Method for enabling landing on an offset runway

A method for determining a distance of an aircraft from an offset runway during a landing by offset approach utilizing a Multimode Reception Device (MMR) and a radioaltimeter, the offset runway being situated at a distance D from a main runway equipped with at least one elevation beacon, comprising:

• determining a height h at which the aircraft is situated, the height being determined with respect to a point T1 of the offset runway, the height being measured by the radioaltimeter with which the aircraft is equipped and thus corresponds to a perpendicular height between the aircraft and ground,
• determining an angle of elevation φ based on a MLS mode of the MMR by using information provided by the at least one elevation beacon with which said main runway is equipped,
• determining a value of a distance ρ of the aircraft from an azimuth beacon by using the following formula:
• ρ
• =
• (
• h
• Tan
• ⁡
• (
• φ
• )
• -
• D
• ⁢
• ⁢
• 2
• Cos
• ⁡
• (
• θ
• )
• )
• 2
• +
• h
• 2
• where θ and φ are angles decoded by the MMR corresponding respectively to an angle between the aircraft and the azimuth beacon and an angle between the aircraft and the elevation beacon, and D2 is defined as a distance between the azimuth beacon and the elevation beacon along the x axis, with x, y and z coordinates of the aircraft being in a reference frame of the elevation beacon,
• using said distance ρ to obtain a point of location of the aircraft in an offset runway reference frame.