SumpThis: Fuel Contamination in General Aviation Aircraft

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National Transportation Safety Board
Washington, D.C. 20594

September 3, 1985

Messrs. Norman L. Horton and Jerry L. Wells
Aviation Safety and Management Consultants
4582 Old Stage Road
Central Point, Oregon 97502

Gentlemen:

Thank you for your letter of June 20, 1985, regarding engine failures in general aviation airplanes due to water in the fuel.

As you know, during the past several years, the National Transportation Safety Board's concern regarding accidents involving water in the fuel has resulted in the issuance of a number of related recommendations to the Federal Aviation Administration (FAA) which affect many thousands of airplanes. These include Safety Recommendations A-80-5 through -7 (information regarding detection and elimination of water from aircraft fuel systems and the inclusion of supplemental information in Pilot Operating Handbooks); A-81-9 through -11 (specifications and design criteria for airport aviation fuel storage and dispensing systems); A-83-66 (Maule auxiliary fuel tanks); A-83-3 through -11 (a comprehensive evaluation of aircraft fuel systems including fuel bladders, fuel caps, seals and leakage, fuel quick drains, fuel strainers, water collectors, and related Airworthiness Directives affecting large numbers of Cessna and Piper airplanes); A-84-104 through -107 (Cessna fuel reservoir tanks, Pilot Operating Handbooks and Manuals); and A-85-8 through -10 (Mooney fuel tanks, inspection and maintenance of fuel filler cap/adapter assemblies, leak testing procedures). Additionally, a number of airplanes you have tested regarding water-in-fuel problems, i.e., Cessna Models 206, U206, T207, and 182, have been addressed directly in Safety Recommendations A-83-3 through -7; the fuel preflight and drainage provisions of Piper Apache Models PA-23-150, -160, and -235 are currently being evaluated. Copies of the above-cited safety recommendations are enclosed for your information.

Prior to the issuance of these recommendations, the subject of water in the fuel had not received adequate attention from either the FAA or the manufacturers. However, that situation has changed significantly, and a number of substantial remedial actions have already been taken. Moreover, there is a new perspective and concern regarding water in the fuel, and directed probes such as those referenced in your letter continue to disclose problems which merit further attention.

The fuel system test results referenced in your letter indicating that a number of airplanes may not comply with applicable fuel system certification requirements has been an area of concern to the Safety Board for some time. The Board has advised the FAA of similar deficiencies in several of its safety recommendations; e.g., Safety Recommendations A-83-3 through -7 regarding Cessna airplanes that have flexible, rubberized bladder-type fuel cells in their wings. More importantly, the Board's evaluation of such fuel cells also disclosed that the deficiencies noted could be effectively resolved. For example, the Safety Board in Safety Recommendation A-83-6 recommended that the FAA:

Require a fuel system modification to Cessna single-engine airplanes with rubberized bladder-type fuel cells which will provide a means for positive detection and/or elimination of water from the fuel, such as an increased capacity fuel strainer or a separate water collector system and quick drains at the low point of the fuel system.

The FAA, in response to this and other Safety Board recommendations regarding Cessna bladder-type fuel systems, issued Airworthiness Directive (AD) 84-10-01. However, the Safety Board believes that the AD does not provide an adequate, reliable means for positive detection and/or elimination of water in the fuel. Some maintenance personnel who have carried out the provisions of the AD have expressed serious doubt as to its effectiveness. As more airplanes comply with the AD, there is increasing evidence to substantiate this belief; i.e, the continued occurrence of water-in-fuel accidents despite AD compliance such as those at Basile, Louisiana, on November 22, 1984, involving a Cessna 182 (N1857X); at Elmonte, California, on January 5, 1985, involving a Cessna 182 (N58816); and at Cold Foot, Alaska; on July 19, 1984, involving a Cessna U-206 (N3948G).

While AD 84-10-01 may partly alleviate the water-in-fuel problem, we believe that installation of a water separator (increased capacity fuel strainer) and quick drains at the low point of the fuel system should be required in airplanes affected by this AD. Such a water separator, available for installation on Cessna Model 180 and 182 airplanes, has already been certificated by the FAA through issuance of Supplemental Type Certificate (STC) SA-2628NM. The water storage/collection capacity of the separator (1 qt) is not likely to be exceeded, particularly in cases where AD 84-10-01 has already been complied with. In fact, compliance with AD 84-10-01 or an equivalent procedure might be considered a desirable prerequisite to such an installation. Therefore, an additional requirement by the FAA to have water separators installed would be logical, feasible and acceptable. The Safety Board will continue its efforts to persuade the FAA to take such positive action to address the water-in-fuel safety problem evident in the Cessna model airplanes.

Further, the number of fuel system deficiencies discovered by the Safety Board in recent years would seem to support a continued, selective testing of fuel systems of all general aviation airplanes. In fact, the Safety Board believes that the implementation of actions such as those proposed in safety Recommendation A-83-6 regarding Cessna airplanes and the related, continuing development of water separators/collectors, etc., might be applicable and effective in connection with existing fuel system deficiencies in other makes and models of airplanes. Therefore, while problems with general aviation fuel systems merit concern and further remedial action needs to be taken by both the FAA and the manufacturers, the Safety Board remains optimistic regarding the ultimate resolution of these fuel system problems. However, the Safety Board, unlike the FAA, is primarily an investigative agency and has no direct authority regarding aircraft certification. Therefore, the Safety Board's evaluation of fuel system deficiencies is derived largely from its accident/incident investigations and/or analysis of accident data.

The Safety Board is most appreciative of the time and effort you have expended toward improvement of general aviation fuel system safety. The Board would be pleased to evaluate any information you may wish to share with us regarding existing water-in-fuel problems, new investigative techniques regarding this subject, or development/testing of fuel system water separators. Therefore, I have asked Mr. Paul Alexander of the Safety Board's Bureau of Technology (telephone No. (202) 382-6654) to meet with you for further discussion of this matter.

Enclosures

Respectfully yours,

Jim Burnett
Chairman

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	Messrs. Norman L. Horton and Jerry L. Wells Aviation Safety and Management Consultants 4582 Old Stage Road Central Point, Oregon 97502

	Gentlemen:

	Thank you for your letter of June 20, 1985, regarding engine failures in general aviation airplanes due to water in the fuel.

	As you know, during the past several years, the National Transportation Safety Board's concern regarding accidents involving water in the fuel has resulted in the issuance of a number of related recommendations to the Federal Aviation Administration (FAA) which affect many thousands of airplanes. These include Safety Recommendations A-80-5 through -7 (information regarding detection and elimination of water from aircraft fuel systems and the inclusion of supplemental information in Pilot Operating Handbooks); A-81-9 through -11 (specifications and design criteria for airport aviation fuel storage and dispensing systems); A-83-66 (Maule auxiliary fuel tanks); A-83-3 through -11 (a comprehensive evaluation of aircraft fuel systems including fuel bladders, fuel caps, seals and leakage, fuel quick drains, fuel strainers, water collectors, and related Airworthiness Directives affecting large numbers of Cessna and Piper airplanes); A-84-104 through -107 (Cessna fuel reservoir tanks, Pilot Operating Handbooks and Manuals); and A-85-8 through -10 (Mooney fuel tanks, inspection and maintenance of fuel filler cap/adapter assemblies, leak testing procedures). Additionally, a number of airplanes you have tested regarding water-in-fuel problems, i.e., Cessna Models 206, U206, T207, and 182, have been addressed directly in Safety Recommendations A-83-3 through -7; the fuel preflight and drainage provisions of Piper Apache Models PA-23-150, -160, and -235 are currently being evaluated. Copies of the above-cited safety recommendations are enclosed for your information.

	Prior to the issuance of these recommendations, the subject of water in the fuel had not received adequate attention from either the FAA or the manufacturers. However, that situation has changed significantly, and a number of substantial remedial actions have already been taken. Moreover, there is a new perspective and concern regarding water in the fuel, and directed probes such as those referenced in your letter continue to disclose problems which merit further attention.

	The fuel system test results referenced in your letter indicating that a number of airplanes may not comply with applicable fuel system certification requirements has been an area of concern to the Safety Board for some time. The Board has advised the FAA of similar deficiencies in several of its safety recommendations; e.g., Safety Recommendations A-83-3 through -7 regarding Cessna airplanes that have flexible, rubberized bladder-type fuel cells in their wings. More importantly, the Board's evaluation of such fuel cells also disclosed that the deficiencies noted could be effectively resolved. For example, the Safety Board in Safety Recommendation A-83-6 recommended that the FAA:

	The FAA, in response to this and other Safety Board recommendations regarding Cessna bladder-type fuel systems, issued Airworthiness Directive (AD) 84-10-01. However, the Safety Board believes that the AD does not provide an adequate, reliable means for positive detection and/or elimination of water in the fuel. Some maintenance personnel who have carried out the provisions of the AD have expressed serious doubt as to its effectiveness. As more airplanes comply with the AD, there is increasing evidence to substantiate this belief; i.e, the continued occurrence of water-in-fuel accidents despite AD compliance such as those at Basile, Louisiana, on November 22, 1984, involving a Cessna 182 (N1857X); at Elmonte, California, on January 5, 1985, involving a Cessna 182 (N58816); and at Cold Foot, Alaska; on July 19, 1984, involving a Cessna U-206 (N3948G).

	While AD 84-10-01 may partly alleviate the water-in-fuel problem, we believe that installation of a water separator (increased capacity fuel strainer) and quick drains at the low point of the fuel system should be required in airplanes affected by this AD. Such a water separator, available for installation on Cessna Model 180 and 182 airplanes, has already been certificated by the FAA through issuance of Supplemental Type Certificate (STC) SA-2628NM. The water storage/collection capacity of the separator (1 qt) is not likely to be exceeded, particularly in cases where AD 84-10-01 has already been complied with. In fact, compliance with AD 84-10-01 or an equivalent procedure might be considered a desirable prerequisite to such an installation. Therefore, an additional requirement by the FAA to have water separators installed would be logical, feasible and acceptable. The Safety Board will continue its efforts to persuade the FAA to take such positive action to address the water-in-fuel safety problem evident in the Cessna model airplanes.

	Further, the number of fuel system deficiencies discovered by the Safety Board in recent years would seem to support a continued, selective testing of fuel systems of all general aviation airplanes. In fact, the Safety Board believes that the implementation of actions such as those proposed in safety Recommendation A-83-6 regarding Cessna airplanes and the related, continuing development of water separators/collectors, etc., might be applicable and effective in connection with existing fuel system deficiencies in other makes and models of airplanes. Therefore, while problems with general aviation fuel systems merit concern and further remedial action needs to be taken by both the FAA and the manufacturers, the Safety Board remains optimistic regarding the ultimate resolution of these fuel system problems. However, the Safety Board, unlike the FAA, is primarily an investigative agency and has no direct authority regarding aircraft certification. Therefore, the Safety Board's evaluation of fuel system deficiencies is derived largely from its accident/incident investigations and/or analysis of accident data.

	The Safety Board is most appreciative of the time and effort you have expended toward improvement of general aviation fuel system safety. The Board would be pleased to evaluate any information you may wish to share with us regarding existing water-in-fuel problems, new investigative techniques regarding this subject, or development/testing of fuel system water separators. Therefore, I have asked Mr. Paul Alexander of the Safety Board's Bureau of Technology (telephone No. (202) 382-6654) to meet with you for further discussion of this matter.