also, analysis of the apex seal reveals that the shape of the stator accelerates the seal inwards during the intake and power stroke and, at the same time, the seal experiences a large change in its contact angle with the stator surface. These effects combine to produce poor conditions for sealing the combustion chamber of the Wankel engine. The paper identifies that the Szorenyi three-chamber engine design does not have these same issues because its symmetrical rotor enables a high rotational speed, and its continuously concave stator profile ensures an outward acceleration of the apex seal and much less change of contact angle with the stator surface. The paper concludes that the Szorenyi engine has the potential to replace Wankel and reciprocating engines in a range of applications and is particularly suited to light aircraft.
Given approximately one million small and light aircraft in operation worldwide, icing detection and icing quantification of in-flight icing are still an open research topic. Despite technical means are available to de-ice on ground, there is a lack of a suitable control system based on sensor data to de-ice while the aircraft is airborne. Most often, it is still task of the pilot to visually inspect the icing status of the airfoil and/or other critical parts of the aircraft such as engine air intakes, which distracts the flight crew from flying the aircraft especially in IMC conditions. Based on preliminary simulation and tests in 2014 in a collaborative research project lasting from 2015 until 2018, the technology of energy self-sustaining, wireless, self-adhesive smart sensors for industrial sensing in an aerodynamically critical environment (i.e. wind turbines) was further investigated to fulfil general aviation requirements. Prototype hardware setups have been designed and built for application on aircraft. In test flights carried out in Scotland in late 2017, the functionality of the system could be demonstrated. It could be shown that a wireless, energy self-sustaining detection system for early icing can be implemented based on currently available technologies and components. Additionally, it could be shown that detection sensitivity is sufficient to detect ice at very thin layers.
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