Rotorcraft fitted with a radioaltimeter having plane antennas and a lens for modifying the field of view of the antennas

A method of measuring the height of a rotorcraft above the ground by means of a radioaltimeter using a computer that determines the height of the rotorcraft above the ground on the basis of data supplied by radio apparatus including at least one set of two antennas that are protected by at least one radome, the antennas being of plane configuration and being installed on the underside of the rotorcraft, as considered when the rotorcraft is standing on the ground, the antennas defining between them a “basic” field of view of the radioaltimeter and supplying the data to the computer by exchanging electromagnetic signals between the antennas, wherein the rotorcraft is also provided with sling equipment for transporting a load, and the method comprises an operation of modifying the basic field of view of the radioaltimeter by at least one lens as a function of whether or not a given load that is to be transported swinging under the rotorcraft by the sling equipment will interfere in the basic field of view of the radioaltimeter, the at least one lens being used selectively depending on whether the field of mobility of the load modifies the basic field of view of the radioaltimeter, as follows:

• in the event of the sling equipment not transporting a load, then the radioaltimeter produces a field of view having a predefined optimum scope, referred to as the optimum field of view;
• and
• in the event of the sling equipment transporting a load, then the radioaltimeter produces a “limited” field of view of scope smaller than the scope of the optimum field of view, the limited field of view being identified by excluding from the optimum field of view a previously determined field of mobility of the load transported by the sling equipment and as considered at least along the longitudinally-extending axis of the rotorcraft.