July-August 2022 - 44

HUMAN FAC TORS
The day following a change to the rotor blade control servo, the
craft encountered fatal loss of control, and impact into a canyon
wall. There were five fatalities. The control to the servo was not
properly attached and became disconnected during a routine
tour flight.
Reuse of a self-locking nut and absence of a locking pin were the
likely cause. The NTSB cited failure to have and follow maintenance
procedures; fatigue-related fitness for duty of the AMT
and inspector; and the importance of human factors training for
everyone in the organization. Read the accident report (NTSB/
AAR-13/01).
EMERGENCY RESCUE HELICOPTER: FLIGHT CONTROL
DISCONNECT ON AIRBUS DAUPHIN, 2020
This event had similarities to the helicopter event above (German
Federal Bureau of Accident Investigation, 2020). The emergency
rescue helicopter encountered a significant rotor control linkage
disconnect at liftoff. The craft rapidly descended, about a meter,
back to the runway with only minor damage to the tail rotor.
Upon post-accident inspection, a large bolt and castellated nut
were found on the floor of gear case cabinet. The aircraft had
flown nearly nine hours, after heavy maintenance, before the
parts disconnected.
Like the Sundance helicopter, there was no cotter pin found. The
found self-locking nut could be turned on to the bolt by hand. The
mechanics/engineers/inspector that completed the work were
highly experienced and recalled using proper locking techniques.
However, careful laboratory inspection proved that the cotter pin
was not used and the nylon in the locknut was worn out. Here is
the list of contributing factors recommendations from the report:
* Maintenance work where the screw fitting involved was loosened
and tightened again
* Use of a worn nylon stop crown nut with insufficient friction
torque
* Application of an insufficient torque of the crown nut
* Omission of a cotter pin protection of the crown nut
GPIAAF
Simulated Disposition of Aircraft During Initial Flight.
* Insufficient check of the work by the examiner
* Omitted check of the screw fitting of the flight controls during
the 10 flight hour/ 7-day inspection.
The excellent final report has extensive human factors discussion
and is interesting reading.
SMALL TWIN: ELEVATOR TRIM TABS INSTALLED
UPSIDE DOWN ON PIPER PA-31P NAVAJO, 2021
A Piper PA-31P Navajo, with just the post-maintenance airline
captain/pilot/owner on board, took off from Myrtle Beach, South
Carolina, on May 2, 2021. It was the first flight after an annual
inspection and painting of selected flight control surfaces.
Immediately after takeoff, the highly experienced airline captain/pilot/owner
told the control tower that he was having control
issues. Investigators immediately discovered that the elevator trim
tabs were installed upside-down and backwards (Flight Global
9/11/21). The usual questions about maintenance procedural compliance,
training/certification of mechanics and MRO, fitness for
duty, and interference/rush by the owner are likely contributing
factors. NTSB report is not published at press time of this article.
http://www.pentagon2000.com
July-August 2022

Table of Contents for the Digital Edition of July-August 2022
