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Testing a Cessna 150 Fuel Tank and a Cessna 152 Fuel Tank: Are the sump drains that are installed on these fuel tanks located at the corresponding tank's sump?




In the course of researching Cessna's integral wing tank design as documented here on the SumpThis web-site, Robert E. Scovill JR and others have reviewed many NTSB aircraft accident reports that involve general aviation aircraft. In addition to reviewing reports involving aircraft equipped with Cessna's integral wing tank, reports involving aircraft equipped with Cessna's 150 fuel tank and aircraft equipped with Cessna's 152 fuel tank have also been reviewed. Scovill's review of these latter reports lead him to include several of them in his petition to the NTSB dated July 31, 2001.

Scovill's petition to the NTSB recommends that the NTSB evaluate its procedures that were used to investigate the aircraft accidents listed in the reports contained in the petition. For these accidents, the recommendation encourages the NTSB to perform an evaluation that gives attention to Scovill's observation that matters related to the positive detection of fuel contamination may not have been considered. Ultimately, the NTSB gave little attention to the petition, but this outcome was expected even before the petition was drafted.

The preferred outcome of the petition desired that the NTSB fulfill the recommendations and reconsiderations given in the petition, but that didn't happen. What did happen is that the petition was placed in public record so that its contents are available as a reference that can be used by the public in its efforts to persuade the NTSB to include in its general aviation aircraft accident investigation procedures a process that establishes with high integrity whether or not a means for positive detection of fuel contamination existed during a preflight check for relevant aircraft accidents that the NTSB investigates. This process must consider aircraft design (such as the design of an aircraft's fuel tank) and required preflight procedures (such as taking a fuel sample or physically rocking an aircraft's wings).

To further document the petition's subject matter, Robert E. Scovill JR and Matt Taylor IA, Director of Maintenance, performed a test on a Cessna 150 fuel tank in November 2002 and performed a test on a Cessna 152 fuel tank in December 2002. These tests were performed to experimentally determine if each tank's sump drain is located at the corresponding tank's sump. Water was used as a heavier than fuel contaminant to locate each tank's sump. Then observations were made that visually determined the location of the water with respect to a tank's sump drain.

Pilot's who fly aircraft that have these types of tanks installed must take a fuel sample during a preflight check. A fuel sample is taken from a sump drain, so to be effective for its intended purpose, a sump drain must be located where fuel contaminates are located. Ideally, a tank's design will permit heavier than fuel contaminates to freely flow under the influence of gravity to a sump area. And ideally, a tank's sump drain will be located at this sump. Then a pilot who takes a fuel sample from such an ideal tank design can with certainty rely on a fuel sample as a means for positive detection of  fuel contamination. Thus, the tests performed on the Cessna 150 fuel tank and the Cessna 152 fuel tank were executed under simulated preflight conditions so that the results indirectly reveal the integrity of established preflight procedures as well as the integrity of each tank's design for use as a means for positive detection of fuel contamination.

For readers who are interested in the Cessna 150 model aircraft and the Cessna 152 model aircraft certifications, the TYPE CERTIFICATE DATA SHEET NO. 3A19 contains certificate data for both aircraft. This document can be used to compare the two aircraft models or to view specifications specific to each model. The document is available online in PDF format (file size is about 71kb). The 3A19 document can be obtained from the Federal Aviation Administration's Aircraft Certification Service Products and Services by navigating from its Home Page to the 3A19 document's download page. Alternatively, you can download the 3A19 PDF document from the SumpThis web-site by clicking here. Also, from adobe.com, you can download Adobe's free Adobe® Reader®.

Commentary and images of the tests performed on the Cessna 150 fuel tank and the Cessna 152 fuel tank are available here on the SumpThis website from the following links.




Cessna 150 Tank Test Performed November 14, 2002

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Cessna 152 Tank Test Performed December 4, 2002

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Other References:

October 29, 2003 Letter to the FAA FSDO Nashville: This letter dated October 29, 2003 alerts the FAA of suspected problems with the Cessna 150 fuel tank's and the Cessna 152 fuel tank's sump and drain design based on the November 14, 2002 and December 4, 2002 tests.

Scovill's Petition to the NTSB

Scovill's petition to the NTSB included aircraft accident reports from NTSB's aircraft accident database for the period 1983 to July 2001. The NTSB's online database includes aircraft accident reports from a data set for the period 1962 to 1981 and another data set for the year 1982. Again, to further document the petition's subject matter, several aircraft accident reports for the period 1962 to 1982 involving Cessna 150 model aircraft and Cessna 152 model aircraft have been categorized using some of the categorizes that are used in the petition for the period 1983 to July 2001. Indexes to each category for the period 1962 to 1982 are available from the following SumpThis web-page.

Index to NTSB aircraft accident reports for the period 1962-1982.










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