Description / Abstract:
This SAE Aerospace Standard (AS) provides guidelines for the
functional, performance, qualification
and acceptance testing, and documentation requirements for the
components of an airborne engine
vibration monitoring (EVM) system which is intended for use as a
turbojet engine rotor unbalance
indicating system, per FAR 25.1305 (D)(3) on transport category
airplanes.
For the purpose of this document, this means a system which can
provide real-time flight deck
displays of engine vibration caused by rotor unbalance, throughout the
flight envelope, which are
suitable for:
a. Relating to engine vibration limits (where such limits are
specified)
b. Use in ice shedding procedures
c. Helping the flight crew to determine which engine has the higher
level of vibration, following
an engine damage event.
As a minimum, the functional capability for such a system shall
include the ability to compute and
display vibration levels specifically related to the rotational
speed(s) of the engine rotor(s).
Systems which can produce only broadband vibration outputs have been
used in the past but they are
not considered suitable for the above purposes. Some EVM systems may
also generate other outputs,
suitable for such functions as engine vibration trend monitoring or
trim balance calculation, but
these are considered to be outside the scope of the requirements for a
minimum system.
This document also defines some recommended, optional, functions and
features which, while they are
outside the scope of minimum requirements, are nevertheless considered
to be highly desirable for a
practical system.
It should be noted that systems incorporating capabilities such as
described above are also
sometimes referred to by the abbreviation AVM. However, there are, or
can be, airborne measurements
taken of vibrations from sources other than the engines.
For the purpose of this document the more descriptive term, engine
vibration monitor (EVM), will be
used.
Purpose:
The purpose of this document is to provide guidance on the
requirements for airborne EVM systems
for turbojet engines on transport category airplanes.