METHOD AND MEANS TO MAINTAIN GROUND TAKEOFF DISPLACEMENTS OF TRANSPORT CATEGORY AIRCRAFT MODIFICATIONS AT BASE VARIANT LEVEL

Abstract

The problem of improving the takeoff and landing runway characteristics of heavier modifications of the transport category aircraft was further developed on the condition of equality of ground displacements of heavier modifications and their base variant by creating a method of formation of the “take-off mass - thrust-to-weight ratio” characteristics and using the fundamentally new local structures of additional slotted spoilers in extendable flaps and additional energetic chambers in landing gear shock absorber systems. The development of such a method and the use of additional slotted spoilers and energetic chambers in the shock absorber systems can provide for the basing of heavier modifications at the aerodromes assigned for the base aircraft.

The problem of providing takeoff and landing characteristics (TLC) of more productive modifications of the transport category aircrafts is due to objective circumstances of ensuring their operation at the aerodromes assigned to the base aircraft on the basis of which the modifications are developed. The increase in productivity inevitably leads to an increase in the takeoff and landing mass and to an increase in the ground movements of modifications, i.e. the increase in the take-off and run distance, the distance of the rejected take-off and the required length of the runway. This increase significantly reduces flight safety.

In the article the method of selection of basic parameters of modifications according to TLC deterministic values is proposed. The idea of the method lies in the fact that the main parameters of the modifications, such as take-off weight, thrust-to-weight ratio, specific load on the wing, etc., are selected from the condition that the main TLC of the modifications (takeoff run length, landing run, decision-making speed, distance length of rejected take-off and the required length of the runway) should be approximately the same with the similar parameters of the base version.

By implementing this method, the areas for the existence of modifications of regional, mid-range and long-haul aircrafts within the coordinates "take-off mass-thrust-to-weight ratio" with a set of constraints, arising from changes in modifications, are determined. In addition, to implement such a method, it is proposed to use fundamentally new structures: additional slotted spoilers in extendable flaps and additional energetic chambers in the landing gear shock absorber systems. The development of such a method and the use of additional slotted spoilers and energetic chambers in the shock absorber systems can provide for the basing of heavier modifications at the aerodromes assigned for the base aircraft.

The implementation of the conceptual provisions proposed in this paper and the use of AEC in the shock absorber systems for the modification of the An-140 aircraft and with an increased take-off weight (m₀ = 3 t)of specific wing load of p = 432 kg / m² allows:

- to reduce the landing run of the aircraft modification by 136 m;

- to keep the required runway length of An-140 modifications (m₀ = 24 t) at the level of its basic version
(m₀ = 24 t) and, thus, to provide for the basing of heavier modifications of the An-140 aircraft on the airfields of the class 3;

- to significantly improve the takeoff and landing characteristics of the basic version of An-140 (m₀ = 21 t), i.e. to reduce the required length of the runway of this aircraft to 1150 m and thereby ensure its possible operation on the airfields of the class 4.