. There is discussed the amplitude-polarization met hod of a moving object pitch angle detection using the radio beacon horizontally polar ized signals. The moving object pitch angle estimation is done using the ratio of the in-phase orthogonal horizontal linearly polarized radio beacon amplitudes of the signals received wit hin the linearly polarized basis. 1. Introduction The roll and the pitch angles describing the flying apparatus (FA) movement relatively its mass center are not measured now in the horizontal co-ordinate system (HCS) by the modern angle estimating systems (MAS) [1]. In the practical FA navigation t here are used onboard inertial systems of orientation [2,3]. Unfortunately these systems are constantly accumulate the errors of measurement [2,3]. This investigation means to value the possibility o f horizontally polarized beacon signals application for the FA pitch angles estimation. In order to develop a new method of the FA navigat ion elements estimation it is necessary to present the illuminated and the received vector sig nals in different polarization basises and in sever al co-ordinate systems. The choice of the reference co -ordinate system (RCS) depending on the beacon and the FA own co-ordinate system (OCS) depending o n its building axes as well as the choice of the measuring co-ordinate system (MCS) depending on the onboard receiving antenna and its UHF elements can be arbitrary and is defined by peculia rities of the problem under consideration. 2. Idea of the amplitude-polarization method The idea of the amplitude-polarization method for a moving object pitch angle detection is as follows. Let’s suggest that the beacon is at the point ( О) within the Cartesian co-ordinate system (zero of the immobile RCS). Axes OX and OZ are horizontal (plane XOZ ) and the axe OY is vertical. The radio beacon illuminates in the direction of the axe OZ horizontally polarized signal as a flat simple harmonic wave (fig. 1a). The illuminated wave within the linear polarization basis (LPB) is presented as a projection of the electric field vector E on the plane XOY perpendicular to the propagation direction OZ . In such a case vector E , in the plane XOZ going along the axe OZ graphically present the horizontally polarized wave (fig. 1a). Fig.1 Illustrates the amplitude-polarization method for a moving object pitch angle detection The FA is moving perpendicular to the axe OZ . Let’s consider OCS connected with the FA body as a moving Cartesian system ,c c X O Y ′ made of the length way cO X ′ and vertical cO Y ′ axes of the FA. O′ is the zero point of the system coinciding the FA mass center. The axe O Z ′ goes along the direction of the signal illumination OZ. Axes cO X ′ and cO Y ′ in the plane of RCS depend on the FA pitch angle ξ. If there is no pitch the axe cO Y ′ goes vertically up and coincides the axe OY , the axe cO X ′ coincides the FA RCS. When there is the FA pitch a ngle the axe cO X ′ changes the direction and the angle between the vector E and the axes cO X ′ is equal the FA pitch angle ξ. This provides the physical background of the ξ measurement. If the axe cO X ′ is above the horizontal plane XOZ , the pitch angle is negative (- ξ) if the axe cO X ′ is below the horizontal plane XOZ , the pitch angle is positive (+ ξ) [1,3,4]. When there is no FA pitch angle the axe cO X ′ and the vector E coincide (fig. 1.b). In order to measure the pitch angle ξ let’s make MCS X O Y ′ ′ ′ onboard the FA in such a way that axes O X ′ ′ and O Y ′ ′ make angle 4θ=π with the FA length way cO X ′ and vertical cO Y ′ axes (fig. 1.b). Polarized electromagnetic waves are received by the FA onboard antenna with lobe axe is perpendicular to the FA movement. There is a linear polarized divider (LPD) in the antenna. The LPD orts coincide the co-ordinate axes O X ′ ′ and O Y ′ ′. Horizontally polarized waves are also received by the LPD which orts also coincide the co-ordinate ax es O X ′ ′ and O Y ′ ′. The chosen LPD orts orientation allows to divide the received horizonta lly polarized wave (vector E ) in to two in-phase orthogonally linearly polarized components xE′ and yE′ . Measured amplitudes xA′ and yA′ of xE′ and yE′ allows to calculate the FA pitch angle ξ. Let’s find the relation of the amplitudes xA′ and yA′, phases x′ϕ and y′ϕ of xE′ and yE′ with the FA pitch angle ξ. The Johns vector and matrixes [5,6] can be used t o describe this relation. Signals at the LPD outputs without temporary depend ence can be found as follows [7]: []()()1 ,xE R R E ′= Π θ ±ξ         (1) []()()2 ,yE R R E ′= Π θ ±ξ         (2) where 1 0E  =     - Johns vector of the illuminated by the beacon ho rizontally polarized wave written in the linearly polarized basis. ( )cos sin sin cos Rξ ± ξ   ±ξ =       ξ ξ   ∓ - operator of the pitch angle ±ξ turn; +ξ - the pitch is positive when the FA length way axe is above the plane XOZ [4]; −ξ - the pitch is negative when the FA length way axe is below the plane XOZ [4]; ( )cos sin sin cos Rθ − θ   θ =       θ θ   - operator of the −θ turn in the plane XOY [5,6], ( θ is the angle of MCS X O Y ′ ′ ′ orientation relatively FA OCS c c X O X ′; [ ]11 0 0 0   Π =     - the Johns operator of the LPD first shoulder whi ch own ort has the same direction as the vector xE′ . [ ]20 0 0 1   Π =     - the Johns operator of the LPD second shoulder whi ch own ort has the same direction as the vector yE′ . After calculation (1) and (2) () cos 0xE′θ±ξ   =     , (3) ( )0 sin yE′  =  θ±ξ    . (4) So the outputs of the two-canal receiver, when (3) and (4) are taken into consideration, are () cos xE′= θ±ξ , (5) () sin yE′= θ±ξ . (6) Taking into account (5) and (6), the phase x′ϕ and ,y′ϕ as well as the ratio of signal amplitudes xA′ and yA′ at the outputs of the receiver having, for example, linear amplitude characteristics and a linear detector has the form 0x y ′ ′ϕ =ϕ = ° (7) and () ( )( )sin cos y xAtg A′ ′θ±ξ = = θ±ξ θ±ξ . (8) Putting 4θ=π in (8) [ ] arctg , 4y xArad A′ ′    π  ξ =± −           (9) where «+» and «-» mean positive and negative FA pit ch. Equation (9) shows that if 1y xA A′ ′= the FA pitch angle 0ξ= (fig. 1.b), if 1y xA A′ ′> , 0ξ< (fig. 1.c), if 1y xA A′ ′<, 0ξ> (fig. 1.d). If the two-channel receiver has logarithmic amplitu de characteristics and a linear detector, then (9) is converted to the form [ ]lg arctg 10 . 4y xA Arad ′ ′    π    ξ =± −           (10) 4. Conclusion When the radio beacon illuminates horizontally pol arized waves and the electric field vector E lies in the horizontal plane, the FA pitch is calculated us ing the ratio of in-phase orthogonal linearly polar ized amplitudes at the FA shoulders outputs. The suggested method of the FA pitch angle measurem ent, compared with those used in practice , is based on a new physical principle an d means to use electronic means of measurement utilizing vector properties of signals. The beacon signal polarization characteristics allo ws first to avoid errors of measurement accumulation. On the other hand, it allows for join t complex measurements of the aircraft pitch angle using inertial and radio-technical navigation aids. Acknowledgments This study was supported by the Ministry of Science and Education of the Russian Federation, project no. FEWM-2020-0039.