6.3.3.1 The point regarding the ability to obtain
the required data during onboard NOx testing is particularly
relevant to brake power. Although the case of directly coupled gearboxes
is considered in chapter 5 (5.1.7),
an engine, 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 context would be generators,
but engines may also be coupled to pumps, hydraulic units, compressors,
etc.
6.3.3.2 The engines driving the machinery given
in 6.3.3.1 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 it 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.