not only for testing an engine in a specific facility (i.e., the OEM’s baseline test facility), but also for testing a specific engine test hardware configuration (i.e., the OEM’s baseline test hardware configuration).
(1) For testing at the reference facility, the FAA recommends that the engine test hardware configuration be the same as:
(a) The hardware to be used during correlation testing at the applicant’s facility;
(b) The hardware to be used for future in-service acceptance testing at the applicant’s facility; and
(c) The OEM’s baseline test hardware configuration.
(2) However, the configurations that were used during testing at the baseline, reference, and applicant’s facilities may be different. These differences should be evaluated for their impact on correlation.
401. CORRELATION PROCEDURES.
a. Procedure Overview. The following activities are a general overview of the step-by-step correlation process. Following this overview, details of these activities are discussed in paragraphs 401b through 401d.
(1) Identify a correlation engine. The engine must:
(a) Develop minimum rated thrust.
(b) Exhibit stable performance.
(2) Calibrate the applicant’s test cell instruments and perform an end-to-end check of systems.
(3) Notify the respective FSDO and verify FAA-approval and the correlation status of the reference facility with respect to the baseline facility.
(4) Perform a shakedown engine run at applicant’s test cell. The run will:
(a) Verify instrumentation accuracy.
(b) Check out all other systems.
(5) Perform an engine test at the reference facility using the correlation engine.
(6) Notify the respective FSDO.
NOTE: The FAA recommends that reference testing be performed before testing at the applicant’s facility. However, this process may be performed in reverse, if necessary.
(7) Perform the applicant’s facility test cell correlation.
Page 22 Par 400
(a) Notify the respective FSDO.
(b) Perform an 8- to 15-data point engine run.
(c) Perform engine run in the same sequence and direction of approach to the test points (i.e., acceleration versus deceleration) as that performed at the reference facility.
(d) Shut down the engine in preparation for an engine and facility repeatability check.
(e) Repeat the engine test using the same procedure.
(8) Perform a retest at the reference facility (recommended, but optional).
(9) Perform data analysis.
(a) Apply corrections to measured data for common reference (e.g., standard day).
Graphically plot the data and draw a smooth characteristic line through the data for each plot. Regression analysis of the data is also an acceptable means of determining the characteristic line.
(b) Analyze the data for measurement error (e.g., perform data validation).
(c) Analyze the data for performance shift.
(d) Determine the cell correlation factor(s) and apply to (usually) corrected common reference data. Plot the adjusted, corrected data.
(e) Perform an acceptance test in accordance with the OEM’s overhaul manual to ensure the applicant’s test cell is capable of being utilized for satisfactory in-service acceptance testing.
(10) Develop documentation.
(a) Write the Correlation Report, as described in paragraph 402, to document details for the entire correlation exercise.
(b) Develop and document procedures for operating and maintaining the test cell and ensuring satisfactory maintenance of the test cell correlation status (i.e., develop a facility operations manual).
b. Pre-correlation Procedure. The following activities should be performed before correlation testing:
(1) Determine correlation test procedures in accordance with the OEM’s correlation test requirements or recommendations.
(2) Instrument the engine in accordance with the OEM’s recommendations.
(3) Obtain fuel samples at both facilities, before or during correlation testing, and determine specific gravity and LHV.
(4) Identify and record appropriate engine test hardware configuration(s) to be utilized at the reference and applicant’s facilities (see paragraphs 305j and 400b). Obtain measurements of the Par 401 Page 23
bellmouth, fan exhaust nozzle, and primary exhaust nozzle areas to be used for reference and applicant facility testing. These measurements should be compared and may be useful when evaluating the correlation. Additionally, when specified by the OEM, bellmouth area measurement may be required for calculating airflow.
(5) Identify an acceptable correlation engine. A new, used, or rebuilt engine can be used as long as it demonstrates at least minimum takeoff thrust and maintains stable performance across the corrected thrust range from idle to takeoff. The engine’s ability to reach rated takeoff thrust without overtemperaturing or overspeeding is important. It allows engine testing to be performed without safety or performance deterioration concerns. The use of an engine experiencing a gradual run-to-run variation in performance, such as a gradual performance deterioration, could result in a nonstandard and needlessly complex correlation evaluation.
(6) Immediately before the correlation run, calibrate the applicant’s test cell instrumentation and engine instrumentation to the selected standard. Also, perform an end-to-end check of the applicant’s facility measurement systems (see paragraph 301).
(7) Notify the respective FSDO:
(a) Early in the planning process so that all requirements are identified, and
(b) Prior to testing at both the reference and the applicant’s facility, should the FAA elect to witness the test.
NOTE: If applicable, obtain proof that the reference facility is FAA-approved and traceable to the OEM’s baseline facility.
(8) Perform a full power shakedown run prior to the correlation run at the applicant’s facility.
The entire facility, including the test cell, data system, and calculation procedures, should be thoroughly tested. This may be performed with an engine other than the correlation engine. This is also another opportunity to investigate and eliminate facility measurement system problems, since a check of the entire system operating together may not have been previously performed.
c. Correlation Procedure. The test procedure used at the applicant’s facility should be the same in all aspects as the procedure conducted at the reference facility. This includes:
/g183/g32 The number of data points acquired /g183/g32 Thrust levels /g183/g32 Stabilization time /g183/g32 Sequence /g183/g32 Direction of approach to the test points /g183/g32 The parameters recorded
Page 24 Par 401
(1) Once the facility to be correlated (i.e., applicant’s facility) is thoroughly tested via the shakedown run, the formal correlation process can begin. In most cases, the correlation engine is first tested in the reference test facility. A correlation engine test usually includes 8 to 15 data points distributed across the thrust range.
NOTE: Under certain conditions, fewer data points could be acceptable.
(2) Care should be taken to fully stabilize the engine thermally and dynamically before data acquisition is initiated. The stabilization time should be recorded so that it can be duplicated during testing at the applicant’s facility.
(3) Weather conditions should be recorded at both facilities at the time of test, as well as any weather changes occurring during the test. It is desirable to minimize the ambient temperature and humidity differences between the two facilities. Any preestablished climatic envelopes are to be observed for satisfactory testing.
(4) To ensure consistent and repeatable engine testing, the proposed test procedure should include a listing of parameters to be measured and the measurement precision and range. The following parameters should be recorded:
/g183/g32 Engine fuel flow
/g183/g32 Engine thrust
/g183/g32 Engine rotor speeds
/g183/g32 Engine airflows
/g183/g32 Engine pressures and temperatures
/g183/g32 Engine inlet conditions
/g183/g32 Test cell temperatures and pressures
/g183/g32 Test cell inlet airflow
/g183/g32 Engine control systems and variable geometry
/g183/g32 Barometric pressure
/g183/g32 Ambient humidity
NOTE: Sufficient data must be obtained to meet acceptance test procedures specified by the OEM. Secondary parameters used in the derivation of any of the above items must also be measured and recorded. In addition, redundant instrumentation can be useful for data verification and troubleshooting purposes.
(5) During the engine test at the reference test facility, the sequence and direction of approach to the test points performed (i.e., acceleration or deceleration) should be recorded. The data points taken at Par 401 Page 25
the facility to be correlated should also be collected in the same sequence and approach to eliminate performance variability due to control system hysteresis.
(6) Once the engine test at the reference facility is complete, the correlation engine should be immediately preserved and shipped to the applicant’s facility for correlation testing. This will minimize engine performance deterioration due to additional operation.
(7) Following the initial correlation engine run at the applicant’s facility, the engine should be shut down for a minimum of several hours to reach a cool engine state. Time periods for cooling can vary; refer to the OEM’s instructions. After the shutdown period, the engine test should be repeated for an engine and facility repeatability check. The repeatability check is intended to demonstrate stable engine performance and engine run-to-run repeatability of the data measurement, acquisition, and reduction systems.
(8) Ideally, the test cell correlation should include engine runs at the reference facility, at the applicant’s facility, and again at the reference facility (i.e., A-B-A). If the engine is routinely used for correlation testing, a retest at the reference facility may not be necessary if correlation engine data from several previous runs are consistent.
(9) Following the performance correlation runs, the correlation engine or another suitable engine should be tested at the applicant’s facility using the overhaul manual in-service acceptance procedures.
This will ensure that the applicant’s facility is capable of being utilized for satisfactory engine acceptance testing. This should not be performed until after all correlation testing is complete and the correlation data has been reduced, analyzed, and accepted.
(10) Data obtained during testing at the reference and applicant’s facilities must be recorded in a manual or automatic log sheet at the time of test. The FAA recommends that copies of these records be provided to the FAA representative witnessing the testing (if applicable) immediately upon conclusion of testing.
d. Post-correlation Procedure. The following paragraphs identify the post-correlation steps. The FAA recommends that the correlation engine be carefully stored until the correlation analysis is complete, in case further testing is necessary.
(1) Following completion of correlation testing, the data must be reduced (i.e., calculations must be performed). Paragraph 305b describes the process of correcting or normalizing the measured data to sea level, static, standard day conditions. The corrected data is typically graphically displayed, and a smooth characteristic curve is drawn through the data.
(2) Paragraph 401e below gives a detailed description of the post-test correlation data analysis of the plotted data. The OEM’s manuals and reports should also be referenced for a more thorough analysis description relative to a specific engine model.
e. Correlation Data Analysis. Once engine tests at both facilities are complete (all data has been edited, averaged, corrected, and plotted graphically) and a smooth characteristic line has been drawn through the data for each performance plot, the data must be analyzed. Data analysis is an engineering function and requires specialized knowledge. It is typically performed by the applicant, OEM, or other qualified personnel. It should include the following three steps: data validation with instrumentation error isolation, performance shift determination, and correlation factor determination. Each of these three elements should be isolated independently in the order given. If data errors or real performance shifts are not recognized, their respective effects on performance might be erroneously lumped into the third item, Page 26 Par 401
the correlation factor. This could result in possible inconsistencies during future in-service acceptance testing of engines at the applicant’s facility.
(1) Data Validation. Data validation analysis is the process of determining the acceptability of the measured, corrected data. The process of data validation requires specialized knowledge of standardized methods (e.g., cross-plotting of various parameters, error and cycle derivatives, influence coefficients) and general knowledge (preferably engine model specific) of aerodynamic/thermodynamic cycle effects. The following paragraphs provide some general methods of determining data validity by analyzing the characteristic plots.
(a) Plots should be constructed with the reference and applicant’s facility data plotted together for comparative analysis. Sample correlation plots are given in Appendix 3. Generally, each corrected parameter is plotted separately on the y-axis, while either the corrected thrust, engine pressure ratio (EPR), or corrected rotor speed is plotted on the x-axis of each plot. Utilizing a practice of plotting the same ordinate (y-axis) values against another parameter, such as corrected rotor speed, is a useful way of independently judging data validity.
(b) Plotting each pressure ratio against corrected rotor speed can be useful in determining possible pressure mismeasurements, though care should be taken to verify that there is not a real performance shift.
(c) Once a parameter is determined to have an unacceptable error, every effort should be made to eliminate that error. Extensive troubleshooting of the measurement system should be performed.
Not only should all gauges, signal conditioners, instrumentation lines, pressure probes, thermocouples, and rakes be carefully examined in an end-to-end check, but the data acquisition system and correction methodology should also be checked. Once the measurement or calculation error has been found and corrective action taken, a determination must be made as to whether another correlation run is necessary.
Some errors, such as a calculation error or gauge scalar error, may be corrected without having to conduct another engine run.
(2) Performance Shift Determination.
(a) Once unacceptable measurement errors have been eliminated or compensated for, an assessment must be made as to whether the engine’s performance remained unchanged between the reference and applicant’s facilities. This can be done by cross-plotting the corrected data. If a shift in performance is not recognized, an incorrect correlation factor could be developed and applied to all future engine test data, resulting in repeated errors in assessing subsequent engine test data.
(b) If there is an apparent performance difference between the two test runs (i.e., reference facility and applicant’s facility) that cannot be accounted for by expected facility and/or engine test configuration influences, further testing may be necessary. Follow-on actions will be determined from the results obtained. Paragraph 303 describes factors that influence correlation.
NOTE: Facility configuration and engine or facility instrumentation differences can be difficult to uncover and quantify.
(3) Correlation Factor Determination.
(a) Correlation factor determination should be done only after the first two parts of the correlation analysis (data validation and performance shift determination) have been satisfactorily completed.
Par 401 Page 27
NOTE: Some OEMs specify run-to-run parameter tolerances for engine correlation testing. If the OEM’s baseline facility was used for reference testing and the data obtained at the two facilities was within the specified tolerances, then the applicant’s facility should be deemed correlated and would not require a correlation factor. See paragraphs 400a and 401e(3)(d) for facilities other than the baseline facility that are used for reference testing.
(b) Turbofan and turbojet engines with a choked core exhaust nozzle generally require that a correlation factor be applied only to thrust. However, engines with unchoked core exhaust nozzles may require additional correlation factors (e.g., exhaust gas temperature (EGT), fuel flow, rotor speeds).
(c) OEM’s manuals should be referenced for correlation factor determination and application methodology. Generally, correlation factors are applied as a curve input (algebraic difference) or a scalar (multiplier, usually greater than unity). They also usually represent the differences in corrected data obtained during testing at the reference and applicant’s facilities. Correlation factors are usually applied to corrected, not raw, data. For example, when a correlation factor is developed for a choked engine, the x-axis may represent corrected thrust, corrected rotor speed, or EPR, and the y-axis would be used for plotting the appropriate correlation factor.
(d) When using a one-away facility for reference testing, caution should be used in determining correlation factors for the applicant’s facility. The one-away facility may not have exactly repeated the OEM’s baseline facility performance curve characteristics. As long as the one-away’s characteristics were within the manufacturer’s acceptable run-to-run tolerance, then a correlation factor applied to the one-away facility would not have been necessary. When a third facility’s (or applicant’s) characteristics are compared to the one-away’s performance characteristics and found to be within the same manufacturer’s acceptable run-to-run tolerance, there exists a potential for compounding the acceptable tolerance. This results in an error greater than the allowed tolerance relative to the baseline facility. The potential compounded tolerance error can be averted by taking into account the characteristic differences between the one-away and baseline facilities when evaluating the correlation factor for the applicant’s facility. The possibility of compounding tolerance errors becomes greater the further the reference facility is from the baseline facility, with respect to correlation. Paragraph 400a provides additional information on this.
NOTE: As previously discussed, every effort must be made to completely eliminate or compensate for all measurement errors during data analysis. Once this is accomplished, attributing the remaining known minor, but elusive, differences to the correlation factor is generally acceptable. For example, there might be a 5-degree measured and corrected EGT difference between the applicant’s facility and the reference facility. The applicant’s facility would then apply the 5 degree difference to all future measured and corrected EGT data. This methodology should be applied only when the parameter has a constant error over the entire engine operating range and is constant from test to test.
NOTE: If the characteristic curve shapes for a particular parameter measured at the two facilities are divergent (not parallel), then this error should not be applied as a correlation factor. The error would result in the cell producing erroneously variable data during future acceptance testing of engines at the applicant’s facility.
In this case, a continued effort should be made to determine the cause and eliminate the error.
Page 28 Par 401
402. CORRELATION REPORT. After completion of the cell correlation program, a final report should be developed to document information necessary for subsequent engine performance and acceptance testing (e.g., test cell and engine configuration, correlation factors, performance calculations used). The final report is also useful to document a comparison of the applicant’s data to the reference data and to document any recommendations. The following should be included in the final Correlation Report.
a. A statement regarding the purpose of the correlation, including any relevant background and historical information.
b. A description of:
/g183/g32 The test cell geometry, preferably including sketches and engineering drawings /g183/g32 Correlation engine configuration, including its serial number and the bellmouth, fan exhaust nozzle, and primary exhaust nozzle areas /g183/g32 A listing of dress kit part numbers and serial numbers where possible /g183/g32 Results of the fuel sample analyses /g183/g32 Significant changes made to the test cell, dress kit, and engine since the last correlation /g183/g32 Significant changes made during the current correlation testing and the reasons for making such changes
NOTE: Detailed photographs are also useful for evaluating whether or not changes have occurred to the facility.
c. The test and performance calculation procedures used, including, where applicable, complete identification of any software programs used.
d. The analysis of the applicant’s performance data compared with the reference facility data, including the measured and corrected data and the curves for both facilities. This should also include a comparison of data between the reference and baseline facilities if the applicant used a reference facility that was not the OEM’s baseline facility.
e. The derived cell correlation factors and how they should be applied.
f. Recommendations for adopting any improvements in engine performance testing (e.g., in-service acceptance testing) that do not affect the validity of the current correlation results. This may include changes that would significantly improve the quality and dependability of future performance data, such as specific operator training, addressing deficiencies in instrument calibration procedures, instrumentation, and data documentation.
g. Conclusions, including any pertinent documentation (i.e., correspondence from the OEM, qualified consultants, DERs), that the applicant’s test cell is acceptable for specific engine model inservice acceptance testing based on the correlation analysis.
Par 402 Page 29
h. If applicable, the final report should include a statement indicating that it supersedes the previous report. The report should be made part of the facility operations manual or other similar documents, as discussed in paragraph 404 below.
403. MAINTAINING CORRELATION. Once a test cell correlation has been established, it must be satisfactorily maintained. Maintaining correlation relies on recognizing elements that could adversely affect the correlation. Care must be taken to control repairs and/or modifications to the test cell and/or engine test hardware (e.g., test cell inlet and exhaust airflow, thrust stand, measurement systems, data reduction software and procedures, configuration of the engines to be tested). Changes in any of these areas may affect correlation validity. This section provides information on the quality control aspects of test cell testing; how correlation can be satisfactorily maintained; items that may affect satisfactory correlation status; and good facility maintenance practices.
a. Configuration Control. Routine acceptance testing of engines following correlation should be accomplished utilizing an engine test hardware configuration that is consistent with that used for the correlation run, unless otherwise checked out as described in paragraph 305j.
(1) It is extremely important that any items affecting airflow in or around the engine or in the test cell be of the same configuration as that used for correlation testing (e.g., the bellmouth, nacelle, substitute fan reverser, bifurcated ducts, core cowl doors, applicable exhaust nozzle(s), and plugs).
Engine components projecting into the airflow, such as generators or hydraulic pumps, should also be of the same configuration. Each piece of critical test hardware must be serialized or otherwise identified. In the event that multiple sets of test hardware are used, back-to-back testing with each specific hardware configuration should be performed. Depending on the results, a separate correlation for each configuration may be required. Paragraph 403c(3) below describes back-to-back testing.
(2) Engine models using ancillary equipment projecting into the cell airflow should be identified at the time of correlation. If it is intended (or just possible) to run the engine with or without such equipment, correlation runs of the engine with and without the equipment should be performed.
b. Correlation Monitoring and Maintenance. The following paragraphs give several ways to maintain correlation. If an operator does not utilize any of the following recommended trending, periodic checks, and recorrelation testing, then it is recommended that the facility institute a process of recorrelation every seven years. This recommendation is based on reference 1-2a(1) of Appendix 1.
NOTE: If the correlation of the applicant’s facility was conducted using a reference facility other than the OEM’s baseline facility (e.g., a one-away facility), using one or more of the following methods to ensure that the correlation is maintained is important.
(1) Trending is the practice of recording and plotting engine performance parameters of satisfactory acceptance engine tests. The key parameters are plotted against results obtained from similar engine tests. These results are examined for signs of performance data shifts above and beyond normal data scatter. Trending can increase confidence in the correlation validity or can alert facilities’ organizations to a possible test anomaly or an unacceptable drift of recorded performance data over an extended period of time. To be interpreted correctly, analysis of trend data must be done with knowledge of any engine internal hardware modifications that result in a change in engine performance. In these cases, evidence of a significant performance data trend would not necessarily indicate a loss of correlation.
Page 30 Par 402
(2) Re-calibration of instrumentation in a test cell must be accomplished on a regular schedule to maintain the required measurement accuracy. A system of recording and forecasting instrumentation calibration requirements should be established. As with the case of initial correlation, all instrumentation calibrations should be performed using primary or secondary standards traceable to an accepted known standard. Paragraph 301 provides additional information on instrument calibration.
(3) Continued periodic checks provide additional confidence in the current validity of the test cell correlation. Periodic check opportunities could include running an engine in another correlated test cell and checking it against run data from the test cell under evaluation or running an engine dedicated for periodic checks in the test cell under evaluation. Data error stackup should be considered in the interpretation of test results. Maximum time intervals for recorrelation may be recommended by the OEM. Additional correlations may be made on an “as needed” basis. For instance, where a test cell has undergone significant changes, recorrelation will be required. This is further discussed in paragraph 403(c).
c. Maintenance of Test Cell Correlation Following Repairs or Modifications. To monitor changes to the test cell and its systems, adequate recordkeeping of events is necessary. Records may take the form of written logs, photographs, video, and other accurate documentation media.
(1) The following are examples of items where modifications can have significant facility effects:
/g183/g32 Engine test hardware (e.g., dress kit)
/g183/g32 Facility inlet and exhaust
/g183/g32 Data acquisition: manual to automated acquisition, manual to automated reduction (calculation), and scanning, averaging, and editing
/g183/g32 Instrumentation: type, quantity, and location
/g183/g32 Thrust stand
/g183/g32 Sizable equipment changes within the cell
(2) Repairs to test cell equipment should be evaluated for possible impact on engine performance or performance measurement.
(3) Back-to-back testing is the method most frequently used to determine the effects on engine performance of a repair or modification made to either the test cell or engine test hardware. This test is accomplished by using an engine with known stable performance that is capable of operating over the engine’s entire thrust range. Before any repair or modification in the cell or to the engine test hardware is made that may affect correlation, the engine must be run through the first stage of a back-to-back test.
The test procedure may be defined by the OEM or developed by the applicant. The schedule should include all power points that would be recorded during routine acceptance testing and may include other data points. It is good practice to perform this initial test twice, at a minimum, before any repair or modification. The data from these runs should be carefully examined to determine if engine performance is stable. When stable engine performance has been established, the engine should be stored for later testing. After the repair and/or modification has been accomplished and documented, the same engine should be tested in the cell to the same schedule as initially tested. Data from these runs should be Par 403 Page 31
analyzed to determine the effect, if any, the repair and/or modification had on engine performance and, thus, any cell correlation factor(s).
(4) Total cell airflow monitoring is a useful technique for determining whether test cell changes have affected engine performance. The measurement of the airflow, pressure, and temperature distribution in front of and around the engine under test may be determined by using a hot wire anemometer, pitot-static array, or a similar system. The data obtained during the test should be compared with that obtained during the last correlation.
(5) If any of the measured parameters that have been corrected and plotted on the characteristic performance curves have changed relative to the initial test, it should be determined whether the change(s) makes sense relative to the repair and/or modification. The parameters that have changed, the magnitude of change in their values, and the direction of their change should be considered during this evaluation. If a change to any of the parameters cannot be reconciled, an analysis of the data should be performed to determine if there is an error in the data measurement (i.e., data validation). If data validation analysis is unsuccessful in reconciling parameter differences, a recorrelation should be performed. Further, if it is determined that a new correlation factor and/or a significant change to an existing correlation factor is necessary following reconciliation of all measured parameter differences, the FAA recommends that a recorrelation be performed.
d. Test Cell Equipment and Facility Maintenance. Regular inspection and maintenance of all parts of the test cell and engine dress kit are highly recommended. A maintenance schedule should be established and followed. Maintenance should include:
/g183/g32 Instrument calibration
/g183/g32 Inspection or checks of measurement systems
/g183/g32 Inspection and repair of intake and exhaust systems (e.g., splitter panels, augmentor tube)
/g183/g32 Lubrication of moving parts
/g183/g32 Activation of valves and limit switches
/g183/g32 Inspection and repair of cell structural surfaces
/g183/g32 Intake screen debris removal
/g183/g32 Exhaust cleaning
/g183/g32 Engine intake and exhaust nozzle inspections
/g183/g32 Oil system flushing
/g183/g32 Emergency system testing
/g183/g32 Personnel training
NOTE: These practices can be characterized as good housekeeping and preventive maintenance.
Page 32 Par 403
404. FACILITY OPERATIONS MANUAL. An FAA-approved facility performing in-service engine acceptance testing should have in place a facility operations manual, or other document(s) acceptable to the FAA, that defines a specific set of requirements for maintaining and operating the test cell and for maintaining a satisfactory correlation status. These requirements should include, but are not limited to, the following:
a. Recordkeeping. As a minimum, facility records must conform to the requirements of part 145.
The current edition of FAA AC 145-3, Guide for Developing and Evaluating Repair Station Inspection Procedures Manuals, prescribes recommended practices for recordkeeping.
b. Test Cell Operations. The engine make, model, and configuration for each operation in the test cell should be documented. Provisions should be made for recording the dress kit hardware and serial numbers, as applicable. This dress kit should be the same configuration as the one used for correlation, unless the dress kit has otherwise been checked out as described in paragraph 305j. Facility operating procedures should be developed. The procedures should include operations under normal and emergency conditions (such as fire, engine failure, compressor stalls, etc). In addition, procedures should be developed in the event of engine operational warnings, as indicated on the test cell console, including the disposition of these warnings.
c. Facility Maintenance Procedures. A procedure must be established to record all repairs and modifications to the facility, especially those that may affect test cell operation and correlation status.
This procedure should specify that the respective FSDO be notified of any facility modifications that may affect the correlation status. Also, a procedure should be developed to ensure that facility maintenance and instrument calibration is regularly scheduled and performed and that pertinent information is recorded.
d. Quality Control Procedures. The facility must have provisions in place to maintain a satisfactory correlation status. Various options for correlation monitoring and maintenance are discussed in paragraph 403. In addition, the facility should have a system to maintain, in a current status, the following:
(1) OEM’s documents, such as a facility planning manual, if published;
(2) Service engine acceptance test procedures taken from the OEM’s Instructions for Continued Airworthiness, and pertinent specifications and Technical Orders for each model being tested;
(3) Correlation reports; and
(4) Other pertinent documents.
NOTE: The provisions and systems discussed above should be defined in a facility operations manual or other documents(s) acceptable to the FAA.
Par 404 Page 33