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1. 05:00 PM - N62DN (DLM)
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I came across another couple of possibilities when I received this:
(1)
On November 16, 2013, a Piper PA-28-140 lost engine power shortly after
takeoff and crashed, resulting in a destroyed aircraft and a seriously
injured pilot. Why? Read on.
You are probably very familiar with the air ducts commonly referred to as
"SCAT," "SCEET," "CAT," and "CEET." You may have replaced some on the
aircraft engines you have worked. You might even keep a ready supply on
hand. Although we are not going to go into detail about each duct here, we
do caution you to ensure that the one you are using is acceptable for the
particular application intended. Beware! Although it "looks like a duct,"
"feels like a duct," or "fits like a duct," it may not function like the
"approved" duct for your specific job.
Investigation revealed that the "SCAT" duct installed as a carburetor air
inlet duct on the mishap PA-28-140 did not meet the specifications of the
air duct authorized and provided by Piper. The duct COLLAPSED, thereby
cutting off air flow to the engine.
An approved Piper inlet duct is engineered and designed to operate in a
vacuum of -12 inches of HG (mercury), at temperatures between -65 to +500
degrees Fahrenheit. The wire supporting the duct is .048 inches in diameter.
Although the collapsed duct had the correct inside diameter, the wall
thickness was thinner and the wire size was several thousandths less than
the Piper duct.
We believe that "off the shelf" ducts may be being used as a normal
replacement part instead of the authorized Piper carburetor air inlet duct.
We say this because there have been no approved carburetor air inlets ducts
ordered from Piper since 1999 even though the FAA registry indicates there
are over 5000 registered PA-28-140 aircraft.
What can you do to help prevent another accident? Well, if applicable, check
your fleet of PA-28-140 aircraft. Pass the word to the owners and operators
who fly these aircraft, as well as your AMT colleagues that maintain these
aircraft. The number one thing you can do is always research the
manufacturer's manuals to validate you are using approved replacement parts.
Finally, never replace components based on what was previously installed.
Trust, but verify.
See Maintenance Safety Tip-1209, "Who do YOU Trust?" published August 2012.
<http://www.faasafety.gov/SPANS/noticeView.aspx?nid=4046>
http://www.faasafety.gov/SPANS/noticeView.aspx?nid=4046.
(2) There are SBs and ADs on the carburetors (Precision Air Motive I
believe) . The carb float sinks and fails to control fuel to engine. Too
much fuel will not light; perhaps a mixture at almost idle cutoff may cause
a light.
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