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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 View images from this test in 1024x768
resolution or in 800x600
resolution. Cessna 152 Tank Test Performed December 4, 2002 View images from this test in 1024x768
resolution or in 800x600
resolution. 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.
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?
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