Premium on Safety - Issue 45, 2022 - 10

LESSONS LEARNED
position to its east and offering a dry 12,000-foot runway. After
burning sufficient fuel, they moved the passengers to the forward
rear-facing seats and briefed them on the evacuation procedures.
Hydraulic pressure was confirmed to be normal with brake pressure
available. The pilots made a normal ILS approach to Runway 6,
touching down with 45 degrees of flaps at the lowest controllable
ground speed and holding the nose up as long as possible. The jet
came to rest on the runway, about 4,500 feet past the approach
end, with the nose gear still in its well. The passengers and crew
evacuated without injury through the main cabin door. As the
captain noted in his statement to the NTSB, " No additional or
different actions of flight crew could have prevented failure, or
resulted in a more favorable outcome. "
The missing pin that allowed the push rod
linkage to wrench out of the nose gear
actuator was just one of the thousands of
pieces that must be in place and correctly
secured for all the systems of any aircraft to
operate as designed.
Photographs taken by the responding FAA inspector documented
that the push rod linkage for the nose gear actuator was
disconnected from its attachment point. The castle nut, washer,
and split pin that should have secured the linkage were not found
in the wreckage, and the corresponding threads of the linkage were
deformed inwards. The matching bushing in the hydraulic actuator
was partially twisted from its seat, suggesting repeated unbalanced
pressures during the 124 cycles since the nose gear had been
10
removed, overhauled, and reinstalled the previous January. No other
inspections of the nose gear had been performed since.
Though the heavy maintenance contractor's job cards had been
checked and signed off by a quality assurance inspector, the NTSB
concluded that " it is likely that the split pin was not installed during
the installation of the nose landing gear following the overhaul, and
over the course of the 124 cycles...the nut and washer backed out. "
The accident's probable cause was therefore found to be:
Maintenance personnel's improper installation of the nose landing
gear assembly, which resulted in separation of the actuator arm and
the failure of a [sic] nose landing gear to lock into place.
After the airplane was removed from the runway, the nose gear
locked into place normally when the operator's maintenance staff
extended it by hand.
Details matter. A bad situation could have been made much worse
had two experienced pilots not put first priority on flying their
airplane, then systematically assessed their situation, identified the
most favorable landing site, and taken care to touch down under
control at the slowest safe speed and lowest safe weight. And the
missing pin that eventually allowed the push rod linkage to wrench
out of the nose gear actuator was just one of the thousands of
pieces that must be in place and correctly secured for all the systems
of even a small corporate jet to operate as designed. There's no
knowing how it came to be overlooked, but while no kingdom
was lost for the lack of a horseshoe nail, the absence of one small,
inexpensive part that could have been installed in seconds led to an
in-flight emergency and vastly disproportionate damage.
-David Jack Kenny is a freelance aviation writer and
statistician.
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