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ITTC – Recommended
7.5-04
-01-01.1
Procedures and Guidelines Page 6 of 10
Full Scale Measurements
Speed and Power Trials
Preparation and Conduct of
Speed/Power Trials
Effective Date
2005
Revision
03
The bias limits of the instrumentation used
for the measurements should be known and assessed.
The instrumentation used for the on-boardmeasurements
must be calibrated before application
on board. If this is not possible, for some
reason, the consequences of this should be
highlighted in the final trial report. Electrical
calibration is recommended for the torque
measurement device and, in case of use during
the sea trials, for the thrust measurement device.
Further a calibration should be done for the
pick ups and the respective amplifiers used for
the measurement of the rate of revolutions. A
“calibration” of a (differential) GPS-System is
not possible without excessive measures, but at
least the function of the device should be
checked before use on board.
If portable radar tracking or (differential)
GPS is utilized, a Receiver/Transmitter (R/T)
unit or GPS antenna is to be installed. In case
the soft ware program used for the evaluation
of the data received does not allow for varying
positions on the uppermost deck of the ship the
antenna should be placed in a location along
the ship’s centerline as close to the ship’s CG
as possible. This location will ideally be located
on a mast or site that is clear of obstructions,
such as the ship’s superstructure.
4.4.2 Instrumentation Calibration Check
All shipboard signals to be recorded during
the trials must be adjusted to zero or should
have their zero value checked (e.g. for a (D)
GPS-device) after the instrumentation installation
is completed and prior to the trials. The
zero values of the torsiometers, the thrust
measurement devices and the devices for the
measurement of the rates of revolutions must
be checked before the trial runs start and after
they have been finished.
As part of the pre-trial calibration, the torsion
meters zero torque readings must be determined
since there is a residual torque in the
shaft, which is resting on the line shaft bearings.
This might be done in different ways; one possible
way is to use the jacking motors. The
shaft is jacked both ahead and astern and the
average of the readings noted. The zeroes are
set at the midpoint of the torque required to
jack each shaft ahead and the torque required to
jack each shaft astern. An allowance is normally
made for frictional losses in the stern
tube bearings.
As part of the pre-trial calibration for a ship
equipped with controllable pitch propellers,
maximum ahead pitch, the design pitch and the
maximum astern pitch should be determined
and then the ship indicators should be adjusted
to reflect the measurement.
4.5 Trial Conditions
Speed/Power trials require accurate position
data. The use of (D) GPS provides great latitude
in choosing a trial site. Regardless of the
instrumentation utilized for obtaining positional
data, the operational area should be free
from substantial small boat traffic.
The tracking range should be agreed between
the Trial Director and the ship’s master.
Draft, trim and displacement of the ship on
trials should be obtained by averaging the ship
draft mark readings. The ship should be
brought into a condition that is as close as possible
to the contract condition and/or the condi-