Central Region
601 E. 12th Street
Kansas City, MO
64106
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Central Region |
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FEB 18 1988 |
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Messrs. Norman L. Horton and Jerry L. Wells |
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Gentlemen: |
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This is in further response to your letter dated December 14, 1987 and our letter of December 28, 1987, concerning fuel contamination in Piper PA-23 airplanes. |
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Our team of specialists reviewing this matter completed their investigation which included testing a privately owned PA-23 Apache airplane with the original main and auxiliary bladder cells installed. The team, which was made up of the Aircraft Certification engineering personnel and an FAA Airworthiness Inspector, concluded that it is possible to trap fluid, including water, in the PA-23 fuel cells in excess of the 3.3 ounce capacity of the fuel strainer. The undrainable fluid can be attributed to a low spot in the aft inboard corner of the main tanks and fluid surface tension plus bladder wrinkle caused by various conditions that are typically found in bladder-type fuel cells. |
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The team found what they thought may be an error in your video tape. The dimension measured from the aft portion of the main tank, where there is a drain hole for the bay area, to the floor must include the 7/8-inch thick rubatex pad that the tank rests on when comparing this dimension to the dimension measured from the center line of the fuel drain line to the floor. |
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However, the team was in general agreement with your observations although they did believe your results may have been magnified by the apparent error mentioned above. The team is currently evaluating the results of their tests and possible additional actions to improve the Piper PA-23 Apache fuel system. The team did not believe that installing drains at the aft inboard corner of the main tanks was a practical solution to the problem for economic reasons, and because only part of the entrapped fluid was found at this location. |
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One of the proposed actions being considered is an Airworthiness Directive (AD) to require compliance with Piper Service bulletin No. 340 concerning inspection of fuel cell vent and drain lines at every annual inspection. |
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We appreciate your suggestions and investigations. A further response to you will be made upon completion of the FAA review which should be on or before March 31, 1988. Should you have any more questions or need to discuss this matter further, please feel free to contact either myself or Mr. Robert Alpiser of my staff at (816) 426-6934. |
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Sincerely, Barry D. Clements, Manager |
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