MD Helicopters CSP-900RMM-2, Servicing And Maintenance

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CSP − 900RMM − 2 MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 5
Revision 25
53-20-00
C. Tub Shell Assembly
(Ref. Figure 3)
The tub shell assembly is fabricated from
multiple composite detail parts joined together
by bonding or rivets.The primary components
included in this assembly are the tub shell, the
left and right keel beams, and the fuel cell
support ribs. Secondary components include
the cockpit and cabin sills, tub shell longerons,
fuel cell liner attachment angles, lower door
track pockets, and miscellaneous support
angles.
Tub Shell −
The tub shell is a primary
structural component and is the load bearing
skin of the lower section of the fuselage.
The sides of the tub shell are fabricated as a
composite sandwich panel that is typically two
ply outer and one ply inner graphite/epoxy
skins cocured with a Nomex honeycomb core.
In areas in which secondary attachment of
additional components will occur, the honey­
comb core is tapered and additional reinforce­
ment plies of graphite/epoxy are inlaid. The
center section between LBL 24 and RBL 24 is
typically three ply graphite/epoxy solid
laminate. In areas in which secondary
attachment of additional components occur,
additional reinforcement plies of graphite/
epoxy are inlaid. In areas in which secondary
attachment of metallic components occurs, a
barrier ply of fiberglass/epoxy is cocured to the
surface of the respective skin. On the exterior
surface of the tub shell a barrier ply of
fiberglass/epoxy and a ply of Astrostrik
is
cocured to the panel.
Fuel Cell Support Ribs −
The fuel cell support
ribs are the primary structural components
that support the loads in the vertical direction
produced by the fuel in the fuel cell. Six fuel
cell support ribs are positioned laterally
between the keel beams, and are located at FS
166.50, FS 176.60, FS 190.25, FS 199.20, FS
209.90, and FS 220.20. The ribs are mechani­
cally fastened to the keel beams by means of
auxiliary cleats or angles.
Early Configuration - The ribs are secondarily
bonded to the tub shell.
Current Configuration - Fuel cell support ribs
are riveted to the tub shell.
All fuel cell ribs are fabricated as composite
sandwich panels, that utilize multiple ply
graphite/epoxy skins cocured with Nomex
honeycomb cores. The honeycomb core
terminates at the integral attachment flanges
which are monolithic laminates.
Auxiliary Components −
The auxiliary
components, such as the cockpit and cabin
sills, tub shell longerons, fuel cell liner
attachment angles, and the lower door track
pockets are secondary structural components.
These auxiliary components are all composite
monolithic laminates utilizing multiple plies of
graphite/epoxy.
The primary function of the cockpit and cabin
sills are to provide for attachment of the
cockpit and cabin compartment floor panels.
The function of the tub shell longerons is to
provide stiffening of the tub shell. The function
of the fuel liner attachment angles is to
provide provisions for attachment of the fuel
cell liner. The primary function of the door
track pockets is to provide attachment of the
forward ends of the lower door tracks for the
cabin doors.