Seems to be an American thing 411? From Jeppesen:
There are many aircraft today that are
equipped with vertical navigation equipment
and are capable and authorized to fly the
computed descent angle on non-precision
approaches. Because of this capability and
the airlines’ desire to use more of the
capability in their FMSs, the FAA issued a Joint
flight Standards handbook bulletin for Air
Transportation (HBAT) and General Aviation
(HBGA). The Bulletin number is HBAT 99-08
and HBGA 99-12 and is applicable to
operators under FAR 121, 125, 129, or 135.
My Bold
and
Most aviation authorities and industry leaders
have recognized the safety benefits that will
be gained by reducing the number of nonprecision
approaches that don’t have vertical
guidance. The addition of vertical guidance
should help to reduce the number of CFIT
(controlled flight into terrain) accidents.
Recently, the NTSB has recommended that
aircraft with onboard capabilities for vertical
guidance should be required to use them
during non-precision approaches. They have
also recommended that within 10 years all
non-precision approaches approved for air
carriers should incorporate constant-angle
descents with vertical guidance from
onboard systems.
Which FAR do you fly under? Have you seen the bulletin?