CASe exAMPle: geneRAl AvIATIOn hAngAR
ReSTORATIOn
I n t ro d u c t i o n
this case example, although for a very small project, illustrates some interesting features of
planning using critical path analysis. although there are only 17 activities, the precedence
logic is a little complex to draw clearly owing to the number of crossed links, and we
show how this difficulty is easily overcome by inserting dummy activities at three of the
crossover points.
our case example demonstrates the application of pert (program evaluation and
review technique), in which the estimated duration for each activity can be subjected
to a probabilistic study in an attempt to forecast the most likely completion time for the
entire project.
finally, this case will demonstrate how a project manager need not accept the results of
time analysis without question, but can plan to apply extra effort to expedite critical activities
(usually for additional cost) to bring the planned project completion date forward
P ro j e c t B a c k g ro u n d
CEN-CONSTRUCT is a medium-sized business located in Sydney, Australia that is
owned and operated by a family. It is principally a consulting company that specializes in
aviation civil engineering, having worked on runway construction and paving projects as
well as several other airport airside projects, most of which have been for smaller general
airports. Having decided to extend its range of operations, the company recognized a local
need for a contractor that could carry out aircraft hangar renovation. In consequence, the
company has now achieved a good level of expertise in the interior design and renovation
of hangars
the subject of this case example was the renovation of a hangar for a small client at a
general aviation airport. the client uses the hangar to house his cessna 310 twin-engine
plane. the hangar was originally built in 1950, since when no further construction or
renovation work has been carried out. cen-construct had no previous integrated
project management system or strategy for this type of project, so the project management
planning steps described here were implemented for them. the planning exhibits are
slightly simplified for clarity of reproduction.
P ro j e c t D e f i n i t i o n A n d A c t i v i t y L i s t
Because the total number of identified activities was small, a simple activity list (task
list) sufficed for the WBS. This list, given in Figure 7.11, defines the project scope. It also
defines the logical work sequence by stating the immediate predecessor(s) that must be
completed before each new activity can begin. the cost estimates show that the total
original estimated cost for this project was $46 900.
Readers will note that the table in Figure 7.11 contains four different duration estimates
for each activity. this is because the project planner decided to use a probability assessment
method known as pert to this project. this is explained in the .
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CASeexAMPlegeneRAlAvIATIOnhAngARReSTORATIOnI n t r.docx
1. CASe exAMPle: geneRAl AvIATIOn hAngAR
ReSTORATIOn
I n t ro d u c t i o n
this case example, although for a very small project, illustrates
some interesting features of
planning using critical path analysis. although there are only 17
activities, the precedence
logic is a little complex to draw clearly owing to the number of
crossed links, and we
show how this difficulty is easily overcome by inserting dummy
activities at three of the
crossover points.
our case example demonstrates the application of pert (program
evaluation and
review technique), in which the estimated duration for each
activity can be subjected
to a probabilistic study in an attempt to forecast the most likely
completion time for the
entire project.
finally, this case will demonstrate how a project manager need
not accept the results of
time analysis without question, but can plan to apply extra
effort to expedite critical activities
(usually for additional cost) to bring the planned project
completion date forward
P ro j e c t B a c k g ro u n d
2. CEN-CONSTRUCT is a medium-sized business located in
Sydney, Australia that is
owned and operated by a family. It is principally a consulting
company that specializes in
aviation civil engineering, having worked on runway
construction and paving projects as
well as several other airport airside projects, most of which
have been for smaller general
airports. Having decided to extend its range of operations, the
company recognized a local
need for a contractor that could carry out aircraft hangar
renovation. In consequence, the
company has now achieved a good level of expertise in the
interior design and renovation
of hangars
the subject of this case example was the renovation of a hangar
for a small client at a
general aviation airport. the client uses the hangar to house his
cessna 310 twin-engine
plane. the hangar was originally built in 1950, since when no
further construction or
renovation work has been carried out. cen-construct had no
previous integrated
project management system or strategy for this type of project,
so the project management
planning steps described here were implemented for them. the
planning exhibits are
slightly simplified for clarity of reproduction.
P ro j e c t D e f i n i t i o n A n d A c t i v i t y L i s t
Because the total number of identified activities was small, a
simple activity list (task
list) sufficed for the WBS. This list, given in Figure 7.11,
defines the project scope. It also
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A p p l i c a t i o n O f P E RT To T h e H a n g a r R e n o v
a t i o n P ro j e c t
Almost all duration estimates are a matter for subjective
judgement and the actual outcome
for each activity can be quite different from the planner’s
intention. One branch of critical
path analysis recognizes this uncertainty. The method, one of
the earliest critical path
analysis methods, is program evaluation and review technique
(pert). each person who
estimates the duration of an activity is asked to give three
possible values which are:
tm = the most likely estimated time
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T h e N e t w o r k D i a g r a m A n d I t s I n i t i a l Ti m e
A n a l y s i s
the network diagram, using expected duration values, is shown
in figure 7.12. time
analysis has revealed the critical path (shown in bold lines) and
indicates a most probable
7. project duration of 67.9 days.
Two dummy activities, identified as A and B, have been
inserted to clarify the logic
drawing. These dummy activities do not affect the network logic
(work sequence) and as
they both have zero duration they do not affect time analysis. It
is quite usual to add a start
dummy and a finish dummy to network diagrams that otherwise
would have multiple starts
and finishes, but their use within a precedence network, as here,
is less common. However, a
glance at figure 7.13 shows that they can improve the clarity of
a network diagram.
M e a s u re s F o r R e d u c i n g T h e P re d i c t e d Ti m
e s c a l e
It often happens that the predicted timescale for a project is too
long, and that was the case
in this example, with the client specifying that he wanted to fly
in and house his airplane
between days 50 and 55 of this project. clearly the originally
planned completion time
of day 68 would have been far too late. there are two possible
approaches to shortening
the planned timescale of a project. the project manager has a
choice between these two
methods or, to achieve maximum expedition, can use both
methods together.
Fast-tracking using concurrency Network logic often shows
constraints that are not literally
true, and it is known that some activities can be allowed to
overlap or even run concurrently.
one example is in the purchase of long-lead items, where design
8. engineers are able to release
purchasing information to the buyer before the relevant design
activity has been completed.
the complex constraints given in figure 7.10 showed how the
precedence system will
allow such overlaps to be depicted in a network. However, that
process was not considered
applicable on this aircraft hangar case project and will not be
described further here.
Shortening activity durations by crash action It is often possible
to shorten the duration
of an activity by deploying more resources, using different
processes, or working overtime.
these actions usually add additional cost, and it would thus be
wasteful to crash activities with
large amounts of slack because, to do so, would have no effect
on the total project duration.
Crash action must be considered first, therefore, only on
activities which lie on the
critical path. constructing a table that compares time saved on
an activity with the relevant
additional cost can theoretically produce a factor for each
activity that will reveal the cost
per day saved for that activity.
thus crash action can be even more selective than choosing only
critical activities,
because it can be concentrated on those critical activities which
have the lowest cost per day
saved. However, the exercise becomes complicated in practice
because as one or two critical
activities are crashed and the critical path is shortened, other
paths through the network
become critical. Crash attention must then shift to the newly
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.
Figure 7.13 use of dummy activities in precedence
networks to clarify
multiple links
Install toilet and shower
Figure 7.14 Activity list for the aircraft hangar
renovation project showing
crashed times and extracosts
a v i a t i o n p r o j e c t m a n a g e m e n t� � �
Flouris, T. G., & Lock, D. (2008). Aviation project
management. Retrieved from http://ebookcentral.proquest.com
Created from erau on 2018-09-26 17:31:09.
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15. there is no slack in a totally crashed network, so that all or most
activities are critical and
that increases the risk of failing to meet the delivery date.
further, the probability results
from the original pert time analysis no longer apply, because
each crashed estimate has
been made on a deterministic, not probabilistic basis.
In the aircraft hangar renovation project a realistic approach to
crash action produced
the table shown in Figure 7.14 on the left. When the crashed
times were substituted for the
pert normal duration estimates in the network diagram they
produced a total estimated
project time of 43 days, well within the client’s requirements.
the notes in figure 7.14 show that some activities were less
costly to crash than others
in terms of the dollars budgeted for each day’s time saved.
note that although activity 10 could have been shortened from
5.2 to 3 days, the
additional expenditure of crashing that task was not justified
because Activity 11, running
concurrently, could not be crashed below 6 days. in other
words, activity 10 still had slack
remaining after Activity 11 had been crashed, and there is no
point in wasting money on
crashing non-critical activities, because that process cannot
reduce the project duration.
Summarizing, therefore, the hangar restoration project duration
was originally planned
as 67.9 days at a budget cost of $46 900. crash actions brought
the planned duration down
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.
General Aviation Hangar Renovation Group Case Study
Assuming the perspective of your role (Project Manager),
consider how you would address the following case study
questions:
1. What are the key issues surrounding this case?
2. What is the nature of the problems that exist?
3. Identify opportunities that may be involved.
4. In what ways were problems resolved or leveraged?
5. Recommend and justify additional courses of action that are
most likely to be effective.
Student 1 – Project ManagerJob Responsibilities: Accomplishes
project objectives by planning and evaluating project activities..
After reading the case study in the PDF file attached separately,
answer the 5 questions above from a Project Manager
perspective. DON'T JUST GIVE GENERAL ANSWERS TO
THE QUESTIONS. IT HAS TO BE FROM A project manager
POINT OF VIEW. YOUR PERSONAL OPINION AS PROJECT
MANAGER.
DON't list references or citations, as this is supposed to be your
own personal opinion from a project Manager point of view.
AT LEAST 50 Words for each answer.
Copy the questions, then put the answers below each question,
in a Q&A format.
General Aviation Hangar Renovation Group Case
18. Stud
y
Assum
ing the perspective of your role
(
Project Manager
)
,
consider how
you would address the following case study questions:
1.
What are the key issues surrounding this case?
2.
What is the nature of the problems that exist?
3.
Identify opportunities that may be involved.
4.
In what ways were problems resolved or leveraged?
5.
Recommend and justify additional courses of action that are
most likely to
be effective.
Student 1
–
19. Project
Manager
Job Responsibilities: Accomplishes project objectives by
planning and evaluating
project activities
.
.
After reading the case study in the PDF file attached
separately, answ
er the 5 questions above from
a
Project Manager
perspective
.
DON'T JUST GIVE GENERAL ANSWERS TO THE
QUESTIONS. IT HAS TO BE FROM
A project manager
POINT OF
VIEW. YOUR
PERSONAL OPINION
AS
PROJECT MANAGER
.
DON't
list references or citations, as this is supposed to be
your own pe
rsonal
opinion from a project
20. Manager
point of
view.
AT LEAST
50 Words for each answer.
Copy the questions, then put the answer
s
below
each question,
in a Q&A format.
General Aviation Hangar Renovation Group Case
Study
Assuming the perspective of your role (Project Manager),
consider how
you would address the following case study questions:
1. What are the key issues surrounding this case?
2. What is the nature of the problems that exist?
3. Identify opportunities that may be involved.
4. In what ways were problems resolved or leveraged?
5. Recommend and justify additional courses of action that are
most likely to
be effective.
Student 1 – Project Manager
Job Responsibilities: Accomplishes project objectives by
planning and evaluating
project activities..
After reading the case study in the PDF file attached
separately, answer the 5 questions above from a Project
21. Manager
perspective. DON'T JUST GIVE GENERAL ANSWERS TO
THE
QUESTIONS. IT HAS TO BE FROM A project manager POINT
OF
VIEW. YOUR PERSONAL OPINION AS PROJECT
MANAGER.
DON't list references or citations, as this is supposed to be
your own personal opinion from a project Manager point of
view.
AT LEAST 50 Words for each answer.
Copy the questions, then put the answers
below each question, in a Q&A format.
