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Washington, DC 20553


Mr. Leon H. Tanguay
Director, Bureau of Safety
Civil Aeronautics Board
Washington, D. C. 20428


Dear Mr. Tanguay:

This will supplement our January 2, 1964, acknowledgment to your Letter,reference B-80-95, dated December 11, 1963, regarding the Pan American World Airways, Inc, Beoing 707-121, N709PA, aircraft accident near Elkton, Maryland, on December 8, 1963.

The recommendations and suggestions offered in your letter of December 17,1963, have been carefully considered along with other ideas for achieving improved protection against lightning stakes. The Agency is engaged in a program of studies, tests, and investigations to provide information essential to the development and application of superior protective measures.

Although the investigation of the accident has not yet disclosed evidence of the mechanism by which a lightning strike ignited the fuel, we have applied certain precautionary measures, each of which offers some degree of benefit. These are:

NOTAM issued on December 13, 1963, alerting pilots and traffic controllers to lightning hazards, need for thunderstorm avoidance, and encouraging use of PIREPS.

Telegram to air carriers and aircraft operators, on December 18, 1963, recommending the installation of static discharges on all aircraft using turbine fuels.

Airwothiness Directive on Boeing 707, 720, and 727 series aircraft, requiring modification of of fuel tank access door bonding, issued on February 4, 1964, as an adopted rule.

Airworthiness Directive on Boeing 707 and 720 series aircraft, requiring overlay on surge tank skin for improved protection against penetration, issued on February 21, 1964, as an adopted rule.

Information on all aspects of our program was given by the Federal Aviation Agency witness in testimony before the Board of Inquiry at Philadelphia on February 25. Thu letter, therefore, is limited. to A brief account of program status.

Technical Committee

A Technical Committee on lightning protection for aircraft fuel systems has been formed, composed of representation from the FAA, Civil Aeronautics Board, National Aeronautics and Space Administration, U. S. weather Bureau, U. S. Air Force, and U. S. Navy. The Committee has been meeting regularly and is providing guidance and assistance in planning and carrying out specific actions.

Installation of static dischargers

The response to the telegraphic recommendation of December 18, 1963, has been completely favorable. Installations are being made as parts become available. Late reports show that about 24 nut earner airplanes are yet to have dischargers installed. Availability of parts is the main factor in completing the reminder.

Collection and analysis of data

We are receiving lightning strike data from all available source. These data are being consolidated and analyzed with the assistance of the Technical Committee.

Contract with Atlantic Research Corp. (FA64WA-4955, dated January 30, 1965, Amount $70,259.00)

This work includes the evaluation of flame arrester designs for effectiveness, and studies and tests on other ways of protecting the vent system - such as explosion suppression and ventilation of vent outlet. Equipment calibration tests are now being conducted.

Contract With Lightning and Transients Research Institute (FA64WA-4960, dated February 4, 1964, Amount, $96,748.95)

This contractor is investigating the internal arcing possibility on typical wing tank construction, and will evaluate means of eliminating any arc found to exist. Later, proof tests of promising flame arrester designs will be conducted. The test article is in place and initial discharges are being fired to check out the equipment.

Planning for comprehensive research and development projects

A more comprehensive program of research and development will be required for the purpose of refining design criteria, making advanced studies of protection concepts — in general covering areas of investigation not possible in the short-range contracts with Atlantic Research Corp. and LTRI. The Technical Committee is now considering suggestions for the scope and nature of the projects.

Fuels study

The questions which have been raised concerning the relative safety of JP-4, kerosene, and mixes of the two are being studied. To assist in the resolution of these questions, we have asked the Coordinating Research Council to undertake a review of all available data on the subject. The CRC is proceeding with this work, which will serve to define the "state of the art," identify areas where research may be needed, and recommend how to accomplish any needed research. In addition, we have issued Advisory Circular No. AC 20-20, which furnishes some general information on the subject.

Reevaluation of aircraft in service

Based upon information now at hand, later to be supplemented by information from the contract work and from the accident investigation, we are proceeding with a reexamination of the basis for approval of lightning protective features of all turbine-engined aircraft.

Through your Mr. Hallman's participation as a member of the Technical Committee, we are receiving information on the continuing work by your investigators, and he is being regularly informed of the status of lightning program plans, actions, and results. We believe that the collective efforts being applied to this program will be successful in producing practical ways and means for improved protection.

George S. Moore
Flight Standards Service

This work is in the public domain in the United States because it is a work of the United States federal government (see 17 U.S.C. 105).