Page 41 - EAA78.Newsletter.Archives.(February.2017-July.2021)

CHAPTER CHATTER, EAA Chapter 78 5

Contaminated fuel brings down Luscombe When Should You Use Trim?

The flight instructor reported that, during the initial
climb for the instructional flight with the student
pilot/owner at the controls of the Luscombe 8A, the
engine began to lose power.

The flight instructor assumed the controls and
attempted a forced landing on a road in a residential
area near Mount Dora, Florida.

During the forced landing, the left wing hit a tree, and
the airplane then came to rest upright, which resulted
in structural damage to the airframe.

During the post-accident examination, dark, granular
sediment was found inside the fuel tank, and it was of
sufficient quantity to interrupt fuel flow to the engine. When should you trim in flight? It's a question we get asked quite a bit.
Here's what you should know.
The airplane had been stored outside. It could not be
determined how, or when, the granular contamination
was introduced into the fuel tank.
First Off, What Does Trim Do?
An examination of the engine and fuel system revealed
evidence of some leakage around the carburetor, and
the cylinders around the exhaust valves showed
signatures consistent with operation at high exhaust Trim Holds Airspeed. If you trim for a speed and
gas temperatures.
let go of the yoke, your plane will keep flying at
Examination of the fuel tank revealed that it contained that speed, regardless of power setting. If you trim
automotive gasoline.
and change your power, your plane will pitch up or
The student pilot believed that the use of auto gas was
permitted, however, no supplemental type certificate down to maintain your trimmed speed. Trim for
(STC) for the use of auto gas existed, and the airplane climb speed, let go, and you'll maintain climb
was not placarded for auto gas use. The auto gas also
might have contained ethanol, which was not permitted speed. Trim for cruise, let go, and it'll maintain
with or without an STC for auto gas use.
cruise speed. Trim for final approach speed, let
Probable Cause: Excessive particulate contamination go, and you'll maintain final approach speed. The
in the fuel tank, which resulted in the interruption of the
fuel flow to the engine and a partial loss of power. The list goes on. Trim holds airspeed.
source of the contamination could not be determined
based on the available information. That's how trim works in a perfect world. In reality,
you might have to continue making small power,
NTSB Identification: ERA15LA265
pitch, and trim adjustments to maintain attitude

Published as an educational tool, it is intended to and speed.
help pilots learn from the misfortunes of others.