The Australian Transport Safety Bureau (formerly the Bureau of
Air Safety Investigation) recommends that the US Federal Aviation
Administration review Rolls Royce RB211-524D4 engine cold stream
nozzle inspection criteria to minimise the possibility of failure
during operation.
This memo is in response to Federal Aviation Administration
(FAA) Safety Recommendations 00.010 and 00.011. The recommended
action is to prevent conditions that caused an uncontained cold
stream nozzle failure in a Rolls-Royce plc RB211-524D4 engine
model. Cold stream nozzle failure is attributed to cracking and
delamination of the acoustic liner at the top right side of the
cold stream nozzles resulting in departure of nozzle sections from
the engine. The failure resulted in sections of the cold stream
nozzle departing the engine and impacting a number of the aircraft
wing leading edge panels and the number 1 flap fairing.
Recommendation 00.011: The Australian Transport Safety Bureau
(formerly the Bureau of Air Safety Investigation) recommends that
"the U.S. Federal Aviation Administration review Rolls Royce
RB211-524D4 engine cold stream nozzle inspection criteria to
minimize the possibility of failure during operation."
ECO Response: The FAA agrees with Recommendation 00.011. The United
Kingdom Civil Aviation Authority (CAA) recently notified the ECO
concerning a recent event in which an RB211-524D4 powered Boeing
747 suffered the loss of a section of cold stream nozzle in flight.
As a result of the cold stream nozzle failure, the CAA has issued
Airworthiness Directive (AD), 005-01-2000 in conjunction with
Rolls-Royce plc (RR) Mandatory Service Bulletin RB.211-78-C955. The
AD requires borescope inspection of the cold stream nozzle
longitudinal flange forward and aft of the forward Z-section
circumferential stiffener position for cracks. AD mandatory
inspection compliance requirements are specified as no later than
400 flight hours or 100 flight cycles, whichever is the sooner,
from the issue date of the Mandatory Service Bulletin, which is
dated January 31, 2000.
The ECO is currently reviewing the available data concerning cold
stream nozzle failures. The FAA will issue an AD in accordance with
the requirements of the CAA AD. The Engine and Propeller
Directorate will forward the AD to AAI when it is issued.
