Appendix 2 refers to range as the “change in range”, or by the symbol ΔR. For example, if given a range [] 21 R,R , then the total change in range is:
12 RRR −=Δ
j. Resolution. An EU representation of the least significant bit (LSB) in the word structure.
This LSB is important when calculating the value of a digital binary type parameter. If the parameter resolution is not identified in the input information, then the resolution must be determined. Given the number of bits and the range in EU, a linear resolution can be calculated by using the following equation:
Where, ΔR is the total change in range, derived in paragraph 2i, measured in EU, and NB is number of bits, the parameter resolution is denoted by:
() NB2 Rres Δ= NOTE: It is important to document an appropriate number of decimal places (or express the resolution as a fraction) to avoid the introduction and propagation of error.
3. REVERSE DFDR DATA CO RRELATION PROCEDURE A. This paragraph describes the first procedure that DFDR test engineers may follow in conjunction with Procedures B and C to develop an acceptable baseline correlation document, when no document exists.
a. Requirements. This paragraph identifies the required data items needed to begin reverse engineering the DFDR data correlation document.
(1) Procedure A requires a search for and an identification of parameter specific information. ICDs, PDDs, and conversion documents are resources that contain information to perform Procedure A. The required minimum inputs to conduct Procedure A are conversion algorithms (decimal units to EU), ranges (EU), and either resolutions or number of bits in the digital word.
(2) The following example illustrates how to find ΔR when given a parameter’s range. If the range of the roll attitude parameter is –180˚ to +180˚, then the total change in range, ΔR, is:
( ) °=°−−°+=Δ 360180180R The parameter resolution in EU may not be available from the resource documents. If the parameter resolution is not identified in the input information, then the resolution must be determined from the number of bits. If roll attitude is the parameter of interest, then the following is an example of how to solve for a linear resolution. Given the number of bits is 12 and the change in range is given in the previous example, the linear resolution can be solved by using the following equation:
Appendix 2 () 0879.0res 4096 360 2 Rres NB = =Δ=
(3) A conversion document contains the algorithms, tables, or codes to convert applicable parameters from EU to decimal units. This information is critical in completion of reverse data correlation. Depending upon the ARINC Specification 429 data word structure of a specific parameter, an algorithm or conversion equation, a look-up table, or a conversion code is required to perform the conversion. An example of a binary formatted data conversion algorithm is below.
In this example roll angle is measured in degrees, such that:
U.E.inanglerollthedenoteswhere 931399390.00465716 602082600.11550433249482610.00000035248068910.00000014 000031670.00000000000015150.00000000 unitDecimal 23 45 ϕ ϕϕϕ ϕϕ +×+×+× −×+×=
(4) Now that the required inputs for Procedure A are gathered, paragraph 3b lays out the foundation to derive baseline correlation data.
b. Process. This paragraph outlines the steps to create the baseline of manufacturer system-specific data.
(1) A baseline must be established that translates a 1 to 1 correlation between decimal units and EU for the full range of every parameter. For each parameter, use the conversion algorithm or other method to calculate the full range in decimal units.
(2) Begin plotting the lowest value in the full range against the respected decimal unit.
Then, increment the resolution to obtain decimal unit values for all NB2 range values. All NB2 values are plotted with an uncertainty of half the resolution, 2res± .
c. Data Application/Desired Output. This paragraph identifies the required data to be produced by following Procedure A.
(1) In Procedure A, DFDR parameter information was gathered to convert the full range from EU to decimal units. The conversion algorithm or other method was utilized to create a baseline of DFDR system data. The baseline conversion data must be stored or displayed in some documented fashion.
(2) If applicable, the parameter’s resolution must be converted from EU to decimal units.
In the case of a parameter with a non-linear resolution, an EU to decimal conversion must be considered from decimal count to decimal count. Section 5 discusses the significance and applicability of the parameter’s resolution to this appendix.
(3) A baseline plot for an identified parameter.
Appendix 2
(a) One example of displaying the baseline data is by plotting individual data points.
One implementation would be to plot decimal units as a function of EU, with increments of the resolution determined in paragraph 3c. The following linear baseline plot, Figure 2-1, is a continuation of the roll attitude example from previous paragraphs. Figure 2-2 shows an example of a nonlinear baseline plot.
(b) If a baseline plot cannot be established with reasonable accuracy, then ground station tools may be required to perform an accurate baseline plot of intermediate converted values. For example, some DFDRS implementations process synchro signals which increases both the complexity and accuracy of a decimal unit to EU conversion.
FIGURE 2-1. EXAMPLE LINEAR BASELINE PLOT OF EU TO DECIMAL UNITS Roll Attitude Parameter Conversion Data -180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180 -20 -16 -12 -8 -4 0 4 8 12 16 20 Decimal Units Engineering Units
Appendix 2 FIGURE 2-2. EXAMPLE NON-LINEAR BASELINE PLOT OF EU TO DECIMAL UNITS Electric Coarse Altitude Parameter Conversion Data -10000 0 10000 20000 30000 40000 50000 -200 0 200 400 600 800 1000 1200 1400 1600 Decimal Units Engineering Units
(4) Once data storage or display is complete, this information is used in paragraph 5 as a baseline to determine compliance with the CFR.
4. REVERSE DFDR DATA CO RRELATION PROCEDURE B. This paragraph identifies the data items needed to complete the required aircraft test of DFDR data reverse correlation.
Accomplishing this procedure depends on the availability of the aircraft to be tested.
a. Requirements. Procedure B requires the data ranges for each parameter, a DFDRS-equipped aircraft, and all equipment necessary to test the onboard DFDRS. The decimal unit to EU conversion algorithm or method is required. The operator or test engineer must have a predetermined list of data points to test for each parameter through the static and full dynamic ranges. This list of data points must be in EU and correlate to one of the 2NB data points obtained in Procedure A. It is also useful to have a tool capable of converting conventional forms of digital outputs into decimal units.
NOTE: There are cases where certain types of parameters cannot be tested in the airplane environment. These parameters can only be stimulated in a lab environment and applied to the airplane through analysis. For example, a computer failure can be simulated in the lab environment and the software paths of the acquisition unit can be confirmed. This testing can be applied to the airplane where it is rare that one can force working equipment to fail for test purposes. Credit should be given that source systems that provide data to the acquisition unit had these functions tested during their certification.
Appendix 2
b. Process. The test engineer evaluates the DFDRS recorded data based on the data ranges for each parameter.
(1) The test engineer must use the predetermined list of data points to be recorded as identified in paragraph 3.
(2) By controlling the aircraft input, the conventional form of the digital output is to be recorded.
(3) The conventional form of the digital output must be converted into decimal units. A capable tool (i.e., calculator, computer application, etc.) makes this conversion easier.
c. Data Application/Desired Output. This paragraph identifies the required data to be produced by following Procedure B.
(1) The parameter’s static and full dynamic ranges and recorded outputs should be stored or displayed. Use a method similar or comparable to that used in Procedure A (i.e., plot EU as a function of decimal units).
(2) Once data storage or display is complete, this information is used in paragraph 5 to compare against the baseline to determine compliance with the CFR.
5. REVERSE DFDR DATA CO RRELATION PROCEDURE C. This paragraph outlines the process to determine compliance with the CFR. It defines a comparative assessment between actual aircraft measured data and manufacturer system-specific data. If regulatory compliance is not determined, then the operator must choose to either repair, recorrelate, or replace the noncompliant system. Procedures A and B must be accomplished before completing Procedure C.
a. Requirements. This paragraph identifies the required data items needed to accomplish DFDR data reverse correlation. The recorded conversion data from Procedures A and B are required to begin Procedure C. If applicable, the parameter’s resolution from Procedure A is also required and is critical in determining an acceptable parameter correlation.
(1) Procedure A contributes manufacturer-specific system conversion and parameter information. For each parameter, a baseline with digital tolerances was established. If applicable, an EU to decimal unit representation of expected DFDR system operational performance was created. In the following discussion, data obtained from Procedure A will be referred to as “expected” data.
(2) Procedure B contributes aircraft-specific DFDR data from testing the static and full dynamic range of each parameter. The number of data points recorded is discretionary, greater numbers of data points increase the probability of the parameter being in compliance. The actual data stored in an aircraft’s DFDR needs to be verified through a comparative assessment with the data from Procedure A. In the following discussion, data obtained from Procedure B will be referred to as “measured” data.
Appendix 2
b. Process. This paragraph outlines the steps to complete the analysis and to determine compliance.
(1) Once the data from Procedure A and B are present, a comparative assessment is required. This analysis relates an aircraft-specific DFDR operational performance to the expected DFDR operational performance as documented by the system manufacturer.
NOTE: We recommend use of a graphing program with the capability to calculate “R” numbers. It is useful to plot the measured data points on the expected baseline graph. An “R” number should be produced to read 0.99 or greater in order to achieve regulatory compliance.
(2) First, select the EU values for which there are both expected and measured data.
Then, obtain the decimal unit values for each data pair. Use the following statement to compare the decimal unit values for the expected and measured data.
(3) If the measured data, denoted as mX , is within the expected data plus or minus half the resolution, denoted as 2resXe ± , then the parameter data value is known with 100 percent certainty to be in compliance. This statement is represented mathematically by, 2 resXX2resX eme +≤≤− The above comparative analysis must be made for each parameter’s operational range.
c. Data Application/Desired Output. This paragraph provides recommendations and information based on the conclusions from the analysis in paragraph 5b. The analysis in paragraph 5b concludes that:
(1) The design is in compliance with 14 CFR,
(2) The system relating to the applicable parameter sensor needs to be recalibrated, or
(3) The parameter must be recorrelated.
d. Ensure Compliance. The final step is to ensure that the parameters with measured data not within the expected data limits are in compliance. To reach conclusion (2) above, the data must be analyzed and a consistent discrepancy must be identified between the measured and expected data values. While the applicable system is in a neutral state, adjust to within the limits.
Conclusion (3) above is a result of random inaccurate trends identified in the comparison analysis. The applicable system needs to be repaired, or replaced.
Appendix 3 APPENDIX 3. DIGITAL FLIGHT DATA RECORDER PARAMETER
REQUIREMENTS FLOWCHART
Appendix 3
Appendix 3 B Manufactured on or before 10/11/91?
NO Flight Data Acquisition Unit (FDAU) as of 07/16/1996?
Part 121 Flight Recorder Parameter Requirements, §121.344 YES YES YES No FDAU More than two engines?
§121.344(b) Appdx B. Record 17 parameters.
Parameter 18 req’d based on capacity.
§121.344(b) Appdx B. Record 18 parameters.
YES NO Analog FDAU §121.344(b) Appdx M. Record 22 parameters.
Parameters 12-17, single source allowed.
§121.344(c) Appdx M. Record 22 parameters*.
Parameters 12-14, single source allowed.
Digital FDAU NO Manufactured after 8/20/2002?
§121.344(f) Appdx M 88 parameters Manufactured after 8/18/2000?
NO YES §121.344(e) Appdx M 57 parameters* §121.344(d) Appdx M 34 parameters* NO B.2 Page 3-4 §121.343 B.1 D Page 3-5 §121.344a END * Commensurate with capacity, any other parameters (of 88) that have information sources installed and connected to the recording system.
From Page 3-2 §91.609 From Page 3-1 Aircraft listed in §121.344(l)(2)?
10-19 passenger seats?
YES NO US registered or brought on US Op Specs after 10/11/91?
YES B.3 Page 3-8 §135.152 NO
Appendix 3 Manufactured after 10/11/1991?
§121.343(f) Appdx B 29 mandatory and 12 recommended parameters.
NO YES §121.343(d) Appdx B 17 mandatory parameters.
NO B.2 Part 121 Flight Recorder Parameter Requirements, §121.343 From Page 3-3 §121.344 Has a digital databus & ARINC 717 DFDAU?
Manufactured after 5/26/1989, or type certificated after 9/30/1969?
YES §121.343(c) Appdx B 11 mandatory parameters.
YES NO §121.343(f) Appdx B 29 mandatory and 12 recommended parameters.
END
Appendix 3 Manufactured Before 8/18/1997?
§121.344a(b)(1) Appdx M 57 parameters***.
B.3 Part 121 Flight Recorder Parameter Requirements, §121.344a Listed in §121.344a(f)?
YES §121.344a(c) Appdx M 88 parameters.
YES Not required to comply with part 121.
May be required to comply with §135.152.
END NO Manufactured After 8/20/2002?
Manufactured After 8/18/2000?
YES Brought on US Register after 10/11/1991?
Foreign Registered and added to US Ops Spec after 10/11/ 1991?
NO NO Not required to carry a FDR.
§121.344a(1)(2)(3) 18* or 22** parameters listed in §121.344(a). Ranges, accuracies, and resolutions as specified in part 135 Appndx B.
YES * Either the parameter listed below must be recorded:
§121.344(a)(12) or (a)(15) §121.344(a)(13) or (a)(16) §121.344(a)(14) or (a)(17) For airplanes with more than two engines, §121.344(a)(18) must also be recorded if sufficient capacity is available on the existing recorder.
Parameters §§121.344(a)(12) through 121.344(a)(17) each may be recorded from a single source.
** Commensurate with the capacity of the recording system (FDAU or equivalent and the DFDR).
*** Commensurate with the capacity of the recording system, all additional parameters (88) listed in §121.344(a) for which information sources are installed and which are connected to the recording system.
D YES From Page 3-3 §121.344 10-19 Passenger Seats?
Less than 10 seats?
YES YES NOYES NO NO END Not required to carry a FDR NO Page 3-8 §135.152 NO
Appendix 3