In the certification activity of a new Flight Management System, the Applicant reported the presence of the
User Defined Approach (UDA) function accessible to the crew. This feature allows to support operations on
airfields for which no approved or published approach procedures are available.
Presence of this function within the FMS impairs compliance with the related CS 25 specifications CS 25.1301,
25.1302, 25.1309 and 25.1523.  The Applicant is not intending to perform neither a physical removal of the item (e.g. equipment, switches, antennas, etc.) not the inhibition of the function (e.g. SW pin-programming).
The Agency therefore intends to accept the proposal of the applicant to prohibit the use of this function for
the certification of the FMS, hence requesting a Deviation to the requirements applicable to the UDA
function.  See https://www.easa.europa.eu/document-library/product-certification-consultations/proposed-deviation-cs-251301-251302-251309-and

Note the ultimate acceptability criteria in this statement:  “Fulfilment of those mitigation factors has been assessed to comply with the following Essential Requirements of Annex II of Regulation (EU) 2018/1139: point 1.3.2, point 1.3.3, point 1.3.4, point 1.3.5, point 2.1, point 2.1(a), point 2.1(b), point 2.1(e), point 2.3, point 2.3(c).”