PT6T36

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Pratt & Whitney Canada

R

C U S T O M E R T R A I N I N G

PT6T-3/6 TRAINING MANUAL

MARCH 2001

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PT6T-3/6 Series

TRAINING MANUAL

February 2001

Pratt & Whitney Canada Corp.

Printed in Canada

Student:

Instructor:

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION III

PRATT & WHITNEY CANADA

This manual is issued by the Pratt and Whitney Canada (P&WC) Customer Training Department, Longueuil, Quebec, Canada and should be used for TRAINING PURPOSES ONLY. The data contained herein does not replace or supersede the information contained in the appropriate airframe or engine maintenance manuals or other official publications.

For information concerning P&WC Customer Training, contact :

Tel : 1-450-468-7774, Fax : 1-450-468-7834, or Email : [email protected] For technical queries, contact the P&WC Help Desk (24 Hour Service) :

Tel :

USA & Canada ...1-800-268-8000

International...(IAC*)+8000-268-8000 Other ...1-450-647-8000

Fax...1-450-647-2888 * International Access Code

Visit the P&WC web site at: http://www.pwc.ca

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TABLE OF CONTENTS (cont'd)

CHAPTER 7 : Ignition System

Ignition ... 7.2

CHAPTER 8 : Performance

Performance check... 8.2 Engine condition trend monitoring ... 8.10 Operating limit ... 8.14 HSI & TBO interval ... 8.15 Rotor service life... 8.16

CHAPTER 9 : Fuel System

Schematic... 9.3 Fuel heater ... 9.4 Fuel pump ... 9.6 MFCU ... 9.8 Flow divider ... 9.14 Fuel nozzles ... 9.16 AFCU... 9.20 N2 governor... 9.24 TCU ... 9.28 FCU adjustments... 9.32 Troubleshooting chart... 9.36

CHAPTER 10 : Maintenance Practices

Periodic Inspections...10.2 Borescope Inspection ...10.4 First stage blade inspection ...10.6 Oil filter cleaning ...10.7 P3 filter cleaning ...10.8 Fuel pump and filter inspection...10.9 AGB Lip seal replacement ...10.10 Carbon seal replacement...10.12 Fuel nozzles Inspection ...10.13 Gas Generator case Inspection ...10.14 Special tools ...10.15 Activity report ...10.19

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SCOPE

This training manual contains information pertaining to the description, operation, maintenance and troubleshooting of the PT6T-3 /-3B /-3BE /-3BF /-3BG /-3D /-3DE /-3DF /-6 and -6B engines. This training manual is intended for classroom use only and includes cross section drawings, schematics and text.

A basic understanding of jet engine principles would be an asset. This manual may be used for Line Maintenance, Hot Section Maintenance or Heavy Maintenance training.

• Line Maintenance : Includes engine description, operation and "on-aircraft" maintenance.

• Hot Section Inspection : Includes removal, inspection, refurbishment of hot section parts as per Maintenance Manual procedures. Due to the commonality between PT6T and PT6B, hot section, the course is common for these two engine models.

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION VII

LINE MAINTENANCE

Course Schedule:

Courses duration : 5 days (30 hours) class time Breaks : 15 minutes at 10:00 and 14:00 Lunch period : 12:00 to 12:45

Course Objectives:

To teach the fundamentals and skills necessary to maintain the engine. At the end of the course, the student should be able to perform all Line Maintenance operations covered during the course.

Course Syllabus

Introduction:

Registration and orientation. Video presentation

Engine Overview:

Introduction to the engine. Main features Glossary of terms (abbreviations). Bearing locations. Stations and flanges. External views

Engine Construction:

Compressor inlet case. Compressor. Compressor bleed valve. Gas generator case. Combustion chamber liner. Compressor turbine vane ring. Turbine support case. Power turbine vane ring. Power turbine. Turbine cooling. Exhaust section. Reduction gearbox. Accessory Gearbox. Accessory Gearbox breather. Cold section trouble-shooting. Hot section troubletrouble-shooting. Compressor wash.

Lubrication System:

General. Power section oil system. Oil filter and by-pass valve. Oil pressure regulation. Scavenge system. Bearing compartment sealing. Reduction gearbox oil system. Oil system troubleshooting.

Indicating System:

General. Engine temperature. Trimming. Torque system. Chip detector. Indicating system Troubleshooting.

Ignition System:

General. Ignition exciter unit. High tension leads. Igniter plugs

Engine Performance:

HECTM description. Engine operating limits. Cycle life calculation.

Fuel System:

Description and features. Fuel system general. Fuel pump. Automatic/Manual Fuel control units. Flow divider. Fuel nozzles. Fuel system Troubleshooting.

Maintenance Practices:

During this phase every trainee will have the opportunity to perform maintenance, inspection and repair included in the engine Maintenance Manual. This portion of the course is done in the training centre shop on a production like engine.

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LINE MAINTENANCE (cont’d)

The Following is a List of Areas Covered :

Oil and fuel filters inspection. Oil pressure adjustment. Chip detector inspection. Lip seals and Carbon seals replacement. Removal and installation of external accessories. Fuel nozzles removal and inspection, Fuel control adjustments. Borescope inspection

Exams:

Four comprehensives multiple choice exams are administered during the course and the student must maintain an overall average of 70% on each exam to obtain a Line Maintenance certificate.

HOT SECTION INSPECTION

To teach the fundamentals and skills necessary to maintain the engine. At the end of the course, the student should be able to perform all Hot Section Inspection and maintenance operations covered during the course.

Course Syllabus

Practical Training:

During this phase every trainee will have the opportunity to perform Hot Section Inspection maintenance and repair included in the engine Maintenance Manuals. This portion of the course is done at different times in the training centre shop on a production like engine.

The Following is a List of Areas Covered:

Removal and installation of external accessories. Borescope inspection. Power section removal. Hot section inspection. Turbine tip clearance calculation. Sealing of hot section components. Grinding procedure.

Exam:

One comprehensive multiple choice exam is completed at the end of the course and the student must have at least 70% to obtain a Hot section inspection certificate.

This certificate and the line maintenance certificate are equivalent to the previously issued Heavy maintenance certificate.

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION IX

HEAVY MAINTENANCE

To teach the fundamentals and skills necessary to maintain the engine. At the end of the course, the student should be able to perform all heavy Maintenance operations covered during the course.

Course Syllabus

Introduction:

Registration and orientation. Video presentation

Engine Overview:

Introduction to the engine. Main features Glossary of terms (abbreviations). Bearing locations. Stations and flanges. External views

Engine Construction:

Compressor inlet case. Compressor. Compressor bleed valve. Gas generator case. Combustion chamber liner. Compressor turbine vane ring. Turbine support case. Power turbine vane ring. Power turbine. Turbine cooling. Exhaust section. Reduction gearbox. Accessory Gearbox. Accessory Gearbox breather. Cold section trouble-shooting. Hot section troubletrouble-shooting. Compressor wash.

Lubrication System:

General. Power section oil system. Oil filter and by-pass valve. Oil pressure regulation. Scavenge system. Bearing compartment sealing. Reduction gearbox oil system. Oil system troubleshooting.

Indicating System:

General. Engine temperature. Trimming. Torque system. Chip detector. Indicating system Troubleshooting.

Ignition System:

General. Ignition exciter unit. High tension leads. Igniter plugs.

Engine Performance:

HECTM description. Engine operating limits. Cycle life calculation.

Fuel System :

Description and features. Fuel system general. Fuel pump. Automatic/Manual Fuel control units. Flow divider. Fuel nozzles. Fuel system Troubleshooting.

Maintenance Practices:

During this phase every trainee will have the opportunity to perform the maintenance, inspection, repairs, and to perform Hot Section Inspection, included in the engine Maintenance Manuals. This portion of the course is done in the training centre shop on a production like engine.

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HEAVY MAINTENANCE (cont’d)

The Following is a List of Areas Covered:

Oil and fuel filters inspection. Oil pressure adjustment. Chip detector inspection. Lip seals and Carbon seals replacement. Removal and installation of external accessories. Fuel nozzles removal and inspection, Fuel control adjustments. Borescope inspection. Power section removal. Hot section inspection. Turbine tip clearance calculation. Sealing of hot section components. Grinding procedure.

Exams:

Four comprehensives multiple choice exams (15 questions each) are administered during the course and the student must maintain an overall average of 70% on each exam to obtain a Heavy Maintenance certificate.

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION XI

ABBREVIATIONS

AGB Accessory Gearbox

AFCU Automatic Fuel Control Unit

BS Built Specification

CW Clockwise

CCW Counter Clockwise

CSU Controlled Service Use

CT Compressor Turbine

EGT Exhaust Gas Temperature

FOD Foreign Object Damage

HSI Hot Section Inspection IGE In Ground Effect Hover

ITT InterTurbine Temperature (or T5) MFCU Manual Fuel Control Unit

N1 or Ng Compressor Rotor Speed

N2 or Nf Power Turbine Speed

Nr Main Rotor Speed

Ns Output Shaft Speed

OAT Outside Air Temperature OEI One Engine Inoperative

P2.5/2.8 Compressor Interstage Air Pressure

P3 Compressor Discharge Air Pressure

Pa Ambient Air Pressure

PAV Pressure Ajusting Valve

Note:

For Clarification, the following will be used in the manual N1 For gas generator speed

N2 For Power turbine speed ITT For Turbine temperature

Pb Fuel Pressure by-pass (returned to pump)

Pg Pneumatic Pressure to N2 Governor and

Torque Control Unit

Pm Fuel Pressure metered (to Fuel Nozzles)

PPH Pounds Per Hour

Pr Regulated Pneumatic Pressure

PRV Pressure Regulating Valve

Ps Fuel Pressure supply (Pump outlet)

Psi Pounds Per Square Inch

Psia Pounds Per Square Inch Absolute Psid Pounds Per Square Inch Differential

PT Power Turbine

P3/Px Pneumatic Pressure (AFCU)

Py Pneumatic Pressure (AFCU)

RGB Reduction Gearbox (CGB)

SB Service Bulletin

SFC Specific Fuel Consumption

SHP Shaft Horse Power

T1 Temperature at air inlet T5 Gas temperature at station 5

TBO Time Between Overhaul

TCU Torque Control Unit

Wa Air Mass Flow

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P&WC PUBLICATIONS :

Pratt and Whitney Canada publish various documents and manuals to support all the engines in service.

Illustrated Parts Catalogue (IPC) :

Contains all part numbers and parts history information along with identifying drawings for an engine series. To be used for ordering parts.

Maintenance Manual (MM) :

The manual defines all the line and heavy maintenance tasks that can be done on the engine as well as various tests and adjustments.

Service Bulletin (SB) :

Service bulletins are published to introduce new parts, modify existing parts to improve the product.

Spare Parts Bulletins (SPB) :

Spare parts bulletins are published to advise for new parts, fully interchangeable with existing parts.

Commercial Support Program Notification (CSPN) :

Program issued to assist operators in the accomplishment of SB’s.

Airworthiness Directive (AD) :

Issued by Governmental Aviation Regulatory Agencies. Requires compliance to rectify potential problems affecting the airworthiness of the aircraft. AD’s refer to

Special Instruction (SI) :

Special instructions are produced by Customer Support to provide specific maintenance information to specific customers.

Service Information Letter (SIL) :

Service information letters are produced by Customer Support to inform all operators on new techniques, new products and other general information.

Training Manual :

Training manual are published by the Customer Training Centre to assist the instructors in class.

Publication Price List :

The publication price list contains the prices of all P&WC publications and training material available to customers. For more information on Pratt & Whitney Canada publications contact :

Supervisor, Publications Customer Services (01CA4) 1000 Marie Victorin Longueuil, Quebec Canada J4G 1A1 Telephone : 1-450-647-2705 Fax : 1-450-647-2702 Email : [email protected]

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION XIII

PUBLICATION STANDARDS

General:

The engine manuals are published following the ATA 100 revision 15

Chapters:

In relation with the documentation used on an aircraft the chapter 71 is the POWERPLANT Chapter, and chapter 72 is the ENGINE Chapter.

The basic engine chapters are :

71 - 00 POWER PLANT (Ground Operating Limits, Ground Testing Procedures)

72 - 00 ENGINE (General, Tools, Consumable Materials, Periodic Inspections)

72 - 10 REDUCTION GEARBOX

72 - 30 GAS GENERATOR

72 - 50 POWER TURBINE AND EXHAUST

72 - 60 ACCESSORY GEARBOX

Component Parts:

Component parts are treated under engine section number as follows :

72 – 00 - 01 & … ENGINE EXTERNALS

72 – 10 - 01 & … RGB COMPONENTS

72 – 30 - 01 & … GAS GENERATOR COMPONENTS

72 – 50 - 01 & … POWER TURBINE AND EXHAUST COMPONENTS

72 – 60 - 01 & … AGB COMPONENTS

Example:

A basic Chapter will be identified as 72 - 00 - 04 Indicates engine chapter

Indicates engine general Indicates fuel nozzles

Pages:

The pages block number inside each chapter is used for breaking the subjects within the manual to small topics for ready reference and ease of use.

The standard page blocks are as follows : Description and Operation ...1 to 99 Fault isolation ...101 to 199 Maintenance Practices ...201 to 299 Servicing ...301 to 399 Removal/Installation ...401 to 499 Adjustment/Test...501 to 599 Inspection/Check ...601 to 699 Cleaning/Painting...701 to 799 Approved Repairs ...801 to 899 Example:

On page 72 - 00 - 04, page 201 you will find the Maintenance practice of the fuel nozzles.

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SERVICE BULLETIN COMPLIANCE CODES

Category 1 Do before the next flight.

Category 2 Do the first time the aircraft is at a line station or maintenance base that can do the procedure.

Category 3 Do before xxx hours or xxx cycles. This Category may be expanded as required, to specify a minimum and/or a maximum and/or repetitive interval/inspection.

Category 4 Do this SB the first time the engine or module is at a maintenance base that can do the procedures, regardless of the scheduled maintenance action or reason for engine removal.

Category 5 Do this SB when the engine is

disassembled and access is available to the necessary sub-assemblies. Do all spare part assemblies.

Category 6 Do this SB when the sub-assembly is disassembled and access is available to necessary part.

Category 7 Do this SB when the supply of superseded

parts is fully used.

Category 8 Do this SB if the operator thinks the change

is necessary because of what he knows of the parts history.

Category 9 Spare parts information only. Old and new

parts are directly interchangeable and operators can mix old and new parts.

Category CSU: Used to evaluate new parts before final

introduction in commercial service. Operators who participate should include this SB at the next maintenance or overhaul of the engine.

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION XV

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ENGINES COVERED IN THIS MANUAL

ENGINE MODEL CERTIFICATION

DATE TAKE-OFF RATING (SHP) INSTALLATION PT6T-3 1970 1800 BELL 212 AGUSTA BELL AB 212 SIKORSKY S-58T PT6T-3B PT6T-3BF 1979 1998 1800 BELL 212 BELL 412 & 412 SP

AGUSTA BELL AB 212 & 412 PT6T-3BE PT6T-3BG 1990 1998 1800 BELL 412 HP AGUSTA BELL AB 412 HP PT6T-3D PT6T-3DE 1993 1995 1800 BELL 412 HP & 412 EP

BELL CFUTTH CH-146 “Griffon” AGUSTA BELL AB 412 HP/EP

PT6T-3DF 1996 1800 BELL 412 EP

PT6T-6 1974 1875 AGUSTA BELL AB 212 & 412

SIKORSKY S-58T

PT6T-6B 1992 1875 AGUSTA BELL AB 412

T400-CP-400 1970 1800 USN, USAF, CF MILITARY

BELL AH-1J, UH-1N, CUH-1N

T400-CP-401 1972 1800 US ARMY MILITARY

BELL VH-1N

T400-WV-402 1975 1970 US NAVY MILITARY

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PT6T-3/6 TRAINING USE ONLY INTRODUCTION XVII

MAJOR ENGINE MODEL DIFFERENCES

The Twin-Pacengines covered in this manual can be divided in three major groups :

1- PT6T-3 /-3B /-3BE /-3BF /-3BG /-3D /-3DE /-3DF 2- PT6T-6 /-6B

3- T400-CP-400 /CP-401 /WV-402

Group 1:

PT6T-3 : Reference model

PT6T-3B : Similar to PT6T-3 with PT6T-6 hot section components for higher output during OEI operation.

PT6T-3BE : Similar to PT6T-3B except for a new torque control unit (deletion of torque sharing) and new of Nos. 16 and 17 bearing housing sleeve in RGB.

PT6T-3BF : Similar to PT6T-3B with increase in the 30 minute OEI rating.

PT6T-3BG : Similar to PT6T-3BE with increase in the 30 minute OEI rating.

PT6T-3D/-3DE : Similar to PT6T-3BE with improved hot section hardware, Duplex Fuel Nozzles & upgraded RGB.

Continuous OEI rating (-3D) 30 minutes OEI rating (-3DE).

PT6T-3DF : Similar to PT6T-3D, New Power Turbine components, 30 minutes OEI rating.

Refer to SB 5352 for details.

Group 2:

The T-6 engines differ from the T-3 engines by the EGT temperature measuring system in lieu of an ITT system. PT6T-6 : Up-rated version of PT6T-3 with hot section

improvements to accommodate higher power. PT6T-6B : Similar to PT6T-6 except for a new torque

control unit (deletion of torque sharing).

Group 3:

The T400 engine series listed below is for reference only, military engines not for commercial use.

T400-CP-400 : US Navy, US Air Force and Canadian Forces version of the PT6T-3 with reduction and accessory gearboxes made of aluminium Housing.

401 : US Army designation for the T400-CP-400 with features similar to the PT6T-3. T400-WV-402: US Navy designation for an up-rated

T400-CP-400 with hot section hardware improvements and Duplex Fuel Nozzles to accommodate higher power and the addition of a power turbine overspeed protection system.

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PT6T-3/-6 TRAINING USE ONLY

ENGINE OVERVIEW

1.1

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TWIN PAC INSTALLATION

The Twin-Pac® is installed in the commercial Bell Helicopter / Agusta-Bell 212 and 412 or in the Sikorsky S58 T The engine is secured in the aircraft by 4 engine mounts :

• 1 at the bottom of each accessory gearbox.

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ENGINE OVERVIEW 1.3

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ENGINE OVERVIEW 1.5

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PT6T-3 TURBOSHAFT

The Twin-Pac engine has 3 modules, 2 power section (PS) modules and 1 reduction gearbox (RGB) module.

References: SHP : ...1,800 shp Length : ...66 inches Width : ...44 inches Height : ...33 inches Dry Weight : ...690 lbs 100% N1 speed ...38,100 rpm 100% N2 speed ...33,000 rpm 100% Output shaft (Ns) ...6,600 rpm Main Components and Features

Accessory gearbox (AGB)

• Support the engine accessories.

• Driven by the compressor rotor.

Compressor

• 3 axial stages plus 1 centrifugal impeller.

• Supply the necessary air pressure and flow, for combustion and cooling of hot section components.

Combustion Chamber

• Annular, Reverse flow (for shorter and lighter engine).

• Area for the combustion of the air-fuel mixture.

Compressor Turbine

•

Power Turbine

• Single stage turbine, turns counterclockwise (CCW).

• Independently of compressor turbine (free turbine).

• Extract the energy to supply necessary power to the aircraft main transmission.

Reduction Gearbox (RGB)

• Two stage reduction gearbox with idler gear.

• Built in torque measurement system.

• Reduce the power turbine speed to a speed satisfactory for the aircraft main transmission.

• Supply the power for two oil cooler blowers.

• Supply the power for two power turbine (N2) governors.

Fuel and Control System

• Separate and identical hydro-pneumatic fuel control systems for each power section.

· Two fuel heater · Two fuel pump

· Two automatic fuel control unit (AFCU) · Two manual fuel control unit (MFCU) · Two N2 governor

· One common torque control unit (TCU)

• Two operating modes · Automatic (normal flight)

· Manual (Emergency, Troubleshooting)

• Governing function

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ENGINE OVERVIEW 1.7

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BEARINGS

Function:

Holds major rotating assemblies.

Ball Bearings

Absorb axial and radial loads.

Roller Bearings

Absorb radial load only Permit thermal expansion

Description:

The Twin-Pac has a total of 33 main bearings, which does not include accessory gearbox bearings.

Power-Section Bearings

Bearings Nos. 1 to 4 are installed in each power section:

• No 1 Ball Front compressor

• No 2 Roller Rear compressor

• No 3 Roller Front power turbine shaft

• No 4 Ball Rear power turbine shaft

Gearbox Bearings

Bearings Nos. 5 to 17 inclusively are installed in the reduction gearbox.

• No 5 Ball duplex Front input drive shaft

• No 6 Roller Rear input drive shaft

• No 7 Roller Front idler gear

• No 8 Ball duplex Rear idler gear

• No 10 Ball Torquemeter piston

• No 10.5 Roller Rear clutch gearshaft / housing

• No 11 Ball Rear clutch gear / 2nd stage gearshaft

• No 12 Ball Front clutch gear / 2nd stage gearshaft

• No 12.5 Roller Front clutch gearshaft / housing

• No 13 Roller Center 2nd stage gearshaft

• No 14 Roller Front 2nd stage gearshaft

• No 15 Roller Rear output shaft

• No 16 Roller Front output shaft

• No 17 Ball Front output shaft

Bearings 1 to 8 are lubricated by the power-section oil

system.

Bearings 10 to 17 are lubricated by the reduction

gearbox oil system.

Maintenance :

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ENGINE OVERVIEW 1.9

BEARINGS

1

4

5

8

10

11

12

14

17

2

3

6

101 2

13

15

16

7

121 2

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MAJOR ASSEMBLIES AND FLANGES

POWER SECTION MODULE

EXHAUST DUCT

POWER TURBINE

REDUCTION

GEARBOX

MODULE

NO. 3 & NO. 4 BEARING

SUPPORT HOUSING

POWER TURBINE

STATOR HOUSING

A

B

C

A

D

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ENGINE OVERVIEW 1.11

MAJOR ASSEMBLIES AND FLANGES

INLET SCREEN

COMPRESSOR TURBINE

SHROUD HOUSING

COMPRESSOR

TURBINE VANE RING

GAS GENERATOR CASE

COMPRESSOR

ACCESSORY

GEARBOX

INLET

CASE

G

F

E

C

F

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BASIC TURBOSHAFT OPERATION

The PT6T (Twin-Pac) engine series is a lightweight free

turbine engine. It drives one output shaft via a two-stage

reduction gearbox. The power section consists of two major assemblies :

• The Compressor rotor assembly

• The Power Turbine rotor assembly.

The Compressor Rotor assembly has a compressor and a compressor turbine. The Power Turbine rotor assembly has a power turbine and a power turbine shaft. The two assemblies are not connected together. They turn at different speeds and in opposite directions. This design is referred to as a "Free Turbine Engine". It permits the power turbine and the rotor to turn at a constant speed, while the fuel control system schedules any compressor speed (N1) as necessary.

Starter cranking torque is low, since only the compressor rotor rotates on start. Engaging the accessory gearbox mounted starter/generator starts the Power Section. The compressor pulls air in the engine via an annular plenum chamber (inlet case). The pressure increases across 3 axial stages and one centrifugal impeller. The air is directed into the combustion chamber.

Air enters the combustion chamber via small holes and at the proper compressor speed, the fuel is sprayed in the combustion chamber by 14 fuel nozzles. Two spark igniters located in the combustion chamber ignite the

air-The generated hot gases are then directed to the turbine area.

At this point, ignition is turned off since a continuous flame exists in the combustion chamber.

The hot expanding gases accelerate through the compressor turbine vane ring and cause the compressor turbine to rotate. The gases leaving the compressor turbine are accelerated again as they flow through the power turbine vane ring. The power turbine provides rotational energy to drive the main rotor via the reduction geartrain. Gases leaving the power turbine are expelled into the atmosphere by the exhaust duct.

The reduction gearbox reduces the power turbine speed to a suitable speed for the aircraft geartrain (6,600 rpm). The engine oil supply is contained in three integral oil tanks, which provide oil to lubricate and cool all bearings and gears.

A hydro-pneumatic fuel control system installed on the Accessory Gearbox regulates fuel flow to the fuel nozzles in response to power requirements and flight conditions. The fuel system controls the main rotor speed by varying the engine's output power as a function of the load demand set by the pilot.

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ENGINE OVERVIEW 1.13

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STATIONS (GRAPH)

0 300 600 900 1200 ₁₂₀ 90 60 30 0 C PSIA STATIONS ₇ ₆ ₅ ₄ ₃ _2.5 ₂ ₁ P T 2.8 P T

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ENGINE OVERVIEW 1.15

LEFT FRONT VIEW

TACHOMETER GENERATOR PAD (N1)

FUEL SYSTEM INLET PORT

FUEL FILTER

REDUCTION GEARBOX OUTPUT SHAFT

T5 SYSTEM TERMINAL BLOCK

FUEL ACCUMULATOR

OIL FILLER CAP

POWER SECTION OIL PRESSURE PORT

POWER SECTION OIL

TEMPERATURE PORT

POWER SECTION OIL TANK DRAIN

ACCESSORY GEARBOX

CHIP DETECTOR

NO.2 BEARING OIL

SCAVENGE PUMP

POWER SECTION

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RIGHT FRONT VIEW

REDUCTION GEARBOX OIL PRESSURE PORT

Py ACCUMULATOR

OIL TO FUEL HEATER

STARTER GENERATOR PAD

FUEL CONTROL UNIT (AFCU + MFCU)

P.S. OIL PRESSURE

SENSING LINE

P.S. OIL PRESSURE REGULATING VALVE

OIL PRESSURE LINE

Pg LINE

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ENGINE OVERVIEW 1.17

RIGHT REAR VIEW

CHECK VALVE

P3 AIR CABIN BLEED

P.S.OIL PRESSURE

ADJUSTMENT VALVE

COMPRESSOR WASH

RING FITTING

AGB OIL BREATHER

CARBON SEAL

AIR INLET

SCREEN

FUEL NOZZLES

SPARK IGNITER

P.S. OIL OUTLET

(TO AIRFRAME OIL COOLER)

T5 TRIM COMPENSATOR

P.S. OIL INLET

(FROM AIRFRAME OIL COOLER)

N2 GOVERNOR

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BACK VIEW

RGB BREATHER PORT

TORQUE CONTROL UNIT

BLOWER

DRIVE

COVER

TORQUEMETER OIL

PRESSURE OUTLET

(TO TRANSDUCER)

RGB STATIC AIR PRESSURE PORT

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ENGINE OVERVIEW 1.19

LEFT SIDE VIEW

METERING TEE ORIFICE

P3 LINE TO R.G.B.

CARBON SEAL

OIL PRESSURE LINE

DRAIN VALVE

FLOW DIVIDER VALVE

P3 AIR FILTER

COMPRESSOR

BLEED VALVE

P3 LINE TO AFCU

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COLD SECTION

2.1

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COLD SECTION

Function:

Supply the necessary mass of air at the right pressure to the combustion chamber and all the supporting systems. Transmit the rotational energy from the compressor turbine to drive the accessories mounted on the accessory gearbox.

Topics Covered in this Chapter:

• Inlet case

• Compressor assembly

• Bleed valve

• Gas generator case

• Cold section cleaning

Operation:

The compressor draws air into the engine and compresses it, before delivery to the combustion chamber area.

Compressed Air:

• Sustains combustion in order to produce the energy necessary to drive the compressor and the power turbines.

• Provides cooling air for hot section components.

• Provides air to seal bearing cavities.

• Assists in the operation of the fuel control unit.

• Controls bleed valve operation.

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COLD SECTION 2.3

COLD SECTION

GAS GENERATOR

COMPRESSOR

BLEED VALVE

INLET CASE

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COMPRESSOR AND INLET CASE

Function:

Inlet Case

• Directs air into the compressor

• Supports No. 1 bearing

Compressor

• Provides the combustion chamber with the correct airflow at the required pressure.

References:

Compression ratio : ...7.3 : 1 Maximum airflow (Wa) :...6.60 lbs/sec Maximum N1 speed : (PT6T-3) : ...100% (38,100 rpm) (PT6T-3B’s/-6’s) : ...103.4% (39,400 rpm) (PT6T-3D’s) : ...109.2% (41,600 rpm) Construction: Inlet case

• One piece aluminum casting protected against corrosion.

• Anti-ice protection by heat from oil tank.

• Inlet screen (1/4 inch mesh) prevents objects from entering the compressor.

Compressor

• Three stages of axial rotors consisting of bladed disks, separated by stator vanes (1st stage Titanium blades, 2nd and 3rd stages, stainless-steel blades).

• One stage centrifugal consisting of a centrifugal impeller (Titanium).

• All the rotating components are held in place with tie rods that extend through the four stages.

• The No 1 bearing flexible housing absorbs compressor rotor vibrations.

• The compressor discs and the impeller are limited in cycles (refer to chapter Performance).

Maintenance:

Scheduled

• Check compressor inlet area for corrosion, dirt deposits and erosion and check first-stage blades and vanes every 300 hours or 1 year and whenever condition of inlet screen warrants its removal.

• Inspect inlet screen cleanliness and condition of mesh and rubber sealing rims for damage every 150 hours.

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COLD SECTION 2.5

COMPRESSOR AND INLET SECTION

INTERSTAGE AIR (P2.8)

IMPELLER HOUSING

IMPELLER

COMPRESSOR

STUB SHAFT

TIE ROD

COMPRESSOR AIR INLET CASE

NO.1 BEARING

FLEXIBLE HOUSING

AIR INLET SCREEN

INTERSTAGE AIR (P2.5)

(46)

Centrifugal Axial

COMPRESSOR BLEED VALVE

Function:

Prevent compressor stalls and surge below 91% N1, due

to different efficiencies between the axial compressor and the centrifugal compressor.

Description:

A piston sliding on a guide pin inside the housing controls the amount of interstage pressure (P2.5/P2.8) bled off from the compressor. A rolling diaphragm mounted on the valve piston prevents leakage between P2.5/P2.8 and the piston chamber.

Operation:

Two forces act on the bleed valve piston :

• Modified P3 air pressure, inside the bleed valve, pushes to close the bleed valve.

• P2.5/P2.8 pressure, from the interstage compressor area, pushes to open it.

P3 air flows through the valve and across 2 orifices (primary and secondary). The valve closing point is achieved during engine acceleration when the pressure acting on the piston (modified P3) is sufficient to overcome the compressor interstage pressure (P2.5/P2.8).

As the compressor speed increases, modified P3 increases higher than P2.5/P2.8, thus increasing the pressure acting on the piston and gradually closes it. The N1 speed at which the valve closes is a function of the

A larger secondary orifice requires more N1 speed (more P3 pressure) to make the valve close.

Maintenance:

Unscheduled

• Perform Bleed valve closing point check.

• Check for evidence of air losses at sealing faces and mating surface.

• Replace diaphragm if leaking.

• Clean orifices.

• Check for bleed valve sticking or seat/piston damage.

Note:

• Refer to SB 5394 for bleed valve assembly / des-assembly.

• P2.8 bleed for PT6T-3D’s and post SB 5351 Power Sections Compressor Efficiencies Wa Bleed Valve closed Bleed Valve opened

(47)

COLD SECTION 2.7

COMPRESSOR BLEED VALVE

CLOSED POSITION

Pa

GUIDE PIN

P3

PISTON

COVER

P2.5/P2.8

GAS GENERATOR CASE

SECONDARY

ORIFICE

PRIMARY

ORIFICE

GUIDE

TUBE

SLEEVE

DISCHARGE TO

ATMOSPHERE

DISCHARGE TO

ATMOSPHERE

OPEN POSITION

P3

Pa

ROLLING

DIAPHRAGM

(48)

BLEED VALVE CLOSING POINT

Purpose:

Verify that the bleed valve closes within an acceptable N1 range.

Operation:

• Install the bracket assembly as per maintenance manual instructions

• Start engine and accelerate slowly while watching air bubbles forming in the water container.

• As N1 speed increases more bubbles will appear.

• Keep accelerating until the bubbles stop.

• Record N1 speed where bubbles stop.

• Repeat the procedure to confirm closing point.

• Plot closing point of bleed valve on graph. Closing point must be within the gas generator speed band for the indicated outside air temperature (OAT).

Adjustment: (Post SB 5380)

The compressor bleed valve contains different sized orifices, which control the closing point on individual engines. If the closing point is not within the specified limits, replacement of the secondary orifice is permitted. If closing point speed is above the limit, install an orifice of a smaller size (smaller dash number).

If closing point speed is below the limit, install an orifice of a bigger size (higher dash number).

A one size change will shift the valve closing point by approximately 1% N1.

Orifices P/N : ST 3268-xxx (range from –067 to –090) Baseline orifice : ST 3268-073

Note:

The bleed valve closing point limits apply to all bleed valve configurations.

(49)

COLD SECTION 2.9

BLEED VALVE CLOSING POINT CHECK

BLEED VALVE

A

BRACKET

ASSEMBLY

DETAIL "A"

80 -40 0 +40 C 82 84 86 88 90 92 94 96 98 N1 %

OUTSIDE AIR TEMPERATURE (OAT) AREA " B " REJECT PERFORMANCE LOSSES COMPRESSOR STALL AREA " B " REJECT BAND " A " A CCEP TABL E

(50)

GAS GENERATOR CASE

Purpose:

Houses and supports various engine components. The diffuser pipes change the high velocity pressure into static pressure and cause the compressor air to turn 90°.

Construction:

• Welded assembly of steel alloy machine parts and sheet metal with an aluminide corrosion resistant coating.

• 21 brazed diffuser pipes. The case provides :

• Support for the compressor stator parts

• Support for the No. 2 bearing

• 14 bosses for fuel nozzles

• 2 bosses for igniter plugs

• 2 bosses for drain valves

• 1 boss for P3 air (to Automatic Fuel Control Unit)

• 1 boss for P3 air (to clutch gear carbon seals)

• 1 boss for P3 air (airframe bleed)

• 1 boss for the ITT harness

Two drain valves are provided on the gas generator case to drain fuel from the combustion chamber in the event of a false start or following power section shutdown.

Maintenance:

Scheduled

• Verify drain valve for security and leaks at each engine periodic inspection.

• Inspect gas generator case for cracks (around fuel nozzles, ports and spot welds), distortion, corrosion and evidence of overheating every 150 hours or 6 months.

• For Pre-SB 5239 only (PT6T-3/3B), Longitudinal seam welds inspection every 600 hours (no inspection if post SB and all helical weld configuration).

Unscheduled

• Cleaning and touch-up of protective coating.

• Repair of fuel nozzle pad threads using "Keensert" inserts.

• During HSI, visually inspect case and diffuser pipes for wear and cracks.

(51)

COLD SECTION 2.11

GAS GENERATOR CASE

DRAIN VALVE

P3 PRESSURE TUBE TO

AUTOMATIC FUEL

CONTROL UNIT

NO.2 BEARING

PRESSURE

OIL TUBE

_{DIFFUSER PIPE}

STRAIGHTENING VANE

NO.2 BEARING

SCAVENGE

OIL TUBE

NO.2 BEARING

PRESSURE OIL TUBE

FLANGE "F"

P3 BLEED PORT

TO CABIN HEATER

IGNITER PORT

P3 PRESSURE TO RGB

CLUTCH GEAR CARBON

SEALS

FLANGE "C"

P3 PRESSURE

TO BLEED VALVE

DRAIN VALVE PORT

COMPRESSOR

BLEED VALVE PORT

IGNITER PORT

(52)

COMPRESSOR WASH

Function:

Restore the compressor efficiency by removing salt and dirt deposits from the compressor gas path.

Type of Washes:

• Desalination wash

• Performance recovery wash

Desalination Wash (Rinse):

This method of washing consists of motoring the engine with the starter while injecting water into the compressor via the wash ring to remove salt deposits. The wash is done with normal drinking water.

Performance Recovery Wash:

This method of washing consists of motoring the engine with the starter while injecting a cleaning solution into the compressor via the wash ring. Approved cleaning agents are used to remove dirt deposits, which cannot be removed using water only.

A 15-30 minute period is allowed for the cleaning agent to soak in, followed by one or two rinse cycles (water). A drying run should follow the compressor wash.

Wash Frequency:

It is recommended that compressor washes be carried out depending on the operating environment.

• Desalination wash should be performed daily if operating frequently in salt laden environment or weekly if operating occasionally in salt laden environment.

• Performance recovery wash should be performed every 50 hours, weekly or as required depending on the operating environment.

When the temperature is below 2°C (36°F), methanol must be added to the water to prevent freezing.

Note:

Prior to washing, make sure that :

• Engine had a minimum of 40 minutes cooling period. • Aircraft bleed air system is “OFF”.

• Flow divider/dump valve line is disconnected. • Ignition is turned “OFF” (circuit braker).

• P3 filter is removed on PRE SB 5309 engines.

• RGB P3 filter is removed (post SB 5174/5320), P3 line disconnected at elbow fitting or cap removed on Tee fitting (post SB 5423).

• Fuel Boost Pump and Fuel valve "ON".

Refer to the maintenance manual 72-00-00 page block 700 for compressor wash procedure.

Caution:

Do not motor engine for more than 30 seconds. Observe starter-cooling period (ref. Aircraft Maintenance Manual)

(53)

COLD SECTION 2.13

COMPRESSOR WASH

CLEANING

SOLUTION

WATER

PRESSURE

GAUGE

REGULATED

AIR PRESSURE

SHUTOFF

VALVE

SPRAY

_RING

(54)

COLD SECTION TROUBLESHOOTING

PROBABLE CAUSE SYMPTOMS AT CONSTANT POWER ACTION REQUIRED

N1 ITT

Restricted inlet screen ⇑ ⇑ Clean and/or remove obstruction

Dirty compressor ⇑ ⇑ Perform compressor wash /revise schedule

Damaged compressor blades ⇑ ⇑ Return to an authorized overhaul facility if

damage is beyond limit

P3 leaks ⇒ ⇑ ⇑ Check for external leaks on gas generator.

At HSI verify sealing surfaces. Excessive loading of starter

generator or other AGB mounted accessories.

⇓ ⇑ Replace faulty accessories.

Bleed valve stuck open ⇑ ⇑

Ensure P3 is not leaking between bleed valve and gas generator case. Inspect, repair, replace bleed valve.

Bleed valve closing point out of limit

Loss of power (Closing too late) or

compressor stalls (Closing too early)

Remove and clean valve orifices or change orifice to get proper closing point.

Bleed valve stuck closed Compressor stalls Remove and clean valve orifices or change orifice to get proper closing point.

Hooting/Rumbling noise Bleed valve flutters Check/replace bleed valve

Humming sound Compressor rotor out of balance If humming disappears above 60% N1, no further action. If present above 60% N1 borescope inspection of compressor and compressor turbine for damage.

Note:

(55)

HOT SECTION

3.1

(56)

HOT SECTION

Purpose:

Extract energy from the hot expanding gases to :

• Drive the compressor turbine

• Drive the power turbine and the reduction gearbox

Topics Covered in this Chapter:

• Combustion chamber

• Compressor turbine vane ring

• Compressor turbine

• Power turbine vane ring

• Power turbine

• Exhaust duct

• Sealing of the hot section

• Compressor turbine wash

Operation:

The hot section of the engine comprises of components down stream of the gas generator. Hot expanding gases leaving the combustion chamber are directed towards the compressor turbine vane ring and hit the compressor turbine blades. The energy extracted by the compressor turbine will drive the compressor and the Accessory Gearbox.

Thereafter, gases travel across the power turbine vane ring and hit the power turbine blades. The power turbine rotation is transmitted to the output shaft via the power turbine shaft and the reduction gearbox.

Gases leaving the power turbine are expelled to the atmosphere through the exhaust duct.

(57)

HOT SECTION 3.3

HOT SECTION COMPONENTS

(58)

COMBUSTION CHAMBER LINER

Purpose:

Provide an area for combustion of the fuel/air mixture. The reverse flow feature provides for a shorter and lighter engine.

Construction:

• Annular, reverse flow type combustion chamber made of nickel alloy sheet metal

• 14 fuel nozzle adapter bosses

• 2 spark igniter bosses

• Cooling rings maintain a layer of cooling air to protect the combustion chamber walls from the flame

• On PT6T-3D’s power section, the small exit duct is an integral part of the liner and it is covered with ceramic coating as thermal barrier.

Operation:

P3 air enters the combustion chamber through holes in the inner and outer liner walls. The shape, size and location of these holes provide the correct fuel/air ratio for all operating conditions.

The combustion chamber combined with the large and small exit ducts form an envelope that turns the gas 180° (reverse flow). This configuration permits location of the turbines closer to the compressor and within the combustion chamber area, thus making the engine shorter and lighter.

Cooling rings direct P3 air into the combustion chamber, close to the walls, to form a flame barrier.

Maintenance:

Unscheduled

• Borescope inspection through fuel nozzle bosses.

During Hot Section Inspection:

• Inspect Liner for evidence of burning, cracking, buckling, etc.

• Regap cooling rings if they are distorted.

• Some damage is acceptable.

Note:

Local damage to the combustion chamber is most likely related to fuel nozzle spray pattern problem.

(59)

PT6T-3/3B's/6's

IGNITER BOSS

FUEL NOZZLE PORT

WITH SUPPORT BRACKET

FUEL NOZZLE PORT

WITH SUPPORT BRACKET

PT6T-3D's

HOT SECTION 3.5

(60)

SMALL AND LARGE EXIT DUCTS

Purpose:

Change direction of the airflow 180° (reverse flow).

Construction:

The small exit duct (except PT6T-3D’s) and large exit duct are made of two layer of heat resistant nickel alloy, air cooled by P3 air, and coated with aluminide coating. On PT6T-3D’s the large exit duct is partially coated with a ceramic compound to act as thermal barrier.

Operation:

Hot expanding gases are re-directed towards the compressor turbine vane ring.

P3 air for cooling flows between the double skin configuration and cools the two ducts. Via the small exit duct P3 air is routed to the compressor turbine vane ring for internal cooling of each vane.

Maintenance:

• Inspect the small and large exit ducts for evidence of burning, cracking or coating loss.

• On the small exit duct only stop drill cracks up to 1 inch long (1/16” drill size).

(61)

COMBUSTION CHAMBER LINER

SMALL EXIT DUCT

(EXCEPT PT6T-3D's)

CERAMIC COATING

(PT6T-3D's ONLY)

LARGE EXIT DUCT

HOT SECTION 3.7

(62)

COMPRESSOR TURBINE VANE RING

(AND ASSOCIATED PARTS)

Vane Ring:

• Direct the gases toward the compressor turbine at optimum angle and speed

• Convergent vanes change the static pressure into velocity

• Cobalt or nickel alloy casting, coated using a diffused aluminide process. Air-cooled core passages allow P3 air to flow through each vane.

• Exit area is classed.

Shroud Housing:

• Support the shroud segments and interstage sealing ring.

• Slots in the shroud housing match with corresponding lugs on the vane ring prevent any side play.

Small Exit Duct:

• Pinched the compressor turbine vane ring on the shroud housing.

• Machined face contact shroud housing and turbine vane ring to prevent P3 air leakage.

Interstage Sealing Ring(s):

•

Shroud Segments:

• Make close tolerance compressor turbine blades tip clearance, to reduce hot gases leakage.

• Machined from nickel alloy steel, thickness is classed to fit different compressor turbine wheel diameters.

Baffle (All Except PT6T-3):

• Create an area to insulate the turbine vane ring and No.2 Bearing area.

No. 2 Bearing Cover (PT6T-3) or Cover Flange (All other):

• Locate the compressor turbine vane ring, shroud housing and small exit duct assemblies with the center line of the power section.

• The inner lugs of the vane ring match with the slots on the cover (T-3) or cover flange (all others).

Lock Plate:

• Secure compressor turbine vane ring and No.2 bearing cover or cover flange to the gas generator case.

(63)

HOT SECTION 3.9

COMPRESSOR TURBINE VANE RING (T-3)

INTERSTAGE

SEALING RING

PRESSURE

SIDE

SHROUD

SEGMENT

RETAINING

RING

COMPRESSOR

TURBINE SHROUD

HOUSING

TIP

CLEARANCE

COMPRESSOR

TURBINE

VANE RING

COMPRESSOR

TURBINE

NO. 2 BEARING

COVER

LOCK PLATE

P3 COOLING

PASSAGE

LARGE

EXIT DUCT

SMALL EXIT

DUCT

P3

(64)

COMPRESSOR TURBINE VANE RING (cont'd)

Operation:

The compressor turbine vane ring receives hot gases from the combustion chamber. The converging vane airfoils direct the air towards the turbine blades, accelerating and changing its direction simultaneously. The vane ring is pinched between the small exit duct and the shroud housing. Lugs on the vane ring fit into slots on the shroud housing to prevent rotational movement. The vane ring class determines the total area of all the openings between the vanes trailing edges. A smaller vane ring class (smaller area) accelerates the air more and therefore increases the compressor turbine speed (N1). A higher N1 speed provides more air to the engine, more cooling and a lower ITT.

The compressor turbine vane ring is subject to extreme temperatures within the engine. Cooling of the vane ring will thus determine its life expectancy. P3 air traveling inside the vane airfoils keeps them at a temperature lower than the gases flowing on the outside. After cooling, air is ejected in the gas path.

Segments come in different classes (thickness) to fit different compressor turbine diameters and maintain the necessary clearance between the compressor turbine blades and the segments.

Effect of Vane Ring Class Change:

Increase area : N1 ⇓ ITT ⇑ Decrease area : N1 ⇑ ITT ⇓

Note:

Replacement vane ring must have a class number identical to the original vane ring (tolerance ±0.03).

Maintenance:

During Hot Section Inspection

• Inspect vane ring for : evidence of burning, cracking and coating loss.

• Insure proper sliding fit (lugs to slots) with mating parts.

• Check flatness of all mating flanges to reduce P3 air leakage to the minimum

(65)

HOT SECTION 3.11

COMPRESSOR TURBINE VANE RING

(T-3B’S/6’S)

INTERSTAGE

SEALING RING

COMPRESSOR

TURBINE SHROUD

HOUSING

TIP

CLEARANCE

COMPRESSOR

TURBINE

VANE RING

COMPRESSOR

TURBINE

NO. 2 BEARING

COVER

LOCK PLATE

NO. 2 BEARING

COVER FLANGE

P3 COOLING

PASSAGE

LARGE

EXIT DUCT

SMALL EXIT

DUCT

PRESSURE

SIDE

SHROUD

SEGMENT

RETAINING

RING

P3

(66)

COMPRESSOR TURBINE VANE RING

PT6T-3D’S (AND ASSOCIATED PARTS)

Vane Ring:

Similar to the PT6T-3B configuration except :

• Nickel alloy casting.

• Air-cooled core passages allow P3 air to flow through each vanes and exit at the trailing edge of the vanes for increased efficiency.

• Lugs on outer diameter used to maintain segments in place.

Baffle:

• Close tolerance baffle to create an area to insulate the turbine vane ring and No.2 Bearing area.

(67)

HOT SECTION 3.13

COMPRESSOR TURBINE VANE RING (T-3D)

COMBUSTION CHAMBER LINER

LARGE EXIT DUCT

COMPRESSOR

TURBINE

VANE RING

SEALING RING

SHROUD SEGMENT

SHROUD HOUSING

TIP CLEARANCE

COMPRESSOR TURBINE BLADE

AIR BAFFLE

NO.2 BEARING COVER

LOCK PLATE

CERAMIC

COATING

PRESSURE SIDE

P3

EXIT DUCT

SUPPORT

FLANGE

CLEARANCE

(68)

COMPRESSOR TURBINE

Purpose:

Extract energy (66%) from the hot gases to drive the compressor rotor unit.

Construction:

The compressor turbine is a two-plane balanced disk assembly, the disk is made of nickel alloy steel with firtree serrations that provide a firm attachment as well as allowing for thermal expansion differences between the blades and the disk. Rivets are used to axially retain the 58 blades on the disk. A master spline ensures reinstallation of the compressor turbine in its initial position on the compressor stub shaft during maintenance. References: Maximum N1 speed : (PT6T-3) : ...100% (38,100 rpm) (PT6T-3B’s/-6’s) : ...103.4% (39,400 rpm) (PT6T-3D’s) : ...109.2% (41,600 rpm) Rotation ... CW viewed looking forward

Operation:

Expanding gases, accelerated through the vane ring hit the turbine blades. The energy available in the gases is converted into rotational movement to drive the compressor and the engine accessories. Nearly two thirds of all the energy available from the products of combustion is needed to drive the compressor. The one third remaining is used to drive the power turbine.

The turbine is individually balanced on two planes with weights and rivets. This feature allows for turbine replacement in the field.

The turbine disc is limited in cycles (refer to chapter Performance).

Maintenance:

• Inspect turbine disk for cracks, overheating, and scratches.

(69)

HOT SECTION 3.15

COMPRESSOR TURBINE

CUP WASHER MASTER SPLINE RETAINING BOLT COMPRESSOR

TURBINE BALANCING WEIGHT & RIVETS

RIVET

DETAIL

PIN

BLADE

(70)

COMPRESSOR TURBINE BLADES

Purpose:

Extract energy from the hot gases

Construction:

The compressor turbine blades are made from a nickel alloy, using a Directionally Solidified casting process known as D.S. blades or Single Crystal on PT6T-3D’s. DS Blades features include triple taper design construction, firtree retention, growth check pad (PT6T-3B’s) and diffused corrosion resistant protective coating Single Crystal blades have firtree retention, new airfoil design, no growth check pads. The blades are serialized for life tracking purpose.

The sulphidation attack can described in four levels :

Stage 1 Mild sulphidation : Evident slight roughness of

surface and breakdown of the coating layer. Condition acceptable in the field.

Stage 2 Medium sulphidation : Heavy roughness of the

surface, Base material is attacked, Blade integrity still not affected. Condition acceptable in the field.

Stage 3 Severe sulphidation : Heavy roughness of the

surface, Built-up of blister, Base material is attacked, Blade integrity is affected. Condition NOT acceptable in

Stage 4 Deep penetration with metal separation. Blade

fracture imminent. Unbalance of rotor assembly. Operation is unsafe.

If sulphidation of the C.T blades is experienced a boroscope inspection should be scheduled to monitor the sulphidation stage. A regular Turbine wash should be established to reduce sulphidation progress.

Special sulphidation resistance coatings are available as customer option.

Maintenance:

Unscheduled

• Wash turbine blades based on past sulphidation experience.

• Borescope inspection through fuel nozzle bosses.

• Inspect turbine blades for sulphidation, cracks, erosion, tip rub, burning, coating loss, impact damage and blade shift.

C.T Blades Retirement Life:

PT6T-3 : ...one TBO period PT6T-3B’s/-6’s : ...“On Condition” PT6T-3D’s : ...8000 hours

(71)

HOT SECTION 3.17

CT BLADES SULPHIDATION

CT BLADE SULPHIDATION

CT BLADES

STAGE 1

EQUIAXED ALLOYS STAGE 2

STAGE 4 STAGE 3

DS ALLOYS

(72)

POWER TURBINE VANE RING

Purpose:

Direct gases to the power turbine and change static pressure into velocity.

Construction:

• Nickel alloy casting with a riveted sheet metal center baffle.

• The exit area (throat) of the vane ring is classified.

• Supported by the power turbine housing.

• A lug to slot arrangements centers and prevents movements of the vane ring.

Operation:

Gases leaving the compressor turbine are accelerated through the power turbine vane ring and cause the power turbine to rotate.

The vane ring is held in place by lugs fitted in the power turbine housing. The riveted inner baffle directs air close to the power and compressor turbine disks for cooling. During engine assembly, selection of the correct vane ring class (area) will allow for optimization (matching) of the N1 and ITT parameters and engine performance.

Effect of Vane Ring Class Change:

Increase area : N1 ⇑ ITT ⇓ Decrease area : N1 ⇓ ITT ⇑

Note:

Replacement vane ring must have a class number identical to the original vane ring (tolerance ±0.1).

Maintenance:

• Inspect vane ring for evidence of burning, cracking and coating loss.

• Insure proper fit (lugs to slots) with mating parts.

(73)

HOT SECTION 3.19

POWER TURBINE VANE RING

(74)

POWER TURBINE

Purpose:

Extract energy (33%) from the gases to drive the aircraft main rotor through the reduction gearbox.

Construction:

The power turbine is a single-plane balanced disk assembly, the disk is made of nickel alloy steel and is splined to the power turbine shaft. A master spline insures that the turbine can only fit in one position on the turbine shaft. The 41 blades are retained in the firtree serrations with rivets. There is no mechanical links between the power and compressor turbines thus the power turbine is "Free" to turn independent of the compressor turbine operation.

Removal of the power turbine is permissible at field level if an operator wants to inspect the area beneath the turbine (ie : No. 3 bearing cover pre SB 5222).

Balancing of the power turbine must be done with the power turbine shaft and the No. 3 and 4 bearings altogether and for that reason the power turbine is not field replaceable.

References:

N2 at 100% ... 33,000 rpm

Rotation ... CCW viewed looking forward NR at 100% ... 324 rpm

The turbine disc is limited in cycles (refer to chapter Performance).

Maintenance:

Unscheduled

During Hot Section Inspection :

• Inspect the turbine disk for cracks, overheating, scratches.

• Inspect the turbine blades for : cracks, burning, coating loss, corrosion, impact damage and blade shift.

(75)

POWER TURBINE

MASTER SPLINE

HOT SECTION 3.21

(76)

SECONDARY AIR SYSTEM

General:

The secondary air system consists of all the pressure air that is not used directly to produce power.

Three Sources of Air Are Used in the Secondary Air System:

• P2.5 interstage air pressure

• P2.8 interstage (shroud bleed) air pressure

• P3 compressor delivery pressure Of all the air entering the power section :

Primary Air System (85%) (Power Production):

- 25% is used in the combustion process. - 60% is used to cool the combustion gasses.

Secondary Air System (15%):

- 8% is used for :

• Turbine disks cooling and CT vane.

• Sealing of bearing compartments. - 2% is used for :

• Operation of bleed valve.

• Operation of Automatic Fuel Control Unit.

• Sealing of Reduction Gearbox carbon seals. - 5% is used for :

• Cabin bleed (heating).

Hot Section Cooling

General:

Internal passages in the engine guide P3 air for cooling of various hot section components like, combustion chamber, vane ring and turbine disks.

A port (at 12 o’clock position) on the gas generator case delivers P3 air pressure for airframe use (heater etc. ).

Operation:

P3 air is taken from the gas generator section and guided with various baffles to provide cooling and prolong hot section components life. Once the air has been used for cooling, it is evacuated in the gas path.

Air flowing into bearing compartments is evacuated via the oil scavenge system (described in oil system chapter).

Maintenance:

Unscheduled

• Ensure no leak exists on airframe air bleed system.

• Ensure that cooling rings in the combustion chamber are in satisfactory condition.