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silver or cadmium plating and the lubricant used.
Testing
55. On completion of assembly, every production
and/or overhauled engine must be tested in a ’sealevel’
test cell (fig. 25-14), i.e. a test cell in which the
engine is run at ambient temperature and pressure
conditions, the resultant performance figures being
corrected to International Standard Atmosphere
(I.S.A.) sea-level conditions (Part 21).
56. To ensure that the engine performance meets
that guaranteed to the customer and the requirements
of the Government licensing and purchasing
authorities, each engine is tested to an acceptance
test schedule.
57. In addition to the ’sea-level’ tests, sample
engines are tested to a flight evaluation test
Overhaul
273
Fig. 25-12 Torque tightening.
Overhaul
274
Fig. 25-13 A high altitude test cell.
Fig. 25-14 A sea-level test cell.
schedule. These tests cover such characteristics as
anti-icing, combustion and reheat efficiencies,
performance, mechanical reliability, and oil and fuel
consumptions at the variety of conditions to which
the engine may be subjected during its operational
life. Flight evaluation testing can be effected by
installing the engine in an aircraft or in an altitude test
cell (fig. 25-13) to test the variations of air humidity,
pressure and temperature on the engine, its
accessories and the oil and fuel systems. When in an
aircraft, the engine is operated at the actual
atmospheric conditions specified in the schedule, but
in an altitude test cell, the engine is installed in an
enclosed cell and tested to the schedule in
conditions that are mechanically simulated.
58. Mechanical simulation comprises supplying the
engine inlet with an accurately controlled mass
airflow at the required temperature and humidity, and
adjusting the atmospheric pressure within the
exhaust cell to coincide with pressure at varying
altitudes.
59. The data which is accumulated from either ’sealevel’
or altitude testing is retained for future
development, engine life assessment, material capabilities
or any aspect of engine history.
60. During the testing of turbo-jet engines there is a
need to reduce the exhaust noise to within
acceptable limits. This may be achieved by several
different means, each involving costly equipment.
However, a typical silencer would do this by
expansion in the first section, damping by acoustic
tubes and final diffusion by a large exit through which
the hot gas would be directed upwards at a low
velocity.
Preparing for storage/despatch
61. The preparation of the engine/module for
storage and/or despatch is of major importance,
since storage and transportation calls for special
treatment to preserve the engine. To resist corrosion
during storage, the fuel system is inhibited by special
oil and all apertures are sealed off. The external and
internal surfaces of the engine are also protected by
special inhibiting powders or by paper impregnated
with inhibiting powder and the engine is enclosed in
a re-usable bag (fig. 25-15) or plastic sheeting into
which a specific amount of desiccant is inserted. If
transportation by rail or sea is involved, the inhibited
and bagged engine may be packed in a wooden
crate or metal case.
Overhaul
275
Fig. 25-15 Transportation stand and storage
bag.
277
Appendix 1
Conversion factors
UNIT ABBREVIATIONS
in = inch
ft = foot
yd = yard
oz = ounce
lb = pound
cwt = hundredweight
Btu = British thermal unit
hp = horsepower
Hg = mercury
s = second
min = minute
h = hour
f = force
W = watt
kW = kilowatt (Wx1000)
mm = millimetre (mx0.001)
m = metre
km = kilometre (mx1000)
g = gram
kg = kilogram
N = newton
Pa = pascal
kPa = kilopascal
J = Joule
kJ = kilojoule (Jx1000)
MJ = megajoule (Jx1 000 000)
CONVERSION FACTORS - Exact values are printed in bold type.
LENGTH 1 in = 25.4 mm
1 ft = 0.3048 m
1 mile = 1 .60934 km
1 International nautical mile = 1.852 km
AREA 1 in2 = 645.16 mm2
1 ft2 = 92903.04 mm2
VOLUME 1 UK fluid ounce = 28413.1 mm3
1 US fluid ounce = 29573.5 mm3
1 Imperial pint = 568261.0 mm3
1 US liquid pint = 473176.0 mm3
1 UK gallon = 4546090.0 mm3
1 US gallon = 3785410.0 mm3
1 in3 = 16387.1 mm3
1 ft3 = 0.0283168 m3
MASS 1 oz (avoir.) = 28. 3495 g
1 lb = 0.45359237 kg
1 UK ton = 1.01605 tonne
1 short ton (2000 lb) = 0.907 tonne
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