T63-A-720 Allison 250-C20C Aviation Unit & Intermediate Maintenance Manual TM 55-2840-241-23

Description

T63-A-720 Allison 250-C20C Aviation Unit & Intermediate Maintenance Manual TM 55-2840-241-23

This T63-A-720 Allison 250-C20C Aviation Unit & Intermediate Maintenance Manual TM 55-2840-241-23 is a detailed technical maintenance reference for the Army Model T63-A-720, identified in the manual as the Allison Gas Turbine Model 250-C20C turboshaft engine. It is written for Aviation Unit Maintenance (AVUM) and Aviation Intermediate Maintenance (AVIM) activities and covers maintenance functions on the complete engine, its components, and its systems in accordance with the Maintenance Allocation Chart. The manual combines engine description and operating principles with practical troubleshooting, servicing, disassembly, inspection, repair, assembly, testing, torque data, dimensional limits, and special inspection procedures.

File Details

• Manual type: Aviation Unit and Aviation Intermediate Maintenance Manual
• Engine model: T63-A-720
• Allison designation: Gas Turbine Model 250-C20C
• Technical manual number: TM 55-2840-241-23
• Part number: 6887191
• NSN: 2840-01-013-1339
• Original date: 2 November 1977
• Latest incorporated change shown: Change 25, 9 June 2009
• Language: English
• Page count: 273 PDF pages
• File format: PDF

Engine Systems and Maintenance Scope

The manual describes the T63-A-720 as a free-turbine engine with a multi-stage axial-centrifugal compressor, a single combustion chamber, a two-stage gas producer turbine, a free two-stage power turbine, and a power and accessory gearbox. Major systems addressed include fuel and control, lubrication, ignition, anti-icing air, temperature measurement, and compressor acceleration bleed air. The compressor description follows six axial stages and one centrifugal stage, while the turbine section explains how the gas producer turbine drives the compressor and accessory train and how the power turbine delivers output through the gearbox.

Maintenance information reaches well beyond basic servicing. The manual includes special tools and test equipment, preservation and depreservation, storage and shipping procedures, engine handling, component removal and installation, tube and fitting practices, fuel-system bleeding and pneumatic leak checks, fuel pump and filter work, gas producer fuel-control adjustments, power turbine governor servicing, fuel nozzle cleaning, lubrication-system servicing, magnetic chip detector inspection, oil-system work, ignition servicing, anti-icing and bleed-air maintenance, and miscellaneous accessory procedures.

Chapters Covered

• Chapter 1 – Introduction
  • Section I – General
  • Section II – Description
• Chapter 2 – Special Tools, Test Equipment, and Consumable Materials
  • Section I – Special Tools and Test Equipment
  • Section II – Consumable Materials
• Chapter 3 – Preparation for Service, Storage, and Engine Handling
  • Section I – Preparation for Service and Storage
  • Section II – Engine Handling
• Chapter 4 – Troubleshooting
• Chapter 5 – Accessories Servicing
  • Section I – General
  • Section II – Fuel System
  • Section III – Lubrication System
  • Section IV – Anti-Icing and Bleed Air Systems
  • Section V – Ignition System
  • Section IV – Miscellaneous Accessories
• Chapter 6 – Engine Disassembly
• Chapter 7 – Cleaning, Inspection and Repair
  • Section I – Cleaning
  • Section II – Inspection
  • Section III – Repair
• Chapter 8 – Assembly of Subassemblies
• Chapter 9 – Final Engine Assembly
• Chapter 10 – Final Engine Test
• Chapter 11 – Torques and Dimensional Limits
  • Section I – Torque Values
  • Section II – Dimensional Limits
• Chapter 12 – Special Inspections
  • Section I – Engine Hot End
  • Section II – Compressor
  • Section III – Abnormal Flight Maneuver Inspection
• Chapter 13 – Overhaul Interval and Retirement Schedule
• Appendix A – References
• Appendix B – Maintenance Allocation Chart
• Index

Taken as a whole, the chapter structure moves from understanding the T63-A-720 and preparing the correct tools through fault isolation, component servicing, controlled disassembly, condition assessment, authorized repairs, reassembly, and functional verification. The Maintenance Allocation Chart defines the maintenance functions assigned at AVUM, AVIM, and depot levels, helping the technician distinguish between work performed at the supported maintenance level and work requiring higher-level action.

Troubleshooting, Inspection, and Repair Detail

The troubleshooting chapter is arranged around trouble, probable cause, and remedy. It addresses starting and light-off problems, slow or hung acceleration, high or low starting temperature, unstable engine operation, oil pressure and oil temperature problems, excessive oil consumption, low power, abnormal turbine outlet temperature indications, N1 and N2 overspeed conditions, compressor stalls, fuel leakage, torquemeter indications, anti-icing faults, exhaust smoking, excessive vibration, afterfire, power loss, N2 droop, flameout, chip detector indications, and Health Indicator Test concerns. The manual also includes HIT baseline procedures and T63-A-720 compressor health-check procedures using compressor discharge pressure as a troubleshooting aid.

IMAGES PREVIEW

Chapter 7 gives cleaning, inspection, and repair criteria for engine areas and components, including compressor blades and vanes, the compressor case, combustion components, gearbox-related items, and repairable damage. It includes illustrated blend limits, combustion-liner inspection criteria, external seal information, painting and corrosion-related repair, and weld-repair procedures where authorized. Chapter 6 limits disassembly to the level needed for AVUM/AVIM cleaning, inspection, repair, and replacement, while Chapters 8 and 9 provide the corresponding subassembly and final engine assembly procedures.

Testing, Limits, and Service Data

Final engine testing can be performed with the engine installed in the airframe or on the specified mobile engine test stand. The test chapter monitors turbine outlet temperature, output shaft torque, oil pressure, gas producer N1 speed, and power turbine N2 speed, and includes operating limits, test requirements, a functional test schedule, vibration limits, and checks tied to repaired or replaced components. The manual’s leading particulars identify a dry engine weight of 158 pounds, design power output of 420 shp, ram power rating of 440 shp, and design speeds of 50,970 rpm for N1, 33,290 rpm for N2, and 6,016 rpm at the power output shaft.

Chapter 11 consolidates application-specific torque values for fasteners, fittings, tubing, and hose connections and provides dimensional limits for relationships such as clearances, plays, runouts, and stud setting heights. Chapter 12 addresses special inspections after overtemperature events, compressor concerns, and abnormal flight maneuvers. Chapter 13 provides established overhaul and retirement intervals for the engine and listed components, making the T63-A-720 maintenance manual useful both for immediate maintenance tasks and for longer-term component control.

Maintain and Diagnose the T63-A-720 with the Correct Procedures

The T63-A-720 Allison 250-C20C Aviation Unit & Intermediate Maintenance Manual TM 55-2840-241-23 supports the technician through fault diagnosis, accessory servicing, engine handling, authorized disassembly and repair, reassembly, inspection, adjustment, torque application, dimensional checks, and post-maintenance functional testing. Using the documented procedures, limits, inspection criteria, and test requirements matters when engine condition and component serviceability must be judged against defined maintenance standards rather than guesswork. Your purchase is delivered as an instant PDF download with no shipping required; open it on a compatible phone, tablet, laptop, or desktop device and print the pages you need for workshop reference.