During a standard Instrument Landing System (ILS) approach, I typically arm the VOR/LOC (Boeing 737) to capture the localiser¹ once on an intercept course. Upon clearance for the approach, I then arm APP mode to capture the glideslope.

According to my company's Standard Operating Procedures (SOPs), APP mode can only be armed once cleared for the approach and within the Designated Operational Coverage (DOC) of the ILS.

My theory textbooks define ILS coverage as extending "18 NM within 10° of either side of the course centreline and 10 NM within 35° of the course centreline."

Is this the typical DOC that my company SOPs refer to?

Typically, I arm the approach mode approximately 10-12 NM from landing. However, a fellow pilot I flew with recently insisted that APP mode should be no armed further than 10 NM due to DOC. Can someone clarify the typical DOC requirements for ILS approaches

^{1: American editors, please resist the urge to correct the spelling. I am a British English user and localiser is an acceptable spelling. Thanks 😊}

During a standard Instrument Landing System (ILS) approach, I typically arm the VOR/LOC (Boeing 737) to capture the localiser¹ once on an intercept course. Upon clearance for the approach, I then arm APP mode to capture the glideslope.

According to my company's Standard Operating Procedures (SOPs), APP mode can only be armed once cleared for the approach and within the Designated Operational Coverage (DOC) of the ILS.

My theory textbooks define ILS coverage as extending "18 NM within 10° of either side of the course centreline and 10 NM within 35° of the course centreline."

Is this the typical DOC that my company SOPs refer to?

Typically, I arm the approach mode approximately 10-12 NM from landing. However, a fellow pilot I flew with recently insisted that APP mode should be no armed further than 10 NM due to DOC. Can someone clarify the typical DOC requirements for ILS approaches

For example, see this NOTAM which describes the DOC into Bergamo as being 25nm/10000ft for IBRM ILS RWY 28:

A4884/24 NOTAMN
Q)LIMM/QIDXX/I/NBO/A/000/999/4540N00942E005
A) LIME
B) 2406121049 C) PERM
E) DME 'IBRM' ASSOCIATED WITH ILS RWY 28 DESIGNATED OPERATIONAL COVERAGE: 25 NM/10000FT REF AIP AD 2 .19 'RADIO NAVIGATION AND LANDING AIDS' COLUMN 7 'DESIGNATED OPERATIONAL COVERAGE LIMITATIONS'

^{1: American editors, please resist the urge to correct the spelling. I am a British English user and localiser is an acceptable spelling. Thanks 😊}