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250--C20 SERIES OPERATION AND MAINTENANCE

COMBUSTION SECTION--MAINTENANCE PRACTICES

1. Combustion Liner
A. Removal
(1) (250--C20S, --C20W) Remove the eight bolts and washers and remove the fireshield access
panel.
(2) Remove the following from the outer combustion case.
WARNING: MAKE SURE THAT THE IGNITION SWITCH IS OFF BEFORE REMOVING THE
SPARK IGNITER OR SPARK IGNITER LEAD ASSEMBLY AS DANGEROUS HIGH
VOLTAGES MAY BE PRESENT. ALLOW FIVE MINUTES AFTER OPERATION FOR
ELECTRICAL DISSIPATION BEFORE DISASSEMBLY.
(a) Ignition lead from spark igniter. Ground the lead to the engine to dissipate any stored
energy.
(b) Fuel hose from fuel nozzle. Cap the fuel nozzle and plug the hose.
(c) Drain hose from burner drain valve.
NOTE: If the outer combustion case is also being replaced, remove the spark igniter,
fuel nozzle and burner drain valve.
(3) Remove the internal retaining rings attaching the compressor discharge air tubes to the outer
combustion case.
(4) Remove the 24 screws and nuts at the splitline and separate the outer combustion case from
the turbine and compressor discharge air tubes.
(5) Remove the combustion liner.
B. Installation
Install the replacement combustion liner as follows:
(1) Place the combustion liner over the first--stage turbine nozzle shield with the igniter plug
opening at the nine o’clock position (looking forward).
(2) Slip the retaining rings over the large ends of the compressor discharge air tubes.
(3) Install the spark igniter, fuel nozzle and burner drain valve if they were removed. Required
torques are: spark igniter 150--200 lb in. (17--23 N.m), fuel nozzle 200--300 lb in. (23--34 N.m)
and burner drain valve 120--140 lb in. (14--16 N.m).
(4) Apply antiseize compound to the split seal rings. Compress the seal rings with 6799952
installation clamps. Split seal ring gaps should be 180° apart. Place the outer combustion
case over the liner while mating it to the compressor discharge air tubes.
(5) (250--C20, --C20B --C20F, --C20J) Secure the outer case to the turbine with 24 bolts and nuts.
Coat bolt threads lightly with antiseize compound before installation. The half--inch (13 mm)
length bolt goes at position 20. (On 6887190 engine assembly, the half--inch length bolts go at
positions 6 and 20.) Tighten nuts of socket head cap screws to 20--30 lb in. (2.3--3.4 N.m).
Tighten nuts of tee--head bolts to 35--40 lb in. (3.9--4.6 N.m) plus locknut drag.
(6) (250--C20S, --C20W) Secure the outer case to the turbine with 24 bolts and nuts. Coat bolt
threads lightly with antiseize compound before installation. Retained on this splitline is the fire
shield supporting bracket (positions 4--5). Positions are determined with 1 at top center when
looking forward. These two positions take the half--inch bolts. Tighten bolts of socket head
cap screws to 20--30 lb in. (2.3--3.4 N.m). Tighten nuts of Tee--head bolts to 35--40 lb in.
(3.9--4.5 N.m) plus locknut drag.

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(7) Remove the installation clamps. Seat the compressor discharge air tube anti--rotation pin,
which is located in the outer combustion case, into the anti--rotation slot of the compressor
discharge air tube by pushing the compressor discharge air tube aft while slightly rotating it
CCW and CW until the pin engages the slot. Once the pin is engaged in the slot and the
compressor discharge air tube can no longer be rotated, install the compressor discharge air
tube retaining ring in the groove in the outer combustion case. Make sure that the compressor
discharge air tube is properly seated in the outer combustion case by pulling forward on the
compressor discharge air tube. There must be no significant movement in the forward
direction.
NOTE: The compressor discharge air tube retaining ring can not be properly installed in the
outer combustion case groove unless the anti--rotation pin is correctly seated in the
compressor discharge air tube slot.
(8) Install the following on the outer combustion case.
WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TIGHTEN FUEL, OIL, AND
AIR FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.
(a) Ignition lead to spark igniter. Tighten coupling nut to 70--90 lb in. (7.9--10.2 N.m).
(b) Fuel hose to the fuel nozzle. Tighten coupling nut to 80--120 lb in. (9.0--13.6 N.m).
Secure with lockwire.
(c) Drain hose to the burner drain valve.
(9) (250--C20S, --C20W) Reinstall the fireshield access panel and secure with eight washers and
bolts. Tighten bolts to 22--26 lb in. (2.5--2.9 N.m).
(10) Check run the engine after combustion liner replacement. (Refer to Check Run, para 1,
72--00--00, Engine--Adjustment/Test)
C. Inspection and Repair
Inspect the combustion liner in accordance with Table 201. Remove the combustion section for the
inspection as described in Combustion Liner, para 1.A., this section.

Table 201
Combustion Liner Inspection and Repair

Serviceable Repairable
Item Condition Limit Limit Disposition

1 Louvers bent closed or Maintain Lightly wire brush as

restricted by carbon par- 0.050--0.070 in. required. Vapor de-
ticles (1.27--1.78 mm) grease; then reposition
uniform opening by bending to proper
opening.

2 Burnt louvers Refer to Figure 201 Replace liner or send

for maximum materi- to an overhaul facility
al which can be for repair.
burned away from
individual louvers

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Table 201 (cont)

Serviceable Repairable
Item Condition Limit Limit Disposition

3 Pulled or broken spot- Max of six with no Four adjacent Plugweld repair. Drill
welds at liner step more than three ad- spotwelds or up to 3/16--in. (5 mm) dia
jacent welds 40% of total per hole through outer sec-
step tion then press sec-
tions together and
plugweld using 29--9 W
Mo weld rod (AMS
5784).Grind weld mate-
rial only if it blocks or
restricts airflow.

4 Handling dam- None Unable to straight- Straighten and reform.

age----mashed out of en to concentricity
round limits

5 Handling dam- None Unable to straight- Straighten and reform

age----dented en to concentricity dents in allowable
limits or dent areas indicated on fig.
causes thin--out of 202.
metal

6 Localized high tempera- Max of 3/16 in. (5 Replace liner or send

ture distortion indicated mm) depth over 1 in. to an overhaul facility
by warping of liner sur- (25 mm) dia and for repair.
face (normally accompa- within allowable
nied by discoloration) areas given on fig.
202

7 Burning in area of relief Max of 1/16 in. (2 Replace liner or send

slots mm) on rear edge or to an overhaul facility
both corners burned for repair.
max of 1/4 in. (6
mm) along relief slot

8 Distortion in dome or None Replace liner or send

exit end of liner to an overhaul facility
for repair.

9 Cracks on outside of lin- None Gas tungsten--arc weld

er (FPI) using 29--9 W Mo weld
rod (AMS 5784).
Crack must be com-
pletely welded. Weld
material must not ob-
struct cooling air pas-
sage.

10 Crack in tab end inside Max of 0.23 in. Three or more Replace liner or send
liner (FPI) (6.0 mm) length and cracks, or one or to an overhaul facility
limited to two cracks more cracks in ex- for repair.
per tab cess of 0.23 in.
(6.0 mm) in length

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Table 201 (cont)

Serviceable Repairable
Item Condition Limit Limit Disposition

11 Cracks at two adjacent Max. of 0.12 in. (3.0 Replace liner or send
relief slots progressing mm) length and lim- to an overhaul facility
toward same hole (FPI) ited to two cracks for repair.

12 Crack in relief slot at Max of 0.19 in. Cracks over Gas tungsten--arc weld
combustion liner steps (5.0 mm) in length 0.19 in. (5.0 mm) using 29--9 W Mo weld
(FPI) (no limit) with other cracks rod (AMS 5784.) Grind
extending more weld material only if it
than 0.39 in. blocks or restricts air-
(10.0 mm) toward flow.
air holes

13 Crack in double lip area None Gas tungsten--arc weld

(FPI) using 29--9 W Mo weld
rod (AMS 5784). Sur-
faces between lips
must be free of weld
material.

14 Cracks in expansion Max of 3/16 in. (5 Gas tungsten--arc weld

slots mm) long using 29--9 W Mo weld
rod (AMS 5784). Sur-
faces between lips
must be free of weld
material.

15 Crack in igniter or fuel None Gas tungsten--arc weld

nozzle ferrule attaching using Hastelloy X weld
weld (FPI) rod (AMS 5798). Max
width of weld 0.080 in.
(2.03 mm).

16 Roughened igniter fer- Max of 0.560 in. Send liner to an over-

rule ID (14.22 mm) ID after haul facility for repair if
polishing not within Serviceable
Limit after polishing.

17 Worn or distorted (out-- Min of 0.020 in. Replace liner or send

of--round) igniter ferrule (0.508 mm) wall to an overhaul facility
thickness and max for repair.
of 0.560 in. (14.22
mm) ID

18 Worn or distorted (out-- Max of 0.670 in. Replace liner or send

of--round) fuel nozzle (17.02 mm) ID to an overhaul facility
ferrule for repair.

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Inspection of Combustion Liner Dome Louvers

Figure 201

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Inspection of Combustion Liner

Figure 202

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2. Outer Combustion Case

A. Removal/Installation
Refer to Removal and Installation para 1.A. and 1.B., this section, for procedures.
B. Inspection and Repair
Inspect, repair or replace the outer combustion case in accordance with Table 202. In addition
perform the following inspections:
(1) Using a bright light (flashlight or equivalent) and mirror, inspect all the welds on the outer
combustion case. (See Figure 203.) Welded areas are:
(a) Horizontal butt welds on outer surface and between the air discharge tube attachment
flanges and gas producer attachment flange on forward side.
(b) Both forward and aft circumferential seam welds between outer case and inner liner.
(c) Welds for attaching bosses for fuel nozzle, both combustion case drain valves, both igniter
plugs.
NOTE: Pay particular attention to welds in areas defined in sub--paragraphs (a) and
where these horizontal butt welds meet the circumferential seam welds defined
in sub--paragraph (b).
(d) No cracks are allowed. An outer combustion case that is cracked must be removed from
service and repaired.
(2) Inspect, utilizing the Leak--teck or Fluorescent Penetrant Inspection (FPI) method, the areas of
horizontal butt weld between the air discharge tube attachment flanges and gas producer
attachment flange on the forward side of the outer combustion case as follows:
CAUTION: DO NOT APPLY LEAK--TECH TO A HOT ENGINE. DAMAGE TO THE
ENGINE CAN OCCUR.
(a) Apply Leak--teck to the above designated areas [(1)(a) through (1)(c)] and utilizing a
suitable power source, motor the engine to at least 20% N1 and look for bubbles. No
bubbles (crack indication) are allowed.
(b) FPI the above designated areas [(1)(a) through (1)(c)] utilizing an appropriate light source
for cracks. No crack indications are allowed.
(c) No cracks are allowed. An outer combustion case that is cracked must be removed from
service and repaired or replaced.
(3) Inspect welds of brazed reinforcement wire patches for cracks. No cracks are allowed. An
outer combustion case that is cracked must be removed from service and repaired or replaced.
(4) After any repair, make a careful, visual, leakage inspection of the outer combustion case during
the check run. No leakage is acceptable.

Table 202
Outer Combustion Case Inspection

Serviceable Repairable
Item Condition Limit Limit Disposition

1 Cracks in outer shell None Weld using 29--9 W Mo

(FPI) weld rod (AMS 5784)
or send case to an
overhaul facility for the
repair. Wall thickness
must be 0.016 in.(0.41
mm) minimum. (See
Fig. 203.)

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Table 202 (cont)

Serviceable Repairable
Item Condition Limit Limit Disposition

2 Cracks in liner inner None Weld using 29--9 W Mo

basket (FPI) weld rod (AMS 5784)
or send case to an
overhaul facility for the
repair.

3 Entrapped material un- None Dislodge entrapped

derliner gasket (visu- material using locally
al----dental mirror and/or fabricated wire hooks.
borescope) Remove all foreign ma-
terial.

4 Stripped or crossed None Max of one dam- Chase threads.

threads in fuel nozzle or aged thread per
drain valve bosses boss

5 Dents Area A, Figure 204. Straighten and reform.

Max of one dent up
to 1/8--in. depth x 3
in. length x 1 in.
width (3 x 76 x 25
mm)

Any other area:

Max of 3 dents up to
1/4--in. (6 mm) depth
and 1 in. (25 mm)
dia.

6 Crack in drain plug boss None Weld using 29--9 W Mo

(FPI) weld rod (AMS 5784)
or send case to an
overhaul facility for the
repair.

7 Crack in fuel nozzle or None Weld using 29--9 W Mo

igniter plug boss (FPI) weld rod (AMS 5784)
or send case to an
overhaul facility for the
repair.

8 Wear in air tube boss Max or 0.004 in. Send case to an over-
(See Fig. 205.) (0.10 mm) wear haul facility for repair.
(measured from ad-
jacent unworn area)

9 Out of round at air tube Max of 0.004 in. Send case to an over-
boss (See Fig. 205.) (0.10 mm) out of haul facility for repair.
round

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Weld–Repairable Areas of Outer Combustion Case

Figure 203

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Dent Limits–Top of Outer Combustion Case

Figure 204

Outer Combustion Case Air Tube Boss

Figure 205

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3. Burner Drain Valve

A. Removal/Cleaning/Installation/Check
Remove, clean, install, and check the burner drain valve as follows: (See Figure 206.)
(1) Remove the burner drain valve. Use a wrench on the drain valve boss to offset torque when
removing the valve.
(2) Clean the valve in carbon solvent (Pentatone ECS or equivalent). Flush the valve with
Stoddard solvent or kerosene. Pass fluid through the valve to verify that it is open. Blow dry
with clean shop air.
(3) Apply antiseize compound to the threads of the burner drain valve. Lubricate packing and
place it on the burner drain valve. Install the valve in the outer combustion case. Tighten to
120–140 lb in. (14–16 N.m). Use a wrench on the boss to offset torque.
(4) Start the engine and check that the valve is closed to the passage of air. Replace valve if it
does not close when the engine is operating. Attach drain hose to valve.

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1. Bolt* 5. Burner Drain Valve

2. Clamp* 6. Bracket*
3. Nut* 7. Nut*
4. Packing

*Not used on 250–C20S, –C20W

Burner Drain Valve Removal/Installation

Figure 206

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4. Compressor Discharge Air Tubes

A. Inspection and Repair
Inspect the compressor discharge air tubes in accordance with Table 203. After each repair, make
a careful visual, leakage inspection of the tube during the first engine operation following installation
of the repaired part. Leakage is not acceptable.

Table 203
Compressor Discharge Air Tube Inspection

Serviceable Repairable
Item Condition Limit Limit Disposition

1 Cracks (FPI) None Max of 3.00 in. Weld using 29--9 W Mo

FPI or Dry Motor the (76.0 mm) weld rod (AMS 5784).
engine (with fuel and (no limit) Pressure test in
ignition off) and use 6798787 fixture at
Leak Tec to detect leaks. 150--160 psig
(1034--1103 kPa) for
three minutes. No
leakage is acceptable.
Send tube to an over-
haul facility for repair.

2 Dents Max of three dents Straighten and reform.

per tube up to FPI after repair.
0.12 in. (3.0 mm)
depth by 0.51 in.
(13.0 mm) dia

3 Wear in seal ring groove Max. of 0.195 in. Send tube to an Autho-
(4.95 mm) groove rized Overhaul Facility
width. for repair.

4 Wear on land surface Dia. B, 2.923 in. Send tube to an Autho-

(74.24 mm) Min. rized Overhaul Facility
Dia. F, 2.183 in. for repair.
(55.45 mm) Min.
(Ref. Figure 207).

5 Wear of sheet metal sur- No appreciable loss 1/2 sheet metal Repair using brazed
face of metal thickness thickness screen patch or re-
place. Pressure test
6798787 fixture at
150--160 psig
(1034--1103 kPa) for 3
minutes. No leakage
acceptable.

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Compressor Discharge Tube Inspection and Repair

Figure 207

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