ENSTROM F-28F/280F SERIES MAINTENANCE
MANUAL
Rev.
7
MM-9-12
Aug
22/16
Table 9-1. Main Rotor Hub Assem
bl
y
– Inspe
ction
Part No.
Figure 9-3
Item #
Part Name
Inspection*
Serviceable Limi
ts*
Repair Limit
s
Repair or Action
28-1
428
0
(co
ntinue
d)
14
U
p
per
Hub
(co
ntinue
d)
Re
ce
sses for
the DU
washers parallel to the
uppe
r su
rfa
c
e
within .001
Damper bolt bushings
diameter .4995 to .5000
Thre
ad
s for walkin
g
bea
m
br
ac
k
e
ts
(cro
ssed or m
issi
ng).
Nicks, scrat
c
hes, or
c
o
rr
os
ion
Cra
c
ks
+
.0
0
05
+
.0
0
05
Non
e Allowe
d
Non
e Allowe
d
Non
e Allowe
d
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
.010 Deep
Not Repairabl
e
Repl
ace Upp
e
r Hu
b
Repl
a
ce Bushing
Repl
ace Heli
coil
Blend and Polish Out
Smooth
Repl
ace Upp
e
r Hu
b
28-1
428
1
18
Lower Hub
Spline Adapt
er Bore
3.624 to 3.625
U Block Beari
ng Bore
s
2.4986 to 2.4994
Re
ce
sses for
the DU
washers parallel to the
lowe
r su
rfa
c
e
within .001
Damper Bolt Bushing
Dia. .4995 to .5000
Nicks, scrat
c
hes, or
c
o
rr
os
ion
Cra
c
ks
+
.0
0
05
+
.0
0
08
+
.0
0
05
+
.0
0
05
Non
e Allowe
d
Non
e Allowe
d
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
0.10 Deep
Not Repairabl
e
Repl
ace Lower Hu
b
Repl
ace Lower Hu
b
Repl
ace Lower Hu
b
Repl
ace Bushing
Blend and Polish Out
Smooth
Repl
ace Lower Hu
b
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.