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

E. Compressor Vane Repair

(1) Replace compressor case if damage to the vane cannot be blended out without reducing the

total width of the vane more than the limits given in Figure 52. Replace the compressor case

when after rework the vane total width is reduced more than the limits given in Figure 52 or

there are sharp edges, burrs, cracks or tears after rework.

F. Compressor Vanes Surface Damage. (See Figure 52)

(1) Blend and polish surface damage on the vanes.

(2) Replace the compressor case when:

(a) The reworked depth exceeds 1/2 of the vane thickness or

(b) Cracking is detected on the vane surface.

WARNING: CORROSION OR EROSION WILL CAUSE DAMAGE TO THE COMPRESSOR

BLADES AND VANES WHICH CAN RESULT IN ENGINE FAILURE.

G. Compressor Vane Erosion.

(1) Replace the compressor case when vane erosion exceeds the limits defined in Figure 53.

Compressor Rotor Blade Tip Blend Limits

FIG. 49

Page 165

92.

Compressor Case Plastic Coating Inspection (Yellow Plastic)

A. Acceptable.

(1) Loss of plastic between stator vanes.

(2) Cracks up to 1/2-in. (13 mm) long with no evidence of looseness.

(3) Blade rub if there is no evidence of discoloration at the blade tips.

(4) Erosion of the plastic coating but not to the extent of exposing any of the vane band adjacent

to the vanes or between the vanes in any stage. Vane thickness and chord dimensions must

be within the limits of Figure 53.

B. Unacceptable.

(1) Plastic separation from case ID in the rotor blade path.

(2) Missing plastic sections exceeding 3/8 x 1/2 in. (9.5 x 12.7 mm) in the rotor blade path

(3) Cracks in the plastic in the rotor path that exhibit evidence of curling.

93.

Compressor Case Plastic Coating Inspection (Black Plastic).

Acceptable.

(1) Cracks in any area provided there is no evidence of debonding, lifting or missing plastic in the

blade paths in stages 1 through 4. (Refer to Compressor Case Plastic Cracks Sealing)

(2) Debonding and loss of plastic between stator vanes in stages 4 through 6. Seal edges around

missing or loose plastic using the procedure Compressor Case Plastic Cracks Sealing.

(3) Erosion of plastic coating but not to the extent of exposing any of the vane band adjacent to

the vanes or between the vanes in any stage. Vane thickness and chord dimensions must be

within the limits of Figure 53.

(4) Blade tip rub in the plastic if there is no evidence of heat discoloration on any blade tip.

Unacceptable.

(1) Loss or removal of plastic sections exceeding 3/8 x 5/8 in. (9.5 x 15.9 mm) in the 5th- and

6th- stage blade paths. Remove loose sections of plastic in these stages. Seal the edges at

the missing or removed loose plastic sections using the procedure in Compressor Case Plastic

Cracks Sealing.

(2) Cracks in the plastic along the horizontal splitline exceeding 3/4 in. (19 mm) at any blade path.

Seal acceptable splitline cracks in accordance with Compressor Case Plastic Cracks Sealing.

Limits on Loss of Plastic.

(1) Loss of plastic can have an adverse effect on compressor performance and is a justified

reason for replacement of the case on low performance engines.

(2) If more than 50% of the plastic is missing between the vanes in stages 4 through 6, or if more

than 20% of the plastic is missing in the blade path of 5th- and 6th-stages, the case should be

replaced.

Page 169

94.

Compressor Case Plastic Coating Cracks Sealing

Apply silicone-resin sealer to plastic coating cracks found during maintenance inspection of

in-service compressor cases. This is an interim repair to aid the arrest of compressor case

corrosion that could contribute to vane-to-rotor rub problems. The procedure is recommended

especially for operators using water rinse as a routine maintenance practice.

(1) Disassemble one case half in accordance with Compressor Case Replacement.

(2) Inspect the case-half plastic coating in accordance with Compressor Case Plastic Coating

Inspection.

NOTE: The frequency of inspection and interim repair of compressor case plastic coating shall be

determined by judgement of the operator based on knowledge of the aircraft operating

environment. Inspection time periods of Inspection Checksheet, Table 8, must not be

exceeded.

(3) Apply silicone-resin sealer (item 37, Table 1) to plastic coating cracks as follows:

NOTE: Do not use sealer on areas without cracks. The application of sealer is of no benefit

until after the plastic has developed cracks.

(a) Wash the case ID surfaces with methylethylketone (MEK); thoroughly dry case before

application of sealer.

(b) Coat the surface of the plastic in the area of all cracks using a small brush or cotton tip

swab. Fill the cracks and exposed edges of the 5th-stage bleed slot. (Ref. FIG. 54)

(d) Allow the first coat to air dry for at least 10 minutes; then apply a second coat to the

cracks. Air dry the second coat for 15 minutes.

(e) Install the case half in accordance with Compressor Case Replacement.

(f)

Repeat the procedure with the second case half.

Page 171

Typical Plastic Coating Cracks

FIG. 54

95.

Compressor Front Support Inspection

A. Vanes.

(1) Cracks-none allowed.

(2) Dents-max. of 0.125 in. (0.635 mm). No punctures allowed.

(3) Bulged Vanes-bulges permitted. No cracks allowed.

B. Bullet Nose.

(1)

No evidence of damage allowed.

96.

Turbine-to-Compressor Coupling Spline Inspection

A. Inspect the turbine-to-compressor coupling splines after compressor removal, turbine removal or

turbine separation at the exhaust collector-to-power turbine support. Replace the coupling if

determined unacceptable.

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

splines allowed.

(2) Visually inspect the 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 the spline teeth for a wear

step. Any discernable wear that can be felt with the scribe is unacceptable.

Page 172

97.

Spur Adapter Gearshaft Aft Spline Inspection.

A. Inspect the spur adapter gearshaft aft spline whenever the compressor is removed. Return the

compressor to an Rolls-Royce Authorized Maintenance Center for replacement of an unacceptable

gearshaft.

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

splines allowed.

(2) Visually inspect the 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 the spline teeth for a wear

step. Any discernable wear that can be felt with the scribe is unacceptable.

98.

Compressor Case Replacement

A. Install a new compressor case as follows: (Ref. FIG. 55)

CAUTION: DO NOT REMOVE BOTH CASE HALVES AT THE SAME TIME.

NOTE: Compressor cases are machined in lower and upper matched sets. Rejection and

replacement of one case is cause for rejection and replacement of the opposite case

(half). Note the serial numbers on both replacement case halves to assure that the case

halves are a matched pair.

(1) Remove the pressure and scavenge oil lines between the gearbox and the compressor front

support.

(2) Remove the RH and LH lines between the anti-ice valve and the compressor front support.

(3) Remove the compressor bleed control valve as follows:

(a) Remove the bleed valve compressor discharge pressure sensing line.

(b) Remove three nuts, bolts and washers; remove the compressor bleed control valve and

gasket.

(4) Remove the top compressor case (half) as follows:

(a) Remove the 16 horizontal splitline nuts and bolts (four dowel bolts).

(b) Remove the 5 compressor case-to-compressor front support nuts and bolts.

Page 173

(d) Carefully lift the top case half straight out. If the case does not separate easily, loosen

the two bolts and nuts at the aft flange and one bolt and nut at the front flange adjacent to

each horizontal splitline.

NOTE: Note the location of the nameplate when the applicable compressor

case-to-compressor front support nuts and bolts are removed. Return the

nameplate to the same location during reassembly.

(5)

Install the new top case half as follows:

NOTE: Be sure that the splitline mating flanges are clean before installation of the

replacement case half.

(a) Carefully position the top case half over the rotor. Install a bolt and nut in the four dowel

bolt holes. If the dowel bolts do not align between old and new case halves, use bolt

positions at four adjacent holes instead. Torque the bolts to the minimum torque

necessary to close the horizontal splitlines.

NOTE: Torque all case splitline nuts to 10-15 lb in. (1.1-1.7 N^.m) plus locknut drag

unless otherwise specified. Locknut drag is the torque necessary to turn the nut

on the bolt in the last turn prior to seating of the nut. Lubricate bolts lightly with

engine oil before installation.

(b) Install and tighten two bolts and nuts in the rear flange of the top case half. Use the two

adjacent bolt holes midway between the horizontal splitlines (approximately 80 degrees

from the horizontal flanges). If the bolt holes in the rear flange do not align with the flange

holes in the front diffuser, loosen the rear flange bolts in the bottom case half to a snug fit.

Using a drift inserted into a misaligned bolt hole, rotate the case sufficiently to align the

holes. Tighten the two centermost bolts on the rear flange of the bottom case half; then

install and tighten the two centermost bolts and nuts in the rear flange of the top case

half.

bolt hole positions. Tighten the two outer bolts to a snug fit; then tighten the center bolt.

If the bolt holes in the front flange do not align with the flange holes in the front support,

loosen the front flange bolts in the bottom case half to a snug fit. Using a drift inserted

into a misaligned bolt hole, rotate the front support sufficiently to align the holes. Install

and tighten the three bolts and nuts.

(6)

Remove the bottom case half as follows:

(a) Remove the four bolts and nuts in the horizontal splitlines.

(b) Remove the five bolts and nuts in the bottom case half front flange.

(d) Carefully lift the bottom case half straight out. Do not pry against the top case half.

(7)

Install the new bottom case half as follows:

(a) Apply a sphere of approximately 0.12 in. (3 mm) dia of RTV 732, or equivalent (item 36,

Table 1), aft of the rearmost bolt hole on the bottom case half horizontal flange surfaces.

Assemble and tighten all splitline bolts and nuts as soon as possible after application of

RTV 732 (never exceed 30 minutes).

(b) The RTV 732 sealer is used to seal the rear corners of the splitline. Use of the sealer is

optional on engines that are not used with the water-cooled injection system.

four dowel holes at the horizontal flange. Tighten the bolts to the minimum torque

necessary to close the horizontal splitlines.

(d) Install and tighten two bolts and nuts in the rear flange of the bottom case half. Use the

bolt holes which are diametrically opposite the top case half bolts.

Page 175

(e) Install and tighten one bolt and nut in the front flange at the center hole position (90

degrees from the horizontal flanges).

(f)

Install the remaining 12 horizontal flange bolts and nuts; then tighten all bolts starting from

the rear and alternating from side to side.

(g) Install and tighten the remaining 12 bolts and nuts in the rear flange and the six bolts and

nuts, plus nameplate, in the front flange.

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(h) Attach the RH and LH anti-icing air tubes to the anti-icing valve and to the front support.

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

(i)

Attach the compressor oil tubes:

Install the gearbox elbow-to-front support scavenge oil tube. Torque coupling nuts

to 150-200 lb in. (17-23 N^.m).

Install the gearbox union-to-pressure reducer pressure oil tube. Torque coupling

nuts to 65-100 lb in. (7.3-11^.3 N.m).

(j)

Apply antiseize compound to the bolt threads; then install the bleed control valve and

gasket on the compressor case mounting flange. Retain with three nuts, bolts and

washers. Torque the 1/4-28 nut to 70-85 lb in. (7.9-9.6 N^.m); Torque the remaining two

nuts to 35-40 lb in. (3.9-4.5 N^.m). Install the bleed control valve pressure sensing line

between the elbows at the valve and the scroll. Torque coupling nuts to 80-120 lb in.

(9.0-13.6 N^.m).

(k) Turn the compressor rotor using 6799790 engine turning adapter (Q, FIG. 1) through the

starter-generator pad. Use a wrench to rotate the turning adapter. No blade tip rub

(evidenced by feel or noise) is acceptable. As an alternate method, motor the engine with

the starter and without ignition to 5-10% N speed. Listen for noise indicating a rub

condition caused by case misalignment.

(8)

Check run the engine after compressor case replacement. (Refer to Engine Check Run.)

99.

Compressor Front Bearing and/or Oil Seal Replacement (Engine Removed)

CAUTION: TO PREVENT ASSEMBLY DIFFICULTIES AND TO MINIMIZE POSSIBLE PART

DAMAGE, DO NOT REMOVE THE FRONT SUPPORT FROM THE COMPRESSOR

UNLESS THE ENGINE IS IN A VERTICAL ATTITUDE WITH THE COMPRESSOR

INLET ON TOP.

A. This is the preferred procedure for replacing the compressor front bearing or oil seal. Replace parts

with engine removed from the aircraft and installed in 6795579 turnover stand. Turn engine to a

vertical position in the stand with compressor inlet at the top. Replace the seal as follows: (Ref.

FIG. 56)

(1) Remove the pressure and scavenge oil lines between the gearbox and the compressor front

support.

(2) Remove the oil pressure reducer from the compressor front support. Discard O-ring.

NOTE: Any time the compressor front bearing and/or front bearing oil seal is replaced or the

oil system has been contaminated, disassemble and inspect the oil pressure reducer.

(a) Remove the internal retaining ring; then separate the restrictor from the oil pressure

reducer body. (Ref. FIG. 56)

(b) Clean all debris from the restrictor and the body using mineral spirits and a soft bristle

brush.

Page 176

condition exists.

(d) Reassemble the oil pressure reducer by installing the restrictor threaded end first into the

body. (Ref. FIG. 56) Secure with the internal retaining ring. Be sure the retaining ring is

properly seated in the groove in the body.

(e) Lubricate a new O-ring and install it with the oil pressure reducer in the compressor front

support. Torque to 50-75 lb in. (5.6-8.5 N⋅m).

(3)

Remove the RH and LH lines between the anti-ice valve and the compressor front support.

(4)

Remove the starter-generator.

(5)

Remove the Pc air line between the bleed valve and the scroll.

(6)

Remove three nuts, bolts and washers and separate the bleed control valve and gasket from

the mounting flange on the compressor case.

(7)

Remove the compressor front support nut. Remove 10 bolts and nuts at the front support

flange.

(8)

Loosen, but do not remove, the compressor case splitline nuts and bolts.

(9)

Separate the compressor front support from the compressor assembly. Discard two O-rings.

The identification plate is removed by this operation.

(10) Remove the front bearing housing by compressing the internal retaining ring and lifting the

housing off the bearing.

(11)

Remove the helical spring and spring cup from the rotor.

(12) If it is necessary to replace or reseat the bearing damper in the front bearing housing, remove

the damper using 6799700 puller. (Ref. FIG. 57)

Compressor Front Bearing Vibration Damper Removal

FIG. 57

Page 178

CAUTION: DO NOT HOLD OR TURN THE N1 GEAR TRAIN THROUGH THE SPARE DRIVE

PAD. THIS COULD RESULT IN DAMAGE TO THE GEARBOX.

CAUTION: EXERCISE CARE WHEN REMOVING THE COMPRESSOR BEARING NUT. DO

NOT ALLOW THE NUT WRENCH TO CONTACT THE BEARING.

CAUTION: THE COMPRESSOR FRONT BEARING CAN BE DAMAGED EASILY. REPLACE

BEARING IF AT ANY TIME DURING REMOVAL OR INSTALLATION THE

BEARING IS DROPPED, LOADED THROUGH THE BALLS TO THE INNER RACE

OR THE OUTER RACE IS PULLED OFF.

(13) Remove the bearing retaining nut using a socket wrench with a broach depth no more than

7/16 in. (11 mm) (Snap-On SW 181 or equivalent). Hold the rotor from turning using 6799790

adapter in the starter-generator pad on the gearbox cover.

(14) For front compressor bearing configuration without a puller groove, install a 6796952 puller on

the puller groove of the seal mating ring and pull both the seal mating ring and bearing

together. For front bearing configurations with a puller groove, remove the bearing first using

23005023 puller followed by removal of the seal mating ring using the same puller. (Ref. FIG.

58)

(15) Remove the oil seal from the rotor. Discard O-ring.

(16) If the vibration damper was removed, install the replacement damper or reseat the old damper

as follows:

(a) Install the vibration damper on 6798796 drift. Chill the damper and the drift using dry ice.

As an option, the bearing housing may be heated to 121°C (250°F) maximum.

(b) Press the damper into the front bearing housing until it bottoms out against the shoulder

of the bearing housing. Apply constant pressure to the drift until such time the

temperature of the damper and the housing have equalized. Remove the drift.

1.218 in. (30.94 mm) minimum from the housing open end.

Page 179

Compressor Front Bearing and Seal Mating Ring Removal

FIG. 58

(17) Lubricate inside the replacement seal with engine oil (by soaking). Install lubricated O-ring on

the seal; then install the seal on the rotor.

CAUTION: USE A RETAINING NUT WITH A BLACK NYLON CAP WITH NO. 1 BEARINGS

HAVING A PULLER GROOVE. USE RED OR YELLOW NYLON CAP NUTS WITH

BEARINGS WITHOUT PULLER GROOVES. IN ORDER FOR THE

SELF-LOCKING FEATURE OF THE RETAINING NUT TO BE EFFECTIVE AND

TO AVOID OIL LEAKAGE INTO THE ROTOR, DO NOT INTERCHANGE THESE

NUT/BEARING COMBINATIONS.

CAUTION: EXERCISE CARE WHEN INSTALLING THE NUT. DO NOT ALLOW THE

WRENCH TO CONTACT THE BEARING.

(18) Install the seal mating ring (pulling lip forward) and the bearing (wire clip or pulling lip forward)

on the compressor rotor. Secure with a nut. Torque nut to 120-130 lb in. (14-14.7 N^.m)

above torque due to locknut drag. Loosen and retorque to 70-80 lb in. (7.9-9.0 N^.m) above

torque due to locknut drag. Use a socket wrench with a broach depth of no more than 7/16 in.

(11 mm) (Snap-On SW 181, or equivalent). Hold the rotor from turning using 6799790

adapter in the starter-generator pad on the gearbox cover.

(19) Install the spring and spring clip. The cup sleeve fits over the spring on the end that contacts

the bearing.

(20) Install the bearing housing on the rotor shaft. Press down on the housing (rearward) until the

prongs on the retaining ring engage the slot in the housing. Support the oil seal, press down

on the housing and engage the retaining ring. Lubricate and install two O-rings on the bearing

housing.

Page 180

CAUTION: DO NOT FORCE THE SUPPORT FLANGE INTO THE COMPRESSOR CASE

PILOT--LOOSEN THE COMPRESSOR CASE HORIZONTAL SPLITLINE BOLTS

AS NECESSARY FOR EASE OF ASSEMBLY, EVEN TO THE POINT OF

REMOVING ONE CASE HALF.

(21) Install the front support on the compressor assembly. This part is indexed correctly when the

scavenge oil fitting is at the bottom of the compressor. Lubricate the threads of the front

bearing housing with antiseize compound. Secure housing to the front support with a nut.

Torque nut to 35-40 lb in. (3.9-4.5 N^.m). Install the identification plate and ten

support-to-compressor case bolts and nuts. Torque the compressor horizontal splitline and

front support splitline nuts to 10-15 lb in. (1.1-1.7 N^.m) plus locknut drag. Tighten the four

shouldered bolts first when tightening the case splitline nuts.

(22) Apply antiseize compound to the bolt threads; then install the bleed control valve and gasket

on the compressor case mounting flange. Retain with three nuts, bolts and washers. The

1/4-28 bolt goes in the LH hole (looking forward). Torque the 1/4-28 nut to 70-85 lb in.

(7.9-9.6 N^.m). Torque the other two nuts to 35-40 lb in. (3.9-4.5 N^.m).

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(23) Attach the compressor discharge pressure sensing tube assembly between the bleed valve

and the scroll. Torque coupling nuts to 80-120 lb in. (9.0-13.6 N^.m).

(24) Attach the RH and LH anti-icing air tubes between the anti-icing valve and to the front

support. Torque coupling nuts to 150-200 lb in. (17-23 N^.m).

(25) Check the oil seal for leakage by applying oil at 4-6 psi (27.6-41.4 kPa) for one minute to the

oil pressure reducer location on the compressor front support. No leakage shall be permitted.

(26) Attach the compressor pressure and scavenge oil tubes:

(a) Install the gearbox-to-front support scavenge oil tube. Torque coupling nuts to 150-200

lb in. (17-23 N^.m).

(b) Install the gearbox union-to-pressure reducer pressure oil tube. Torque coupling nuts to

65-100 lb in. (7.3-11.3 N^.m).

(27) Install the starter-generator.

After complete assembly of the compressor, check the compressor rotor for freedom of operation.

If compressor drag or rubbing is detected either by feel or by sound, investigate to determine the

cause by removing one or both halves of the case assembly.

Check run the engine after seal or bearing replacement. (Refer to Engine Check Run.)

100. Compressor Front Bearing and/or Oil Seal Replacement (Engine Installed)

A. This is an alternate procedure for replacing the front bearing and/or oil seal while the engine is

installed and in a horizontal position.

CAUTION: THIS ALTERNATE PROCEDURE INVOLVES GREATER RISK OF PART DAMAGE AND

ASSEMBLY ERROR THAN THE PREFERRED PROCEDURE (PARA 99). THE

ALTERNATE PROCEDURE IS RECOMMENDED ONLY FOR SKILLED MECHANICS

HAVING APPROVAL OF THEIR DISTRIBUTOR.

(1) Support the compressor rotor in the compressor case by carefully installing shim stock

between the 1st-stage wheel blade tips and the case halves. Install the shim stock through

the open end of the compressor front support at three equally spaced locations.

CAUTION: IN ORDER TO ENSURE THAT REMOVAL OF THE SHIM STOCK IS NOT

OVERLOOKED AT REASSEMBLY, IT IS SUGGESTED THAT A STRING OR

STREAMER BE ATTACHED TO THE PROTRUDING END OF THE SHIM STOCK

BEFORE THE STOCK IS INSERTED INTO THE COMPRESSOR.

(2) Replace the compressor front bearing and/or oil seal in the same manner as used in the

Engine Removed procedure (sub para A (1) through sub para B of para 99).

Page 181

(3) Remove the shims from between the first-stage wheel blade tips and the case halves.

B. Check run the engine. (Refer to Engine Check Run.)

101. Compressor Assembly Replacement

A. Remove and inspect the compressor assembly as follows: (Ref. FIG.59)

(1) Remove the following items:

(a) Compressor oil supply and scavenge lines from the compressor front support and from

the power and accessories gearbox. Remove the oil pressure reducer from the front

support.

(b) Fuel control system compressor discharge pressure (Pc) sensing line. Remove tube from

the diffuser scroll pressure probe elbow and from the governor. On engine configurations

with the Pc filter, hold the filter while disconnecting the coupling nut.

(2) Remove the compressor discharge pressure sensing tube at the compressor bleed control

valve and at the diffuser scroll pressure probe elbow.

(3) On control system configurations A or B, remove the two pressure probe elbows from the

diffuser scroll.

(Ref. FIG. 8 and 9) On configuration C remove the pressure probe elbow and

Pc filter from the scroll.

(Ref. FIG. 10)

1. Oil Supply Tube

8. Anti-icing Air Valves

2. Oil Scavenge Tube

9. Bolt (5)

3. Control Sensing Tube

10. Washer

4. Bleed Valve Sensing Tube

11. Coupling

5. Pressure Probe Elbow (2)

12. O-ring

6. Bleed Valve

13. O-ring

7. Anti-icing Air Lines (2)

14. Shim

Compressor Removal

FIG. 59

Page 182

(4)

Remove the nut and separate the anti-icing valve from the diffuser scroll.

(5)

Remove the three bolts, nuts and washers and separate the compressor bleed control valve

and gasket from the compressor case.

(6)

Remove the two anti-icing lines at the compressor front support and at the anti-icing valve.

(7)

If the compressor assembly is to be reinstalled, count and record the number of shims at each

mounting pad prior to complete removal of the compressor. Save the shims for reuse.

Remove the nuts and washers at the two pads inboard on the gearbox and remove the three

bolts at the outboard pads. Note the position of the three different bolts and one washer used

at these pads. Separate the compressor from the gearbox.

NOTE: Early engines incorporate 5 bolts to attach the compressor to the gearbox.

(8)

Remove the turbine-to-compressor coupling from the spur adapter gearshaft.

(9)

Make the following inspection of the compressor discharge air tube seal groove lands and 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.

(10) Inspect the compressor attachment inserts in the gearbox housing for looseness. (Refer to

Compressor Insert Inspection.)

WARNING: FAILURE TO PROPERLY SHIM THE COMPRESSOR AT INSTALLATION CAN CAUSE

THE SPUR ADAPTER GEARSHAFT TO FAIL RESULTING IN SUDDEN ENGINE

STOPPAGE.

CAUTION: BE SURE THE SPUR ADAPTER GEARSHAFT IS IN MESH WITH THE GEARBOX

MATING GEAR BEFORE TIGHTENING COMPRESSOR RETAINING BOLTS.

B. Install the replacement compressor as follows:

NOTE: Check to ensure that the compressor and gearbox mounting flanges are clean and free of

foreign material which could cause misalignment.

(1) Place new packings on the compressor rear diffuser and the spur adapter gearshaft. Position

the turbine-to-compressor coupling on the spur adapter gearshaft. Determine the number of

shims required for compressor installation. When replacing a compressor, the quantity of

0.002 in. (0.05 mm) shims required at each attaching point has been determined during

compressor buildup (overhaul) and marked on the appropriate bolt hole on the rear diffuser.

When reinstalling a compressor, install with the quantity of shims marked on the rear diffuser.

If the shim markings are not legible, not present, or in doubt, compute the total shim thickness

requirements in accordance with paragraph 102. Place the compressor on the gearbox with

the required quantity of shims in place at the bolt pads. If interference is encountered between

the compressor and one of the cast bosses on the gearbox, lightly dress the boss by filing.

Remove only sufficient material to provide a positive clearance. Dichromate the machined

area per AMS 2475. Apply engine gray enamel (AMS 2510). Use the same configuration of

bolts, nuts and washers at each of the five compressor pads as was previously used. (If the

gearbox is changed, different bolts or nuts may be required.) Use 6799790 engine turning

adapter (Q, FIG. 1) to turn the gear train until it meshes with the spur adapter gearshaft.

Torque attachment features to 70-85 lb in. (7.9-9.6 N^.m) and secure bolts with lockwire.

Page 183

(2) Install the anti-icing valve on the diffuser scroll.

(Refer to Anti-Icing Air System.)

(3) On control system configurations A or B, apply antiseize compound lightly to the threads; then

install the two pressure probe elbows with new O-rings in the diffuser scroll. Do not torque

jam nuts until final tube alignment is made.

(4) On control system configuration C, apply anti-seize compound lightly to the threads of the

bleed air valve Pc pressure probe elbow. Install the elbow with a new O-ring in the diffuser

scroll. Mask the filter body and Pc probe of the Pc filter. Apply a light, even coat of bonded

lubricant to the threads at the probe end of the filter (Electrofilm Lubri-Bond A Resin,

Molybdenum Disulfide Solid Film Lubricant, or equivalent.) Allow the lubricant a minimum of

30 minutes to air dry. Install the Pc filter with new O-ring in the compressor scroll. Torque

filter to 75-85 lb in. (7.9-9.6 N^.m).

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(5) Install pressure sensing line between bleed valve and diffuser scroll elbows. Torque coupling

nuts to 80-120 lb in. (9.0-13.6 N.m). Torque elbow jam nuts to 55-80 lb in. (6.2-9.0 N^.m) and

secure with lockwire.

(6) Install the pressure sensing line between the tee at the governor and the diffuser scroll. On

engine configurations with the Pc filter, attach the scroll-to-Pc filter tube assy to the scroll and

to the forward end of the Pc filter. Attach the Pc filter-to-power turbine governor tube. Hold

the filter with the proper wrench at the hex flats of the filter assembly. Torque the coupling nuts

to 80-120 lb in. (9.0-13.6 N^.m). Torque elbow jam nut to 55-80 lb in. (6.2-9.0 N^.m) and

secure with lockwire. Clamp Pc filter-to-governor tube to ignition lead.

(7) Install the pressure reducer and oil supply and scavenge lines to the front support and to the

gearbox. Torque reducer to 50-75 lb in. (5.7-8.5 N^.m) and pressure oil tube coupling nuts to

65-100 lb in. (7.3-11.3 N^.m). Torque scavenge oil tube coupling nuts to 150-200 lb in. (17-23

N^.m).

(8) Make appropriate entry relative to compressor replacement in the Engine Log.

Check run the engine and select the proper size diffuser vent orifice after compressor replacement.

(Refer to Engine Check Run.)

102. Compressor Mounting Shim Thickness Requirements Determination

A. Position the compressor assembly in a vertical position (on blocks) with the impeller end up.

NOTE: Be sure the spur adapter gearshaft is match-marked to the impeller hub prior to removal.

B. Before removing the spur adapter gearshaft from the compressor assembly, match-mark the spur

adapter gearshaft to the impeller hub.

C. Using 6795588 wrench to hold the rotor and a six-point socket on the nut, remove the retaining nut

securing the spur adapter gearshaft in the impeller hub. Use 6798250 puller, remove the gearshaft

from the impeller hub.

D. Install the plate of 6873066 fixture on the aft side of the rear diffuser.

E. Attach the indicator and bracket on the impeller hub.

F. Level the plate using the three leveling screws and the bracket mounted indicator.

G. Position the dial indicator on the plate to contact the five mounting pads (C, FIG. 60). Record the

reading at the five positions.

H. Zero the indicator at the highest of the five positions. Measure and record the minus reading at

each of the other four positions.

Compute the total thickness of shims required to build the four (low) bolt holes up to the zero

indicated hole as required to obtain an installed compressor squareness of 0.002 in. (0.05 mm) FIR.

Page 184

The total thickness of shims at any one location shall not exceed 0.020 in. (0.51 mm). Electro-

chemically etch the total shim thickness adjacent to the applicable bolt hole and cover the etched

surface with Metcoseal AMS 3135 transparent silicone resin. Mark the zero indicated hole with a 0

(zero).

(Ref. FIG. 60) Shims are available in three sizes; 0.002, 0.004, and 0.008 in. (0.05, 0.10,

0.20 mm).

Remove the 6873066 fixture.

K. Align the match marks and install the spur adapter gearshaft in the splines of the impeller hub.

Retain the gearshaft with a retaining nut. Hold the gearshaft with the 6795588 wrench and torque

the nut to 50-55 lb in. (5.6-6.2 N@m) above locknut drag using a six-point socket.

L. Align the matchmarks and install the spur adapter gearshaft into the splines of the adapter coupling.

Retain the gearshaft in the coupling with the internal retaining ring.

Compressor Rotor Squareness Measurement

FIG. 60

Page 185

103. Turbine Assembly Maintenance

WARNING: AN ENGINE WHICH HAS BEEN OPERATED ON LEADED FUEL HAS A PALE

YELLOW POWDER RESIDUE ON THE EXHAUST PASSAGES. HANDLING LEAD

RESIDUE COATED PARTS BY PERSONS WITH OPEN CUTS OR SCRATCHES ON

THEIR HANDS CAN BE EXTREMELY DANGEROUS. ALWAYS WEAR GLOVES

WHEN HANDLING RESIDUE COATED PARTS.

Turbine Blade and Vane Inspection

(1) Inspect the 1st-stage turbine blades and vanes with the combustion section removed. (Refer

to Combustion Liner Replacement.) Inspect the 4th-stage turbine blades through the exhaust

ducts.

Turbine Blade Damage

(1) Replace the turbine assembly if any of the following conditions exist:

(a) Damage to inner 1/3 of blade.

(b) Blade or stator vane broken off.

(d) Melted vane or blade.

Power Turbine Shaft Spline Inspection

(1) Inspect the power turbine shaft splines whenever the engine has been subjected to a sudden

stoppage as defined in Sudden Engine Stoppage Inspection or whenever turbine is removed.

Return the turbine to an Rolls-Royce Authorized Maintenance Center for replacement of an

unacceptable shaft. (Refer to FIG. 61)

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

splines are allowed.

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

are allowed.

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

Any discernable wear step that can be felt on the scribe in unacceptable.

Turbine-to-Pinion Gear Coupling Shaft Spline Inspection

(1) Inspect turbine-to-pinion gear coupling shaft splines whenever turbine is removed. Replace

coupling shaft if determined unacceptable.

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

splines allowed.

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

allowed.

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

Any discernable wear step that can be felt on the scribe in unacceptable.

1st-stage Turbine Nozzle and Nozzle Shield Inspection

(1) The inspection limits and disposition regarding specific conditions which may be encountered

are given in Table 14. The limits given in the table are defined as follows:

(a) Serviceable limit is the maximum degree of a specified condition which can be accepted,

allowing the part to be placed back into service without repair.

(b) Repairable limit is the maximum degree of a specified condition which can be repaired.

Any condition exceeding the limit cannot be corrected by the specified repair procedure;

therefore, the part must be condemned.

104. 1st-stage Turbine Nozzle or 1st-stage Turbine Nozzle Shield Replacement

A. Replace the 1st-stage turbine nozzle shield using the applicable part of the following 1st-stage

turbine nozzle replacement procedure.

(1) Remove the firewall shield. (Refer to Firewall Shield Removal and Replacement.)

Page 186

(2) Remove drain hoses from the exhaust collector support and from the burner drain valve.

(3) For engines without a Pc filter, remove the pressure sensing line from the diffuser scroll and

the tee at the governor. For engines with a Pc filter, remove the Pc filter-to-governor tube.

Hold filter while disconnecting tube.

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

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

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

from the compressor. (Ref. FIG. 62)

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

discharge air tubes when tubes are separated from diffuser scroll and firewall.

(5) Remove the five nuts at the splitline and separate the turbine from the power and accessories

gearbox.

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

O-rings.

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

(8) Attach the turbine assembly to the supporting adapter (M, FIG. 1), at the three exhaust

collector support bolt holes, with the gas producer support up.

Page 187

Table 14

1st-Stage Turbine Nozzle and Nozzle Shield Inspection

Serviceable

Repairable

Item

Condition

Limit

Limits

Disposition

1st-Stage Nozzle

Axial crack in vane air-

Leading edge 1/4 in. (6

Leading edge 3/8 in. (10

Gas tungsten-arc weld

foil

mm) max; trailing edge

repair using X40 (EMS

5/16. (8mm) max.

3/8 in. (10 mm) max.

70175) or alternate

a. No two cracks in

Haynes 188 (AMS

same plane.

5801). Anneal at 1066

b. Adjacent cracks 1/4 in

+ 14°C (1950 + 25°F

(6 mm) apart.

for one hour. Rapid air

c. Adjacent cracks not

cool. Restore to origi-

progressing toward

nal contour by grinding

each other.

with fine grit stone.

Nicked or dented lead-

Leading edge 1/16 in.(2

(2.4 mm) max; trailing

Repair by blending

ing and trailing edge.

mm) max; trailing edge

edge 5/32 in. max (4

with fine grit stone.

Warped or burned trail-

1/8 in. (3 mm) max.

mm) max. Max of three

ing edge only.

adjacent vanes and total

of eight vanes.

Weld repair and re-

Leading edge 1/8 in. (3

store to original con-

mm) max; trailing edge

tour by grinding with

1/4 in. (6 mm) max.

fine grit stone.

Fillet cracks-inner and

Leading edge 1/4 in. (6

Leading edge 3/8 in. (10

Weld repair as in Item

outer band.

mm) max; trailing edge

1/8 in. (3 mm) max.

3/16 in. (5 mm) max.

Inner band.

Leading edge 3/16 in. (5

Leading edge 3/8 in. (10

Weld repair as in Item

mm) max axially into the

mm) max axially. Trail-

band and not in line with

ing edge extending

trailing edge cracks Trail-

through inner band to

ing edge-- extending

sheet

through inner band to

sheet metal detail.

Outer band leading and

Extending 3/16 Extend-

Extending 1/2 in (13 mm)

Weld repair as in Item

trailing edges

ing 1/2 in in. (5 mm) ax-

axially into the band and

ially into the band and

not in line with crack on

opposite edge.

opposite edge Extending

1/2 in. Sheet metal

Sheet metal diaphragm

Extending 1/2 in. (13

None.

Replace nozzle.

mm) circumferentially,

max of two cracks at

least two in. (50.8 mm)

apart.

1st-stage Nozzle Shield

Cracks around spot-

Cracks are accept-

Up to 100% cracking in

Inert gas weld using

welds on heat shield.

able provided the

all welds

filler material class 13.

length of the crack is

not greater than 50%

of the distance

around the weld.

Page 189

NOTE: It may be necessary to reverse the three turbine attaching studs on the supporting

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

(9)

Clamp holding wrench (J, FIG. 1) on the supporting adapter. The wrench fits through the

power turbine drive and on the gas producer turbine rotor drive spline. The wrench is secured

by two handknobs.

(10) Remove the two positioning plugs and separate the 1st-stage turbine nozzle shield from the

turbine.

(Ref. FIG. 63)

(11)

Remove G-type retaining ring.

(12) Remove the gas producer turbine sump and nut assembly using 6798047 sump wrench (L,

FIG. 1).

(13) Remove and discard metallic U-ring gasket.

(14) Remove the gas producer turbine bearing oil nozzle using 6796920 puller (F, FIG. 1).

(15) Remove the bearing retaining plate (retaining ring on some configurations).

(16) Remove the spanner nut using 6798046 bearing locknut wrench (K, FIG. 1). (This nut has a

left-hand thread.)

(17) On applicable configurations pull the gas producer turbine ball bearing inner half race using

6795590 puller (B, FIG. 1). Do not pull the one-piece bearing at this time.

(18) Remove the No. 8 bearing and then the rotating labyrinth seal using 6795590 puller (B, FIG.

1).

(19) Remove the 24 nuts and bolts from the splitline; then lift the gas producer turbine support from

the turbine.

(20) Remove and discard the two metallic ring gaskets at the balance piston air tube locations of

the gas producer turbine support.

NOTE: The 2nd-stage nozzle tang is match marked opposite the small hole on the power

turbine and gas producer support flanges. If this marking is not visible, remark it

immediately after the gas producer turbine support is removed, before the gas

producer turbine rotor has been moved in any manner.

(21) Remove lockwire and five bolts at the rear of the gas producer turbine support; remove the

1st-stage turbine nozzle. On some engines a bellows seal will be removed with the nozzle.

Use of the bellows seal and the 11.12 in. (282.4 mm) length of fiberglass packing at this

location has been discontinued. Discard the bellows seal and fiberglass packing.

Page 190

Install the 1st-stage turbine nozzle as follows: (Ref. FIG. 63)

(1)

Install the 1st-stage turbine nozzle in the gas producer turbine support. Retain with five bolts;

coat bolt threads lightly with antiseize compound before installation. Before torquing the bolts,

install the

1st-stage nozzle shield and use it to final position the 1st-stage nozzle. When the

nozzle is positioned, remove the shield and torque the bolts to 35-40 lb in. (3.9-4.5 N^.m) and

secure with lockwire. Recheck installation of the 1st-stage nozzle shield after torquing the

bolts.

(2)

With the turbine installed in 6798089 supporting adapter (M, FIG. 1) and with the rotor retained

by 6798045 holding wrench (J, FIG. 1), position the index mark on the tang of the 2nd-stage

nozzle in alignment with the small hole in the power turbine support flange. Place preformed

fiberglass packing in the 1st-stage turbine nozzle and the two metallic ring gaskets in the

balance piston air tube openings; then install the gas producer turbine support on the turbine.

The power turbine and gas producer turbine supports are properly indexed when the balance

piston air tubes are aligned. When the gas producer turbine support is properly seated in the

tang slots, retain it with 24 bolts and nuts. Coat bolt threads lightly with antiseize compound

before installation. The three half-inch (13 mm) bolts go at positions 2, 3, and 20 counting

clockwise with 1 at top center when looking forward. Torque nuts of 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) plus

prevailing torque.

NOTE: It may be necessary to use petrolatum to retain the metallic ring gaskets during this

assembly.

(3)

Lubricate (engine oil) and install the rotating labyrinth seal and the gas producer turbine ball

bearing assembly on the gas producer using 6895538 press (T, FIG. 1 with detail -7).

(4)

Install the bearing in the position noted at disassembly.

(5)

Lubricate (engine oil) and install the spanner nut using 6798046 bearing locknut wrench (K,

FIG. 1). Torque nut (left-hand thread) to 150-175 lb in. (17-20 N^.m) and stake nut edge into

lock detent using 23003262 crimper.

(6)

Install the gas producer bearing oil nozzle using 6796920 puller (F, FIG. 1). Be sure the

anti-rotation pin aligns with the index slot of the oil nozzle. If the pin does not engage the slot

of the nozzle, stake the pin into the slot in such a manner that the nozzle can be removed

without removal of the pin. Replace pin having cracks or tears in the staked surface.

(7)

Establish the fully seated position of the sump and nut assembly as follows:

(a) Position the bearing retaining plate against the bearing. Use the pin in the support and

the small slot in the plate for the index location. Do not install the U-ring gasket during

the measurement build-up.

(b) Lightly lubricate the threads with antiseize compound; then install the sump and nut

assembly using the sump wrench (L, FIG. 1). Torque the sump and nut assembly to

40-50 lb ft (54-68 N^.m) so that it is seated against the bearing retaining plate.

sump and nut assembly and the gas producer support castellations. This index mark

indicates the fully seated sump and nut angular position.

(d) Remove the sump and nut assembly using sump wrench (L, FIG. 1).

Page 193

CAUTION: FAILURE TO PROPERLY INDEX THE BEARING RETAINING PLATE MAY

RESULT IN AN INTERNAL ENGINE FIRE CAUSED BY OIL LEAKING PAST

THE NO. 8 BEARING LABYRINTH SEAL.

CAUTION: BE SURE THE CORRECT SIZE METALLIC U-RING GASKET IS INSTALLED.

THE CORRECT SIZE GASKET FITS AROUND THE OD OF THE RETAINING

PLATE. (REF. FIG. 64) IMPROPER GASKET FIT OR INSTALLATION

ALLOWS INCREASED AIR PRESSURE IN THE AREA OF THE NO. 8

BEARING. INCREASED AIR PRESSURE FORCES OIL THROUGH THE

LABYRINTH SEAL ONTO THE FIRST-STAGE TURBINE WHEEL.

WARNING: OIL CONTACTING THE HOT TURBINE WHEEL CAN CAUSE EXCESSIVE

TEMPERATURE AND ULTIMATELY CAUSE WHEEL FAILURE.

(e) Carefully coat the threads of the sump and nut assembly with antiseize compound.

Position the metallic U-ring gasket in the sump. Position the bearing retaining plate

against bearing. Use the pin in the support and small slot in the plate for index location.

Install the sump and nut assembly using 6798047 sump wrench (L, FIG. 1). Tighten until

the nut is seated and the white reference index marks are aligned. If the torque required

to align the reference mark is less than 60 lb ft (81 N^.m), or greater than 160 lb ft (217

N^.m), replace the U-ring gasket with a new part.

(8) Perform a leak check of the No. 8 bearing sump area to ensure proper seating of the U-ring

gasket. (Refer to U-ring Gasket Installation Leak Check.)

Metallic U-ring Gasket Installation

FIG. 64

Page 194

(9)

Install the G-type retaining ring.

(10) Install the 1st-stage turbine nozzle shield on the turbine. Retain with two positioning plugs.

Coat threads of plugs lightly with antiseize compound before installation. Torque positioning

plugs to 100-150 lb in. (11-17 N^.m) and secure with lockwire.

(11)

Remove the turbine from the supporting adapter.

(12) 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).

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

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

the turbine rotor.

(Some configurations have only one O-ring.) Be sure the coupling is

installed on the rotor of the turbine with the end having the four equally spaced grooves out

(toward the gearbox)

(14) Install the turbine on 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. Coat stud threads lightly with antiseize compound before installation

of 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).

(15) Place the packing, seal ring, and wave washer over the small end of one compressor

discharge air tube. Space the split seal ring gaps 180° apart and apply antiseize compound to

the rings. Insert the tube through the firewall into the diffuser scroll. Use 6799953 installation

clamp (S, FIG.1) to compress the split seal ring. Install the second compressor discharge air

tube in the same manner.

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

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

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

(18) Compress the seal rings with 6799952 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 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 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.

(19) Install the firewall shield.

(Refer to Firewall Shield Removal and Replacement.)

(20) Install drain hoses at the burner drain valve and exhaust collector support.

(21) For engines without a Pc filter, install the pressure sensing line between the diffuser scroll and

the tee at the governor. For engines with a Pc filter install the scroll-to-Pc filter tube and the

Pc filter-to-governor tube. Hold the filter while connecting the tubes. Torque coupling nuts to

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

(22) Check run the engine following replacement of the turbine nozzle. (Refer to Engine Check

Run.)

105. U-ring Gasket Installation Leak Check

A. Perform an air leakage check of the No. 8 bearing sump area to ensure proper seating of the

metallic U-ring gasket. (Ref. FIG. 64) Perform this check any time the sump and nut has been

removed. The following equipment and procedures are required for the No. 8 bearing sump

pressure check:

(1) Shop air supply with pressure regulator, appropriate filtration fittings and lines as required to

introduce clean, dry air into the No. 8 bearing scavenge fitting.

Page 195

Rolls-Royce Engine 250–C18, 250–C18A, 250–C18B, 250–C18C. Operation and Maintenance Manual (2003) - page 9