Meeting Component Reliability Demands of the Aerospace Industry -Experiences and Recommendations

Gianluca AndreiHead of Gearbox System Engineering

Aarhus, October 6th, 2009

Oct. 6th, 2009 2© Avio SpA - 2009

One of Our Gearboxes vs. Typical Wind Turbine Gearbox

1.5 MWatt

Speed IncreaserAround 2 MWattAround 106 kNm Input TorqueAround 2000 mm Dimension

Speed ReducerAround 8 MWattAround 105 kNm Output TorqueAround 1000 mm Dimension

Oct. 6th, 2009 3© Avio SpA - 2009

Table of Contents

• Avio Overview and Gearbox Products

• Airworthiness and Reliability demands in Aeronautics and flow down in Avio Phase and Gate Process

• Gearbox Reliability Data and MaintenanceApproach

• Our Approach to achieve Reliability Targets:– Architecture, system, methodologies, technologies,

validation

Oct. 6th, 2009 4© Avio SpA - 2009

Our Business Activities

Complete propulsion systemsand services

MILITARY EJ200

Space propulsion & Launchers(solid & liquid)SPACE

Civil aeroengine MROCIVILMR&O

CIVIL Modules and Componentsfor civil aviation aeroengines& aeroderivative engines

GEnx

Maintenance Vega

Oct. 6th, 2009 5© Avio SpA - 2009

Turbofans:• PW2000, PW4000, CF6-80, GE90,

V2500, TRENT 900, SaM146, GEnx 1B/2B

• RB199, EJ200, F119, F124-GA-200, F110, DFZI100

Turboshafts:• T700, T700/CT7-8/T6E1

Jet Derivative Engines:• LM2500, LM6000

• Drive for electrical, hydraulic, fuel, oil, etc accessories for engineand aircraft utilities & Drive forengine starting

• Power Range: up to 1 MWatt

Our Aeroengine Accessory Drive Trains

Avio Designed Products have cumulated successfullymore than 150 million flight hours in revenue service

Oct. 6th, 2009 6© Avio SpA - 2009

Power Gearbox (PGB) for Turboprop and Turboshaft:• PW150, PT6-36B, TP400-D6• Power Range up to 8 MWatt

Our Power Gearboxes

Reduction Gearbox Demos for Geared Fan Aeroengine:

• Power Range up to 30 MWatt

Helicopter Main Gearbox:• Dauphin (SA 365/EC 155), Puma

(SA330), Super Frelon (SA321)• Power Range up to 1 MWatt

GearboxGearbox

Oct. 6th, 2009 7© Avio SpA - 2009

Latest Development - TP400 D6 Power GearboxMain Features:

• Around 8 MW

• 2 PGB versions (LH & RH)

• System Design based on tuned flexibility to achieve low weight and reliability

• 1st red. Stage: Bi-Helical Gears

• 2nd red. Stage: Planetary System

• Integral Bearing Races

• Isotropic Superfinished gears

Main Achievements:

• Output Torque Density around 200 Nm/kg

• More than 2000 hours development and certification tests

Oct. 6th, 2009 8© Avio SpA - 2009

• Civil Aviation World is governed by the Convention on International Civil Aviation (commonly known as the Chicago Convention)

• The International Civil Aviation Organization (ICAO), a specialized agency of the United Nations, sets the minimum Standards and Recommended Practices for international civil aviation

• Airworthiness Authority Agencies (EASA, FAA, …) were created:– to maintain a high level of safety and environmental protection in Civil Aviation

(primary mission)– to establish legislative and regulatory tasks– to issue Type Certificates for aeronautical products – to approve design, production and maintenance organizations (DOA, POA, MOA)

Civil Aviation World

Airworthiness is the termused to dictate whether anaircraft is worthy of safeflight

Oct. 6th, 2009 9© Avio SpA - 2009

ETOPS has set new standards for Aeroengine Reliability

Early ETOPS:

• provides ETOPS type design certification without any previous service experience

•The reliability plan must be defined and strictly followed throughout the NPI process

ETOPS:

• is an acronym for Extended-range Twin-engine Operation

• ETOPS allows a twin engine commercial passenger aircraft to be at any time a certain number of flying minutes away from a suitable diversion landing field

80s 90s 2000s

ET

OP

S di

vers

ion

time

(min

utes

)

75

150

225

300

Early ETOPS

ETOPS Diversion Time

In F

light

Shu

tDow

n R

ate

80s 90s 2000s70s

180 min. ETOPS IFSD rate < 0.02/1000 flight hour

Current Typical Turbofan IFSD rate < 0.005/1000 flight hours (i.e. anengine fails in flight once every > 60 years)

Improvement in Aeroengine Reliability by a factor > 10 in the the last 30 years

Oct. 6th, 2009 10© Avio SpA - 2009

Identify Product RequirementsIdentify Product Requirements

Customer Spec., Agency Specs

Translate to Technical Requirements& Flowdown to Components

Translate to Technical Requirements& Flowdown to Components

Design Specification, QFD, Risk Assessment -> Key Requirements Flowdown, Component Specifications, Validation Plans

Design Product, Assess AgainstTargets & Make Trades

Design Product, Assess AgainstTargets & Make Trades

FMEA, PFMEA, Lessons Learned, Design Practices, DFSS, Maintainability Analysis

Validate Customer & AirworthinessRequirements are satisfied

Validate Customer & AirworthinessRequirements are satisfied

Design Review, Substantiation, Testing and Manufacturing Capability

Monitor Field Performance to Assure Customer Requirements are satisfied

Monitor Field Performance to Assure Customer Requirements are satisfied

Observed Reliability, Weibull, IFSD, MTBUR

Problem Tracking

and Resolution

Problem Tracking

and Resolution

FRACAS (Failure Reporting, Analysis and Corrective

Action System)

NPI process: Phase and Gate Process to achieve Reliability

Achieve Type Design Certification and Production Readiness

Achieve Type Design Certification and Production Readiness

Continued AirworthinessContinued Airworthiness

Failure, Malfunction & Defect Mangement, Engineering Change, Service Bulletin

Oct. 6th, 2009 11© Avio SpA - 2009

Gearbox Reliability Data and Maintenance ApproachM

TB

UR

[per

Mill

ion

Flig

ht H

ours

]

Gearbox TOW [per Thousands Flight Hours]

0.5

1.0

1.5

2.0

10

Aeroengine Accessory Drive Train

Turboprop PGB

20 30

Gearbox Mean Time Between Unscheduled Removal (MTBUR) vs. Average Time On Wing (TOW)

(Typical)

Typical Maintenance approach: • On Condition• Condition Monitoring:

• Oil Content • Oil Debris Monitoring • Oil Filter Blockage• Oil Feed Pressure and

Temperature• Higher failure rate components are

allowed to be replaced On Wing (e.g. accessories, dynamic seals….)

• Line Replaceable Units (LRUs)

Corresponds to a single PGB UnscheduledRemoval every more than200 years (yearly usagerate about 2000 hours)

Corresponds to a single Gearbox UnscheduledRemoval every more than1000 years (yearly usage rate about 2000 hours)

Accessory Drive Train Reliability betterthan PGB for several reasons, e.g. lower

torque density, different usage spectrum,..

Oct. 6th, 2009 12© Avio SpA - 2009

Characteristics of Our Gearboxes

Technologies:

•Advanced Gears Technologies

•High Load Capacity bearings (rolling and journal bearings)

•Integral bearing races

•HUMS

Design Methodologies (System and Components):

•Whole System Modeling (CAD/CAE)

•System Dynamics

•Advanced Gears Design Methods

Architecture:

•Design based on Tuned Flexibility to achieve even Load / Torque share

•Design based on low parts count

Oct. 6th, 2009 13© Avio SpA - 2009

Architecture approach based on Tuned Flexibility

Even Split of Torque into two paths

Even Load Share and Control of Misalignments in Planetary Systems

Oct. 6th, 2009 14© Avio SpA - 2009

Planetary System Load Sharing Factor - DFSS analysis

• Developed proprietary methodologyto simulate planetary systems

– Simplified and fast methodology allowinganalysis of 106 cases in less than 10’

– Analysis of effects of architecture and boundary conditions on failure probability

– Analysis of effects of tolerances andmanufacturing errors on failure probability

Mean increase (%) of planet load as function of support stiffness

Each point: mean value from 50000random errors combination (tolerances and assembly)

Planet gear failure probability as function of support stiffness

Load cases

Material strengthPlanet Stress

Nominal planet stressMean planet stress

Oct. 6th, 2009 15© Avio SpA - 2009

Propshaft and relevant supports are designed to maintain allowedmisalignments on gears and bearings

Tuning of System Flexibility

Whole Gearbox Modelling

PGB System deflection - plot

(magnified)

Oct. 6th, 2009 16© Avio SpA - 2009

AVIO approach for transient torsional dynamic analysis allows non-linear simulation of the entire transmission system

This methodology:has been key to support the design of a high power Accessory Drive Trainhas allowed to simulate dynamic transients due to large generators torque fluctuations and failures

Fair match between analytical and experimental data was achieved

System Dynamics - Torsional Dynamic Modelling

Transient Torque

0

100

200

300

400

500

600

1,7 1,8 1,9 2 2,1

secN

m

Experimental

Analytical

Transmission model Test results vs analysis (torque vs. time)

Avio Verification Test Rig

Oct. 6th, 2009 17© Avio SpA - 2009

AVIO developed and validated a state of the art analysis code for real stress of gear teethAll gear types are designed with true surface topography, tooth stiffness, etc.Allowable stress limits became independent of gear typeContact Pattern Optimized by DFSS approach

Conventional "stress index" does not show anomalies in helical gears contact…

Wear Area

New "true stress" analysis tools detects the edge contact enabling successful design

…but wear is actually experienced in service.

True stress analysis for unified gears modeling / analysis

Oct. 6th, 2009 18© Avio SpA - 2009

1 MW Power Circulating Gear Test RigSingle Tooth Bending Fatigue for gear material bending characterizationTwin disk machines for surface damage modeling and characterizationClosed loop test rig for HUMS algorithms calibration (vibes)

Power Circulating Rig

Testing Capabilities to Develop Gear Allowables

• Main tests: – Bending, Surface Fatigue,

Adhesive Wear Tests: – High Hot Hardness Steels – Surface finish (e.g. as ground and

Isotropic Superfinished)

Oct. 6th, 2009 19© Avio SpA - 2009

Integral Races technology: > 2000hrs flawless performance in TP400-D6 PGB

1,0

Failu

rePr

obab

ility

[%]

Pyrowear 53-Avio FinishPyrowear 53-Ra<0,08µmPyrowear 53-Ra=0,15µm

Pyrowear 53-Avio FinishPyrowear 53-Ra<0,08µmPyrowear 53-Ra=0,15µm

Lifing design data

Case Hardened and IsotropicSuperfinished Races in Gear Steels

Fatigue Tests (e.g. spall propagation)

INTEGRALRACES

High Load Capacity Bearings – Integral Races

Oct. 6th, 2009 20© Avio SpA - 2009

Transmission Development and Certification Tests

Avio Lube System Simulator

Avio Power Rig

Gearshaft holography

Fatigue test

Components Verification

Subsystems Verification

Module Verification

Transmission Certification

Engine Certification

Component Strength

• Oil System Sensitivity• Gearbox efficiency

• Load Sharing Factor• System Dynamics• Effect of aero loads• Heat to oil• Durability

Transmission Type Test (150hrs)

• Integration with engine systems

• Initial MaintenanceInspection Test (IMI)

• Flight Test Bed

Component Dynamics

Oct. 6th, 2009 21© Avio SpA - 2009

Health Monitoring for Transmission systems

Vibration algorithmsAccelerometers

Oil Debris Monitoring System

Bearing diagnostics

Gear diagnostics

Bearing diagnostics

Gear diagnostics

time

Pitting

Failure

Spalling Failure

Weardetection

Warning time

Dam

age

Prog

ress

ion

time

Pitting

Failure

Spalling Failure

Weardetection

Warning time

Dam

age

Prog

ress

ion

Oct. 6th, 2009 22© Avio SpA - 2009

Product Reliability - Recommendations

• New Products have to be managed by a Phase and Gate Process

• Design For Reliability should be part of this Phase and Gate Process

• Key Enablers of the Process are:o Clear understanding of Product Requirements and their flow

down to subsystems/componentso Product background (Architectures, Design Criteria and Lesson

Learned, Technologies, Manufacturing Capabilities and Field Data)

o Design and validation methodologies

Oct. 6th, 2009 23© Avio SpA - 2009

Acronyms• Block Test or Type Test: 150 hours endurance

certification test

• CTQ: Critical to Quality, key characteristic

• DFSS : Design For Six Sigma

• DOA : Design Organization Approval

• EASA: European Aviation Safety Agency

• ETOPS: Extended Twin Engines Operations, used to indicate Civil Airworthiness Authority approval to allow a twin engine commercial passenger aircraft to be at any time a certain number of flying minutes away from a suitable landing field.

• FAA: Federal Aviation Administration

• FMEA: Failure Malfunction and Effect Analysis, carried out at system and component level since concept design

• FRACAS : Failure Reporting, Analysis and Corrective Action System is a mean to improve the product reliability during the development phase. To achieve this, FRACA is a closed-loop process that feeds back development experience into the product design. This process applies to development build, strip and test including flight test of engines, parts and accessories (including software) in support of the development of a product.

• HUMS: Health and Usage Monitoring System

• IFSD : In-Flight Shut Down

• IMI: Initial Maintenance Inspection test. This is a test that simulates the conditions in which the engine is expected to operate in service, including start stop cycles, to establish when the initial maintenance inspection is required. The test must be accomplished on an engine which substantially conforms to the type design.

• LH: Left Handed

• MOA : Maintenance Organization Approval

• MTBUR: Mean Time BeteweenUnscheduled Removal

• MRO: Maintenance, Repair and Overhaul

• NPI: New Product Introduction Process

• PGB: Power Gearbox

• PFMEA: Process Malfunction and Effect Analysis, carried out on manufacturing process to identify risks for component producibility.

• POA : Production Organization Approval

• QFD: Quality Function Deployment

• RH: Right Handed

• TOW: Time On Wing