6.3.3.1 The point regarding the ability to obtain
the required data during on-board NOx testing is particularly
relevant to brake power. Although the case of directly coupled gearboxes
is considered in chapter 5, the engines,
as may be presented on board, could, in many applications, be arranged
such that the measurements of torque (as obtained from a specially
installed strain gauge) may not be possible due to the absence of
a clear shaft. Principal in this group would be generators, but engines
may also be coupled to pumps, hydraulic units, compressors, etc.
6.3.3.2 The engines driving such machinery would
typically have been tested against a water brake at the manufacture
stage prior to the permanent connection of the power-consuming unit
when installed on board. For generators this should not pose a problem
to use voltage and amperage measurements together with a manufacturer's
declared generator efficiency. For propeller-law-governed equipment,
a declared speed-power curve may be applied together with ensured
capability to measure engine speed, either from the free end or by
ratio of, for example, the camshaft speed.