Rolls-Royce Engine 250–C18, 250–C18A, 250–C18B, 250–C18C. Operation and Maintenance Manual (2003)

(2) Pressure gage with approximate range of 0-60 psig (0-414 kPag) and appropriate fittings and

lines to connect to No. 8 bearing pressure oil tube.

(3) Connect an air pressure regulator supplied with clean, dry shop air to the No. 8 bearing

pressure oil fitting and connect a pressure gauge (0-60 psig (0-414 kPag) to the No. 8 bearing

pressure oil tube.

CAUTION: CARE MUST BE TAKEN TO AVOID BENDING OR OTHERWISE DAMAGING THE

NO. 8 BEARING PRESSURE OIL TUBE DURING THE INSTALLATION AND

REMOVAL OF THE PRESSURE GAGE.

(4) With the turbine vertical and the No. 8 bearing sump facing upward, adjust the pressure

regulator to maintain sump pressure at 50 + 2 psig (345 + 14 kPag) as measured on the

pressure oil tube gage.

NOTE: Air will leak across the No. 8 bearing labyrinth seal during this check and should not

be of concern.

(5) With the turbine vertical and the No. 8 bearing sump facing upward and 50 + 2 psig (345 + 14

kPag) internal pressure in the sump, apply Leak-tek or equivalent around the threads and

brazed cap of the sump nut.

WARNING: AIR LEAKAGE ACROSS THE U-RING SEAL WILL RESULT IN PRESSURIZATION

OF THE NO. 8 BEARING SUMP. PRESSURIZATION OF THE NO. 8 SUMP WILL

CAUSE A FLOW REVERSAL ACROSS THE NO. 8 LABYRINTH SEAL. THIS

LEAKAGE CAN RESULT IN AN ENGINE OIL FIRE AND SUBSEQUENT TURBINE

WHEEL RIM FAILURE CAUSING A SECTION OF THE WHEEL RIM TO EXIT THE

ENGINE WITH POTENTIALLY SERIOUS RESULTS.

(6) Hold pressure for one minute minimum. No leakage is acceptable. If leakage occurs,

corrective action must be taken.

(7) Disconnect the pressure test apparatus.

106. Turbine and Exhaust Collector Support Crack Repair

CAUTION: TO PREVENT ELECTRICAL ARC BEARING DAMAGE, SEPARATE THE EXHAUST

COLLECTOR FROM THE ENGINE/TURBINE AND REMOVE THE NO. 5 BEARING

BEFORE THE WELD REPAIR IS MADE.

A. Weld repair any cracks found in the exhaust ducts or outboard structure of the turbine and exhaust

collector support.

(1) Weld cracks in the exhaust ducts (areas -9 and -10 of FIG. 65) using gas tungsten-arc

process with 29-9 W Mo (AMS 5784) weld rod.

(2) Weld cracks in the outboard structure (area -3 of FIG. 65) using gas tungsten-arc process

with Hastelloy W (MIL-R-5031, class 12) weld rod.

Page 196

Turbine and Exhaust Collector Support Weld Repairable Areas

FIG. 65

107. Oil Bellows Seal Replacement

Remove the oil bellows seal as follows:

(1)

Remove the gas producer fuel control and the power turbine fuel governor. (Refer to Gas

Producer Fuel Control Replacement and Power Turbine Fuel Governor Maintenance.)

(2)

Remove the pressure and scavenge oil lines at the power and accessories gearbox.

(3)

Remove the pressure sensing line at the diffuser scroll and at the tee at the governor.

(4)

Remove the ignition lead from the ignition exciter.

(5)

Remove the drain hoses from the burner drain valve, firewall shield, and exhaust collector

support.

(6)

Remove the five nuts at the splitline and separate the turbine and combustion section

assembly from the power and accessories gearbox.

(7)

Remove the turbine shaft-to-pinion gear and turbine-to-compressor couplings. Discard

O-ring.

(8)

Remove the two nuts and bolts and separate the firewall from the turbine assembly.

NOTE: Keep the packing, seal rings, wave washers, and split rings with the compressor

discharge air tubes when the tubes are separated from the diffuser scroll and

firewall.

(9)

Attach the turbine and combustion section assembly on the supporting adapter (M, FIG. 1), at

the three exhaust collector support bolt holes, with the combustion section down.

(10) It may be necessary to reverse the three turbine attaching studs on the supporting adapter

plate from a top side mounting position to an under side mounting position.

(11)

Remove the power turbine shaft ball bearing spanner nut using the holder and wrench (C, D,

FIG. 1). (Ref. FIG. 66)

Page 197

(12) Remove the internal retaining ring and spacers (washer) from the turbine and exhaust collector

support.

(13) Pull the ball bearing from the power turbine shaft with 6872882 puller.

NOTE: Make note of the exact bearing index location before removal so that it can be

installed in the same position as it was in the preceding buildup.

(14) Remove the thrust plate (not on all configurations).

(15) Remove the mating ring rotating seal from the power turbine shaft using 6872882 puller.

NOTE: If facilities are not available to lap the mating ring rotating seal (to ensure flatness

within six helium light bands--use optical flat and polarized light source), replace the

mating ring rotating seal whenever the oil bellows seal is replaced.

1. Spanner Nut

5. Thrust Plate

2. Retaining Ring

6. Mating Ring Rotating Seal

3. Washer

7. Oil Bellows Seal Assy

4. No. 5 Bearing

8. Power Turbine Shaft Shield

Oil Bellows Seal Removal

FIG. 66

Page 198

(16) Remove the oil bellows seal from the turbine and exhaust collector support with a puller (U,

FIG. 1). (Ref. FIG. 67)

NOTE: To maintain the rotor total travel as in the preceding engine buildup, measure and

record the new and old oil bellows seal thickness. Change the spacer (washer)

thickness to account for any difference in seal thickness. The new seal (or seal and

thrust plate when a damped-bellows type seal is used) plus the new spacers must

be the same thickness as the old seal (or seal and thrust plate) plus the old spacers.

(Ref. FIG. 68)

Pulling the Oil Bellows Seal from the Turbine and Exhaust Collector Support

FIG. 67

B. Install the oil bellows seal as follows:

(1) Thoroughly clean the bellows seal bore in the exhaust collector. Remove oil traces with

methylethylketone. Apply a light coating of sealant (Permatex 1372, or equivalent) to the seal

bore below the oil drain slots in the exhaust collector.

(2) Install the replacement oil bellows seal using 6796918 drift (E, FIG. 1). Chill the seal with dry

ice to aid in assembly.

(3) Install the thrust plate (used with the damped-bellows seal only) and the mating ring rotating

seal.

Page 199

NOTE: If facilities are not available to lap the mating ring rotating seal (to ensure flatness

within six helium light bands--use optical flat and polarized light source), replace the

mating ring rotating seal whenever the oil bellows seal is replaced.

Spacer Thickness Determination

FIG. 68

(4) Install the ball bearing on the power turbine shaft using 6796922 pusher (G, FIG. 1) and guide

(-2) of 6796918 drift assembly. The pusher locks on the splines inside the power turbine

shaft.

NOTE: Install the bearing in the position noted at disassembly.

(5) Insert spacers (washers) and internal retaining ring. Retain bearing stack with spanner nut

lightly lubricated with engine oil. Torque the nut to 250-300 lb in. (28-34 N^.m) using 6795985

wrench and 6795984 holder. (Ref. FIG. 69) Stake nut edge into lock detent using 6798927

crimper, do not use a previous locking position.

(6) Remove the turbine and combustion section assembly from 6798089 supporting adapter (M,

FIG. 1).

Page 200

(7)

Install the firewall on the front of the turbine. Retain with two each nuts, bolts, and washers.

Coat threads of bolts lightly with antiseize compound before installation. Torque nuts to 35-40

lb in. (3.9-4.5 N^.m).

(8)

Apply engine oil lightly to the splines, then install the compressor-to-turbine coupling on the

spur adapter gearshaft and the turbine shaft-to-pinion gear coupling with two new O-rings

(one O-ring on some configurations) on the turbine rotor.

NOTE: Always replace the O-ring on the spur adapter gearshaft each time the turbine

assembly is removed or anytime the O-ring is exposed. Use only authorized P/N

O-rings as replacements.

(9)

Install the turbine and combustion section assembly on the power and accessories gearbox as

follows:

(a) Apply antiseize compound lightly to the threads of the five turbine attaching studs.

(b) Place the packing, seal rings, and wave washers over the small end of the compressor

discharge air tubes. Apply antiseize compound to the split seal rings. Use 6799952 and

6799953 installation clamps (R, S, FIG. 1) to compress the split seal ring for installation

into the diffuser scroll.

CAUTION: DO NOT USE THE IGNITER PLUG, FUEL NOZZLE OR ANY LINES OR

TUBING AS HANDLES FOR MANEUVERING THE TURBINE AND

COMBUSTION SECTION ASSEMBLY DURING THE INSTALLATION.

(10) Carefully mate the turbine and combustion section assembly to the power and accessories

gearbox. Turn the gear trains with 6799790 engine turning adapter (Q, FIG. 1) as necessary

to allow the coupling splines to mate. Retain the turbine with five nuts; torque the top nut

(5/16-24) to 110-120 lb in. (12-14 N^.m) and the bottom four nuts (1/4-28) to 55-65 lb in.

(6.2-7.3 N^.m).

(11)

Install the drain hoses at the burner drain valve, firewall shield, and exhaust collector support.

(12) Attach the ignition lead to the ignition exciter. Torque lead coupling to 70-90 lb in. (7.9-10.2

N^.m).

WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TORQUE FUEL, OIL, AIR

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(13) For engines without a P_c filter, install the pressure sensing line from the diffuser scroll to the

tee at the governor. For engines with a P_c filter, install the scroll-to-filter and

filter-to-governor tee tubes. Hold the P_c filter while connecting these tubes. Torque coupling

nuts to 80-120 lb in. (9.0-13.6 N^.m).

(14) Install the pressure and scavenge oil lines. Torque the nut retaining the elbow to the firewall

shield to 55-80 lb in. (6.2-9.0 N^.m). Torque the scavenge tubing coupling nuts to 150-200

lb in. (17-23 N^.m). Torque the supply tubing coupling nuts to 80-120 lb in. (9.0-13.6 N^.m).

(15) Install the gas producer fuel control and the power turbine fuel governor. (Refer to Gas

Producer Fuel Control Replacement and Power Turbine Fuel Governor Maintenance).

Page 202

108. Turbine Assembly Replacement

Replace the turbine assembly as follows:

(1)

Remove the ignition lead from the spark igniter, firewall shield and clamping points.

(2)

Remove the fuel line from the fuel control, firewall shield and fuel nozzle.

(3)

Remove the drain hoses at the burner drain valve, firewall shield, and exhaust collector

support.

(4)

Remove the gas producer fuel control and attached control and fuel lines.

(5)

Remove the power turbine fuel governor and attached control lines.

(6)

Remove the accumulator loop type support clamp from the firewall shield.

(7)

Remove the turbine pressure and scavenge oil lines from the firewall shield and external

sump.

(8)

Remove the lead from the thermocouple terminal. Remove the thermocouple and two

thermocouple lead clamps.

(9)

Remove the internal retaining rings attaching the compressor discharge air tubes to the

combustion outer case. Remove the 24 bolts at the splitline and separate the combustion

section from the turbine and from the compressor discharge air tubes.

(10) Remove the two compressor discharge air tubes and make the following inspection of the seal

groove lands and of the split seal rings at the compressor (small) end.

(a) Remove the split seal rings from the small end of the air tubes.

(b) Replace the split seal rings if the edges show wear which could be detrimental to the

sealing effect or if the expander ring is broken.

(d) Apply antiseize compound to the components of the split seal rings. Install the rings on

the discharge air tubes. Split seal ring gaps should be 180° apart.

(11)

Remove the five nuts at the splitline and separate the turbine assembly from the power and

accessories gearbox.

NOTE: Refer to Helical Gear Internal Spline Inspection, para 71.

(12) Remove the turbine shaft-to-pinion gear and turbine-to-compressor couplings. Discard

O-rings. Replacement couplings are included in the turbine assembly unit exchange package.

(13) Remove the burner drain valve from the outer combustion case. Wash in hot detergent, rinse

in water and blow dry.

(14) Install the burner drain valve in the outer combustion case. Torque valve to 120-140 lb in.

(14-16 N^.m).

Install the replacement turbine assembly as follows:

(1) Apply engine oil lightly to the splines of the two turbine couplings. Install the

compressor-to-turbine coupling on the spur adapter gearshaft. Lubricate two new O-rings

and install them on the turbine shaft-to-pinion gear coupling. (Some configurations have only

one O-ring.) Install the coupling on the rotor of the replacement turbine with the end having

the four equally spaced grooves out (toward the gearbox).

(2) Lubricate O-ring and place it on the back of the power and accessories gearbox. Install the

replacement turbine on the gearbox. Turn the gear trains with the engine turning adapter (Q,

FIG. 1) as necessary to allow the coupling splines to mate. Retain the turbine with five nuts.

Coat stud threads lightly with antiseize compound before installation. Torque the top nut

(5/16-24) to 110-120 lb in. (12-14 N^.m) and the four bottom nuts (14/-28) to 55-65 lb in.

(6.2-7.3 N^.m).

Page 203

CAUTION: DO NOT FORCE THE TURBINE AND GEARBOX ASSEMBLIES TOGETHER. IF

INTERFERENCE IS ENCOUNTERED CHECK THE PINION BEARING OIL

NOZZLE TO DETERMINE IF IT IS THE CAUSE. (SEE STEP (3).)

(3)

If the pinion bearing oil nozzle is determined to be the interference hindering

turbine-to-gearbox fit, remove the nozzle and lightly dress it with a file. (Ref. FIG. 70)

Thoroughly clean the dressed nozzle with solvent. Air dry. Apply antiseize compound to the

studs and lubrication to the new O-ring. Install nozzle and O-ring. Secure the nozzle with two

washers and nuts. Torque nuts to 35-40 lb in. (3.9-4.5 N^.m).

(4)

Remove the retaining rings and separate the compressor discharge air tubes from the

combustion section.

(5)

Place the packing, seal ring, and wave washers over the small end of one compressor

discharge air tube, then insert the tube through the firewall into the diffuser scroll. Use the

installation clamp (S, FIG. 1) to compress the split seal ring for the installation. Install the

second air tube in the same manner.

(6)

Slip the retaining rings over the large ends of the compressor discharge air tubes.

(7)

Place the combustion liner over the 1st-stage turbine nozzle shield with the igniter plug

opening at the nine o’clock position (looking forward).

(8)

Compress the seal rings with the installation clamps (R, FIG. 1). Place the outer combustion

case over the liner while mating it to the compressor discharge air tubes. Secure the outer

case to the turbine with 24 bolts and nuts. Coat bolt threads lightly with antiseize compound

before installation. Torque nuts of the socket head cap screws to 20-30 lb in. (2.3-3.4 N^.m).

Torque nuts of Tee-head bolts to 35-40 lb in. (3.9-4.5 N^.m). The half-inch (13 mm) length

bolt goes at position 21 (with 1 at top center looking forward). Remove the installation clamps

and secure the air tubes with retaining rings.

(9)

Install drain hoses at the burner drain valve, firewall shield, and exhaust collector support.

Turbine-to-Gearbox Interference Correction

FIG. 70

Page 204

(10) Attach the ignition lead to the spark igniter, firewall shield and clamping points. Torque spark

igniter coupling nuts to 70-90 lb in. (7.9-10.2 N^.m).

WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TORQUE FUEL, OIL, AIR

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(11) Install the gas producer fuel control, power turbine fuel governor with the control and fuel lines.

Torque fuel line coupling nuts to 150-200 lb in. (17-23 N^.m) and air line coupling nuts to

80-120 lb in. (9.0-13.6 N^.m).

(12) Attach the fuel line to the fuel control, firewall shield, and fuel nozzle. Torque nozzle coupling

nut to 80-120 lb in. (9.0-13.6 N^.m). Secure with lockwire.

(13) Attach the accumulator loop-type support clamp to the firewall shield.

(14) Install turbine pressure and scavenge oil lines.

(15) Attach the thermocouple terminal to the exhaust collector support with two nuts and bolts.

Torque nuts to 20-25 lb in. (2.3-2.8 N^.m). Clamp thermocouple lead to the firewall shield at

two places using clamps, bolts, and nuts. Torque nuts to 35-40 lb in. (3.9-4.5 N^.m). Attach

thermocouple leads to terminal; Torque chromel (small) nut to 10-15 lb in. (1.1-1.7 N^.m) and

alumel (large) nut to 30-40 lb in. (3.4-4.5 N^.m).

(16) Make appropriate entry relative to turbine replacement in the Engine Log.

(17) Check run the engine after turbine replacement. (Refer to Engine Check Run.)

109. Combustion Section Inspection

Inspect the combustion liner in accordance with Table 15. Remove the combustion section for the

inspection as described in Combustion Liner Replacement.

TABLE 15

Combustion Liner Inspection and Repair

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Louvers bent

Maintain 0.060-0.065 in.

Lightly wire brush as

closed or restricted by

(1.52-1.65 mm) uniform

required. Vapor de-

carbon particles

opening

grease; then reposi-

tion by bending to

proper opening.

Burnt louvers

Refer to FIG. 71 for maxi-

Replace liner or prop-

mum material which can

er opening. send to

be burned away from indi-

an overhaul facility

vidual louvers

for repair.

Pulled or broken spot-

Six or no more than three

Four adjacent spot

Plugweld repair. Drill

welds at liner step

adjacent welds

welds or up to 40%

3/16-in. (5 mm) dia

of total per step

hole through outer

section then press

sections together and

plugweld using 29-9

W Mo weld rod (AMS

5784). Grind weld

material only if it

blocks or restricts air-

flow.

Handling damage-

None

Unable to straighten

Straighten and re-

mashed out of round

to concentricity limits

form.

Page 205

TABLE 15

Combustion Liner Inspection and Repair - continued

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Handling damage-

None

Unable to straighten Straighten and re-

dented

to concentricity limits

form dents in allow-

or dent causes thin-

able areas indicated

out of metal

on FIG. 72.

Localized high tempera-

Max. of 3/16 in. (5 mm)

Replace liner or send

ture distortion indicated

depth over 1 in. (25 mm)

to an overhaul facility

by warping of liner sur-

dia and within allowable

for repair.

face (normally accom-

areas given on FIG. 65

panied by discoloration)

Burning in area of relief

Max. of 1/16 in. (2 mm) on

Replace liner or send to an

slots

rear edge or both corners

overhaul facility for repair.

burned max. of 1/4 in. (6

mm) along relief slot

Distortion in dome or

None

Replace liner or send to an

exit end of liner for re-

overhaul facility

pair.

Cracks on outside of lin-

None

Gas tungsten-arc weld us-

er (dye check)

ing 29-9 W Mo weld rod

(AMS 5784). Crack must

be completely welded.

Weld material must not ob-

struct cooling air passage.

Crack in tab end inside

Max. of 1/4 in. (6mm)

Three or more

Replace liner or send to an

liner (dye check)

length and limited to 2

cracks, or one or

overhaul facility for repair.

cracks per tab

more cracks in ex-

cess of 1/4 in. (6

mm) in length

Cracks at two adjacent

Max. of 1/8 in. (3 mm)

Replace liner or send to

relief slots progressing

length and limited to two

an overhaul facility for re-

toward same hole (dye

cracks

pair.

check)

Crack in relief slot at

Max. of 3/16 in. (5 mm) in

Cracks over 3/16 in.

Gas tungsten-arc

combustion liner steps

length (any number)

(5 mm) with other

weld using 29-9 W

(dye check)

cracks extending

Mo weld rod (AMS

more than 3/8 in. (10

5784.) Grind weld

mm) toward air

material only if it

holes

blocks or restricts air-

flow.

Page 206

TABLE 15

Combustion Liner Inspection and Repair - continued

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Crack in double lip area

None

Gas tungsten-arc

(dye check)

weld using 29-9 W

Mo weld rod (AMS

5784). Surfaces be-

tween lips must be-

tween lips must be

free of weld material.

Cracks in expansion

Max. of 3/16 in. (5 mm)

Replace liner or send

slots

length

to an over-haul facil-

ity for repair.

Crack in igniter or fuel

None

Gas tungsten-arc

nozzle ferrule attaching

weld using Hastelloy

weld (dye check)

X weld rod (AMS

5798). Max width of

weld 0.080 in. (2.03

mm).

Roughened igniter fer-

Max. of 0.560 in. (14.22

Send liner to an over-

rule ID

mm) ID after polishing

haul facility for repair

if not within Service-

able Limit after pol-

ishing.

Worn or distorted (out-

Min of 0.020 in. (0.508

Replace liner or send

of-round) igniter ferrule

mm) wall thickness and

to an overhaul facil-

max. of 0.560 in. (14.22

ity or repair.

mm) ID.

Worn or distorted (out-

Max. of 0.670 in. (17.02

Replace liner or send

or-round) fuel nozzle

mm) ID

to an overhaul facility

ferrule

for repair.

Page 207

Combustion Liner Dome Louvers Inspection

FIG. 71

110. Combustion Liner Replacement

A. Replace the combustion liner as follows:

(1) Remove the ignition lead from spark igniter from the outer combustion case.

(2) Remove the fuel line from fuel nozzle from the outer combustion case.

(3) Remove the drain line from burner drain valve from the outer combustion case.

NOTE: If the outer combustion case is also being replaced, remove the spark igniter, fuel

nozzle and burner drain valve.

(4) Remove the internal retaining rings attaching the compressor discharge air tubes to the outer

combustion case.

(5) Remove the 24 screws and nuts at the splitline and separate the outer combustion case from

the turbine and compressor discharge air tubes.

(6) Remove the combustion liner.

Page 208

Install the replacement combustion liner as follows:

(1) Place the combustion liner over the 1st-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. (23-24 N^.m)

and burner drain valve 120-140 lb in. (14-16 N^.m).

(4) Apply antiseize compound to the split seal rings then compress the rings with 6799952,

6799953 installation clamps (R, S, FIG. 1). Place the outer combustion case over the liner

while mating it to the compressor discharge air tubes. Secure the outer case to the turbine

with 24 bolts and nuts. Coat bolt threads lightly with antiseize compound before installation.

Torque nuts of socket cap screws to 20-30 lb in. (2.3-3.4 N^.m). Torque nuts of Tee-bolts to

35-40 lb in. (3.9-4.6 N^.m). The half-inch (13 mm) length bolt goes at position 21 (with 1 at top

center looking forward). Remove the installation clamps and secure the air tubes with

retaining rings.

WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TORQUE FUEL, OIL, AIR

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(5) Install the following on the outer combustion case.

(a) Ignition lead to spark igniter. Torque coupling nut to 70-90 lb in. (7.9-10.2 N^.m).

(b) Fuel line to the fuel nozzle. Torque coupling nut to 80-120 lb in. (9.0-13.6 N^.m). Secure

with lockwire.

(6) Check run the engine after combustion liner replacement. (Refer to Engine Check Run.)

111. Outer Combustion Case Maintenance

Inspect, repair, or replace the outer combustion case in accordance with Table 16. After any repair,

perform a careful visual leakage inspection of the outer case during the check run. No leakage is

acceptable.

TABLE 16

Outer Combustion Case Inspection

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Cracks in outer shell

None

Weld using 29-9 W

(dye check)

Mo weld rod (AMS

5784) or send case

to an overhaul facility

for the repair. Wall

thickness shall be

0.016 in. (0.47 mini-

mum in areas A and

B of FIG. 73 after

weld repair.

Cracks in liner inner

None

Weld using 29-9 W

basket (dye check)

Mo weld rod (AMS

5784) or send case

to an overhaul facility

for the repair.

Entrapped material un-

None

Dislodge entrapped

der liner gasket (visu-

material using locally

al--dental mirror and/or

fabricated wire

borescope)

hooks. Remove all

foreign material.

Page 210

TABLE 16

Outer Combustion Case Inspection - continued

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Stripped or crossed

None

Max. of one dam-

Chase threads.

threads in fuel nozzle or

aged thread per

drain valve bosses

boss

Dents

Area A, FIG. 74 Max. of

Straighten and re-

one dent up to 1/8-in.

form.

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. to

1/4-in. (6 mm) depth and

1 in. (25 mm) dia.

Crack in drain plug boss

None

Weld using 29-9 W

(dye check)

Mo weld rod (AMS

5784) or send case

to an overhaul facility

for the repair.

Crack in fuel nozzle or

None

Weld using 29-9 W

igniter plug boss (dye

Mo weld rod (AMS

check)

5784) or send case

to an overhaul facility

for the repair.

Wear in air tube boss

Max. or 0.004 in. (0.10

Send case to an

(Ref. FIG. 75)

mm) wear (measured from

overhaul facility for

adjacent unworn area)

repair

Out of round at air tube

Max. of 0.004 in. (0.10

Send case to an

boss (Ref. FIG. 75)

mm) out of round

overhaul facility for

repair.

Page 211

112. Burner Drain Valve Maintenance

A. Remove, clean, install, and check the burner drain valve as follows: (Ref. FIG. 76)

(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 (Cities Service No. 26 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 O-ring and place

it on the burner drain valve. Install the valve in the outer combustion case. Torque 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.

1. Nut

2. Bolt

3. Bracket

4. Clamp

5. Nut

6. Plug (250-C18A,-C18B)

7. Burner Drain Valve (250-C18A,-C18C)

8. O-Ring

9. Burner Drain Valve (250-C18A,-C18C)

10. Plug (250-C18, -C18B)

11. O-Ring

Burner Drain Valve Removal

FIG. 76

Page 214

113. Compressor Discharge Air Tubes Inspection

Inspect the compressor discharge air tubes in accordance with Table 17. After any repair, perform

a careful visual leakage inspection of the tube during the first engine operation following installation

of the repaired part. No leakage is acceptable.

TABLE 17

Compressor Discharge Air Tube Inspection

Item

Condition

Serviceable Limit

Repairable Limit

Disposition

Cracks (dye check)

None

Max. of 3 in. (75

Weld using 29-9 W

mm) (any number)

Mo weld rod (AMS

5784). Pressure test

in 6798787 fixture at

150-160 psig

(1034-1103 kPa) for

three minutes. No

leakage is accept-

able. Send tube to

an overhaul facility

for repair.

Dents

Max. of 3 dents per tube

Straighten and re-

up to 1/8-in. (3 mm) depth

form. Dye check af-

by 1/2-in. (13 mm) dia

ter repair.

Wear in seal ring groove

Ref. FIG. 77.

Wear on land surface

Ref. FIG. 77.

(Ref. FIG. 77)

Wear of sheet metal

No appreciable loss of

1/2 sheet metal

Repair using brazed

surface

metal thickness

thickness

screen patch or re-

place. Pressure test

6798787 fixture at

100 psig (689 kPa)

for 3 minutes. No

leakage acceptable.

Page 215

114. Power And Accessories Gearbox (gearbox) Maintenance

A. Power and accessories gearbox (hereafter; referred to as the gearbox) maintenance includes:

inspection and repair of compressor mounting inserts; inspection for oil leaks; replacement of oil

seals; replacement of the gearbox; disassembly and assembly of the gearbox for part replacement

and disassembly, inspection and assembly of the oil pump.

(1) Starter-generator Gearshaft Female Spline Inspection.

(a) Remove the starter-generator.

(b) Clean the female splines of the starter-generator gearshaft and the male splines of the

starter-generator driveshaft with mineral spirits and a soft brush.

NOTE: A sharp pointed scribe can be helpful in detecting a wear step. A 0.010 in. (0.25

mm) feeler gage can be helpful in visually comparing the depth of the wear step.

(d) Lubricate acceptable splines with engine oil.

(e) Before reinstallation of the starter-generator, make sure the torsional damper members of

the driveshaft in the starter-generator are in hard contact with each other.

115. Opened Gearbox Inspection

A. Whenever the gearbox is opened for any reason, make a general inspection of the assembly,

paying particular attention to the following:

(1) Check condition of accessory gearshaft drive splines. If excessive wear is believed present,

replace the gearshaft.

(2) Check condition of gears. Replace gears having spalled or chipped teeth.

(3) Check mounting and attachment security of all internal parts including tab lock washers and

safety wire. Secure as required.

(4) Check integrity of oil pump attaching screws and oil tube O-rings.

(5) Check condition of the accessory pad seal for the gas producer gear train idler spur gearshaft

(inside the gearbox cover). Replace seal if it shows apparent damage or if the engine is prone

to blow oil out the gearbox vent.

(6) Check the filter housing for excessive wear at the opening for the filter inlet and filter bypass

tubes. Replace O-rings on the filter inlet and bypass tubes at each disassembly. Replace the

filter housing if necessary to prevent air/oil leakage.

(7) If the records indicate that more than 3500 hours have elapsed since the gears were new or

were last magnafluxed at overhaul or repair, all gears are to be magnetically inspected. (Refer

to the Engine Overhaul Manual, publication No. 5W2, for inspection criteria.)

NOTE: If any doubt exists concerning the serviceability of any part, repair or replace the part

before closing the gearbox.

Page 217

116. Compressor Mounting Inserts Inspection

A. Any time the compressor is removed or if an insert(s) looseness is known or suspected, check for

the space between the inserts and the gearbox housing. If a piece of 0.0015 in. (0.038 mm) shim

stock can be inserted anywhere under the insert, the insert shall be reworked.

117. Compressor Mounting Inserts Repair

CAUTION: The gearbox housing must have at least three good compressor mounting inserts before

rework can be accomplished on a loose insert.

Repair loose compressor mounting inserts in the gearbox housing as follows:

NOTE: The rework shall be made with the engine removed from the airframe and with the

compressor assembly removed from the gearbox. (Refer to Compressor Assembly

Replacement.)

(1)

Clean the area of the loose insert on the gearbox housing with methylethylketone.

(2)

If the insert is pinned, use a No. 53 drill to drill out the insert locking pin. Remove the insert

using wrench 6872881 (EX 97154) or 6872927 as applicable.

(3)

File off the burrs and clean the threads and surrounding area of the housing using a brush and

methylethylketone.

(4)

Check the threads of the gearbox housing for wear. Check by reinstalling the removed insert

in the threaded opening of the housing. The threads should be snug when the bottom side of

the insert flange is 1/8 in. (3 mm) above the surface of the gearbox. If any side movement or

wobble is present, use an oversized insert for the replacement. Select the oversized insert to

obtain the best fit.

(5)

Install the selected insert. Torque to 125-150 lb in. (14-17 N^.m) plus running torque. Do not

exceed 180 lb in. (20 N^.m).

(6)

Install checking fixture 6872880 (EX 92634) over the five compressor mounting inserts. (Ref.

FIG. 79) Be sure the fixture does not touch any of the four bosses around the insert at the

seven o’clock position. Determine the seven o’clock position by viewing the gearbox from the

front (compressor) side.

(7)

Use shim stock to feel for clearance between each insert flange and the bottom of the fixture.

Rework insert flange using spotfacing kit 6872879 (EX 97156) until there is no clearance at

any of the five locations. (Ref. FIG. 80)

NOTE: When properly installed and reworked the five compressor mounting inserts are the

same height. In this condition the checking fixture rests on all five points and each

insert-to-fixture fit will be closed to the passage of the shim stock feeler gage.

(8)

Mark the gearbox boss at the location of the insert pin slot. Remove the insert using wrench

6872881 (EX 97154) or 6872927 as applicable. Clean the threads of the insert and the

gearbox using methylethylketone.

(9)

Apply Resiweld FE 186, or equivalent, sealer to the threads of the replacement insert. Thread

the insert into the gearbox. The insert will apply sealer to the threads in the gearbox. Repeat

the application of sealer to the insert as necessary to cover all threads of both parts. Also, at

the five o’clock insert position, do not install the O-ring; however, be sure the O-ring groove is

filled with sealer.

CAUTION: WIPE EXCESS SEALER FROM THE END OF THE INSERT TO MAKE SURE

THAT NONE OF THE SEALER ENTERS THE GEARBOX AT THE SEVEN

O’CLOCK INSERT POSITION THROUGH-HOLE. ON BOTTOM-HOLED INSERT

LOCATIONS, MAKE SURE THE HOLE DOES NOT ACCUMULATE EXCESS

SEALER WHICH CAN PUSH UP THROUGH THE INSIDE THREAD OF THE

INSERT. CLEAN SEALER FROM INSERT INSIDE THREADS BEFORE IT

HARDENS USING METHYLETHYLKETONE AND A 14/-28 BOLT. RETAP (1/4-28)

THE INSIDE THREAD IF HARDENED SEALER IS ENCOUNTERED.

(10) Install the new insert. Torque to 125-150 lb in. (14-17 N^.m) to a position where the pin slot

aligns with the mark on the gearbox boss. (See para (8) Do not exceed 180 lb in. (20 N^.m).

Page 219

(11) Wipe any excess sealer from the insert or gearbox. Recheck insert height. (See steps (6) and

(7.) Cure sealer for 25-35 minutes at 177°C (350°F), or as an option, at 149°C (300°F) for two

hours (to combine cure cycle with paint bake cycle).

(12) Install compressor and turbine assemblies on the gearbox. (Refer to Replacing the

Compressor Assembly Replacement.)

(13) Return the engine to service. Inspect the insert at the seven o’clock position for any sign of oil

leakage after the Check Run. Repair the insert if any leakage is detected.

118. Oil Leakage Inspection

A. Inspect the power and accessories gearbox for oil leaks. Replace the seal assembly if excessive

oil leakage is detected at the accessory pad locations. (Ref. FIG. 81)

1. Power Turbine Tachometer-Generator Pad

1. Power Takeoff Pad

2. Power Output Pad

2. Fuel Pump Pad

3. Gas Producer Tachometer-Generator Pad

3. Vacuum-Hydraulic Pad

4. Torquemeter Spanner Nut

4. Power Turbine Fuel Governor Pad

5. Starter Generator Pad

5. Gas Producer Fuel Control Pad

Power and Accessories Gearbox Inspection

FIG. 81

Page 221

119. Power Train Drive Helical Gear Spline Inspection

A. Inspect the power train drive helical gear spline whenever the engine has been subjected to a

sudden stoppage as defined Sudden Engine Stoppage Inspection or whenever the turbine is

removed. Replace the gear (24, FIG. 83, Sheet 1 of 2) if determined unacceptable.

(1) Visually inspect splines for evidence of deformation or twisting. No deformed or twisted

splines allowed.

(2) Visually inspect splines for pitted, cracked or broken teeth. No pitted, cracked or broken teeth

allowed.

(3) Using a sharp pointed scribe, 0.020 in. (0.51 mm) radius, inspect spline teeth for a wear step.

Any discernable wear tht can be felt with scribe is unacceptable.

120. Power and Accessories Gearbox Oil Seals Replacement

A. Replace leaking power and accessories gearbox seals as follows:

(1) Remove the accessory or drive from the gearbox pad.

CAUTION: DO NOT PRY BETWEEN THE SEAL CAVITY IN THE HOUSING AND THE SEAL.

(2) Use the seal replacement kit to remove the seal (H, FIG. 1). Be careful not to contaminate the

shaft bearing or damage the gear shaft. The seal will be damaged during removal,

consequently will not be salvageable.

CAUTION: DO NOT USE SILICONE LUBRICANTS EXCEPT WHERE SPECIFIED. USE

ONLY THE LUBRICANTS RECOMMENDED IN THE ENGINE PUBLICATIONS.

(3) Apply grease (Shell 6249, or equivalent) to the seal lip to aid the installation then carefully

drive (or press) the replacement seal in place.

(4) Reinstall the accessory or drive on the gearbox pad.

121. Power and Accessories Gearbox Replacement

Remove the following from the rejected power and accessories gearbox.

(1) Ignition Exciter

(2) Power Turbine Fuel Governor

(3) Fuel Pump and Filter Assembly

(4) Gas Producer Fuel Control

(5) Lubrication System Tubing and Fittings

(6) Engine Identification Plate

(7) Two Magnetic Plugs

(8) Rear Takeoff Pad Cover

Remove the compressor. (Refer to Compressor Replacement.)

Remove the turbine and combustion section assembly. (Refer to Turbine Assembly Replacement;

it is not necessary to separate the combustion section from the turbine.)

Inspect all fuel, control air, and oil tubes.

(Refer to Fuel, Control Air, and Oil Tubes Inspection.)

Remove the rejected gearbox and install the replacement unit.

NOTE: Transfer the accessory pad covers as required from the rejected to the replacement

gearbox.

Install the following from the rejected power and accessories gearbox.

(1) Install the compressor.

(Refer to Compressor Replacement.)

(2) Install the turbine and combustion section assembly. (Refer to Turbine Assembly

Replacement.)

Page 222

WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TORQUE FUEL, OIL, AIR

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(3) Install the ignition exciter

(4) Install the power turbine fuel governor

(5) Install the fuel pump and filter assembly

(6) Install the gas producer fuel control

(7) Install the engine identification plate

(8) Install the two magnetic plugs. Install with new O-rings, Torque to 60-80 lb in. (6.8-9.0 N^.m)

and secure with lockwire.

(9) Lubrication System Tubing and Fittings. (Ref. FIG. 82) Apply a light coating of engine oil to

lubrication system fitting threads and to O-rings to aid installation.

(10) Rear Takeoff Pad Cover. Torque nuts to 70-85 lb in. (7.9-9.6 N^.m).

G. Make appropriate entry relative to gearbox replacement in the Engine Log.

H. Check run the engine after gearbox replacement. (Refer to Engine Check Run.)

NOTE: When the power and accessories gearbox has been replaced, check the system oil level

before and after the check run.

Page 223

122. Gearbox Disassembly

NOTE: Applicable parts of the following procedure may be used by any knowledgeable and qualified

maintenance facility to perform part replacement in the gearbox. Return the gearbox to an

Rolls-Royce Authorized Maintenance Facility if repair beyond part replacement is required or if

metal particles are detected inside the gearbox.

Disassemble the gearbox as follows:

(1) Remove the engine from the aircraft and separate the gearbox from the engine. Refer to

Power and Accessories Gearbox Replacement.

(2) Install the gearbox in 6795579 turnover stand or equivalent.

(3) Remove the 39 nuts, 4 bolts and 43 washers at the splitline and separate the cover from the

housing. (Ref. FIG. 83, Sheet 1 of 2.)

Disassemble the gearbox cover as follows:

(1)

Remove the two self-locking nuts and take the power train pinion oil nozzle from the aft side of

the gearbox cover. Discard the O-ring seal. (Ref. FIG. 83, Sheet 1 of 2.)

(2)

Remove the torquemeter shaft support spanner nut using 6795597 wrench. (Ref. FIG. 84)

Remove the cup washer. Remove the torquemeter shaft support from the gearbox cover.

Remove the headed pin; then press the bearing inner race from the support using 6796947

drift and 6796950 plate with detail -4. (Ref. FIG. 85 and 86)

(3)

Simultaneously remove the helical power takeoff gearshaft and the helical torquemeter

gearshaft. Remove the helical torquemeter gearshaft bearing end plate and thrust washer.

Discard O-ring from the gearbox cover.

(4)

Remove the bearing outer race and rollers from the helical torquemeter gearshaft.

(5)

Remove the ball bearing from the helical power takeoff gearshaft using 6796948 drift and

6796950 plate with detail -11. (Ref. FIG. 87) Remove the roller bearing inner race using

6796948 drift and 6796950 plate with detail -10.

(6)

Remove the internal retaining ring then remove the power train drive helical gear from the

gearbox cover. Remove the two ball bearings from the gear. Bearings which cannot be

removed using detail -23 of puller 6796950 kit with 6796948 drift shall be removed by pulling

at the outer race. Discard any bearings which have been pulled by the outer race.

(7)

Remove the internal retaining ring from the drive gear. Internal retaining rings are not used

with drive gears which incorporate an integrally-cast oil dam in place of a retaining ring groove.

(8)

Remove the fuel control spur gearshaft from the cover by removing the internal retaining ring

with 6796966 retaining ring pliers. Discard O-ring. (Ref. FIG. 88) Do not remove the pin or

splined adapter from the gearshaft. Remove the retaining ring and bearing retainer. (Ref.

FIG. 89) Remove the two bearings and the bearing spacer from the shaft using 6796946 drift

and 6796950 plate with detail -12.

Page 225

Rolls-Royce Engine 250–C18, 250–C18A, 250–C18B, 250–C18C. Operation and Maintenance Manual (2003) - page 10