Flight Data Recorder Rule Change


In late 1997 the U.S. Federal Aviation Administration (FAA) adopted a change requiring an increase in the number of recorded signals for flight data recorders (FDR). This rule change will affect many airplanes that operate under FAA rules, including all airplanes registered in the United States and those in other countries where regulatory authorities use the FAA rules as their own. Boeing is prepared to help operators meet the requirements of the rule change by its effective date, which varies according to each airplane's date of manufacture.

In the interest of further increasing safety in the commercial airplane industry, the U.S. Federal Aviation Administration has effected a rule change that increases the amount of flight information collected in flight data recorders (FDR). The ability to gather additional information after a commercial airplane accident or incident can result in a more thorough investigation, as well as help the industry identify trends and make necessary modifications to prevent future accidents and incidents. Boeing is offering operators the support they need to meet the requirements of the new FAA rule by the date of compliance. ("Performance Data for European Operators" in the January-March 1997 issue of Airliner magazine addresses the rule for operators of JAA-registered airplanes.) The following article discusses:

1. Purpose of flight data recorders.
2. History of flight data recorders.
3. Summary and effects of the flight data recorder rule change.
4. Boeing support for operator compliance.

1 Purpose of Flight Data Recorders
The purpose of an airplane flight data recorder system is to collect and record data from a variety of airplane sensors onto a medium designed to survive an accident. Depending on the age of an airplane, the FDR system may consist of (1) an analog or digital flight data acquisition unit (FDAU) and a digital FDR (DFDR) that may have a tape or solid-state memory, or (2) simply an FDR. The protected medium that collects data from an airplane resides in the FDR or DFDR. This recording system has been installed in thousands of airplanes, and continues to play a key role in making airplane travel as safe as possible.

The data collected in the FDR system can help investigators determine whether an accident was caused by pilot error, by an external event (such as windshear), or by an airplane system problem. Over the years, these data have contributed to airplane system design improvements and the ability to predict potential difficulties as airplanes age. An example of the latter is using FDR data to monitor the condition of a high-hours engine. Evaluating the data could be useful in making a decision to replace the engine before a failure occurs.

2 History of Flight Data Recorders
Flight data recorders were first introduced in the 1950s. Many first-generation FDRs used metal foil as the recording medium, with each single strip of foil capable of recording 200 to 400 hr of data. This metal foil was housed in a crash- survivable box installed in the aft end of an airplane. Beginning in 1965, FDRs (commonly known as "black boxes") were required to be painted bright orange or bright yellow, making them easier to locate at a crash site.

Second-generation FDRs were introduced in the 1970s as the requirement to record more data increased, but they were unable to process the larger amounts of incoming sensor data. The solution was development of the flight data acquisition unit (FDAU).

As shown in figure 2, the FDAU processes sensor data, then digitizes and formats it for transmission to the FDR. The second-generation digital FDR (DFDR) uses tape similar to audio recording tape. The tape is 300 to 500 ft long and can record up to 25 hr of data. It is stored in a cassette device mounted in a crash-protected enclosure.

FAA rule changes in the late 1980s required the first-generation FDRs to be replaced with digital recorders. Many of the older FDRs were replaced with second-generation magnetic tape recorders that can process incoming data without an FDAU. Most of these DFDRs can process up to 18 input parameters (signals). This requirement was based upon an airplane with four engines and a requirement to record 11 operational parameters for up to 25 hours (see "Parameters Explained" below).

Another FAA rule change that took effect October 11, 1991, led to the installation of digital FDAUs (DFDAUs) and DFDRs with solid-state memory on all Boeing airplanes before delivery. This FDR system was required to record a minimum of 34 parameter groups. The DFDAU processes approximately 100 different sensor signals per second for transmission to the DFDR, which uses electronics to accommodate data for a 25-hr period.

Today all Boeing current-production models use DFDR systems, which will store 64 12-bit words per second (wps) over a 25-hr period in electronic memory. At the end of the 25 hours, the DFDR will begin recording the most recent data over the oldest data. No tape removal is required with these systems. Each of these systems on every Boeing model (except the 777) have at least two data frames that are transmitted from the DFDAU to the DFDR (see "What Is a Data Frame?" below).

These separate data frames accommodate the different regulatory agency requirements. A 128-wps DFDR was available for the Boeing 777 and MD-90, allowing the development of one data frame that incorporated all regulatory agency requirements and that required operators to develop only one data frame decode algorithm. "How a FAA Rule Is Changed", below, explains the basis on which the FAA may propose rule changes.

3 Summary and Impact of FAA FDR System Rule Change
The rule change addresses all Boeing commercial airplane models and groups them as follows:

AIRPLANES MANUFACTURED PRIOR TO OCTOBER 11, 1991, WITHOUT AN FDAU OR DFDAU INSTALLED AS OF JULY 16, 1996.
The new rule requires that by August 18, 2001 the FDR record at least 18 parameter groups. For most airplanes, this is an increase from 11 parameter groups, as described in "Effects of 1989 FAA Flight Data Recorder Rule Change" on page 32. On about half of all the Boeing 727, 737, DC-8, and DC-9 models the FDR system uses a single FDR, a result of the late 1980s replacement activity. Most of these FDRs should have enough spare inputs to accommodate the increased requirements with little or no modification required. Other parameter groups required to be recorded include the addition of both flight control surface positions and flight control inputs for all three axes (lateral, directional, longitudinal), lateral acceleration, and autopilot engagement status. Airplanes manufactured prior to October 11, 1991, with a FDAU or DFDAU installed as of July 16, 1996. The new rule requires that by four years from date of rule at least 22 parameter groups be recorded by the FDR. In this group are Boeing models 727, 737, 747, 757, 767, DC-10, and MD-80. Most of these airplanes record almost all the 22 parameter groups, some of which operators may ask Boeing to remove to save weight or to avoid maintenance costs if a parameter group is not required by a particular country's regulatory agency. The additional parameter groups required to be recorded include the addition of flight control surface positions and flight control inputs for all three axes, lateral acceleration, and autopilot engagement status.

AIRPLANES MANUFACTURED AFTER OCTOBER 11, 1991.
The 34 required parameter groups for this category are all recorded, with a few exceptions (some of the required recording rates are not met for flight control surface positions, flight control inputs, or both). The rule gives operators until August 18, 2001, to comply. Since the rule became effective August 18, 1997, the FDR system changes required for airplanes manufactured after August 18, 2000, will affect only new production. The new-production part of the rule changes require 57 parameter groups to be recorded by August 18, 2001, and 88 parameter groups by August 18, 2002.

4 Boeing Support for Operator Compliance
Boeing models 707, 727, 737-100/-200/-300/-400/-500, 757, 767, 747-100/-200/-300/-400, 777-200/-300, DC-8, DC-9, DC-10, MD-11, MD-80, and MD-90 will require retrofit activity. This may involve the addition of new sensors and wiring plus installation of a DFDAU, software, or both because of a new FDR frame. The details of the Boeing plan to support the airplanes listed below are discussed in "Rule Change Support Plan".

The following airplanes are covered by the rule change support plan:

Summary
The FDR rule change effected by the FAA in late 1997 will require operators of airplanes flying under FAA rules to make sure the FDRs on their airplanes can record several additional parameter groups. The compliance date for these airplanes depends on their date of manufacture. Boeing is ready to support all customers with their activities to meet the new FDR rule. Operators should contact Boeing to initiate a customer requested change if their airplanes need additional sensor and bracket installations but are not covered in the service bulletins that Boeing offers. Though Boeing has no plans to provide unique FDR data frame updates for airplanes manufactured before October 11, 1991, the company will respond to requests for assistance if an operator generates a customer change request.


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Parameters Explained
The text in the new rule from the U.S. Federal Aviation Administration (FAA) lists 88 operational parameters required to be recorded by digital flight data recorders (DFDR). To meet each of these requirements, based upon the design of an airplane, more than one parameter may need to be recorded by the flight data recorder (FDR) at the same time. An example of this is the operational parameter thrust/ power of each engine-primary flight crew reference. On most Boeing- and Douglas-designed airplanes, two parameters (signals) per engine are provided to the FDR system to capture the thrust/power of each engine. As a result, 88 defined operational parameters in the FAA rule will result in many more than 88 parameters actually recorded. To avoid confusion, Boeing identifies each of the 88 operational parameters in the new FAA FDR rule as 88 parameter groups, as each can require recording more than one parameter.


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How an FAA Rule Is Changed
New rules or rule changes can be prompted by many things, including the advent of new technology, accident data, or Congressional mandates. The U.S. National Transportation Safety Board (NTSB), which performs all airplane accident investigations in the United States, issues a written safety recommendation to the U.S. Federal Aviation Administration (FAA) to consider as a subject for rulemaking. In the case of the flight data recorder (FDR) system rule change, the NTSB stated that more airplane information must be recorded by the FDR system. This recommendation was based upon the NTSB's findings and the difficulty they encountered in their investigations because of a lack of adequate flight information.

The FAA must evaluate NTSB safety recommendations based on many factors. Two of these are the economic impact of the change and the ability to produce and govern the regulation. Public and private hearings regarding the proposed changes often are held to aid the FAA in this evaluation process. In the 1980s, the FAA established the Aviation Rulemaking Advisory Committee (ARAC) to improve the regulatory process and improve communication between the FAA, airline operators, and manufacturers on new regulations. The main task of ARAC is to work with the FAA to evaluate the many factors resulting in rules that can be technically and economically justified, then feasibly implemented and regulated.

The new FDR system rule resulted from three NTSB safety recommendations to the FAA. The FAA held a public hearing on April 20, 1995, to discuss the NTSB recommendations that spawned a rulemaking process within ARAC. A flight data recorder working group was established by the FAA and directed to draft the Notice of Proposed Rulemaking (NPRM) for the FDR system. This NPRM would become the final FDR rule from the FAA. The working group, representing the FAA, NTSB, airplane manufacturers, and airplane operators, was to report its results (a draft NPRM) to the ARAC Executive Committee. The FAA would then use the draft to create the final NPRM.

The Administrative Procedures Act requires that every Federal rule (except those of an emergency nature and certain others) first be issued as a "proposed rule" (NPRM) and provide time for the public to review and comment on it. When an NPRM is published in the Federal Register, the public is allowed time to comment on the FAA's discussions and conclusions presented in the preamble of the NPRM, as well as the text of the proposed rule itself. The preamble discusses the historical background that prompted the proposed rule, as well as how and why it should be implemented. The preamble includes a review of the cost-versus-benefit information in order to justify the proposal. When the public comment period ends, the FAA addresses each comment submitted and determines the content of the final rule. (The content of the final rule may be changed in light of comments received.) ARAC may be invited to participate, but often is not. The final rule, including its effective date, is also published in the Federal Register.


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What Is a Data Frame?
A flight data recorder (FDR) data frame is the order of the words that are transmitted from the digital flight data acquisition unit (DFDAU) to the digital FDR (DFDR) each second over many seconds (see ARINC 717 for additional information). Most FDR system data frames are made up of four subframes within one superframe. For a 64-words-per-second (wps) FDR system, a DFDAU will output 64 12-bit words to the FDR each second, where each word typically contains the value of an analog parameter. The order of the words (for example, word number 12 of the 64 words) within a subframe, as well as the order of the subframes, define an FDR data frame. This order is important to understand in order to decode the data recorded in the DFDR.

Some Boeing airplanes have two data frames, because one data frame in an FDR system with a capability of 64 wps cannot accommodate all of the world's regulatory requirements. By comparison, the 777 FDR system can handle 128 wps. In order to meet the new rule from the U.S. Federal Aviation Administration (FAA) that requires recording of 88 parameter groups by August 18, 2002, FDR systems on Boeing airplanes will handle 256 wps.


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Effects of 1989 FAA Flight Data Recorder Rule Change
The FAA rule change in 1989 required a flight data recorder (FDR) that provided a digital method of recording, storing, and readily retrieving data. It also increased the number of parameter groups to a total of 11 from 6:

Because most airplanes recorded only six parameter groups, nearly all operators were required to retrofit the FDRs in their airplanes. In response to this requirement, many FDR manufacturers developed crash-survivable FDRs that did not require flight data acquisition units to replace the first-generation foil FDRs, and that accommodated the 11 required parameter groups for airplanes with up to four engines. Airplanes such as the 737 that have these FDRs can accommodate up to 18 parameter groups, as they have only two engines for which data must be recorded.


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Where To Find the FAA FDR Rule
The full content of the FAA FDR rule is listed in the Federal Register Part IV, Department of Transportation, Federal Aviation Administration, section 14 of the Code of Federal Regulations (CFR), affected parts:

The rule may be found on the World Wide Web at the following address:
http://www.faa.gov/avr/arm/nprm/nprm.htm


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Rule Change Support Plan
Boeing plans the following activities to help operators comply with the FAA rule change for flight data recorders.

717-200.
This model will be equipped to meet the new rule.

727 AND 737-100/-200. (ALL MANUFACTURED BEFORE OCTOBER 11, 1991), AND 737-300/-400/-500 MANUFACTURED BEFORE OCTOBER 11, 1991.
Service Bulletin (SB) 727-31-0059, SB 737-31-1100, and SB 737-31-1099, respectively, provide for purchase of a parts kit (sensor brackets), supplier information for ordering sensors, and wiring examples from the sensors to the flight data recorder (FDR) (airplane tail) or flight data acquisition unit (FDAU)/digital FDAU (DFDAU). These parts would address flight control surface positions and flight control inputs for all three axes and lateral acceleration. Boeing technical support for the autopilot/flight director computer (AFDC) engaged is available upon request in each of these three categories of airplanes.

737-300/-400/-500 MANUFACTURED AFTER OCTOBER 11, 1991, BUT BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
These models will need a new FDR frame (see "What Is a Data Frame?"). Boeing is working with its FDAU suppliers to develop a common data frame across all Boeing models.

737-600/-700/-800.
These models will be equipped to meet the new rule.

747-100/-200/-300.
Most of these airplanes record the required 22 parameter groups. However, a service bulletin, if requested by an operator, could provide for a parts kit (sensor brackets), sensors supplier information for ordering, and wiring examples from the sensors to the FDAU/DFDAU and for the AFDC engaged discrete. The parts kit would address both flight control surface positions and flight control inputs for all three axes and lateral acceleration.

747-400S MANUFACTURED BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
These models will need a new FDR frame. Boeing is working with its FDAU suppliers to develop a common data frame across all Boeing models. A service bulletin will be released for a digital flight data acquisition card update.

757S AND 767S MANUFACTURED BEFORE OCTOBER 11, 1991.
A service bulletin is currently in work and will be released to provide for purchase of a parts kit (sensor brackets), sensors supplier information for ordering, and wiring examples from the sensors to the DFDAU.

These parts would address both flight control surface positions and flight control inputs for all three axes and lateral acceleration. Boeing technical support for the AFDC engaged discrete is available upon request. Also, incorporation of SB 757-31-0059 and SB 767-31-0091 for correction of engine indicating and crew alerting system (EICAS) filtering of flight control data is required.

757S AND 767S MANUFACTURED BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
These models will need a new FDR frame and incorporation of the service bulletins for correction of EICAS filtering of flight control data resulting from PRR 54727 (757) and PRR B12710 (767). Boeing is working with its FDAU suppliers to develop a common data frame across all Boeing models.

777S MANUFACTURED BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
These models will need a new FDR frame. Boeing is working with its FDAU suppliers to develop a common data frame across all Boeing models. A service bulletin will be released for an airplane information management system (AIMS) digital flight data acquisition function update.

ALL CURRENT-PRODUCTION BOEING MODELS.
These models will require retrofit of new flight recorder data frames that will address the 34 parameter groups. The plan is to design the data frames as required to meet the new FDR rule and provide these designs in all the appropriate Boeing documentation. This activity is required because the MD series, 737, 757, and 767 DFDAUs that will incorporate this update are buyer- furnished equipment (selected by the operator).

AIRPLANES THAT REQUIRE 18 TO 22 PARAMETER GROUPS AND WHOSE DATA FRAMES WILL BE AFFECTED.
These airplanes will be a subset of the new data frames. For these airplanes, as well as for the MD series, 737, 757, and 767, Boeing plans to accomplish the data frame development and lab testing short of installation and certification on the airplane, and update all the appropriate documentation. Boeing can certify these data frames for an operator if an operator generates a customer change request to install the new data frame. Installation would occur on a production airplane for delivery prior to the production cut-in of the 57/88 parameter groups.

747-400 AND 777.
For these two models Boeing provides the FDR acquisition function (supplier-furnished equipment). The 747-400 uses a digital flight data acquisition card (DFDAC). The 777 uses a digital flight data acquisition function (DFDAF) that resides in a module in both cabinets of the AIMS. The data frame updates for these models will be provided to operators through a purchased service bulletin. The 777 service bulletin will be a software change only.

DC-8, DC-9, AND 707 (ALL MANUFACTURED BEFORE OCTOBER 11, 1991).
Boeing believes that these models comply with the 1989 FAA requirement for 11 parameter groups. A service bulletin, if requested by an operator, could provide for a parts kit (sensor brackets), sensors supplier information for ordering, and wiring examples from the sensors to the FDAU/DFDAU. The parts kit would address both flight control surface positions and flight control inputs for all three axes, the auto-pilot engaged discrete, and lateral acceleration.

DC-10 (ALL MANUFACTURED BEFORE OCTOBER 11, 1991) AND MD-80 (WITH FDAU) MANUFACTURED BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
A kit configuration notice (KCN) is available upon customer request to provide instructions for rewiring the programming plug of the currently installed FDAU to create a new FDR frame, which will meet the increased parameter recording rates. This same KCN can include flight control input position sensors and wiring, plus provide instructions for removing the wiring for parameters (signals) currently being recorded that are not required by the new FAA rule. Removal of parameters not required by the new rule is required to use the currently installed 64-words-per-second (wps) FDR system.

MD-80, MD-90, AND MD-11 MANUFACTURED BEFORE AUGUST 18, 2000 (PRODUCTION CUT-IN OF 57/88 PARAMETER GROUPS).
The DFDAUs installed on these models will need a new FDR frame to meet the increased parameter recording rates. A KCN is available upon customer request to provide instructions for adding flight control input position sensors and wiring, plus provide instructions for removing the wiring for parameters currently being recorded that are not required by the new FAA rule. Removal of parameters not required by the new rule is required to use the currently installed 64-wps FDR system.

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