Small Airplane Directorate
601
E. 12th Street
Kansas City, MO 64106
Home Documents Images
Message Board
(Use
your browser's back button to return to the page that you were previously
viewing.)
|
|
Small Airplane Directorate |
|
FEB 10, 1994 |
|
|
|
Messrs. Norman L. Horton and Mr. Jerry L. Wells |
|
|
|
Dear Mr. Horton and Mr. Wells: |
|
|
|
The following information is provided in response to your January 5, 1994, letter to Mr. Hinson, Federal Aviation Administration Administrator, wherein you expressed concern about contamination of the fuel system caused by water that could be trapped in the aft inboard corner of each tank. I have been asked to respond to you. |
|
|
|
There have been 16 accidents since 1975 involving certain Piper PA-23 series airplanes, where it was believed that water in the fuel caused engine stoppage. Airworthiness Directive (AD) 90-23-18, Amendment 39-6782 was published in the Federal Register on November 7, 1990. After issuing AD 90-23-18, the Federal Aviation Administration (FAA) discovered that there was an error in the AD, in that it required both the installation of dual drain kits and a revised fuel system draining procedure in accordance with Piper Service Bulletin (SB) No. 827A. The AD should have only required one of these actions. In addition, the Aircraft Owners and Pilots Association (AOPA) petitioned the FAA to withdraw the fuel system modification requirement from AD 90-23-18. In its judgment (and that of many of the airplane owners), the AOPA attributed the water-in-the-fuel problem to poor maintenance rather than an inadequate design. From the evidence presented by the owners and the AOPA, the probable cause of water entering the fuel cells was due to poorly maintained fuel filler caps and doors. The FAA has previously addressed the fuel filler cap problem through AD 88-21-07 R1. |
|
|
|
The FAA re-examined its position on this AD, and suspended the effectiveness of AD 90-23-18 on December 13, 1990. After this suspension, over 50 comments from the owners of Piper PA-23 series airplanes were received. The FAA issued an advance notice of proposed rulemaking (APRM) on April 24, 1991, to provide an opportunity for the general public to participate in the decision whether to initiate further rulemaking. There were 188 responses to the ANPRM, with the vast majority coming from the owners and operators of PA-23 series airplanes. A majority of the commenters felt that parts of AD 90-23-18 were not justified, and that the AD should be removed or replaced. These commenters stated that good preflight fuel drainage procedures and maintenance are required to minimize water in the fuel. |
|
|
|
The FAA carefully reviewed all the comments, and all additional available information. A determination was made that the preflight fuel drainage procedures that were required by AD 90-23-18, and maintenance of the fuel caps and doors that is required by AD 88-21-07 R1, will prevent water-in-the-fuel problems. The FAA determined that the modification requirements of AD 90-23-18 are not necessary. The FAA has also determined that the preflight fuel draining procedures on the Piper Models PA-23, PA-23-150, and PA-23-160 airplanes should not be required if the airplanes have been modified by the installation of a dual fuel drain kit in accordance with the instructions of Park II of Piper SB No. 827A, dated March 4, 1988. |
|
The FAA issued Notice of Proposed Rule Making (NPRM), published January 27, 1992, which incorporated the suggestions from the comments received as a result of the ANPRM. Eighteen comments were received. Fourteen of the commenters agree that the use of standard inspection and maintenance procedures, as specified in the proposed AD, would eliminate water-in-the-fuel problems on certain Piper PA-23 series airplanes. |
|
|
|
Two of the commenters proposed the incorporation of airplane modifications to prevent or remove water in the fuel. These modifications were: (1) the installation of an inclinometer on the side of the airplane, and putting the airplane in a 2-degree nose-down attitude position when checking for water in the fuel after refueling; and (2) the incorporation of a drain in the reservoir around the fuel cap to drain any water that collects in this area. |
|
The other two commenters are against the proposed rule, and feel that an airplane design improvement is required to prevent water-in-the-fuel problems. |
|
The FAA did not concur that a design improvement, nor the modification referenced in the comments discussed above, were necessary in order to prevent water-in-the-fuel problems on certain Piper PA-23 series airplanes. Water can enter the fuel system on the affected airplanes through (1) condensation; (2) contaminated fuel; or (3) leaky fuel caps and door seals. The FAA determined that condensation is a small contributor to water-in-the fuel problems, and can be practically eliminated by promptly refilling all fuel tanks after each flight. Industry federal controls on aviation fuels minimize the likelihood of contaminated fuel. Therefore, the principle cause of water in the fuel for certain Piper PA-23 series airplanes is caused by improperly sealed fuel filler caps and ineffective door seals. The problems with fuel filler caps and door seals were addressed by AD 88-21-07 R1 for the affected airplanes. |
|
Based on an extensive analysis of all available information, including the comments discussed above, the FAA issued AD 92-13-04. AD 92-13-04 required the incorporation of paragraphs 1 through 5 of the Aircraft Systems Operating Instructions that are contained in Part 1 of Piper SB No. 827A, dated November 4, 1988, into the Owner Handbook and Pilots Operating Manual. In addition, the FAA added a note that recommends precautions that could be taken in the event water exceeding one tablespoon is found in the fuel during repeated fuel draining after wings are rocked, or the airplane has been put in nose-down attitude. If water continues to be found, the drainage and inspection of the tanks is recommended. |
|
AD 92-13-04 only applied to PA-23-150 and -160 models. The PA-23-235 and -250 were not included in the AD, since the Aztec models have individual line drains for the main and auxiliary tanks in addition to the gascolator drain. There have been no other accident reports associated with water-in-the-fuel on Piper PA-23 series aircraft since the issuance of AD 92-13-04, effective August 21, 1992. |
|
Additional the National Transportation Safety Board supported the adoption of AD 92-13-04 in its letter of April 17, 1992. |
|
Thank you for your concern for aircraft safety. |
|
Sincerely, Barry D. Clements |
Home Documents Images
Message Board
(Use
your browser's back button to return to the page that you were previously
viewing.)