Recommendation
Affects Approximately 400 Airbus Planes On Friday, the National Transportation
Safety Board urged the Federal Aviation Administration to order inspections of
the inner skin of the composite rudder surfaces of certain Airbus A300 series
airplanes.
The safety recommendations -- one of which is classified as
urgent by the Safety Board -- address a safety issue identified during the investigation
of damage found during an inspection of a rudder from a Federal Express A300-600
airplane last November. The Board noted that this incident might have applicability
to a more serious rudder separation that occurred last year, involving a passenger
airliner.
"The Board believes that this urgent recommendation, if
acted upon quickly, will go a long way to prevent a catastrophic failure of the
rudder," NTSB Acting Chairman Mark V. Rosenker said.
On March 6, 2005,
an Airbus A310-300, operated by Air Transat as flight 961, experienced an in-flight
separation of its rudder shortly after departure from Juan G. Gomez International
Airport in Varadero, Cuba. The flight returned to Varadero, where it landed uneventfully.
Upon landing, the crew discovered that most of the airplane's rudder had separated
in flight with only the bottom closing rib and the spar between the rib and the
hydraulic actuators remaining.
Following the Air Transat accident -- which
is being investigated by Canada with the assistance of the NTSB -- Airbus issued
a mandatory All Operator Telex (AOT) A300-55A6035 specifying a one-time rudder
inspection for all A-300 series airplanes equipped with premodification 8827 or
40904 rudders.
On March 28, 2005, the FAA issued Airworthiness Directive
(AD) 2005-07, requiring operators to perform the inspections specified in the
AOT.
American Airlines and Federal Express (the only U.S. operators of
these airplanes) complied with the AD.
On November 27, 2005, the rudder
on an Airbus A300-600 airplane operated by Federal Express was damaged during
routine maintenance. To assess the extent of the damage, the rudder was shipped
to the manufacturer's facility and examined. In addition to the damage that occurred
during maintenance, the examination found a substantial area of disbonding between
the inner skin of the composite rudder surface and the honeycomb core, which is
located between two composite skins.
Further examination of the disbonded
area revealed traces of hydraulic fluid. Hydraulic fluid contamination between
the honeycomb skin and the fiberglass composite skin can lead to progressive disbonding,
which compromises the strength of the rudder. Tests on the damaged rudder also
revealed that disbonding damage could spread during flight.
The investigation found that the areas specified in the
AOT did not include the areas in which the disbonds were found on the incident
rudder. Further, it was determined that tap tests on the external surfaces of
the rudder likely would not have disclosed the disbonding of an internal surface.
On March 2, 2006 Airbus issued AOTs notifying operators of applicable A300
series airplanes that large disbonds between the rudder's inner skin and the honeycomb
core could go undetected, and providing guidance for inspecting the rudders. The
Safety Board is recommending a more stringent compliance time than specified in
the AOT and also requesting that FAA make the inspections mandatory.
More
recent examinations have disclosed that hydraulic fluid can exist along the edges
of the rudder's inner surface along with an accompanying area of substantial disbonding
and that the inspection specified in the AOTs cannot detect the presence of the
hydraulic fluid or the disbonding along the edges.
Therefore, the Safety
Board is recommending that the FAA require that all operators of Airbus A-300
series airplanes immediately (possibly before further flight) comply with four
Airbus All Operators Telexes dated March 2, 2006. Any disbonding to the rudder
skins that occurs in the presence of hydraulic fluid contamination should be repaired
or the rudder should be replaced as soon as possible, well before the 2, 500 flights
specified in the AOTs. (A-06-27) This is an urgent recommendation.
The
NTSB further recommended that the FAA establish a repetitive inspection interval
for Airbus premodification 8827 rudders until a terminating action is developed.
The interval should be well below 2,500 flights. (A-06-28)
It is estimated
that these recommendations concern about 400 aircraft in Airbus's worldwide fleet.
Read
The Recommendation Letter:
