INFORMATION LETTER #2000-1
S-61/H3/Agusta AS-61/Westland Sea King/Commando
inspection of 40 main rotor blades manufactured by Agusta, Sikorsky
and Westland, we have isolated the following problem.
We have recently completed inspection on 10 each Westland manufactured
main rotor blades part number, WD4529-00002-047. By visual inspection
and X-ray, we have found that 82 pockets out of 230 have severe internal
corrosion. The majority of this corrosion is on the ribs that support
pockets are manufactured in several pieces, the skin, internal ribs
and the back wall. There are a number of pocket configurations used
on this blade, some have five internal support ribs and the others
have eight ribs. The pocket skin, ribs, back wall and adhesive are
then assembled in an alignment fixture and heated to cure the adhesive.
Prior to assembly, all parts are heat treated for strength and anodized
for corrosion resistance.
Westland manufactured pockets we have inspected revealed severe corrosion
present on an abnormal amount of support ribs. Some interior skin has
corrosion present, but in small amounts, the back wall has shown no
corrosion problem. This may be a problem in the process used to manufacture
the ribs or in the anodize plating process used.
field operations many of these pocket may be found by inspecting each
pocket for rib integrity by applying external pressure on the pocket
skin, by applying light hand pressure, to determine if the ribs are
2. ABS received 10 each Agusta main rotor blades that were stored in a barge
for in excess of 100 days. We have found an average of 12 pockets, per assembly
of Agusta manufactured rotor blades that were replaced due to pocket internal
and external corrosion. Out of the 10 blades inspected, four were removed from
service due to spar corrosion beyond allowable limits and six were repaired
and returned to the customer. With proper storage, handling and shipping the
potential for this problem would have been minimized.
3. Over the past 5 years we have replaced a very small number of Sikorsky manufactured
pockets due to internal corrosion.
cannot overly stress the need to properly maintain, store, handle and
ship your rotor blades as repairs can become quite expensive. Although,
the severe corrosion has been isolated to the Westland manufactured
pocket assemblies and the Augusta blades that are improperly stored,
this problem will continue to increase operational cost if not addressed
is just one example of a corroded pocket removed from a Westland Sea
King main rotor blade. ABS has replaced many that are corroded to a
grater degree and many to a lesser. This pocket was found during a
visual inspection but many that have not reached this stage of corrosion
can only be found by means of X-ray or fluoroscope. Approximately 80%
of the pocket replaced on a Westland manufacture blade will be due
to corrosion inside the pocket. Sikorsky and Augusta manufactured pockets
have not experienced this specific problem, if they are replaced due
to corrosion it is mostly exhibited on the skin surface but very seldom
on the internal ribs. If the ribs are corroded on the Sikorsky or Augusta
rotor blade there is always additional corrosion found throughout the