Bird Strike Resistant
Windshield Contributed To Helicopter Crash
December 1, 2010 - The National Transportation Safety
Board released a final report on a fatal crash involving
a transport-category helicopter caused by a bird strike.
The Board said the lack of requirements for bird
strike-resistant windshields contributed to the crash,
and called on the FAA to develop such requirements.
January 4, 2009, a dual-engine Sikorsky S-76C++
helicopter (N748P), registered to and operated by PHI,
Inc., crashed into marshy terrain near Morgan City,
Louisiana approximately 7 minutes after takeoff from
Amelie, Louisiana, on a charter flight to an oil rig in
the Gulf of Mexico. Both pilots and 6 of the 7
passengers were killed in the crash.
The aircraft had reached level cruise flight at 850 feet mean sea level and 135 knots when the cockpit voice recorder recorded a loud bang, followed by sounds consistent with rushing wind and a power reduction on both engines. The aircraft crashed several seconds later.
and other bird debris were collected from the canopy and
windshield of the aircraft. Laboratory analysis identified the
remains as coming from a female red-tailed hawk; the average
weight of such a bird is 2.4 pounds. The investigation revealed
that the impact of the bird on the canopy just above the
windshield near the engine control quadrant likely jarred the
fire extinguisher T-handles out of their detents and moved them
aft, pushing both engine control levers into or near the flight
idle position, reducing fuel to both engines. The pilots were
probably disoriented from the broken windshield and rushing air
and were unable to react in time to maintain control of the
helicopter was originally equipped with laminated glass
windshields that complied with European bird-strike resistance
standards. PHI replaced the windshields with lighter weight,
aftermarket cast acrylic windshields that did not have any
bird-strike resistance standards.
when the S-76 was certificated, there were no bird-strike
requirements. Currently, 14 Code of Federal Regulations 29.631
(in effect since August 8, 1996) states that, at a minimum, a
transport-category helicopter, such as the S-76C++, should be
capable of safe landing after impact with a 2.2-pound bird at a
specified velocity, this requirement includes windshields.
Current FAA requirements for transport category helicopter
windshields also state that ?windshields and windows must be
made of material that will not break into dangerous fragments.?
About 4 months
after this accident, Sikorsky issued a safety advisory to all operators
of the S-76C++ regarding the reduced safety of acrylic windshields (both
cast and stretched) compared to the helicopter?s original windshield.
According to the advisory, the S-76C++?s laminated glass windshield
demonstrated more tolerance to penetrating damage from in-flight impacts
(such as bird strikes) compared to acrylic windshields.
concern in the safety advisory that the presence of a hole through the
windshield, whether created directly by object penetration or indirectly
through crack intersections, may cause additional damage to the
helicopter, cause disorientation or injury to the flight crew, increase
pilot workload, or create additional crew-coordination challenges. The
investigation revealed that, following this accident, PHI is replacing
all of the windshields in its S 76 helicopters with windshields that
meet European bird-strike standards.
Based on main
rotor speed decay information provided by Sikorsky, the accident flight
crew had, at most, about 6 seconds to react to the decaying rotor speed
condition. Had they quickly recognized the cause of the power reduction
and reacted very rapidly, they would likely have had enough time to
restore power to the engines by moving the ECLs back into position.
However, the flight crewmembers were likely disoriented from the bird
strike and the rush of air through the fractured windshield; thus, they
did not have time to identify the cause of the power reduction and take
action to move the ECLs back into position.
helicopter was not equipped with an audible alarm or a master warning
light to alert the flight crew of a low-rotor-speed condition. An
enhanced warning could have helped the accident flight crew quickly
identify the decaying rotor speed condition and provided the flight crew
with more opportunity to initiate the necessary corrective emergency
actions before impact.
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