TM 55-2840-241-23
12-2 Change 19
c.
Visually inspect the N1 turbine first-stage blades.
Replace the engine if any of the following conditions
exist:
(1)
Damaged inner 1/3 of blade.
(2)
Blade broken off.
(3)
Cracked blade. If cracks are suspected, refer
to TM 1-1520-254-23, technical manual Aviation Unit
Maintenance (AVUM) and Aviation Intermediate Mainte-
nance (AVIM) manual Nondestructive Inspection Proce-
dure for OH-58 helicopter series.
(4)
Melted blade.
d.
Inspect the combustion liner. (Refer to table
7-1.)
Table 12-3. First-Stage Turbine Nozzle and Shield Inspection
Item
Condition
Serviceable limits
First-Stage Nozzle
1
Axial cracks in vane airfoil.
Leading edge 1/4 in. maximum; trailing edge 5/16 in maximum.
a. No two cracks in same plane.
b. Adjacent cracks 1/4 in. apart.
c. Adjacent cracks not progressing toward each other.
2
Nicked or dented leading
and trailing edge. Warped
or burned trailing edge only.
Leading edge 1/16 in. maximum; trailing edge 1/8 in. maximum.
3
Fillet cracksÐinner and
outer band.
Leading edge 1/4 in. maximum; trailing edge 1/8 in. maximum.
4
Outer band cracksÐleading
and trailing edges.
Visible portion of crack extends 3/16 in. maximum axially into
the band and not in line with crack on opposite edge.
5
Inner band cracksÐleading
and trailing edges.
Leading edgeÐvisible portion of crack extends 3/16 in. maxi-
mum axially into the band and not in line with trailing edge
cracks.
Trailing edgeÐextending through inner band to sheet metal
detail.
First-Stage Nozzle Shield
6
Cracks around spotwelds
on heat shield.
Cracks are acceptable provided the length of the crack is not
greater than 50 percent of the distance around the weld.
1 VANE AIRFOIL CRACKS
2 VANE EDGE DAMAGE
3 FILLET CRACKS
4 OUTER BAND CRACKS
5 INNER BAND CRACKS
9766
PIN: 033211-019
Figure 12-1. Typical First-stage Turbine Nozzle
