Appendix 6
(3) For dedicated parameters that are analog and analog discrete in nature, all of these requirements should be checked.
b. Operational: The operational check is a task to determine an item is fulfilling its intended purpose. An operational check is a failure-finding task and does not determine if the item is performing within specified limits. When applied to a DFDR, the operational check determines the DFDR is active and recording each parameter value within the normal operating range of the sensor. The operational check must also verify each electrical interface to the DFDRS. This may take place off the airplane.
c. System: A system functional check confirms interfaces to the recording system are present and functioning. This test confirms the presence of the electrical interfaces to the recording system and the function of dedicated sources. The operator must include a system functional check in the maintenance program. For dedicated sources, you may simulate sensor or transducer outputs to check the range, accuracy, sampling rate, and resolution of the recorded data. However, the instructions for continued airworthiness (ICA) and the operator’s maintenance program must prescribe a periodic system functional check of each of these transducers or sensors for range and accuracy.
15. Installed and connected to the recording system. This refers to the requirement to record parameters in addition to those specifically identified in the regulation (i.e., 22, 34, or 57 parameters, based on the date the aircraft was manufactured; see appendix 3). The DFDRS must record the parameters required by the aircraft’s existing DFDRS on July 16, 1996 if sufficient capacity is available in the upgraded DFDR. However, an operator is not required to upgrade the capacity of an installed recording system beyond that needed to record the mandated parameters.
In other words, a previously installed DFDR must continue to record parameters it was recording effective as of July 16, 1996, plus additional parameters if they are already connected and available to the system and if capacity exists in the system to record the parameters. Thus, if a retrofitted DFDRS can accommodate additional parameters, the retrofitted DFDR must continue to record any parameters not specifically mandated, but may be accommodated by the upgraded DFDRS. The FAA considers a parameter to be easily accommodated if it is provided by an installed system and it is already connected to the data bus. (See Sufficient Capacity definition below.)
16. Readily retrievable. This term means that the actual sensor value of the mandatory parameter can be retrieved from the storage medium by qualified personnel in 8 hours using:
a. Existing, easily understood instructions and commonly available tools and techniques;
and
b. Step-by-step procedures, including all conversion algorithms, necessary to derive and validate the values.
Note: These procedures must be a permanent part of the aircraft-specific DFDRS documentation package. Portions of the documentation package pertaining to the format and conversion algorithms of the recorded data may be recorded within the crash-protected memory of the DFDR.
A6-3
Appendix 6
17. Reasonableness. An off-airplane review of recorded data to assess the overall health of the recording system parameter. The review requires technical judgment to assess a parameter’s health functions off the airplane. Typically, the data is downloaded from the airplane and reviewed in a ground station tool away from the airplane, using graphical and tabular means.
The reasonableness check may identify gross parameter anomalies, such as static parameters, missing parameters, random movement in parameters, parameters not in agreement with related parameters in a given operational range or mode, etc. Technical judgment is required during the review so that the reviewer does not confuse acceptable airplane operational differences with parameter recording anomalies (i.e., the reasonability check is for parameter health and not piloting technique).
18. Single source. This term applies to certain split flight control parameters. It means that if it is necessary to conserve capacity in order to record the required parameters, the DFDR must record the position of only one of the two flight control positions.
a. For example, the DFDR may record the position of the aileron bellcrank instead of each aileron surface position. However, any recording from a single source must be made so the position of the flight control input can be differentiated from the position of the flight control surface.
b. In the example given, the installation instructions must tell the installer to place the aileron surface position sensor on one or the other bellcrank lobes to which one of the aileron surface actuator arms is attached—not the lobe to which the control yoke is attached.
19. Split flight control parameter. This applies to flight control and flight control surface parameters when the flight control system design allows the flightcrew to disconnect the captain’s controls from the first officer’s controls. This flight control system design is also known as breakaway capability.
a. The DFDRS must record multiple flight control positions, as well as multiple flight control surface positions.
b. For example, an aircraft flight control system design may allow the flightcrew to disconnect the captain lateral (aileron) control from the first officer lateral (aileron) control. The disconnection would leave the left aileron connected to the captain lateral (aileron) control and the right aileron connected to the first officer lateral (aileron) control. This would leave the captain capable of operating only the left aileron, and the first officer capable of operating the right only.
c. The captain and first officer control inputs (parameter 13) would be a split parameter necessitating each pilot’s lateral control position be recorded. The DFDRS must record both the left and the right lateral control surface (aileron) position (parameter 16) as well.
20. Sufficient capacity. This addresses the existing capacity of the installed DFDRS (either before retrofit or in new production) with regard to the addition of available parameters to be connected to the recording system. These parameters are in addition to the 22, 34, 57, or 88 parameter requirements, based on the aircraft date of manufacture (see appendix 3). Adding these parameters should not force the installation of a higher capacity acquisition unit (FDAU or A6-4
Appendix 6 DFDAU) or DFDR to accommodate these parameters. For example, if the existing DFDRS functions at a 64 word-per-second rate, the rule does not require the applicant to upgrade the system to function at a 128 word-per-second rate to accommodate these parameters, even if it means disconnecting previously recorded parameters that are not required to be recorded. (See, Installed and Connected to the Recording System, definition above.)
21. When an information source is installed. When this term appears in the parameter listing in the 14 CFR section or appendix, the parameter is mandatory only if the aircraft is fitted with a system that provides that capability. For example, it is not necessary to install an ice detection system to comply with parameter 61, but, if an ice detection system is already installed on the aircraft, the DFDRS must record its operation.
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