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

Available online at http://docs.lib.purdue.edu/jate Journal of Aviation Technology and Engineering 6:2 (2017) 80–88 Hybrid Buoyant Aircraft: Future STOL Aircraft for Interconnectivity of the Malaysian Islands Anwar ul Haque International Islamic University Malaysia (IIUM) Waqar Asrar Department of Mechanical Engineering, International Islamic University Malaysia (IIUM) Ashraf Ali Omar Department of Aeronautical Engineering, University of Tripoli Erwin Sulaeman Department of Mechanical Engineering, International Islamic University Malaysia (IIUM) Jaffar Syed Mohamed Ali Department of Mechanical Engineering, International Islamic University Malaysia (IIUM) Abstract 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 turbopropeller 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. Keywords: hybrid buoyant aircraft, green energy, PEST analysis http://dx.doi.org/10.7771/2159-6670.1138 A. ul Haque et al. / Journal of Aviation Technology and Engineering Introduction It is well-known that a substantial share of the aviation world market is the transport of passengers and goods. Over the years, the number of people traveling by air has also increased. According to a recent survey by International Air Transport Association (IATA, 2013), approximately 3 billion people traveled by air in 2013. Freight/cargo terminals of airports in major cities of the world are also heavily utilized. Due to heavy traffic, the airports are congested, which sometimes may result in delays in departure and takeoff times. Hybrid buoyant aircraft can solve these issues to an extent and can offer an economical traveling option with both less noise and less fuel consumption. Such aircraft can takeoff and land at airports where the freight system and its infrastructure are available to load and unload cargo (Rist, 2012). Most of the international airports are away from city centers; sometimes it takes a long time to reach the destination. Passengers can be transported by deploying hybrid buoyant aircraft such as airport–city center transfer. This idea is not new: Goodyear previously proposed the idea of airship missions in heavily populated areas that have noise and pollution issues (Ardema, 1981). Certified airships are already in operation in many countries such as Germany, Switzerland, and the United States, where their use is limited to the tourism sector only. A hybrid buoyant aircraft is a concept in which the lift to remain airborne is combined with buoyancy. As cited by Carichner and Nicolai (2013), a hybrid buoyant aircraft is an aircraft that combines the lift obtained from buoyancy effects, known as static lift, with that coming from the contour of the big hull, characterized as dynamic lift. With the help of a suitable propulsion system, such aircraft require a short runway to takeoff and land. However, fuel is used for thrust generation at a speed that is lower than that of any other STOL aircraft. The concept of hybrid buoyant aircraft came from airships; it is not wrong to state that airships have returned in the form of hybrid buoyant aircraft. These aircraft are mostly in the design, testing, and experimental phases and are always in a semibuoyant condition (Blake, 2013; ESTOLAS aircraft, 2012; Rist, 2012). Among them is the Dynalifter 81 (Rist, 2012), a plane disguised as an airship, its fuselage and wing providing half of the total lift; its prototype was flown in late 2012. The ESTOLAS aircraft (2012) is another hybrid buoyant aircraft, funded by the European Union, which is a novel concept of an aircraft with extremely short takeoff and landing on all surfaces. Hybrid buoyant aircraft have the potential to takeoff and land with short runway requirements. These aircraft will vary from light passenger aircraft to high payload cargo/ passenger types. In order to develop demonstration models, a number of research and development (R&D) activities are underway, including the certification requirement for integrating such aircraft in airspace. Its takeoff and landing segments are similar to those of a conventional aircraft and have the capability of short takeoff and landing. Also, there are some fundamental research projects at the academia level to fill in the gap: special methodology for conceptual design and experimental data for estimation of hybrid buoyant aircraft aerodynamic and stability characteristics (Haque et al., 2014a; Haque et al., 2014b; Haque et al., 2015; Haque et al., 2016). Pictorial views of some conceptual models (C-1 and C-2) can be found below in Figure 1. In the case of conventional aircraft, half of the fuel is used to keep it aloft, whereas the use of aerostatic lift in hybrid buoyant aircraft has the potential to reduce the amount of fuel required to keep the aircraft aloft (Prentice & Knotts, 2014). Hybrid buoyant aircraft combine the aerodynamic (similar to conventional aircraft) and aerostatic lift (similar to airships) and are considered the ‘‘best of the both worlds’’ by Zhang, Han, and Song (2009). Helium is commonly used as the lifting gas to provide buoyant lift. On average, helium gas lifting capacity is about 1.05 kg/m3 (Carichner & Nicolai, 2013). It is important to note that if the lifting gas bag can freely expand or contract, then the aerostatic lift due to the buoyancy effects remains consistent until pressure height of the buoyant or hybrid buoyant aerial vehicle (Raymer, 2012). In this way, the load balanced by the aerostatic lift remains constant until pressure height. As per the Archimedes principle, buoyancy force is dependent upon the volume immersed in fluid, and its estimation is critical for calculating net weight Wnet. Equation 1 is the gross takeoff weight minus the weight balanced by the aerostatic lift, Figure 1. Pictorial views of clean configurations of hybrid buoyant aircraft concepts. 82 A. ul Haque et al. / Journal of Aviation Technology and Engineering and it is the actual weight carried by the wings or other liftgenerating components. The gross takeoff mass is expressed in Equation 2, by Raymer (2012): Wnet ~(mGTM |g{Lbu (...truncated)