December 15, 2010 

U. S. Department of Transportation 

Docket Operations 

West Building Ground Floor, Room W12-140 

1200 New Jersey Avenue, SE. 

Washington DC, 20590 

Subject: Request for Exemption to Sections of 14 CFR Part 121.344: 

American Airlines, Inc. would like to petition the Federal Aviation Administration for a timelimited exemption of 18 months from December 6, 2010, to 14 CFR 121.344 to continue 14 CFR 

121 operations of three 737-823 series aircraft using a flight data recorder system that does not 

fully comply with the recording interval requirements for the rudder pedal input force parameter. 

This parameter is one of the three force parameters listed as parameter 88 in 14 CFR 121.344 

(a). This exemption request involves the same 737-7 data frame which American was granted 

an exemption of the left elevator position parameter (Reference Exemption No.1 0173, 

Regulatory Docket No. FAA-2010-1178 dated December 9,2010). The rudder pedal force 

anomaly behaves the same as the left elevator position parameter. Intermittently, from 4 to 5 

seconds apart, 1 sample of the 8 samples per second records the previous second's sample. 

Applicable Sections: 

14 CFR 121.344 (f) states "For all turbine-engine-powered transport category airplanes that are 

manufactured after August 19, 2002 - (1) The parameters listed in paragraph (a) (1) through 

(88) of this section must be recorded within the ranges, accuracies, resolutions, and recording 

intervals specified in Appendix M of this part. " 

14 CFR 121.344 Appendix M (Note 18) states "For all aircraft manufactured on or after 

December 6, 2010, the seconds per sampling interval is 0.125. Each input must be recorded at 

this rate. Altemately sampling inputs (interleaving) to meet this sampling interval is prohibited. " 

Extent of Relief 

This time-limited exemption would allow for the continued domestic and international operations 

of the following American Airlines operated B737-823 series aircraft (see Table 1) for 18 months 

after December 6, 2010, without the fully compliant recording interval of the rudder pedal force 

parameter (see Table 2): 

Make I Model 

Boeing 1737-823 

Boeing 1737-823 

Boeing 1737-823 

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Serial # 

31111 

29554 

40584 

Line # 

3487 

3493 

3499 

Registration # 

N864NN 

N865NN 

N866NN 
American Airlines - 737NG Exemption Request 

Table 2 

121.344 (f) 

Parameter # 

88 

Reason for relief 

Appendix M 

Requirement 

Rudder Pedal Input Force 

Input to DFDAU 

Rudder Pedal Force Data 

(1 sample of the 8 Hz set 

eve 4 to 5 seconds 

This exemption is necessitated by the Aircraft Manufacturer (Boeing) and the Digital Flight Data 

Acquisition Unit (DFDAU) system I software supplier's (Teledyne) need to develop, validate, and 

integrate the enhanced system software into the aircraft type design. This enhanced software 

will provide for the DFDAU recording of all regulatory required parameters and allow American 

Airlines time to install the software without significantly affecting flight operations. 

Background 

Summary: 

A 737NG Flight Data Recorder System (FDRS) anomaly was discovered during Boeing flight 

line airplane operations. It was found that the left elevator position parameter was not being 

acquired, hence not recorded properly. Subsequent review of the data frame identified the 

rudder pedal force parameter as also having the same anomaly. American Airlines was not 

informed of the rudder pedal force parameter anomaly until December 13, 2010. Boeing has 

stated that their comprehensive review did not detect further anomalies. 

This FDRS configuration includes a Teledyne Digital Flight Data Acquisition Unit (DFDAU) with 

the 737-7 data frame enabled. The data frame is a 512 words per second data frame that was 

certified in April of 2010 to meet the latest FAA regulations (§ 121.344 (f) Appendix M), which 

was effective starting December 6, 2010. The following describes the anomaly and discusses 

Boeing's plan to correct the discrepancy. 

Discussion: 

The root cause of this anomaly is found in a DFDAU software acquisition timing error. 

Periodically, in a given parameter acquisition cycle, the DFDAU is requesting the acquisition of 

more parameter data than it has time to complete in that acquisition cycle. Because parameter 

acquisition does not have time to complete the previous valid sample is used in the recording 

rather than the desired current sample. 

The DFDAU software is on-wing load able and Teledyne has informed Boeing that this anomaly 

can be fixed with a minor software revision resulting in new software part numbers. 

Plan to Correct Anomaly: 

Boeing has verbally notified the FAA and is in the process of filing a "Report of Noncompliance 

with Part 25 Airworthiness Regulations" with the FAA stating that the anomaly does not 

represent a safety issue for continued operation. 

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American Airlines - 737NG Exemption Request 

Boeing has a signed contract with Teledyne and plans to certify the new DFDAU software in 

approximately 5-6 months. The date of certification is contingent on what is found during test 

which may cause the schedule to move either left or right. In any case, Boeing is actively 

working to accelerate the certification of corrected software. 

Upon receipt of the Boeing Service Bulletin and certified software, American Airlines will install 

this software within 90 days, terminating the need for the exemption. 

Public Interest 

The granting of this exemption would be in the public interest by allowing American Airlines to 

continue providing service to domestic and international destinations utilizing the B737 -823 

series aircraft listed in Table 1. 

Failure to grant this exemption may require American Airlines to cancel flights and disrupt 

schedules causing significant financial loss as well as impose inconvenience and potential losttime cost to the traveling public. 

Affect on the Level of Safety 

American Airlines understands that the flight recorder parameters do not have an impact on the 

safe operation of aircraft, but they do provide a means for increasing safety based on availability 

of data after an occurrence, accident or incident. American believes that the infrequent loss of 

one sample of the 8-Hz sampling of the rudder pedal force parameter will not cause significant 

burden in obtaining a sufficient amount of data from this parameter. The availability of the 

rudder pedal position and rudder parameters will also enhance the missing data. 

Summary for the Federal Register 

As described in 14 CFR 11.87, American Airlines requests that this exemption not be published 

in the Federal Register and follow with request for comments due to the ensuing delay of 

potentially granting the exemption. 

American Airlines is requesting an exemption from 14 CFR Part 121.344 to allow for the 

continued operation of B737 -823 series aircraft in domestic and international revenue service 

without the recording of all 8 samples of the rudder pedal force data. This exemption shall allow 

the Aircraft Manufacturer (Boeing) and the DFDAU System Software Provider (Teledyne) time 

to develop, validate, and certify the software to correct the DFDAU anomaly and allow American 

Airlines time to install the software with minimal interruption to flight scheduling. 

Use of the Exemption outside the United States 

American Airlines would like to utilize the privileges of this exemption outside the United States. 

The primary scheduled operations for this model aircraft in American Airlines fleet includes 

international operations primarily in Mexico, Canada, Central America, South America and the 

Caribbean. 

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American Airlines - 737NG Exemption Request 

Your consideration of the foregoing and expedited approval of this request is appreciated. If you 

have any questions regarding this request, please feel free to contact this office. 

Sincerely, 

~t?i?~ Vice President 

Engineering, Performance and Quality Assurance 

On behalf of: American Airlines, Inc. 

Air Carrier Certificate AALA025A 

3900 N Mingo Rd, MD 183 

Tulsa, OK 74116 

Phone: 918-292-2902 

Fax: 918-292-1830 

Email: bill.cavitt@aa.com 

cc: Federal Aviation Administration 

AAL Certificate Management Office 

c/o Mr. William T. Satterfield, PAl 

14800 Trinity Blvd, SI. 100 

Fort Worth, Texas 76155 

The Boeing Company 

B. C. Groenewegen, 

Manager, Continued Airworthiness 

Twin Aisle Programs 

P.O. Box 3707 

Seattle WA 98214-2207 

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