AOPA Pilot Magazine - February 2019 - 88

P&E

SAVVY MAINTENANCE

THE THROTTLE CABLE was found disconnected from the throttle bellcrank, and the

attaching hardware was gone.

fly the airplane to his shop so Rick could look
at it, assuring Sam that the airplane would be
safe to fly because it has two magnetos. Rick
explained that he was a certificated pilot and
had "done this many times."
The next day, Sam intended to fly the airplane to Rick's shop, but the engine still ran
rough on the right magneto, so Sam decided
to stay in the local traffic pattern and shoot
some touch-and-goes. On the second touchand-go, the engine seemed to sputter slightly
on takeoff. On the third touch-and-go, the
engine sputtered a couple of times, causing
Sam to decide to make a full-stop landing,
park the airplane, and investigate further.
Sam removed the top engine cowling
and was horrified to find that the ignition
leads on two cylinders had B-nuts that were
floating free and cigarettes (insulators) that
were partially backed out from the spark
plugs. He hand-checked the B-nuts on the
ignition leads for the other four cylinders
and found all of them to be loose and in the
process of backing off the plugs.
Sam phoned Rick to report what he had
found. Rick apologized and said he'd drive
to Sam's airplane the following week to fix
the loose B-nuts. In the meantime, Sam
noticed that the nosegear tire appeared to
be underinflated. He decided to inflate it
88 | AOPA PILOT February 2019

to the proper pressure, but discovered that
the valve stem was not accessible through
the wheel fairing access door because the
nosewheel had been installed backwards
with the valve stem on the wrong side. Sam
also noted that the dynamic balance weight
washers that had previously been installed
on the spinner were missing.
A week later, Rick met Sam at the airplane
to rectify the problem with the loose ignition
harness B-nuts. Sam brought the other discrepancies he'd found to Rick's attention and
asked him to correct these issues as well. Sam
gave Rick keys to the airplane and asked to
be notified when the work was finished. The
next day, Rick advised Sam that the airplane
was "good to go" and that he would "have no
problem flying it with his kids on board."
IT GETS WORSE

Sam started planning his first solo crosscountry but was still apprehensive about the
mechanical status of the airplane. A visiting
friend who was an experienced pilot offered
to fly the airplane with Sam to help restore his
confidence in the machine. They took off on a
short flight to a nearby airport. Approaching
their destination, the pilots throttled the
engine back to 21 inches of manifold pressure to slow the airplane during the descent.

Upon entering the traffic pattern, they throttled back further, but the engine did not
respond to the throttle inputs, and manifold
pressure remained at 21 inches. Attempts to
move the throttle in either direction now had
no effect on engine power. Sam's pilot friend
took control and reduced power by pulling
the mixture control and was able to land
without incident.
After landing, Sam removed the top
cowling and observed that the throttle cable
rod end was not connected to the bellcrank
on the throttle body. The clevis bolt and its
retaining nut and cotter pin were missing
and could not be located. Understandably,
Sam's faith in his airplane and mechanic
were badly shaken. Sam and his friend were
not injured, and the aircraft was undamaged. They were fortunate. Literally the
day before Sam told me his story, I had been
reading an NTSB probable cause report of a
fatal accident that was eerily similar.
It involved the May 2016 crash of a
Beechcraft Bonanza in Arizona. A flight
instructor was performing a post-maintenance test flight of the airplane following
the installation of a repaired carburetor, and
elected to use the flight to provide instruction to a private pilot who had requested a
checkout in the airplane. The private pilot
reported that the flight was initially normal,
but then the engine stopped responding to
throttle control. According to the private
pilot, the engine remained at idle power as
the airplane descended and struck trees in
a residential area. The flight instructor was
killed in the crash, and the private pilot suffered serious injuries.
Examination of the wreckage revealed
that the carburetor throttle cable was
detached from the throttle body linkage.
The bolt and castellated nut used to secure
the throttle cable to the linkage were found
lying separately in the engine cowling;
there was no evidence that a cotter pin had
been used to secure the nut on the bolt, as
required.
The NTSB determined the probable
cause of the accident was "the mechanic's
AOPA Pilot Magazine - February 2019

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