AFS-11-205-E May 24, 2011

Exemption No. 10269 Regulatory Docket No. FAA-2011-0188

Mr. William M. Cavitt Vice President, Engineering, Performance and Quality Assurance American Airlines, Inc. 3900 N. Mingo Road, MD 183 Tulsa, OK 74116

Dear Mr. Cavitt:

This letter is to inform you that we have granted your request for exemption. It relays our decision, explains its basis, and gives you the conditions and limitations of the exemption, including the date it ends.

The Basis for Our Decision:

By letter dated February 24, 2011, you petitioned the Federal Aviation Administration (FAA) on behalf of American Airlines, Inc. (American), for an exemption from § 121.344(f) and part 121, Appendix M, of Title 14, Code of Federa l Regulations (14 CFR). This exemption, if granted, would allow American the continue d operations of the following American B737- 823 series aircraft for 18 months from the date of this letter without complying with 14 CFR § 121.344(f) and part 121, Appendix M (footnot e 18), the accuracy requirement for pitch control surface position and rudder control input force.

The FAA has determined that good cause exists for waiving the requirement for Federal Register publication because the exemption, if granted, would not set a precedent and any delay in acting on this petition would be detrimental to American.

The FAA has issued a grant of exemption to American Airlines in circumstances similar in all material respects to those presented in this petition. In Grant of Exemption No. 10173A (copy enclosed), the FAA granted relief from recording the parameters listed under 14 CFR § 121.344(f) and part 121, Appendix M (f ootnote 18), because American minimized the impact of the loss of the flight recorder dataand showed the loss of the data did not affect the safety of the aircraft.2

Having reviewed your reasons for requesting this exemption, I find that—

 they do not differ materially from those presented by American in the enclosed grant of exemption;

 the reasons stated by the FAA for granting the enclosed exemption also apply to the situation you present; and

 a grant of exemption is in the public interest.

Flight data recorders (FDR) are required by regulation, because they are recognized as an essential tool for investigating accidents and inci dents. Although a digital flight data recorder (DFDR) does not affect flightcrew procedures , it is critical for later analysis of crew performance and the procedures used during an accident or incident.

The petitioner states that a Boeing 737 NG ai rplane elevator indication anom aly was discovered during ground operations that consequently led to the discovery of a flight data recorder system (FDRS) anomaly. Further investigation uncovered an identical anomaly associated with the recording of the rudder control input force.

On October 19, 2010, a problem was detected on a Boeing production 737 NG airplane. The display of the left elevator position on the center lower display of the com mon display system (CDS) was lagging when compared to the right elevator position on the same display. The CDS retrieves surface position data from the digital flight data acquisition unit (DFDAU) for flightcrew display. The petitioner notes that the display of elevator position is not required to meet certification regulations and only supports an optional ground maintenance operation to aid in airplane dispatch. The display of the el evator positions (along with other primary flight control positions) on the CDS is a customer option. The petitioner’s aircraft are not equipped with this option. When the elevator indication problem was reported, the FDR was downloaded, and the data was analyzed to determine if the problem seen on the CDS was also present in the FDR elevator position data. This analysis also detected an identical problem with the rudder control input force recording. The FDR data analysis showed that, at times, one of the eight samples of data, in a given second, could be stale (repeating a previous sample) and is visible if there is a rapid movement of the elevator position or rudder controls. The anomalous data are usually present in each parameter only once every 5 seconds (i.e., once every 5 seconds there are seven valid samples and one invalid sample in a 1-second acquisition period, or subframe). The FDRS anomaly does not exist in the right elevator position data or the other flight control input force data.

The root cause of this anomaly was found to be the result of a DFDAU software acquisition

tim ing error. Periodically, in a given parameter acquisition cycle, the DFDAU is requesting the acquisition of more parameter data than it has time to process in that acquisition cycle. Because the parameter acquisition does not have time to complete the cycle, a previous valid sample is used in the recording rather than the desired current sample.3

The petitioner states that Boeing had “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.” The petitioner also states that Boeing has a pending contract w ith Teledyne, the manufacturer of the DFDAU. The plan is to certify new DFDAU software by mid-August 2011. The date of certification is contingent on what is found during testing that may cause the schedule to change. Boeing is actively working to accelerate the certification of corrected software. Teledyne has informed Boeing that this anomaly can be fixed with a minor software revision resulting in new software part numbers. The DFDAU software is field loadable, which minimizes the workload and schedule impact of accomplishing this change.

In support of allowing these aircraft to temporarily operate under this exemption, the petitioner notes that since the FDRS is recording the left elevator position and rudder control input force accurately at seven sam ples per second, there is not an adverse affect on the normal or irregular operation of the aircraft. The petitioner states that this anomaly can be addressed in ground processing of the data by eliminating the first sample, of eight, in each left elevator position acquisition cycle.

The FAA’s Decision:

In consideration of the foregoing, I find that a grant of exemption is in the public interest. Therefore, pursuant to the authority contained in 49 U.S.C. §§ 40113 and 44701, delegated to me by the Administrator, American Airlines, Inc., is granted an exemption from 14 CFR § 121.344(f) to the extent necessary to allow American to temporarily operate newly delivered 737 NG aircraft, subject to the conditions and limitations listed below.

Conditions and Limitations:

1. This exem ption only applies to the following aircraft.

Make Model Serial# Line# Registration# Boeing 737-823 40762 3634 N867NN Boeing 737-823 40763 3668 N868NN

2. This exemption covers only the recordation of the left elevator position, as part of the pitch control surface position parameter 15, and rudder control input force, as part of the flight control input force parameter 88, listed in 14 CFR part 121, Appendix M.

3. A copy of this exemption must be retained with the operator’s DFDR correlation documentation as specified in 14 CFR 121.344(j) until the airplanes identified in this exemption have incorporated the DFDAU system modification.

4. In the event of an accident or incident after which the DFDR data must be sent to the National Transportation Safety Board, American must provide a copy of this4

exemption and instructions on how to reprogram the DFDR ground read-out tool to eliminate the anomaly.

5. Following receipt of the modification service bulletins, American must provide, to its principal avionics inspector, a schedule for the completion of the new

installation.

This exemption terminates on the sooner of the installation of the DFDAU software update correcting the problem described in the petition, or 18 months after the date of this letter, unless sooner superseded or rescinded.

Sincerely,

/s/ Raymond Towles Acting Director, Flight Standards

Service

Enclosure