ASTM D6812-04a(2019)
(Practice)Standard Practice for Ground-Based Octane Rating Procedures for Turbocharged/Supercharged Spark Ignition Aircraft Engines
Standard Practice for Ground-Based Octane Rating Procedures for Turbocharged/Supercharged Spark Ignition Aircraft Engines
SIGNIFICANCE AND USE
5.1 This practice is used as a basis for determining the minimum ground-based octane requirement of turbocharged/supercharged aircraft engines by use of PRFs and RFs.
5.2 Results from standardized octane ratings will play an important role in defining the octane requirement of a given aircraft engine, which can be applied in an effort to determine a fleet requirement.
SCOPE
1.1 This practice covers ground-based octane rating procedures for turbocharged/supercharged spark ignition aircraft engines. This practice has been developed to allow the widest range of applicability possible but may not be appropriate for all engine types. This practice is specifically directed to ground-based testing and actual in-flight octane ratings may produce significantly different results.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
- Status
- Published
- Publication Date
- 30-Apr-2019
- Technical Committee
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
- Drafting Committee
- D02.J0.02 - Aviation Piston Engine Fuels
Relations
- Effective Date
- 01-Mar-2024
- Effective Date
- 01-Nov-2023
- Effective Date
- 01-Oct-2023
- Effective Date
- 01-Oct-2017
- Effective Date
- 01-Dec-2016
- Effective Date
- 01-Jan-2016
- Effective Date
- 01-Oct-2013
- Effective Date
- 15-Jul-2013
- Effective Date
- 01-Jun-2013
- Effective Date
- 01-Oct-2010
- Effective Date
- 01-Oct-2009
- Effective Date
- 01-May-2008
- Effective Date
- 01-Dec-2007
- Effective Date
- 01-Mar-2007
- Effective Date
- 15-Jan-2007
Overview
ASTM D6812-04a(2019) - Standard Practice for Ground-Based Octane Rating Procedures for Turbocharged/Supercharged Spark Ignition Aircraft Engines provides a systematic approach for assessing the minimum octane requirements of turbocharged and supercharged piston aircraft engines using ground-based test methods. This standard is crucial for manufacturers, maintenance providers, and operators of aviation piston engines requiring precise fuel octane specifications to ensure optimal performance and safety.
Adopting this practice ensures that octane requirements are established through consistent, repeatable procedures. While developed for broad applicability, the standard is tailored to ground-based environments; actual in-flight octane performance may vary. Users are responsible for ensuring compliance with safety, health, and local regulatory requirements.
Key Topics
- Octane Requirement Determination: Procedures for identifying the minimum ground-based octane number required by turbocharged or supercharged spark ignition aircraft engines using primary reference fuels (PRFs) and reference fuels (RFs).
- Stable Testing Conditions: The importance of conducting tests only when engine temperatures, fuel flows, and operational parameters remain within specified tolerances to ensure reliable data.
- Knock Detection and Quantification: Guidance on instrumentation and methodology for sensing knock (abnormal combustion) within the engine during octane testing, which is essential for correct octane classification.
- Ground-Based Focus: Test procedures are intentionally restricted to ground environments such as test cells or dynamometers for repeatability and safety.
- Reporting Requirements: Documentation steps that ensure traceable, accurate results-including recording environmental conditions, engine setup, and detailed knock event data.
- Fleet and Engine Application: Insights into how individual engine test results can influence broader fleet-wide octane requirement determinations.
Applications
- Engine Certification and Conformity: Aircraft engine manufacturers utilize ASTM D6812 to validate that new, remanufactured, or overhauled turbocharged or supercharged spark ignition engines meet required octane specifications before service.
- Fuel Compatibility Assessments: Maintenance organizations and operators use these procedures to align engine fuel needs with available aviation gasoline grades, ensuring operational reliability and optimizing engine longevity by preventing knock-related damage.
- Regulatory Compliance: Satisfying aviation safety authorities’ demands for documented, standardized octane requirement data as part of engine and fuel certification processes.
- Performance Benchmarking: Comparative evaluations of different engine configurations, fuels, or operational strategies to maximize efficiency, reduce costs, and enhance safety.
- Fleet Management: Establishing fleet-wide octane requirements based on collected engine test results, supporting large-scale operational planning and fuel procurement.
Related Standards
- ASTM D2700: Test Method for Motor Octane Number of Spark-Ignition Engine Fuel – referenced for confirming the octane quality of PRFs and validating the fuels used in engine octane rating.
- ASTM International Aviation Fuel Standards: Complementary specifications relevant to aviation gasoline composition, properties, and testing methods.
- World Trade Organization TBT Principles: This standard aligns with internationally recognized guidelines for the development of standards to minimize technical barriers to trade.
Keywords: ASTM D6812, octane rating, turbocharged aircraft engine, supercharged engine, spark ignition, ground-based engine testing, aviation fuel, knock detection, engine certification, reference fuels, motor octane number, aviation standards.
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Frequently Asked Questions
ASTM D6812-04a(2019) is a standard published by ASTM International. Its full title is "Standard Practice for Ground-Based Octane Rating Procedures for Turbocharged/Supercharged Spark Ignition Aircraft Engines". This standard covers: SIGNIFICANCE AND USE 5.1 This practice is used as a basis for determining the minimum ground-based octane requirement of turbocharged/supercharged aircraft engines by use of PRFs and RFs. 5.2 Results from standardized octane ratings will play an important role in defining the octane requirement of a given aircraft engine, which can be applied in an effort to determine a fleet requirement. SCOPE 1.1 This practice covers ground-based octane rating procedures for turbocharged/supercharged spark ignition aircraft engines. This practice has been developed to allow the widest range of applicability possible but may not be appropriate for all engine types. This practice is specifically directed to ground-based testing and actual in-flight octane ratings may produce significantly different results. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
SIGNIFICANCE AND USE 5.1 This practice is used as a basis for determining the minimum ground-based octane requirement of turbocharged/supercharged aircraft engines by use of PRFs and RFs. 5.2 Results from standardized octane ratings will play an important role in defining the octane requirement of a given aircraft engine, which can be applied in an effort to determine a fleet requirement. SCOPE 1.1 This practice covers ground-based octane rating procedures for turbocharged/supercharged spark ignition aircraft engines. This practice has been developed to allow the widest range of applicability possible but may not be appropriate for all engine types. This practice is specifically directed to ground-based testing and actual in-flight octane ratings may produce significantly different results. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
ASTM D6812-04a(2019) is classified under the following ICS (International Classification for Standards) categories: 75.160.20 - Liquid fuels. The ICS classification helps identify the subject area and facilitates finding related standards.
ASTM D6812-04a(2019) has the following relationships with other standards: It is inter standard links to ASTM D2700-24, ASTM D2700-23b, ASTM D2700-23a, ASTM D2700-17, ASTM D2700-16a, ASTM D2700-16, ASTM D2700-13b, ASTM D2700-13a, ASTM D2700-13, ASTM D2700-10, ASTM D2700-09e1, ASTM D2700-08, ASTM D2700-07b, ASTM D2700-07a, ASTM D2700-07. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM D6812-04a(2019) is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6812 − 04a (Reapproved 2019)
Standard Practice for
Ground-Based Octane Rating Procedures for Turbocharged/
Supercharged Spark Ignition Aircraft Engines
This standard is issued under the fixed designation D6812; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope (AN 105). No attempt has been made to correlate performance
number of leaded reference fuels to the amine number of
1.1 This practice covers ground-based octane rating proce-
unleaded reference fuels, and none is implied.
dures for turbocharged/supercharged spark ignition aircraft
engines. This practice has been developed to allow the widest
3.1.2 engine octane requirement—one full number greater
range of applicability possible but may not be appropriate for
thanthemaximumnumberthatresultsinknock(graphicknock
all engine types. This practice is specifically directed to
level descriptions can be seen in Annex A1). For example, a
ground-based testing and actual in-flight octane ratings may
test engine knocks on primary reference fuels with 98 and
produce significantly different results.
99 motor octane numbers. The test engine does not knock on a
primary reference fuel with a 100 motor octane number. The
1.2 This standard does not purport to address all of the
maximum motor octane number that results in knock is 99 so
safety concerns, if any, associated with its use. It is the
the motor octane requirement is 100. If a test engine knocks on
responsibility of the user of this standard to establish appro-
a reference fuel with a 3 amine number and does not knock on
priate safety, health, and environmental practices and deter-
a fuel with a 4 amine number, then the engine requirement is a
mine the applicability of regulatory limitations prior to use.
4 amine number.
1.3 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1.3 full rich—condition where the mixture control is at the
ization established in the Decision on Principles for the
full-rich stop position with the fuel flow within the manufac-
Development of International Standards, Guides and Recom-
turer’s recommended settings.
mendations issued by the World Trade Organization Technical
3.1.4 house fuel, n—for engine operation, a fuel that does
Barriers to Trade (TBT) Committee.
not contain metallic additives used for engine warm-up and all
non-octane rating engine operation.
2. Referenced Documents
2.1 ASTM Standards: 3.1.5 knock, n—in an aircraft spark ignition engine, abnor-
mal combustion caused by autoignition of the air/fuel mixture.
D2700 Test Method for Motor Octane Number of Spark-
Ignition Engine Fuel
3.1.6 knock condition, n—for octane rating, where the
knock intensity in any cylinder is light knock or greater, as
3. Terminology
described in Annex A1.
3.1 Definitions:
3.1.7 knock number, n—for octane rating, a numerical
3.1.1 amine number of reference fuels above 100, AN—
quantification of knock intensity.
determined in terms of the weight percent of
3-methylphenylamine in reference grade isooctane (2,2,4- 3.1.8 motor octane number of primary reference fuels from
trimethylpentane). For example, 5 % of 3-methylphenylamine 0 to 100—the volume % of isooctane (equals 100.0) in a blend
in reference grade isooctane has an amine number if 105
with n-heptane (equals 0.0).
3.1.9 no-knock condition, n—for octane rating, where the
knock intensity in all cylinders is less than light knock. Refer
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
to Annex A1 for description of knock intensity.
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.J0.02 on Aviation Piston Engine Fuels.
3.1.10 peak EGT, n—for octane rating, as the mixture is
CurrenteditionapprovedMay1,2019.PublishedJuly2019.Originallyapproved
manuallyleanedfromastaterichofstoichiometric,theexhaust
in 2002. Last previous edition approved in 2014 as D6812 – 04a (2014). DOI:
10.1520/D6812-04AR19.
gas temperature will increase with the removal of excess fuel.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
As the mixture is continually leaned, a peak temperature will
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
be attained, after which continued leaning will result in lower
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. exhaust gas temperatures.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6812 − 04a (2019)
3.1.11 primary reference fuels, n—for octane rating, 4.2 Octane ratings are determined under stable engine
blended fuels of reference grade isooctane and n-heptane. conditions using known PRFs and RFs.
3.1.12 reference fuels above 100, n—for octane rating, 4.3 Knock sensor installation and knock quantification are
described in Annex A1.
blended fuels of reference grade isooctane and
3-methylphenylamine.
5. Significance and Use
3.1.12.1 Discussion—Thispracticedescribesreferencefuels
above 100 MON in terms of isooctane/3-methylphenylamine.
5.1 This practice is used as a basis for determining the
Alternate reference fuels may be used if appropriate, for
minimum ground-based octane requirement of turbocharged/
example, MON in Test Method D2700, Section 8, mixtures of
supercharged aircraft engines by use of PRFs and RFs.
tetraethyl lead and reference grade isooctane. Care should be
5.2 Results from standardized octane ratings will play an
exercised to ensure the reference fuel does not adversely
important role in defining the octane requirement of a given
contaminate the engine and influence the results.
aircraft engine, which can be applied in an effort to determine
3.1.13 stable engine conditions, n—for octane rating, cyl- a fleet requirement.
inder head temperatures change less than 5 °C (9 °F) during a
1 min period. Any changes or minor adjustments to throttle,
6. Apparatus
mixture, or engine conditions mandate restarting the clock for
6.1 Instrumentation:
determining stable conditions.
6.1.1 The engine shall be equipped with the following
3.1.14 takeoff power, n—for octane rating, normal or maxi- instrumentation,whichshallbeaccuratetowithin 62 %offull
scale unless noted otherwise.
mum rated power with the engine speed at maximum rated.
6.1.1.1 Absolute Manifold Pressure Transducer—The loca-
3.1.15 turbocharged/supercharged aircraft engine,
tionoftheMAPsensorshallconformtoenginemanufacturer’s
n—aircraft piston engine that breathes with forced means from
specified location. Manifold pressures shall be measured with
either turbochargers or superchargers.
an accuracy of less than 2.5 mmHg and recorded to ensure
3.2 Acronyms:
proper engine behavior and repeatability.
6.1.1.2 Cooling Air Pressure Transducer, located so as to
3-MPA = 3-methylphenylamine
determine the pressure within the cowling.
AN = amine number
6.1.1.3 Cooling Air Temperature Sensor, located either
CHT = cylinder head temperature
within the cowling or at the entrance to the cowling. If a
EGT = exhaust gas temperature
thermocouple is utilized, it should extend at least a third of the
inHg = inches of mercury
way across the measured area.
MAP = manifold absolute pressure
6.1.1.4 Crankshaft Angle Encoder, if required for knock
MAT = manifold absolute temperature
mmHg = millimetres of mercury
detection. The encoder shall have a sample resolution of at
MON = motor octane number
least 0.4° of crankshaft rotation. The encoder TDC pulse shall
PRF = primary reference fuel
be aligned with the TDC of cylinder number one prior to
psig = pounds per square inch gage
octane rating.
RF = reference fuel above 100
6.1.1.5 Cylinder Head Temperature Sensors, installed in
r/min = revolutions per minute
each cylinder. The sensing locations and types of thermo-
TDC = top dead center
couplesshallconformtotheenginemanufacturer’srecommen-
TIT = turbine inlet temperature
dations. The CHT measurements shall be accurate to within
1 % of full scale.
4. Summary of Practice
6.1.1.6 Exhaust Gas Temperature Sensors, on all cylinders.
Installation shall conform to the manufacturer’s recommended
4.1 A recently overhauled, remanufactured, or new,
location and proper material selection. EGT probes are usually
turbocharged/supercharged aircraft engine is octane rated to
installed within 5 cm (2 in.) of the exhaust stack flange. The
determine the minimum ground-based octane requirement.
EGT probes shall be accurate to within 1 % of full scale.
Minimum octane requirement is defined as one number above
6.1.1.7 Turbine Inlet Temperature Sensors, for each turbine.
thehighestMONorANwhereknockwasdetected.Theengine
is tested at three or more of the worst power points subject to Installation shall conform to the manufacturer’s recommended
location and proper material selection.TheTITprobes shall be
knock behavior while operating under harsh and repeatable
environmental conditions. These points usually involve high accurate to within 1 % of full scale.
6.1.1.8 ManifoldAbsolute Temperature Sensor—Installation
manifold pressures. At the very least, takeoff power, a maxi-
mum continuous or climb power, and a cruise configuration shallconformtothemanufacturer’srecommendedlocationand
proper material selection. The MAT probe shall be accurate to
shallbetested.Takeoffpowerandclimbpoweraretestedunder
full-rich mixture conditions, and cruise power is tested under within 1 % of full scale.
full-rich and lean mixture configurations in 5 % increment 6.1.1.9 Engine Speed Sensor—The dynamometer or propel-
reductions from full-rich fuel flow to peak exhaust gas tem- ler stand shall measure the engine shaft speed to determine
perature. Engine operating temperatures and oil temperatures power development. The engine speed sensor shall be accurate
are kept at maximum allowable limits. to within 65 r⁄min.
D6812 − 04a (2019)
6.1.1.10 Fuel Flow Meter—If the device is calibrated for a 6.3.1 The power absorber shall be capable of providing
particular fuel, then the device shall be recalibrated for each loads for given engine speeds covering the entire range of the
different and subsequent fuel. Data should be reported in mass engine’s operating envelope.
flow units. If applicable, vapor return flow rate shall also be
6.4 Fuel System:
measured to obtain the actual engine fuel consumption rate.
6.4.1 The fuel supply shall have a disposable or cleanable
6.1.1.11 Fuel Pressure Transducers—Locations of fuel
filter. The filter shall allow the proper minimum fuel flow.
pressure transducers shall conform with that recommended by
6.4.2 The fuel selection valve shall be capable of selecting
the engine manufacturer. One transducer is required for the
at least two different fuel sources without the possibility of
metered fuel pressure, if necessary, and another is required for
cross contamination of either source.
the pump outlet pressure. The fuel inlet pressure shall not fall
6.4.3 The fuel supply system shall comply with federal,
below the minimum specified by the engine manufacturer
state,andlocalregulationsrelatedwithfire,hazards,andhealth
during the rating process.
issues.
6.1.1.12 Induction Air Pressure Transducer, located so as to
7. Reagents and Materials
measure the pressure of the induction stream prior to the
throttle plate.
7.1 The MON of PRFs is confirmed by using Test Method
6.1.1.13 Induction Air Temperature Sensor, located so as to
D2700. All PRFs used for the engine octane ratings consist of
measure the temperature of the induction stream prior to the
blends of reference grade isooctane and n-heptane. The PRFs
throttle plate.
will be prepared in increments of one MON. All RFs used for
6.1.1.14 Knock Sensors—The referee method for knock
engine octane rating consist of blends of reference grade
detection is described in AnnexA1.This method requires flush
isooctane and 3-MPA. The reference fuels will be prepared in
mounting piezoelectric transducers. All cylinders shall be
increments of one weight % 3-MPA. (Warning—PRF and RF
monitored. These transducers are connected to charge ampli-
are flammable and the vapors are harmful. Vapors may cause
fiers and shall be capable of measuring combustion pressures
flash fire.)
under a high temperature environment.
7.1.1 Isooctane (2,2,4-trimethylpentane) shall be no less
6.1.1.15 Oil Pressure Transducer—Location of pressure
than 99.75 % by volume pure, contain no more than 0.10 % by
measurement shall conform to the engine manufacturer’s
volume n-heptane, and contain no more than 0.5 mg⁄L
specified location.
(0.002 g⁄U.S. gal) of lead. (Warning—Isooctane is flammable
6.1.1.16 Oil Temperature Sensor—Location of temperature
and its vapor is harmful. Vapors may cause flash fire.)
measurement shall conform to the manufacturer’s specified
7.1.2 n-Heptane shall be no less than 99.75 % by volume
location.
pure, contain no more than 0.10 % by volume isooctane, and
6.1.1.17 Torque Meter—The dynamometer or propeller
contain no more than 0.5 mg⁄L (0.002 g⁄U.S. gal) of lead.
stand shall measure the torque to determine power develop-
(Warning—n-heptane is flammable and its vapor is harmful.
ment. The torque measurement shall be accurate to within 1 %
Vapors may cause flash fire.)
of full scale.
7.1.3 MPA shall be no less than 99 % by volume pure,
6.1.2 The engine should be equipped with the following
contain no more than 0.10 % by volume isooctane, and contain
instrumentation,whichshallbeaccuratetowithin 62 %offull
nomorethan0.5 mg⁄L(0.002 g⁄U.S.gal)oflead.(Warning—
scale unless noted otherwise.
3-MPA is flammable and its vapor is harmful. 3-MPA is toxic
6.1.2.1 Induction Air Flow Meter—Data should be pre-
byinhalation,incontactwithskin,andifswallowed.Dangerof
sented in mass flow units.
cumulative effects. Vapors may cause flash fire.)
6.1.2.2 Induction Air Humidity Sensor, located in either the
7.1.4 Asample shall be taken of each PRF and subjected to
induction air plenum or induction air duct. Data should be
Test Method D2700 for motor octane verification.
presented in absolute, rather than relative, quantities.
7.1.5 A sample shall be taken of each RF and the amine
6.1.2.3 Outside Air Temperature Sensor, capable of measur-
content verified. Ensure reference fuel is a homogenous mix-
ing the ambient dry bulb temperature.
ture under test conditions.
6.2 Data Acquisition:
7.2 Fuels used for operations other than octane rating (for
6.2.1 The instrumentation listed in 6.1 shall be scanned and
example, warm-up) shall not contain metallic additives and
the data recorded at least once every 10 s by an automatic data
should be capable of satisfying the test engine’s octane
acquisition system. The data shall be stored in a universal
requirement under the conditions for the fuel to be used.
format (for example, comma separated values (CSV) for IBM
(Warning—These fuels are flammable and their vapor is
compatible machines) that can be retrieved at a later date.
harmful. Vapors may cause flash fire.)
6.2.2 If in-cylinder pressures are recorded to determine
7.3 Engine oils used for break-in and normal operation shall
knock intensity, the pressure data shall be sampled at a rate of
be oils approved by the engine manufacturer for their respec-
at least 1800 samples per pressure cycle per cylinder for 100
tive operation. (Warning—Lubricating oil is combustible and
consecutive engine cycles.
its vapor is harmful.)
6.3 Power Absorption—The testing is to be performed in a
8. Preparation of Apparatus
ground-based test cell using either a dynamometer or propeller
test stand that shall be capable of maintaining a constant speed 8.1 The history and condition of each test engine should be
to within 65 r⁄min. known and documented by means of engine log books, test run
D6812 − 04a (2019)
sheets, and any other documentation issued by the original controller setting, proper overboost relief valve operation, fuel
equipment manufacturers or repair overhaul shops before any flows, and magneto timing.
octane rating tests are performed.
8.16 A systems check shall be performed, in accordance
with specific aircraft engine manufacturer’s recommendations,
8.2 Only the engine accessories required to operate the
prior to starting the test engine. As a minimum, this shall
engineshallbeinstalledonthetestenginewhenconductingthe
octane ratings. include the following: idle throttle stop, wide-open throttle
throw, mixture cut-off, and full-rich positions. This shall also
8.3 The installation of the proper turbocharger controller,
include fuel and oil system leak inspections.
wastegate actuator, wastegate valve, and overboost relief valve
8.17 A systems check shall be performed after starting the
for the specific engine model and application shall be verified.
test engine. This shall include as a minimum the following
8.4 The installation of the proper intercoolers or
items: oil pressure, magneto ground check in accordance with
aftercoolers, if required, for the specific engine model and
the engine manufacturer’s recommendations, instrumentation
application shall be verified. The intercooler/aftercooler shall
indications within normal ranges, and induction and exhaust
be supplied with proper cooling air pressure and any cabin
system leak inspections.
bleed-airventurisshallbefreetoventtothelocalenvironment.
8.5 The installation of the proper fuel control system,
9. Calibration and Standardization
including the metering unit, pump, distribution manifold,
9.1 The engine shall be set up in accordance with the
nozzles, and fuel lines for the specific engine model and
manufacturer’s specifications. The ignition timing shall be set
application shall be verified. This should also include ensuring
within the engine manufacturer’s specified allowable range for
equal fuel flow distribution through all nozzles and associated
that engine make and model.
lines.
9.2 The fuel flows shall be set within 62 % of the recom-
8.6 The exhaust system employed shall be free to discharge
mended fuel flow (or 65 % of the recommended pressure
into the surrounding environment without extended plumbing,
when appropriate).
plenums, or mufflers, which may induce an improper pressure
9.3 Proper waste gate controller operation shall be verified,
balance across cylinders.
which must include ensuring that maximum rated power is
8.7 Propersparkplugsmatchingtherequiredheatrangeand
attained at full throttle and maximum rated speed without
depth for the engine model to be tested shall be verified. The
encroaching the limiting manifold pressure.
plugs should be cleaned and gapped prior to octane rating. The
9.4 Instrumentation shall be calibrated and checked to
integrity of the spark plug ignition leads shall also be verified.
ensure accuracy to within 62 % of full scale, unless noted
8.8 Crankcase vents shall be free to vent to the local
otherwise.
environment.
10. Procedure
8.9 If the test engine’s fuel system is designed to recirculate
fuel to the tank, provisions shall be made to ensure that no fuel
10.1 Engine Break-In:
is recirculated to the containers with the PRFs or RFs.
10.1.1 If the test engine is new, remanufactured, or recently
overhauled, break it in prior to conducting initial octane
8.10 The idle and full-rich mixture settings shall be set, and
ratings. Conduct the break-in in accordance with the engine
the resulting fuel flow rates verified to be within the engine
manufacturer’s recommendations. Conduct the break-in with a
manufacturer’s specifications.
fuel that does not contain metallic additives.
8.11 The idle stop and full throttle throw positions shall be
10.1.2 Start the engine, and follow the engine manufactur-
set in accordance with the engine manufacturer’s recommen-
er’s warm-up procedures. Perform a magneto check in accor-
dations.
dance with the engine manufacturer’s recommendation.
10.1.3 Operate the engine at the manufacturer’s recom-
8.12 It shall be verified that the mass moment of inertia of
mended power settings, and record the oil consumption until
the flywheel, couplers, driveshaft, and spacers and the drive-
either oil consumption is stabilized or 10 h of engine operation
shaft stiffness are sufficient to prevent operational resonance
is attained. Oil consumption stabilization should conform to
and possible engine failure.
the engine manufacturer’s recommendation.
8.13 Before any octane rating, and after all break-in and
10.1.4 During the engine break
...
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