Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
AIR-21-19
November 29, 2021
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin alerts owners,
operators, and maintenance personnel of an airworthiness concern on MD
Helicopters Inc. (MDHI) Model 369D, 369E, 369F, 369FF, 500N, and 600N
with Colorado Helicopters, Inc. Supplemental Type Certificate (STC)
SH5230NM Side Pull Hook Assembly installed.
At this time, the airworthiness concern is not an unsafe condition that
would warrant airworthiness directive (AD) action under Title 14 of the
Code of Federal Regulations (14 CFR) part 39.
Background
The Federal Aviation Administration (FAA) became aware that the
breakaway pin installed in the breakaway swivel of the side pull hook
link installation could be replaced with the wrong pin or bolt prior to
operations (See Figure 1 below). The hook link installation is
certified for a maximum pull load of 1,900 pounds and is safeguarded by
the calibrated breakaway pin connecting the two pieces of the swivel
(The swivel is shown assembled in Figure 1). If the hook link
installation is overloaded, the breakaway pin is designed to shear and
allow the load line to fall away without upsetting the helicopter.
Installation of other than the approved breakaway pin could result in
helicopter damage, upset, and even loss of control if the maximum pull
load of 1,900 pounds is exceeded. The swivel is installed in between
the hook link assembly, which attaches to the helicopter, and the line
attached to the load. The pin is approximately one inch long with one
end painted GREEN (not BLUE) and fills the hole through the swivel. The
pin has two smaller diameters allowing it to break in shear at a
specified load. It does NOT contain any threaded features and does not
protrude from the swivel. The pin is held in place with a steel
retaining ring installed in a groove around the circumference of the
swivel. Visual verification of the shear diameters and lack of threads
is accomplished by removal of the steel ring and pin. If further
verification is needed, a maintenance mechanic may measure the shear
diameter (the smallest diameter of the pin in two places) to be .149
inch +.000/-.003 inches, not larger. ILLUSTRATION (Figure 1)
Recommendations
The FAA recommends that all pilots of the affected aircraft listed in
the introduction of this SAIB inspect the breakaway pin for correct
color code (GREEN) and general appearance (shear diameters present, no
threads) immediately before any side pull operations. If the pin
matches the description above and has no signs of damage, reinsert the
pin and reinstall the retaining ring prior to flight. If the pin does
not match the description above, or shows signs of damage, it should be
replaced with pin part number 91106-018 prior to the next side pull
operation.
The STC Design Approval Holder, Colorado Helicopters, Inc., further
recommends that forward airspeed be limited to approximately 10 knots
when utilizing the side pull hook. Higher airspeeds can result in loads
in excess of 1,900 pounds, nuisance breakaway pin failures, and hazards
to persons on the ground when the load is unexpectedly released.
For Further Information Contact