Causes and Impacts of Engineering Changes

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Lean Aerospace Initiative

Product Development & Supplier Relations

Focus Teams

Causes and Impacts of Engineering

Changes

October 14-15, 1998

Presented By:

Ted Hsu

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LEAN AEROSPACE

INITIATIVE

_{Presentation Outline}

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Motivation

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Key questions

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Research design

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LEAN AEROSPACE LEAN AEROSPACE INITIATIVE INITIATIVE

_Motivation

Program & the system being acquired Acquisition community User community

Prime contractor & its suppliers

Note: Diagram adopted from Ellis & Ludwig’s Systems Philosophy, & Blanchard’s System Engineering Management.

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Goal: Guidelines for

reducing defense

aerospace product cost &

development cycle time

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Literature: Engineering

Changes lead to increased

cost & cycle time

– How do these results apply in defense aerospace product development?

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Context: Defense

aerospace

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LEAN AEROSPACE

INITIATIVE

Class I Engineering Changes:

Development & Production Phases

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Impacts on product form, fit, or function

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Functionalities or physical config different before/after

engineering change

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Visible to all communities

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LEAN AEROSPACE

INITIATIVE

_{Key Questions}

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What are the major causes and impacts of

engineering changes?

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What are practices that would help reduce

undesirable engineering changes?

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What might the customer do to help reduce

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LEAN AEROSPACE

INITIATIVE

_{Research Design}

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Method

– Case studies focusing on 3 major defense aerospace programs

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Database

– Studied 118 engineering changes

– Engineering Change Proposal (ECP) contractor submittals – Program A: 60, Program B: 31, Program C: 27

– Each set comprehensive for each program until 11/17/1997 – Supporting documents & written background information

– Conducted formal & informal interviews

– Personnel interviewed – Government (24) – Contractors (29) – Purpose of interviews

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LEAN AEROSPACE

INITIATIVE

_{Overview of Case Studies}

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Program A - Major aircraft subsystems upgrade

– Modification program to integrate 4 electronics mission subsystems

– Single prime contractor

– No IPTs during development

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Program B - Major electronics subsystem upgrade

– Modification program - technology upgrade

– Somewhat dependent on Program A

– Two primes during development, customer as integrator

– No IPTs during development

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Program C - Major aircraft development & production program

– New program, single prime contractor

– Integrate Program A basic electronics mission subsystems into

aircraft

– Incorporate some newer technology

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LEAN AEROSPACE

INITIATIVE

Primary Causes of Engineering

Changes

• Comprehensive data set identified 3 dominant causes • Added two more based on data normalizations

19.5% 14.4% 18.6% 11.0% 7.6% 19.5% 9.3% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% Reqmts definition issues Changes in needs

Fix deficiencies Govt-prime interactn Program-to-program interactn Technology change Documentation changes Causes % of Engineering Changes

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LEAN AEROSPACE

INITIATIVE

Program Comparison: Primary

Causes of Engineering Changes

• Combinations of dominant causes are different across programs • Conventional wisdom would predict major program schedule delay

in Program C. Is the prediction correct?

25.0% 13.3% 26.7% 8.3% 1.7% 16.7% 8.3% 19.4% 3.2% 16.1% 22.6% 19.4% 12.9% 6.5% 7.4% 29.6% 3.7% 3.7% 7.4% 33.3% 14.8% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% Reqmts definition issues Changes in needs

Fix deficiencies Govt-prime

interactn Program-to-program interactn Technology change Documentation changes Causes % of Engi neering Changes Program A (60) Program B (31) Program C (27)

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LEAN AEROSPACE

INITIATIVE

_{Program A Dominant Causes}

_ Dominated by complex,

modified OTS system integration

_ Supplier of OTS system

involved in development early

_ Many redesigns on OTS

system

_ Recent producibility &

reliability problems

_ Other mission systems

evolved by introducing newer technology

Program Key Characteristics

Total Program A engineering changes: 60

25.0% 26.7% 16.7% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% Reqmts definition issues Fix deficiencies Technlgy change Causes % of Engineering Changes

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LEAN AEROSPACE

INITIATIVE

_{Program B Dominant Causes}

_ Subsystems suppliers

involved early in design

_ Two primes during

development

– Reqmts-related questions remained despite frequent contacts

– 2 engineering changes per ECP issue

_ Program baseline shifted due

to changes in Program A

Program Key Characteristics

Total Program B engineering changes: 31

19.4% 22.6% 19.4% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% Reqmts definition issues Govt-prime interactn Program-to-program interactns Causes % of Engineering Changes

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LEAN AEROSPACE

INITIATIVE

_{Program C Dominant Causes}

_ Program schedule a priority

_ Clarified reqmts early

_ Opportunities for fast customer

learning

– Accommodate newly definitized needs

– Add newer, low risk technology

_ Documentation changes mostly

due to program newness

29.6% 33.3% 14.8% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% Changes in needs Technlgy change Doc. changes Causes % of Engineering Changes

Program Key Characteristics

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LEAN AEROSPACE

INITIATIVE

_{Requirements Definition Issues}

25.0% 19.4% 7.4% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% A (60) B (31) C (27) Program

% of engineering changes

Use of IPTs helped clarify design assumptions/capabilities as much as possible early in Program C, thereby reducing

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LEAN AEROSPACE

INITIATIVE

_{Changes in Needs}

13.3% 3.2% 29.6% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% A (60) B (31) C (27) Program % of Engineering Changes

Due to few “Reqmts definition issues”, Program C quickly

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LEAN AEROSPACE

INITIATIVE

_{Technology Advances}

16.7% 12.9% 33.3% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% A (60) B (31) C (27) Program % of Engineering Changes

• Program C also had opportunity to quickly incorporate newer

technology

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LEAN AEROSPACE

INITIATIVE

Impacts of Engineering Changes

on Program Schedule

• Program C schedule priority ensured no program schedule delay • Programs A & B engrg change-related schedule delays due

primarily to “Reqmts definition issues” & “Fix deficiencies”

• Not all program schedule delays are due to engrg changes: other

18.3% 22.6% 0.0% 0.0% 5.0% 10.0% 15.0% 20.0% 25.0%

Program A (60) Program B (31) Program C (27)

E n g i n e e r i n g C h a n g e s l e a d i n g t o p r o g r a m s c h e d u l e d e l a y s

% of Enigneering

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Impacts of Engineering

Changes on Prime Contractors

45.0% 11.7% 6.5% 18.5% 77.8% 0.0% 43.3% 0.0% 48.4% 45.2% 0.0% 3.7% 0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

Rework New work Less work None

Impacts on prime contractor(s)

% of engineering changes

• Use of IPT helped prime of Program C clarify reqmts early, & have

less “Rework” than primes in Programs A & B

•Engineering changes infrequently provide relief from reqmts for

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Impacts of Engineering Changes

on Suppliers

66.7% 21.7% 36.7% 33.3% 8.3% 16.1% 35.5% _38.7% 9.7% 3.7% 25.9% 3.7% 0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

Rework New work Less work None

Impacts on suppliers

% of Engineering Changes

• Use of IPTs including key suppliers may have helped clarify key

suppliers’ capabilities to the primes early in Programs A & B, thereby avoiding some “Rework”

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Engineering Changes Resulting in

Unanticipated Engineering Changes

• Majority of engrg changes do not result in surprises to be dealt with

using additional engrg changes

• Impact of engineering changes well-understood on

change-by-change basis. 1.7% 0.0% 7.4% 0.0% 2.0% 4.0% 6.0% 8.0% 10.0%

Programs

% of Engineering

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LEAN AEROSPACE

INITIATIVE

Summary of Findings

l Five dominant causes of engineering changes identified

l Combination of dominant causes in each program driven by

characteristics & practices in each program

l Use of IPTs enabled reduction of engineering changes due primarily

to “Requirements definition issues”

l Lessons on supplier integration into product development

– Early involvement not always sufficient to reduce undesirable engrg changes

– Reduction of undesirable engrg changes requires understanding of key suppliers’ capabilities by primes, IPT environment would help

l Frequent changes in needs and insertion of newer technology can be

done without PD cycle time increases

l Few engineering changes provide relief from requirements for primes

& their suppliers