As discussed before, the primary risk to the project was schedule risk. Due to the generous funding from the project sponsors, the HE-RPA development team was able to acquire parts and labor required for development in order to reduce the total potential development time of the system. Further, spare parts were ordered where appropriate to avoid further delays should they become necessary.
As discussed in Chapter III, a survey of the HE-RPA development team members was taken to determine the expected duration of each task in the network diagram. The average of the responses for minimum, likely, and maximum duration in weeks are repeated below in Table 13 with the actual task completion time included as well.
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Table 13: Network Diagram Activities with Results
Many of the tasks took a lot longer to complete than expected, showing that the HE-RPA development team was either incredible unlucky or did not adequately
appreciate the level of schedule risk in the project.
Tasks F, G, I, and L took less time than the minimum expected amount of time to complete. Task F, build HE system, took less time according to the network diagram because it was being designed as the EM and ICE systems were being designed. This is more of an artifact of the network diagram and the definition of dependent and parallel tasks. The HE system could not be built without the ICE or EM system and many issues found while building the HE system would cause redesigns of the EM, ICE or both systems. The duration of task G, integrate AFIT 1, was just below the lower end of the projected duration. Once the airframes were delivered, Co-Operative Engineering Services Inc. (CESI) was able to get the system ready for taxi test as planned. The
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extensive experience of CESI in flying hobby aircraft assisted in keeping this task under schedule. Task I, taxi test AFIT 1, took a minimum amount of time because integration of AFIT 2 was being competed the morning of the taxi test, and the taxi test was
accomplished in one day. Task L, AFRL flight test approval, took a minimum amount of time; AFRL decided that AFRL flight test approval was not required since AFRL was not directly funding the flight test. The fact that this task could be accomplished in parallel with another task also assisted in keeping it off the critical path.
The duration of tasks C, E, M, N, and O fell within projected timeframe. The HE- RPA development team correctly predicted that task C, build airframes, would take longer than expected. Fortunately, the airframe that was delivered worked and was able to support the required test objectives. Task E, bench test ICE system, stayed within the expected range. Again, this is more of an artifact of the network diagram. Two ICE engines were damaged, one permanently, during bench testing resulting in a redesign of the ICE system. The redesign is captured in the ICE system build time and not in the ICE test time. Many hours were spent in the lab testing different configurations of the HE system with the ICE running to see if the ICE system would work while integrated as a part of the HE system as a whole.
Task M, bench test AFIT 2, did not take a long time. This was likely due in part to the learning curve. The bench testing of the integrated system was similar to the bench test of the HE system but it included the airframe and the propeller. Task N, taxi test
AFIT 2, also stayed within schedule. Having the prior experience of taxi testing AFIT 1
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objectives that were accomplished. Task O, flight test AFIT 2, also took as much time as expected. The motivation to complete the flight test prior to graduation assisted in making sure everything was ready to go for flight test pending acceptable flight weather. Task O remains partially completed since AFIT 2 crashed in flight test and never flew. It still remains to be seen if the HEPS can provide enough thrust to get AIFT 2 airborne. All HEPSs were functioning properly when the landing gear assembly broke and a wheel came off during takeoff.
Tasks A, B, D, H, J, and K took longer than the maximum expected amount of time to complete. Task A, build EM system and task B, build the ICE system were accomplished in parallel. Some delays that could be attributed to other tasks were included in the delay for tasks A and B since the network diagram is not set up
iteratively. Issues in later tasks that resulted in rework of earlier tasks are charged to the earlier task. It could be argued that some of the delays in tasks A and B are due to the heavier class schedule during this period but a lighter class schedule would not have shortened the fabrication time of many of the parts built during tasks A and B. In spite of a heavy class schedule, Ausserer [12] directed the interns in development of HE system components.
Task D, bench test EM system took one day longer to complete than the upper bound of the projected duration. This timeframe does not include much of the rework that was done during the EM system development. Task H, bench test HE system, was delayed and some of the delay could be attributed to the iterative behavior of testing, which is not captured by the diagram. Including the iterative nature of the project with the
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network diagram would not have sped up the project completion and would not have changed what appears on the critical path, it would have only changed the accounting of when tasks were completed.
Task J, integrate AFIT 2, took longer than expected due to the lack of
communication between team members and CLMax. Integration efforts were addressed at the onset of the project and an extra fuselage was shipped to ensure that the avionics would fit. The fuselage did not include the hinges or the other hardware required for integration, so the risk mitigation efforts were ineffective in reducing the amount of time required for system integration.
Task K, flight test AFIT 1, was also delayed. Flight test delays were anticipated due to the high level of coordination required between CESI support contractors, HE- RPA team members, Camp Atterbury scheduling, advisors, and weather. There was a delay in coordinating an acceptable flight test date for AFIT 1. Since AFIT 1 was not on the critical path, it did not delay the project. Ausserer, who was primarily working on the HEPS development, did not attend the AFIT 1 flight test and continued working on the HEPS development.
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Figure 42: HE-RPA network calculations
Figure 42 shows how long the project would take if the durations from the likely column in Table 13 were used, and is repeated from Chapter III for ease of reference. Figure 43 shows how long the project actually took by using the durations in the actual column from Table 13 to calculate the network duration as well as the start, finish, and slack times. The project lasted 56.6 weeks. Not one of the 100 trials in the Monte Carlo simulation took 56.6 weeks. The average pass through the Monte Carlo simulation took 38.2 weeks to accomplish with a standard deviation of 4.3 weeks. The actual project duration of 56.6 weeks is 4.3 standard deviations above the average.
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Figure 43: Actual Network Diagram
The average of the team members’ approximate minimum, likely, and maximum task durations were used to generate triangle distributions for each task in the network diagram. The triangle distribution was selected because it can compensate for a high level of uncertainty. If the team member minimum, likely, and maximum duration approximations were accurate, then it would be almost impossible for the project to take 56.6 weeks to accomplish. It is almost certain that the projections were not accurate and that the long schedule duration is due more to the team not understanding the entire schedule risk of each task. Prior experience levels of the team members could have been used to make adjustments to the task estimations Additionally, it would not be accurate to say that the team was delayed due to bad weather on account of the unseasonably warm weather experienced over the fall and winter of 2011-2012. Given the lack of experience of the team on similar projects, the inaccuracies of the schedule predictions are less surprising
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