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

Refer to Section I, Oil Specification and Approved Oils when servicing oil.

WARNING: ONLY DISCRETIONARY MIXING OF OILS WITHIN AN OIL SERIES IS

PERMITTED WITHOUT A TIME PENALTY. USE OF MIXED OILS FROM

DIFFERENT SERIES IN AN ENGINE IS LIMITED TO FIVE HOURS TOTAL

RUNNING TIME DURING ONE OVERHAUL PERIOD. ADEQUATE

MAINTENANCE RECORDS MUST BE MAINTAINED TO ENSURE THAT THE FIVE

HOUR LIMIT IS NOT EXCEEDED. FAILURE TO COMPLY WITH OIL MIXING

RESTRICTIONS CAN RESULT IN ENGINE FAILURE.

WARNING: FAILURE TO COMPLY WITH OIL MIXING RESTRICTIONS CAN RESULT IN

ENGINE FAILURE.

(7) Fill the oil supply tank with approved oil. Refer to Approved Oils, Section 1. and refer to

Airframe Manual for proper quantity of oil.

(8) Motor the engine with the starter and without ignition until an indication of oil pressure is

attained. When pressure is evidenced, start the engine and operate at Idle for five minutes.

Monitor oil pressure continuously during the five minute run.

(9) Make a notation of the oil change in the Engine Log book.

CAUTION: REMOVE AND INSPECT THE OIL FILTER EACH 25 HOURS OF ENGINE

OPERATION IF THE TYPE OF OIL (MIL-PRF-7808 OR MIL-PRF-23699) IS

CHANGED. REPEAT THE FILTER INSPECTION EACH 25 HOURS AS

REQUIRED UNTIL EXCESSIVE CARBON PARTICLE ACCUMULATION

SUBSIDES.

CAUTION: THE FILTER INSPECTION IS TO DETERMINE IF COKE, WHICH WAS FORMED

DURING PREVIOUS OPERATION, IS BEING DISLODGED DURING THE INITIAL

OPERATION FOLLOWING THE OIL CHANGE.

CAUTION: IF HEAVY CARBON DEPOSITS ARE OBSERVED ON THE ENGINE FILTER, IT IS

SUGGESTED THAT THE ENGINE OIL BE CHANGED AGAIN. THE OIL IS TO BE

DRAINED WHEN THE OIL IS HOT TO OBTAIN THE MAXIMUM BENEFIT. THE

25-HOUR OIL MONITORING IS TO CONTINUE UNTIL THE NEXT OIL CHANGE

PERIOD.

CAUTION: USE OF OILS WHICH ARE NOT INCLUDED IN THE APPROVED OILS LISTING

OR FAILURE TO DRAIN OIL WITHIN THE PRESCRIBED INTERVAL GIVEN IN

TABLE 8 WILL BE CONSIDERED AS MISUSE UNDER ITEM (4) OF THE

WARRANTY POLICY.

74.

Removed

75.

Engine Oil Filter Maintenance

A. Remove, inspect, clean, and install the oil filter as follows: (See Figure 32)

(1) Place a cloth between the gearbox and the turbine to catch oil which will overflow the element

housing when the cap is removed.

(2) Remove two nuts and washers; then using 6798860 puller, remove the oil filter cap. Use a

suction gun or other suitable device to remove the puddled oil from the filter housing before the

element is removed.

(3) Remove the filter element and packing on applicable configurations from the housing. Discard

the packing.

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(4) Inspect the filter element and filter cavity for metal particles. A small amount of metal debris

may be expected after recent overhaul or repair. If excessive metal contamination is present,

clean the filter and perform a ground run for 30 minutes with the rotor turning. Check the filter

after the ground run for new accumulation of particles. If the filter is clean, release the aircraft

for flight. If accumulation persists, repeat the cleaning and ground run. If accumulation is

present after the second ground run, tag the engine noting the cause for rejection.

(5) Clean the filter ultrasonically in Perchlorethylene. If equipment is not available, clean by

agitating in mineral spirits. If excessive contamination is present the filter must be

ultrasonically cleaned. If excessive carbon deposits are found, conduct the inspection and

cleaning of the power turbine support pressure oil nozzle in accordance with the Power

Turbine Support Pressure Oil Nozzle Cleaning.

(6) Dry the filter element by shaking (air dry) and inspect for any metal particles. If particles are

present, reclean or replace the air filter element.

(7) Thoroughly clean the filter cavity of all residual oil and sludge.

(8) Install the cleaned filter with new O-ring and fill the filter cavity with engine oil. Install filter cap;

Torque nuts to 30-40 lb in. (3.4-4.5 N.m).

76.

Engine Lube Oil Filter Housing Replacement. (Ref. FIG. 32)

A. Replace the lube oil filter housing as follows:

(1) Remove the eight nuts and washers. Remove the housing and the gasket.

(2) Replace the O-ring seals on the filter housing mating ends of the two transfer tubes.

(3) Replace the O-ring seals on both ends of the check valve assembly.

(4) Replace the filter housing gasket. Install the replacement lube oil filter housing. Mate the

housing to the two transfer tubes and to the check valve during the assembly.

(5) Retain the lube oil filter housing with eight nuts and washers. Torque nuts to 35-40 lb in.

(3.9-4.5 N.m).

77.

Engine Oil Pressure Regulating Valve Adjustment. (Ref. FIG. 32)

A. Make necessary changes in the engine oil pressure by adjusting the pressure regulating valve.

NOTE: During the initial check run of a newly installed engine the pressure regulating valve may

be adjusted to increase or decrease oil pressure as per specified limits. A direct reading

gage is to be utilized anytime an adjustment to the pressure regulating valve is required.

CAUTION: EXCEPT FOR INITIAL ADJUSTMENTS ON NEWLY INSTALLED ENGINES, DO NOT

ADJUST THE PRESSURE REGULATING VALVE TO CORRECT FOR HIGH OIL

PRESSURE. DO NOT MAKE A PRESSURE REGULATING VALVE ADJUSTMENT TO

CORRECT FOR A SUDDEN INCREASE OR RAPID CHANGE IN OIL PRESSURE.

THESE CONDITIONS ARE CAUSE TO SUSPECT OTHER OIL SYSTEM PROBLEMS

HAVE DEVELOPED.

(1) Remove the lockwire.

(2) Using a wrench turn the regulating valve clockwise to increase and counterclockwise to

decrease the oil pressure. An approximate adjustment may be made by bottoming the valve

and then backing it out 5-1/2 turns. One turn of the adjustment will change the oil pressure

approximately 13 psig (90 kPa). Oil pressure is 120 + 10 psig (827 + 69 kPa) at 107°C

(225°F) oil temperature.

78.

Turbine Pressure Oil System Check Valve Maintenance

A. Disassemble, clean and inspect the check valve as follows: (Ref. FIG. 34)

(1) Remove the fitting from the check valve housing.

(2) Separate the O-ring, spring, and poppet from the housing. Discard O-ring.

Page 135

(3) Wash parts in mineral spirits.

(4) Inspect valve parts in accordance with Table 12.

(5) Insert poppet and spring into valve housing.

(6) Install fitting with new O-ring on housing.

CAUTION: BE SURE THE CHECK VALVE IS INSTALLED WITH THE ARROW POINTING

TOWARD THE REAR OF THE ENGINE.

CAUTION: IF A NEW CHECK VALVE IS INSTALLED (BLACK IN COLOR) VERIFY THAT

THE PROPER NEW CLAMP IS INSTALLED. IF THE OLD CLAMP IS BEING

USED, THE CLAMP AND CHECK VALVE MUST BE REPLACED.

(7) Install check valve, ensure that the proper clamp is being used and that the clamp is

positioned on the downstream end of check valve upon the shouldered area.

(8) Inspect check valve for external leakage at first engine operation after valve installation on the

engine. No leakage permitted.

79.

Gas Producer Turbine Support Pressure Oil Tube Replacement

A. While removal of this tube is not recommended as a standard maintenance practice, removal may

be required from time to time to facilitate replacement of leaking seals or replacement of broken or

damaged tube assemblies.

(1) Remove and/or replace the gas producer oil tube assembly as follows:

(a) Disconnect and remove the No. 8 bearing scavenge oil tube assembly from the gearbox

and turbine.

(b) Remove safety wire from the gas producer pressure oil tube attaching hardware.

tee fitting.

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Dec 15/97

(d) Supply 30 psi (207 kPa) clean, dry shop air to the No. 8 bearing scavenge fitting on the

bottom of the gas producer support.

(e) Remove two bolts retaining the tube to the gas producer support. Carefully remove tube

from gas producer support. Discard packing.

(2)

Install the gas producer pressure oil tube assembly as follows:

NOTE: Air pressure to the gas producer support No. 8 scavenge fitting should be maintained

at 30 psi during reassembly. Always reinstall the pressure oil tube assembly with a

new crush seal.

(a) Supply 30 psi (207 kPa) clean, dry shop air to the No. 8 bearing scavenge fitting on the

bottom of the gas producer support.

(b) Install pressure oil tube with new packing in the gas producer support. Apply anti-seize

compound to the two retaining bolts; Torque to 35-40 lb in. (3.9-4.5 N.m) and secure with

lockwire.

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(d) Connect the pressure oil tube to the power turbine support pressure oil tee fitting. Torque

coupling nut to 80-120 lb in. (9.0-13.6 N.m).

(e) Connect the No. 8 bearing scavenge oil tube assembly to the gearbox and the turbine.

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

(f)

Check run the engine. (Refer to Engine Check Run.) Check for oil leaks in the area of

disassembly.

(g) Monitor engine chip indications for the next two flight hours.

80.

Gas Producer Turbine Support Pressure Oil Passage Flushing

Removal of the gas producer turbine support pressure oil tube is not recommended at this

maintenance level as it may leave carbon contaminants in the support passage. However, if the

No. 8 bearing cavity has been exposed and the tube must be removed, flush the support passage

as follows before reassembly.

(1) Remove lockwire and two screws retaining the gas producer pressure oil tube. Loosen

coupling nut. Loosen clamp at splitline. Remove tube from gas producer support. Discard

packing.

(2) Disassemble turbine as required. (Refer to applicable part of replacing the 1st-stage Turbine

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

(3) To keep the washing fluid from the rotor bearing area, turn the engine to a vertical position with

the compressor end on top.

(4) Place a bucket beneath the engine then flow mineral spirits through the support passage into

the bucket.

Table 12

Turbine Pressure Oil System Check Valve Inspection

Item

Condition

Serviceable Limit

Repair Limits Disposition

Stripped or crossed

None

Max. of one

Chase threads.

threads on fitting or

damaged

housing.

thread.

Nicks or scratches on

None

Repair or re-

flared tube sealing sur-

place part.

face of fitting or hous-

ing.

Page 138

Table 12

Turbine Pressure Oil System Check Valve Inspection - continued

Item

Condition

Serviceable Limit

Repair Limits Disposition

Nicks or scratches on

None

poppet seating surface

or housing valve seat.

Fretting wear in bore of

None

housing.

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(5) Install clamp and bracket on the gas producer support pressure oil tube. Do not tighten until

final clamp position is determined. Lubricate O-ring and install with pressure oil tube in the

gas producer support. Apply antiseize compound to the two retaining bolts; install bolts;

Torque to 35-40 lb in. (3.9-4.5 N.m) and secure with lockwire. Torque coupling nut to 80-120

lb in. (9-13.6 N.m). Position clamp and bracket as required and secure with splitline nut and

bolt. Torque nut to 20-30 lb in. (2.3-3.4 N.m). Torque clamp nut to 35-40 lb in. (3.9-4.5 N.m).

Disconnect fire shield-to-power turbine support pressure oil tube from the connector. Blow

through the installed pressure oil tube with clean compressed air to ensure that the tube is

clear. Remove screen from disconnected pressure oil tube. Flush screen in mineral spirits

and shake dry. Reinstall screen and tube at connector. Torque coupling nut at connector to

80-120 lb in. (9-13.6 N.m); Torque coupling nut at fireshield elbow to 200-250 lb in. (23-28

N.m).

(6) Reassemble turbine (refer to 1st-stage Turbine Nozzle or 1st-stage Turbine Nozzle Shield

Replacement).

81.

Power Turbine Support Scavenge Oil Strut Inspection and Cleaning

When carbon buildup is found during the scheduled inspection, clean (as required) the power

turbine support scavenge oil passage. Disassemble, inspect, clean, and reassemble the power

turbine oil system components as follows:

(1) Disassemble the oil passage components.

(a) Disconnect the scavenge oil line from the external sump.

(b) Remove lockwire and the two external sump attaching bolts. Remove the sump. Discard

the O-ring.

spacer. Rotate the spacer around the bolt to expose the scavenge oil passage in the

strut.

NOTE: On some configurations the spacer is an integral part of the support.

(d) Remove the pressure oil tube extending between the elbow at the firewall shield and the

power turbine pressure oil tube. Remove the screen.

(e) Loosen the gas producer pressure oil tube coupling at the power turbine pressure oil tube.

Do not remove the gas producer pressure oil tube.

CAUTION: IF THE GAS PRODUCER PRESSURE OIL TUBE IS REMOVED, THE

SUPPORT PASSAGE MUST BE FLUSHED. (REFER TO GAS PRODUCER

TURBINE SUPPORT PRESSURE OIL PASSAGE FLUSHING.)

(f)

Remove lockwire and two bolts then remove the power turbine pressure oil tube (nozzle).

(On some configurations the power turbine oil tube assembly is two pieces, a connector

and an oil tube.) Discard O-rings.

Page 139

NOTE: Removal of the pressure oil tube (nozzle) is not necessary unless the scavenge

oil passage requires cleaning.

CAUTION: MAKE CERTAIN THAT NO FOREIGN MATERIAL ENTERS THE EXPOSED

TUBES OR OPENINGS.

(2) Inspect the power turbine support scavenge oil passage using a light and mirror. The cross

section of the passage is approximately 1/2 x 5/32 inch (13 x 4 mm). If carbon deposits (coke)

are found, clean the passage; otherwise reassemble the oil passage components. (Ref. FIG.

35)

(3) Clean carbon deposits from the walls of the scavenge oil passage as follows:

(a) Use a soft wire with a hook bent at one end. Pull the carbon downward away from the

bearing area.

(b) Force shop air or engine oil (in a hand pump-type oil can) through the power turbine

support pressure oil strut to dislodge any loosened carbon.

petroleum solvent and dry.

Carbon Buildup in Power Turbine Support Scavenge Oil Strut and Rotating Labyrinth Seals

FIG. 35

Page 140

(4) Assemble the oil passage components as follows:

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(a) Lubricate a new O-ring and install it on the power turbine pressure oil tube. (On the

two-piece connector-tube configuration two O-rings are required.) Install the tube (or

tube and connector), secure with two bolts. Torque bolts to 35-40 lb in. (3.9-4.5 N.m)

and secure with lockwire.

(b) Attach the gas producer pressure oil tube to the power turbine pressure oil tube. Torque

coupling nut to 80-120 lb in. (9.0-13.6 N.m).

the power turbine pressure oil tube.

(d) On power turbine support configurations having a separable spacer at the scavenge oil

opening, remove the loosely installed bolt that was used to position the spacer during the

passage cleaning operation. Seat the spacer in the opening. Apply Permatex 1372

sealer lightly to the O-ring. Install O-ring at the power turbine support drain port. Install

the sump; retain with two bolts. Torque bolts to 40 lb in. (4.5 N.m) and secure with

lockwire. Apply torque in small equal increments.

(e) Connect the scavenge oil tube to the external sump. Torque coupling nut to 150-200 lb

in. (17-23 N.m).

82.

Power Turbine Support Pressure Oil Nozzle Cleaning

A. Clean the pressure oil nozzle as follows:

(1) Inspect and clean as required, the power turbine support scavenge oil strut. (Refer to

Inspection and Power Turbine Support Scavenge Oil Strut Cleaning.)

(2) Remove the oil lines at the connector (tee-fitting) for the power turbine pressure oil nozzle.

Remove the screen.

(3) Clean the screen using a suitable solvent.

(4) Remove the two bolts holding the tee-fitting and the pressure oil nozzle in place. Remove and

clean the fitting (Ref. FIG. 36). Using 6796920 puller, remove the pressure oil nozzle if it is

possible to do so without damaging the nozzle or the flange. If the nozzle cannot be removed

without causing damage, clean the nozzle while it is installed. Flush the nozzle often during

the cleaning using oil from a hand-squirt oil can or shop air.

(5) Clean and inspect the power turbine pressure oil nozzle as follows: (Ref. FIG. 37 and 38)

NOTE: Dash number details (-1), (-2), etc., refer to detail parts of 23003267 power turbine

support cleaning kit.

(a) Insert a No. 56 (0.047 in., 1.18 mm) drill (-4) into the pressure oil jet hole.

(b) Establish the alignment holes on a horizontal plane. (Ref. FIG. 39)

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Pressure Oil Tee Fitting Cleaning

FIG. 36

perpendicular is cause to scrap and replace the jet nozzle.

(d) Using a No. 52 (0.063 in., 1.61 mm) drill (-3), clean the upper 1.25 in. (32 mm) of the

power turbine pressure oil nozzle. (Ref. FIG. 37) Flush the nozzle and orifice several

times during the cleaning process.

(e) Using the 0.050 in. (1.27 mm) spiral (round) saw blade (-6), clean accumulated carbon

from the remainder of the nozzle. Use a twisting motion. (Ref. FIG. 37)

(f)

Ensure that the oil nozzle jet orifice is clean by inserting MS20995C41 stainless steel

safety wire, 0.041 in. (1.04 mm) diameter (-17) through from the top of the nozzle. (Ref.

FIG. 38) The safety wire contacts the end of the nozzle at 3.125 in. (79.4 mm) depth.

Using flat nose pliers, continue turning and pushing the wire into the nozzle until it is felt to

exit out the jet orifice. This penetration must be positively felt. Repeat as necessary.

83. Oil Flow Measurement

A. Measure the quantity of oil flow from the power turbine support scavenge oil passage or from the

external sump. If the external sump is removed, use a length of suitable hose to direct the

scavenge flow into a calibrated container. If the external sump is not removed, connect a hose to

the external sump scavenge fitting to direct oil flow.

Page 142

Power Turbine Pressure Oil Nozzle Inspection

FIG. 39

(1) To ensure consistency, make the measurement during the following conditions:

(a) Engine oil temperature no cooler than 10° C (50°F) and no hotter than normal operating

temperatures

(b) Use an external power source (not aircraft battery) to ensure a minimum N cranking

speed of 16%.

installed) are full of oil and that there is oil flow.

(2) Crank the engine with ignition disarmed for exactly 15 seconds. Collect and measure oil flow

during the 15 second cranking period and during coast down until the engine stops. It is not

necessary to collect and measure minor drips. At least 16% N speed must be achieved.

(3) A flow of less than 90 cc (3 oz) indicates a significant restriction of the oil nozzle and/or

passages. Clean the following areas of the lubrication system and conduct the flow check

once again.

(a) The power turbine support scavenge oil passage. (Refer to Power Turbine Support

Scavenge Oil Strut Inspection and Cleaning.)

(b) The power turbine support pressure oil nozzle, connector (tee- fitting) and screen. (Refer

to Power Turbine Support Pressure Oil Nozzle Cleaning.)

84.

Power Turbine Labyrinth Seals Cleaning

A. Clean carbon buildup from the power turbine labyrinth seals as follows: (Ref. FIG. 35)

(1) Remove the turbine from the engine. (Refer to applicable part of Turbine Assembly

Replacement.)

Page 145

(2) Mount the turbine on 6799955 fixture. Retain the fixture at the rear gas producer support

flange with two bolts. Position vertically with the turbine and exhaust collector support at the

top.

(3) Remove the 24 nuts and bolts from the splitline and carefully lift the turbine and exhaust

collector support, with power turbine rotor assembly, from the power turbine support.

NOTE: The two firewall shield retaining brackets and the oil tube clamp bracket are removed

when the exhaust collector is separated from the power turbine support.

CAUTION: DO NOT USE A CARBON REMOVER ON THE STATIONARY MEMBER OF THE

LABYRINTH SEALS. CARBON REMOVER WILL DAMAGE THE

NICKEL-GRAPHITE SURFACE.

(4) Carefully remove carbon and coke deposits from the rotating labyrinth seal knives.

(5) Before reassembly of the exhaust collector-power turbine rotor assembly to the turbine, press

the No. 6 bearing rollers outboard to create the maximum opening for passage of the bearing

inner race. It may be necessary to use grease to retain the rollers in this position.

(6) Reposition the turbine and exhaust collector support, with power turbine rotor assembly, onto

the power turbine support. Use care to prevent damage to the knife edges of the labyrinth

seals and/or to the No. 6 bearing inner race or rollers.

(7) Index the exhaust collector and power turbine supports as required. Apply antiseize

compound; then install the four slab head bolts at the line reamed holes marked at production

or overhaul during the alignment build. Rotate the power turbine rotor by hand to ensure that

there is no binding.

(8) Install the remaining 20 bolts and nuts, each lightly coated with antiseize compound. The six

long bolts go at positions 2, 6, 8, 9, 17 and 18 (looking forward with one at top center). The

two fireshield brackets go at position 8, 9 and 17, 18. The oil tube clamp brackets go at

position 2 and 6. Alternately Torque nuts 180 degrees apart to 10-15 lb in. (1.1-1.7 N.m);

then repeat the process torqueing the nuts of socket head bolts to 20-30 lb in. (2.3-3.4 N.m).

If Tee-head bolts are used, Torque to 35-40 lb in. (3.9-4.5 N.m) plus prevailing torque.

(9) Remove the turbine from 6799955 fixture. Install the turbine on the gearbox in accordance

with the installation procedure given in Turbine Assembly Replacement.

(10) Check run the engine after turbine installation. (Refer to Engine Check Run.)

85.

Ignition System Maintenance

WARNING: MAKE SURE THAT THE IGNITION SWITCH IS OFF BEFORE REMOVING THE SPARK

IGNITER OR SPARK IGNITER LEAD ASSEMBLY AS DANGEROUSLY HIGH

VOLTAGES MAY BE PRESENT. ALLOW FIVE MINUTES AFTER OPERATION FOR

ELECTRICAL DISSIPATION BEFORE DISASSEMBLY.

Maintenance of the ignition system includes: cleaning and inspecting the spark igniter, inspecting the

ignition exciter and spark igniter lead, and making an ignition check.

A. Spark Igniter Maintenance

(1) Remove, inspect, clean, and install the spark igniter as follows: (Ref. FIG. 40)

(a) Disconnect the ignition lead at the igniter. Hold the lead to prevent its twisting while

removing the nut. Separate the lead from the igniter by pulling straight out with no

rotational motion.

Page 146

(e) Inspect spark igniter for fretting wear. Wear of 0.032 in. (0.813 mm) max is serviceable

without corrective action. Wear of 0.032 in. (0.813 mm) or more is acceptable if it does

not affect the function of the spark igniter and if the following corrective action is taken:

Fabricate a shim from corrosion resistant steel shim stock to the dimensions given in

FIG. 42.

Spark Igniter Shim

FIG. 42

At installation of the spark igniter, place the fabricated shim between the outer

combustion case and the igniter.

NOTE: A shim sized per FIG. 42 will reduce the spark igniter installed thread length by

1/2 turn. Localized fretting is thereby moved 180° from the wear area of the

previous installation. Be sure to remove the shim when a new spark igniter is

installed.

(f)

Check the general condition of the spark igniter; replace if excessive erosion is evident.

(g) Check the operation of the spark igniter after it has been removed from the engine. Apply

28 volts dc to the exciter and observe the rate of firing. Normal operation is six sparks

per second minimum. Replace the spark igniter if it fails to fire or fires intermittently.

NOTE: Do not replace the spark igniter as defective until the ignition exciter is known to

be acceptable. (Refer to Ignition Exciter Replacement.)

(h) When replacing and/or reinstalling a serviceable spark igniter, apply a light coat of

antiseize compound (NS-165) to the threads. Install the spark igniter, Torque to 150-200

lb in. (17-23 N.m) and lockwire to fuel nozzle. Connect ignition lead; Torque to 70-90 lb

in. (7.9-10.2 N.m).

Ignition Exciter Maintenance

(1) Remove, inspect, and install the ignition exciter as follows: (Ref. FIG. 40)

Page 149

WARNING: MAKE SURE THAT THE IGNITION SWITCH IS OFF BEFORE REMOVING THE

SPARK IGNITER OR SPARK IGNITER LEAD ASSEMBLY AS DANGEROUSLY

HIGH VOLTAGES MAY BE PRESENT.

(a) Disconnect electrical leads and remove ignition exciter from the engine by removing three

nuts and washers.

(b) Connect a known satisfactory lead and spark igniter of the type used on the engine to the

ignition exciter.

CAUTION: DO NOT ENERGIZE IGNITION EXCITER IF SPARK IGNITER AND LEAD

ARE DISCONNECTED.

16 gage (12.95 mm). Observe firing. If a repetitive spark rate of less than 6 sparks per

second is observed, replace the ignition exciter.

CAUTION: DO NOT OPERATE THE LOW ENERGY EXCITER FOR MORE THAN FOUR

MINUTES IN ANY 30 MINUTE PERIOD. THE HIGH ENERGY IGNITION

EXCITER IS QUALIFIED FOR CONTINUOUS DUTY OPERATION.

HOWEVER, USE OF THE IGNITION SYSTEM ON A CONTINUOUS BASIS IS

NOT RECOMMENDED BECAUSE OF DEGRADATION OF THE SPARK

IGNITER.

(2) Apply 14 volts dc to the input of the ignition exciter if there is any question about its operation.

The spark rate should not be less than three sparks per second and should be uniform.

(3) Install serviceable exciter on the engine in reverse of the order of removal and connect

electrical leads. Torque attaching self-locking nuts to 30-40 lb in. (3.4-4.5 N^.m). Torque the

igniter lead coupling to 50-70 lb in. (5.6-7.9 N^.m). Torque input lead nut to 8-12 lb in.

(0.90-1.36 N^.m).

Spark Igniter Lead Maintenance

(1) Remove, inspect, and replace the spark igniter lead as follows: (Ref. FIG. 40)

(a) Inspect the outer part of the lead for braid damage; replace lead if damage is excessive.

(b) Remove the lead from the ignition exciter and the spark igniter; detach from retention

clamps at the power turbine governor and from the aft flange of the firewall shield.

(d) Reinstall cable in reverse order of removal. Torque igniter coupling to 70-90 lb in.

(7.9-10.2 N^.m); Torque exciter coupling to 50-70 lb in. (5.6-7.9 N^.m).

Ignition Check

(1) A procedure for checking the engine ignition is as follows:

WARNING: TO PREVENT ELECTRICAL SHOCK DURING INSTALLATION OF THE SPARK

IGNITER AND THE LEAD, ALLOW FIVE MINUTES FOR ELECTRICAL

DISSIPATION FOLLOWING IGNITION OPERATION OR TEST.

CAUTION: TURN THE LEAD NUT AND NOT THE SPARK IGNITER WHEN ASSEMBLING OR

DISASSEMBLING A LEAD AND AN IGNITER WHICH IS NOT INSTALLED ON THE

ENGINE.

(a) Remove the spark igniter lead from the spark igniter.

(b) Remove the spark igniter.

(d) Apply 28 volts dc across the ignition exciter. Observe or listen for spark.

(e) When replacing and/or reinstalling a serviceable spark igniter, apply a light coat of

antiseize compound (NS-165) to the threads. Install spark igniter and spark igniter lead

on the engine. Torque the spark igniter to 150-200 lb in. (17-23 N^.m) and lockwire to the

fuel nozzle. Torque the lead to 70-90 lb in. (7.9-10.2 N^.m).

Page 150

86. Temperature Measurement System

Temperature measurement system maintenance consists of inspection and replacement of the

thermocouple assembly.

A. Thermocouple Inspection. Make a visual and electrical check of the thermocouple assembly. (Ref.

FIG. 43)

(1) Visual. Visually inspect the thermocouple harness assembly for wear, broken leads or other

damage. Using a strong light and 10X magnification, inspect the thermocouple tips for cracks,

erosion, and scale. Replace thermocouple assembly for any of the following reasons:

(2) Excessive wear or damage to the leads.

(3) Tip breaks or cracks detected by magnification.

(4) Probes or tips which indicate melting or show other evidence of overtemperature.

NOTE: Turbines must be inspected for overtemperature damage anytime thermocouples are

rejected for melting or if they show other evidence of overtemperature.

(5) Tips which evidence erosion to the point that either wire has been reduced in area an

estimated 25% or more.

Page 151

Thermocouple Assembly

FIG. 43

CAUTION: DIRECT THE GRIT BLAST ON THE TIPS PERPENDICULAR TO THE PROBE

AXIS--NOT ON THE END OF THE PROBE WHERE THE INSULATION COULD

BE ERODED. AFTER THE SCALE IS REMOVED, REINSPECT THE TIP FOR

CRACKS USING A STRONG LIGHT AND 10X MAGNIFICATION.

(6) Tips having scale on either wire affecting 25% of the cross sectional area. If the thermocouple

is otherwise satisfactory, remove the scale by soft grit blast.

B. Thermocouple Electrical Check. The electrical check of the thermocouple assembly consists of a

continuity check and an insulation check.

NOTE: When performing any electrical check on an installed thermocouple harness assembly, at

least one harness lead must be disconnected from the fireshield junction block.

Disconnecting one lead isolates the thermocouple assembly from the airframe

temperature measurement system.

Page 152

CAUTION: A HOT ENGINE WILL CAUSE THE THERMOCOUPLES TO GENERATE A SMALL

POTENTIAL WHICH WILL PRODUCE ERRORS IN MEASURED INTERNAL

RESISTANCE VALUES. AN APPROXIMATE VALUE MAY BE OBTAINED BY

REVERSING THE LEADS AND AVERAGING THE READINGS.

(1) Continuity check. The internal resistance of an acceptable thermocouple harness assembly,

measured across the alumel and chromel leads, is 0.55 to 0.65 ohms at room temperature for

harness assemblies prior to p/n 23034926. For harness p/n 23034926, the acceptable internal

resistance is, 0.50 to 0.60 ohms at room temperature. An open circuit in the harness

assembly will cause this resistance to be high; a short circuit will cause it to be low.

NOTE: A check of these limits can be performed only by using test instruments that offer

usable sensitivity in this range (null-type resistance bridge or an especially designed

test instrument such as the Barfield Model 2312G). If such instrumentation is not

available, an ohmmeter (Simpson Meter or equivalent) can be used to detect an

open circuit.

CAUTION: ENGINE THERMOCOUPLES SHOULD NEVER BE IMMERSED OR SPRAYED

WITH CLEANING SOLVENTS. LIQUID CLEANING SOLVENTS WILL

PENETRATE THE POROUS MAGNESIUM OXIDE INSULATION. ENGINE HEAT

WILL VAPORIZE THE SOLVENTS LEAVING A RESIDUE CONTAINING CARBON

WHICH CAUSES A LOW RESISTANCE TO GROUND.

(2) Insulation check. The minimum acceptable resistance to ground is 2,000 ohms. Carbon

buildup on the probe tip will cause a short to ground. If resistance measures less than 2,000

ohms, clean carbon deposits from the probe using a clean soft cloth or by salt/grit blast.

Repeat the check after cleaning the tip.

(a) On installed thermocouple assemblies, connect a portable multimeter between either

harness lead and any probe flange.

(b) On uninstalled thermocouple assemblies, connect a portable multimeter between either

harness lead and each of the four probe flanges.

applying 650 ± 28°C (1200 ± 50°F) temperature to each thermocouple in succession

(JetCal and kit BH8001, or equivalent). The harness should indicate an upscale reading

on the millivolt meter and a gradual increase in resistance. If the resistance of each

probe increases above 2000 ohms during this hot check, the harness is acceptable. Low

resistance can be caused by carbon formation on the probe tip and/or magnesium oxide

insulation shorting the probe to ground. If the resistance of any probe decreases or

indicates a dead short, replace the thermocouple harness.

Thermocouple Replacement

(1) Replace the thermocouple assembly as follows:

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

(b) Remove the two thermocouple bracket mounting bolts and nuts; separate the bracket

from the turbine.

(d) Remove the thermocouple assembly starting at either end. Discard gaskets.

(e) Install replacement thermocouple with new gaskets in reverse of the order of removal.

Torque the eight junction mounting flange bolts to 30-40 lb in. (3.4-4.5 N^.m), the two

bracket bolts to 20-30 lb in. (2.3-3.4 N^.m) and the terminal nuts to 18-24 lb in. (2.0-2.7

N^.m).

(f)

Check run the engine after thermocouple replacement. (Refer to Check Run, para 256.)

87.

Firewall Shield Removal and Replacement

NOTE: The firewall shield assembly must be removed from the engine before the thermocouple

assembly can be taken off.

Page 153

Remove the firewall shield as follows:

(1)

Remove the gas producer fuel control assembly. (Refer to Gas Producer Fuel Control

Replacement.)

(2)

Remove the ignition lead from the spark igniter and from the firewall shield.

(3)

On applicable control system configurations, remove the fuel control system accumulator and

double check valve clamps from the firewall shield. (Ref. FIG. 10)

(4)

Remove the fuel line from the fuel nozzle. Detach the line from the firewall shield.

(5)

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

sump.

(6)

Remove the two attaching screws and remove the sump.

(7)

Remove the nuts and washers retaining the firewall shield to the gas producer support

scavenge oil fitting and to the pressure oil tube elbow.

(8)

Remove the firewall shield drain line.

(9)

Remove the two attaching bolts and washers; pull the firewall shield rearward to separate it

from the turbine and exhaust collector support.

(10) If the gas producer support scavenge oil fitting is cocked and/or shows evidence of oil leakage,

remove the fitting; then reinstall it as follows:

NOTE: If these conditions do not exist, it is not necessary to remove the scavenge oil fitting

during firewall shield replacement. (Omit step 10.)

CAUTION: KEEP THE PERMATEX OUT OF THE SCAVENGE OIL PASSAGE.

(a) Apply a coat of sealer (Permatex 1372 or equivalent) to the seal recess of the pad for the

scavenge fitting on the gas producer support.

(b) Install a new O-ring seal into the coated seal recess. Lightly overcoat the installed

O-ring with Permatex.

in. (3.9-4.5 N^.m). Use care while torqueing to prevent cocking the fitting.

Install the firewall shield as follows:

(1) Select the required bushing. The bushing plus the washer shall be sized to accommodate the

void and maintain a parallel relationship between the fitting and the horizontal firewall shield.

Install the bushing on the fitting.

(2) Install a washer on the scavenge oil fitting and on the pressure oil tube elbow; then install the

horizontal firewall shield. Retain the firewall shield at the scavenge oil fitting with a washer and

hex nut. Torque nut to 15-20 lb in. (1.7-2.3 N^.m). Retain at the pressure oil tube elbow with a

washer and nut. Torque nut to 55-80 lb in. (6.2-9.0 N^.m). Install the two firewall shield

retaining bolts. Torque bolts to 35-40 lb in. (3.9-4.5 N^.m).

(3) Apply sealer (Permatex 1372, or equivalent) lightly to the power turbine support scavenge oil

external sump O-ring. Install O-ring and sump. Retain sump with two bolts. Torque bolts to

35-45 lb in. (3.9-5.1 N^.m) alternately in small increments.

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(4) Install the gas producer fuel control.

(Refer to Gas Producer Fuel Control Replacement.)

Page 154

CAUTION: WHEN TIGHTENING THE GAS PRODUCER SCAVENGE OIL TUBE COUPLING

NUT ON THE SCAVENGE FITTING, BE SURE THAT THE OIL TUBE DOES NOT

CAUSE BINDING AT THE FITTING. ANY MISALIGNMENT OF THE TUBE THAT

WILL PLACE A COCKING LOAD ON THE FITTING COULD CAUSE OIL

LEAKAGE.

(5) Install the firewall shield drain line, the turbine pressure and scavenge oil lines, the fuel tube

and hose and on applicable control system configurations, the accumulator and double check

valve clamps. Torque fuel and pressure oil line coupling nuts to 80-120 lb in. (9.0-13.6 N^.m).

Torque scavenge oil tube coupling nuts to 150-200 lb in. (17-23 N^.m). Torque clamp bolts to

35-40 lb in. (3.9-4.5 N^.m).

(6) Attach the ignition lead to the firewall shield and to the spark igniter. Torque to 70-90 lb in.

(7.9-10.2 N^.m). Torque attaching bolts to 35-40 lb in. (3.9-4.5 N^.m).

88.

Anti-icing Air System

Anti-icing air system maintenance includes removal of the valve from the engine, inspection of the

valve, replacement of the poppet seat, and installation of the valve on the engine.

Anti-icing Air Valve Maintenance

(1)

Remove,the anti-icing air valve as follows: (Ref. FIG. 44)

(a) Disconnect the anti-icing air lines from the valve.

(b) Disconnect the linkage from the control arm.

(d) Disassemble the valve assembly.

(e) Remove the cotter pin, washer, and pin. Detach the actuating lever from the valve.

Discard cotter pin.

(f)

Remove the lockwire and unscrew the poppet guide assembly from the valve body.

Separate the poppet assembly from the body.

(2)

Clean the valve components in mineral spirits.

(3)

Inspect the anti-icing valve components in accordance with Table 13.

(4)

Assemble the valve assembly as follows:

(a) Insert the poppet into the valve body.

(b) Screw the poppet guide assembly into the body. Torque the coupling nut to 65-75 lb in.

(7.3-8.5 N^.m). Do not lockwire at this time.

the guide) and insert the pin. Secure the pin with a washer and cotter pin. Lockwire the

poppet guide to the valve body.

(5)

Install the valve as follows:

(a) Apply antiseize compound lightly to the threads then install the valve with new O-ring in

the scroll.

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

AIR FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(b) Reconnect linkage and air lines.

Page 155

Legend for FIG 44

1. Anti-ice tube LH

13. Not used

25. O-ring (2)

2. Anti-ice tube RH

14. Seat

26. Bleed valve

3. Anti-ice valve

15. Screw

27. Bleed valve

4. O-ring

16. Poppet assembly

28. Nut

5. Nut

17. Pin

29. Washer

6. Pin

18. Body

30. Bolt

7. Washer

19. Sensing tube

31. Nut (2)

8. Pin

20. Pressure probe elbow

32. Washer

9. Lever

21. Nut

33. Bolt (2)

10. Poppet guide

22. Elbow

34. Gasket

11. Poppet assy

23. Jet

35. Plug (2)

12. Pin

24. Nut

36. O-ring (2)

(d) Torque valve-to-scroll jam nut to 100-150 lb in. (11-17 N^.m) and secure with lockwire.

NOTE: For convenience of installation, the anti-icing valve may be rotated 360

degrees. Position valve as desired for the installation; then torque coupling nut

to 65-75 lb in. (7.3-8.5 N^.m) and secure with lockwire.

(6) Recheck the valve for leakage during first engine operation following installation of the repaired

valve. Replace valve assembly if leakage is still excessive.

Table 13

Anti-icing Air Valve Inspection and Repair

Serviceable

Repairable

Item Condition

Limit

Limits

Disposition

Lever wear at poppet

Max. flat length of (2.0

Repair by grinding

mating surface (creat-

mm)

rounded end in accor-

ing flat)

dance with FIG. 45 or

replace lever.

Wear at hole for air-

Remaining wall thick-

Repair or replace lever.

frame linkage

ness not less than

0.040 in. (1.02 mm)

Nicks or scratches in

None

Repair or replace valve

flared tube sealing sur-

body.

faces of valve body

Page 157

Anti-icing Valve Poppet Seat Replacement

FIG. 46

89.

Bleed Air System

Bleed air system maintenance includes cleaning, testing, and/or replacing the bleed control valve.

Bleed Air Control Valve Maintenance

(1) Test the bleed control valve on an installed engine. Clean the bleed valve if it does not operate

in the range given in Section I, FIG. 16. (Clean valve in accordance with Compressor Bleed

Valve Cleaning.) If cleaning does not bring the valve into the desired operating range, replace

the bleed control valve as follows: (Ref. FIG. 44)

(a) Disconnect the compressor discharge pressure sensing tube assembly by loosening the

coupling nut at the valve elbow.

(b) Remove the three bolts, nuts and washers. Separate the bleed control valve and gasket

from the mounting flange on the compressor case.

from the bleed valve. Discard O-ring.

(2) Assemble and install the bleed control valve as follows:

(a) Lubricate new O-ring and install it on the elbow (or elbow and jet). Install the elbow (or

elbow and jet) in the new bleed valve. Do not torque the jam nut at this time.

NOTE: The elbow and jet is used only in Holley bleed valves on 250-C18A and -C18C

engines. All other installations use elbow AN 833-4C.

(b) Apply antiseize compound to bolt threads then install the replacement bleed control valve

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

Assemble with washers beneath bolt heads. 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).

Page 159

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

AIR FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

valve with the coupling nut. Torque coupling nuts to 80-120 lb in. (9.0-13.6 N^.m). Torque

the elbow jam nut to 55-80 lb in. (6.2-9.0 N^.m).

90.

Compressor, Turbine Assemblies, Combustion Section and Power and Accessories Gearbox

Component Maintenance

WARNING: DO NOT BURN DISCARDED TEFLON SEALS. TOXIC GASSES ARE PRODUCED.

Component maintenance includes inspections, cleaning, replacement and repairs accomplished on

the components making up the compressor assembly, the turbine assembly, the combustion

section and the power and accessories gearbox.

Compressor

WARNING: CORROSION OR EROSION WILL CAUSE DAMAGE TO COMPRESSOR BLADES

AND VANES WHICH CAN RESULT IN ENGINE FAILURE.

(1) The cleaning and preservation practices which are necessary for the proper maintenance of

the compressor are described in the General Practices paragraphs. (Refer to Compressor,

Cleaning and Compressor Preservation.)

Diffuser Vent Orifice Inspection

(1) Inspect the diffuser vent orifice for evidence of spewing or for looseness. If spewing has been

encountered, resize the orifice. (Refer to Diffuser Vent Orifice Selection/Installation.)

Rear Diffuser O-ring Replacement

(1)

Replace the compressor rear diffuser-to-diffuser scroll O-ring as follows:

(a) Remove the pressure and scavenge oil lines between the compressor and the power and

accessories gearbox.

(b) For engines without a Pc filter, remove the Pc tube between the diffuser scroll and the

governor (tee). For engines with a Pc filter, remove the Pc scroll-to-Pc filter tube.

NOTE: Hold the Pc filter when removing tubes.

valve. Discard gasket.

(d) Remove the anti-ice lines between the anti-ice valve and the compressor front support.

(e) Remove the five bolts and one washer from the splitline and separate the compressor

from the gearbox. Discard O-rings. (Ref. FIG. 59)

NOTE: Keep track of the quantity and location of the compressor mounting shims. To

assure that compressor alignment remains unchanged, the same quantity of shims

must be reused at each mounting position when the compressor is reinstalled on the

gearbox.

(f)

Remove the turbine-to-compressor coupling.

(g) Cut the lockwire then remove the 12 screws from the aft side of the rear diffuser. (Ref.

FIG. 47)

(h) Separate the diffuser scroll from the compressor. Remove and discard the O-ring at the

rear diffuser OD. Lightly lubricate and install a new O-ring in its place.

(2)

Inspect the scroll as follows:

(a) Inspect the bronze sealing surface on the scroll at the diffuser mating surface. Replace

the diffuser scroll if the bronze is loose or breaking away.

Page 160

(3)

Assemble the scroll as follows:

(a) Apply antiseize compound lightly to the 12 attaching screws; then assemble the scroll to

the rear diffuser. Torque the 12 retaining screws to 20 lb in. (2.3 N^.m); then, one at a

time, loosen to about 10 lb in. (1.13 N^.m) and retorque to 16-17 lb in. (1.8-1.9 N^.m).

Secure with lockwire.

(b) Place new lightly lubricated O-rings on the rear diffuser and the spur adapter gearshaft.

Position the turbine-to-compressor coupling on the spur adapter gearshaft.

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

GEARBOX MATING GEAR BEFORE TORQUEING COMPRESSOR

RETAINING BOLTS.

foreign material which could cause misalignment. Place the compressor on the gearbox

with the required shims in place at the bolt pads. Attach the compressor with the five

bolts and one washer. Use 6799790 adapter (Q, FIG. 1) to turn the gear train until it

meshes with the spur adapter gearshaft. Torque bolts to 70-85 lb in. (7.9-9.6 N^.m) and

secure with lockwire.

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

FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE.

(d) Install the anti-ice lines between the anti-ice valve and the compressor front support.

(e) Apply antiseize compound to the bolt threads then install the bleed valve with new gasket

on the mounting flange. Retain with three bolts, nuts and washers. 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).

(f)

Attach the Pc line to the bleed valve and to the scroll. Torque coupling nuts to 80-120

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

NOTE: Hold the Pc filter while attaching tubes.

(g) For engines without a Pc filter, attach the Pc tube to the governor (tee) and to the scroll.

For engines with a Pc filter, attach the Pc tube to the Pc filter and to the scroll. Torque

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

(h) Install the pressure and scavenge oil lines between the compressor and the power and

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

Torque pressure oil coupling nuts to 65-100 lb in. (7.3-11.3 N^.m). Clamp tubes at

previous clamping locations.

Page 161

1. Diffuser Scroll

3. Compressor

2. O-ring

4. Screw (12)

Rear Diffuser O-ring Replacement

FIG. 47

91. Compressor Blades and Vanes Inspection

A. The design of the compressor case permits inspection of blades and vanes by removing the

compressor bleed control valve and one compressor half case. (Refer to Compressor Case

Replacement.) Remove the compressor and send it to an Rolls-Royce Authorized Maintenance

Center if vane rub marks are found on the hub area of the compressor rotor wheels during the

blade and vane inspection. Rework all nicks, dents, and corrosion pits by blending.

NOTE: Do not remove both case halves at the same time.

NOTE: Before reworking any blades, refer to the General Practices in Blade Damage, para B.

Compressor Rotor Blade Leading and Trailing Edge Blend Limits

FIG. 48

Compressor Blade Damage

(1)

Replace the compressor if any blade is cracked or broken off. Recommended corrective

actions for compressor blades are as follows:

NOTE: It is not possible to fully describe all of the damage conditions that could be incurred;

therefore, if damage is within the rework limits of Figure 48 and 49, but there is

reasonable doubt about the strength of the reworked blade as compared to a new

blade, replace the compressor assembly.

NOTE: For wheels with coated blades: Nicks, dents, etc. in the lower 25% of the airfoil

cannot be polished/blended without glass bead peening and reapplication of the

corrosion resistant coating. For these reasons the compressor rotor must be

removed and sent to an Rolls-Royce Authorized Maintenance Center.

(2)

General Practices. Blend and polish blades or vanes in a longitudinal direction only with the

rework forming a smooth blend with the basic airfoil. The number of blades or vanes which

may be reworked is not limited. The limiting factor of blade or vane rework is engine

performance. Any reduction of blade or vane area will decrease the efficiency of the

compressor and the performance of the engine. Remove as little material as possible. No

sharp edges, burrs, cracks or tears are acceptable.

(3)

Leading and Trailing Edge Damage (See Figure 48)

Blend and polish to remove damage. Replace compressor when the limits of Figure 48 are

exceeded.

(4)

Tip Damage (See Figure 49)

Blend and polish to remove tip damage. Replace compressor when the limits of Figure 49 are

exceeded.

(5)

Surface Damage (See Figure 50)

Blend and polish to remove surface damage. Replace the compressor when any of the limits

of Figure 50 are exceeded.

Page 163

(6)

Corrosion--Uncoated Blades. Blend and polish to remove all corrosion caused pits by

blending to limits defined for damage. Replace the compressor when:

NOTE: CORROSION OR EROSION WILL CAUSE DAMAGE TO THE COMPRESSOR

BLADES AND VANES WHICH CAN RESULT IN ENGINE FAILURE.

(a) Pitting in any area of the blade forms a definite line or

(b) Pit size or location exceeds blend limits.

(7)

Corrosion--Coated Blades.

(a) Two similar aluminide coatings are used on the compressor blades; H151S (Alloy Surface

Corporation) or A-12 (Chromalloy). Both consist of intermetallic diffused aluminide

coating and a conversion top coating. These coatings offer sacrificial protection against

corrosion.

(b) Due to the sacrificial properties of the diffused coating, reddish brown colored products

(superficial rust) may become visible on the airfoil surfaces if exposed to a corrosive

environment. These products are actually corrosion of the coating surface; not the base

blade material. This superficial rust may be removed by lightly brushing with a soft nylon

brush using hot 150°F (65°C) soapy water solution (non-alkaline neutral) followed by

water rinse. This procedure applies only to superficial rust indications not be confused

with corrosion pitting.

outer 75% of the blade. Blend and polish to the limits defined for damage. If corrosion

caused pits or any form of damage is detected in the inner 25% of the blade, send the

rotor assembly to an Rolls-Royce Authorized Maintenance Center.

(d) Replace the compressor assembly when:

Pitting in any area of the blade forms a definite line.

Pitting size or location exceeds blend limits.

Compressor Blade Erosion

(1) Replace the compressor assembly when more than 50% of the blades in any stage have a

chord width less than the limits shown in Figure 51.

Compressor Vane Damage

(1) Replace the compressor case if any vanes are cracked or broken off or show evidence of tip

rub on the rotor spacer. Refer to the General Practices in Blade Damage, para B, before

reworking any vanes. Inspection limits for the vanes are as follows:

CAUTION: THE COMPRESSOR CASES SHALL NOT BE IMMERSED IN LIQUIDS. THE

CASE MAY BE SET UP IN A VERTICAL POSITION AND SPRAYED WITH

MINERAL SPIRTS THEN IMMEDIATELY BLOWN DRY.

Page 164

Rolls-Royce Engine 250–C18, 250–C18A, 250–C18B, 250–C18C. Operation and Maintenance Manual (2003) - page 8