ENSTROM F-28F/280F SERIES MAINTENANCE
MANUAL
Rev.
7
MM-9-13
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
425
1
21
Stop Pad
Visual da
mag
e
(cra
cks,
chip
s, etc.)
Non
e Allowe
d
Not Repairabl
e
Repl
ace Stop
ECD0
92
-1
22
Bearin
g
O.D. 2.4994 t
o
2.5000
I.D. 1.7493 to 1.7500
Ratcheting or
roughness
No Tole
ra
nce
Allowed
No Tole
ra
nce
Allowed
Non
e Allowe
d
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
Repl
ace Bearing
Repl
ace Bearing
Repl
ace Bearing
28-1
323
6
23
DU Wa
she
r
Flatness
Thickne
s
s .090 to.093
.005
-.003
Not Repairabl
e
Not Repairabl
e
Repl
ace Wa
sher
Repl
ace Wa
sher
28-1
411
7
24
U-Block
Bore Di
a. 2.4988 to
2.4996
Bearing Surface O.D.
1.7488 to 1.7494
Bearin
g Surfa
c
e
s
c
o
nc
entr
ic
Thre
ad
s
(cro
ssed or m
issi
ng)
Nicks, scrat
c
hes, or
c
o
rr
os
ion
Cra
c
ks
+
.0
0
02
-.0002
.001 FIM
Non
e Allowe
d
None allowed at the
radius of the beari
ng
spin
dle
Non
e Allowe
d
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
Not Repairabl
e
.030 deep
Not Repairabl
e
Repl
ace U-Bl
ock
Repl
ace U-Bl
ock
Repl
ace U-Bl
ock
Repl
ace U-Bl
ock
Blend and p
ol
ish out
smooth
Repl
ace U-Bl
ock
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.