ENSTROM F-28F/280F SERIES MAINTENANCE MANUAL
Rev.
7
MM-9-25
Aug
22/16
E.
Main Rotor Hub – Assembly (See Figure 9-3)
WARNING: Use extreme caution when removing or installing the blade and grip
assemblies to prevent from injuring personnel.
WARNING: Use protective gloves when handling heated parts.
NOTE: The upper hub plate has helicoil inserts in the outer bosses for the
walking beam mount brackets. The lower hub plate bosses are solid.
(1) Heat the upper hub plate (14) and the lower hub plate (17) to approximately
250°F/121°C.
(2) Place the lower hub plate on 2" X 4" wood blocks. Lubricate the bearing bores with
MIL-PRF-81322.
NOTE:
Ensure the DU washers have been installed on the U-blocks with the
chamfered side facing the hub plates. The DU washers must be seated
in the recessed area of the hub plate.
(3) Install the U-block (universal block) assemblies (15) into the bearing bore of the hub
plate with the threaded notched end of the U-blocks down (3 places).
(4)
Place the spacer (16) on the lower hub plate and align the bolt holes.
NOTE:
Ensure the DU washers are seated in the recessed areas of the upper
hub plate.
(5) Lubricate the bearing bores of the upper hub plate and install the upper hub plate
onto the U-blocks.
NOTE:
The dowel pins must be installed until slightly recessed from face of
hub plate surface.
(6) Lubricate the dowel pins (13) and tap pins into the center hole of the 3-hole bolt
pattern (3 places).
NOTE:
The upper spline adapter has the wider flat surface on the top side of
the splines while the lower adapter has a rib extending from the lower
end of the splines.
CAUTION: When installing spline adapters, the phasing marks on top of the
splines must align with one of the walking beam mount brackets (3).
Using a felt marker, mark a line on outboard edge of hub plate in line
with spline phasing marks to aid in the alignment when installing
lower spline adapter.
UNCONTROLLED COPY WHEN DOWNLOADED OR PRINTED
Visit www.enstromhelicopter.com for instructions to order an original manual and to register for email notification of updates.