Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NE-07-30
April 19, 2007
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts you,
owners, operators, pilots, mechanics, and certificated repair
facilities of all Sikorsky Aircraft Model S-61 helicopters to restrict
from further flight any S-61 main rotor blade that has an indication
from the Blade Inspection Method (BIM®) system. This restriction is
to continue until the cause of the indication is determined and
corrected. We are issuing this SAIB because we have been notified of
the determination of a fatigue crack in a blade retrieved from a fatal
accident of an S-61 helicopter.
Background
The FAA issued airworthiness directive (AD) 74-20-07 R5 that became
effective September 26, 1984. This AD applies to the main rotor Visual
BIM® and Cockpit BIM® systems of S-61 helicopters. If the blade
is equipped with only the Visual BIM®, the pressure indicators must
be checked every 3 hours time-in-service. If a Cockpit BIM® is
installed, the electrical circuit must be tested every 3 hours
timein-service. The 3-hour interval allows sufficient time to comply
with instructions in the Rotorcraft Flight Manual after an in-flight
BIM® indication. This interval was based on the assumption that the
spar cracks immediately after the last check or test, which causes
leakage of internal pressure.
Note: FAA AD 85-18-05 R2 applies to Sikorsky S-61 main rotor
blades for helicopters used for more than six repeated external lifts
per hour. The BIM® inspection intervals are more restrictive for
these operations.
AD 74-20-07 R5 requires that each blade with any black or red
indication visible in the Visual BIM® blade pressure indicator, or
whose transducer of the Cockpit BIM® activates the cockpit warning
light is considered to be unsafe. Any such blade is restricted from
further flight until the cause of the indication is determined and
corrected in accordance with the procedures given in Sikorsky Service
Bulletin No. 61B15-6P or later FAA-approved revision (or Maintenance
Manuals SA 4045-80 and SA 4045-101).
Sikorsky Aircraft Corporation issued Safety Advisory SSA-S61-06-002,
dated October 20, 2006, to emphasize the need to follow flight manual
and maintenance manual procedures. The advisory carried the following
warning:
WARNING
Failure to follow established technical directives and publications
during inspection, maintenance and repair of main rotor blades equipped
with BIM systems could result in spar damage remaining undetected. Main
rotor blade failure will result in loss of control of the helicopter,
either on the ground or in the air, and subsequent loss of life and
property.
Recommendation
We remind all owners and operators of Sikorsky S-61 helicopters that
any BIM indication should be viewed as a spar failure of that blade
and, as stated in FAA AD 74-20-07 R5AD, that blade should not be flown
until the cause of the indication is determined and corrected.
For Further Information Contact
FAA Contact; Richard Noll, Aerospace Safety Engineer, FAA Boston
Aircraft Certification Office, ANE-150, 12 New England Executive Park,
Burlington, MA 01803; (781) 238-7160; email: dick.noll@faa.gov
For Service Letter Information Contact
Sikorsky Aircraft Corporation Contact: Sikorsky Customer Service
Engineering Desk at 1-800 Winged-S or E-mail: sikorskywcs@sikorsky.com
or Phone: (203) 416-4299.