Transcript Whole Engine Cost Modelling and Use of a Comparator Tool

How
Big is Yours?
The use of Comparator tools in Estimation
Andy Nolan BSc Hons, CEng, FBCS, CITP
Chief of Software improvement – The Software Centre of Excellence
Satpaul Sall BSc Hons
Software Technologist – The Software Centre of Excellence
©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose
other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given
concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of
its subsidiary or associated companies.
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Rolls-Royce data
A Brief History of Engine Controls
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 The Control Systems department
is responsible for the Engine
Electronic Controllers (EECs) for a
range of small and large gas
turbine engines for the aerospace
industry.
 The software is developed to DO178B Level-A standards
 The company has been developing
high integrity software for over 20
years and has extensive data on
its processes and productivity.
 We have the largest order book in
history, new engine development
places greater demand on the
software team (shorter time scales
and lower costs)
Rolls-Royce data
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Benchmarking
the business
CO-Bus-MO
Enterprise
business
performance
CO-RISK-MO
Risk
Management
Using the model
to identify and
quantify
risk
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CO-Imp-MO
Improvement
COCOMO
Estimation &
eliciting key
assumptions &
negotiation
Software
Supplier
COCOMO
COCOMO
Hardware
COCOMO
A unifying
language
Using COCOMO
to identify &
validate
improvements
Challenging
our supplier
costs.
Hardware
Supplier
COCOMO
Using many SW
factors to
estimate
hardware
engineering
The Comparator Tool
©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose
other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given
concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of
its subsidiary or associated companies.
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Assumption
The engineering practice of
translating requirements into a
implementation will be “similar” in
many engineering domains and will
be subject to the same cost drives
as software
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Environment
Cost = C * Size * Environment
Higher
Cost
Lower
Cost
Size
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Size (the product): The
magnitude (or quantity) of a
task.
• Size
• Complexity
• Reuse
• Risk/Uncertainty
Environment: The
environment in which you
build the product
• Processes & tools
• People
• Management
• Organisation
• Etc
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Comparator Tool
New Project
Historic Baseline
Historic Size
Historic
Environment
(a definition of the
project
environment)
Actual historic cost
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Delta
Create a
scaling Factor
that represents
the differences
between the
two projects in
both size and
environment
New Size
New
Environment
(a definition of the
project
environment)
New cost = Historic
cost * Delta
Examples
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Absolute Tool
An “Absolute” estimation
tool was developed for
Hardware by relating
hardware complexity to
software lines of code.
This relationship is hidden
from the estimator who
only has to select
hardware units they are
working on
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New Project
Standard job hours
Size
(task and unit)
Environment
(a definition of the
project
environment)
cost = Standard Job
* Size *
Environment
Calibrating a Whole Engine
R&D Cost Model
©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose
other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given
concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of
its subsidiary or associated companies.
Abstract
 Business Challenge

Can we use COCOMO to estimate the cost of a whole engine?
 Effort

We have 8 hours to demonstrate this capability!
 Approach
Use Comparator method based on COCOMO II
 Relate all aspects to a nominal “Baseline” project
 COCOMO II factors to be completed by Chief Design Engineer
 No underlying factors to be altered – only the constant “C”
 Leave 1 project aside as a test of calibration (project 6)

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Environment: Relative (COCOMO II factors)
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Engine 1 Engine 2 Engine 3 Engine 4 Engine 5 Engine 6
The only show in
town – high
priority. Single
site project, stable
team
High requirements
volatility, low
TRL, low process
maturity, low team
experience, low
management
experience and
high schedule
pressure
Rolls-Royce data
Stable
requirements,
higher precedence,
team more
experienced, single
site team,
improved process
maturity., high
levels of reuse
High Schedule
pressure
Stable
requirements,
higher precedence,
single site team,
improved process
maturity. Improved
management
Some architectural
issues. Drop in
team experience,
high turnover of
staff, multi site
working
High process
maturity,
Requirements
change, loss of
precedence,
inexperienced
team, architectural
issues, loss of team
cohesion, schedule
pressure, new
management team,
multi site project,
staff turnover
Lower
requirements
change, team
cohesion, process
maturity,
experienced team
Loss of
precedence, some
architectural
issues, schedule
pressure, multi site
project, high staff
turnover
Low requirements
volatility, high
team cohesion,
high precedence,
mature processes,
experienced team,
low schedule
pressure,
experienced
management team
What correlated well
 Size
 REVL
 PREC
 FLEX
 RESL
 TEAM
 PMAT
 SCED
 Management
Expereince
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 Based on the
survey, these
factors correlated
well with cost.
This does not
mean the other
factors do not –
rather it means
that these were the
factors the
interviewee
understood well.
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Predicted & Actual costs – A close correlation
Calibrate to
these
projects
Baseline
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Estimate
this project
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Cost = C * Size * Environment
(not to scale)
Environment
1
4
2
5
B
6
3
Size (AMF) – not to scale
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Conclusions
 Size is not the only determining
factor for cost – the environment
is also proving critical for project
success.
 From a simple analysis, it would
seem that COCOMO II can be
used to “model” the development
environment
 The Rolls-Royce Environment is
changing and COCOMO II
predicts that this is creating a
headwind
 The exercise has the side effect
of training the business leaders in
the factors that affect cost
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Why Estimation Tools Help
the Business
©2011 Rolls-Royce plc
The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose
other than that for which it is supplied without the express written consent of Rolls-Royce plc.
This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given
concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of
its subsidiary or associated companies.
COCOMO II: A common Language
COCOMO II is a language
that bridges between
engineering and the
business
It is also the bridge between
different areas of the
business
It has been used to help
benchmark the business
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Remain within a domain
 You can interpolate and
extrapolate within a domain
but not across domains
(unless you have a domain
bridge function)
COCOMO II appears to work
on engineering practices
where requirements are
translated into implementation
through an engineering
process
Rolls-Royce data
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