Reducing take-off and landing distances for regional turboprop aircraft

The increased efficiency of turboprop engines in cruising flight as well as low operating costs have determined the economic feasibility of using regional propeller-driven aircraft to transport 40–80 passengers on short routes within one country or connecting two nearby regions (for example, in Russia). The aerodynamic performance requirements for regional aircraft, determined from typical flight missions for the Russian and European markets differ greatly in range and required runway lengths. The typical flight range in Europe is about 800 km, while in Russia it increases to 1500 km due to the limited number of airports and aerodromes in operation. The limitation on runway length is 1300 m (airfield class G) for aircraft with a maximum take-off weight and 1000 m (class D) with a payload of up to 70% of the maximum value. The ability to take off and land from unpaved runways is also an essential requirement in Russia. This leads to a more complex design and an increase in the weight of the airframe, as well as to the need to increase the wing lift. Most of the operating European regional aircraft previously did not have tight restrictions on runway lengths and their takeoff and landing characteristics were not active constraints when forming wing configurations. However, the recently observed growing demand for air travel leads to a significant increase in the load on hub airports and, as a result, to the delay of many flights. One of the possible ways to solve this problem is to relieve the major hub airports by transferring regional aircraft service to nearby local airports. This will require both the modernization of existing airports and the development of a new generation of aircraft with short takeoff and landing distances (STOL). The development of STOL aircraft which are capable of connecting local airports and small towns has been conducted for many years. The STOL performance can be achieved by both developing an effective high-lift system with increased lift effectiveness and wing load alleviation. Wing load alleviation, often used in the light aircraft transitional category, leads to deterioration of cruising performance and increased sensitivity to atmospheric turbulence, especially at low altitudes. This makes difficult to track the final approach paths when controlling the pitch angle by deflecting the elevator. Therefore, a more preferable and more often considered option to reduce takeoff and landing distances of commercial airplanes is the increase of lift performance in combination with a set of additional technical solutions. Significant advances in the application of computational techniques for the development of swept wing high lift devices for long-haul aircraft with high lifting properties (Cy max ≈ 3), including a retractable Fowler flap and a three-position slat, make it possible to use a similar approach to the design of high-lift system for new regional aircraft. Taking into account the specifics of aircraft operation at local aerodromes, a complex of technical solutions has been considered to increase wing lift at low flight speeds, as well as additional measures to reduce the landing distance. The results of computational and experimental studies of the proposed technical solutions are presented with an assessment of the effectiveness of their use on a regional aircraft of the ATR 42-600 type.